1
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Krivdin LB. Recent advances in the liquid-phase 6,7 Li nuclear magnetic resonance. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2023; 61:138-161. [PMID: 36330776 DOI: 10.1002/mrc.5323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 11/01/2022] [Accepted: 11/01/2022] [Indexed: 06/16/2023]
Abstract
The present review is focused on experimental methods and structural applications, including computational aspects, of classical lithium liquid-phase nuclear magnetic resonance (NMR). It consists of four parts covering accordingly a brief overview, early experimental reports (papers of up to about 2015) and more recent (papers appearing in the interim of about 2015 until 2022) results, together with very few but highly prospective computational results.
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Affiliation(s)
- Leonid B Krivdin
- A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
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2
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Masiuk US, Faletrov YV, Kananovich DG, Mineyeva IV. Stereodivergent Assembly of 2,6- cis- and - trans-Tetrahydropyrans via Base-Mediated Oxa-Michael Cyclization: The Key Role of the TMEDA Additive. J Org Chem 2023; 88:355-370. [PMID: 36495268 DOI: 10.1021/acs.joc.2c02382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The stereodivergent synthesis of cis- and trans-2,6-disubstituted tetrahydropyrans (THPs) via sodium hexamethyldisilazide-promoted oxa-Michael cyclization of (E)-ζ-hydroxy α,β-unsaturated esters is presented. The cyclization affords the kinetically favored trans-THPs with high stereoselectivity (dr up to 93:7) at a low temperature (-78 °C), while the room-temperature reaction does not produce the thermodynamically preferred cis-THPs as major products and occurs with poor stereocontrol. The addition of tetramethylethylenediamine (TMEDA) significantly improves the stereochemical outcome of the room-temperature cyclization and allows attaining high cis-selectivity (dr up to 99:1). The remarkable effect of TMEDA indicates that the sodium cation plays an important role in controlling the stereoselectivity of the thermodynamically driven process, that is, complexation of the cation with the cyclization products results in diminished selectivity. DFT calculations support this conclusion, indicating a greater difference in Gibbs energies of sodium-free cis- and trans-enolates compared to the respective sodium chelate complexes. The synthetic utility of the method has been demonstrated by the formal syntheses of (+)-Neopeltolide and (-)-Diospongin B and the total synthesis of (-)-Diospongin A.
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Affiliation(s)
- Uladzimir S Masiuk
- Department of Chemistry, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus.,School of Science, Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Yaroslav V Faletrov
- Department of Chemistry, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus.,Research Institute for Physical Chemical Problems, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus
| | - Dzmitry G Kananovich
- School of Science, Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Iryna V Mineyeva
- Department of Chemistry, Belarusian State University, Leningradskaya 14, 220006 Minsk, Belarus
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3
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Lui NM, MacMillan SN, Collum DB. Lithiated Oppolzer Enolates: Solution Structures, Mechanism of Alkylation, and Origin of Stereoselectivity. J Am Chem Soc 2022; 144:23379-23395. [PMID: 36534055 PMCID: PMC10071589 DOI: 10.1021/jacs.2c09341] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Camphorsultam-based lithium enolates referred to colloquially as Oppolzer enolates are examined spectroscopically, crystallographically, kinetically, and computationally to ascertain the mechanism of alkylation and the origin of the stereoselectivity. Solvent- and substrate-dependent structures include tetramers for alkyl-substituted enolates in toluene, unsymmetric dimers for aryl-substituted enolates in toluene, substrate-independent symmetric dimers in THF and THF/toluene mixtures, HMPA-bridged trisolvated dimers at low HMPA concentrations, and disolvated monomers for the aryl-substituted enolates at elevated HMPA concentrations. Extensive analyses of the stereochemistry of aggregation are included. Rate studies for reaction with allyl bromide implicate an HMPA-solvated ion pair with a +Li(HMPA)4 counterion. Dependencies on toluene and THF are attributed to exclusively secondary-shell (medium) effects. Aided by density functional theory (DFT) computations, a stereochemical model is presented in which neither chelates nor the lithium gegenion serves roles. The stereoselectivity stems from the chirality within the sultam ring and not the camphor skeletal core.
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Affiliation(s)
- Nathan M Lui
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
| | - David B Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
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4
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Abstract
The asymmetric alkylation of enolates is a particularly versatile method for the construction of α-stereogenic carbonyl motifs, which are ubiquitous in synthetic chemistry. Over the past several decades, the focus has shifted to the development of new catalytic methods that depart from classical stoichiometric stereoinduction strategies (e.g., chiral auxiliaries, chiral alkali metal amide bases, chiral electrophiles, etc.). In this way, the enantioselective alkylation of prochiral enolates greatly improves the step- and redox-economy of this process, in addition to enhancing the scope and selectivity of these reactions. In this review, we summarize the origin and advancement of catalytic enantioselective enolate alkylation methods, with a directed emphasis on the union of prochiral nucleophiles with carbon-centered electrophiles for the construction of α-stereogenic carbonyl derivatives. Hence, the transformative developments for each distinct class of nucleophile (e.g., ketone enolates, ester enolates, amide enolates, etc.) are presented in a modular format to highlight the state-of-the-art methods and current limitations in each area.
