- Delivering 2-Aryl Benzoxazoles through Metal-Free and Redox-Neutral De-CF3Process
-
An unexpected cleavage of the Csp3-CF3 bond of CF3-hydrobenzoxazoles has been disclosed, affording a range of 2-aryl benzoxazoles under metal-free and redox-neutral conditions. This transformation has demonstrated broad substrate scope and good compatibility of functional groups. 2-Aryl benzothiazole and 2-aryl benzoimidazole could be smoothly assembled in the same manner. On the basis of preliminary mechanistic studies, base initiated and aromatization driven β-carbon elimination was considered to be the key step for the formation of 2. This reaction offers an alternative, facile, and sustainable route to access important 2-aryl benzoxazole motifs.
- Qiao, Xinxin,Zhao, Yong-De,Rao, Mingru,Bu, Zhan-Wei,Zhang, Guangwu,Xiong, Heng-Ying
-
p. 13548 - 13558
(2021/10/01)
-
- Bimetallic Cooperative Catalysis for Decarbonylative Heteroarylation of Carboxylic Acids via C-O/C-H Coupling
-
Cooperative bimetallic catalysis is a fundamental approach in modern synthetic chemistry. We report bimetallic cooperative catalysis for the direct decarbonylative heteroarylation of ubiquitous carboxylic acids via acyl C-O/C-H coupling. This novel catalytic system exploits the cooperative action of a copper catalyst and a palladium catalyst in decarbonylation, which enables highly chemoselective synthesis of important heterobiaryl motifs through the coupling of carboxylic acids with heteroarenes in the absence of prefunctionalization or directing groups. This cooperative decarbonylative method uses common carboxylic acids and shows a remarkably broad substrate scope (>70 examples), including late-stage modification of pharmaceuticals and streamlined synthesis of bioactive agents. Extensive mechanistic and computational studies were conducted to gain insight into the mechanism of the reaction. The key step involves intersection of the two catalytic cycles via transmetallation of the copper–aryl species with the palladium(II) intermediate generated by oxidative addition/decarbonylation.
- Liu, Chengwei,Ji, Chong-Lei,Zhou, Tongliang,Hong, Xin,Szostak, Michal
-
p. 10690 - 10699
(2021/04/09)
-
- Visible Light-Induced Copper-Catalyzed C—H Arylation of Benzoxazoles?
-
A general method for visible light-induced copper-catalyzed arylation of sp2 C—H bonds of azoles has been developed. The method employs aryl halide as the coupling partner, lithium alkoxide as base. A variety of azoles including benzooxazole and benzothiazole can be arylated. Furthermore, electron-poor heterocycles such as thiophene possessing one electron-withdrawing group can also be arylated.
- Ma, Xiaodong,Zhang, Guozhu
-
supporting information
p. 1299 - 1303
(2020/08/05)
-
- Facile access to libraries of diversely substituted 2-aryl-benzoxazoles/benzothiazoles from readily accessible aldimines via cyclization/cross coupling in imidazolium-ILs with Pd(OAc)2 or NiCl2 (dppp) as catalyst
-
A two-step protocol involving Pd-catalyzed cyclization of readily accessible p-bromophenyl-aldimines to 2-bromophenyl-benzoxazole/benzothiazole in [BMIM][PF6] or [BMIM][BF4] as solvent, followed by the Suzuki, Heck, and Sonogashira cross-coupling reactions catalyzed by Pd or Ni is described that generates libraries of diversely substituted 2-aryl-/heteroaryl-benzoxazoles/benzothiazoles in respectable isolated yields under mild reaction conditions. The feasibility to perform the two-steps in sequence in one-pot starting from the aldimines is also demonstrated and the potential for recycling/reuse of the IL solvent is also shown.
- Malunavar, Shruti S.,Sutar, Suraj M.,Savanur, Hemantkumar M.,Kalkhambkar, Rajesh G.,Laali, Kenneth K.
-
-
- Ni-Catalyzed C?F Bond Functionalization of Unactivated Aryl Fluorides and Corresponding Coupling with Oxazoles
-
A Ni-catalyzed C?F bond functionalization of unactivated aryl fluorides with oxazoles as coupling partners was developed. Various arylated oxazoles could be obtained in moderate to good yields in the presence of Ni(cod)2/IMes catalytic system.
- Yin, Youzhi,Yue, Xiaoyu,Zhong, Qi,Jiang, Hanmin,Bai, Ruopeng,Lan, Yu,Zhang, Hua
-
supporting information
p. 1639 - 1643
(2018/03/21)
-
- p-Toluenesulfonic acid-catalyzed metal-free formal [4?+?1] heteroannulation via N[sbnd]H/O[sbnd]H/S[sbnd]H functionalization: One-pot access to 2-aryl/hetaryl/alkyl benzazole derivatives
-
A concise and direct one-pot [4?+?1] synthetic strategy for the construction of 2-substituted benzazoles such as benzoxazoles and benzothiazoles has been disclosed in high yields (80–98%) by cascade coupling reaction of 2-amino(thio)phenols with β-oxodithioesters. The current approach enables N[sbnd]H/O[sbnd]H/S[sbnd]H functionalization in one-pot under solventless condition leading to diverse benzazoles without use of any external metal. A wide range of 2-amino(thio)phenols and β-oxodithioesters are compatible toward this transformation with excellent functional group tolerance. Furthermore, we preempt the wider implications of this novel strategy by demonstrating its compatibility toward versatile diversification of DNA Topoisomerase-II inhibitors.
