HIGHLY STEREOSELECTIVE PREPARATION OF TRI-SUBSTITUTED AND TETRA-SUBSTITUTED OLEFINS VIA BETA-TRIBUTYLSTANNYL-ALPHA,BETA-UNSATURATED KETONES

The palladium(0)-catalyzed reactions of beta-tributylstannyl-alpha,beta-unsaturated ketones 3 with benzyl or aryl halides in the presence of copper(I) iodide gave the tri- and tetra-substituted olefins 4 or 5 with high stereoselectivity, respectively. It was found that the yields of 5 were remarkably improved by the use of triethylamine as an additive. The starting materials 3 were easily prepared by the tin(IV) chloride-promoted coupling reaction of alpha-tributylstannylthioacetals with enol silyl ethers followed by the treatment with potassium hydride or DBU in good yields.