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Title: Higher-order cycloisomerisations of enynamides
Author: Straker, Robert N.
ISNI:       0000 0004 6496 3674
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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This thesis describes the development of a novel transformation of ynamides, and addresses more general questions of asymmetric cycloisomerisation. The rhodiumcatalysed [5+2] cycloisomerisation of ynamide vinylcyclopropanes A1 to [5.3.0]- heterobicycles A2 is established (Scheme i). We design a versatile substrate synthesis, which allows the preparation of diversely substituted enynamide substrates. Under achiral rhodium catalysis, the extent of substrate diastereo- and regioselectivity is investigated. The reaction is rendered asymmetric with the use of chiral phosphoramidite ligands; where a mechanistic hypothesis for stereoselectivity leads to the development of a powerful catalyst system for the preparation of enantioenriched A3. A theoretical reaction analysis elucidates the mechanistic pathway, and gives an energetic rationale for our model of ligand stereoinduction. Our asymmetric catalyst system is applied to the [5+2] cycloisomerisation of chiral substrates in double stereodifferentiating transformations, where it is possible to synthesise previously inaccessible diastereomers of product A4.
Supervisor: Anderson, Edward Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available