Formation of ylidenehydrazines enabled by manganese-catalyzed acceptorless dehydrogenative coupling

Abstract

Catalytic dehydrogenation, which exhibits highly atom-economical and chemo-selective properties, converts multiple green sustainable alcohols to critical molecules and is a highly desirable and elusive process; furthermore, the dehydrogenation of alcohols with hydrazines produces ylidenehydrazines, which are versatile building blocks in the formation of numerous pharmaceuticals. However, the syntheses of functionalized ylidenehydrazines involve multi-step reactions that require harsh conditions. Herein, we report a practical one-pot catalytic tandem dehydrogenative condensation coupling of hydrazines with alcohols and halides to form ylidenehydrazines via an acceptorless dehydrogenative coupling strategy, overcoming the challenge of selectivity in multicomponent reactions. The system is based on the Earth-abundant metal Mn, which is stabilized by a novel bench-stable PNN pincer ligand derived from aminoindazole. A large series of functionalized ylidenehydrazines is obtained in high yields with excellent selectivities, and gram-scale ylidenehydrazines are prepared using this protocol. Notably, using this protocol, several pharmaceuticals may be easily synthesized in a one-pot manner. This strategy significantly broadens the scope of Mn-catalyzed dehydrogenative condensation coupling for synthesizing unsaturated molecules.