Screening of chiral phosphines as catalysts for the enantioselective [3+2] annulations of N-tosylimines with allenic esters
摘要:
The use of chiral, binaphthyl-based phosphepines as catalysts improves previous results for the enantioselective [3+2] cyclisation reactions between allenic esters and N-tosylimines, both in terms of conversion rate and enantioselectivity. Pyrrolines bearing 1-naphthyl, phenyl, o-tolyl and p-MeO-phenyl substituents on the stereogenic alpha-carbon have been obtained with enantiomeric excesses up to 64-80%. (c) 2007 Elsevier Ltd. All rights reserved.
The use of chiral, binaphthyl-based phosphepines as catalysts improves previous results for the enantioselective [3+2] cyclisation reactions between allenic esters and N-tosylimines, both in terms of conversion rate and enantioselectivity. Pyrrolines bearing 1-naphthyl, phenyl, o-tolyl and p-MeO-phenyl substituents on the stereogenic alpha-carbon have been obtained with enantiomeric excesses up to 64-80%. (c) 2007 Elsevier Ltd. All rights reserved.
Enantioselective Binaphthophosphepine-Promoted [3+2] Annulations of N-Ts- and N-DPP-Imines with Allenoates and 2-Butynoates
The use of binaphthophosphepine 1a as a catalyst for the [3+2] cyclisation between allenoates or 2-butynoates andimines was investigated. The effects of the imine protecting group on both the catalytic activity and enantioselectivity were determined by comparing the behaviour of N-tosyl- and N-DPP-imines. The N-DPP-imines displayed lower reactivity, but afforded the desired pyrrolines in higher enantiomeric