1826-17-1Relevant academic research and scientific papers
PdII-Catalyzed Regio- and Enantioselective Oxidative C?H/C?H Cross-Coupling Reaction between Ferrocenes and Azoles
Cai, Zhong-Jian,Liu, Chen-Xu,Gu, Qing,Zheng, Chao,You, Shu-Li
supporting information, p. 2149 - 2153 (2019/01/24)
Asymmetric C?H bond functionalization reaction is one of the most efficient and straightforward methods for the synthesis of optically active molecules. Herein we disclose an asymmetric C?H/C?H cross-coupling reaction of ferrocenes with azoles such as oxazoles and thiazoles. Palladium(II)/monoprotected amino acid (MPAA) catalytic system which exhibits excellent reactivity and regioselectivity for oxazoles and thiazoles. This method offers a powerful strategy for constructing planar chiral ferrocenes. Mechanistic studies suggest that the C?H bond cleavage of azoles is likely proceeding through a SEAr process and may not be a turnover limiting step.
Decarbonylative Methylation of Aromatic Esters by a Nickel Catalyst
Okita, Toshimasa,Muto, Kei,Yamaguchi, Junichiro
, p. 3132 - 3135 (2018/05/28)
A Ni-catalyzed decarbonylative methylation of aromatic esters was achieved using methylaluminums as methylating agents. Dimethylaluminum chlorides uniquely worked as the methyl source. Because of the Lewis acidity of aluminum reagents, less reactive alkyl esters could also undergo the present methylation. By controlling the Lewis acidity of aluminum reagents, a chemoselective decarbonylative cross-coupling between alkyl esters and phenyl esters was successful.
C-H arylation and alkenylation of imidazoles by nickel catalysis: Solvent-accelerated imidazole C-H activation
Muto, Kei,Hatakeyama, Taito,Yamaguchi, Junichiro,Itami, Kenichiro
, p. 6792 - 6798 (2015/11/24)
The first nickel-catalyzed C-H arylations and alkenylations of imidazoles with phenol and enol derivatives are described. Under the influence of Ni(OTf)2/dcype/K3PO4 (dcype: 1,2-bis(dicyclohexylphosphino)ethane) in t-amyl alcohol, imidazoles can undergo C-H arylation with phenol derivatives. The C-H arylation of imidazoles with chloroarenes as well as that of thiazoles and oxazoles with phenol derivatives can also be achieved with this catalytic system. By changing the ligand to dcypt (3,4-bis(dicyclohexylphosphino)thiophene), enol derivatives could also be employed as coupling partners achieving the C-H alkenylation of imidazoles as well as thiazoles and oxazoles. Thus, a range of C2-arylated and alkenylated azoles can be synthesized using this newly developed nickel-based catalytic system. The key to the success of the C-H coupling of imidazoles is the use of a tertiary alcohol as solvent. This also allows the use of an air-stable nickel(ii) salt as the catalyst precursor.
Pd/Cu-cocatalyzed reigoselective arylation of thiazole derivatives at 2-position under ligand-free conditions
Gu, Jian,Cai, Chun
, p. 56311 - 56315 (2015/07/15)
An efficient protocol for regioselective arylation of thiazole derivatives at the 2-position via palladium- and copper-catalyzed C-H bond activation under ligand-free conditions has been developed. The reaction proceeds smoothly with 1% palladium catalyst in the presence of 20% Cu(TFA)2 to furnish the desired products. The direct C-H arylation and no ligand made this method synthetically useful for the arylation of thiazoles at the 2-position.
Nickel-catalyzed C-H arylation of azoles with haloarenes: Scope, mechanism, and applications to the synthesis of bioactive molecules
Yamamoto, Takuya,Muto, Kei,Komiyama, Masato,Canivet, Jerome,Yamaguchi, Junichiro,Itami, Kenichiro
experimental part, p. 10113 - 10122 (2011/10/08)
Novel nickel-based catalytic systems for the C-H arylation of azoles with haloarenes and aryl triflates have been developed. We have established that Ni(OAc)2/bipy/LiOtBu serves as a general catalytic system for the coupling with aryl bromides and iodides as aryl electrophiles. For couplings with more challenging electrophiles, such as aryl chlorides and triflates, the Ni(OAc)2/dppf (dppf=1,1′-bis(diphenylphosphino)ferrocene) system was found to be effective. Thiazoles, benzothiazoles, oxazoles, benzoxazoles, and benzimidazoles can be used as the heteroarene coupling partner. Upon further investigation, we discovered a new protocol for the present coupling using Mg(OtBu)2 as a milder and less expensive alternative to LiOtBu. Attempts to reveal the mechanism of this nickel-catalyzed heterobiaryl coupling are also described. This newly developed methodology has been successfully applied to the syntheses of febuxostat (a xanthine oxidase inhibitor that is effective for the treatment of gout and hyperuricemia), tafamidis (effective for the treatment of TTR amyloid polyneuropathy), and texaline (a natural product having antitubercular activity). Copyright
Decarboxylative C-H cross-coupling of azoles
Zhang, Fengzhi,Greaney, Michael F.
body text, p. 2768 - 2771 (2010/07/04)
(Figure Presented) Cote d'Azole: The title reaction demon-strates the use of diverse oxazoles 2 as suitable substrates in cross-coupling reactions with azole-5-carboxylic acids 1 under palladium catalysis in the presence of copper carbonate. The reaction
A facile synthesis of 2,4-disubstituted thiazoles using MnO2
Yu, Yan-Bo,Chen, Hong-Liang,Wang, Li-Yi,Chen, Xin-Zheng,Fu, Bin
experimental part, p. 4858 - 4865 (2010/04/05)
Structurally diverse thiazoles with electron-donating and electron-withdrawing groups were conveniently synthesized through manganese dioxide (MnO2) oxidation of the corresponding thiazolines. The effect of substitution at the 2- and 4-positions was investigated. The desired thiazoles with aryl or vinyl substitutions at the 2- or 4-position can be obtained in good to excellent yields.
Direct α-oxytosylation of carbonyl compounds: One-pot synthesis of heterocycles
John, Oliver R. S.,Killeen, Niall M.,Knowles, Deborah A.,Yau, Sze Chak,Bagley, Mark C.,Tomkinson, Nicholas C. O.
, p. 4009 - 4012 (2008/02/11)
N-Methyl-O-tosylhydroxylamine is an effective reagent for the direct α-oxytosylation of carbonyl compounds. The reactions proceed smoothly at room temperature in the presence of both moisture and air and functional group tolerance in the substrate is good. With nonsymmetrical substrates regioselectivity for primary over secondary centers is observed and complete regiospecificity for primary over tertiary centers is obtained. Addition of a bis-heteronucleophile directly to the crude reaction mixture in a one-pot process leads to the corresponding heterocyclic product.
Palladium-Catalyzed Reactions of Terminal Acetylenes and Olefins with Halo-1,3-azoles
Sakamoto, Takao,Nagata, Hideo,Kondo, Yoshinori,Shiraiwa, Masafumi,Yamanaka, Hiroshi
, p. 823 - 828 (2007/10/02)
The palladium-catalyzed reactions of 4-bromo- and 5-bromothiazoles, as well as 4-bromo and 5-bromooxazoles with terminal acetylenes gave ethynyl derivatives in 43-89percent yields, whereas the reactions of 2-bromothiazoles and iodo-N-methylimidazoles affo
