Stereoselective Radical Transformations by Co(II)-Based Metalloradical Catalysis
Chapter 1. Co(II)-Based Metalloradical Catalysis for Stereoselective Radical Cyclopropanation of Alkenes This Account summarizes our group’s recent efforts in developing metalloradical catalysis as a one-electron approach for catalytic radical cyclopropanation of alkenes with diazo compounds. Chapter 2. Asymmetric Radical Process for General Synthesis of Chiral Heteroaryl Cyclopropanes We have developed a Co(II)-based metalloradical system that is highly effective for asymmetric radical cyclopropanation of alkenes with in situ-generated heteroaryldiazomethanes. Through fine-tuning the cavity-like environments of newly developed D2-symmetric chiral amidoporphyrins as the supporting ligand, the optimized Co(II)-based metalloradical system is broadly applicable to pyridyl and other heteroaryldiazomethanes for asymmetric cyclopropanation of a wide range of alkenes, providing general access to valuable chiral heteroaryl cyclopropanes in high yields with excellent diastereoselectivities and enantioselectivities. Chapter 3. Enantioselective Metalloradical 1,6-C–H Alkylation of In Situ-Generated Alkyldiazomethanes for Synthesis of Chiral Piperidines We have disclosed an effective Co(II)-based metalloradical system as a fundamentally different approach to harness the potential of 1,6-HAA radical process, enabling asymmetric 1,6-C–H alkylation of in situ-generated alkyldiazomethanes to construct chiral piperidines. Supported by an optimal D2-symmetric chiral amidoporphyrin ligand, the Co(II)-catalyzed alkylation system is capable of activating a wide array of alkyldiazomethanes containing C(sp3)–H bonds with varied steric and electronic properties, providing access to chiral piperidines in good to high yields with high enantioselectivities from readily accessible 4-aminobutanal derivatives. In addition to practical attributes, such as operational simplicity and mild conditions, the metalloradical system is highlighted by its tolerance to different functional groups as well as compatibility with heteroaryl units. Chapter 4. Design and Synthesis of A Novel D2-Symmetric Chiral Porphyrin for Co(II)-Based Metalloradical Catalysis A novel D2-symmetric chiral amidoporphyrin derived from chiral cyclopropanecarboxamide containing diphenyl units has been effectively constructed based on Co(II)-catalyzed asymmetric cyclopropanation of alkenes.