Enantioselective Synthesis of Quaternary Δ4 - and Δ5 -Dehydroprolines Based on a Two-Step Formal [3+2] Cycloaddition of α-Aryl and α-Alkyl Isocyano(thio)acetates with Vinyl Ketones.

Enantioselective Synthesis of Quaternary Δ4 - and Δ5 -Dehydroprolines Based on a Two-Step Formal [3+2] Cycloaddition of α-Aryl and α-Alkyl Isocyano(thio)acetates with Vinyl Ketones.