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During the recent development of machine-learning (ML) methods for organic synthesis, the value of "failed experiments" has increasingly been acknowledged. Accordingly, we have developed an exhaustive database comprising 300 entries of experimental data obtained by performing ruthenium-catalyzed hydrogenation reactions using 10 ketones as substrates and 30 phosphine ligands. After evaluating the predictive performance of ML models using the constructed database, we conducted a virtual screening of commercially available phosphine ligands. For the virtual screening, we utilized several models, such as histogram-based gradient boosting and Ridge regression, combined with the Mordred descriptors and MACCSKeys, respectively. The disclosed approach resulted in the identification of high-performance phosphine ligands, and the rationale behind the predictions in the virtual screening was analyzed using SHAP.

Catalytic systems using a small amount of organic photosensitizer for the activation of an inorganic (on-demand ligand-free) nickel(II) salt represent a cost-effective method for cross-coupling reactions, while C(sp 2 )-O bond formation remains less developed. Herein, we report a strategy for the synthesis of phenols with a nickel(II) salt and an organic photosensitizer, which was identified via an investigation into the catalytic activity of 60 organic photosensitizers consisting of various electron donor and acceptor moieties. To examine the effect of multiple intractable parameters on the catalytic activity of photosensitizers, machine-learning (ML) models were developed, wherein we embedded descriptors representing their physical and structural properties, which were obtained from DFT calculations and RDKit, respectively. The study clarified that integrating both DFT- and RDKit-derived descriptors in ML models balances higher "precision" and "recall" across a wide range of search space relative to using only one of the two descriptor sets., (© 2023 Wiley-VCH GmbH.)

A metal-free and operationally simple strategy for the generation of various α-monofluoroalkyl radicals has been developed. A combination of 1,4-bis(diarylamino)naphthalene photocatalyst and sulfoximine-based fluoroalkylating reagents is the key to success. The protocol can be applied to modular synthesis of β-monofluoroketones through radical monofluoroalkylation of alkenyl acetates.

Organic photoredox catalysis has become a useful tool for the development of metal-free radical reactions. Recently, we have reported that 1,4-bis(diphenylamino)naphthalene N serves as an efficient photoredox catalyst for radical monofluoromethylation with N -tosyl- S -monofluoromethyl- S -phenylsulfoximine 2 . In this paper, we report the preparation and photo- and electrochemical properties of (diarylamino)naphthalene derivatives, 1,4-bis(di( p - tert -butylphenyl)amino)naphthalene 1a , 1,5-bis(di( p - tert -butylphenyl)amino)naphthalene 1b , and 1-(di( p - tert -butylphenyl)amino)naphthalene) 1c , as supported by density functional theory (DFT) and time-dependent-DFT calculations. In addition, their performance of photocatalysis has been evaluated by means of methoxy-monofluoromethylation of aromatic alkenes. Laser flash photolysis shows that the fluorescence of 1a in the excited state is efficiently quenched by 2 (quenching rate constant k q = ca. 2 × 10 9 M -1 s -1 ). Transient absorption spectroscopic analyses reveal that the excited species of 1a in the presence of 2 starts decreasing in ca. 100 ps, suggesting the occurrence of fast electron-transfer processes. These results lead to the unconventional concept for the catalyst design, that is, long lifetime of the excited state is not always a requisite for efficient photoredox catalysts.

Regioselective amino-difluoromethylation of aromatic alkenes via C(sp 3 )-CF 2 H and C(sp 3 )-N bond formation with the C[double bond, length as m-dash]C moiety has been achieved in a single operation by visible-light photoredox catalysis. The combination of a shelf-stable and easy-to-handle sulfonium salt, S -difluoromethyl- S -di( p -xylyl)sulfonium tetrafluoroborate, and perylene catalysis is the key to the successful transformation. Furthermore, this noble metal-free protocol allows for the photocatalytic trifluoromethylation of alkenes., (This journal is © The Royal Society of Chemistry 2017.)

Simple synthesis of CF3- and CF2H-spiroethers from aryl-fused cycloalkenylalkanols by photoredox catalysis has been developed. Modification of the fluoromethylating reagents and the photoredox catalysts leads to both CF3- and CF2H-spiroetherification. The present photocatalytic system allows us to access a variety of new anti-fluoromethylated spiroethers in a highly selective manner.

A novel synthesis of CF3-containing spirooxazolines and spirooxazines has been developed. Regiospecific trifluoromethylative spirocyclization (CF3-spirocyclization) of cyclic alkenes bearing an amide pendant mediated by photoredox catalysis is a useful strategy for construction of a C(sp(3))-CF3 bond and an spirooxazoline or spirooxazine ring onto C═C bonds via a single step. The key intermediate is α-CF3-substituted carbocationic species smoothly generated from single-electron-transfer (SET) photoredox processes, which results in diastereoselective spirocyclization. This is the first example of synthesis of CF3-containing spirooxazolines and spirooxazines in anti-fashion with respect to the CF3 group and the oxygen atom of the spirocycles.