Differential Dihydrofunctionalization of Terminal Alkynes: Synthesis of Benzylic Alkyl Boronates through Reductive Three-Component Coupling

J Am Chem Soc. 2019 Apr 17;141(15):6173-6179. doi: 10.1021/jacs.9b02372. Epub 2019 Apr 3.

Abstract

The differential dihydrofunctionalization of terminal alkynes is accomplished through the reductive three-component coupling of terminal alkynes, aryl halides, and pinacolborane. The transformation results in hydrofunctionalization of both π-bonds of an alkyne in a single reaction promoted by cooperative action of a copper/palladium catalyst system. The differential dihydrofunctionalization reaction has excellent substrate scope and can be accomplished in the presence of esters, nitriles, alkyl halides, epoxides, acetals, alkenes, aryl halides, and silyl ethers. Mechanistic experiments indicate that the reaction proceeds through copper-catalyzed hydroboration followed by a second hydrocupration. The resulting heterobimetallic complex is the key intermediate that participates in the subsequent palladium-catalyzed cross-coupling, which furnishes benzylic alkyl boronate products.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Alkynes / chemistry*
  • Benzene Derivatives / chemical synthesis*
  • Benzene Derivatives / chemistry
  • Boronic Acids / chemical synthesis*
  • Boronic Acids / chemistry
  • Molecular Structure

Substances

  • Alkynes
  • Benzene Derivatives
  • Boronic Acids