Nazarov Reaction of Trisubstituted Dienones: Mechanism Involving Wagner-Meerwein Shift

Article abstract of DOI:10.1021/jo00002a047

The Nazarov reactions of trisubstituted α,α'-dienones were studied.Whereas α,β-dimethyl-β'-alkyl α,α'-dienones gave 2,3-dimethyl-4-alkyl-2-cyclopentenones when heated in concentrated sulfuric acid, the reaction of β,β-dimethyl-β'-alkyl α,α'-dienones afforded 3,4-dimethyl-4-alkyl-2-cyclopentenones as the rearranged products.A mechanistic investigation using two deuterated dienones suggests that the Nazarov reactions of the latter dienones are accompanied by Wagner-Meerwein shifts to form the most stable carbocations.