Synergistic Cesium Carbonate-Promoted Dehydration of Ketonitrones: Stereoselective Synthesis of Indenyl-2-azadienes

Abstract

A strategy for N-O bond cleavage of ketonitrones promoted by cesium carbonate has been developed, enabling access to indenyl-2-azadienes via a dehydration process. Both cyclic indanone-derived nitrones and acyclic ketonitrones underwent dehydration in the Cs2CO3/toluene system to afford 2-azadienes in high yields with excellent selectivity. Control experiments indicated that the synergistic cesium ion-directed deprotonation of the α-hydrogen of the ketonitrone to generate a carbanion intermediate is the key step in the dehydration process. Moreover, 1-aminoindane, a privileged scaffold present in numerous pharmaceutical agents, is readily accessible through the selective reduction of 2-azadiene.