Vitamin B12 and a metal-organic framework enable the photocatalytic generation of alkyl radicals.

A versatile Co-catalyst-vitamin B12 (cobalamin)-can be photochemically reduced to its catalytically active Co(I) form under visible light irradiation, in the presence of MIL-125-NH2(Ti) as a photocatalyst and utilized for the generation of alkyl radicals. The prior reduction of cobalamin to the Co(II) form is not required in this method.

Vinyl Azides as Radical Acceptors in the Vitamin B12-Catalyzed Synthesis of Unsymmetrical Ketones.

Vinyl azides are very reactive species and as such are useful building blocks, in particular, in the synthesis of N-heterocycles. They can also serve as precursors of ketones. These form in reactions of vinyl azides with nucleophiles or radicals. We have found, however, that under light irradiation vitamin B12 catalyzes the reaction of vinyl azides with electrophiles to afford unsymmetrical carbonyl compounds in decent yields. Mechanistic studies revealed that alkyl radicals are key intermediates in this transformation.