Alkylation of in situ generated imines via photoactivation of strong aliphatic C-H bonds

Abstract

• A three-component photocatalytic process towards functionalized secondary alkyl amines. • Photoactivation of strong aliphatic C-H bonds via polyoxometalate tetrabutylammonium decatungstate (TBADT) catalyst. • An atom economic transformation via coupling of in situ generated imines and C-sp 3 centered radicals. The ubiquity of non-activated aliphatic C-H bonds has been the object of evergreen attention for the advantages that the direct functionalization of these strong C-H bonds hold. The development of photoredox catalysis has brought evident advancement in this field, providing a wide array of solutions to overcome the challenges related to the inertness of unactivated C-H bonds. In this regard, the use of polyoxometalate tetrabutylammonium decatungstate (TBADT) provides a straightforward solution for the generation of C-sp 3 centered radicals from aliphatic C-H bonds. Albeit the wide utilization of this photocatalyst, only a limited number of radical acceptors has been employed, and scarce reports on multicomponent reactions can be found, mainly due to chemoselectivity challenges and polarity match issues. Our study, therefore, focuses on the development of a broadly applicable strategy for the alkylation of in situ formed imines for the construction of functionalized secondary amines under mild reaction conditions. This atom economic transformation exploits the intrinsic electrophilicity of imines towards radical addition, and the fine-tuning of electronic properties of the starting materials allows the formation of a wide variety of products.