A facile and practical removal of 2-oxazolidinone and 2-hydroxyethylamine auxiliaries was accomplished by treating the corresponding N-acyl-2-oxazolidin one and N-(2-hydroxyethyl)amide derivatives in simple methoxide-carbonate systems. The presence of excess DMC (dimethyl carbonate) accelerates the N-acyl bond cleavage for those substrates under mild reaction conditions, and the present method was found to be useful especially for the synthesis of planar-chiral nicotinate. (C) 2003 Elsevier Science Ltd. All rights reserved.
Hammett Studies of Enantiocontrol by PHOX Ligands in Pd-Catalyzed Allylic Substitution Reactions
作者:Ryan N. Constantine、Naomi Kim、Richard C. Bunt
DOI:10.1021/ol034610q
日期:2003.6.1
Electronically modified PHOX ligands 3a-e were synthesized to probe the mechanism of the enantioselective palladium-catalyzed allylicalkylation and amination reactions. Alkylation with dimethyl sodiomalonate produced only a small variation in the ee (89.3% to 93.4%), but amination with benzylamine gave a much wider variation in the ee (16.4% to 66.6%). Hammett analysis suggests that the substituents