Journal
CHINESE JOURNAL OF ORGANIC CHEMISTRY
Volume 34, Issue 1, Pages 107-111Publisher
SCIENCE PRESS
DOI: 10.6023/cjoc201310053
Keywords
N-H insertion; chiral sulfonamide urea; ammonium ylide; co-catalysts; alpha-amino acid derivatives
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Funding
- National Natural Science Foundation of China [21125209]
- Science and Technology Commission of Shanghai Municipality [12JC1403800]
- Minhang District Government in Shanghai
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The enantioselective N-H insertion of alpha-diazoesters and carbamates provides a potentially attractive approach to alpha-amino acid derivatives. Herein, a novel cooperative catalytic system of achiral dirhodium(II) acetates, chiral sulfonamide urea and achiral sulfonic acid was developed for asymmetric N-H insertion reactions. Prochiral ammonium ylide intermediates, generated in situ from alpha-diazoesters and carbamates initiated by dirhodium(II) acetate, underwent asymmetric protonation with a considerable enantioselectivity in the presence of chiral sulfonamide urea and achiral sulfonic acid as co-catalysts. The co-catalysts of chiral sulfonamide urea and achiral sulfonic acid were considered as a chiral proton shuttle assisting the asymmetric proton transfer process to control the enantioselectivity. This methodology provides an efficient and mild approach to a-amino acid derivatives in high yields (up to 84% yield) with moderate enantioselectivity (up to 77% ee).
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