Highly Chemoselective Synthesis of 4-Aminocinnolines via Electrophilic Activation Strategy

Chemoselective cyclodehydration of α-arylhydrazonoamides via an electrophilic activation strategy has been described. A series of polysubstituted 4-aminocinnolines are chemoselectively synthesized in 67-90% yields from α-arylhydrazono-β-oxoamides in the presence of hexaphenyloxodiphosphonium triflate (Hendrickson reagent) and triflic anhydride (Tf2O) at room temperature, whereas several substituted quinolino [3,2-c]cinnolines are obtained in 64-77% yields under reflux. The readily available starting materials, mild conditions, good yields and high chemoselectivity make this novel synthetic protocol much attractive and practical.