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Amberchan G, Snelling RA, Moya E, Landi M, Lutz K, Gatihi R, Singaram B. Reaction of Diisobutylaluminum Borohydride, a Binary Hydride, with Selected Organic Compounds Containing Representative Functional Groups. J Org Chem 2021; 86:6207-6227. [PMID: 33843216 DOI: 10.1021/acs.joc.0c03062] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The binary hydride, diisobutylaluminum borohydride [(iBu)2AlBH4], synthesized from diisobutylaluminum hydride (DIBAL) and borane dimethyl sulfide (BMS) has shown great potential in reducing a variety of organic functional groups. This unique binary hydride, (iBu)2AlBH4, is readily synthesized, versatile, and simple to use. Aldehydes, ketones, esters, and epoxides are reduced very fast to the corresponding alcohols in essentially quantitative yields. This binary hydride can reduce tertiary amides rapidly to the corresponding amines at 25 °C in an efficient manner. Furthermore, nitriles are converted into the corresponding amines in essentially quantitative yields. These reactions occur under ambient conditions and are completed in an hour or less. The reduction products are isolated through a simple acid-base extraction and without the use of column chromatography. Further investigation showed that (iBu)2AlBH4 has the potential to be a selective hydride donor as shown through a series of competitive reactions. Similarities and differences between (iBu)2AlBH4, DIBAL, and BMS are discussed.
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Affiliation(s)
- Gabriella Amberchan
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Rachel A Snelling
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Enrique Moya
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Madison Landi
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Kyle Lutz
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Roxanne Gatihi
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
| | - Bakthan Singaram
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, United States
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2
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Nikitin K, O'Gara R. Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy. Chemistry 2019; 25:4551-4589. [PMID: 30421834 DOI: 10.1002/chem.201804123] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Indexed: 12/31/2022]
Abstract
Detailed mechanistic information is crucial to our understanding of reaction pathways and selectivity. Dynamic exchange NMR techniques, in particular 2D exchange spectroscopy (EXSY) and its modifications, provide indispensable intricate information on the mechanisms of organic and inorganic reactions and other phenomena, for example, the dynamics of interfacial processes. In this Review, key results from exchange NMR studies of small molecules over the last few decades are systemised and discussed. After a brief introduction to the theory, the key types of dynamic processes are identified and fundamental examples given of intra- and intermolecular reactions, which, in turn, could involve, or not, bond-making and bond-breaking events. Following that logic, internal molecular rotation, intramolecular stereomutation and molecular recognition will first be considered because they do not typically involve bond breaking. Then, rearrangements, substitution-type reactions, cyclisations, additions and other processes affecting chemical bonds will be discussed. Finally, interfacial molecular dynamics and unexpected combinations of different types of fluxional processes will also be highlighted. How exchange NMR spectroscopy helps to identify conformational changes, coordination and molecular recognition processes as well as quantify reaction energy barriers and extract detailed mechanistic information by using reaction rate theory in conjunction with computational techniques will be shown.
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Affiliation(s)
- Kirill Nikitin
- School of Chemistry, University College Dublin, Belfield, Dublin, Ireland
| | - Ryan O'Gara
- School of Chemistry, University College Dublin, Belfield, Dublin, Ireland
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Neufeld R, John M, Stalke D. The Donor-Base-Free Aggregation of Lithium Diisopropyl Amide in Hydrocarbons Revealed by a DOSY Method. Angew Chem Int Ed Engl 2015; 54:6994-8. [PMID: 26014367 DOI: 10.1002/anie.201502576] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Indexed: 11/08/2022]
Abstract
Lithium diisopropyl amide (LDA) is a very prominent reagent that plays a key role in organic synthesis, serving as a base par excellence for a broad range of deprotonation reactions. However, the state of aggregation in solution in the absence of donor bases was unclear. In this paper we solved this problem by employing DOSY NMR experiments based on a newly elaborated external calibration curve (ECC) approach with normalized diffusion coefficients.
