Visible-Light-Initiated Manganese Catalysis for C-H Alkylation of Heteroarenes: Applications and Mechanistic Studies

A visible-light-driven Minisci protocol that employs an inexpensive earth-abundant metal catalyst, decacarbonyldimanganese Mn-2(CO)(10), to generate alkyl radicals from alkyl iodides has been developed. This Minisci protocol is compatible with a wide array of sensitive functional groups, including oxetanes, sugar moieties, azetidines, tert-butyl carbamates (Boc-group), cyclobutanes, and spirocycles. The robustness of this protocol is demonstrated on the late-stage functionalization of complex nitrogen-containing drugs. Photophysical and DFT studies indicate a light-initiated chain reaction mechanism propagated by Mn-.(CO)(5). The rate-limiting step is the iodine abstraction from an alkyl iodide by Mn-.(CO)(5).