Direct C-H α-Arylation of Enones with ArI(O2CR)2 Reagents

J Am Chem Soc. 2020 Jan 8;142(1):64-69. doi: 10.1021/jacs.9b11282. Epub 2019 Dec 27.

Abstract

α-Arylation of α,β-unsaturated ketones constitutes a powerful synthetic transformation. It is most commonly achieved via cross-coupling of α-haloenones, but this stepwise strategy requires prefunctionalized substrates and expensive catalysts. Direct enone C-H α-arylation would offer an atom- and step-economical alternative, but such reports are scarce. Herein we report the metal-free direct C-H arylation of enones mediated by hypervalent iodine reagents. The reaction proceeds via a reductive iodonium Claisen rearrangement of in situ-generated β-pyridinium silyl enol ethers. The aryl groups are derived from ArI(O2CCF3)2 reagents, which are readily accessed from the parent iodoarenes. The reaction is tolerant of a wide range of substitution patterns, and the incorporated arenes maintain the valuable iodine functional handle. Mechanistic investigations implicate arylation via an umpoled "enolonium" species and show that the presence of a β-pyridinium moiety is critical for the desired C-C bond formation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alkenes / chemistry*
  • Cyclization
  • Indicators and Reagents / chemistry*
  • Ketones / chemistry*
  • Metals / chemistry
  • Oxidation-Reduction

Substances

  • Alkenes
  • Indicators and Reagents
  • Ketones
  • Metals