Extrusion of dinitrogen from enol diazoacetates with a RhII catalyst generates metal enolcarbenes. 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.