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The oxidation of olefins promoted by transition metal complexes

The oxidation of olefins by transition metal complexes leading to epoxide or ketonic products has been reviewed, with an emphasis on non-free radical processes. The formation of cycloadducts by reaction of <u>bis</u> (triphenylphosphine )- platinum(O)dioxygen with the α,β-unsaturated carbonyl compounds <u>trans</u> but-2-enal, propenal, cyclohex-2-en-1-one, <u>exo</u> 2-methvlenecyclohexan-1-one and 3-phenylprop- 2-enal was investigated by H- and <sup>31</sup>P- nuclear magnetic resonance (n.m.r.). The cycloadducts derived from <u>trans</u> but-2-enal and propenal were thermally unstable in solution and further reacted to form stable, isolable complexes. The mechanism by which the cycloadduct <u>cis</u> [4-<u>trans</u>(prop-2-enyl )-1,1-bis( triphenyl - phosphine)platina-2,3» 5-trioxacyclopentane] , I , was transformed into <u>cis</u> [<u>trans</u>- (5-formyl-4-methyl)-1,1-bis(triphenylphosphine )platina-2 t 3-dioxacyclopentane] , II , was investigated by H- and H-n.m.r. utilising <u>trans</u> 4-[<sup>2</sup>H<sub>3</sub>]but-2-enal. A mechanism which involved both exchange of free <u>trans</u> but-2-enal with I and reaction to give II was proposed; a computer model, based upon numerical integration of the alternative rate equations was in good agreement with this proposition. The chemical reactivity of II with a variety of reagents was explored. In particular, the reaction of II with trifluoroacetic acid gave <u>trans</u> 2-formyl- 3-methyloxirane in high yield and stereoselectivity. The dynamic behaviour of <u>cis</u>[<i>bis</u>(triphenylphosphine)(2<sub>3</sub>,3'-m)(<u>trans</u> - but-2-enal )platinum(0)] was observed by variable temperature P-n.m.r. and explained by the interconversion of carbonyl rotamers. The preparation of iridium(I) olefin and peroxo complexes has been described Chloro<u>bis</u> triphenylphosphine) (1,2-m) (ethene )dioxygen iridium( I) , III , and related complexes were found to oxidise terminal olefins to their methyl ketones stoichiometrically, by a non-free radical process. The mechanism has been discussed.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:330362
Date January 1981
CreatorsJohn, Robert Alun
ContributorsBrown, John M.
PublisherUniversity of Oxford
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Sourcehttp://ora.ox.ac.uk/objects/uuid:9bc3b270-11ab-4a64-8659-b5ac117de6f6

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