Issue 8, 2017

Mono-N-protected amino acid ligands stabilize dimeric palladium(ii) complexes of importance to C–H functionalization

Abstract

Mono-protected amino acid (MPAA) ligands are used in a number of Pd-catalyzed C–H functionalization reactions. MPAAs have been proposed to bind to Pd(II) via κ2-(N,O) coordination, but such binding has not yet been experimentally validated. Herein, we report the synthesis and detailed characterization of a series of MPAA complexes prepared via cyclopalladation of dimethylbenzylamine in the presence of MPAAs. The isolated complexes exist as μ-carboxylato (MPAA) bridged dimers and feature potential M–M cooperativity and secondary sphere hydrogen bonding. Selective MPAA coordination and relay of stereochemistry, previously suggested to uniquely result from κ2-(N,O) MPAA coordination, are both observed. The isolated MPAA complexes undergo C–C and C–X (X = Cl, Br, I) bond formation when treated with electrophiles used for catalytic C–H functionalization. Stoichiometric iodination of MPAA palladacycles was found to proceed via a dinuclear palladium species with one equivalent of iodine in the rate limiting transition structure, and the isolated complexes also served as viable precatalysts for catalytic C–H functionalization. Together, these results provide a number of insights into the reactivity of Pd-MPAA complexes relevant to C–H bond functionalization.

Graphical abstract: Mono-N-protected amino acid ligands stabilize dimeric palladium(ii) complexes of importance to C–H functionalization

Supplementary files

Article information

Article type
Edge Article
Submitted
14 Apr 2017
Accepted
15 Jun 2017
First published
16 Jun 2017
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2017,8, 5746-5756

Mono-N-protected amino acid ligands stabilize dimeric palladium(II) complexes of importance to C–H functionalization

J. J. Gair, B. E. Haines, A. S. Filatov, D. G. Musaev and J. C. Lewis, Chem. Sci., 2017, 8, 5746 DOI: 10.1039/C7SC01674C

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