N-bromobutanimide → methyl (E)-4-bromo-3-methoxy-pent-2-enoate

Participants

Reaction Conditions

Reaction Steps

A 500-ml 4-necked pear-shaped flask equipped with a mechanical stirrer, a thermometer, a cooler, an argon inlet and an oil bath was charged under argon with 31.2 g of crude methyl (E)-3-methoxy-2-pentenoate (ca. 0.217 mol), 10.45 g of N-bromo succinimide (58.7 mmol), 0.47 g of 2,2′-azobis(2-methylpropionitrile) (2.86 mmol) and 100 ml of carbon tetrachloride. The resulting yellow suspension was heated for 10 min with an 80° C. oil bath to give an almost colorless suspension. Then three additional portions consisting each of 10.45 g of NBS, 0.47 g of AIBN and 35 ml of carbon tetrachloride, in total 31.35 g of N-bromo succinimide (0.176 mol), 1.41 g of 2,2′-azobis(2-methylpropionitrile) (8.59 mmol) and 105 ml of carbon tetrachloride were added in 5 min time intervals at the same temperature. 20 min after the last addition of reagents (total reaction time was 45 min) the oil bath was removed and the reaction mixture cooled under stirring with an ice bath for ca. 30 min. The suspension was filtered with suction and the filter cake washed with a total of 90 ml of carbon tetrachloride. The filtrate was rotary evaporated to dryness (50° C., 10 mbar) to give 49.7 g of crude methyl rac-(E)-4-bromo-3-methoxy-pent-2-enoate (theor. amount 48.4 g) as an orange oil. This material was used without purification in the next step.

Provenance & Evidence