| production method | add 105mL(86G, 1mol) to a 2L four-mouth bottle 3-methyl-2-butanone and 600ml of anhydrous methanol were stirred and cooled (ice-salt bath) to 0-5 °c. Then 160g(54.6mL,1mol) of bromine is quickly added from the dropping funnel with stirring (fast addition is important, otherwise the isomer increases), the temperature will increase, but not more than 10 deg C (otherwise isomers), and then continue to stir at 10 deg C to the end of the reaction, Red completely fade (about 45min), add 300ml water (should not be layered), stir overnight at room temperature (complete hydrolysis of Ketal), then add 10% ml of water, then extract with ml of ether × 4, combine the ether solution, then use ml of potassium carbonate solution, washing with 145 × 2 of water, drying with anhydrous calcium chloride for 1H, and spin-dissolving under reduced pressure to obtain -158g of crude product (main product: isomer = 95: 5), the fraction of 83-86 ° C./7.2kPa was collected by vacuum fractionation using a V column to obtain 115-128g of product with a yield of 69.5%-77.5% and a 1-bromo purity of 95%. |