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Affiliation(s)
- Timothy B Wright
- Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada
| | - P Andrew Evans
- Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.,Xiangya School of Pharmaceutical Sciences, Central South University, Changsha 410013, Hunan, P. R. of China
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5
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Łowicki D, Watral J, Jelecki M, Bohusz W, Kwit M. Stereoselective protonation of 2-methyl-1-tetralone lithium enolate catalyzed by salan-type diamines. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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6
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Pang H, Williard PG. Solid state aldol reactions of solvated and unsolvated lithium pinacolone enolate aggregates. Tetrahedron 2020. [DOI: 10.1016/j.tet.2019.130913] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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7
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Zhou Y, Keresztes I, MacMillan SN, Collum DB. Disodium Salts of Pseudoephedrine-Derived Myers Enolates: Stereoselectivity and Mechanism of Alkylation. J Am Chem Soc 2019; 141:16865-16876. [PMID: 31613094 DOI: 10.1021/jacs.9b08176] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Pseudoephedrine-derived dianionic Myers enolates were generated using sodium diisopropylamide (NaDA) in THF solution. The reactivities and selectivities of the disodium salts largely mirror those of the dilithium salts but without the requisite large excesses of inorganic salts (LiCl) or mandated dilute solutions. The disodium salts require careful control of temperature to preclude deleterious aggregate aging effects traced to changes in the aggregate structure and intervening O-alkylations. Structural studies and density functional theory (DFT) computations show a dominant highly symmetric polyhedron quite different from the lithium analogue. No enolate-NaDA mixed aggregates are observed with excess NaDA. Rate studies show an alkylation mechanism involving an intervening tetramer-monomer pre-equilibrium followed by rate-limiting alkylation of tetrasolvated monomers. DFT computations were conducted to explore the possible influences on stereochemistry. A crystal deriving from samples aged at ambient temperature contains six dianionic subunits and two monoanionic (alkoxide-only) subunits. A new preparation of concentrated solutions of NaDA in THF solution is described.
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Affiliation(s)
- Yuhui Zhou
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
| | - David B Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory , Cornell University , Ithaca , New York 14853-1301 , United States
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8
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Zhang Z, Collum DB. Structures and Reactivities of Sodiated Evans Enolates: Role of Solvation and Mixed Aggregation on the Stereochemistry and Mechanism of Alkylations. J Am Chem Soc 2019; 141:388-401. [PMID: 30462500 PMCID: PMC7185956 DOI: 10.1021/jacs.8b10364] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Oxazolidinone-based sodiated enolates (Evans enolates) were generated using sodium diisopropylamide (NaDA) or sodium hexamethyldisilazide (NaHMDS) in the presence of N,N,N',N'-tetramethylethylenediamine (TMEDA), ( R,R)- trans- N,N,N',N'-tetramethylcyclohexanediamine [( R,R)-TMCDA], or ( S,S)-TMCDA. 13C NMR spectroscopic analysis in conjunction with the method of continuous variations (MCV), x-ray crystallography, and density functional theory (DFT) computations revealed the enolates to be octahedral bis-diamine-chelated monomers. Rate and computational studies of an alkylation with allyl bromide implicate a bis-diamine-chelated-monomer-based transition structure. The sodiated Evans enolates form mixed dimers with NaHMDS, NaDA, or sodium 2,6-di- tert-butylphenolate, the reactivities of which are examined. Stereoselective quaternizations, aldol additions, and azaaldol additions are described.
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Affiliation(s)
- Zirong Zhang
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
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9
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Jermaks J, Tallmadge EH, Keresztes I, Collum DB. Lithium Amino Alkoxide-Evans Enolate Mixed Aggregates: Aldol Addition with Matched and Mismatched Stereocontrol. J Am Chem Soc 2018; 140:3077-3090. [PMID: 29457718 PMCID: PMC6059615 DOI: 10.1021/jacs.7b13776] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Building on structural and mechanistic studies of lithiated enolates derived from acylated oxazolidinones (Evans enolates) and chiral lithiated amino alkoxides, we found that amino alkoxides amplify the enantioselectivity of aldol additions. The pairing of enantiomeric series affords matched and mismatched stereoselectivities. The structures of mixed tetramers showing 2:2 and 3:1 (alkoxide-rich) stoichiometries are determined spectroscopically. Rate and computational studies provide a viable mechanistic and stereochemical model based on the direct reaction of the 3:1 mixed tetramers, but they raise unanswered questions for the 2:2 mixed aggregates.
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Affiliation(s)
- Janis Jermaks
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Evan H. Tallmadge
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
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10
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Zhang X, Tutkowski B, Oliver A, Helquist P, Wiest O. Mechanistic Study of the Nickel-Catalyzed α,β-Coupling of Saturated Ketones. ACS Catal 2018. [DOI: 10.1021/acscatal.7b04105] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xin Zhang
- Laboratory
of Computational Chemistry and Drug Design, Laboratory of Chemical
Genomics, Peking University Shenzhen Graduate School, Shenzhen 518055, People’s Republic of China
| | - Brandon Tutkowski
- Department
of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
| | - Allen Oliver
- Department
of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
| | - Paul Helquist
- Department
of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
| | - Olaf Wiest
- Department
of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
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11
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Fox T, Günther H. NMR spectroscopy of organolithium compounds, part XXXIII: trans
-2,3-dimethylcyclopropyllithium aggregation in diethylether: An equilibrium between three different complexes of comparable energy and the influence of LiBr on aggregate structure. J PHYS ORG CHEM 2018. [DOI: 10.1002/poc.3800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Thomas Fox
- University of Zürich; Institute of Chemistry; Zürich Switzerland
| | - Harald Günther
- University of Siegen; Chemistry Department; Siegen Germany
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12
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Jagtap PR, Císařová I, Jahn U. Bioinspired total synthesis of tetrahydrofuran lignans by tandem nucleophilic addition/redox isomerization/oxidative coupling and cycloetherification reactions as key steps. Org Biomol Chem 2018; 16:750-755. [DOI: 10.1039/c7ob02848b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Three steps suffice to complete a bioinspired total synthesis of tetrahydrofuran lignans using tandem addition/isomerization/dimerization and cycloetherification reactions.
