Synthesis of Quinolizidine-Based 1,4-Azaphosphinines via Cyclization of Heteroarylmethyl(alkynyl)phosphinates.

Intramolecular hydroarylation of (phenylethynyl)phosphinates represents a powerful strategy for constructing six-membered phosphorus heterocycles. In this study, we report a silver-catalyzed cyclization protocol that enables the efficient synthesis of 1,4-aza-phosphorus heterocycles under mild conditions. The approach demonstrates broad substrate tolerance, affording full conversion across more than 30 derivatives. Dearomatization of pyridine leads to the formation of previously unreported quinolizidine-based 1,4-azaphosphinine scaffolds. These novel phosphorus heterocycles expand the structural diversity of phosphorus-containing frameworks and open new opportunities in the chemistry of functional heterocycles.