One-Pot Metal-Free Synthesis of Diarylamines from Aromatic Aldehydes and Anilines

A novel and environmentally friendly method has been developed for the synthesis of a broad range of diarylamines from inexpensive and readily available starting materials, such as aromatic aldehydes and amines. The process follows a one-pot strategy in which imine formation is succeeded by an oxidative rearrangement analogous to the Meinwald reaction and concludes with a light-induced deformylation step. This efficient transformation proceeds in a single vessel with a high atom economy under mild, metal-free conditions. The methodology was further demonstrated as a key step in the synthesis of phentolamine, a reversible, nonselective α-adrenergic blocker used in the treatment of hypertensive emergencies.