An unprecedented, chemo- and regioselective, organo-photoredox catalyzed hydroformylation reaction of aryl olefins with diethoxyacetic acid as the formylation reagent is described. In contrast to traditional transition metal promoted ionic hydroformylation… Click to show full abstract
An unprecedented, chemo- and regioselective, organo-photoredox catalyzed hydroformylation reaction of aryl olefins with diethoxyacetic acid as the formylation reagent is described. In contrast to traditional transition metal promoted ionic hydroformylation reactions, the new process follows a unique photoredox promoted, free radical pathway. In this process, a formyl radical equivalent, produced from diethoxacetic acid through a dye (4CzIPN) photocatalyzed, sequential oxidation-decarboxylation route, regio- and chemoselectively adds to a styrene substrate. Importantly, under the optimized reaction conditions the benzylic radical formed in this manner is reduced by SET from the anion radical of 4CzIPN to generate a benzylic anion. Finally, protonation produces the hydroformylation product. By using the new protocol, aldehydes can be generated regioselectively in up to 90% yield. A broad array of functional groups is tolerated in the process, which takes place under mild, metal-free conditions.
               
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