Synthesis of 6,12-Epiminodibenzo[b,f][1,5]diazocines via an Ytterbium Triflate-Catalyzed, AB2 Three-Component Reaction

An efficient and selective procedure for the synthesis of epiminodibenzo[b,f][1,5]diazocines involving a AB2 three-component reaction is developed. Two equivalents of suitably substituted 2-aminoarylaldehydes reacted with arylamines in the presence of Yb(OTf)3 to afford the desired products in high yields. The reaction is highly atom-economic and waste-free, in addition to allowing the generation of two heterocyclic rings and four C–N bonds in a single operation. Significantly, this approach is complementary to the existing literature procedures, affording arylamine-derived products that could not be accessed previously. A plausible mechanism is proposed involving an imine formation-intermolecular annulation-intramolecular iminium ion cyclization sequence.