Esterification of α-Halo-α,β-unsaturated Aldehydes by Using a Carbene Catalyst

Du et al. have reported the esterification of α-halo-α,β-unsaturated aldehydes by using a carbene catalyst. According to their results, α-halo-α,β-unsaturated aldehydes react with various alcohols in the presence of DBU and a catalytic amount of 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride to provide α,β-unsaturated esters in high yields with excellent stereoselectivity. Presumably, the intermediates undergo elimination of hydrogen halides under basic conditions to afford the α,β-unsaturated esters.