Facile Synthesis of Dendralenes Based on the Cross-coupling Reaction of 2,3-Bis(pinacolato) boryl-1,3-butadiene

Palladium-catalyzed cross-coupling reaction of 2,3-diboryl-1,3-butadiene with an alkenyl halide or a dienyl halide allowed us to straightforwardly prepare various kinds of acyclic cross-conjugated polyenes that are referred to as dendralenes. The present method is applicable to the synthesis of not only symmetrical [4]- and [6]dendralenes but also unsymmetrical [3]- to [5] dendralenes.