Alkenylboron derivatives, coupling with alkenyl halides

Alkenylboron compounds couple with the representative organic halides or triflates (Scheme 28). Hexaalkylbenzene was synthesized by sixfold alkenylation (55) of hexabromobenzene followed by catalytic hydrogenation of the double bonds 11521. The reaction of 1-alkenylborane with 1-bromo-l-alkyne stereose-lectively provided ( )-enyne (56) which was then converted into ( ,Z)-hexa-deca-10,12-dienal, a sex pheromone of the melonworm 11531. Due to the difficulty of purification of a geometrical mixture, the stereoselective synthesis is critical for such dienes or trienes. The PGEi derivatives (57) were synthesized... 

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