bromine; sodium carbonate; acetic acid in water

in benzene from a suspn. of dihydroxybutenedioic acid and triethylboroxine in benzene the half amt. of benzene was removed by azeotropic distn.; the remaining suspn. was cooled; filtered and the crystn. compd. washed with hexane; further purifn. by high vac. sublimation at ca 130-150°C or crystn. from a large vol. of toluene; elem. anal.;

a suspn. of dihydroxybutenedioic acid and diethyl(pivaloyloxy)borane was slowly heated to ca 70°C; on completion of gas evolution the mixt. was cooled, hexane was added; crystn. compd. filtered and washed with hexane; further purifn. by highvac. sublimation at ca 130-150°C or by crystn. from a large vol.of toluene; elem. anal.;

in benzene to dihydroxybutenedioic acid in benzene cooled to 0°C was added CH3BBr2; on warming to room temp. followed gas evolution for ca 15 min; mixt. then was heated slowly under reflux for ca 30 min, cooled; filtered and the compd. washed thoroughly with hexane; further purifn. by vac. sublimation at ca 130-150°C or by crystn. from a large vol. of toluene; elem. anal.;

1: dihydroxybutenedioic acid With bromine; acetic acid in water 2: ethanol With hydrogenchloride T=0°C;