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.

A new synthetic route to allylsilanes: the reaction of silyllithium reagents with aromatic carbonyl compounds and aluminium tris(2,6-diphenylphenoxide) (ATPH)

Boron and Silicon Lewis Acids for Mukaiyama Aldol Reactions

A tantalum-catalyzed solvent-free approach for the construction of amide bonds with 1-(trimethylsilyl)imidazole is developed, and the mild reaction conditions are applicable to a wide variety of electrophilic amino acid homologues. This approach delivers a new class of peptides in high yields without any epimerization.

Tantalum-Catalyzed Amidation of Amino Acid Homologues

Asymmetric Mannich-type reactions with a chiral acetate: effect of Lewis acid on activation of aldimine

Herein, we report a general and efficient method for direct N–O bond formation without undesirable C–N bond (amide) formation starting from commercially available amines and benzoyl peroxide. The oxidation of 1,2-diamines to furnish bis-(benzoyloxy)-1,2-diamines is reported for the first time. We found that a significant amount of water (BPO : water = 3 : 1) in combination with Cs2CO3 is necessary to achieve high selectivity and yield. The reaction conditions are applicable to a wide range of 1,2-diamine and 1,2-disubstituted-1,2-diamine substrates. Additionally this method is highly applicable to primary and secondary amines. Further, the present method can access chiral bis-hydroxamic acids and bis-hydroxyl amines in just two steps from 1,2-diamines. The reaction conditions are simple, mild and inert atmosphere free. The synthetic potential of this methodology is further demonstrated in the short synthesis of a chiral BHA ligand.

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Hisashi Yamamoto

Papers

A new synthetic route to allylsilanes: the reaction of silyllithium reagents with aromatic carbonyl compounds and aluminium tris(2,6-diphenylphenoxide) (ATPH)

Boron and Silicon Lewis Acids for Mukaiyama Aldol Reactions

Tantalum-Catalyzed Amidation of Amino Acid Homologues

Asymmetric Mannich-type reactions with a chiral acetate: effect of Lewis acid on activation of aldimine

Direct N–O bond formation via oxidation of amines with benzoyl peroxide