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Bioinspired Vitamin B12 Catalysis

Sunday, 28 May 2017: 15:00
Grand Salon C - Section 16 (Hilton New Orleans Riverside)
D. Gryko (Institute of Organic Chemistry Polish Academy of Sciences)
Vitamin B12 catalysis is inspired by the ultimate chemist Nature, as methylcobalamin and adenosylcobalamin are involved in numerous biocatalytic reactions including isomerization, methylation and dehalogenation.[1,2] This type of catalysis has been successfully translated into the laboratory and used in a small collection of reactions.[2, 3] The advantage of using vitamin B12 as a catalyst lays in the complete stability of the central cobalt ion, whereas most catalytic reactions require the addition of toxic metals plus complex ligands into a cocktail of reagents, vitamin B12in itself is a package deal. It has also been well documented that the reaction mechanism usually follows a radical pathway, bringing a new dimension to this already interesting field.

Along this line, we have proposed vitamin B12 photochemical activation in bond forming and cleavage reactions.[4] Our results show that TiO2 can be utilized in a catalytic system with vitamin B12, allowing for the efficient photocatalytic reduction of Co(III) to Co(I). Under light irradiation vitamin B12 derivative unusually catalyzes a new olefinic sp2 C-H alkylation reaction, with diazo reagents as a carbene source, instead of the expected cyclopropanation. Furthermore, we also use challenging acyl radicals in C-C bond forming reactions. Light-induced vitamin B12-catalyzed methods are also suitable for C-O bond cleavage. Our studies showed that reduced cyanocobalamin catalyzes C-O bond cleavage in allyloxyarenes.

These key findings emphasize the unique feature of vitamin B12as a catalyst to achieve something unachievable with other methodologies or to find a greener approach.

1. Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999
2. K. ó Proinsias, M. Giedyk, D. Gryko, Chem. Soc. Rev. 2013, 42, 6605-6619.
3. Giedyk, M.; Fedosov, S.; Gryko, D. Chem. Commun. 2014, 50, 4674-4676.
4. a) Shimakoshi, H.; Nishi, M.; Tanaka, A.; Chikama, K.; Hiseada, Y. Chem. Commun. 2011, 47, 6548-6550. b) K. Tahara, Y. Hisaeda, Green Chem. 2011, 13, 558-561. H. Shimakoshi, L. Li, M. Nishi, Y. Hisaeda, Chem. Commun. 2011, 47, 10921-10923.