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Abstract

The object of these studies is to contribute to the continuing development of the use of the diazo group in synthesis. Diazocarbonyl compounds were chosen owing to their relative ease of synthesis, their stability and because the carbonyl group is excellent for further bond building.

Literature reviews of the chemistry of 2-diazo-l,3-dicarbonyl compounds and of cyclopropanones are presented. An efficient synthesis of 3-diazopentane-2,4-dione has been developed and the chemistry of this compound has been examined. It has proved to be very sluggish in carbenoid reactions and gives poor yields of cyclopropanation products with olefins. Attempts to oxidise the resulting 1,1-diacetylcyclopropanes and similar canpounds in order to furnish cyclopropanone equivalents were unsuccessful.

The reported reactions of diazo canpounds with thiophenes are reviewed in detail and possible mechanisms for product formation are discussed. The reactions of 3-diazopentane-2,4-dione and related diazo canpounds with thiophenes have been examined and it has been shown that in special cases, 2H-thiopyran can be formed. A feasible mechanism for their formation is demonstrated to be via the cyclization of intermediate 2Z-dienethials. The latter canpounds are potentially useful intermediates in a general route to 2H- thiopyrans, but owing to their difficulty of synthesis it did not prove possible to develop such a route.

Following a review of asymmetric induction reactions, it is shown that copper canplexes of 3-trifluoroacetyl-d-camphor (facam) and sone of its derivatives are efficient chiral catalysts for cyclopropanation with a high degree of asymmetric induction. The copper complex of an immobilized, silica bonded version of facam was also shown to be very efficient for this purpose, offering the prospect for easy recovering and recycling of the catalyst.

The chemistry of 2-diazoamides is reviewed and attempts to improve the synthesis of 2-diazo-3-phenylpropanoic acid N,N- dimethylamide are described. This 2-diazoamide failed to give a 2H- thiopyran on reaction with thiophene. A review is then presented of the synthesis of benzothiophenes. The acetylation and cyclisation of 2-thienyl-l,3-dicarbonyl compounds (formed by condensation of thiophene with 2-diazo-l,3-dicarbonyl compounds) is shown to lead, in sane cases, to benzothiophenes, but yields were too low to make the route of much practical value.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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