Terumasa Kato

The first tail-to-tail dimerization of methacrylonitrile (MAN) has been realized by the cooperative use of N-heterocyclic carbene (NHC) and Brønsted acid catalysts, producing 2,5-dimethylhex-2-enedinitrile with the E/Z ratio of 24:76. Although the NHC alone was not effective for the catalysis, the addition of alcohols resulted in the significant increase of the dimer yield up to 82% in the presence of 5 mol % NHC. Detailed experimental studies including the ESI-MS analysis of the intermediates,

We and others have previously reported the intermolecular umpolung reactions of Michael acceptors catalyzed by an N-heterocyclic carbene (NHC). The representative tail-to-tail dimerization of methyl methacrylate (MMA) has now been intensively investigated, leading to the following conclusions: (1) The catalysis involves the deoxy-Breslow intermediate, which is quite stable and remains active after the catalysis. (2) Addition of the intermediate to MMA and the final catalyst elimination are the r

ESR spectra of γ-irradiated TGS were observed in both ferroelectric and paraelectric phases. The hyperfine splitting tensors of the rotating β-protons and the α-proton in the radical NH 3 \(\dot{\text{C}}\)HCOO - , were determined. The hfs tensor of the β-protons was varied when the crystal passed through the Curie point. From the temperature dependence of the spectrum, the frequency factor, f 0 and the activation energy E of the rotating β protons were determined to be 5×10 11 sec -1 and 0.17 e

N-Heterocyclic carbenes (NHCs) promote the transfer hydrogenation of various activated C=C, C=N, and N=N bonds with water as the proton source. The NHCs act as reducing reagents to be converted into their oxides. A detailed reaction mechanism is proposed on the basis of deuterium-labeling experiments.

Three species of radicals were observed. One of these was already identified as HN 3 \(\dot{\text{C}}\)HCOO - by Ovenall et al. and by Blinc et al. . One of the other species, which appears as a triplet with an intensity ratio of 1:2:1, is identified as \(\dot{\text{C}}\)H 2 COO - . The principal values of A - and g -tensor of the radical are determined to be 25.1, 19.6 and 16.7 gauss and 1.9994, 1.9999 and 2.0009, respectively. From the temperature dependence of the spectra, it is concluded tha

A series of new bowl-shaped N-hydroxyimide derivatives has been designed and used as selective organoradical catalysts. A number of these bowl-shaped N-hydroxyimide derivatives exhibit excellent site-selectivity in the amination of benzylic C(sp³ )-H bonds in aromatic hydrocarbon substrates.

The ESR spectra of Cu 2+ doped in TGS were analyzed without any assumption in the symmetry of the crystal field. At room temperature, the directions of the maximum principal values of the A - and g -tensors agreed within 4° with the normal to the plane containing the two glycines, glycine 2 and glycine 3. the directions of g x and g y were nearly parallel to the bisector lines between N-N and O-O. At 77 K, two kinds of the absorption lines, the spectrum I and spectrum II, were observed. The form

The copper-catalyzed selective cleavage of alkylsilyl peroxides and the subsequent formation of carbon-carbon or carbon-nitrogen bonds with organosilicon compounds are described. The reaction proceeds under mild conditions and exhibits a broad substrate scope with respect to both cyclic and acyclic alkylsilyl peroxides in combination with carbon and nitrogen sources. In particular, this approach enables the facile radical perfluoroalkylation using commercially available perfluoroalkyltrimethylsi

The directions of the CH bonds of \(\dot{\text{C}}\)H 2 COO - radical in TGS at liquid nitrogen temperature were determined. The activation energy for the exchange of two hydrogens in the radical was also determined to be 0.16±0.03 eV, from the temperature dependence of ESR spectrum. A motional narrowing of proton resonance line in NMR will be expected at about 110°K, if the two hydrogens in glycine (I) would exchange their positions to each other in the unirradiated TGS crystal.

N-Heterocyclic carbenes (NHCs) with a variety of oxidants promote the Mitsunobu-type coupling reactions of alcohols with phenols, carboxylic acids, and phthalimide. Experiments using a chiral alcohol indicate that these reactions proceed via SN1 or SN2 pathways depending on the polarity of the used solvents. The NHCs are consumed as reducing reagents to form their oxides as readily separable byproducts.

A novel method for a mild copper-catalyzed selective monoalkylation of active methylene compounds with various alkylsilyl peroxides has been developed. The reaction has a broad substrate scope and our mechanistic studies suggest the participation of radical species in this alkylation reaction.

An Fe(OTf)₂-catalyzed three-component coupling reaction of α,β,γ,δ-unsaturated carbonyl compounds with alkylsilyl peroxides in the presence of certain heteronucleophiles (ROH and indole) is realized under mild reaction conditions. A variety of α,β,γ,δ-diene carbonyl substrates with different substituents were successfully employable via combination with several different alkylsilyl peroxides. This new approach is also applicable to the double functionalization of diene substrates.

The formation of two carbon-carbon bonds using vinylarenes with alkylsilyl peroxides and β-keto carbonyl substrates is effected by the presence of catalytic Fe(OTf)₂ under mild reaction conditions. A variety of vinylarenes with different substituents can be utilized in combination with several different alkylsilyl peroxides and β-keto carbonyl substrates.

A highly efficient, site-selective benzylic C-H bond amination of two different benzylic ether substrates was described by using bowl-shaped <i>N</i>-hydroxyimide organoradical catalysts with diethyl azodicarboxylate. The synthetic utility of this approach is demonstrated by the subsequent transformation of the amination products into the corresponding aldehydes and alkylhydrazines.