The ring‐closure reactions of N‐(3,4‐dimethoxyphenylthiomethyl)‐2‐nitrobenzamide derivatives 5a,b with phosphoryl chloride gave 4‐(2‐nitrophenyl)‐2H1,3‐benzothiazine derivatives 7a,b, which on reduction yielded 4‐(2′‐aminophenyl)‐3,4‐dihydro‐2H‐1,3‐benzothiazines 8a,b. Reaction of these compounds with phosgene led to a new heterocyclic ring system, 6H,8H‐quinazolino[3,4‐c][1,3]benzothiazine derivatives 9a,b. The structures of the title compounds were proved via their ir and nmr (1H, 13C) spectra.
ASJC Scopus subject areas
- Organic Chemistry