Deuterated Alkyl Sulfonium Salt Reagents; Importance of H/D Exchange Methods in Drug Discovery.

Deuterated drugs (heavy drugs) have recently been spotlighted as a new modality for small-molecule drugs because the pharmacokinetics of pharmaceutical drugs can be enhanced by replacing C-H bonds with more stable C-D bonds at metabolic positions. Therefore, deuteration methods for drug candidates are a hot topic in medicinal chemistry. Among them, the H/D exchange reaction (direct transformation of C-H bonds to C-D bonds) is a useful and straightforward method for creating novel deuterated target molecules, and over 20 reviews on the synthetic methods related to H/D exchange reactions have been published in recent years.

Furanyl bis(indolyl)methane as a palladium ion-selective chromogenic agent.

The colorless solution of furan-2-yl bis(indolyl)methane (BIM) is newly revealed to work as a palladium (Pd) ion-selective chromogenic agent by turning orange. 5-(-Methyl--phenyl-aminomethyl)-furan-2-yl BIM could be synthesized from 5-chloromethylfurfural as a biorenewable feedstock one-pot and double functionalization, and a mixture of its solution and Pd ions showed the highest absorbance at 465 nm in UV-Vis analysis. On the other hand, other metal ions (Cu, Cr, Cr, Fe, Fe, Ni, Zn, In, Pt, or Ce) exhibited no response.

Impact of multiple H/D replacements on the physicochemical properties of flurbiprofen.

Although deuterium incorporation into pharmaceutical drugs is an attractive way to expand drug modalities, their physicochemical properties have not been sufficiently examined. This study focuses on examining the changes in physicochemical properties between flurbiprofen (FP) and flurbiprofen- (FP-), which was successfully prepared by direct and multiple H/D exchange reactions at the eight aromatic C-H bonds of FP. Although the effect of deuterium incorporation was not observed between the crystal structures of FP and FP-, the melting point and heat of fusion of FP- were lower than those of FP.

Sulfonium Salt Reagents for the Introduction of Deuterated Alkyl Groups in Drug Discovery.

The pharmacokinetics of pharmaceutical drugs can be improved by replacing C-H bonds with the more stable C-D bonds at the α-position to heteroatoms, which is a typical metabolic site for cytochrome P450 enzymes. However, the application of deuterated synthons is limited. Herein, we established a novel concept for preparing deuterated reagents for the successful synthesis of complex drug skeletons with deuterium atoms at the α-position to heteroatoms.

Arylation of indoles using cyclohexanones dually-catalyzed by niobic acid and palladium-on-carbons.

3-Arylindoles were easily constructed from indoles and cyclohexanone derivatives using a combination of catalytic niobic acid-on-carbon (NbO/C) and palladium-on-carbon (Pd/C) under heating conditions without any oxidants. The Lewis acidic NbO/C promoted the nucleophilic addition of indoles to the cyclohexanones, and the subsequent dehydration and Pd/C-catalyzed dehydrogenation produced the 3-arylindoles. The additive 2,3-dimethyl-1,3-butadiene worked as a hydrogen acceptor to facilitate the dehydrogenation step.

Facile Hydrogenative Deprotection of -Benzyl Groups Using a Mixed Catalyst of Palladium and Niobic Acid-on-Carbon.

The palladium-on-carbon (Pd/C)-catalyzed hydrogenative deprotection of the -benzyl-protecting group was effectively facilitated by the combined use of niobic acid-on-carbon (NbO/C). NbO/C is an acidic heterogeneous catalyst prepared from NbCl and activated carbon. The catalysts were easily removed from the reaction mixture and reusable.

Birch-Type Reduction of Arenes in 2-Propanol Catalyzed by Zero-Valent Iron and Platinum on Carbon.

Catalytic arene reduction was effectively realized by heating in 2-propanol/water in the presence of Pt on carbon (Pt/C) and metallic Fe. 2-Propanol acted as a hydrogen source, obviating the need for flammable (and hence, dangerous and hard-to-handle) hydrogen gas, while metallic Fe acted as an essential co-catalyst to promote reduction. The chemical states of Pt and Fe in the reaction mixture were determined by X-ray absorption near-edge structure analysis, and the obtained results were used to suggest a plausible reaction mechanism, implying that catalytic reduction involved Pt- and Fe-mediated single-electron transfer and the dehydrogenation of 2-propanol.

Stainless Steel-Mediated Hydrogen Generation from Alkanes and Diethyl Ether and Its Application for Arene Reduction.

Hydrogen gas can be generated from simple alkanes (e.g., n-pentane, n-hexane, etc.