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Gold catalysed intermolecular atom transfer reactions on heteroatom-substituted alkynes

Cremonesi, Alex (2013)
Ph.D. thesis, University of Birmingham.

 Cremonesi13PhD.pdfPDF (8Mb)Restricted to Repository staff only until 31 December 2018.

Abstract

In this thesis the development of several novel gold-catalysed transformations are reported. Two intermolecular atom transfer processes have been designed and developed to access gold carbenoid reactivity. The latter reactive species allowed the synthesis of various α,ß-unsaturated carboxylic acid derivatives and trisubstituted oxazoles.
Numerous nitrogen- and oxygen substituted alkynes have been prepared and employed in oxygen transfer processes promoted by gold complexes. Using pyridine $$N$$-oxide, both ynamides and ynol ethers underwent regioselective intermolecular oxidation reactions under mild gold catalysis conditions. During the transformation, an α-oxo gold carbenoid intermediate is accessed which develops through a rapid 1,2-insertion reaction to yield α,ß -unsaturated imides and vinylogous carbimates.
The strategy has proved to be a valid alternative to the use of hazardous α-oxo diazo compound when carbene reactivity is desired. Appling a similar strategy, $$N$$-imido pyridonium ylides have been used as an $$O,N$$-dipole onto gold activated ynamides and ynol ethers. The overall [3+2] cyclisation occurred through a nitrene transfer process followed by a cycloisomerisation step. Under this approach, ynamides and ynol ethers have been converted into highly functionalised trisubstituted oxazoles. The mild gold catalysis conditions allowed the use of a wide range of functionality. Moreover, the α-imido gold carbenoid involved as a reaction intermediate displayed the possibility to utilise such protocol to access α-imido carbene reactivity

Type of Work: Ph.D. thesis. Davies, Paul Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Chemistry QD Chemistry University of Birmingham 4083
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