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Title: Lithiation chemistry of vinyl ureas
Author: Lefranc, Julien
ISNI:       0000 0004 2719 3332
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2011
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The construction of tertiary alkylamines is a synthetic challenge exacerbated by the poor electrophilicity of imines. Due to the presence of this kind of building block in a large number of bioactive molecules, the development of new strategies to synthesise the quaternary carbon centre is essential. This thesis describes the work carried out on the rearrangement of lithiated vinyl ureas in order to form α-tertiary amines. The first part presents how vinyl ureas were synthesised, using the reaction between an imine and an aryl isocyanate. The development of one-pot process allows the synthesis of a range of ureas in large scale. These vinyl ureas present unusual reactivity: the electron-rich double bond can undergo syn umpolung carbolithiation followed by retentive aryl migration in order to generate highly substituted amines after cleavage of the urea. The complete mechanism is investigated to understand fully the diastereoselective pathway of the reaction. In the next part, the rearrangement of lithiated ureas is extended to the N to C vinyl transfer. Different vinyl migrating group are investigated and α-tertiary amines have been synthesised in high yields and enantiomerically pure form using this new rearrangement. The mechanistic insights of the reaction are also studied and a retentive mechanism will be identified. Finally, N to C vinyl transfer is applied toward the synthesis of Erythrina alkaloids.
Supervisor: Clayden, Jonathan Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: alpha-tertiary amines ; Rearrangement ; Carbolithiation ; Stereospecific ; Enantioselective