Study on the stereoselective construction of furans with an asymmetric quaternary center at the 2-position

Abstract

During our examination on the generality of the asymmetric Michael reaction using a chiral piperazine, we found that furans bearing a quaternary carbon center at the 2-position could be constructed just by mixing 2-oxo-cyclopentanecarboxylic acid benzyl ester and (Z)-4-oxo-pent-2-enal in the presence of weak Bronsted acids such as HFIP and carboxylic acids . Since the reaction proceeded under mild conditions, the diastereoselective furan formation reaction was examined by using B-ketoesters bearing chiral auxiliaries. As a result, it was found that high diastereoselectivity could be achieved by using 8-phenylmenthol as the chiral auxiliary with selectivity as high as 96% de. Determination of the stereochemistry of the major diastereomer and the examination of the generality of this diastereoselective reaction are currently underway.