Direct Cyclopropanation of α‐Cyano β‐Aryl Alkanes by Light Mediated Single Electron Transfer between Donor‐Acceptor Pairs

Cyclopropanes are traditionally prepared by the formal [2+1] addition of carbene or radical based C1 units to alkenes. In contrast, the one pot intermolecular cyclopropanation of alkanes by redox active C1 units has remained unrealised. Herein, we achieved this process simply by exposing β‐aryl propionitriles and C1 radical precursors ( N ‐oxy esters) to base and blue light. The overall process is redox‐neutral and a photocatalyst, whether metal‐ or organic‐based, is not required. Our findings support that single electron transfer (SET) from the α‐cyano carbanion of the propionitrile to the N ‐oxy ester is facilitated by blue‐light via their electron donor‐acceptor (EDA) complex. The α‐cyano carbon radical thus formed can then lose a β‐proton to form a π‐resonance stabilised radical anion that preferentially couples at the benzylic β‐position with a decarboxylated C1 radical unit. This new transition metal‐free chemistry tolerates both electron rich and electron deficient (hetero)aryl systems, even sulfide or alkene functionality, to afford a range of cis ‐aryl/cyano cyclopropanes bearing congested tetrasubsitituted quaternary carbons.