Access to high value sp 3 -rich frameworks using photocatalyzed [2 + 2]-cycloadditions of γ-alkylidene-γ-lactams.

By harnessing an energy transfer process, new photocatalyzed [2 + 2]-cycloadditions occurring between γ-alkylidene-γ-lactams and unsaturated substrates have been developed. The reaction mode is particularly powerful because it leads to the formation of different high value sp 3 -rich frameworks and further diversity can be introduced through cascade sequences wherein strain releasing opening of the cyclobutane intermediates gives access to complex polycyclic alkaloid frameworks.