Process for the Synthesis of 3-spiropiperidino Indolenines

The invention is related to the synthesis of 3-Spiropiperidino Indolenines, more particularly it relates to process for the synthesis of 3-spiropiperidino indolenines from activated aziridines. 3-Spiropiperidino indolenine is a privileged heterocyclic scaffold with exceptional pharmaceutical significance. It constitutes structural cores of several naturally-occurring alkaloids with valuable biological activities. 3-Spiropiperidino indolenine derivatives have been used as a calcitonin gene-related peptide (CGRP) receptor antagonist for headache therapy,1 and as 11β-hydroxysteroid dehydrogenase type-1 enzyme inhibitors that are useful in the treatment and prophylaxis of obesity and diabetes. We have invented a practical synthetic route to a wide range of 3-spiropiperidino indolenines possessing an exocyclic olefinic moiety at the 2-position of the piperidine ring via one-pot Lewis acid catalyzed SN2-type ring opening of activated aziridines with 2-substituted 1H-indoles followed by Pd-catalyzed spirocyclization with propargyl carbonates.