Organocatalytic Synthesis of Tetrahydroquinolines from a,p-Unsaturated Ketones via 1,5-Hydride Transfer/Cyclization

摘要

The development for direct functionalization of sp3 C-H bonds has become an area of intense interest in synthetic organic chemistry. Because such reactions offer practical methods for the construction of structurally complex and biologically active organic molecules with atom- and step economy.1 The 1,5-hydride transfer and subsequent cycli-zation process is a well-known sp3 C-H bond functionalization strategy and has attracted considerable interest for its application in the synthesis of heterocyclic compounds. Sames group successfully applied the intramolecular 1,5-hydride transfer/cyclization strategy to the functionalization of ether, carbamate, and benzylic C-H bonds bearing unsaturated moieties. This protocol includes the initial cleavage of a C-H bond in the context of a hydride transfer to give a zwitterionic intermediate, followed by ring closure to give the cyclic products. The tert-amino effect and related 1,5-hydride transfer/subsequent cyclization has attracted much attention due to its unique features to afford tetrahydroquinolines.3'4 Tetrahydroquinoline derivatives have attracted considerable attention in organic synthesis and medicinal chemistry due to their importance as building blocks and diverse array of biological activities.