Highly Efficient and Enantioselective α-Arylation of Cycloalkanones by Scandium-Catalyzed Diazoalkane-Carbonyl Homologation

Abstract

Functionalized α-tertiary and -quaternary 2-arylcycloalkanones are rapidly accessed by scandium(III) triflate-catalyzed diazo­alkane-carbonyl homologations. Recent developments have allowed for carbon insertion reactions to be performed with catalyst loadings as low as 0.5 mol% on scales up to 5 mmol. Pairing readily available bis- and tris(oxazoline) based ligands with scandium triflate allows access to arylated medium ring carbocycles with enantioselectivities up to 98:2 er and >98% yield. The formal C-C insertion of aryldiazo­methanes into unsubstituted cycloalkanones provides a single-step solution to the ongoing challenge of α-arylation.

Key words

diazo compounds - scandium - asymmetric catalysis - ring expansion - arylation

References

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9

Rendina V. L.; Kingsbury, J. S. Submitted to J. Org. Chem. for publication.

10

Though not studied in the context of cycloalkanone ring expansions, heteroaromatic substrates are well tolerated in the Sc-catalyzed homologation of aldehydes. See reference 6b.