CuH-Catalyzed Enantioselective Alkylation of Indole Derivatives with Ligand-Controlled Regiodivergence

J Am Chem Soc. 2019 Mar 6;141(9):3901-3909. doi: 10.1021/jacs.8b11838. Epub 2019 Feb 20.

Abstract

Enantioenriched molecules bearing indole-substituted stereocenters form a class of privileged compounds in biological, medicinal, and organic chemistry. Thus, the development of methods for asymmetric indole alkylation is highly valuable in organic synthesis. Traditionally, achieving N-selectivity in indole alkylation reactions is a significant challenge, since there is an intrinsic preference for alkylation at C3, the most nucleophilic position. Furthermore, selective and predictable access to either N- or C3-alkylated chiral indoles using catalyst control has been a long-standing goal in indole functionalization. Herein, we report a ligand-controlled regiodivergent synthesis of N- and C3-alkylated chiral indoles that relies on a polarity reversal strategy. In contrast to conventional alkylation reactions in which indoles are employed as nucleophiles, this transformation employs electrophilic indole derivatives, N-(benzoyloxy)indoles, as coupling partners. N- or C3-alkylated indoles are prepared with high levels of regio- and enantioselectivity using a copper hydride catalyst. The regioselectivity is governed by the use of either DTBM-SEGPHOS or Ph-BPE as the supporting ligand. Density functional theory (DFT) calculations are conducted to elucidate the origin of the ligand-controlled regiodivergence.

Publication types

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

MeSH terms

  • Alkylation
  • Catalysis
  • Copper / chemistry
  • Hydrogen / chemistry*
  • Indoles / chemical synthesis*
  • Indoles / chemistry
  • Ligands
  • Molecular Structure
  • Stereoisomerism

Substances

  • Indoles
  • Ligands
  • Copper
  • Hydrogen