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Affiliation(s)
- Roman Neufeld
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077 Göttingen (Germany)
| | - Michael John
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077 Göttingen (Germany)
| | - Dietmar Stalke
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077 Göttingen (Germany).
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Neufeld R, John M, Stalke D. Aufklärung der donorbasenfreien Aggregation von Lithiumdiisopropylamid in Kohlenwasserstoffen mithilfe einer DOSY-Methode. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201502576] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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5
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Mulvey RE, Robertson SD. Synthetically important alkali-metal utility amides: lithium, sodium, and potassium hexamethyldisilazides, diisopropylamides, and tetramethylpiperidides. Angew Chem Int Ed Engl 2013; 52:11470-87. [PMID: 24133015 DOI: 10.1002/anie.201301837] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Indexed: 11/08/2022]
Abstract
Most synthetic chemists will have at some point utilized a sterically demanding secondary amide (R2 N(-) ). The three most important examples, lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS), lithium diisopropylamide (LiDA), and lithium 2,2,6,6-tetramethylpiperidide (LiTMP)-the "utility amides"-have long been indispensible particularly for lithiation (Li-H exchange) reactions. Like organolithium compounds, they exhibit aggregation phenomena and strong Lewis acidity, and thus appear in distinct forms depending on the solvents employed. The structural chemistry of these compounds as well as their sodium and potassium congeners are described in the absence or in the presence of the most synthetically significant donor solvents tetrahydrofuran (THF) and N,N,N',N'-tetramethylethylenediamine (TMEDA) or closely related solvents. Examples of hetero-alkali-metal amides, an increasingly important composition because of the recent escalation of interest in mixed-metal synergic effects, are also included.
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Affiliation(s)
- Robert E Mulvey
- WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL (UK).
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Mulvey RE, Robertson SD. Nützliche Alkalimetallamide für die Synthese: Lithium-, Natrium- und Kaliumhexamethyldisilazide, -diisopropylamide und -tetramethylpiperidide. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201301837] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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7
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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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Abstract
Static high pressure lithium amide (LiNH(2)) crystal structures are predicted using evolutionary structure search methodologies and intuitive approaches. In the process, we explore the relationship of the structure and properties of solid LiNH(2) to its molecular monomer and dimer, as well as its valence-isoelectronic crystalline phases of methane, water, and ammonia all under pressure. A NaNH(2) (Fddd) structure type is found to be competitive for the ground state of LiNH(2) above 6 GPa with the P = 1 atm I4[overline] phase. Three novel phases emerge at 11 (P4[overline]2(1)m), 13 (P4(2)/ncm), and 46 GPa (P2(1)2(1)2(1)), still containing molecular amide anions, which begin to form N-H···N hydrogen bonds. The P2(1)2(1)2(1) phase remains stable over a wide pressure range. This phase and another Pmc2(1) structure found at 280 GPa have infinite ···(H)N···H···N(H)···H polymeric zigzag chains comprising symmetric N···H···N hydrogen bonds with one NH bond kept out of the chain, an interesting general feature found in many of our high pressure (>280 GPa) LiNH(2) structures, with analogies in high pressure H(2)O-ices. All the predicted low enthalpy LiNH(2) phases are calculated to be enthalpically stable with respect to their elements but resist metallization with increasing pressure up to several TPa. The possibility of Li sublattice melting in the intermediate pressure range structures is raised.
