Excitation of organocatalytic intermediates and application in new radical processes

Identifier:  TDX:4205

Handle: https://hdl.handle.net/20.500.11797/TDX4205

Authors:  Balletti, Matteo

Abstract:
The work presented in this doctoral thesis highlights the use of excited-state organocatalytic intermediates as new radical-generating platform and the development of novel enantioselective radical transformations. It has been shown how, a new class of dithiocarbamate catalyst (DTC), can be exploited to activate acyl and carbamoyl chlorides through acyl nucleophilic substitution. Subsequent photolysis of the intermediate provided easy access to the corresponding C (sp2) radicals, which could be trapped by electron-poor olefins. Mechanistic studies, allowed us to elucidate the main steps and intermediates of the catalytic cycle. The DTC photochemical activation strategy was then coupled with asymmetric organocatalysis to develop the regio- and enantioselective remote functionalization of enals. Exploiting the action of a secondary amine catalyst, it was possible to elicit the in situ formation of chiral dienamines which intercepted the radicals, generated by the DTC platform, with high selectivity. Overall, the transformation provided a rare example of radical regio- and enantioselective -functionalization of branched enals. Finally, we leveraged on the previous knowledge acquired on vinylogous radical chemistry to use dienamines as donor partners for EDA complex formation with perfluoroalkyl iodides. Visible-light excitation of such complexes triggered the formation of perfluoroalkyl radicals, which could be intercepted by the chiral dienamines with high levels of regio- and enantio-selectivity to develop an enantioselective -perfluoroalkylation of enals.