Kinetic separation methodology for the stereoselective synthesis of (E)- and (Z)-α-fluoro-α,β-unsaturated esters via the palladium-catalyzed carboalkoxylation of 1-bromo-1-fluoroalkenes

[GRAPHICS] Methodology for the stereoselective preparation of both (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated esters is described. 1-Bromo-1-fluoroalkenes (EIZ approximate to 1:1) can be isomerized to high EIZ ratio mixtures, which participate in palladium-catalyzed carboalkoxylation and lead to (Z)-alpha-fluoro-alpha/beta-unsaturated esters in high stereoselectivity. The same starting material can also be kinetically reduced to get an EIZ ratio of 0:100; similar carboalkoxylation reaction at 70 degreesC affords (E)-alpha-fluoro-alpha,beta-unsaturated esters stereospecifically.