Facile Synthesis and Palladium‐Catalyzed Cross‐Coupling Reactions of 2,3‐Bis(pinacolatoboryl)‐1,3‐butadiene

Abstract

Treatment of 1,1-bis(pinacolatoboryl)ethene with an excess of 1-bromo-1-lithioethene gave 2,3-bis(pinacolatoboryl)-1,3-butadiene in high yield. Palladium-catalyzed cross-coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)2/PPh3 and aqueous KOH to give 2,3-diaryl-1,3-butadienes in good yields. The coupling reaction with commercially available 4-acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one-pot manner. A variety of [3]- to [6]dendralenes were synthesized by palladium-catalyzed coupling of the diene or 1,1-bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields.