Synthesis of substituted α-(hydroxymethyl)-β-iodoacrylates via MgI₂-promoted stereoselective aldol coupling

The efficient and highly stereoselective syntheses of a variety of (Z)-configured, substituted α-(hydroxymethyl)-β-iodo-acrylates from prop-2-ynoate and various aldehydes was achieved. The synthetic protocol involves a simple one-pot coupling reaction under mild conditions, promoted by MgI₂, which serves both as a Lewis acid and iodine source for a Baylis-Hillman-type reaction. All adducts were generated in good-to-excellent yields, the (Z)-isomers being formed in high selectivity (>98%). The conversion of methyl prop-2-ynoate into an active 'β-iodo allenolate' intermediate, which then nucleophilically attacks an aldehyde, is proposed as a plausible reaction mechanism.