- Selective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex
-
We report the catalytic reduction of a C-O bond and the borylation by a rhodium complex bearing an X-Type PAlP pincer ligand. We have revealed the reaction mechanism based on the characterization of the reaction intermediate and deuterium-labeling experiments. Notably, this novel catalytic system shows steric-hindrance-dependent chemoselectivity that is distinct from conventional Ni-based catalysts and suggests a new strategy for selective C-O bond activation by heterobimetallic catalysis.
- Hara, Naofumi,Nakao, Yoshiaki,Saito, Teruhiko,Seki, Rin
-
supporting information
p. 6388 - 6394
(2021/05/31)
-
- Iridium(iii) complex-based electrochemiluminescent probe for H2S
-
Since abnormal levels of hydrogen sulphide (H2S) correlate with various diseases, simple methods for its rapid and sensitive detection are highly required. Herein, we introduce a new electrochemiluminescent probe 1 for H2S based on a cyclometalated iridium(iii) complex. o-(Azidomethyl)benzoate ester groups on the main ligands of probe 1 react selectively with H2S, resulting in cascade reactions involving H2S-mediated reduction and intramolecular cyclization/ester cleavage. With this structural change induced by H2S, the intrinsic electrochemiluminescence (ECL) of 1 decreased greatly due to the unfavourable electron transfer of a tripropylamine (TPA) radical. Probe 1 showed a high ECL turn-off ratio and good selectivity for H2S over various anions and biothiols. The sensing mechanism of H2S was elucidated using1H NMR spectroscopy and MALDI-TOF mass spectrometry analyses.
- Park, Joonho,Kim, Taemin,Kim, Hoon Jun,Hong, Jong-In
-
p. 4565 - 4573
(2019/04/05)
-
- Transition-Metal-Free Decarboxylative Arylation of 2-Picolinic Acids with Arenes under Air Conditions
-
A facile, transition-metal-free, and direct decarboxylative arylation of 2-picolinic acids with simple arenes is described. The oxidative decarboxylative arylation of 2-picolinic acids with arenes proceeds readily via N-chloro carbene intermediates to afford 2-arylpyridines in satisfactory to good yields under transition-metal-free conditions. This new type of decarboxylative arylation is operationally simple and scalable and exhibits high functional-group tolerance. Various synthetically useful functional groups, such as halogen atoms, methoxycarbonyl, and nitro, remain intact during the decarboxylative arylation of 2-picolinic acids.
- Zhang, Xitao,Feng, Xiujuan,Zhou, Chuancheng,Yu, Xiaoqiang,Yamamoto, Yoshinori,Bao, Ming
-
supporting information
p. 7095 - 7099
(2018/11/23)
-
- Ruthenium-Catalyzed meta-Selective C?H Mono- and Difluoromethylation of Arenes through ortho-Metalation Strategy
-
The first example for the ruthenium-catalyzed ligand-directed meta-selective C?H mono- and difluoromethylation is developed, affording a variety of new meta-mono- and difluoromethylated 2-phenylpyridines, 2-phenylpyrimidines, and 1-phenylpyrazoles in moderate-to-good yields. This new transformation exhibits broad substrate scope, good functional group tolerance, and high efficiency, and offers a practical approach to synthesize mono- and difluoromethylated arenes. Mechanistic studies indicate that a reaction pathway involving palladium-initiated radical species is involved in the catalytic cycle. The new dual catalytic system consisting of compatible ruthenium(II) and palladium(0) complexes enables the key processes of C?H activation and mono-/difluoromethyl-radical formation to occur and achieves the meta-selective functionalization efficiently. In addition, the present protocol can also be extended to non-fluoromethylation.
- Li, Zhong-Yuan,Li, Liang,Li, Qi-Li,Jing, Kun,Xu, Hui,Wang, Guan-Wu
-
supporting information
p. 3285 - 3290
(2017/03/16)
-
- METHODS FOR EXTERNAL BASE-FREE SUZUKI COUPLINGS
-
The present disclosure describes a method of coupling a first aromatic compound to a second aromatic compound, the method comprising: (a) preparing a reaction mixture comprising the first aromatic compound, the second aromatic compound, a catalyst and water; the reaction mixture does not contain an external base, the reaction mixture having an initial pH of from 11 to 1; the catalyst having at least one group 10 atom; the first aromatic compound having a halogen, triflate or sulfonate substituent; the second aromatic compound having a boron-containing substituent; wherein, at least one of the first aromatic compound or the second aromatic compound includes one or more heteroatom; and (b) reacting the first aromatic compound and the second aromatic compound in the reaction mixture, the reaction mixture having a final pH following reaction of the first aromatic compound and the second aromatic compound.
