Aqil, Rehan; (2002) Studies on the generation and reactivity of metal carbenoids. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis concerns the generation of metal carbenoids, in particular organozinc carbenoids, and their subsequent reactions, such as C-H insertion reactions or cyclopropanation with alkenes. The thesis is divided into three major sections. The introductory chapter presents a comparative review covering metal carbenoid species. The review focuses on how their reactivity is controlled by the metal, the leaving group and by the nature of electron-donating and -withdrawing groups on the carbenoid and finally which type of alkenes give the highest reactivity and yields as a function of these parameters. The results and discussion chapter opens with a brief overview of the organozinc carbenoid chemistry which has been developed within our group. Subsequent sections then describe a range of reactions which were investigated. Thus, studies on both the acid catalysed chlorotrimethylsilane-zinc deoxygenation of ketones and the use of iodotrimethylsilane-zinc for reactive carbenoid generation are presented and used in an investigation of transannular insertion in small, medium and large ring sized ketones. The first efforts towards electrochemical generation of organozinc carbenoids for dicarbonyl coupling are then described. This is followed by a detailed study of the regio-and stereoselective behaviour of electron rich dienes with a range of organozinc carbenoids generated from appropriate aldehydes and ketones. An investigation of both zinc and copper carbenoids in carboalkoxy- cyclopropanations is then presented. In addition, the generation of a novel geminally substituted alkoxy-carboalkoxy copper carbenoid was also examined and used for cyclopropanation. Attempts to generate metal carbenoids from halo iminium salts for aminocylopropanation are also discussed. This is followed by a chapter summarising the results achieved and perspectives for future work. A concluding chapter provides a formal description of the experimental results and procedures together with appropriate references.

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