Dual-role of PtCl2 Catalysis in the Intramolecular Cyclization of (Hetero)Aryl-Allenes for the Facile Construction of Substituted 2,3-Dihydropyrroles and Polyheterocyclic Skeletons
A Pt(II)-catalyzed cyclization of (hetero)aryl-allenes has been developed, providing controllable synthesis of substituted 2,3-dihydropyrroles and polyheterocyclic skeletons. Temperature plays an important role to determine the product distribution: the reaction gives 2,3-dihydropyrroles when running at 70 oC, while further Friedel-Crafts type annulation takes place when the reaction temperature increased to 90 oC. Another notable feature of this method is the dual-role of Pt(II) catalyst, initiating the migration of (hetero)arylmethylene group and the subsequent Friedel-Crafts type annulation, respectively. The substrate scope is broad and a variety of functional groups are tolerated. Moreover, the synthetic utilization is further demonstrated by gram scale synthesis and simple transformation of the polyheterocyclic product into other drug-candidate molecules.