反应详情

A mixture of 5-acetyl-indole-1-carboxylic acid tert-butyl ester [4.85 g, 18.70 mmol, Intermediate (18)], ethylene glycol (5.0 g), pyridinium p-toluenesulfonate (100 mg) in benzene (35 mL) is refluxed under N2 with a Dean-Stark trap for 24 hours. To this resulting dark reaction mixture is added solid NaHCO3 (2.5 g). After stirring for 15 minutes, it is filtered under suction and washed three times with ethyl acetate (30 mL). The filtrate is washed twice with water (10 mL) and dried over sodium sulfate. The crude is chromatographed on 10 g silica gel cartridge (heptane then 10% ethyl acetate in heptane) afforded 5-(2-methyl-[1,3]dioxolan-2-yl)-indole-1-carboxylic acid tert-butyl ester [Intermediate (19)] as colorless oil; 1H NMR (CDCl3): δ 8.128 (1H, d), 7.706 (1H, s), 7.625 (1H), 7.475 (1H, dd), 6.591 (1H, d), 4.106 (2H, m), 3.843 (2H, m), 1.742 (3H, s), 1.703 (9H, s); LC/MS: 304 (M+H).

1. temperatureis refluxed under N2 with a Dean-Stark trap for 24 hours
2. customTo this resulting dark reaction mixture
3. filtrationit is filtered under suction
4. washwashed three times with ethyl acetate (30 mL)
5. washThe filtrate is washed twice with water (10 mL)
6. dry with materialdried over sodium sulfate
7. customThe crude is chromatographed on 10 g silica gel cartridge (heptane