3,6-Dihydro-5H-pyrazolo [4′,3′:5,6]pyrano[3,4-b]indol-5-one

Abstract

Pyrano [3,4-b]indol-1(9H)-ones and indolo [2,3-c]coumarins are important classes of heterocyclic compounds with versatile biological activities. Herein, we describe a straightforward and scalable synthesis of 3,6-dihydro-5H-pyrazolo [4′,3′:5,6]pyrano [3,4-b]indol-5-one, a pyrazolo-fused pyrano [3,4-b]indolone, via a three step approach including Fischer-indole synthesis and intramolecular esterification. The compound is fully characterized by means of 1H and 13C NMR spectra, using direct and long-range heteronuclear correlation experiments (HMBC and HMQC).