A photochemical deracemization of 5-substituted 3-phenylimidazolidine-2,4-diones (hydantoins) is reported (27 examples, 69%-quant., 80–99% ee). The reaction is catalyzed by a chiral diarylketone which displays a two-point hydrogen bonding site. Mechanistic evidence (DFT calculations, radical clock experiments, H/D labeling) suggests the reaction to occur by selective hydrogen atom transfer (HAT). Upon hydrogen binding, one substrate enantiomer displays the hydrogen atom at the stereogenic center to the photoexcited catalyst allowing for a HAT from the substrate and eventually for its conversion into the product enantiomer. The product enantiomer is not processed by the catalyst and is thus enriched in the photostationary state.

Upon irradiation in the presence of a chiral benzophenone catalyst (5 mol %), a racemic mixture of a given chiral imidazolidine-2,4-dione (hydantoin) can be converted almost quantitatively into the same compound with high enantiomeric excess (80−99% ee). The mechanism of this photochemical deracemization reaction was elucidated by a suite of mechanistic experiments. It was corroborated by nuclear magnetic resonance titration that the catalyst binds the two enantiomers by two-point hydrogen bonding. In one of the diastereomeric complexes, the hydrogen atom at the stereogenic carbon atom is ideally positioned for hydrogen atom transfer (HAT) to the photoexcited benzophenone. Detection of the protonated ketyl radical by transient absorption revealed hydrogen abstraction to occur from only one but not from the other hydantoin enantiomer. Quantum chemical calculations allowed us to visualize the HAT within this complex and, more importantly, showed that the back HAT does not occur to the carbon atom of the hydantoin radical but to its oxygen atom. The achiral enol formed in this process could be directly monitored by its characteristic transient absorption signal at λ ≅ 330 nm. Subsequent tautomerization leads to both hydantoin enantiomers, but only one of them returns to the catalytic cycle, thus leading to an enrichment of the other enantiomer. The data are fully consistent with deuterium labeling experiments and deliver a detailed picture of a synthetically useful photochemical deracemization reaction.

The Pd0/AuI-mediated coupling between a tungsten stannylcarbyne and a diverse range of aryl halides has allowed from one to four carbynes to be appended to, and bridged by, central aromatic ring systems including fused polycyclic examples.

Studies with chronic schizophrenia patients have demonstrated that patients fluctuate between rigid and unpredictable responses in decision-making situations, a phenomenon which has been called dysregulation. The aim of this study was to investigate whether schizophrenia patients already display dysregulated behavior at the beginning of their illness. Thirty-two first-episode schizophrenia or schizophreniform patients and 30 healthy controls performed the two-choice prediction task. The decision-making behavior of first-episode patients was shown to be characterized by a high degree of dysregulation accompanied by low metric entropy and a tendency towards increased mutual information. These results indicate that behavioral abnormalities during the two-choice prediction task are already present during the early stages of the illness.

A group of transition-metal catalyzed hydrogen moving reactions, encompassing hydrogen autotransfer (HAT; also called borrowing hydrogen, BH), dehydrogenative condensation (DHC) and alkene isomerization, displays high atom economy and relies on widely available starting materials. Such reactions have considerable potential for clean reaction design and application in sustainable synthesis. With the aim to develop and study synthetic applications of the title reactions, we have set up synthetic access routes to a toolbox of structurally varied ligands for and pincer complexes of some transition metals (cobalt, ruthenium, iridium) that are well established for the title reactions. Ligand target structures, for which often improved syntheses have been found, encompass 6,6'-dihydroxy-2,2'-bipyridine, 2(3-hydroxyphenyl)pyridines (as backbones for PCN pincers), 2(6-methylpyridine-2yl)pyridines (as backbones for PNN pincers) and 2(3-tolyl)pyridines (as backbones for PCN pincers). To support research towards asymmetric versions of the title reactions, we have prepared asymmetrically modified versions of well-established catalysts, including chiral, enantiopure versions of Milstein's PNN-ruthenium pincer, Kempe's triazinyl-diaminophosphanyl PNP-iridium-or -cobalt pincers, Huang's PCN-iridium pincers, and Grotjahn's alkene zipper complex. The strategy applied to 'chiral switching' relied on replacing symmetric dialkylphosphine donorgroups by dimenthylphosphine or aryl(menthyl)phosphine donor units. The resulting ligands or complexes have been structurally characterized, and the catalytic potential of the catalysts has been established in exploratory model reactions (transfer hydrogenation; diol to lactone dehydrogenative condensation; alkene isomerization). Several model reactions have been designed which will allow to study asymmetric catalytic hydrogen moving reactions.

Dual nucleophilic phosphine photoredox catalysis is yet to be developed due to facile oxidation of the phosphine organocatalyst to the phosphoranyl radical cation. Herein, we report a reaction design that avoids this event and exploits traditional nucleophilic phosphine organocatalysis with photoredox catalysis to allow the Giese coupling with ynoates. The approach has good generality, while its mechanism is supported by cyclic voltametric, Stern-Volmer quenching, and interception studies.

Dual nucleophilic phosphine photoredox catalysis is yet to be developed due to facile oxidation of the phosphine organocatalyst to the phosphoranyl radical cation. Herein, we report a reaction design that avoids this event and exploits traditional nucleophilic phosphine organocatalysis with photoredox catalysis to allow the Giese coupling with ynoates. The approach has good generality, while its mechanism is supported by cyclic voltametric, Stern-Volmer quenching, and interception studies.