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Rearrangement and trapping of organozinc carbenoids.

O'Mahony, Donogh John Roger; (1995) Rearrangement and trapping of organozinc carbenoids. Doctoral thesis (Ph.D.), University College London. Green open access


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This thesis is divided into six chapters. Chapter one presents a review on metallocarbenoid chemistry and is divided into three parts. The first part gives a general survey of the influence of substituents on the reactivity and stability of free carbenes. The second part describes the reactions of transition metal carbenoids, particularly in relation to the oxidation state of the metal and the stoichiometry of carbenoid generation. The final part discusses the reactions of zinc carbenoids and the means of their formation. Chapter two is prefaced by a review on the generation and reactivity of organozinc carbenoids within the group, coupled with a mechanistic study of their formation. Studies on the hydrogen migration in open chain and more rigid cyclic ketone derived zinc carbenoids are presented. The organozinc carbenoids were shown to exhibit greater overall selectivity for the more thermodynamically favoured alkene isomer. Finally, the one-step conversion of aldehydes to terminal alkenes is presented. This conversion is shown to be accelerated by the addition of Lewis acids, particularly zinc chloride. Chapter three describes the direct one-pot conversion of acetals and ketals to organozinc carbenoids. It was found that carbenoids could be prepared efficiently from ketals containing the 1,3-dioxane, 1,3-dioxolane or dimethoxy moiety. However, for the acetal derivatives, only the dimethoxy and 1,3-dioxolane acetals could be readily reduced to the carbenoid. In chapter four, the carbenoids derived from aromatic aldehydes were shown to cyclopropanate olefins, and a brief study some of the steric and electronic effects of the alkene component is presented. The derived dimethoxy and 1,3-dioxolane acetals were also shown to cyclopropanate some simple olefins, with the syn:anti ratio dependant on the amount of added zinc chloride. Chapter five concludes the results and discussion, and gives a perspective to further work. Chapter six provides a formal description of the experimental results and procedures.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: Rearrangement and trapping of organozinc carbenoids.
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10104173
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