Gold-Catalyzed Cycloisomerization Reactions Through Activation of Alkynes

New Developments and Mechanistic Studies

Antoine Simonneau's thesis highlights the development of new cycloisomerization reactions through the activation of alkynes with gold complexes. First Simonneau describes 1,6-enynes and their direct conversion into allenes through 1,5-hydride or ester migration processes. The author and his team used appropriate propargylic functional groups to achieve this conversion. This study shows that O-tethered 1,6-enynes carrying a strained cycloalkane at the propargylic position could undergo a cyclopropanation/ring expansion cascade reaction. The author employed this rearrangement as the starting point in the design of a new macro cycle synthesis. The next part of the thesis focuses on the cycloisomerization of diynes involving as the first step of the process the rearrangement of one alkyne partner into an allene thanks to a gold-catalyzed 1,3-shift of a propargylic ester. The thesis discloses a new cycloisomerization pattern featuring a 1,5-carbonyl transfer, giving rise to unprecedented cross-conjugated diketones. In the final part of the research, Simmoneau investigates the gold-catalyzed cycloisomerization mechanism of 1,6-enynes and questions the intermediacy of gold acetylides. By the means of NMR and mass spectrometry analysis, theoretical treatment and solution experiments, it was possible to rule out the involvement of these species in the catalytic cycle. This thesis has led to a number of publications in high-impact journals.