Ethyl propiolate → pyrrolo[2,1-b]thiazole-7-carboxylic Acid Ethyl Ester

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Reaction Steps

Under nitrogen atmosphere (trimethylsilyl)methyl trifluoromethanesulfonate (16.3 mmol) is added dropwise to a mixture of 2-methylthio-1,3-thiazole (15.5 mmol) in acetonitrile (75 mL). The mixture is treated with propynoic acid ethyl ester (23.2 mmol), kept with occasional shaking for 30 min at RT and added dropwise to a vigorously stirred solution of CsF (21.7 mmol) and propynoic acid ethyl ester (23.2 mmol) in acetonitrile (75 mL). After stirring for 1 h the mixture is concentrated in vacuo, diluted with DCM (100 mL), washed twice with water and twice with brine and dried over Na2SO4. The solvents are removed in vacuo and the residue is purified by flash chromatography (gradient: heptane to heptane/EtOAc 8/2) to give the desired product. LC-MS: tR=0.87 min; [M+H]+=196.0.

Provenance & Evidence