Details of Grant 

EPSRC Reference:	GR/S62659/01
Title:	Mechanistic Studies on Prins-Type Cyclisations for the Stereocontrolled Synthesis of Heterocycles
Principal Investigator:	Willis, Professor C
Other Investigators:	Alder, Professor R
Researcher Co-Investigators:
Project Partners:
Department:	Chemistry
Organisation:	University of Bristol
Scheme:	Standard Research (Pre-FEC)
Starts:	02 February 2004	Ends:	01 February 2007	Value (£):	96,896
EPSRC Research Topic Classifications:	Chemical Synthetic Methodology Physical Organic Chemistry
EPSRC Industrial Sector Classifications:	Chemicals
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Panel History:
Summary on Grant Application Form
Oxygen- and nitrogen-containing heterocycles feature in many biologically active compounds and developing efficient strategies for their synthesis remains an important goal. Cyclisations of homoallylic alcohols and aldehydes under acidic conditions lead to the stereocontrolled synthesis of tetrahydropyrans with the creation of up to 3 asymmetric centres in a single-pot process. The mechanism is not simple however and we have shown that starting with enantioenriched benzylic homoallylic alcohols, the enantiopurity of the product is dependent upon the substituents on the aromatic ring. We propose that a chair 4-tetrahydropyyansl cation with an unusual structure is a common intermediate in these Prins cyclisations and associated oxoniaCope rearrangements and that related intermediates are involved in Grob fragmentations. These proposals rest on calculations, and this project aims to subject them to appropriate experimental tests For example, the integrity of these novel intermediates and the effects of substituents on cation stability will be investigated, analogues of sufficient stability for observation by NMR will be designed and synthesised and factors controlling fragmentation versus cyclisation of oxonium and iminium ions will be determined. An improved mechanistic understanding should lead to a rational design of efficient enantioselective svntheses of substituted tetrahvdroovrans and oineridines.
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Organisation Website:	http://www.bris.ac.uk