Aminoalkylation of alkynyl bromides for accessing propargylamines via visible-light-driven multicomponent reaction

Propargylamines are an important class of organic motifs that exist in a myriad of biologically active molecules. In this paper, we present a new approach for synthesising propargylamines, which utilises a reductive photocatalytic protocol to enable the three-component coupling of alkynyl bromides with feedstock secondary alkylamines and aldehydes. A wide range of highly functionalized propargylamines (44 examples) can be furnished in 29-75 % yields at room temperature. Both aliphatic aldehydes and aromatic aldehydes are compatible with this aminoalkylation reaction. Mechanistic studies indicate that the reactions involve the in situ -generation of iminium ions, subsequently leading to the production of α -amino radicals via single electron transfer. These radicals then undergo addition to alkynyl bromides, followed by a β -elimination cascade.