Highly Enantioselective Dearomatizing Formal [3+3] Cycloaddition Reactions of N‐Acyliminopyridinium Ylides with Electrophilic Enol Carbene Intermediates

Extrusion of dinitrogen from enol diazoacetates with a RhII catalyst generates metal enol carbenes. Subsequent vinylogous addition of these to N-acyliminopyridinium ylides results in an effective formal [3+3] cycloaddition to give highly substituted 1,2,3,6-tetrahydropyridazines in up to 98 % ee and high yield.