- -
-
Paragraph 0035-0036
(2017/07/14)
-
- Aqueous Suzuki Coupling Reactions of Basic Nitrogen-Containing Substrates in the Absence of Added Base and Ligand: Observation of High Yields under Acidic Conditions
-
A series of aqueous heterogeneous Suzuki coupling reactions of substrates containing basic nitrogen centers with phenylboronic acid in the absence of added base and ligand is presented. High yields of products were obtained by employing aryl bromides containing aliphatic 1°, 2°, and 3° amine substituents, and good to high yields were obtained by employing a variety of substituted bromopyridines. In the former series, the pH of the aqueous phase changed from basic to acidic during the course of the reaction, while in the latter series the aqueous phase was on the acidic side of the pH scale throughout the entire course of reaction. A mechanistic interpretation for these observations, which generally preserves the oxo palladium catalytic cycle widely accepted in the literature, is presented.
- Li, Zhao,Gelbaum, Carol,Fisk, Jason S.,Holden, Bruce,Jaganathan, Arvind,Whiteker, Gregory T.,Pollet, Pamela,Liotta, Charles L.
-
p. 8520 - 8529
(2016/09/28)
-
- Room-temperature Suzuki-Miyaura coupling of heteroaryl chlorides and tosylates
-
Suzuki-Miyaura coupling of heteroaryls is an important method for the preparation of compound libraries for medicinal chemistry and materials research. Although many catalysts have been developed, none of them have been generally applicable to the coupling reactions of heteroaryl chlorides and tosylates at room temperature. We discovered that a catalyst combination of Pd(OAc)2 and XPhos (2-dicyclohexylphosphanyl-2',4',6'- triisopropylbiphenyl) could efficiently catalyze these couplings. Besides the choice of catalyst, the use of hydroxide bases in an aqueous alcoholic solvent was essential for fast couplings. These conditions promoted fast release of active catalyst (XPhos)Pd0, and accelerated the transmetalation in the catalytic cycle. Most of the major families of heteroaryl chlorides (31 examples) and tosylates (17 examples) reached full conversion within minutes to hours at room temperature. The method could be easily scaled up for gram-scale synthesis. Furthermore, we examined the relative reactivity of coupling partners in whole reactions. Electron-rich heteroaryl chlorides and tosylates reacted more slowly than electron-deficient ones, in the order of indole, pyrrole furan, thiophene > pyridine. Similarly, electron-deficient arylboronic acids were less reactive than electron-neutral and electron-rich ones. The reactivity trends from this study can help to choose appropriate coupling partners for Suzuki reactions.
- Yang, Junfeng,Liu, Sijia,Zheng, Jian-Feng,Zhou, Jianrong
-
supporting information
p. 6248 - 6259,12
(2020/09/16)
-
- Mild and ligand-free palladium-catalyzed cross-couplings between aryl halides and arylboronic acids for the synthesis of biaryls and heterocycle-containing biaryls
-
Ligand-free palladium-catalyzed Suzuki-Miyaura cross-couplings between aryl halides and arylboronic acids performed at room temperature are presented. It was found that both solvent and base had a fundamental influence on the reaction, and the most effective system in terms of yield and rate was observed to be the combination of Pd(OAc)2 with MeONa and alcohols. In the presence of Pd(OAc)2 and MeONa, a variety of aryl halides reacted very rapidly with arylboronic acids in good to excellent yields at room ternperature in EtOH as the solvent. Moreover, the Pd(OAc)2/MeONa catalytic system could also be applied in couplings between heteroaryl halides and arylboronic acids to provide satisfactory results in MeOH as the solvent after prolonged reaction times. It is noteworthy that the reactions were conducted under mild, aerobic, and ligand-free conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Deng, Chen-Liang,Guo, Sheng-Mei,Xie, Ye-Xiang,Li, Jin-Heng
-
p. 1457 - 1462
(2008/09/18)
-
- PREPARATION OF PYRIDINE DERIVATIVES USING PYRIMIDINIUM DERIVATIVES AS INTERMEDIATES
-
A method in which a pyridinium derivative of formula (I) such as 1,3-dimethyl-2,3-dihydro-2-oxopyrimidinium chloride is reacted with an acetyl compound of formula (II) such as 4-acetylpyridine, and then the reaction product is reacted with ammonia or an ammonium salt to form a pyridine derivative of formula (III):Also disclosed is a method for the preparation of the compound of formula (I) from reacting a compound of formula (IV) or (V) with a compound of formula (VI):Also disclosed are two additional alternative methods for the preparation of compounds of formula (I) and related compounds. The substituents are defined in the claims.
- -
-
Page/Page column 23-24
(2008/06/13)
-