Thiazoline-2-thiones ring opening

Recently, Hoff and Blok report the reductive ring opening of 4-methyl-A-4-thiazoline-2-thione anion (80) (Scheme 39) (204) when treated with two equivalents of sodium in liquid amonia. Treatment of the prop-enethiolate (83) by 4N aqueous HCl affords 4-methylthiazole. The... 

Retro-Hantzsch, mechanism of, 84, 85, 102 Rhodanine, alkylation of, 419 ambident reactivity of. 419 reaction with aryldiazonium salts, 419 reaction with halogenothiazoles, 79 Rice cultures, 135, 136, 137 Ring-chain tautomerism, 113 Ring opening, of A-2-thiazoline-5-one, 433 Ring transformation, 5 amino-A-4-thiazo-line-2-thione to 4-mercapto-imidazoline-2-thione, 399 5,5-diphenyl-2,4-thiazolidinedithione, to 4,5-diphenyl-A-4-thiazoline-2-thione, 37 3... 

If R3 or R4 is a 2-hydroxyethyl group or a 2-acetoxyethyl group, treatment with hydrochloric acid yield 3-(2-methyl-4-amino-5-pyrimidi-nylmethyl)-2,3,3a,5,6,6a-hexahydrofuro[2,3-d]thiazole-2-thione (CXCVI) with liberation of water or acetic acid (Table 21). On further hydrolysis with acids the tetrahydrofuran ring opens again and 3-(2-methyl-4-amino-5-pyrimidinylmethyl)-4-methyl-5-(2-hydroxyethyl)-/l4-thiazoline-2-thiones are obtained (Table 29)-... 

Alkylation Reactions.—The mechanism proposed for the conversion of benzo-thiazoline-2-thione (29 R = CH2CH2OH, X = S) into the corresponding benzothiazolin-2-one (29 X = O) with ethylene oxide in acetic acid is considered to involve ring-opening by the thione sulphur atom to give the j8-sub-stituted ethanol. This reacts with acetate ion or acetic acid at the 2-position to give an acetate, which decomposes to MeC(0)SCHaCH20H and (29 X = O). In support of the mechanism, no desulphurization occurred when the reaction was attempted in acetone or methanol. 

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