Expedient Synthesis of 6-Aryl Derivatives of 3,4-Dihydro-1,4,4a,6a-tetraaza-benzo[a]fluoren-2-one: A New Heterocyclic Framework

Abstract

3,4-Dihydro-1,4,4a,6a-tetraaza-benzo[a]fluoren-2-one, a new tetracyclic heterocyclic framework, is designed through a simple and convenient synthetic sequence. Its 6-aryl derivatives are synthesized starting from 1H-indole-2-carboxylic acid. The reaction of differently substituted phenacyl bromides with 1H-indole-2-carboxylic acid and POCl₃-mediated cyclization of the resultant 1H-indole-2-carboxylic acid phenacyl ester provided 2-oxa-4a-aza-fluoren-1-one, and its sequential reaction with hydrazine and 2-chloro-acetamide furnished the desired new heterocyclic compounds 7a–f.

Keywords:

• 2-Amino-4-phenyl-2H-pyrazino[1,2-a]indol-1-one
• 3,4-dihydro-1,4,4a,6a-tetraaza-benzo[a]fluoren-2-one
• 1H-indole-2-carboxylic acid
• phenacyl bromide
• phenacyl ester
• 4-phenyl 2-oxa-4a-aza-fluoren-1-one

ACKNOWLEDGMENTS

We thank the management of Dr. Reddy's Laboratories Ltd. for extending support to the work. Cooperation from the project colleagues and analytical department is highly appreciated.