Divergent and Synergistic Photocatalysis: Hydro- and Oxoalkylation of Vinyl Arenes for the Stereoselective Synthesis of Cyclopentanols via a Formal [4+1]-Annulation of 1,3-Dicarbonyls

The controllable
divergent reactivity of 1,3-dicarbonyls is described,
which enables the efficient hydro- and oxoalkylation of vinyl arenes.
Both reaction pathways are initiated through the formation of polarity-reversed C-centered-radical intermediates at the active methylene
center of 1,3-dicarbonyls via direct photocatalytic C–H bond
transformations. The oxoalkylation of alkenes is achieved under aerobic
conditions via a Cu­(II)-photomediated rebound mechanism, while
the corresponding hydroalkylation becomes possible under a nitrogen
atmosphere by the combination of 4CzIPN and a Brønsted base.
The breadth of these divergent protocols is demonstrated in the late-stage
modification of drugs and natural products and by the transformation
of the products to a variety of heterocycles such as pyridines, pyrroles,
or furans. Moreover, the two catalytic modes can be combined synergistically
for the stereoselective construction of cyclopentanol derivatives
in a formal [4+1]-annulation process.