The Question of Electrophilic vs Nucleophilic Addition of Cyclic β-Dicarbonyl Phenyliodonium Ylides: Electrophilic Cycloaddition of Diphenylketene

The reaction of beta-dicarbonyl phenyliodonium ylides with diphenylketene at room temperature affords mixtures of lactone and aurone derivatives. The initial electrophilic attack of the iodonium ylide on the C-beta position of the diphenylketene, followed by cyclization of the zwitterionic species, and subsequent ejection of iodobenzene, affords the lactone and aurone cycloadducts. Treatment of beta-dicarbonyl iodonium ylides with acyl chlorides yields alpha-chloroenones with good to excellent yields.