In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

Organic Photoredox Catalysis

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

Asymmetric enamine catalysis.

Reactions that convert carbon–hydrogen (C–H) bonds into carbon–carbon (C–C) or carbon–heteroatom (C–Y) bonds are attractive tools for organic chemists, potentially expediting the synthesis of target molecules through new disconnections in retrosynthetic analysis. Despite extensive inorganic and organometallic study of the insertion of homogeneous metal species into unactivated C–H bonds, practical applications of this technology in organic chemistry are still rare. Only in the past decade have metal-catalyzed C–H functionalization reactions become more widely utilized in organic synthesis.Research in the area of homogeneous transition metal–catalyzed C–H functionalization can be broadly grouped into two subfields. They reflect different approaches and goals and thus have different challenges and opportunities. One approach involves reactions of completely unfunctionalized aromatic and aliphatic hydrocarbons, which we refer to as “first functionalization”. Here the substrates are nonpolar and hydrophobic a...

Weak coordination as a powerful means for developing broadly useful C-H functionalization reactions.

Small-molecule H-bond donors in asymmetric catalysis.

Molecular Recognition of Carbonyl Compounds Using Aluminum Tris(2,6-diphenylphenoxide) (ATPH): New Regio- and Stereoselective Alkylation of α,β-Unsaturated Carbonyl Compounds.

Significance: Chiral pyridone backbones can be found in many bioactive compounds. The authors have developed a nickel-catalyzed enantioselective C–H functionalization of 2and 4-pyridones by using a bulky N-heterocyclic ligand. Comment: This nickel-catalyzed reaction permits the enantioselective intramolecular C–H functionalization of 2and 4-pyridones. The nickel complex, based on a chiral bulky N-heterocyclic ligand, is effective in terms of selectivity, giving chiral 2and 4-pyridones in good yields and with high enantioselectivities. Selected examples: X N O R1 R2 Ni(cod)2 (10 mol%) ligand (11 mol%) MAD (40 mol%)

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Nickel-Catalyzed Asymmetric C–H Functionalization of Pyridones

455 Y . S H I N , K . A . W I N A N S , B . J . B A C K E S , S . B . H . K E N T , J . A . E L L M A N , C . R . B E R T O Z Z I * ( U N I V E R S I T Y O F C A L I F O R N I A , B E R K E L E Y A N D G R Y P H O N S C I E N C E S , S O U T H S A N F R A N C I S C O , U S A ) Fmoc-Based Synthesis of Peptide-Thioesters: Application to the Total Chemical Synthesis of a Glycoprotein by Native Chemical Ligation J. Am. Chem. Soc. 1999, 121, 11684–11689.

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Total Chemical Synthesis of a Glycoprotein by Native Chemical Ligation

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Sulfide-Mediated Peptide Ligation in Water

The asymmetric hydroxyamination of β-ketoesters with nitrosocarbonyl compounds generated in situ is described.

Asymmetric Construction of Quaternary Stereocenters by Magnesium Catalyzed Direct Amination of β‐Ketoesters Using in situ Generated Nitrosocarbonyl Compounds as Nitrogen Sources.

Hisashi Yamamoto

Papers

Molecular Recognition of Carbonyl Compounds Using Aluminum Tris(2,6-diphenylphenoxide) (ATPH): New Regio- and Stereoselective Alkylation of α,β-Unsaturated Carbonyl Compounds.

Nickel-Catalyzed Asymmetric C–H Functionalization of Pyridones

Total Chemical Synthesis of a Glycoprotein by Native Chemical Ligation

Sulfide-Mediated Peptide Ligation in Water

Asymmetric Construction of Quaternary Stereocenters by Magnesium Catalyzed Direct Amination of β‐Ketoesters Using in situ Generated Nitrosocarbonyl Compounds as Nitrogen Sources.