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Affiliation(s)
- Dasari L V K Prasad
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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Rustagi V, Tiwari R, Verma AK. AgI-Catalyzed Cascade Strategy: Regioselective Access to Diversely Substituted Fused Benzimidazo[2,1-a]isoquinolines, Naphthyridines, Thienopyridines, and Quinoxalines in Water. European J Org Chem 2012. [DOI: 10.1002/ejoc.201200546] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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Streitwieser A, Facchetti A, Xie L, Zhang X, Wu EC. Ion Pair pKs of Some Amines: Extension of the Computed Lithium pK Scale. J Org Chem 2012; 77:985-90. [DOI: 10.1021/jo202253q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Andrew Streitwieser
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720-1460,
United States
| | - Antonio Facchetti
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720-1460,
United States
| | - Linfeng Xie
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720-1460,
United States
| | - Xingyue Zhang
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720-1460,
United States
| | - Eric C. Wu
- Department of Chemistry, University of California—Berkeley, Berkeley, California 94720-1460,
United States
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11
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Hoepker AC, Gupta L, Ma Y, Faggin MF, Collum DB. Regioselective lithium diisopropylamide-mediated ortholithiation of 1-chloro-3-(trifluoromethyl)benzene: role of autocatalysis, lithium chloride catalysis, and reversibility. J Am Chem Soc 2011; 133:7135-51. [PMID: 21500823 PMCID: PMC3102585 DOI: 10.1021/ja200906z] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ortholithiation of 1-chloro-3-(trifluoromethyl)benzene with lithium diisopropylamide (LDA) in tetrahydrofuran at -78 °C displays characteristics of reactions in which aggregation events are rate limiting. Metalation with lithium-chloride-free LDA involves a rate-limiting deaggregation via dimer-based transition structures. The post-rate-limiting proton transfers are suggested to involve highly solvated triple ions. Autocatalysis by the resulting aryllithiums or catalysis by traces (<100 ppm) of LiCl diverts the reaction through di- and trisolvated monomer-based pathways for metalation at the 2 and 6 positions, respectively. The regiochemistry is dictated by a combination of kinetically controlled metalations overlaid by an equilibration involving diisopropylamine that is shown to occur by the microscopic reverse of the monomer-based metalations.
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Affiliation(s)
- 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
| | - Yun Ma
- 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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12
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Gupta L, Ramírez A, Collum DB. Reaction of lithium diethylamide with an alkyl bromide and alkyl benzenesulfonate: origins of alkylation, elimination, and sulfonation. J Org Chem 2010; 75:8392-9. [PMID: 21077695 DOI: 10.1021/jo101505x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A combination of NMR, kinetic, and computational methods are used to examine reactions of lithium diethylamide in tetrahydrofuran (THF) with n-dodecyl bromide and n-octyl benzenesulfonate. The alkyl bromide undergoes competitive S(N)2 substitution and E2 elimination in proportions independent of all concentrations except for a minor medium effect. Rate studies show that both reactions occur via trisolvated-monomer-based transition structures. The alkyl benzenesulfonate undergoes competitive S(N)2 substitution (minor) and N-sulfonation (major) with N-sulfonation promoted at low THF concentrations. The S(N)2 substitution is shown to proceed via a disolvated monomer suggested computationally to involve a cyclic transition structure. The dominant N-sulfonation follows a disolvated-dimer-based transition structure suggested computationally to be a bicyclo[3.1.1] form. The differing THF and lithium diethylamide orders for the two reactions explain the observed concentration-dependent chemoselectivities.
