Edmunds, Andrew John Francis (1986) Stereochemical and trapping studies of biradicals. PhD thesis, University of Warwick.

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Abstract

The work in this thesis can be divided into two parts.

1) Stereochemical studies
Irradiation of cis-anti-5,6-[²H]₂-2,3-diazablcyclo[2.2.2]oct-2-ene (dg-DBO) leads to bicyclo[2.2.0]hexane (BCH) in which the deuterium is predominantly exo, i.e. double inversion of configuration, and hexa-1,5-diene (HD) with equal amounts of cis and trans deuterium. In addition, direct photolysis affords small amounts of cyclohexene formed via a stereoselective 1,3-shift. The proportions of EE-, EZ-, and ZZ-d₂-HD’s were not accessible by direct spectroscopic methods but could be obtained by a chemical method combined with mass spectrometry. Stereoselective substitution at the 1,6-positions, in which Z-deuterium was lost and E- deuterium retained, translated stereochemical information into deuterium content. The results of the analysis showed that the EZ-isotopomer was formed predominantly, but significant amounts of EE- and ZZ-isotopomers were also present. The results are compared to the pyrolysis stereochemistry of stereoselectively labelled d₂-BCH and the known stereochemistry for the deazetation of DBO. A mechanism is proposed that accounts for all the observations.

2) Trapping studies
While triplet biradicals have been intercepted by a wide range of biradical traps only one case of singlet biradicals, 2-alkylidenecyclopentane-l,3- diyls, are sufficiently long-lived to undergo intermolecular reactions. Related singlet biradicals have been proposed as intermediates in the photochemical rearrangement of a cyclic triene, 6-methylene-3,3- dimethylcyclohexa-1, 4-diene. When the triene was irradiated in the presence of olefins, 1:1 triene:olefin adducts could be isolated. Their structure was established by X-ray diffraction, spectroscopy, and independent synthesis. The mechanism of their formation is discussed.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Biradicals, Stereochemistry, Photochemistry
Official Date:	1986
Dates:	Date Event 1986 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Samuel, Christopher J.
Sponsors:	Science and Engineering Research Council (Great Britain)
Extent:	1 volume ([11], 323 leaves) : illustrations
Language:	eng

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