Simple protocol for enhanced (E)-selectivity in Julia–Kocienski reaction
摘要:
A short and efficient Julia-Kocienski olefination protocol, based upon the use of chelating agents (18-crown-6 or TDA-1 for K(+); 12-crown-4 or HMPA for Li(+)), was developed. This protocol enhances the (E)selectivity of the reaction and the desired olefins are obtained generally with >10:1 (E/Z)-selectivity. (C) 2011 Elsevier Ltd. All rights reserved.
Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.