A general synthetic access to 3,3-disubstituted 1,4-diynes bearing a quaternary carbon center from acetylacetone was developed. The compounds were cyclized to the corresponding enol ethers by cationic gold complexes. The reactions occur in complete exo-selectivity in contrast to compounds incorporating an alkoxy substituent in the 3-position. A mechanistic rationale for this reversal of selectivity is provided.
Anion-Induced Enantioselective Cyclization of Diynamides to Pyrrolidines Catalyzed by Cationic Gold Complexes
作者:Asmaa Kamal Mourad、Juliane Leutzow、Constantin Czekelius
DOI:10.1002/anie.201205416
日期:2012.10.29
Only chiral anions do the job! Optically active goldcomplexes derived from substituted binol hydrogen phosphate catalyze the desymmetrizing cyclization of 1,4‐diynamides. This reaction provides access to synthetically useful, chiral methylene pyrrolidines with an all‐carbon‐substituted quaternary stereocenter.