A Highly Selective Catalytic System for the Cross-Coupling of (E)-Styryl Bromide with Benzeneboronic Acid: Application to the Synthesis of All-Trans Poly(arylenevinylene)s

作者：Wakioka Masayuki; Mutoh Yuichiro; Takita Ryo; Ozawa Fumiyuki^*

来源：Bulletin of the Chemical Society of Japan, 2009, 82(10): 1292-1298.

DOI：10.1246/bcsj.82.1292

A highly selective system for palladium-catalyzed polycondensation of (E,E)-1,4-bis(2-bromoethenyl)benzene ((E,E)-1) with 2,5-dioctyloxybenzene-1,4-diboronic acid (2a) to give all-trans poly[(p-phenylenevinylene)-alt-(2,5-dioctyloxy-1,4-phenylenevinylene)] (all-trans 3) has been investigated using (E)-styryl bromide ((E)-4) and 2,5-dioctyl-oxybenzeneboronic acid (5a) as model compounds of (E,E)-1 and 2a, respectively. The reaction of (E)-4 and 5a in toluene in the presence of Pd(PPh3)(4) catalyst and aqueous K2CO3 base affords considerable amounts of homocoupling products (i.e., 1,4-diphenylbutadiene (13%) and 2,2',5,5'-tetraoctyloxybiphenyl (22%)), together with (E)-2,5-dioctyl-oxystilbene ((E)-6a) as the cross-coupling product (30%). The use of aqueous NaOH as a strong base and Bu4NBr as a phase-transfer catalyst notably reduces the homocoupling products, and the use of Pd(PBu'(3))(2) instead of Pd(PPh3)(4) results in almost perfect selectivity of the cross-coupling product (E)-6a. Under optimized catalytic conditions, the desired all-trans 3 has been successfully prepared without notable defects in the polymer chain.

• 出版日期2009-10-15