Concise bromodecarboxylation of cinnamic acids to β-bromostyrenes

A convenient salt-free approach to the halodecarboxylation of cinnamic acid analogs to β-bromostyrene was reported. This conversion was conducted at 0 °C in CH2Cl2 with only 10% of acetic acid. This protocol can be used for cinnamic acids with a variety of substituents, including β-methyl cinnamic acid (1d) in 60-81% yield, but not for hydroxyl- and p-methyl-cinnamic acids. Meanwhile, pyridine hydrobromide perbromide was used as bromide source to convert 1a-2a in 59% yield.