Austin, Carolyn Ann
(2006)
Diversity-based synthesis of nitrogen heterocycles.
PhD thesis, University of Glasgow.
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Abstract
Brief investigations were carried out towards the synthesis of 2,4-disubstituted quinolines and 2,6-disubstituted piperidines using titanium alkylidene chemistry, but these were unsuccessful. A route towards the diversity based stereoselective synthesis of 2-substituted azepane derivatives was explored via titanium alkylidene chemistry. Thioacetals i were reacted with low valent titanium(II) species ii to produce titanium(IV) alkylidenes that were reacted with resin-bound esters iii. Cleavage of the resulting enol ethers led to a small library of amino ketones iv, but reductive amination to give azepanes, remained elusive. However, hydrogenation of the phenylethylamino group in ketones iv gave racemic azepanes v. [diagram] Diversity based synthesis of cyclic imines, both 6 and 7 membered, has been carried out using trityl protected amines vi and vii. Alkylidene formation followed by reaction with a range of resin-bound esters iii gave enol ethers. Cleavage and deprotection under mild acidic conditions followed by treatment with base cyclised aminoketone products to cyclic imines viii and ix. [diagram].
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