Transition metal-catalyzed reactions of heteroatom-substituted alkynes

Identificador:  TDX:3389

Handle: https://hdl.handle.net/20.500.11797/TDX3389

Autors:  Zanini, Margherita

Resum:
Homogeneous gold(I) catalysis is a powerful tool for the construction of molecular complexity under mild conditions by mean of the selective activation of C-C multiple bonds. Our group developed a series of gold(I)-catalyzed reactions of alkynes with alkenes both in intramolecular and intermolecular settings. These reactions start with the nucleophilic attack of the double bond on the alkyne to form a cyclopropyl gold(I) carbene intermediate that than rearranges into a variety of products. In this Doctoral Thesis we present a series of new gold(I)-catalyzed intermolecular reactions of heteroatom-substituted alkynes with alkenes and the mechanistic investigation we performed by means of experimental work and DFT calculations. In the gold(I) catalyzed reactions of bromoalkynes with alkenes, the 1-bromo-cyclopropyl gold(I) carbene initially formed rearranges into gold(I) vinylidenes and vinylidenephenonium gold(I) cations passing through a cyclic bromonium intermediate. DFT calculations demonstrated that these two reactive intermediates are conformers of the same species but have different reactivity. On one side gold(I)-vinylidenes can undergo hydroarylation or C-H insertion, while vinylidenephenonium gold(I) cations easily undergo 1,2-aryl shift forming a triple bond. Moreover, we found that terminal alkynyl ethers are undergoing efficiently [2+2] cycloaddition with alkenes to form cyclobutene derivatives that can be easily transformed into the corresponding cyclobutanones.