反应详情

温度

80 °C

1-Dimethylamino-1-methoxyethylene (4 cc) is added, in the course of 55 minutes, to a solution of 7-t-butoxycarbonylamino-2-(4-methoxybenzyloxycarbonyl)-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene (3.75 g) in dimethylformamide (25 cc), heated to 80° C., the temperature being kept at 80° C. This yields a solution of 7-t-butoxycarbonylamino-3-(2-dimethylaminoprop-1-en-1-yl)-2-(4-methoxybenzyloxycarbonyl)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene, which is poured into a mixture of iced water (20 cc) and ethyl acetate (150 cc). The organic phase is washed with water (2×200 cc), dried over sodium sulphate and filtered in the presence of decolorising charcoal and the filtrate is evaporated to dryness under reduced pressure (20 mm Hg; 2.7 kPa). The residue is chromatographed on a column of Merck silica gel (0.06-0.2) (45 g) (diameter of the column: 3 cm, height: 15 cm). Elution is carried out with a 20/80 (by volume) ethyl acetate/cyclohexane mixture (500 cc) and 40 cc fractions are collected. Fractions 7 to 10 are concentrated to dryness under reduced pressure (20 mm Hg; 2.7 kPa) and this yields a mixture (70/30) of 3-acetonyl-7-t-butoxycarbonylamino-2-(4-methoxybenzyloxycarbonyl)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene and -oct-3-ene (0.25 g) in the form of an ochre solid.

1. custombeing kept at 80° C