An expedient stereoselective synthesis of (E)-α,β-unsaturated esters and thioesters using FeCl₃·6H₂O

Facile and convenient synthesis of α,β-unsaturated esters and thioesters from alkylidene derivatives of Meldrum's Acid is described. This method uses catalytic amount of FeCl₃·6H₂O (0.001–0.005 equiv) with alcohols/thiols (1 equiv) in dry CH₃NO₂ followed by catalytic amount of piperidine. A variety of α,β-unsaturated esters and thioesters have been synthesized with high E-stereoselectivity in good to excellent yields. The application of this methodology is demonstrated by gram scale synthesis of octinoxate, a sunscreen agent, and other p-methoxycinnamate esters.