Patent GB-557550-A (GB)
IPC: C07D277/36
Abstract: 557,550. Dye intermediates. KENDALL, J. D. April 23, 1942, No. 5437. [Class 2 (iii)] Dye intermediates of the general formula (I) (wherein X and Y each represent O or S, R 1  is H or a hydrocarbon group, R  2  is a hydrocarbon group, and R 3  is an alkyl group) are prepared by reacting compounds of the general formula (II) (where R 4  is an alkyl group) with a mercaptan R 2 SH or a trithio-orthoformic ester (R 2 S) 3 CH or an orthoformic ester (R 2 O) 3  CH in the presence of a mineral acid or an alkyl or aralkyl ester thereof and in the presence of a solvent for the reactants. Compounds of the general formula II may be prepared by reacting rhodanic acid or oxarhodanic acid with a 2-alkoxymethylene- 1 : 3-diketone in the presence of a solvent and an alkaline condensing agent. The hydrocarbon groups may be methyl, ethyl, propyl, benzyl, naphthylmethyl, phenyl, naphthyl, allyl, or cinnamyl groups. R 3  and R 4  are preferably lower alkyl groups. The mineral acid is preferably hydrochloric acid. A mercaptan, when used, acts as a solvent for the reactants and no auxiliary solvent is necessary. 5 - (# - diacetylvinyl) N - ethylrhodanic acid is prepared by refluxing N-ethylrhodanic acid and ethoxymethylene-acetylacetone in ethyl alcohol in presence of fused sodium acetate. 5 - (# - diacetylvinyl) - N - methylrhodanic acid, 5 - (# - diacetylvinyl) - N - methyloxarhodanic acid, 5 - (# - diacetylvinyl) - N - ethyloxarhodanic acid, 5 - (# - diacetylvinyl) rhodanic acid, 5 - (# - dipropionylvinyl) - N methylrhodanic acid, and 5 - (# - diacetylvinyl) N - phenylrhodanic acid are similarly prepared. 2 - thio - 3 - ethyl - 4 - keto - 5 - (γ - ethylthiocrotonylidene)-tetrahydrothiazole is prepared by (a) allowing 5-( #-diacetylvinyl)-N-ethylrhodanic acid, ethyl mercaptan, methyliodide, and methyl alcohol to stand together in a sealed flask or (b) passing HCl through a flask containing 5 - (# - diacetylvinyl) - N - ethylrhodanic acid, ethyl mercaptan, and methyl alcohol in a freezing mixture. 2-thio-3-methyl- 4 - keto 5 - (γ - ethylthiocrotonylidene) - tetrahydrothiazole is prepared similarly by method (a) using either ethyl mercaptan or ethyl trithio-orthoformate. 2-thio - 3 - methyl - 4 - keto - 5 - (γ-ethylthiocrotonylidene) - tetrahydro - oxazole, 2 - thio - 3 - ethyl - 4 - keto - 5 - (γ - ethylthiocrotonylidene)- tetrahydro - oxazole, 2 - thio - 3 - methyl - 4 - keto - 5 - (γ - ethoxycrotonylidene) - tetrahydrothiazole (using sulphuric acid), 2 - thio - 3 - ethyl - 4 - keto - 5 - (y - ethoxycrotonylidene) - tetrahydrothiazole (using H 2 SO 4  or HC 2 ), 2-thio-3- methyl - 4 - keto - 5 - (y - ethoxycrotonylidene) - tetrahydro-oxazole (using H 2 SO 4 ), 2-thio-4-keto- 5 - (γ - ethylthiocrotonylidene) - tetrahydrothiazole) 2 - thio - 4 - keto - 5 - (γ -ethoxycrotonylidene) - tetrahydrothiazole (using H 2 SO 4 ), 2-thio- 3 - methyl - 4 - keto - 5 - (y - ethylthio : γ - ethylallylidene) - tetrahydrothiazole, 2 - thio - 3 - phenyl - 4 - - keto - 5 - (y - ethylthiocrotonylidene) - tetrahydrothiazole, and 2-thio-3-ethyl-4-keto-5-(γ- benzylthiocrotonylidene) - tetrahydro - oxazole are similarly prepared. Ethoxymethylenedipropionylmethane is prepared by heating together dipropionylmethane, ethyl orthoformate, and acetic anhydride. Specification 557,549 is referred to.