反应详情

5-Methyl-4-amino-thiophene-2-carboxylic acid 1,3-benzodioxol-5-ylmethyl ester from Step 2 (0.15 g, 0.5 mmol) was dissolved in hot 1,4-dioxane (6-8 mL) under an inert atmosphere, stirred, and treated with benzyl isocyanate (0.07 g, 0.5 mmol). After 72 hours at room temperature, the mixture was diluted with diethyl ether (50 mL). After another hour the precipitate was filtered off, rinsed with ether, and dried to afford 0.14 g of 4-(3-benzyl-ureido)-5-methyl-thiophene-2-carboxylic acid 1,3-benzodioxol-5-ylmethyl ester; mp 216-217° C.

1. filtrationAfter another hour the precipitate was filtered off
2. washrinsed with ether
3. customdried