Gold-catalysed reactions of Nitrogen containing molecules

• Main Author: Martin, Nicolas
• Published: University of Birmingham 2010
• Subjects: 541.39; QD Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524882

The development of several new gold-catalysed reactions are described. Two new strategies have been employed to access pyrroles by the cycloisomerisation of alkynyl aziridines, and the formation of α,β-unsaturated imides by the oxidation of ynamides has been developed. A rare gold-mediated vinylidene rearrangement of brominated or silylated alkynes has been used to prepare brominated or silylated 2,4-substituted pyrroles regioselectively. The practical applicability of this process was limited by instability of products under the reaction conditions. Cationic gold catalysis was used in a synthesis of 2,4- and 2,5-substituted pyrroles from alkynyl aziridines. The role of counterion in these processes was studied and shown to be important in determining reaction outcomes. A Ph\(_3\)PAuCl/AgOTs catalyst system, allows 2,5-substituted pyrroles to be regioselectively synthesised in an atom-economical manner in near quantitative yield. From the same aryl-substituted starting materials the 2,4-substituted pyrrole isomer were accessed preferentially when a Ph\(_3\)PAuCl/AgOTf catalytic system was employed. A reaction mechanism accounting for the reaction outcome was proposed on the basis of \({^13}\)C- and deuterium-labelling studies. A new gold-catalysed synthesis of α,β-unsaturated imides was developed using a ynamide oxidation approach. Gold carbenoid intermediates can be formed regioselectively by action of an external oxidising agent, and were used in 1,2-insertion reactions.