C(sp3)-H methylation enabled by peroxide photosensitization and Ni-mediated radical coupling

The magic methyl effect describes the change in potency, selectivity, and/or metabolic stability of a drug candidate associated with addition of a single methyl group. We report a synthetic method that enables direct methylation of C(sp(3))-H bonds in diverse drug-like molecules and pharmaceutical building blocks. Visible light-initiated triplet energy transfer promotes homolysis of the O-O bond in di-tert-butyl or dicumyl peroxide under mild conditions. The resulting alkoxyl radicals undergo divergent reactivity, either hydrogen-atom transfer from a substrate C-H bond or generation of a methyl radical via beta-methyl scission. The relative rates of these steps may be tuned by varying the reaction conditions or peroxide substituents to optimize the yield of methylated product arising from nickel-mediated cross-coupling of substrate and methyl radicals.

Automated summary

The research presents a synthetic method that allows for direct methylation of C(sp(3))-H bonds in drug-like molecules and pharmaceutical building blocks, leading to changes in potency, selectivity, and metabolic stability.