Photoinduced Cobalt-Catalyzed Enantioselective Decarboxylative Cross-Sulfonylimine Coupling

The direct conversion of readily available and stable
carboxylic
acids into enantiomerically enriched chiral molecules has long been
a valuable target for chemists. The high oxidation potential of carboxylic
acids and the highly reactive radical intermediates generated in situ
render enantioselective control particularly challenging. This report
describes a photoinduced cobalt-catalyzed enantioselective decarboxylative
cross-sulfonylimine coupling reaction that offers a promising approach
to achieving this difficult reactivity. A charge-transfer complex
derived from arylacetic carboxylate and sulfonylimine induced radical
decarboxylation and subsequent enantioselective radical coupling under
visible light and in the presence of a cobalt catalyst, thereby constructing
tetrasubstituted chiral carbon centers with high enantioselectivity
(up to 96% ee). Mechanistic investigations indicate that the cobalt
salt serves as both the catalyst precursor and catalytic base, which
is crucial for activating carboxylic acids. Notably, an exogenous
photoredox catalyst is not needed in the developed protocol.