Asymmetric Synthesis of 1,3-Dioxolanes by Organocatalytic Formal [3 + 2] Cycloaddition via Hemiacetal Intermediates

A novel asymmetric formal [3 + 2] cycloaddition reaction for the synthesis of 1,3-dioxolanes using cinchona-alkaloid-thiourea-based bifunctional organocatalysts is reported. The reaction proceeds via the formation of hemiacetal intermediates between γ-hydroxy-α,β-unsaturated ketones and aldehydes.