Chemoselective Cyclodehydration of α‐Acyl‐β‐arylaminoacrylamides Using Hendrickson Reagent: Access to Polysubstituted 4‐Aminoquinolines and Diazaphenacenes

A chemoselecive cyclodehydration of alpha-acyl-beta-arylaminoacrylamides via an electrophilic activation strategy has been described. A series of substituted 4-aminopyridines are chemoselectively prepared in 73-92% yields from alpha-acyl-beta-arylaminoacrylamides activated by hexaphenyloxodiphosphonium triflate (Hendrickson reagent), whereas substituted diaza[n]phenacenes (n=4-6) are obtained in 72-93% yields directly from alpha-acyl-beta-arylaminoacrylamides using Hendrickson reagent in combination with triflic anhydride (Tf2O). The synthetic protocols feature with readily available starting materials, mild reaction conditions, simple execution, and wide range of synthetic potential of products.