Cobalt phthalocyanine (Co(Pc)) is a new co-catalyst for radical generation that is compatible with nickel catalysis. To demonstrate the potential of Co(Pc), we applied this co-catalyst to the synthesis of diarylmethanes, a valuable class of molecules in medicinal chemistry. Mechanistic studies demonstrate that nickel is slow to react with benzylic mesylates (BnOMs), avoiding bibenzyl formation, while Co(Pc) reacts selectively with BnOMs to form benzyl radicals, leading to selective cross-product formation. In our new approach, BnOMs can be conveniently generated <i>in situ</i> from abundant benzyl alcohols and no pre-formed nucleophiles are needed. The nickel and cobalt co-catalytic strategy of synthesizing diarylmethanes shows good functional group tolerance and can be applied to the synthesis of beclobrate, an antilipidemic drug. The adaptation of these conditions to a less reactive electrophile (phosphate ester), and an enantioconvergent reaction will also be discussed.

New co-catalyst strategy: Cobalt and nickel-catalyzed cross-electrophile coupling of benzyl mesylates and aryl halides

249th National Meeting (2015)

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