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Silenes: Novel Reagents for Organic Synthesis

CZYZEWSKI, MICHAL (2010) Silenes: Novel Reagents for Organic Synthesis. Doctoral thesis, Durham University.



Whilst silenes have long been studied for their unique chemistry there has been little attempt to exploit this in other synthetic strategies. As part of a programme to explore this aspect the reactions of readily accessible silenes with alkenes and dienes were studied.
Silenes, generated by the thermolysis of acylpolysilanes, add to α,β-unsaturated esters to form silacyclobutanes and silyl-substituted cyclopropanes in moderate yields. Upon silicon-carbon bond oxidation the cyclopropanes were converted directly to 1,4-dicarbonyl compounds, thus demonstrating the formal acyl anion chemistry of acylpolysilanes.
In an alternative approach towards milder silene generation, the potential of α-silyl diazo carbonyl compounds was examined. It was found that α-silyl diazo esters undergo rhodium (II) catalysed decomposition to provide short-lived silenes. These intermediates rearrange to oxasilates which can be trapped with α,β-unsaturated ketones. The resulting products contain a high degree of functionality which offers considerable potential for further synthetic transformations.
Finally, more complex skeletons were approached through an exploration of intramolecular silene cycloaddition. In this respect, it was shown that thermolysis of acylpolysilanes at 180 oC produced [4+2] cycloadducts, while [2+2] cycloadducts and ‘ene’ products were not observed. Similarly, it was found that intramolecular cycloadducts can be generated at lower temperatures by the addition of MeLi•LiBr to acylpolysilanes. These two approaches allowed the cycloadducts to be synthesised in good yields and moderate diastereoselectivities.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Keywords:organosilicon chemistry, silene, cycloaddition
Faculty and Department:Faculty of Science > Chemistry, Department of
Thesis Date:2010
Copyright:Copyright of this thesis is held by the author
Deposited On:01 Nov 2010 14:53

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