Regiodivergent α- and β-Functionalization of Saturated N-Heterocycles by Photocatalytic Oxidation

Synthetic methods that provide, via a central intermediate, access to two different types of products are highly valuable but difficult to establish. Here, we present a photocatalytic, regiodivergent method for the functionalization of saturated N-heterocycles at either the α- or the β-position. A t-butyl carbamate (Boc)-stabilized iminium ion serves as the key intermediate en route to either α-hydroxylation or β-elimination, depending on the choice of base. The operationally simple procedures use a readily available flavin-based catalyst and reagents, aqueous media, and do not require metals. Combined with facile downstream derivatization, the regiodivergent reaction gives rapid access to a large set of functionalized piperidines, molecules that are highly sought-after for the synthesis of pharmaceuticals and agrochemicals.