SYNTHESIS OF STEREOISOMERICALLY PURE (E)-1,5-DIYN-3-ENES AND (E)-1-BROMO-3-YN-1-ENES BY DIASTEREOSELECTIVE PALLADIUM-CATALYZED CROSS-COUPLING REACTION OF 1-ALKYNYLZINC CHLORIDES WITH A STEREOISOMERIC MIXTURE OF 1,2-DIBROMOETHYLENE.
In the stereospecific palladium-catalyzed cross coupling reaction of 1-alkynylzinc chlorides, (E)-1,2-dibromoethylene reacts preferentially in the presence of (Z)-1,2-dibromo-ehylene.Productcs of di- or mono substitution can be obtained according to the ratio of reagents.