Fragmentation vs rearrangement of the amide and thioester groups in 4,4-disubstituted cyclohexadienones

Abstract

Migration of electron-withdrawing substituents in carbocations normally occurs in preference to other common substituents that are normally very good migrating groups, if the electronwithdrawing group contains a π bond. This study represents the first investigation of the amide (diethylamido) and thioester (thiocarbethoxy) substituents in the dienone-phenol rearrangement reaction. In aqueous acid, the dienones 6b and 6c were found to fragment instead of to undergo rearrangement. A mechanistic rationalization is given.