Rh-Catalyzed Formation of Dioxolanes from α-Alkyl Diazoesters: Diastereoselective Cycloadditions of Carbonyl Ylides with Selectivity over β-Hydride Elimination

Described here is a diastereoselective Rh-catalyzed method for the preparation of dioxolanes from α-alkyl-α-diazoesters. This represents the first general method for generating carbonyl ylides from α-diazoesters that possess β-hydrogens, as such diazo compounds typically give rise to alkenes via β-hydride elimination. Subsequent cycloaddition with aromatic aldehydes gives tetrasubstituted dioxolanes with unusually high diastereoselectivity. A model is set forth to explain the diastereoselectivity of the cycloaddition.