ENCHAINEMENTS HETEROATOMIQUES ET LEURS PRODUITS DE CYCLISATION-VIII1 METHYLENE-2 DIHYDRO-3,6 2H-THIAZINES-1,3 FONCTIONNALISEES EN POSITION 4 PAR SUBSTITUTION NUCLEOPHILE D'UN GROUPEMENT BROMOMETHYLE ET PAR CONVERSION D'UN GROUPEMENT DIBROMOMETHYLE EN ALDEHYDE, NITRILE ET ESTER

Treatment with NBS of 2-methylene-3,6-dihydro-2 H -1,3-thiazines carrying an ester function on 5 and a methyl on 4 gives the corresponding 4-bromomethyl and 4,4-dibromomethyl derivatives in a perfectly selective manner. The monobromo compounds give access to 4-aminomethyl, 4-alkoxymethyl, 4-alkylthiomethyl, 4-acetoxymethyl and 4-formyl thiazines. These aldehydes, also prepared from the dibromo derivatives, are converted into 4-cyano and 4-alkoxycarbonyl thiazines. In certain cases, interactions with the neighbouring ester group, leading to lactones are observed.