Facile Synthesis of Dendralenes Based on the Cross-coupling Reaction of 1,1-Diborylethene and 2,3-Diboryl-l,3-butadiene

摘要

Palladium-catalyzed cross-coupling reaction of 1,1-diborylethene and 2,3-diboryl-l,3-butadiene with an alkenyl halide or a dienyl halide allows us to simply prepare various kinds of acyclic cross-conjugated polyenes that are called as dendralenes.The present method is applicable to the synthesis of not only symmetrical [3]-to [6]dendralenes but also unsymmetrical [4]-and [5]dendralenes.UV spectra of the dendralenes prepared exhibited no bathochromic shift of absorption maxima,suggesting that the polyenes adapted nonplanar conformations in a ground state.