Studies on the generation and use of functionalised organozinc carbenoids for the synthesis of aminocyclopropanes and related congeners
The present thesis describes a range of studies on the generation and reactivity of organozinc carbenoid species possessing adjacent nitrogen functionality for the preparation of aminocyclopropanes and related congeners. This thesis opens with two distinct introductory reviews. The first one focuses on the description of the different general methods already available for the synthesis of aminocyclopropanes. The second one is concerned with the generation and reactivity of organozinc carbenoids encountered in the literature. The results and discussion chapter firstly describes the successful generation of an organozinc carbenoid from an acetal moiety contiguous to a nitrogen atom of a simple cyclic amide using a mixture of zinc amalgam and chlorotrimethylsilane. This new organometallic species is found to undergo cyclopropanation reactions with a range of alkenes to yield amidocyclopropanes. Subsequent studies directed towards the design of carbenoid precursors which can lead to the preparation of primary aminocyclopropanes are then discussed. A method for the synthesis of chiral protected aminocyclopropanes in two steps from their corresponding alkenes is described. An investigation of the preparation of N-substituted cyclopropyl amino alcohols and acids is presented. From this study, an N-substituted cyclopropyl glycine derivative is prepared. Finally, this thesis discusses the attempted palladium-catalysed cross-coupling reactions between amino cyclopropylsilanes and aryl iodides and the successful Tamao-Fleming oxidation of the carbon-silicon bond of vicinal amino cyclopropylsilanols to give the corresponding amino cyclopropanols. The thesis terminates with a full description of the experimental procedures used and the compounds prepared.