Synthesis of New Heterocyclic Compounds by the Skraup Reaction of Amino-9H-thioxanthen-9-ones

Abstract

The Skraup reaction of amino-9H-thioxanthen-9-ones was conducted in the presence of glycerol, fuming sulfuric acid, nitrobenzone, iron(II) sulfate and boric acid. 1-Amino-9H-thioxanthen-9-one (1) gave 12H-[1]benzothiopyrano[2, 3-h]quinolin-12-one (5). 2-Amino-(2) and 3-amino-9H-thioxanthen-9-ones (3) gave angular-type products, 12H-[1]benzothiopyrano[3, 2-f]quinolin-12-one (6) and 7H-[1]benzothiopyrano[2, 3-f]quinolin-7-one (8), but did not give linear-type products. 4-Amino-9H-thioxanthen-9-one (4) gave 7H-[1]benzothiopyrano[3, 2-h]quinolin-7-one(10).