Chiral silver phosphate catalyzed transformation of ortho-alkynylaryl ketones into 1H-isochromene derivatives through an intramolecular-cyclization/ enantioselective-reduction sequence

Abstract

The transformation of ortho-alkynylaryl ketones through a cyclization/enantioselective-reduction sequence in the presence of a chiral silver phosphate catalyst afforded 1H-isochromene derivatives in high yield with fairly good to high enantioselectivity. An asymmetric synthesis of the 9-oxabicyclo[3.3.1]nona-2,6-diene framework, which has been found in some biologically active molecules, is presented as a demonstration of the synthetic utility of this method. Dependent on its other half: The title reaction of ortho-alkynylaryl ketones in the presence of a silver catalyst with a chiral counteranion afforded 1H-isochromene derivatives in high yield with good to high enantioselectivity (see scheme; R1=alkyl, aryl; R2=aryl; R3=H, F). An asymmetric synthesis of the 9-oxabicyclo[3.3.1]nona-2,6- diene framework found in biologically active molecules highlights the synthetic utility of this method. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.