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Why does the synthesis of N-phenylbenzamide from benzenesulfinate and phenylisocyanate via the palladium- mediated extrusion–insertion pathway not work? A mechanistic exploration

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Version 2 2024-11-03, 23:17
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journal contribution
posted on 2024-11-03, 23:17 authored by Y Yang, Allan CantyAllan Canty, RAJ O'Hair

The gas-phase extrusion–insertion (ExIn) reactions of the palladium complexes [(phen)nPd(O2SC6H5)]+ (phen = 1,10-phenanthroline, n = 1 or 2), were investigated in the gas phase by multistage mass spectrometry (MSn) experiments consisting of electrospray ionisation and a linear ion trap combined with density functional theory (DFT) calculations. Desulfination of palladium sulfinate cations under collision-induced dissociation (CID) generates the organopalladium intermediates [(phen)nPd(C6H5)]+. Of these two organometallic cations, only [(phen)Pd(C6H5)]+ reacts with phenyl isocyanate via insertion to yield [(phen)Pd(NPhC(O)C6H5)]+. The formation of a coordinated amidate anion is supported by DFT calculations. In exploring this reactivity in the solution phase, we found that heating a mixture of benzenesulfinic acid, phenylisocyanate and palladium trifluoroacetate under a range of different conditions (ligand free versus with ligand, different solvents, addition of acid or base) failed to lead to the formation N-phenyl-benzamide in all cases. Instead, biphenyl was formed and could be isolated in a yield of 46%. DFT calculations using a solvent continuum reveal that the barrier associated with the insertion reaction lies above the competing sequential reactions of desulfination of a second phenyl sulfinate followed by reductive elimination of biphenyl.

History

Publication title

Australian Journal of Chemistry

Volume

76

Issue

1

Pagination

49-57

ISSN

0004-9425

Department/School

Chemistry

Publisher

C S I R O Publishing

Publication status

  • Published

Place of publication

150 Oxford St, Po Box 1139, Collingwood, Australia, Victoria, 3066

Rights statement

© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License, https://creativecommons.org/licenses/by-nc-nd/4.0/

Socio-economic Objectives

280105 Expanding knowledge in the chemical sciences