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Affiliation(s)
- Pratap R. Jagtap
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences
- 166 10 Prague
- Czech Republic
| | - Ivana Císařová
- Department of Inorganic Chemistry
- Charles University in Prague
- 12843 Prague 2
- Czech Republic
| | - Ullrich Jahn
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences
- 166 10 Prague
- Czech Republic
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13
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Mack KA, McClory A, Zhang H, Gosselin F, Collum DB. Lithium Hexamethyldisilazide-Mediated Enolization of Highly Substituted Aryl Ketones: Structural and Mechanistic Basis of the E/Z Selectivities. J Am Chem Soc 2017; 139:12182-12189. [PMID: 28786667 PMCID: PMC6122874 DOI: 10.1021/jacs.7b05057] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Enolizations of highly substituted acyclic ketones used in the syntheses of tetrasubstituted olefin-based anticancer agents are described. Lithium hexamethyldisilazide (LiHMDS)-mediated enolizations are moderately Z-selective in neat tetrahydrofuran (THF) and E-selective in 2.0 M THF/hexane. The results of NMR spectroscopy show the resulting enolates to be statistically distributed ensembles of E,E-, E,Z-, and Z,Z-enolate dimers with subunits that reflect the selectivities. The results of rate studies trace the preference for E and Z isomers to tetrasolvated- and pentasolvated-monomer-based transition structures, respectively. Enolization using LiHMDS in N,N-dimethylethylamine or triethylamine in toluene affords a 65:1 mixture of LiHMDS-lithium enolate mixed dimers containing E and Z isomers, respectively. Spectroscopic studies show that condition-dependent complexation of ketone to LiHMDS occurs in trialkylamine/toluene. Rate data attribute the high selectivity exclusively to monosolvated-dimer-based transition structures.
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Affiliation(s)
- Kyle A. Mack
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Andrew McClory
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Haiming* Zhang
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - Francis Gosselin
- Small Molecule Process Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States
| | - David B. Collum
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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14
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Cano R, Zakarian A, McGlacken GP. Direct Asymmetric Alkylation of Ketones: Still Unconquered. Angew Chem Int Ed Engl 2017; 56:9278-9290. [PMID: 28497890 DOI: 10.1002/anie.201703079] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 04/27/2017] [Indexed: 01/07/2023]
Abstract
The alkylation of ketones is taught at basic undergraduate level. In many cases this transformation leads to the formation of a new stereogenic center. However, the apparent simplicity of the transformation is belied by a number of problems. So much so, that a general method for the direct asymmetric alkylation of ketones remains an unmet target. Despite the advancement of organocatalysis and transition-metal catalysis, neither field has provided an adequate solution. Indeed, even use of an efficient and general stoichiometric chiral reagent has yet to be reported. Herein we describe the state-of-the-art in terms of direct alkylation reactions of some carbonyl groups. We outline the limited progress that has been made with ketones, and potential routes towards ultimately achieving a widely applicable methodology for the asymmetric alkylation of ketones.
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Affiliation(s)
- Rafael Cano
- Department of Chemistry, University College Cork, Cork, Ireland.,Analytical and Biological Chemistry Research Facility, University College Cork, Cork, Ireland
| | - Armen Zakarian
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, 93106, USA
| | - Gerard P McGlacken
- Department of Chemistry, University College Cork, Cork, Ireland.,Analytical and Biological Chemistry Research Facility, University College Cork, Cork, Ireland
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15
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Cano R, Zakarian A, McGlacken GP. Direkte asymmetrische Alkylierung von Ketonen: noch immer ein unerreichtes Ziel. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201703079] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Rafael Cano
- Department of Chemistry; University College Cork; Cork Irland
- Analytical and Biological Chemistry Research Facility; University College Cork; Cork Irland
| | - Armen Zakarian
- Department of Chemistry and Biochemistry; University of California; Santa Barbara CA 93106 USA
| | - Gerard P. McGlacken
- Department of Chemistry; University College Cork; Cork Irland
- Analytical and Biological Chemistry Research Facility; University College Cork; Cork Irland
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16
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Gair JJ, Haines BE, Filatov AS, Musaev DG, Lewis JC. Mono- N-protected amino acid ligands stabilize dimeric palladium(ii) complexes of importance to C-H functionalization. Chem Sci 2017; 8:5746-5756. [PMID: 29619194 PMCID: PMC5859881 DOI: 10.1039/c7sc01674c] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 06/15/2017] [Indexed: 11/21/2022] Open
Abstract
C–H activation, C–H functionalization, cyclopalladation, mono-protected amino acid, dimeric Pd amino acid complexes, MPAA coordination, relay of stereochemistry.
Mono-protected amino acid (MPAA) ligands are used in a number of Pd-catalyzed C–H functionalization reactions. MPAAs have been proposed to bind to Pd(ii) via κ2-(N,O) coordination, but such binding has not yet been experimentally validated. Herein, we report the synthesis and detailed characterization of a series of MPAA complexes prepared via cyclopalladation of dimethylbenzylamine in the presence of MPAAs. The isolated complexes exist as μ-carboxylato (MPAA) bridged dimers and feature potential M–M cooperativity and secondary sphere hydrogen bonding. Selective MPAA coordination and relay of stereochemistry, previously suggested to uniquely result from κ2-(N,O) MPAA coordination, are both observed. The isolated MPAA complexes undergo C–C and C–X (X = Cl, Br, I) bond formation when treated with electrophiles used for catalytic C–H functionalization. Stoichiometric iodination of MPAA palladacycles was found to proceed via a dinuclear palladium species with one equivalent of iodine in the rate limiting transition structure, and the isolated complexes also served as viable precatalysts for catalytic C–H functionalization. Together, these results provide a number of insights into the reactivity of Pd-MPAA complexes relevant to C–H bond functionalization.
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Affiliation(s)
- Joseph J Gair
- Department of Chemistry , The University of Chicago , Chicago , Illinois 60637 , USA .
| | - Brandon E Haines
- Cherry L. Emerson Center for Scientific Computation , Emory University , 1515 Dickey Drive , Atlanta , Georgia 30322 , USA .
| | - Alexander S Filatov
- Department of Chemistry , The University of Chicago , Chicago , Illinois 60637 , USA .
| | - Djamaladdin G Musaev
- Cherry L. Emerson Center for Scientific Computation , Emory University , 1515 Dickey Drive , Atlanta , Georgia 30322 , USA .
| | - Jared C Lewis
- Department of Chemistry , The University of Chicago , Chicago , Illinois 60637 , USA .