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Affiliation(s)
- Lekha Gupta
- Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States
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13
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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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14
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Andrews PC, Bull SD, Koutsaplis M. Homo- and heteroanionic alkali metal aza-enolate aggregates derived from o-methylvalerolactim ether. NEW J CHEM 2010. [DOI: 10.1039/c0nj00088d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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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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16
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Pratt LM, Fujiwara SI, Kambe N. Structure, bonding, and aggregation of selenium-containing organolithium species. Tetrahedron 2009. [DOI: 10.1016/j.tet.2008.11.087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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17
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Davies SG, Durbin MJ, Goddard EC, Kelly PM, Kurosawa W, Lee JA, Nicholson RL, Price PD, Roberts PM, Russell AJ, Scott PM, Smith AD. Doubly diastereoselective conjugate addition of homochiral lithium amides to homochiral α,β-unsaturated esters containing cis- and trans-dioxolane units. Org Biomol Chem 2009; 7:761-76. [DOI: 10.1039/b818298a] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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18
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Däschlein C, Strohmann C. Structural Studies on (–)‐Sparteine‐Coordinated Lithiosilanes. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800792] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Christian Däschlein
- Technische Universität Dortmund, Anorganische Chemie, Otto‐Hahn‐Straße 6, 44227 Dortmund
| | - Carsten Strohmann
- Technische Universität Dortmund, Anorganische Chemie, Otto‐Hahn‐Straße 6, 44227 Dortmund
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Riggs JC, Singh KJ, Yun M, Collum DB. Anionic Snieckus-Fries rearrangement: solvent effects and role of mixed aggregates. J Am Chem Soc 2008; 130:13709-17. [PMID: 18798619 PMCID: PMC2626637 DOI: 10.1021/ja804087r] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lithiated aryl carbamates (ArLi) bearing methoxy or fluoro substituents in the meta position are generated from lithium diisopropylamide (LDA) in THF, n-BuOMe, Me2NEt, dimethoxyethane (DME), N,N,N',N'-tetramethylethylenediamine (TMEDA), N,N,N',N'-tetramethylcyclohexanediamine (TMCDA), and hexamethylphosphoramide (HMPA). The aryllithiums are shown with (6)Li, (13)C, and (15)N NMR spectroscopies to be monomers, ArLi-LDA mixed dimers, and ArLi-LDA mixed trimers, depending on the choice of solvent. Subsequent Snieckus-Fries rearrangements afford ArOLi-LDA mixed dimers and trimers of the resulting phenolates. Rate studies of the rearrangement implicate mechanisms based on monomers, mixed dimers, and mixed trimers.
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Affiliation(s)
- Jason C Riggs
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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Li D, Sun C, Liu J, Hopson R, Li W, Williard PG. Aggregation studies of complexes containing a chiral lithium amide and n-Butyllithium. J Org Chem 2008; 73:2373-81. [PMID: 18294002 DOI: 10.1021/jo702655m] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A system consisting of a chiral lithium amide and n-BuLi in tol-d(8) solution was investigated with (1)H and (13)C INEPT DOSY, (6)Li and (15)N NMR, and other 2D NMR techniques. A mixed 2:1 trimeric complex was identified as the major species as the stoichiometry approached 1.5 equiv of n-BuLi to 1 equiv of amine compound. (1)H and (13)C INEPT DOSY spectra confirmed this lithium aggregate in the solution. The formula weight of the aggregate, correlated with diffusion coefficients of internal references, indicated the aggregation number of this complex. Plots of log D(rel) vs log FW are linear (r > 0.9900). (6)Li and (15)N NMR titration experiments also corroborated these results. These NMR experiments indicate that this mixed aggregate is the species that is responsible for asymmetric addition of n-BuLi to aldehydes.
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Affiliation(s)
- Deyu Li
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
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Popenova S, Mawhinney RC, Schreckenbach G. Density Functional Study of Lithium Hexamethyldisilazide (LiHMDS) Complexes: Effects of Solvation and Aggregation. Inorg Chem 2007; 46:3856-64. [PMID: 17432844 DOI: 10.1021/ic061599s] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The title compound, lithium hexamethyldisilazide (LiHMDS), has been studied using modern quantum-chemical methods in the form of the B3LYP approach. Monomers, dimers, trimers, and tetramers, microsolvated with up to four THF molecules have been considered. The choice of model complex is seen to be important-for instance, the simpler water molecule is shown to be an inappropriate substitute for the THF solvent. Calculated lithium NMR shieldings are reported, but by themselves, they seem to be insufficient for unequivocal assignments of the different species. The energetics of aggregation and solvation have been studied. Temperature effects are seen to be important, and the degrees of solvation and aggregation are higher at 0 K than at 298 K. The highest degree of THF solvation for the monomer and dimer is found to be three (0 K) and two (298 K), respectively. The highest possible degree of aggregation for unsolvated LiHMDS is four. However, in nonpolar solvents, formation of the LiHDMS dimer from the trimer is thermodynamically preferred. The pathway is likely to involve an intermediate tetramer. In THF solution, di-solvated monomers and dimers are the most likely species.
