A Simple and Advantageous Synthesis of the Privileged 1,4-Benzodiazepine Nucleus

Abstract

A novel domino approach has been described for an easy access of the privileged nucleus of 5-carbomethoxy substituted 1,4-benzodiazepin-2-ones 4(a–i) from an in situ methanolic hydrolysis of an incipient species formed from the interaction of 1-chloroacetylisatin 2(a–i), hexamethyldisilazane, and n-butyl lithium. The reaction is believed to take place through a consecutive series of intramolecular reactions in a cascade to first generate a highly reactive carbene intermediate 3(a–i) from 1-chloroacetylisatin and n-butyl lithium which is simultaneously trapped by hexamethyldisilazane before undergoing its in situ hydrolysis with methanol to initiate its concomitant cyclocondensation to produce 4(a–i) in high yield and purity.