Palladium-catalyzed, modular synthesis of highly functionalized indoles and tryptophans by direct annulation of substituted o-haloanilines and aldehydes

J Org Chem. 2006 Sep 29;71(20):7826-34. doi: 10.1021/jo061471s.

Abstract

One-pot synthesis of indoles by a palladium-catalyzed annulation of ortho-haloanilines and aldehydes has been developed. Coupling of ortho-iodoaniline with aldehyde is realized under mild ligandless conditions [Pd(OAc)2, DABCO, DMF, 85 degrees C], whereas X-Phos is found to be the ligand of choice for coupling reactions involving ortho-chloroanilines/ortho-bromoanilines and aldehydes. A variety of ortho-haloanilines with different electronic properties are suitable substrates, and aldehydes including chiral ones participated in this reaction without racemization. Coupling of (S)-2-N,N-di-tert-butoxycarbonyl-5-oxopentanoate, derived from L-glutamic acid, with ortho-haloanilines provides a rapid access to the ring-A-substituted tryptophans in good to excellent yields.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aldehydes / chemistry
  • Aniline Compounds / chemistry
  • Catalysis
  • Indoles / chemical synthesis*
  • Palladium / chemistry
  • Tryptophan / analogs & derivatives*
  • Tryptophan / chemical synthesis

Substances

  • Aldehydes
  • Aniline Compounds
  • Indoles
  • Palladium
  • Tryptophan