Nickel‐Catalyzed Regioselective Arylboration of Conjugated Dienes.

The nickel‐catalyzed arylboration of conjugated dienes is reported. Good 1,4‐regioselectivity and (E)‐stereoselectivity were obtained using isoprene, together with very good 1,2‐regioselectivity and (E)‐stereoselectivity using 1‐arylbutadienes. The high reactivity and selectivity of this process were dependent on the use of the appropriate nitrogen‐based ligand. Moreover, wide functional group tolerance was observed under mild reaction conditions. This protocol provides a path to allyl or homoallyl boronic ester derivatives starting from 1,3‐dienes, aryl bromides, and B2pin2. The downstream transformation of allyl boronic esters was also achieved, suggesting a strategy for the diastereoselective 1,2‐difunctionalization of isoprene and demonstrating the potential for the synthesis of complex molecules. [ABSTRACT FROM AUTHOR]