Mechanistic insights into the malonoyl peroxide syn-dihydroxylation of alkenes

Rawling, Michael and Rowley, Julian and Campbell, Matthew and Kennedy, Alan and Parkinson, John and Tomkinson, Nick (2014) Mechanistic insights into the malonoyl peroxide syn-dihydroxylation of alkenes. Chemical Science, 2014 (5). pp. 1777-1785. ISSN 2041-6520

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Abstract

A detailed mechanistic understanding of the malonoyl peroxide mediated dihydroxylation of alkenes is presented. The reaction is first order in both alkene and peroxide with stoichiometric water playing a dual role. An ionic mechanism is proposed and supported by the use of 18O isotopically labelled peroxide, a radical clock probe and DFT calculations. Hammett analysis suggests the reaction proceeds via a discrete carbocation intermediate which is consistent with the stereochemical outcome of the transformation. A subsequent Woodward-type 1,3-dioxolan-2-yl cation has been trapped in situ and the mechanism of hydrolysis defined by isotopic labelling studies. Stable reaction intermediates have been isolated and characterised by X-ray crystallographic analysis and minor competing reaction pathways identified.