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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:330362 |
| Date | January 1981 |
| Creators | John, Robert Alun |
| Contributors | Brown, John M. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:9bc3b270-11ab-4a64-8659-b5ac117de6f6 |
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