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17
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Abstract
The solution structures, stabilities, physical properties, and reactivities of sodium diisopropylamide (NaDA) in a variety of coordinating solvents are described. NaDA is stable for months as a solid or as a 1.0 M solution in N,N-dimethylethylamine (DMEA) at -20 °C. A combination of NMR spectroscopic and computational studies show that NaDA is a disolvated symmetric dimer in DMEA, N,N-dimethyl-n-butylamine, and N-methylpyrrolidine. Tetrahydrofuran (THF) readily displaces DMEA, affording a tetrasolvated cyclic dimer at all THF concentrations. Dimethoxyethane (DME) and N,N,N',N'-tetramethylethylenediamine quantitatively displace DMEA, affording doubly chelated symmetric dimers. The trifunctional ligands N,N,N',N″,N″-pentamethyldiethylenetriamine and diglyme bind the dimer as bidentate rather than tridentate ligands. Relative rates of solvent decompositions are reported, and rate studies for the decomposition of THF and DME are consistent with monomer-based mechanisms.
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Affiliation(s)
- Russell F. Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, United States,
| | - Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, United States,
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301, United States,
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18
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Guang J, Liu Q, Hopson R, Kagan G, Li W, Monroe TB, Williard PG. Conformational Polymorphism of Lithium Pinacolone Enolate. J Am Chem Soc 2016; 138:15177-15188. [PMID: 27762552 DOI: 10.1021/jacs.6b08177] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A metastable, polymorphic hexameric crystal structure of lithium pinacolone enolate (LiOPin) is reported along with three preparation methods. NMR-based structural characterization implies that the lithium pinacolate hexamer deaggregates to a tetramer in toluene but retains mainly the hexameric structure in nonaromatic hydrocarbon solvents such as cyclohexane. Moreover, the presence of a small amount of lithium aldolate (LiOA) dramatically influences the aggregation state of LiOPin by forming a mixed aggregate with a 3:1 ratio (LiOPin3·LiOA).
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Affiliation(s)
- Jie Guang
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Qiyong Liu
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Russell Hopson
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Gerald Kagan
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Weibin Li
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Thomas B Monroe
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
| | - Paul G Williard
- Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States
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19
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Abstract
![]()
In
this paper, we investigate the coassembly of peptides derived
from the central and C-terminal regions of the β-amyloid peptide
(Aβ). In the preceding paper, J. Am. Chem. Soc.2016, DOI: 10.1021/jacs.6b06000, we established that peptides containing residues 17–23 (LVFFAED)
from the central region of Aβ and residues 30–36 (AIIGLMV)
from the C-terminal region of Aβ assemble to form homotetramers
consisting of two hydrogen-bonded dimers. Here, we mix these tetramer-forming
peptides and determine how they coassemble. Incorporation of a single 15N isotopic label into each peptide provides a spectroscopic
probe with which to elucidate the coassembly of the peptides by 1H,15N HSQC. Job’s method of continuous variation
and nonlinear least-squares fitting reveal that the peptides form
a mixture of heterotetramers in 3:1, 2:2, and 1:3 stoichiometries,
in addition to the homotetramers. These studies also establish the
relative stability of each tetramer and show that the 2:2 heterotetramer
predominates. 15N-Edited NOESY shows the 2:2 heterotetramer
comprises two different homodimers, rather than two heterodimers.
The peptides within the heterotetramer segregate in forming the homodimer
subunits, but the two homodimers coassemble in forming the heterotetramer.
These studies show that the central and C-terminal regions of Aβ
can preferentially segregate within β-sheets and that the resulting
segregated β-sheets can further coassemble.
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Affiliation(s)
- Nicholas L Truex
- Department of Chemistry, University of California, Irvine , Irvine, California 92697-2025, United States
| | - James S Nowick
- Department of Chemistry, University of California, Irvine , Irvine, California 92697-2025, United States
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20
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Houghton MJ, Biok NA, Huck CJ, Algera RF, Keresztes I, Wright SW, Collum DB. Lithium Enolates Derived from Pyroglutaminol: Aggregation, Solvation, and Atropisomerism. J Org Chem 2016; 81:4149-57. [PMID: 27035057 PMCID: PMC5245164 DOI: 10.1021/acs.joc.6b00459] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lithium enolates derived from protected pyroglutaminols were characterized by using (6)Li, (13)C, and (19)F NMR spectroscopies in conjunction with the method of continuous variations. Mixtures of tetrasolvated dimers and tetrasolvated tetramers in different proportions depend on the steric demands of the hemiaminal protecting group, tetrahydrofuran concentration, and the presence or absence of an α-fluoro moiety. The high steric demands of the substituted bicyclo[3.3.0] ring system promote dimers to an unusual extent and allow solvents and atropisomers in cubic tetramers to be observed in the slow-exchange limit. Pyridine used as a (6)Li chemical shift reagent proved useful in assigning solvation numbers.
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Affiliation(s)
- Michael J. Houghton
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Naomi A. Biok
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Christopher J. Huck
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Russell F. Algera
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Ivan Keresztes
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Stephen W. Wright
- Worldwide Medicinal Chemistry, Pfizer Global Research and Development, 445 Eastern Point Road, Groton, CT 06340
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
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21
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McNeil AJ. My maize and blue brick road to physical organic chemistry in materials. Beilstein J Org Chem 2016; 12:229-38. [PMID: 26977181 PMCID: PMC4778497 DOI: 10.3762/bjoc.12.24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/01/2016] [Indexed: 11/23/2022] Open
Abstract
Similar to Dorothy’s journey along the yellow brick road in The Wizard of Oz, this perspective carves out the path I took from my early childhood fascinations with science through my independent career at the University of Michigan (maize and blue). The influential research projects and mentors are highlighted, including some fortuitous experimental results that drew me into the field of supramolecular chemistry, specifically, and organic materials, broadly. My research group’s efforts toward designing new sensors based on small molecule gelators are described. In particular, I highlight how our design strategy has evolved as we learn more about molecular gelators. This perspective concludes with some predictions about where molecular gels, as well as my personal and professional life, are headed.
