Indole Synthesis by Controlled Carbolithiation of o-Aminostyrenes

Albane Kessler, Claire M. Coleman, Patchanee Charoenying, and Donal F. O'Shea*
Centre for Synthesis and Chemical Biology, Conway Institute, Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
J. Org. Chem., 2004, 69 (23), pp 7836–7846
DOI: 10.1021/jo048723e
Publication Date (Web): October 21, 2004
Copyright © 2004 American Chemical Society

Abstract

Abstract Image

An effective synthesis of the functionalized indole ring system has been developed from substituted o-aminostyrene starting material. Our methodology involves a novel cascade reaction sequence of alkyllithium addition to the styrene double bond and subsequent trapping of the intermediate organolithium with a suitable electrophile, followed by an in situ ring closure and dehydration to generate the indole ring. This new reaction sequence allows for the introduction of molecular diversity at all positions on the indole scaffold. The procedure was shown to be successful with a range of both C and N substituents on the o-aminostyrenes. The reaction sequence was tolerant to the reactivity range of alkyllithiums such as tert-, sec-, and n-butyllithium. The electrophiles used were DMF, which generated indole products with C-2 unsubstituted, and nitriles, which incorporated the nitrile substituent at C-2. The o-aminostyrene starting materials were generated by a Pd-catalyzed cross-coupling reaction of a vinyl boronic acid equivalent with the readily available substituted o-bromoanilines.

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History

  • Published In Issue November 12, 2004
  • Received July 25, 2004

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