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Palladium-Catalyzed Cross-Coupling Reaction of Bis(pinacolato)diboron with 1-Alkenyl Halides or Triflates: Convenient Synthesis of Unsymmetrical 1,3-Dienes via the Borylation-Coupling Sequence

Jun Takagi, Kou Takahashi, Tatsuo Ishiyama* and Norio Miyaura

*Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan, Email: ishiyamaorg-mc.eng.hokudai.ac.jp

J. Takagi, K. Takahashi, T. Ishiyama, N. Miyaura, J. Am. Chem. Soc., 2002, 124, 8001-8006.

DOI: 10.1021/ja0202255



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Abstract

1-Alkenylboronic acid pinacol esters have been synthesized via a palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with 1-alkenyl halides or triflates in toluene at 50°C in the presence of KOPh in high yields with complete retention of configuration of the double bonds. A one-pot synthesis of unsymmetrical 1,3-dienes via the borylation-coupling sequence has been developed.

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Details

The study presents a palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with 1-alkenyl halides or triflates to synthesize 1-alkenylboronic acid pinacol esters. Conducted in toluene at 50 °C with KOPh and PdCl2(PPh3)2-2Ph3P, the reaction achieves high yields with complete retention of double bond configuration. This method overcomes limitations of traditional hydroboration and transmetalation techniques, offering a one-pot synthesis of unsymmetrical 1,3-dienes via a borylation-coupling sequence. The process tolerates various functional groups and provides a versatile route for synthesizing 1-alkenylboronates, which are valuable intermediates in organic synthesis. The study demonstrates the method's utility through the synthesis of diverse 1,3-dienes, highlighting its efficiency and selectivity. The reaction conditions, including the use of KOPh and toluene, are optimized to suppress byproduct formation and enhance yields. This approach offers a practical and efficient alternative for preparing 1-alkenylboronates and 1,3-dienes, expanding the toolkit for synthetic organic chemists.


Key Words

Miyaura Borylation, Vinyl Boronates, Suzuki Coupling, 1,3-Dienes


ID: J48-Y2002-1200