Transition metal promoted cycloadditions of strained three-membered carbocycles

Resumo

In this thesis transition metal promoted cycloadditions of trhee-strained carbocycles were carried out. On one hand, the chemistry of alkydlidenecyclopropenes (ACPs) was explored. Despite the abudant number of cycloadditions involving this systems, their enantioselective versions are scarce. In this context, using a low valent cobalt catalyst, a novel enantioselective intramolecular cycloaddition of ACPs and alkynes was succesfully developed. Moreover, mechanistic experiments and computational analysis of the reaction allowed us to stablish an unkonwk mechanism. In addition, the advantages of cobalt was applied in a intramolecular (3+2+2) cycloaddition of ACPs, alkynes and alkenes construction several polycarbocyclic scaffolds. Moreover, the intramolecular cycloaddition of ACPs with alkenes, allenes and dienes catalysed by cobalt was further analysed. The intermolecular cycloaddition of ACPs and trifluoromethyl ketones was also developed. By employing bulky biaryl phosphines as ligands several exo-methylene trifluoromethyl tetrahydrofurans could be synthetize in good yields albeit in low diastereomeric control. Finally, a novel (3+2) cycloaddition of cyclopropenes tethered to alkynes was accomplished. Employing a low valent cobalt catalyst several cyclopentadienes were synthetize with good efficinect. In addition, the syntehtic utility of this trasnformation was proved by the synthesis of several cyclopentadienyl rhodium complexes.