The cross-coupling of aryl esters has emerged as a powerful platform for the functionalization of otherwise inert acyl C–O bonds in chemical synthesis and catalysis. Herein, we report a combined experimental and computational study on the acyl Suzuki–Miyaura cross-coupling of aryl esters mediated by well-defined, air- and moisture-stable Pd(II)–NHC precatalysts [Pd(NHC)(μ-Cl)Cl]2. We present a comprehensive evaluation of [Pd(NHC)(μ-Cl)Cl]2 precatalysts and compare them with the present state-of-the-art [(Pd(NHC)allyl] precatalysts bearing allyl-type throw-away ligands. Most importantly, the study reveals [Pd(NHC)(μ-Cl)Cl]2 as the most reactive precatalysts discovered to date in this reactivity manifold. The unique synthetic utility of this unconventional O–C(O) cross-coupling is highlighted in the late-stage functionalization of pharmaceuticals and sequential chemoselective cross-coupling, providing access to valuable ketone products by a catalytic mechanism involving Pd insertion into the aryl ester bond. Furthermore, we present a comprehensive study of the catalytic cycle by DFT methods. Considering the clear advantages of [Pd(NHC)(μ-Cl)Cl]2 precatalysts on several levels, including facile one-pot synthesis, superior atom-economic profile to all other Pd(II)–NHC catalysts, and versatile reactivity, these should be considered as the ‘first-choice’ catalysts for all routine applications in ester O–C(O) bond activation.
|Original language||English (US)|
|Journal||Catalysis Science & Technology|
|State||Published - Mar 25 2021|
Bibliographical noteKAUST Repository Item: Exported on 2021-04-02
Acknowledgements: We thank Rutgers University, the NSF (CAREER CHE-1650766), and the NIH (1R35GM133326) for generous financial support. Supplement funding for this project was provided by the Rutgers University – Newark Chancellor's Research Office. The 500 MHz spectrometer used in this study was supported by the NSF-MRI grant (CHE-1229030). A. P. is a Serra Húnter Fellow, and ICREA Academia Prize 2019, and thanks the Spanish MINECO for a project PGC2018-097722-B-I00, and European Fund for Regional Development (FEDER) grant UNGI10-4E-801. S. P. N thanks the BOF research fund as well as the SBO projects CO2perate and D2M for financial support.
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