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Affiliation(s)
- Svetlana Popenova
- Department of Chemistry and Biochemistry, Concordia University, Montreal QC, Canada H3G 1M8
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Singh KJ, Collum DB. Lithium Diisopropylamide-Mediated Ortholithiation and Anionic Fries Rearrangement of Aryl Carbamates: Role of Aggregates and Mixed Aggregates. J Am Chem Soc 2006; 128:13753-60. [PMID: 17044703 DOI: 10.1021/ja064655x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structural and mechanistic studies of the lithium diisopropylamide (LDA)-mediated anionic Fries rearrangements of aryl carbamates are described. Substituents at the meta position of the arene (H, OMe, F) and the dialkylamino moiety of the carbamate (Me(2)N, Et(2)N, and i-Pr(2)N) markedly influence the relative rates of ortholithiation and subsequent Fries rearrangement. Structural studies using (6)Li and (15)N NMR spectroscopies on samples derived from [(6)Li,(15)N]LDA reveal an LDA dimer, LDA dimer-arene complexes, an aryllithium monomer, LDA-aryllithium mixed dimers, an LDA-lithium phenolate mixed dimer, and homoaggregated lithium phenolates. The highly insoluble phenolate was characterized as a dimer by X-ray crystallography. Rate studies show monomer- and dimer-based ortholithiations as well as monomer- and mixed dimer-based Fries rearrangements. Density functional theory computational studies probe experimentally elusive structural and mechanistic details.
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Affiliation(s)
- Kanwal Jit Singh
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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Ramirez A, Sun X, Collum DB. Lithium Diisopropylamide-Mediated Enolization: Catalysis by Hemilabile Ligands. J Am Chem Soc 2006; 128:10326-36. [PMID: 16881665 DOI: 10.1021/ja062147h] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structural, kinetic, and computational studies reveal the mechanistic complexities of a lithium diisopropylamide (LDA)-mediated ester enolization. Hemilabile amino ether MeOCH2CH2NMe2, binding as an eta1 (ether-bound) ligand in the reactant and as an eta2 (chelating) ligand in the transition structure, accelerates the enolization 10,000-fold compared with n-BuOMe. At the onset of the reaction, a dimer-based enolization prevails. As the reaction proceeds, significantly less reactive LDA-enolate mixed dimers appear and divert the reaction through monomer- and mixed dimer-based pathways. The mechanistic and computational investigations lead to a proof-of-principle ligand-catalyzed enolization in which an ancillary ligand allows the catalytic ligand to re-enter the catalytic cycle.
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Affiliation(s)
- Antonio Ramirez
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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Abstract
Phase diagrams are reported for glyme mixtures with simple lithium salts. The glymes studied include monoglyme (DME), diglyme, triglyme, and tetraglyme. The lithium salts include LiBETI, LiAsF6, LiI, LiClO4, LiBF4, LiCF3SO3, LiBr, LiNO3, and LiCF3CO2. The phase diagrams clearly illustrate how solvate formation and thermophysical properties are dictated by the ionic association strength of the salt (i.e., the properties of the anions) and chain length of the solvating molecules. This information provides critical predictive capabilities for solvate formation and ionic interactions common in organometallic reagents and battery electrolytes.
