1.3- Thiazin-6-ones

Chemical Name 2-(4-Chlorophenyl)tetrahydro-3-methyl-4H-1,3-thiazin-4-one 1,1-dioxide Common Name Chloromethazanone Structural Formula ... 

A variety of N,S-bis(nucleophiles) react with unsaturated 5(47/)-oxazolones to produce triazolo-l,3-thiazin -ones 570 and 1,3-thiazin-4-ones 572. Mechanistically, Michael addition of the bis(nucleophile) to 569 and 571 followed by ring opening with concomitant cyclization leads to the observed products. 

In this sequence, substitution by 1 mol of dimethylamine first replaces the benzylmercaptan leading to 5-acetyl-2-dimethylamino-6//-l,3-thiazine (197). The thiazine then undergoes attack by dimethylamine excess at C-6, leading to the thiourea (198). The benzylmercaptan liberated in the first reaction may act as a nucleophile (BzS",H2NMe2+), and a different thiourea substituted by dimethylamino and benzylthio groups is obtained. The action of pyrrolidine on 1,3-thiazine-4-ones (194) can be seen as a Michael addition followed by elimination of H2S. In acidic media, the linear compound obtained is cyclized to the pyrimidone (200) (Scheme 80)... 

Suzdalev, K. F., Chemistry of 1,3-Thiazin-4-ones and Their Derivatives, 66, 131. 

The carbonyl portion of 2-iminobenzo-TA 94 can be converted into the thioxo group with the formation of derivatives 261 (67PHA611) (Scheme 102). The analogous reactions are also known for monocyclic 1,3-thiazin-4-ones (67CJC939) and for 2,3-dihydro-l,3-benzothiazin-4-ones (55BSF-1518). 

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