Bioorganometallic structure found in coenzyme B12 is a key component in B12-dependent enzymatic reactions in natural enzymes. Cleavage of a cobalt-carbon bond in organometallic B12 compound provide reactive intermediate for molecular transformations. Application of the bioorganometallic B12 in organic synthesis have been developed using natural vitamin B12 as well as synthetic vitamin B12 derivatives as a bioinspired catalyst in organic solvent. Vitamin B12 derivatives composed of corrinoid structure should form stable organometallic compound having a cobalt-carbon bond. Using the unique property of the organometallic vitamin B12 derivatives, various catalytic reactions have been developed in synthetic organic chemistry. The dual catalytic system of vitamin B12 derivatives and photocatalyst, such as Ru(II) polypyridyl complex or titanium oxide, could construct light-driven molecular transformations. The B12-dependent enzymes mimic reactions, such as the dechlorination of organic halides and the radical mediated isomerization reactions, catalytically proceed in the dual catalyst system. Electroorganic syntheses mediated by the vitamin B12 derivatives have been developed as green molecular transformations. The redox active vitamin B12 derivatives shows a unique catalysis in the electroorganic synthesis, such as alkene and alkyne reductions.