Journal article
Highly enantioselective (-)-sparteine-mediated lateral metalation-functionalization of remote silyl protected ortho-ethyl N,N-dialkyl aryl O-carbamates.
- Fässler J †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- McCubbin JA †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- Roglans A †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- Kimachi T †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- Hollett JW ‡Department of Chemistry, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada.
- Kunz RW #Institute of Organic Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland.
- Tinkl M †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- Zhang Y †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- Wang R †Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
- Campbell M ⊥Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, Ontario P7B 6V4, Canada.
- Snieckus V ∥Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.
- 2014-12-19
Published in:
- The Journal of organic chemistry. - 2015
Carbamates
Crystallography, X-Ray
Lithium Compounds
Molecular Structure
Silanes
Sparteine
Stereoisomerism
English
We report the enantioselective, lateral deprotonation of ortho-protected or functionalized tertiary N,N-dialkyl aryl O-carbamates 5-7 (Scheme 2 ) and meta-protected carbamates 14, 15, and 20 (Schemes 5 and 7 ) by s-BuLi/(-)-sparteine and subsequent quench with a variety of electrophiles to give products 11-13 and 16, 17, and 21 in yields up to 96% and enantiomeric ratios up to 99:1. The influence of organolithium reagents, ratio of organolithium/(-)-sparteine pair versus N,N-dialkyl aryl O-carbamate starting materials, temperature, solvents, electrophiles, substituents located ortho or meta to the O-carbamate moiety, and O-carbamate N-substituents was investigated. The identical absolute configuration of the stereogenic center of the major enantiomers of the products, as established by single-crystal X-ray analysis for substrates (S)-11c, (S)-19, and (S)-21a, provides evidence for a consistent stereochemical course in the enantioselective deprotonation. Mechanistic investigations, including an estimate of the configurational stability of the benzyllithium species 9 (starting from 12e; Scheme 8 ) and 23 (starting from 17e; Scheme 9 ), both derived by tin-lithium exchange, and 24 (starting from 20; Scheme 9 ) are reported. The experimental results, together with semiempirical molecular orbital calculations (PM3/SMD), are consistent with a process in which enantioinduction occurs in the deprotonation step (Scheme 11 ).
- Language
-
- English
- Open access status
- closed
- Identifiers
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- DOI 10.1021/jo502561m
- PMID 25521308
- Persistent URL
- https://sonar.ch/global/documents/19208
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