CN bond formation via palladium-catalyzed carbene insertion into NN bonds: inhibiting the general 1,2-migration process of ylide intermediates

A new example of CN double bond formation in metal carbene insertion reactions is reported. Remarkably, the general 1,2-migration process of the corresponding ylide intermediates in X–H carbene insertion reactions that leads to C–X single bond formation is completely inhibited by replacing the H atom with a nitrogen atom. This palladium-catalyzed carbene insertion reaction with NN double bonds gave various N,N-disubstituted hydrazone products in high yields.