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Affiliation(s)
- Wesley A Henderson
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
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Granander J, Sott R, Hilmersson G. Correlation between the6Li,15N Coupling Constant and the Coordination Number at Lithium. Chemistry 2006; 12:4191-7. [PMID: 16526078 DOI: 10.1002/chem.200501371] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The 6Li,15N coupling constants of lithium amide dimers and their mixed complexes with n-butyllithium, formed from five different chiral amines derived from (S)-[15N]phenylalanine, were determined in diethyl ether (Et2O), tetrahydrofuran (THF) and toluene. Results of NMR spectroscopy studies of these complexes show a clear difference in 6Li,15N coupling constants between di-, tri- and tetracoordinated lithium atoms. The lithium amide dimers with a chelating ether group exhibit 6Li,15N coupling constants of approximately 3.8 and approximately 5.5 Hz for the tetracoordinated and tricoordinated lithium atoms, respectively. The lithium amide dimers with a chelating thioether group show distinctly larger 6Li,15N coupling constants of approximately 4.4 Hz for the tetracoordinated lithium atoms, and the tricoordinated lithium atoms have smaller 6Li,15N coupling constants, approximately 4.9 Hz, than their ether analogues. In diethyl ether and tetrahydrofuran, mixed dimeric complexes between the lithium amides and n-butyllithium are formed. The tetracoordinated lithium atoms of these complexes have 6Li,15N coupling constants of approximately 4.0 Hz, and the 6Li,15N coupling constants of the tricoordinated lithium atoms differ somewhat, depending on whether the chelating group is an ether or a thioether; approximately 5.1 and approximately 4.6 Hz, respectively. In toluene, mixed trimeric complexes are formed from two lithium amide moieties and one n-butyllithium. In these trimers, two lithium atoms are tricoordinated with 6Li,15N coupling constants of approximately 4.6 Hz and one lithium is dicoordinated with 6Li,15N coupling constants of approximately 6.5 Hz.
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Affiliation(s)
- Johan Granander
- Department of Chemistry, Göteborg University, 41296 Göteborg, Sweden
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Zuend SJ, Ramirez A, Lobkovsky E, Collum DB. Lithiated Imines: Solvent-Dependent Aggregate Structures and Mechanisms of Alkylation. J Am Chem Soc 2006; 128:5939-48. [PMID: 16637662 DOI: 10.1021/ja060363k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We describe efforts to understand the structure and reactivity of lithiated cyclohexanone N-cyclohexylimine. The lithioimine affords complex solvent-dependent distributions of monomers, dimers, and trimers in a number of ethereal solvents. Careful selection of solvent provides exclusively monosolvated dimers. Rate studies on the C-alkylations reveal chronic mixtures of monomer- and dimer-based pathways. We explore the factors influencing reactants and alkylation transition structures and the marked differences between lithioimines and isostructural lithium dialkylamides with the aid of density functional theory calculations.
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Affiliation(s)
- Stephan J Zuend
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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28
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Solvent effects on the mixed aggregates of chiral 3-aminopyrrolidine lithium amides and alkyllithiums. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.01.095] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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29
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Davies SG, Dupont J, Easton RJ, Ichihara O, McKenna JM, Smith AD, de Sousa JA. Stereoselective conjugate addition reactions of lithium amides to α,β-unsaturated chiral iron acyl complexes [(η5-C5H5)Fe(CO)(PPh3)(COCHCHR)]. J Organomet Chem 2004. [DOI: 10.1016/j.jorganchem.2004.04.046] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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30
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Suzuki M, Koyama H, Noyori R. Effects of HMPA on the Structure and Reactivity of the Lithium Enolate of Cyclopentanone in THF: The Dimer is Responsible for Alkylation and Proton Exchange Reactions. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2004. [DOI: 10.1246/bcsj.77.259] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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7Li- and 31P NMR spectra of cyclopentanone lithium enolate in ethereal solvents: identification of the HMPA-coordinated aggregate structures. Tetrahedron 2004. [DOI: 10.1016/j.tet.2003.12.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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32
