反应详情

To a stirred mixture of 2.2 g of trans (4-hydroxy-cyclohexyl)-carbamic acid tert-butyl ester, 4 g of triphenyl-phosphine, 4.2 g of 4-nitrobenzoic acid, 120 mL of benzene and 10 mL of THF was added 3.5 g of diisopropyl-azo-di-carboxylate over 5 min. The mixture was allowed to stir at room temperature for 4 h and then concentrated under reduced pressure, taken up in 250 mL of dichloromethane and filtered and again concentrated. Chromatography on silica gel eluting with a gradient of 2%-20% ethyl acetate in hexane gave 1.2 g of product as a crystalline solid; 1H NMR (400 MHz, CDCl3) 8.3 (d, 2H), 8.2 (d, 2H), 3.8 (br m, 1H), 3.6 (br m, 1H), 2.4 (d, 1H), 2.1-1.6 (complex m, 8H), 1.45 (s, 9H).

1. concentrationconcentrated under reduced pressure
2. filtrationfiltered
3. concentrationagain concentrated