Multicomponent Domino Synthesis of Spiro Framework under Ultrasonic Irradiation

This work describes an easy synthetic methodology to create a 25 member library of hexahydrospiro[indoline-3.3'-pyrrolizine]-2-one derivatives under ultrasonic irradiation. Spiro compounds were synthesized through a three-component reaction of isatin, L-praline, and chalcone analogs. The target compounds were formed in a regioselective approach with predominant formation, only one regioisomer. The probable reason behind regioselectivity was also explained with the help of orbital symmetry control. The formation of secondary orbital interaction in the transition state leads to the formation of a favorable transition state which predominantly forms the selective regioisomer.