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Nassar R, Beatty A, Henderson K. Sodiated β‐Diphosphonate Carbanions: Characterization of the Tetrameric Cubane and the Hexameric Ladder Complexes [{(
i
PrO)
2
P(O)}
2
CHNa]
4
and [{(EtO)
2
P(O)}
2
CHNa]
6. Eur J Inorg Chem 2003. [DOI: 10.1002/ejic.200300258] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Roger Nassar
- University of Notre Dame, Department of Chemistry and Biochemistry 251 Nieuwland Science Hall, Notre Dame, IN 46556‐5670, USA, Fax: (internat.) + 1‐574/631‐6652
| | - Alicia M. Beatty
- University of Notre Dame, Department of Chemistry and Biochemistry 251 Nieuwland Science Hall, Notre Dame, IN 46556‐5670, USA, Fax: (internat.) + 1‐574/631‐6652
| | - Kenneth W. Henderson
- University of Notre Dame, Department of Chemistry and Biochemistry 251 Nieuwland Science Hall, Notre Dame, IN 46556‐5670, USA, Fax: (internat.) + 1‐574/631‐6652
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Mahmoudkhani AH, Rauscher S, Grajales B, Vargas-Baca I. Structural diversity of lithium sulfenamides: 7Li NMR studies in solution and crystal structures of [Li2(eta2-(CH3)3C-NS-C6H4CH(3)-4)2(THF)2] and [Li2(eta1-4-CH3C6H4-NS-C6H4CH(3)-4)2(THF)4]. Inorg Chem 2003; 42:3849-55. [PMID: 12793822 DOI: 10.1021/ic026269w] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Two lithium sulfenamides were prepared by reaction of (CH(3))(3)C-N(H)-S-C(6)H(4)CH(3)-4 (1) and 4-CH(3)C(6)H(4)-N(H)-S-C(6)H(4)CH(3)-4 (2) with an alkyllithium. The unsolvated sulfenamide Li[(CH(3))(3)C-NS-C(6)H(4)CH(3)-4] (3) was soluble enough for variable-temperature (VT) (7)Li NMR to provide evidence of a dynamic exchange of oligomers in solution. The crystal structures of the solvated sulfenamides of [Li(2)(eta(2)-(CH(3))(3)C-NS-C(6)H(4)CH(3)-4)(2)(THF)(2)] (4) and of [Li(2)(eta(1)-4-CH(3)C(6)H(4)-NS-C(6)H(4)CH(3)-4)(2)(THF)(4)] (6) consisted of dimers in which the anions display different hapticities. The VT (7)Li NMR spectra of 4 suggest that the two different structures exist in equilibrium in toluene-THF mixtures. These compounds are easily oxidized to the neutral thioaminyl radicals as identified by EPR spectroscopy.
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Affiliation(s)
- Amir H Mahmoudkhani
- Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada
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Henderson KW, Kennedy AR, MacDougall DJ. Aggregation patterns in alpha,alpha'-stabilized carbanions: assembly of a sodium cage polymer by slip-stacking of dimers. Inorg Chem 2003; 42:2736-41. [PMID: 12691583 DOI: 10.1021/ic026194w] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The alpha,alpha'-stabilized carbanion complexes [PhSO(2)CHCNNa.THF], 3, [t-BuSO(2)CHCNNa], 4, [PhSO(2)CHCNK], 5, [t-BuSO(2)CHCNK], 6, and [MeSO(2)CHCNLi.TMEDA], 7, have been synthesized via the metalation of the parent (organo)sulfonylacetonitriles by BuLi, BuNa, or BnK in THF solution (or THF/TMEDA in the case of 7). In addition, complexes 3 and 7 have been characterized by single-crystal X-ray analyses and have been found to adopt related structures in the solid state. Complex 7 is a molecular dimer containing a central 12-membered (OSCCNLi)(2) ring core, with each metal rendered tetracoordinate by binding to a chelating TMEDA molecule. As found in related complexes, no direct carbanion to lithium contacts are present in the structure of 7. Complex 3 forms a polymeric cage structure composed of associated "dimeric" (OSCCNNa)(2) rings, similar to those found in 7. The larger sodium cations, and the presence of only one THF molecule/metal, allow additional contacts with the anions, leading to hexacoordination at the metal centers. These contacts include long-range transannular Na-N interactions (2.8042(14) A) across the central dimeric ring and "interdimer" Na-C connections (2.8718(15) A). Dissolution of complexes 3-6 and their lithiated derivatives [PhSO(2)CHCNLi.TMEDA], 1, and [t-BuSO(2)CHCNLi.THF], 2, in DMSO-d(6) results in almost identical chemical shifts for each type of ligand. This suggests that charge-separated complexes of the form [RSO(2)CHCN](-)[M(DMSO-d(6))(n)()](+) are formed in highly polar solution.
