Metal-free POCl3 promoted stereoselective hydrochlorination of ethynylated azaheterocycles

Abstract

An efficient hydrochlorination of ethynylated azaheterocycles was achieved using POCl₃ as a chlorinating agent under metal-free reaction conditions. Mechanistic studies show that the reaction proceeded via nucleophilic attack of POCl₃ on the nitrogen of the quinoline ring in a stereoselective manner. The resulting products were versatile intermediates in organic synthesis and were used in the cross-coupling reaction and metal-free synthesis of heterocycles. The developed protocol features inexpensive and easily synthesizable starting materials, easy operation, and high efficiency with a high yield of products.