Studies on novel heterocyclic ring systems. Reaction of 4‐hydroxylcoumarin with o‐aminobenzaldehyde and 2‐mercaptoaniline

Abstract
Reactions of 4‐hydroxycoumarin (1) with o‐aminobenzaldehyde (2) and 2‐mercaptoaniline (5) have been investigated. The yet unreported 6,12‐dihydro‐l‐benzopyrano[3,4‐b][1,4]benzothiazin‐6‐one (6) system has been synthesized and characterized on the basis of spectral and analytical data. A novel synthetic route to 6H‐l‐benzopyrano[4,3‐b]quinolin‐6‐one (4) is reported. HMO calculations predict the most reactive sites on the molecules.