Methyl 2-bromo-2-butenoate(Methyl (Z)-2-bromocrotonate) yields (S)-2-bromobutanoic acid by baker′s yeast fermentation. It undergoes biotransformation catalyzed by old yellow enzyme to yield methyl (S)-2-bromobutanoate, a key intermediate for the synthesis of chiral drugs. It is a biannelating reagent which participates in double Michael-additions.
Ethyl or methyl crotonate is treated with Br2/CCl4 or Br2/AcOH followed by dehydrobromination with quinoline or DBU to afford Methyl 2-bromo-2-butenoate.
Handle under nitrogen in a fume hood; these reagents are moisture-sensitive. Store refrigerated and in brown bottles to avoid polymerization. Caution: lachrymator and irritant; may be harmful.
