Alkenylboranes, isomerization

The coupling of alkenylboranes with alkenyl halides is particularly useful for the stereoselective synthesis of conjugated dienes of the four possible double bond isomers[499]. The E and Z forms of vinylboron compounds can be prepared by hydroboration of alkynes and haloalkynes, and their reaction with ( ) or (Z)-vinyl iodides or bromides proceeds without isomerization, and the conjugated dienes of four possible isomeric forms can be prepared in high purity. 

Heterosubstituted alkenes undergo hydrozirconation. Hydrozirconation of aUcenyl-zirconiums is a suggested mechanism for isomerization of alkenylzirconiums, and 1,2-dizirconiums are known . Hydrozirconation of alkenylboranes and alkenyl-aluminums leads to both 1,1- and 1,2-dimetalated derivatives ... 

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