Studies on Condensed Heterocyclic Isoquinolone Derivatives. III. A Novel Oxidative Rearrangement of 11-Methyl-6-oxo-3, 4-dihydro-2H, 6H-1, 3-thiazino [3, 2-b] isoquinoline

The reaction of 11-methyl-6-oxo-3, 4-dihydro-2H, 6H-1, 3-thiazino [3, 2-b] isoquinoline (I) or the corresponding sulfone (II) with hydrogen peroxide led to a ring enlargement reaction to give a β-keto-sulfone, 1, 6-methano-1-methyl-7, 12-dioxo-4, 5, 7-trihydro-1H, 3H-benzo [g]-1, 5-thiazonine 2, 2-dioxide (III), which was further converted into an enolsulfone, 12-methyl-7-oxo-3H, 7H-4, 5-dihydro-2, 1, 4-oxathiazepino [4, 3-b] isoquinoline 2, 2-dioxide (VI), by thermal rearrangement. These ring enlargement and thermal rearrangement reactions involve intramolecular migration of the sulfonyl group. On treatment with sodium hydroxide, compound III gave 5-methyl-3, 3a-dihydro-2H, 5H-[2] benzothio-pyrano [4, 3-b] pyrrole 4, 4-dioxide (VIII), presumably by hydrolysis and intramolecular condensation. Reaction of compound I with chlorine in the presence of water gave 3-(4-chloro-4-methyl-1, 3-dioxo-1, 2, 3, 4-tetrahydroisoquinolin-2-yl) propanesulfonyl chloride (X) by ring opening, while compound II gave an additicn product, 11, 11a-dichloro-11-methyl-6-oxo-3, 4, 11, 11a-tetrahydro-2H, 6H-1, 3-thiazino [3, 2-b] isoquinoline 1, 1-dioxide (XIII), as the major product.