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Affiliation(s)
- Kenneth W Henderson
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556-5670, USA
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Pratt LM, Streitwieser A. A computational study of lithium enolate mixed aggregates. J Org Chem 2003; 68:2830-8. [PMID: 12662059 DOI: 10.1021/jo026902v] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ab initio calculations were performed to examine the formation of mixed dimer and trimer aggregates between the lithium enolate of acetaldehyde (lithium vinyloxide, LiOV) and lithium chloride, lithium bromide, and lithium amides. Gas-phase calculations showed that in the absence of solvation effects, the mixed trimer 2LiOV.LiX is the most favored species. Solvation in ethereal solvents was modeled by a combination of specific coordination of dimethyl ether ligands on each lithium and "dielectric solvation" (DSE, dielectric solvation energies), immersion of each molecule in a cavity within a continuous dielectric having the dielectric constant of THF at room temperature. DSE is less important for aggregates (reduced dipoles or quadrupoles) than monomers (dipoles) and is also reduced for the coordinatively solvated species. Both solvation terms reduce the exothermicity of aggregation. In many cases, lithium salts that are three- rather than four-coordinate have significant populations at room temperature. The strongly basic lithium amides prefer mixed aggregates with weaker bases than homoaggregates. The computational results are consistent with the limited experimental data available.
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Affiliation(s)
- Lawrence M Pratt
- Department of Chemistry, Fisk University, 1000 17th Avenue North, Nashville, Tennessee 37208, USA.
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Abstract
Multinuclear and multidimensional NMR spectroscopy have shown that lithium (S)-N-isopropyl-O-methyl-valinol (1-[6Li]) exists in a mixed 2:1 complex with nBu[6Li], (1-[6Li])2/nBu[6Li], in non-coordinating solvents such as hexane or toluene. A 6Li,1H-HOESY NMR spectrum indicates that the complex is a cyclic trimer with a large distance between the di-coordinated lithium and the carbanion of nBu[6Li]. Such arrangements are present in the solid state as previously reported by Williard and Sun. The exchange of lithium atoms within the trimer is slow at -33 degrees C. The exchange barrier (deltaG++) was determined to be 14.7 kcal x mol(-1) from quantitative 6Li,6Li-EXSY spectra. Addition of diethyl ether results in the formation of mixed dimers of (1-[6Li])/nBu[6Li], tetramers of nBu[6Li], and homodimers (1-[6Li])2. The apparent equilibrium constant of the mixed dimer was determined from the 6Li NMR integrals as K = 7.
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Affiliation(s)
- G Hilmersson
- Organic Chemistry, Department of Chemistry, Göteborg University, Sweden.
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Rutherford JL, Collum DB. Lithium diisopropylamide: oligomer structures at low ligand concentrations. J Am Chem Soc 2001; 123:199-202. [PMID: 11456504 DOI: 10.1021/ja003104i] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One- and two-dimensional (6)Li and (15)N NMR spectroscopic studies of lithium diisopropylamide (LDA) solvated by substoichiometric concentrations of oxetane, THF, Et(2)O, and diisopropylamine are described. Partially solvated dimers and trimers are identified. Possible benefits of carrying out organolithium chemistry at low ligand concentrations are discussed.
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Affiliation(s)
- J L Rutherford
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
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