ChemInform Abstract: Application of a Palladium‐Catalyzed C—H Functionalization/Indolization Method to Syntheses of cis‐Trikentrin A and Herbindole B.

Abstract

We describe herein formal syntheses of the indole alkaloids cis-trikentrin Aa nd herbindole Bf rom ac ommon meso-hydroquinone intermediate prepared by ar utheniumcatalyzed[ 2 + +2+ +1+ +1] cycloaddition that has not been used previously in natural product synthesis.K ey steps include as terically demanding Buchwald-Hartwig amination as well as au nique C(sp 3 )ÀHa mination/indole formation. Studies towardas elective desymmetrization of the meso-hydroquinone are also reported.Scheme 1. Retrosynthesis of herbindole Band cis-trikentrin A.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.

Palladium-Catalyzed Transformations of Alkyl C–H Bonds

“…252 Under the reaction conditions similar to the cross-coupling, Tf-protected 2-ethylanilines underwent intramolecular C(sp 3 )−H amination/indole formation in the absence of arylboron reagents, which found applications in syntheses of cis-trikentrin A and herbindole B (261). 253 The observed significant ligand acceleration in the β-C(sp 3 )−H olefination of alanine-derived amide 232 240 as well as γ-C(sp 3 )−H olefination of carboxylic acid derivatives 249 prompted us to investigate the feasibility of γ-C(sp 3 )−H olefination of alkyl amines through the development of pyridine-and quinoline-based ligands. The newly identified 3phenylquinoline (Ligand 21) was found to enable the olefination of Tf-protected simple alkyl amines 262 (Scheme 74).…”