Yuta Fujiwara

Mild and Efficient H/D Exchange of Alkanes Based on CH Activation Catalyzed by Rhodium on Charcoal

The C H bond activation of organic compounds is one of the most useful synthetic methods for the fuctionalization of simple molecules. The activation of unsaturated compounds can be achieved using transition-metal catalysts, and the coordination of a metal center to the p bond plays an important role in the reaction process. On the other hand, alkanes (saturated organic compounds) are known to be much less reactive towards C H bond activation than unsaturated compounds because alkanes possess no coordination sites for metals. Therefore only a few processes, such as oxidation, H/D exchange, dehydrogenation, and radical reactions, have been reported as being C H activationinduced, even though extensive efforts to activate alkanes have been made. The H/D exchange reaction is a basic transformation of alkanes. Deuterated products have received attention not only as useful tools for the investigation of human metabolism or reaction mechanisms, but also as functional materials like deuterated polymers as components of optical fibers for high-speed telecommunications systems. Deuterated pesticides and pharmaceuticals are also effective for quantitative analyses and bioanalytical investigations as internal standards, while deuterated alkanes are expected to be applied as marker molecules to prevent the distribution of illegally mixed light diesel oil. Owing to this increasing interest, it is important to develop an efficient and facile H/D exchange method for alkanes. Since the first H/D exchange of alkanes was reported by Shilov and co-workers, other H/D exchange reactions of alkanes have been developed. Recently, Bergman and co-workers reported an efficient H/D exchange method for various substrates, including alkanes, by using a homogeneous cationic Ir hydride complex under mild conditions. The H/D exchange reaction with deuterium oxide catalyzed by Pd/C under hydrothermal conditions has also been reported. We have recently established a method for deuterium incorporation into organic molecules by using a combination of Pd/C (or Pt/C) in D2O under H2, which has led to efficient H/D exchange for a variety of organic molecules such as aromatic compounds, ketones, and alcohols (Scheme 1). As part of an ongoing program for the development of H/D exchange reactions induced by heterogeneous catalysts, we have discovered a unique protocol for the C H

Method for regio-, chemo- and stereoselective deuterium labeling of sugars based on ruthenium-catalyzed C-H bond activation.

An efficient and facile deuterium labeling of sugars has been achieved in a completely regio-, chemo- and stereoselective manner using the Ru/C-H(2)-D(2)O combination via C-H bond activation assisted by the coordination of Ru to the oxygen atom of the sugar-hydroxyl groups.

Stereo- and regioselective direct multi-deuterium-labeling methods for sugars.

Deuterium-labeled sugars can be utilized as powerful tools for the architectural analyses of high-sugar-containing molecules represented by the nucleic acids and glycoproteins, and chiral building blocks for the syntheses of new drug candidates (heavy drugs) due to their potential characteristics, such as simplifying the (1)H NMR spectra and the stability of C-D bonds compared with C-H bonds. We have established a direct and efficient synthetic method of deuterated sugars from non-labeled sugars by using the heterogeneous Ru/C-catalyzed H-D exchange reaction in D(2)O under a hydrogen atmosphere with perfect chemo- and stereoselectivities. The direct H-D exchange reaction can selectively proceed on carbons adjacent to the free hydroxyl groups, and the deuterium labeling of various pyranosides (such as glucose and disaccharides), as well as furanosides, represented by ribose and deoxyribose was realized. Furthermore, the desired number of deuterium atoms can be freely incorporated into selected positions by the site-selective protection of the hydroxyl groups using acetal-type protective groups because the deuterium exchange reaction never proceeds on positions adjacent to the protected hydroxyl groups.

Effect of sodium acetate in atom transfer radical addition of polyhaloalkanes to olefins

The atom transfer radical addition of polyhaloalkanes, such as bromotrichloromethane and polyfluoroalkyl iodine, to olefins smoothly proceeds in the presence of sodium acetate as an efficient auxiliary agent in dimethoxyethane. The present transition metal- and peroxide-free methodology is applicable to a broad scope of substrates.

Facile Hydrogenation of Ketones Catalyzed by Platinum on Carbon under Ordinary Pressures and Temperatures

An efficient and practical procedure for the hydrogenation of aliphatic and aromatic ketones under mild reaction conditions is established. The method is highly effective even for the hydrogenation of sterically hindered ketones. Furthermore, the selective hydrogenation of the carbonyl group of aromatic ketones was achieved with the aromatic nuclei and the resulting secondary benzyl alcohol moiety still intact on addition of catalytic amount of pyridine.