2-Amino-5-methylthiazole → 2-Amino-3-(4-ethoxy-2,4-dioxobutyl)-5-methylthiazol-3-ium bromide

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Reaction Steps

Ethyl 4-bromo-3-oxobutanoate (92 g, 0.35 mol) was added to a solution of 5-methylthiazol-2-amine (40 g, 0.35 mol) in acetone (400 mL). The mixture was left to stand overnight and then evaporated to give 2-amino-3-(4-ethoxy-2,4-dioxobutyl)-5-methylthiazol-3-ium bromide in 82% yield, 101 g. 2-amino-3-(4-ethoxy-2,4-dioxobutyl)-5-methylthiazol-3-ium bromide (101 g, 0.28 mol) was then refluxed in ethanol (250 mL) for 2 hours. The solvent was then evaporated to give ethyl 2-(2-methylimidazo[2,1-b]thiazol-6-yl)acetate hydrobromide as yellow crystals in 97% yield, 85 g. Solid K2CO3 was added to a solution of ethyl 2-(2-methylimidazo[2,1-b]thiazol-6-yl)acetate hydrobromide (85 g, 0.28 mol) in water (300 mL) to pH ˜8. The product was extracted with chloroform (3×100 mL), and the combined extracts were dried over Na2SO4 and evaporated to give ethyl 2-(2-methylimidazo[2,1-b]thiazol-6-yl)acetate in 84% yield 52 g. Ethyl 2-(2-methylimidazo[2,1-b]thiazol-6-yl)acetate (52 g, 0.23 mol) was refluxed in 10% aqueous HCl (150 mL) for 2 hours. The solution was evaporated to dryness to give the title compound as brown crystals in 59% yield 32.3 g; m/z 197 [M+H]+.

Provenance & Evidence