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Title: Carbenoid insertion into zirconacycles
Author: Norton, David
ISNI:       0000 0001 3449 7930
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2004
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Insertion of E-1,2-dihalo-1-lithioethene into zirconacyclopentenes formed methylenecyclopentenes. The mechanism proposed involves initial formation of an alkyne that then inserts intramolecularly into a carbon-zirconocenium bond. Stable alcohol products have been formed from hydroboration of the exocyclic double bond followed by basic peroxide quench. The same methylenecyclopentenes were formed from insertion of 1-lithio-2-haloethynes via a novel zirconocene vinylidene. Insertion of the carbenoid into a zirconacyclopentane formed an alkyne, but also showed for the first time that a neutral zirconium species will rearrange to incorporate a carbenoid fragment at room temperature, in this case forming a bis-insertion product. Intramolecular carbenoid insertion was attempted, but the area of research failed to give positive results. Some substrates with carbon-chlorine bonds were found to be incompatible with the zirconium cyclisation method. The range of vinyl carbenoids inserted into zirconacyclopentanes and - enes has been extended. Novel polyinsertion of vinyl carbenoids into the same side of zirconacyclopentanes has been discovered, revealing the fluxionality of the intermediate zirconate species. A novel rearrangement of zirconacyclohexane to form phenyl substituted methylenecyclopentenes has also been discovered. The first insertion of carbon monoxide into a zirconacyclohexane to form a cyclohexanone is reported. The insertion of phenylsulfone or vinyl carbenoids followed by butyl isocyanide has been found to form functionalised cyclohexanones after acidic quench. The 'one pot' formation of a bicyclic cycloheptanone from an acyclic precursor, with five new regioselectively formed carbon-carbon bonds, was discovered; thus revealing the degree of elaboration possible with organozirconium chemistry.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available