Innovative carbon radical generation from hydrocarbons through a catalytic process under mild conditions has been achieved by the use of
N-hydroxyphthalimide (NHPI) as a catalyst. This method can be ...successfully applied to a wide variety of functionalizations of hydrocarbons. Thus, alkanes are converted into alcohols, ketones, and carboxylic acids, through alkyl radicals generated by the action of NHPI. Cyclohexane was directly converted into adipic acid with O
2 by NHPI combined with Mn(OAc)
2.
p-Xylene was oxidized to terephthalic acid in 95% yield by using an NHPI analogue as a catalyst. Alkenes could be epoxidized with H
2O
2 generated in situ from benzhydrol and O
2 under the influence of NHPI.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Commercially available and air- and moisture-stable rhodium complex Rh(OH)(cod)2 (2) was utilized in the synthesis of RhX(cod)(NHC) (3). The presence of an OH group in complex 2 serves as an internal ...base, facilitating the deprotonation of the C–H bond of the azolium ring in the hydroxyamide-substituted benzimidazolium salt 1. This reaction between 1 and 2 proceeded in THF at room temperature without temperature control, affording the desired NHC/Rh complex 3 in excellent yield. The characterization of complex 3 was accomplished through NMR and HRMS analyses, revealing its existence as a diastereomeric mixture of two NHC/Rh complexes. Furthermore, its catalytic performance was briefly evaluated in the reaction between 2-naphthaldehyde (5) and phenylboronic acid (6).
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Previously, we demonstrated the synthesis of a well-defined hydroxyalkyl-functionalized N-heterocyclic carbene (NHC)/Ru(II) complex through the transmetalation reaction between RuCl2(p-cymene)2 and ...the corresponding NHC/Ag(I) complex derived from a chiral benzimidazolium salt using the Ag2O method. In this study, we successfully synthesized RhX(cod)(NHC) complexes through a one-pot deprotonation route. The hydroxyalkyl-substituted benzimidazolium salt reacted with Rh(OH)(cod)2 in THF at room temperature, affording the corresponding monodentate NHC/Rh(I) complex in nearly quantitative yield. The rhodium complex was characterized using NMR, HRMS measurement, and elemental analysis.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A switchable enantioselectivity was achieved in a Cu-catalyzed asymmetric conjugate addition (ACA) reaction. The ethylene-bridged, hydroxyamide-functionalized NHC-AgI complex, readily accessible from ...a chiral β-amino alcohol, was found to be a versatile chiral ligand precursor for dual enantioselective control. The stereocontrol of the catalytic ACA reaction depended on the order of addition of the substrates. To a THF solution containing CuOTf (6 mol %), NHC-AgI complex (1b, R1 = Et, R2 = Bn, 4 mol %), and 2-cyclohexen-1-one (3) was added Et2Zn to yield (R)-3-ethylcyclohexanone ((R)-4) in 74% enantioselectivity (method A). In stark contrast, when 3 was added as a last component to a mixture of CuOTf (4 mol %), 1b (10 mol %), and Et2Zn in THF (method B), the ACA reaction afforded (S)-4 with 87% ee. In order to obtain an insight into various aspects of the present ACA reaction, the chiral NHC ligand precursors, substrates, and NHC skeletons were fully evaluated. A study of the relationship between the catalyst ee (eecat) and the product ee (eepro) revealed a chiral amplification phenomenon. Moreover, it was found that the ACA reaction using method A was not affected by the halide ion on the NHC-AgX complex, whereas the halide ion on the silver complex showed a significant influence on the enantiocontrol of the ACA reaction using method B. In particular, a Cu/NHC/I catalytic ratio of 1/1/2 was needed for a successful ACA reaction using method B. According to these factors affecting the reversal of enantioselectivity in the ACA reaction, a possible reaction pathway was proposed.
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•A small library of the ethylene-bridged, hydroxyamide-functionalized NHC-AgI complexes was prepared.•The stereoselectivity in the conjugate addition reaction with the CuOTf/NHC-AgI system was inverted by changing the order of addition of the substrates.•The choice of the NHC skeleton in addition to the introduction of a chiral carbon center at an appropriate position on the NHC side-arm was an important feature.•The catalytically active species seems to contain Cu, a chiral NHC, and the iodide ion in a 1/1/2 ratio.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hydroxyamide-functionalized azolium salt (NHC•HI 4) was evaluated for dual enantioselective control in a Cu-catalyzed asymmetric conjugate addition (ACA) reaction. This investigation was based on our ...previously reported ACA reaction catalyzed using CuOTf combined with NHC•AgI complex 1. It was revealed that the stereocontrol of the catalytic ACA reaction depended on the order of the addition of the substrates. Additionally, the chiral NHC ligand precursors, substrates, the relationship between the catalyst ee (eecat) and product ee (eepro), and halogen counter anion were completely evaluated. These results suggested that the catalytic performance of the CuOTf/4 system was comparable with that of the CuOTf/1 system. Furthermore, to gain knowledge of the Cu species generated using CuOTf and NHC ligand precursor, the reaction of CuOTf with 1 was investigated. Although obtaining the corresponding NHC•CuX species failed, the corresponding NHC•AuCl complex 11 could be synthesized by allowing 1 to react with AuCl•SMe2.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A new monodentate iridium(III) complex bearing a readily accessible and tunable chiral hydroxy-amide functionalized N-heterocyclic carbene (NHC) ligand has been synthesized and characterized by ...crystallographic methods. The monodentate NHC–Ir complex acts as a catalyst precursor for the stereoselective transfer hydrogenation of acetophenone in the presence of KOH even at room temperature.
A new monodentate iridium(III) complex bearing a readily accessible and tunable chiral hydroxy-amide functionalized N-heterocyclic carbene ligand, Cp
∗Ir(NHC)Cl
2, has been synthesized and characterized by crystallographic methods. The monodentate Cp
∗Ir(NHC)Cl
2 complex was found to act as a catalyst precursor for the stereoselective transfer hydrogenation of acetophenone in the presence of KOH even at room temperature. Moderate enantioselectivity was observed in the initial screening of the chiral ligands.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In April 2018, the Clinical Trials Act pertaining to investigator-initiated clinical trials was passed in Japan. The purpose of this study was to investigate activity in investigator-initiated ...clinical studies before and after enforcement of the new Clinical Trials Act. This was done by analysing the records of the Ethics Committee of Tokushima University Hospital, which reviews studies based on the Japanese government’s Ethical Guidelines for Medical and Health Research Involving Human Subjects prior to the Clinical Trials Act, and records of the Certified Review Board established at Tokushima University under the Clinical Trials Act in 2018. The number of new applications to these two review boards during fiscal years 2015–2017 (pre-Act) and fiscal years 2018 and 2019 (post-Act) were used as an indicator of activity in investigator-initiated clinical studies. The number of new applications to the Ethics Committee was 303, 261, 316, 303, and 249 in 2015, 2016, 2017, 2018, and 2019, respectively. The data show that the total number of new interventional studies decreased from 50.3 in average in 2015–2017 (pre-Act) to 42 in 2018 and 40 in 2019 (post-Act), respectively. These results suggest that fewer interventional studies were started following enforcement of the new Clinical Trials Act. To confirm this trend and identify contributing factors, further studies are required. In addition, possible way, such as broader contribution of clinical research coordinators, to promote clinical studies in the new Clinical Trials Act era should be examined.
Search for new element (1) Morita, Kosuke; Sakaguchi, Satoshi
Journal of the Atomic Energy Society of Japan,
2022, Volume:
64, Issue:
12
Journal Article
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