Driving Recursive Dehydration by P(III)/P(V) Catalysis: Annulation of Amines and Carboxylic Acids by Sequential C–N and C–C Bond Formation

[Image: see text] A method for the annulation of amines and carboxylic acids to form pharmaceutically relevant azaheterocycles via organophosphorus P(III)/P(V) redox catalysis is reported. The method employs a phosphetane catalyst together with a mild bromenium oxidant and terminal hydrosilane reductant to drive successive C–N and C–C bond-forming dehydration events via the serial action of a catalytic bromophosphonium intermediate. These results demonstrate the capacity of P(III)/P(V) redox catalysis to enable iterative redox-neutral transformations in complement to the common reductive driving force of the P(III)/P(V) couple.