反应详情

1.97 g (10 mmoles) of 4-methoxy-3-nitrobenzoic acid was dissolved in 50 ml of acetonitrile. 1.15 g (10 mmoles) N-hydroxysuccinimide was added with agitation. Finally 2.063 g (10 mmoles) of N,N′-dicyclohexylcarbodiimide were added and the mixture agitated. After 2 hours at approx. 20° C. a precipitate of dicyclohexyl-urea had formed. The solution was filtered through a Gooch 3G funnel. The formation of ester was determined by t.l.c. of the filtrate (CHCl3/MeOH=9:1, v/v). Observation under U.V. revealed the ester as a dark spot of Rf approx. 0.9. After evaporation of the acetonitrile a whitish-yellow powder remained in the flask. The powder was redissolved in 50 ml of hot isopropanol. Approximately 2 spatula-tips activated charcoal were added and the solution was boiled in a boiling water-bath for about 5 minutes. The boiling solution was quickly poured through a sintered glass filter (G4, previously heated by a passage of hot isopropanol) into a hot flask. The solution was allowed to cool down overnight. White, needle-like crystals were formed (m.p. approx. 145-152° C.) having the expected t.l.c. properties.