Radical Hydrocarboxylation of Unactivated Alkenes via Photocatalytic Formate Activation

Herein we disclose a strategy to promote the hydrocarboxylation of unactivated alkenes using photochemical activation of formate salts. We illustrate that an alternative initiation mechanism circumvents the limitations of prior approaches and enables hydrocarboxylation of this challenging substrate class. Specifically, we found that accessing the requisite thiyl radical initiator without an exogenous chromophore eliminates major byproducts that have plagued attempts to exploit similar reactivity for unactivated alkene substrates. This redox-neutral method is technically simple to execute and effective across a broad range of alkene substrates. Feedstock alkenes, such as ethylene, are hydrocarboxylated at ambient temperature and pressure. A series of radical cyclization experiments indicate how the reactivity described in this report can be diverted by more complex radical processes.