Efficient Synthesis of 4-Halo-4-penten-2-ones and 3-Halo-3-butenoic Acids/Esters via Hydrohalogenation Reaction of 3,4-Pentadien-2-one and 2,3-Butadienoic Acid/Methyl Ester

S. Ma, Z. Shi, L. Li, J. Org. Chem. 1998, 63, 4522-4523.