Competing amination and C-H arylation pathways in Pd/xantphos-catalyzed transformations of binaphthyl triflates: Switchable routes to chiral amines and helicene derivatives

Aaron A. Ruch, Sachin Handa, Fanji Kong, Vladimir N. Nesterov, Dale R. Pahls, Thomas R. Cundari, Legrande M. Slaughter

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

A Pd(OAc)2/xantphos catalyst system was found effective for benzylaminations of binaphthyl 2-triflates bearing a variety of alkyl, benzyl, and substituted phenyl substituents at the 2′-position. With 2′-aryl substituents, an intramolecular Pd-catalyzed C-H arylation was observed as a competing side reaction under some conditions. By adjusting the solvent and quantity of the amine, the reaction was optimized to favor either the amination or the C-H arylation pathway, affording two distinct and potentially useful sets of products. The amines represent tunable chiral ligand precursors, while the C-H arylation pathway affords a series of benzofused [5]helicene derivatives. Kinetic studies and activation parameters for the C-H arylation pathway, supported by DFT calculations, are consistent with a concerted metalation-deprotonation (CMD) mechanism involving a Pd-bound carbonate as the base. Xantphos is proposed to facilitate the turnover-limiting inner-sphere CMD step by acting as a hemilabile ligand, while its wide bite angle engenders a low reductive elimination barrier.

Original languageEnglish (US)
Pages (from-to)8123-8140
Number of pages18
JournalOrganic and Biomolecular Chemistry
Volume14
Issue number34
DOIs
StatePublished - 2016

Bibliographical note

Publisher Copyright:
© 2016 The Royal Society of Chemistry.

Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.

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