Rhodium(II)-Catalyzed Reaction of Iodonium Ylides with Conjugated Compounds: Efficient Synthesis of Dihydrofurans, Oxazoles, and Dihydrooxepines

The rhodium(II)-catalyzed reaction of iodonium ylides with a variety of conjugated compounds has been examined. With α,β-unsaturated esters and α,β-unsaturated ketones, dihydrofurans were produced in moderate yields. Reactions with acrylonitriles yield oxazoles and dihydrofurans in moderate yields, whereas reactions with 1,3-butadienes result in dihydrofurans and dihydrooxepines in good yields, respectively. The mechanistic pathway for the formation of these products has been described in terms of a cyclopropane intermediate or a 1,3-dipolar cycloaddition mechanism.