Cycloaddition of Spiroepoxycyclohexa-2,4-dienones, Radical Cyclization and 1,3-Acyl Shift in Excited State: Aromatics to Sterpuren-4-one

A stereoselective
route to sterpuren-4-one from a simple aromatic
precursor is presented. Oxidative dearomatization, π4s + π2s cycloaddition of 6,6-spiroepoxycyclohexa-2,4-dienones
with ethyl acrylate, radical cyclization and 1,3-acyl shift in excited
state are the important aspects of our approach. An interesting effect
of a remote substituent on radical cyclization has also been presented.