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Issue 29, 2014
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Mechanistic insight into the ruthenium-catalysed anti-Markovnikov hydration of alkynes using a self-assembled complex: a crucial role for ligand-assisted proton shuttle processes

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Abstract

A combined computational and experimental study is presented that investigates the mechanism of the anti-Markovnikov hydration of phenylacetylene by [Ru(η5-C5H5)(6-DPPAP)(3-DPICon)]+ (where 6-DPPAP = 6-(diphenylphosphino)-N-pivaloyl-2-aminopyridine) and 3-DPICon = 3-diphenylphosphinoisoquinolone). The proposed mechanism, modelled using density functional calculations, involves an initial alkyne–vinylidene tautomerism, which occurs via a ligand-assisted proton shuttle (LAPS) mechanism. Intramolecular ligand assistance from the 6-DPPAP and 3-DPICon ligands, particularly the basic nitrogen of 6-DPPAP, is also involved in subsequent stages of the mechanism and three LAPS processes in total are observed. The self-assembled ligand backbone helps to create a water-binding pocket close to the metal centre, which facilitates nucleophilic attack of water at the vinylidene α-carbon and mediates protonation and deprotonation of subsequent acyl and vinyl intermediates. Experimental evidence is also presented for a novel non-productive catalyst deactivation pathway, which appears to arise from an initial lactam–lactim tautomerism of the 3-DPICon ligand followed by coupling with a vinylidene.

Graphical abstract: Mechanistic insight into the ruthenium-catalysed anti-Markovnikov hydration of alkynes using a self-assembled complex: a crucial role for ligand-assisted proton shuttle processes

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Publication details

The article was received on 10 Mar 2014, accepted on 06 May 2014 and first published on 15 May 2014


Article type: Paper
DOI: 10.1039/C4DT00712C
Author version available: Download Author version (PDF)
Citation: Dalton Trans., 2014,43, 11277-11285
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    Mechanistic insight into the ruthenium-catalysed anti-Markovnikov hydration of alkynes using a self-assembled complex: a crucial role for ligand-assisted proton shuttle processes

    B. Breit, U. Gellrich, T. Li, J. M. Lynam, L. M. Milner, N. E. Pridmore, J. M. Slattery and A. C. Whitwood, Dalton Trans., 2014, 43, 11277
    DOI: 10.1039/C4DT00712C

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