1.2.6- Thiadiazin

Under acidic conditions, a thiosemicarbazone intermediate (145) has been isolated, this can be cyclized in alcohol either into the corresponding 2-hydrazinothiazole (142) in the presence of benzaldehyde or into 1,3,4-thiadiazine (146) in the absence of benzaldehyde (Scheme 71) (375, 397, 408). 

DiaminO 4,4-dimethyl-l,3,5-thiadiazine hydrobromide was isolated as by-product (418). Benzene sulfonates of cyanohydrin prepared from sodium cyanide and an halobenzoaldehyde, when treated with thiourea or its derivatives, afford 2,4-diamino-5-(p-halogenophenyl)-thiazole benzene sulfonates (447). Similarly, cyanoamido thiocarbamates obtained from cyanamide and isothiocyanates yield substituted 2,4-diaminothiazoles (598). 

Another example is a claim of possible industrial appHcation for preparing l-cyclohexyl-3,5-dimethylpyrazole [79580-49-7] (75) and similar compounds from 1,2,6-thiadiazine-l,1-dioxide (74) by extmsion of SO2 (eq. 20) (48). This process has the added advantage of not requiring hydrazine derivatives as reactants. 

Chloromethylbenzo-l,2,4-thiadiazine 1,1-dioxide forms quaternary salts, e.g. 8 (n = 1), with pyridine, 2- and 3-picolines, and iso-quinoljne, but the 3-(2 -chloroethyl) compound gives a lower yield of the salt, e.g. 8 (% = 2), because some of the halogen derivative is converted into the 3-vinyl compound. ... 

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