2-Amino-5-chlorothiazole hydrochloride → HCID 13105859, Verbindung

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

2-amino-5-chloro-thiazole hydrochloride (10 g) was reacted with ethyl 2-acetoxy-acetoacetate (22 g) in dimethylacetamide (400 ml) containing polyphosphoric acid (71 g: 29 g of H3PO4 and 42 g of P2O5) under stirring at 100° C. for 6 hours. After cooling, dilution with ice water and neutralization with 37% NaOH, the precipitate was extracted with ethyl acetate and the organic solution was evaporated in vacuo to dryness. The residue was hydrolyzed by treatment with 35% HCl (50 ml) in dioxane (100 ml) at reflux temperature for 2 hours: after cooling the reaction mixture was diluted with ice water and neutralized with 37% NaOH and the precipitate was extracted with ethyl acetate. The organic solution was evaporated in vacuo to dryness and the residue was crystallized from methanol to give 5.85 g of 2-chloro-6-hydroxy-7-methyl-5H-thiazolo[3,2-a]pyrimidine-5-one, m.p. 214°-217° C., which was dissolved in dimethylformamide (100 ml) and reacted with methyl iodide (15.4 g) in the presence of anhydrous K2CO3 (15 g) under stirring at 60° C. for 3 hours. After cooling the reaction mixture was diluted in ice water and neutralized with NaH2PO4 : the precipitate was filtered and the aqueous phase was extracted with ethyl acetate for the complete recovering of the product. On the whole it was obtained 5.1 g of 2-chloro-6-methoxy-7-methyl-5H-thiazolo[3,2-a]pyrimidine-5-one, m.p. 138°-141° C., which was reacted with N-bromosuccinimide (17 g, added portionwise) in benzene (150 ml) at the reflux temperature for 40 hours. After cooling the reaction mixture was diluted with ethyl acetate and treated with aqueous NaHCO3 and then with water: the separated organic solution was evaporated in vacuo to dryness and the residue was crystallized from ethyl acetate to give 2.8 g of 7-bromomethyl-2-chloro-6-methoxy-5H-thiazolo[3,2-a]pyrimidine-5-one, m.p. 160°-162° C., which was reacted with triphenylphosphine (2.6 g) in acetonitrile (50 ml ) at the reflux temperature for 3 hours. After cooling and evaporation in vacuo of the solvent, the residue was purified with ethyl acetate to give 3.8 g of (2-chloro-6-methoxy-5H-thiazolo[3,2-a]pyrimidine-5-one-7-yl)-methyl-triphenylphosphonium bromide, which was suspended in dimethylsulfoxide (45 ml) and treated with potassium tert-butoxide (0.75 g) dissolved in dimethylsulfoxide (20 ml) at room temperature under stirring for 10 minutes.

Herkunft & Nachweise