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Delany PK, Mortimer CL, Hodgson DM. Electrophile dependent mechanisms in the asymmetric trapping of α-lithio- N-( tert-butoxythiocarbonyl)azetidine. Chem Commun (Camb) 2020; 56:12174-12177. [PMID: 32910117 DOI: 10.1039/d0cc05396a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sn-Li exchange and 'poor man's Hoffmann tests' establish asymmetric trapping of α-lithio-N-(tert-butoxythiocarbonyl) (Botc) azetidine to be controlled by dynamic thermodynamic resolution or dynamic kinetic resolution, depending on the electrophile. Unusually, different configurational stability is seen for the anion generated by lithiation compared to transmetallation. Configurational stability of α-lithio-N-Boc azetidine indicates instability with the N-Botc system is due to the C[double bond, length as m-dash]S group.
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Affiliation(s)
- Pascal K Delany
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
| | - Claire L Mortimer
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
| | - David M Hodgson
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
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2
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Fournier AM, Nichols CJ, Vincent MA, Hillier IH, Clayden J. Lithium Choreography: Intramolecular Arylations of Carbamate-Stabilised Carbanions and Their Mechanisms Probed by In Situ IR Spectroscopy and DFT Calculations. Chemistry 2012; 18:16478-90. [DOI: 10.1002/chem.201201761] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 08/29/2012] [Indexed: 11/10/2022]
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3
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Sakakura A, Yamada H, Ishihara K. α-Heterosubstituted β-Alkylacroleins as Useful Multisubstituted Dienophiles for Enantioselective Diels-Alder Reactions. ASIAN J ORG CHEM 2012. [DOI: 10.1002/ajoc.201200054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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4
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Page A, Clayden J. Carbamate-directed benzylic lithiation for the diastereo- and enantioselective synthesis of diaryl ether atropisomers. Beilstein J Org Chem 2011; 7:1327-33. [PMID: 22043243 PMCID: PMC3201046 DOI: 10.3762/bjoc.7.156] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Accepted: 08/24/2011] [Indexed: 11/23/2022] Open
Abstract
Diaryl ethers carrying carbamoyloxymethyl groups may be desymmetrised enantio- and diastereoselectively by the use of the sec-BuLi–(−)-sparteine complex in diethyl ether. Enantioselective deprotonation of one of the two benzylic positions leads to atropisomeric products with ca. 80:20 e.r.; an electrophilic quench typically provides functionalised atropisomeric diastereoisomers in up to 97:3 d.r.
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Affiliation(s)
- Abigail Page
- School of Chemistry, University of Manchester, Oxford Rd., Manchester M13 9PL, UK
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5
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Aggarwal VK, Binanzer M, de Ceglie MC, Gallanti M, Glasspoole BW, Kendrick SJF, Sonawane RP, Vázquez-Romero A, Webster MP. Asymmetric synthesis of tertiary and quaternary allyl- and crotylsilanes via the borylation of lithiated carbamates. Org Lett 2011; 13:1490-3. [PMID: 21332157 DOI: 10.1021/ol200177f] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tertiary allyl- or crotylsilanes have been prepared in high er and dr via the lithiation-borylation reaction of alkyl carbamates with silaboronates. Using a related strategy, quaternary allylsilanes could be accessed in similarly high er.
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Affiliation(s)
- Varinder K Aggarwal
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.
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6
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Hémery T, Huenerbein R, Fröhlich R, Grimme S, Hoppe D. Configurationally labile enantioenriched lithiated 3-arylprop-2-enyl carbamates: joint experimental and quantum chemical investigations on the equilibrium of epimers. J Org Chem 2010; 75:5716-20. [PMID: 20666439 DOI: 10.1021/jo101218z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Experimental investigations as well as high-level quantum chemical calculations are performed on the two epimeric pairs of complexes 4.2 and 6.2 obtained by lithiation of cinnamyl carbamate (1) and 1-naphthyl derivative 5 in the presence of BOX ligands (S,S)- and (R,R)-2. Indeed, in the case of configurationally labile complexes and a dynamic thermodynamic resolution, which is found to take place, one of both epimers is energetically favored. The quantum chemical computations allow the prediction of the enantiomeric excess that can be expected.
