ABSTRACT The A 3 ‐coupling reaction, which involves aldehydes, amines, and terminal alkynes to synthesize propargylamines, is a versatile method in organic synthesis but is often plagued by Glaser coupling as an undesired side reaction, leading to a diyne byproduct. In this study, we report an optimized copper(I)‐catalyzed photoredox A 3 ‐coupling protocol that employs p ‐toluenesulfonic acid (PTSA) as an additive to effectively suppress the Glaser coupling product. Utilizing CuI (10 mol%) as the catalyst, acetonitrile as the solvent, and a nitrogen atmosphere, the reaction achieves high selectivity and yields (84%–92%) of propargylamines with a trace amount of diyne. The photoredox system enhances copper (Cu)‐mediated alkyne activation under mild conditions, while PTSA stabilizes the reaction environment by promoting iminium ion formation and preventing oxidative homocoupling. This optimized protocol offers a robust, scalable, and efficient approach for synthesizing propargylamines.
Ayyavoo et al. (Sun,) studied this question.