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Affiliation(s)
- Anne J McNeil
- Department of Chemistry and Macromolecular Science and Engineering Program, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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22
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Jin KJ, Collum DB. Solid-State and Solution Structures of Glycinimine-Derived Lithium Enolates. J Am Chem Soc 2015; 137:14446-55. [PMID: 26554898 PMCID: PMC4762874 DOI: 10.1021/jacs.5b09524] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A combination of crystallographic, spectroscopic, and computational studies was applied to study the structures of lithium enolates derived from glycinimines of benzophenone and (+)-camphor. The solvents examined included toluene and toluene containing various concentrations of tetrahydrofuran, N,N,N',N'-tetramethylethylenediamine (TMEDA), (R,R)-N,N,N',N'-tetramethylcyclohexanediamine [(R,R)-TMCDA], and (S,S)-N,N,N',N'-tetramethylcyclohexanediamine [(S,S)-TMCDA]. Crystal structures show chelated monomers, symmetric disolvated dimers, S4-symmetric tetramers, and both S6- and D3d-symmetric hexamers. (6)Li NMR spectroscopic studies in conjunction with the method of continuous variations show how these species distribute in solution. Density functional theory computations offer insights into experimentally elusive details.
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Affiliation(s)
- Kyoung Joo Jin
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
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23
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Tallmadge EH, Collum DB. Evans Enolates: Solution Structures of Lithiated Oxazolidinone-Derived Enolates. J Am Chem Soc 2015; 137:13087-95. [PMID: 26437278 PMCID: PMC4765922 DOI: 10.1021/jacs.5b08207] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The results of a combination of (6)Li and (13)C NMR spectroscopic and computational studies of oxazolidinone-based lithium enolates-Evans enolates-in tetrahydrofuran (THF) solution revealed a mixture of dimers, tetramers, and oligomers (possibly ladders). The distribution depended on the structure of the oxazolidinone auxiliary, substituent on the enolate, and THF concentration (in THF/toluene mixtures). The unsolvated tetrameric form contained a D(2d)-symmetric core structure, whereas the dimers were determined experimentally and computationally to be trisolvates with several isomeric forms.
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Affiliation(s)
- Evan H Tallmadge
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853-1301, United States
| | - David B Collum
- Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University , Ithaca, New York 14853-1301, United States
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24
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Roca-López D, Polo V, Tejero T, Merino P. Mechanism Switch in Mannich-Type Reactions: ELF and NCI Topological Analyses of the Reaction between Nitrones and Lithium Enolates. European J Org Chem 2015. [DOI: 10.1002/ejoc.201500447] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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25
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Tomasevich L, Collum DB. Method of continuous variation: characterization of alkali metal enolates using ¹H and ¹⁹F NMR spectroscopies. J Am Chem Soc 2014; 136:9710-8. [PMID: 24915602 PMCID: PMC4105082 DOI: 10.1021/ja504365z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Indexed: 11/29/2022]
Abstract
The method of continuous variation in conjunction with (1)H and (19)F NMR spectroscopies was used to characterize lithium and sodium enolates solvated by N,N,N',N'-tetramethylethyldiamine (TMEDA) and tetrahydrofuran (THF). A strategy developed using lithium enolates was then applied to the more challenging sodium enolates. A number of sodium enolates solvated by TMEDA or THF afford exclusively tetramers. Evidence suggests that TMEDA chelates sodium on cubic tetramers.
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Affiliation(s)
- Laura
L. Tomasevich
- Department
of Chemistry and
Chemical Biology, Baker Laboratory, Cornell
University , Ithaca, New York 14853-1301, United States
| | - David B. Collum
- Department
of Chemistry and
Chemical Biology, Baker Laboratory, Cornell
University , Ithaca, New York 14853-1301, United States
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26
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Bruneau A, Liou L, Collum DB. Solution structures of lithium amino alkoxides used in highly enantioselective 1,2-additions. J Am Chem Soc 2014; 136:2885-91. [PMID: 24471766 PMCID: PMC3985715 DOI: 10.1021/ja412210d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Indexed: 01/25/2023]
Abstract
Lithium ephedrates and norcarane-derived lithium amino alkoxides used to effect highly enantioselective 1,2-additions on large scales have been characterized in toluene and tetrahydrofuran. The method of continuous variations in conjunction with (6)Li NMR spectroscopy reveals that the lithium amino alkoxides are tetrameric. In each case, low-temperature (6)Li NMR spectra show stereoisomerically pure homoaggregates displaying resonances consistent with an S4-symmetric cubic core rather than the alternative D2d core. These assignments are supported by density functional theory computations and conform to X-ray crystal structures. Slow aggregate exchanges are discussed in the context of amino alkoxides as chiral auxiliaries.
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Affiliation(s)
- Angela
M. Bruneau
- Department of Chemistry and
Chemical Biology Baker Laboratory, Cornell
University, Ithaca, New York 14853-1301, United States
| | - Lara Liou
- Department of Chemistry and
Chemical Biology Baker Laboratory, Cornell
University, Ithaca, New York 14853-1301, United States
| | - David B. Collum
- Department of Chemistry and
Chemical Biology Baker Laboratory, Cornell
University, Ithaca, New York 14853-1301, United States
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27
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Renny JS, Tomasevich LL, Tallmadge EH, Collum DB. Method of continuous variations: applications of job plots to the study of molecular associations in organometallic chemistry. Angew Chem Int Ed Engl 2013; 52:11998-2013. [PMID: 24166797 PMCID: PMC4028694 DOI: 10.1002/anie.201304157] [Citation(s) in RCA: 429] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Indexed: 11/10/2022]
Abstract
Applications of the method of continuous variations (MCV or the Method of Job) to problems of interest to organometallic chemists are described. MCV provides qualitative and quantitative insights into the stoichiometries underlying association of m molecules of A and n molecules of B to form A(m)B(n) . Applications to complex ensembles probe associations that form metal clusters and aggregates. Job plots in which reaction rates are monitored provide relative stoichiometries in rate-limiting transition structures. In a specialized variant, ligand- or solvent-dependent reaction rates are dissected into contributions in both the ground states and transition states, which affords insights into the full reaction coordinate from a single Job plot. Gaps in the literature are identified and critiqued.