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Affiliation(s)
- Thérèse Hémery
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Germany
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7
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Hémery T, Becker J, Fröhlich R, Hoppe D. (-)-Myrtenyl N,N-Diisopropylcarbamate: Stereochemistry of Lithiation and Electrophilic Substitution Directed by Dynamic Kinetic Diastereoisomer Resolution. European J Org Chem 2010. [DOI: 10.1002/ejoc.201000390] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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8
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9
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Kizirian J. Mechanism and Stereochemical Features in Asymmetric Deprotonation Using RLi/(–)‐Sparteine Bases. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/9783906390628.ch6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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10
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Genet C, McGrath MJ, O'Brien P. Evaluation of sparteine-like chiral diamines in the enantioselective lithiation–electrophilic trapping of an O-alkyl carbamate. Org Biomol Chem 2006. [DOI: 10.1039/b600032k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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11
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Brandau S, Hoppe D. Asymmetric synthesis of (2-carbamoyloxy-1-alkenyl)cyclopropanes by intramolecular cycloalkylation. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.09.110] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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12
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McGrath MJ, O'Brien P. Catalytic Asymmetric Deprotonation Using a Ligand Exchange Approach. J Am Chem Soc 2005; 127:16378-9. [PMID: 16305208 DOI: 10.1021/ja056026d] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel ligand exchange approach to catalytic asymmetric deprotonation-electrophilic trapping has been developed that uses 1.3 equiv of s-BuLi, 0.06-0.2 equiv of chiral diamine ((-)-sparteine or a (+)-sparteine surrogate), and 1.2 equiv of achiral bispidine. The methodology is illustrated with a range of examples and gives access to either enantiomer of useful chiral products in good yields using substoichiometric amounts of chiral diamines.
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Affiliation(s)
- Matthew J McGrath
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
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Zeng W, Fröhlich R, Hoppe D. Enantioselective, (−)-sparteine-mediated deprotonation of geranyl and neryl N,N-diisopropylcarbamate: configurational stability of the intermediate lithium compounds. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.01.100] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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14
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Coldham I, Dufour S, Haxell TF, Vennall GP. Dynamic resolution of N-alkyl-2-lithiopyrrolidines with the chiral ligand (−)-sparteine. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.01.096] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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15
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Wang L, Nakamura S, Ito Y, Toru T. Enantioselective reaction of α-lithiated thiazolidines as new chiral formyl anion equivalents. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.tetasy.2004.08.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Marr F, Fröhlich R, Hoppe D. Preparation of meso-1,3-diphenylallyllithium·(−)-sparteine—its crystal structure and reactions. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0957-4166(02)00660-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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17
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Basu A, Thayumanavan S. Konfigurative Stabilität und Stereoinformationstransfer in Reaktionen Enantiomeren-angereicherter Organolithium-Reagentien. Angew Chem Int Ed Engl 2002. [DOI: 10.1002/1521-3757(20020301)114:5<740::aid-ange740>3.0.co;2-r] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Pippel DJ, Weisenburger GA, Faibish NC, Beak P. Kinetics and mechanism of the (-)-sparteine-mediated deprotonation of (E)-N-Boc-N-(p-methoxyphenyl)-3-cyclohexylallylamine. J Am Chem Soc 2001; 123:4919-27. [PMID: 11457318 DOI: 10.1021/ja001955k] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The (-)-sparteine-mediated asymmetric lithiation-substitution of (E)-N-Boc-N-(p-methoxyphenyl)-3-cyclohexylallylamine ((E)-5) to afford gamma-substituted enantiomerically enriched products 6 is reported. The solution structure for the lithiated intermediate 8.1 in these reactions was determined by heteronuclear NMR to be a configurationally stable, alpha-lithio, eta(1)-coordinated monomer. This intermediate is proposed to exist as two rotamers that are rapidly equilibrating on the NMR time scale; competitive electrophilic substitution of each conformation results in the formation of Z or E products. Kinetic measurements of the lithiation by in situ infrared spectroscopy provide pseudo-first-order rate constants for reactions with a variety of concentrations of amine, (-)-sparteine, and n-BuLi. The reaction is first order in amine and zero order in 1:1 base--ligand complex. When the concentration of n-BuLi is varied independently of (-)-sparteine concentration, the reaction rate exhibits an inverse dependence on n-BuLi concentration. The deuterium isotope effect for the reaction was determined to be 86 at -75 degrees C, a result consistent with C--H bond breaking in the rate-determining step and indicative of tunneling. A reaction pathway involving a prelithiation complex is supported by kinetic simulations.
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Affiliation(s)
- D J Pippel
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Schultz-Fademrecht C, Wibbeling B, Fröhlich R, Hoppe D. Synthesis of Enantiomerically Enriched Allenes by (−)-Sparteine-Mediated Lithiation of Alkynyl Carbamates. Org Lett 2001; 3:1221-4. [PMID: 11348199 DOI: 10.1021/ol0157104] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[reaction: see text]. The alpha-deprotonation of alkynyl carbamates 3 with the chiral base (-)-sparteine (4)/n-butyllithium, transmetalation with ClTi(O(i)()Pr)3, and subsequent substitution with an aldehyde results in the formation of enantioenriched 4-hydroxyallenyl carbamates 11. Stereoselection is determined by dynamic resolution of the lithium/(-)-sparteine complexes by selective crystallization.
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Affiliation(s)
- C Schultz-Fademrecht
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany
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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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