Novel and Convenient Method for the Stereo- and Regiospecific Synthesis of Conjugated Alkadienes and Alkenynes via the Palladium-Catalyzed Cross-Coupling Reaction of 1-Alkenylboranes with Bromoalkenes and Bromoalkynes

Article abstract of DOI:10.1021/ja00290a037

Details of a new and general method for the stereo- and regiospecific synthesis of conjugated alkadienes and alkenynes are described.The reaction of (E)- or (Z)-1-alkenyldisiamylboranes, or 2-((E)-1-alkenyl)-1,3,2-benzodioxaboroles readily obtainable by hydroboration, with either (E)- or (Z)-1-alkenyl bromides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium and bases such as sodium alkoxides gives the corresponding (E,E)-, (E,Z)-, (Z,E)-,or (Z,Z)-conjugated alkadienes stereo- and regiospecifically, while retaining the configurations of both the strating alkenylboranes and bromoalkenes.The reaction of (E)- and (Z)-1-alkenyldisiamylboranes with 1-bromoalkynes similarly provides a stereo- and regiospecific synthesis of conjugated (E)- and (Z)-alkenynes.A mechanism of this cross-coupling reaction, which involves the transmetalation between a 1-alkenylborane and an alkoxypalladium(II) complex generated through the metathetical displacement of a halogen atom from R(Pd(II)X with sodium alkoxide, is proposed.