X=Y-ZH systems as potential 1,3-dipoles. Part 55: Cascade 1,3-azaprotio cyclotransfer-cycloaddition reactions between ketoximes and divinyl ketone

The cascade 1,3-azaprotio cyclotransfer-1,3-dipolar cycloaddition reaction between ketoximes and divinyl ketone [or its equivalent bis(2-chloroethyl) ketone] affords high yields of substituted 1-aza-7-oxabicyclo[3.2.1]octan-4-ones and 1-aza-8-oxabicyclo[3.2.1]octan-4-ones where the cycloaddition regioselectivity is controlled by a judicious choice of experimental conditions, The N-O bonds in the products are reductively cleaved to form piperidones and perhydroazepinones and the ketone moiety undergoes stereoselective sodium cyanoborohydride reduction to afford anti-1-aza-7-oxa-4-hydroxybicyclo[3.2.1]octanes and ariti-1-aza-8-oxa-4-hydroxybicyclo[3.2.1]octanes. (C) 2002 Elsevier Science Ltd. All rights reserved.