Three‐Component Synthesis of Substituted Azepines by Gold/Magnesium Orthogonal‐Relay Catalysis

A three‐component one‐pot synthesis of substituted azepines was realized by gold/magnesium orthogonal relay catalysis. The one‐pot synthesis involves simply mixing and heating propiolates, imines, and activated cyclopropanes to initiate a gold‐catalyzed aza‐enyne metathesis between propiolates and imines, followed by a magnesium‐catalyzed [4+3] cycloaddition reaction of the resultant 1‐azabutadienes and cyclopropanes, yielding substituted azepines. The corresponding substituted azepines including 22 derivatives could be successfully prepared in good to excellent yield (61–95%). The reaction could be conducted in one‐gram scale.