反应详情

0.29 ml (3.4 mmol) of 1,2-dibromoethane was added to a suspension of 1.66 g (68.1 mmol) of magnesium in 5 ml of anhydrous tetrahydrofuran under a stream of nitrogen. 9.96 g (51.1 mmol) of 3-bromo-2-methylpropionaldehyde ethylene acetal [prepared as described in step (i) above] were then added dropwise to the resulting mixture, whilst ice-cooling, after which the mixture was stirred for 1 hour. A solution of 6.58 g (34.1 mmol) of N-methoxy-N-methyl-3,4-dimethylbenzamide in 30 ml of tetrahydrofuran was then added dropwise to the mixture, and the resulting mixture was stirred, whilst ice-cooling for 1 hour. A saturated aqueous solution of ammonium chloride was then added to the mixture, and the resulting mixture was extracted twice with ethyl acetate. The organic extracts were combined and washed with a saturated aqueous solution of sodium chloride, after which they were dried over anhydrous magnesium sulfate and concentrated by evaporation under reduced pressure. The residue thus obtained was applied to a silica gel chromatography column and eluted with a 6:1 by volume mixture of hexane and ethyl acetate, to give 3.26 g (yield 39%) of the title compound as a colorless oily substance.

1. temperaturecooling
2. stirringthe resulting mixture was stirred, whilst ice-
3. temperaturecooling for 1 hour
4. extractionthe resulting mixture was extracted twice with ethyl acetate
5. washwashed with a saturated aqueous solution of sodium chloride
6. dry with materialafter which they were dried over anhydrous magnesium sulfate
7. concentrationconcentrated by evaporation under reduced pressure
8. customThe residue thus obtained
9. washeluted with a 6:1 by volume mixture of hexane and ethyl acetate