Asymmetric catalysis is seen as one of the most economical strategies to satisfy the growing demand for enantiomerically pure small molecules in the fine chemical and pharmaceutical industries. And visible light has been recognized as an environmentally friendly and sustainable form of energy for triggering chemical transformations and catalytic chemical processes. For these reasons, visible-light-driven catalytic asymmetric chemistry is a subject of enormous current interest. Photoredox catalysis provides the opportunity to generate highly reactive radical ion intermediates with often unusual or unconventional reactivities under surprisingly mild reaction conditions. In such systems, photoactivated sensitizers initiate a single electron transfer from (or to) a closed-shell organic molecule to produce radical cations or radical anions whose reactivities are then exploited for interesting or unusual chemical transformations. However, the high reactivity of photoexcited substrates, intermediate radical ions or radicals, and the low activation barriers for follow-up reactions provide significant hurdles for the development of efficient catalytic photochemical processes that work under stereochemical control and provide chiral molecules in an asymmetric fashion. Here we report a highly efficient asymmetric catalyst that uses visible light for the necessary molecular activation, thereby combining asymmetric catalysis and photocatalysis. We show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide very effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre simultaneously serves as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the 'green' synthesis of non-racemic chiral molecules.

A chiral-at-metal octahedral rhodium(iii) complex serves as an effective asymmetric catalyst for Michael additions (electrophile activation) and α-aminations (nucleophile activation).

An efficient enantioselective addition of alkyl radicals, oxidatively generated from organotrifluoroborates, to acceptor-substituted alkenes is catalyzed by a bis-cyclometalated rhodium catalyst (4 mol %) under photoredox conditions. The practical method provides yields up to 97% with excellent enantioselectivities up to 99% ee and can be classified as a redox neutral, electron-transfer-catalyzed reaction.

A metal-coordination-based high performance asymmetric catalyst utilizing metal centrochirality as the sole element of chirality is reported. The introduced substitutionally labile chiral-at-metal octahedral iridium(III) complex exclusively bears achiral ligands and effectively catalyzes the enantioselective Friedel-Crafts addition of indoles to α,β-unsaturated 2-acyl imidazoles (19 examples) with high yields (75%-99%) and high enantioselectivities (90-98% ee) at low catalyst loadings (0.25-2 mol %). Counterintuitively, despite its substitutional lability, which is mechanistically required for coordination to the 2-acyl imidazole substrate, the metal-centered chirality is maintained throughout the catalysis. This novel class of reactive chiral-at-metal complexes will likely be of high value for a large variety of asymmetric transformations.

An enantioselective, catalytic trichloromethylation of 2-acyl imidazoles and 2-acylpyridines is reported. Several products are formed with enantiomeric excess of ≥99%. In this system, a chiral iridium complex serves a dual function, as a catalytically active chiral Lewis acid and simultaneously as a precursor for an in situ assembled visible-light-triggered photoredox catalyst.

Stereochemical control in the construction of carbon-carbon bonds between an alkyl electrophile and an alkyl nucleophile is a persistent challenge in organic synthesis. Classical substitution reactions via SN1 and SN2 pathways are limited in their ability to generate carbon-carbon bonds (inadequate scope, due to side reactions such as rearrangements and eliminations) and to control stereochemistry when beginning with readily available racemic starting materials (racemic products). Here, we report a chiral nickel catalyst that couples racemic electrophiles (propargylic halides) with racemic nucleophiles (β-zincated amides) to form carbon-carbon bonds in doubly stereoconvergent processes, affording a single stereoisomer of the product from two stereochemical mixtures of reactants.

A direct enantioselective acylation of α-amino C(sp 3 )−H bonds with carboxylic acids has been achieved via the merger of transition metal and photoredox catalysis. This straightforward protocol enables cross-coupling of a wide range of carboxylic acids, one class of feedstock chemicals, with readily available N-alkyl benzamides to produce highly valuable α-amino ketones in high enantioselectivities under mild conditions. The synthetic utility of this method is further demonstrated by gram scale synthesis and application to late-stage functionalization. This method provides an unprecedented solution to address the challenging stereocontrol in metallaphotoredox catalysis and C(sp 3 )−H functionalization. Mechanistic studies suggest the α-C(sp 3 )−H bond of the benzamide coupling partner is cleavage by photocatalytically generated bromine radicals to form α-amino alkyl radicals, which subsequently engages in nickel-catalyzed asymmetric acylation.

Octahedral iridium(III) complexes containing two bidentate cyclometalating 5-tert-butyl-2-phenylbenzoxazole (IrO) or 5-tert-butyl-2-phenylbenzothiazole (IrS) ligands in addition to two labile acetonitrile ligands are demonstrated to constitute a highly versatile class of asymmetric Lewis acid catalysts. These complexes feature the metal center as the exclusive source of chirality and serve as effective asymmetric catalysts (0.5-5.0 mol % catalyst loading) for a variety of reactions with α,β-unsaturated carbonyl compounds, namely Friedel-Crafts alkylations (94-99% ee), Michael additions with CH-acidic compounds (81-97% ee), and a variety of cycloadditions (92-99% ee with high d.r.). Mechanistic investigations and crystal structures of an iridium-coordinated substrates and iridium-coordinated products are consistent with a mechanistic picture in which the α,β-unsaturated carbonyl compounds are activated by two-point binding (bidentate coordination) to the chiral Lewis acid.