Synthesis of Symmetrical (E,E)-1,4-Diaryl-1,3-butadienes by One-Pot Method

1,3-Conjugated olefins are very useful synthetic intermediates. Furthermore, 1,3-diene moiety is an important unit often found in many polymers, natural products and biologically active compounds. For these reasons, the design and synthesis of compounds containing a diene moiety have received considerable attention in organic synthesis and have been extensively studied. Among these methods, the Heck cross-coupling reaction between alkenyl halide and terminal alkene under palladium catalysis has become a powerful tool for the synthesis of dienes. Recently, many research groups have focused on "one-pot method" cascade reactions to form carbon-carbon bond due to not only their convenient and simple operation, but also their high atomic economy. Using terminal alkyne and bis(pinacolato)diboron as starting materials and NaOMe as the base, alkenyl borates were formed, and a series of 1,3-butadienes were directly synthesized via palladium-catalyzed homocoupling reaction of alkenyl borates. The structures of all the compounds were confirmed by H-1 NMR and C-13 NMR. This one pot method is simple and mild, which provides a simple way for the synthesis of a series of 1,3-butadienes.