Regiocontrolled synthesis of (hetero)aryl and alkenyl dehydropyrrolidines, dehydropiperidines and azepenes by Ru-catalyzed, heteroatom-directed α-C–H activation/cross-coupling of cyclic enamides with boronic acids†
The synthesis of α-aryl and alkenyl pyrrolidine-, piperidine-, and azepane derivatives, through the intermediacy of cyclic enamides is described. The desired outcome is achieved through ruthenium-catalyzed, site-selective sp2 C–H activation/cross-coupling with aryl and alkenyl boronic acids. The regioselectivity (α-sp2vs. α-sp3vs. β-sp2 C–H functionalization) is governed by the rate differences between sp2 and sp3 C–H activation and the necessity for chelation between the ruthenium metal and the carbonyl directing group.