N ‐Acyl‐ N ‐tosylhydrazine as a Synthon To Construct Tetrasubstituted Carbon Centers Possessing a Nitrogen Group

New halohydrazidation and hydrazidopalladation reactions were developed that use the synthon N ‐acyl‐ N ‐tosylhydrazine. The intramolecular bromohydrazidation reactions of β,γ‐unsaturated N ‐acyl‐ N ‐tosylhydrazines readily afforded pyrazolidinone ring systems that contained a tetrasubstituted carbon center, and the primary amine of the N ‐acyl‐ N ‐tosylhydrazine was shown to be a soft nucleophile. The similar bromohydrazidation reaction of γ,δ‐unsaturated N ‐acyl‐ N ‐tosylhydrazine resulted in O‐cyclization to give a lactone ring instead of N‐cyclization to give a hydropyridazine ring system; however, the intramolecular hydrazidopalladation reaction predominantly afforded a hydropyridazine ring. The established catalytic hydrazidopalladation reaction was applicable to several multisubstituted alkenes to construct a tetrasubstituted carbon center possessing a nitrogen group.