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Affiliation(s)
- Joseph S. Renny
- Contribution from the Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Laura L. Tomasevich
- Contribution from the Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Evan H. Tallmadge
- Contribution from the Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - David B. Collum
- Contribution from the Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
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28
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Renny JS, Tomasevich LL, Tallmadge EH, Collum DB. Methode der kontinuierlichen Variation: Verwendung von Job-Plots zur Untersuchung molekularer Assoziationen in der metallorganischen Chemie. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201304157] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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29
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Larrañaga O, de Cózar A, Bickelhaupt FM, Zangi R, Cossío FP. Aggregation and cooperative effects in the aldol reactions of lithium enolates. Chemistry 2013; 19:13761-73. [PMID: 23964002 DOI: 10.1002/chem.201301597] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Indexed: 11/11/2022]
Abstract
Density functional theory and Car-Parrinello molecular dynamics simulations have been carried out for model aldol reactions involving aggregates of lithium enolates derived from acetaldehyde and acetone. Formaldehyde and acetone have been used as electrophiles. It is found that the geometries of the enolate aggregates are in general determined by the most favorable arrangements of the point charges within the respective Lin On clusters. The reactivity of the enolates follows the sequence monomer≫dimer>tetramer. In lithium aggregates, the initially formed aldol adducts must rearrange to form more stable structures in which the enolate and alkoxide oxygen atoms are within the respective Lin On clusters. Positive cooperative effects, similar to allosteric effects found in several proteins, are found for the successive aldol reactions in aggregates. The corresponding transition structures show in general sofa geometries.
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Affiliation(s)
- Olatz Larrañaga
- Departamento de Química Orgánica I/, Kimika Organikoa I Saila, Facultad de Química/, Kimika Fakultatea Euskal Herriko Unibertsitatea, UPV/EHU and Donostia International Physics Center (DIPC), 1072, 20018 San Sebastián-Donostia (Spain)
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30
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Zhou Z, Qin W, Chu Y, Fei W. Elucidation of the structures of tributyl phosphate/Li complexes in the presence of FeCl3 via UV–visible, Raman and IR spectroscopy and the method of continuous variation. Chem Eng Sci 2013. [DOI: 10.1016/j.ces.2013.07.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Harrison-Marchand A, Mongin F. Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 1. Structural Data. Chem Rev 2013; 113:7470-562. [DOI: 10.1021/cr300295w] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anne Harrison-Marchand
- Laboratoire COBRA de l′Université de Rouen, INSA de Rouen, CNRS, UMR 6014 & FR 3038, IRCOF, Rue Tesnière, 76821 Mont St Aignan Cédex, France
| | - Florence Mongin
- Équipe Chimie et Photonique Moléculaires, Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS-Université de Rennes 1, Bâtiment 10A, case 1003, Avenue du Général Leclerc, 35042 Rennes Cédex, France
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32
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Reich HJ. Role of Organolithium Aggregates and Mixed Aggregates in Organolithium Mechanisms. Chem Rev 2013; 113:7130-78. [DOI: 10.1021/cr400187u] [Citation(s) in RCA: 248] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Hans J. Reich
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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33
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Tomasevich LL, Collum DB. Structure determination using the method of continuous variation: lithium phenolates solvated by protic and dipolar aprotic ligands. J Org Chem 2013; 78:7498-507. [PMID: 23806055 PMCID: PMC3759316 DOI: 10.1021/jo401080n] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The method of continuous variation (MCV) was used in conjunction with (6)Li NMR spectroscopy to characterize four lithium phenolates solvated by a range of solvents, including N,N,N',N'-tetramethylethylenediamine, Et2O, pyridine, protic amines, alcohols, and highly dipolar aprotic solvents. Dimers, trimers, and tetramers were observed, depending on the precise lithium phenolate-solvent combinations. Competition experiments (solvent swaps) provide insights into the relative propensities toward mixed solvation.
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Affiliation(s)
- Laura L. Tomasevich
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
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34
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De Vries TS, Bruneau AM, Liou LR, Subramanian H, Collum DB. Azaaldol condensation of a lithium enolate solvated by N,N,N',N'-tetramethylethylenediamine: dimer-based 1,2-addition to imines. J Am Chem Soc 2013; 135:4103-9. [PMID: 23413774 PMCID: PMC3715612 DOI: 10.1021/ja400345c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The lithium enolate of tert-amylacetate solvated by N,N,N',N'-tetramethylethylenediamine (TMEDA) is shown to be a doubly chelated dimer. Adding the dimeric enolate to 4-fluorobenzaldehyde-N-phenylimine affords an N-lithiated β-amino ester shown to be monomeric using (6)Li and (15)N NMR spectroscopies. Rate studies using (19)F NMR spectroscopy reveal reaction orders consistent with a transition structure of stoichiometry [(ROLi)2(TMEDA)2(imine)](‡). Density functional theory computations explore several possible dimer-based transition structures with monodentate and bidentate coordination of TMEDA. Supporting rate studies using trans-N,N,N',N'-1,2-tetramethylcyclohexanediamine showing analogous rates and rate law suggest that TMEDA is fully chelated.
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Affiliation(s)
- Timothy S. De Vries
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Angela M. Bruneau
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | - Lara R. Liou
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
| | | | - David B. Collum
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University, Ithaca, New York 14853–1301
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35
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Lazny R, Wolosewicz K. An expedient preparation of amine-free lithium enolates using immobilized amide reagents. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2012.12.067] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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36
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Glaser R, Ulmer L, Coyle S. Mechanistic models for LAH reductions of acetonitrile and malononitrile. Aggregation effects of Li+ and AlH3 on imide-enamide equilibria. J Org Chem 2013; 78:1113-26. [PMID: 23327108 DOI: 10.1021/jo302527k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The results are reported of an ab initio study of the addition of LiAlH(4) to acetonitrile and malononitrile at the MP2(full)/6-311+G* level considering the effects of electron correlation at higher levels up to QCISD(T)/6-311++G(2df,2pd) and including ether solvation. All imide (RCH(2)CH═N(-)) and enamide (RCH(-)CH═NH ↔ RCH═CHN(-)H) adducts feature strong interactions between the organic anion and both Li(+) and AlH(3). The relative stabilities of the tautomeric LAH adducts are compared to the tautomer preference energies of the LiH adducts and of the hydride adducts of the nitriles. Alane affinities were determined for the lithium ion pairs formed by LiH addition to the nitriles. The results show that alane binding greatly affects the imide-enamide equilibria and that alane complexation might even provide a thermodynamic preference for the imide intermediate. While lithium enamides of malononitrile are much more stable than lithium imides, alane binding dramatically reduces the enamide preference so that both tautomers are present at equilibrium. Implications are discussed regarding to the propensity for multiple hydride reductions and with regard to the mechanism of reductive nitrile dimerization. A detailed mechanism is proposed for the formation of 2-aminonicotinonitrile (2ANN) in the LAH reduction of malononitrile.
