Other Type A Syntheses

Other Type A Syntheses.—Successive treatment of lactone (4) with hydrochloric acid and thiourea yields 2-amino-5-hydroxyethyl-4-methylthiazole, an intermediate in the synthesis of vitamin j8j8-Dichloro-a-amino-acrylonitrile, 

ClaC=C(CN)NH2, prepared from hydrogen cyanide and dichloroacetonitrile, reacts with thioformamide in the n ssary presence of toluene-/7-sulphonic acid to give thiazole-4-carbonitrile. 2-Methylthiazole-4-carbonitrile may be prepared similarly. 4-Aryl-3-arylamino-5-imino-l,2,4-thiadiazolidines (Hector s 

4- amino-thiazoles (7 R = H, Et, or Ph) may be prepared by allowing )3-cyano-vinyltriphenylphosphonium bromide, PhaPCH=CHCN Br , to react with a thioamide RC(S)NHa (R = H, Et, or Ph) a 03-cyano-y-amino-y-alkyl)-allyl-triphenylphosphonium bromide is formed also.  

Other Type A (S—C—N + C—C) Syntheses.—2,4-Dichloro-2,3-epoxyalka-noates (3), (obtainable by the reaction of aliphatic a-halogenoaldehydes with methyl dichloroacetate) react with thiourea in methanol to yield 2-amino-4-methoxycarbonyl-5-(l-methoxyalkyl)thiazoles (4) as shown.  

Desaminothiamine (6 R = H) and other 2 -, 4 -, and S-variants of thiamine, have been prepared by attaching the thiazole moiety, derived from carbon disulphide and 3-chloropentan-l-ol-4-one, to the appropriate pyrimidine, followed by oxidative desulphurization of the resulting thiazolinethiones (5) with hydrogen peroxide.  

Arakawa, T. Miyasaka, and H. Ohtsuka, Chem. and Pharm. Bull. (Japan), 1972,20,1041. 

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