GB584981A - Manufacture of thiazoline derivatives - Google Patents

Abstract

Thiazoline derivatives of general formula <FORM:0584981/IV/1> wherein R, R1 and R111 each represent hydrogen or a hydrocarbon radical and R11 represents a hydrocarbon radical, are obtained by interacting an a -acylaminoacrylic ester of the formula <FORM:0584981/IV/2> with phosphorus pentasulphide, conveniently by heating the reactants together in presence of an inert solvent or diluent and preferably in presence of potassium polysulphide, conveniently used as liver of sulphur. In examples: (1) methyl a - benzoylamino - b : b - dimethyl - acrylate, phosphorus pentasulphide and potassium polysulphide are heated together under reflux, in toluene, and the residual oil, in methanol, is distilled in vacuo to isolate methyl 2-phenyl-5 : 5-dimethylthiazoline-4-carboxylate; (2) methyl a -acetylamino-b b -dimethylacrylate, phosphorus pentasulphide and potassium polysulphide are treated as in (1) using benzene to isolate methyl 2 : 5 : 5-trimethylthiazoline-4-carboxylate; (3) ethyl a -benzoylaminocinnamate, phosphorus pentasulphide and potassium polysulphide are treated as in (1), using toluene, and the residual oil, after removing sulphur, is saturated, in dry ether, with hydrogen chloride, the residue being treated with aqueous sodium bicarbonate and extracted with ether to isolate ethyl 2 : 5-diphenylthiazoline-4-carboxylate, from which the corresponding 4-carboxylic acid is obtained by saponification and ultimate acidification. Methyl-a -benzoylamino-b : b -dimethylacrylate is obtained by heating under reflux 2-phenyl-4-isopropylidene-5-oxazolone, methanol and concentrated sulphuric acid and pouring the mixture into water to isolate the product. Methyl - a - acetylamino - b : b - dimethylacrylate is obtained from chloroacetylvaline, which is converted into 2 - methyl - 4 - isopropyline - 5 - oxazolone by heating with acetic anhydride, which substance is treated with methanolic sodium methoxide.