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Affiliation(s)
- Rainer Glaser
- Department of Chemistry, University of Missouri, Columbia, Missouri 65211, USA.
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37
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Sakata T, Seki N, Yomogida K, Yamagishi H, Otsuki A, Inoh C, Yamataka H. Origin of regioselectivity in the reactions of nitronate and enolate ambident anions. J Org Chem 2012; 77:10738-44. [PMID: 23136916 DOI: 10.1021/jo302103c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reactions of nitronates of ring-substituted phenylnitromethanes and enolates of ring-substituted 1-phenyl-2-propanones with MeOBs gave exclusively the O-methylated and C-methylated products, respectively. DFT calculations suggested that two factors, namely, intrinsic barriers and metal-cation coordination, control the C/O selectivity. The kinetic preference for O-methylation in the reactions of nitronates arises from the intrinsic barriers, which are ca. 10 kcal/mol lower for O-methylation than for C-methylation. The situation is the same for the gas-phase reaction of an enolate, in which the O-methylation is more favorable than the C-methylation. The experimentally observed C-selectivity of enolate reactions in solution is due to the metal-cation coordination, which hinders O-methylation for enolates. The effects of the enolate reactivity and the solvent on the C/O selectivity are also rationalized to arise from the two factors.
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Affiliation(s)
- Tomomi Sakata
- Department of Chemistry and the Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro, Toshima-ku 171-8501, Tokyo, Japan
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38
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Patil M, Thiel W. Origin of Selectivity of Tsuji-Trost Allylic Alkylation of Lactones: Highly Ordered Transition States with Lithium-Containing Enolates. Chemistry 2012; 18:10408-18. [DOI: 10.1002/chem.201201267] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Indexed: 11/11/2022]
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39
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Affiliation(s)
- Hans J. Reich
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
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40
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Kolonko KJ, Wherritt DJ, Reich HJ. Mechanistic studies of the lithium enolate of 4-fluoroacetophenone: rapid-injection NMR study of enolate formation, dynamics, and aldol reactivity. J Am Chem Soc 2011; 133:16774-7. [PMID: 21939211 DOI: 10.1021/ja207218f] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lithium enolates are widely used nucleophiles with a complicated and only partially understood solution chemistry. Deprotonation of 4-fluoroacetophenone in THF with lithium diisopropylamide occurs through direct reaction of the amide dimer to yield a mixed enolate-amide dimer (3), then an enolate homodimer (1-Li)(2), and finally an enolate tetramer (1-Li)(4), the equilibrium structure. Aldol reactions of both the metastable dimer and the stable tetramer of the enolate were investigated. Each reacted directly with the aldehyde to give a mixed enolate-aldolate aggregate, with the dimer only about 20 times as reactive as the tetramer at -120 °C.
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Affiliation(s)
- Kristopher J Kolonko
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, USA
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41
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Casey BM, Flowers RA. On the nature of the oxidative heterocoupling of lithium enolates. J Am Chem Soc 2011; 133:11492-5. [PMID: 21721524 DOI: 10.1021/ja205017e] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The coupling of enolates through single-electron oxidation is one of the most direct routes for generating 1,4-dicarbonyls. Recent work on the intermolecular heterocoupling of equimolar amounts of two different enolates through single-electron oxidation has shown that synthetically useful yields beyond those predicted by statistics can be obtained. To determine the underlying basis for the selective formation of heterocoupled products, kinetic, (7)Li NMR, and synthetic studies were performed. The collection of data obtained from these experiments shows that the selective formation of heterocoupled products is a consequence of heteroaggregation of lithium enolates.
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Affiliation(s)
- Brian M Casey
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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42
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Erb J, Paull DH, Dudding T, Belding L, Lectka T. From bifunctional to trifunctional (tricomponent nucleophile-transition metal-lewis acid) catalysis: the catalytic, enantioselective α-fluorination of acid chlorides. J Am Chem Soc 2011; 133:7536-46. [PMID: 21513338 PMCID: PMC3432319 DOI: 10.1021/ja2014345] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report in full detail our studies on the catalytic, asymmetric α-fluorination of acid chlorides, a practical method that produces an array of α-fluorocarboxylic acid derivatives in which improved yield and virtually complete enantioselectivity are controlled through electrophilic fluorination of a ketene enolate intermediate. We discovered, for the first time, that a third catalyst, a Lewis acidic lithium salt, could be introduced into a dually activated system to amplify yields of aliphatic products, primarily through activation of the fluorinating agent. Through our mechanistic studies (based on kinetic data, isotopic labeling, spectroscopic measurements, and theoretical calculations) we were able to utilize our understanding of this "trifunctional" reaction to optimize the conditions and obtain new products in good yield and excellent enantioselectivity.
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Affiliation(s)
- Jeremy Erb
- Department of Chemistry, New Chemistry Building, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland, 21218
| | - Daniel H. Paull
- Department of Chemistry, New Chemistry Building, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland, 21218
| | - Travis Dudding
- Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada L2S 3A1
| | - Lee Belding
- Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada L2S 3A1
| | - Thomas Lectka
- Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada L2S 3A1
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Kagan G, Li W, Li D, Hopson R, Williard PG. Characterization of dimeric chiral lithium amide structures derived from N-isopropyl-O- triisopropylsilyl valinol. J Am Chem Soc 2011; 133:6596-602. [PMID: 21486016 DOI: 10.1021/ja109041z] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dimeric structure is characterized for a chiral amide base complex consisting of an (S)-N-isopropyl-O-triisopropylsilyl valinol ligand and lithium. The complex is characterized by a variety of NMR techniques, including multinuclear one- and two-dimensional NMR experiments and diffusion-ordered NMR spectroscopy (DOSY) as well as diffusion coefficient-formula weight (D-fw) correlation analyses. Spartan calculations are presented which support the structural assignment. This structural characterization leads to an explanation of the behavior and the reactivity of these complexes in solution.
