Reaction of sulfenes with heterocyclic N,N‐disubstituted α‐aminomethyleneketones. XIII. Synthesis of 1,2‐oxathiino[6,5‐f]quinazoline derivatives

Abstract

The 1,4‐cycloaddition of sulfene to N,N‐disubstituted (E)‐6‐aminomethylene‐7,8‐dihydro‐(2‐methyl)‐(2‐phenyl)quinazolin‐5(6H)‐ones I gave N,N‐disubstituted 4‐amino‐3,4,5,6‐tetrahydro‐(8‐methyl) (8‐phenyl)‐1,2‐oxathiino[6,5‐f]quinazoline 2,2‐dioxides II, which are derivatives of the new heterocyclic system 1,2‐oxathiino[6,5‐f]quinazoline. With 2‐phenylenaminones Id‐h, the cycloaddition occurred, generally in satisfactory yields, both in the case of aliphatic N,N‐disubstitution and aromatic N‐monosubstitution, whereas with 2‐methyl enaminones Ia‐c the reaction took place in low yields only in the case of aliphatic N,N‐disubstitution. Also the reaction of 2‐phenyl enaminones Id‐g with chlorosulfene occurred as with sulfene, giving a mixture of cycloadducts which were dehydrochlorinated in situ with DBN to afford N,N‐di‐substituted 4‐amino‐5,6‐dihydro‐8‐phenyl‐1,2‐oxathiino[6,5‐f]quinazoline 2,2‐dioxides III generally in satisfactory yields. Compounds III could not be dehydrogenated either by DDQ in boiling benzene or by palladium on carbon in boiling p‐cymene.