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Affiliation(s)
- Gerald Kagan
- Department of Chemistry, Brown University, 324 Brook Street, Providence, Rhode Island 02912, USA
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Ma Y, Hoepker AC, Gupta L, Faggin MF, Collum DB. 1,4-addition of lithium diisopropylamide to unsaturated esters: role of rate-limiting deaggregation, autocatalysis, lithium chloride catalysis, and other mixed aggregation effects. J Am Chem Soc 2010; 132:15610-23. [PMID: 20961095 PMCID: PMC2989387 DOI: 10.1021/ja105855v] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Lithium diisopropylamide (LDA) in tetrahydrofuran at -78 °C undergoes 1,4-addition to an unsaturated ester via a rate-limiting deaggregation of LDA dimer followed by a post-rate-limiting reaction with the substrate. Muted autocatalysis is traced to a lithium enolate-mediated deaggregation of the LDA dimer and the intervention of LDA-lithium enolate mixed aggregates displaying higher reactivities than LDA. Striking accelerations are elicited by <1.0 mol % LiCl. Rate and mechanistic studies have revealed that the uncatalyzed and catalyzed pathways funnel through a common monosolvated-monomer-based intermediate. Four distinct classes of mixed aggregation effects are discussed.
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Affiliation(s)
- Yun Ma
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Alexander C. Hoepker
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Lekha Gupta
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - Marc F. Faggin
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
| | - David B. Collum
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301
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Lecachey B, Oulyadi H, Lameiras P, Harrison-Marchand A, Gérard H, Maddaluno J. MeLi + LiCl in THF: One Heterodimer and No Tetramers. J Org Chem 2010; 75:5976-83. [DOI: 10.1021/jo101282m] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Baptiste Lecachey
- CNRS UMR 6014 & FR 3038, Université de Rouen and INSA de Rouen, 76821 Mont St. Aignan Cedex, France
| | - Hassan Oulyadi
- CNRS UMR 6014 & FR 3038, Université de Rouen and INSA de Rouen, 76821 Mont St. Aignan Cedex, France
| | - Pedro Lameiras
- CNRS UMR 6014 & FR 3038, Université de Rouen and INSA de Rouen, 76821 Mont St. Aignan Cedex, France
| | - Anne Harrison-Marchand
- CNRS UMR 6014 & FR 3038, Université de Rouen and INSA de Rouen, 76821 Mont St. Aignan Cedex, France
| | - Hélène Gérard
- UPMC Univ Paris 6 and CNRS, UMR 7616, Laboratoire de Chimie Théorique, 4 place Jussieu, 75252 Paris Cedex 05, France
| | - Jacques Maddaluno
- CNRS UMR 6014 & FR 3038, Université de Rouen and INSA de Rouen, 76821 Mont St. Aignan Cedex, France
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Cousins DM, Davidson MG, Frankis CJ, García-Vivó D, Mahon MF. Tris(2-dimethylaminoethyl)amine: a simple new tripodal polyamine ligand for Group 1 metals. Dalton Trans 2010; 39:8278-80. [DOI: 10.1039/c0dt00567c] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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47
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De Vries TS, Goswami A, Liou LR, Gruver JM, Jayne E, Collum DB. Lithium phenolates solvated by tetrahydrofuran and 1,2-dimethoxyethane: structure determination using the method of continuous variation. J Am Chem Soc 2009; 131:13142-54. [PMID: 19702308 PMCID: PMC2752606 DOI: 10.1021/ja9047784] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The method of continuous variation in conjunction with (6)Li NMR spectroscopy was used to characterize lithium phenolates solvated by tetrahydrofuran and 1,2-dimethoxyethane. The strategy relies on the formation of ensembles of homo- and heteroaggregated phenolates. The symmetries and concentration dependencies of the heteroaggregates attest to the aggregation numbers of the homoaggregates. The structurally diverse phenols afford substrate- and solvent-dependent combinations of lithium phenolate monomers, dimers, trimers, tetramers, and pentamers. We discuss the refinement of protocols for characterizing O-lithiated species. Computational studies examine further the substituent and solvent dependencies of aggregation.
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Affiliation(s)
- Timothy S De Vries
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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Kolonko KJ, Biddle MM, Guzei IA, Reich HJ. Solution Structures of Lithium Enolates of Cyclopentanone, Cyclohexanone, Acetophenones, and Benzyl Ketones. Triple Ions and Higher Lithiate Complexes. J Am Chem Soc 2009; 131:11525-34. [DOI: 10.1021/ja903479p] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Margaret M. Biddle
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Ilia A. Guzei
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Hans J. Reich
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706
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De Sterck B, Van Speybroeck V, Mangelinckx S, Verniest G, De Kimpe N, Waroquier M. Theoretical Study on the Structural Properties of Various Solvated Metalated 3-Halo-1-azaallylic Anions. J Phys Chem A 2009; 113:6375-80. [DOI: 10.1021/jp811317y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bart De Sterck
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium, and Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Veronique Van Speybroeck
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium, and Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Sven Mangelinckx
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium, and Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Guido Verniest
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium, and Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Norbert De Kimpe
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium, and Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
| | - Michel Waroquier
- Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium, and Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
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Declerck R, De Sterck B, Verstraelen T, Verniest G, Mangelinckx S, Jacobs J, De Kimpe N, Waroquier M, Van Speybroeck V. Insight into the Solvation and Isomerization of 3-Halo-1-azaallylic Anions from Ab Initio Metadynamics Calculations and NMR Experiments. Chemistry 2009; 15:580-4. [DOI: 10.1002/chem.200800948] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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