- Srivastava, Abhijeet,Shukla, Gaurav,Singh, Maya Shankar
-
p. 879 - 887
(2017/01/25)
-
- High-Throughput Screening Protocol for the Coupling Reactions of Aryl Halides Using a Colorimetric Chemosensor for Halide Ions
-
Mercury complex of 4-(2-pyridylazo)resorcinol (PAR-2Hg2+), a halide-ion chemosensor, was prepared and its efficiency as a tool for high-throughput screening (HTS) of transition-metal-catalyzed coupling reactions was investigated. It showed a high selectivity for halide ions. When the PAR-2Hg2+ complex was used in the Suzuki coupling reaction and C-H activated coupling reaction with aryl bromides, the quantitative and qualitative conversions of aryl halides were obtained from the reaction mixture color change.
- Eom, Min Sik,Noh, Jieun,Kim, Han-Sung,Yoo, Soyeon,Han, Min Su,Lee, Sunwoo
-
supporting information
p. 1720 - 1723
(2016/05/19)
-
- S8-Mediated Cyclization of 2-Aminophenols/thiophenols with Arylmethyl Chloride: Approach to Benzoxazoles and Benzothiazoles
-
A metal-free approach to benzazoles from arylmethyl chlorides and 2-mercaptan/2-hydroxyanilines using elemental sulfur as a traceless oxidizing agent has been developed. The reactions proceeded in good to excellent yields, exhibiting good functional groups tolerance and gram-scale ability. A key mechanistic investigation indicated that the key intermediate trisulfide 6, which was characterized by NMR, HRMS and crystal X-ray crystallography, was separated in the reaction prior to the formation of the product.
- Gan, Haifeng,Miao, Dazhuang,Pan, Qiang,Hu, Renhe,Li, Xiaotong,Han, Shiqing
-
supporting information
p. 1770 - 1774
(2016/07/07)
-
- Palladium-catalyzed coupling of azoles or thiazoles with aryl thioethers via C-H/C-S activation
-
Palladium-catalyzed cross-coupling via the Csp2-S bond activation of aryl thioethers and the C-H bond activation of azoles or thiazoles was carried out. Electron-deficient and -rich aryl methyl thioethers and diaryl thioethers can be employed as the coupling partners and the reaction tolerates a range of functional groups including MeO, CF3, CN, PhCO, CONEt2, and Py groups.
- Zhu, Feng,Wang, Zhong-Xia
-
supporting information
p. 1601 - 1604
(2015/03/30)
-
- Highly phosphorescent iridium(III) complexes based on 2-(biphenyl-4-yl)benzo[d]oxazole derivatives: Synthesis, structures, properties and DFT calculations
-
Five new bis-cyclometalated iridium(iii) complexes, [(bpbo)2Ir(acac)] (3a), [(fbpbo)2Ir(acac)] (3b), [(Mebpbo)2Ir(acac)] (3c), [(3,5-f2bpbo)2Ir(acac)] (3d) and [(2,4-f2bpbo)2Ir(acac)] (3e) (bpbo = 2-(biphenyl-4-yl)benzo[d]oxazole, fbpbo = 2-(4′-fluoro-[biphenyl]-4-yl)benzo[d]oxazole, Mebpbo = (4′-methyl-[biphenyl]-4-yl)benzo[d]oxazole, 3,5-f2bpbo = 2-(3′,5′-difluoro-[biphenyl]-4-yl)benzo[d]oxazole, 2,4-f2bpbo = 2-(2′,4′-difluoro-[biphenyl]-4-yl)benzo[d]oxazole, acac = acetylacetone), have been synthesized and fully characterized. A single crystal X-ray diffraction study was carried out on complexes 3a-3d, which showed that each adopted the distorted octahedral coordination geometry with the cis-C,C′ and trans-N,N′ arrangement. All Ir(iii) complexes are luminescent (560-566 nm) with quantum yields of 3.6-53.5% and lifetimes of 0.282-0.382 μs in solution at 298 K. The spectroscopic and redox characterisation of these complexes were complemented by DFT and TD-DFT calculations, supporting the assignment of 3MLCT/LC to the emissive character.
- Niu, Zhi-Gang,Zheng, Tao,Su, You-Hui,Wang, Peng-Jiang,Li, Xiao-Yan,Cui, Feng,Liang, Jiao,Li, Gao-Nan
-
p. 6025 - 6033
(2015/08/06)
-
- An iron and copper system catalyzed C-H arylation of azoles with arylboronic acids
-
An efficient, environmentally friendly, and economical new method for arylation reactions of azoles with arylboronic acids via copper-iron-catalyzed C-H and C-B bond activation has been developed. The protocol tolerates a series of functional groups, such as methoxy, nitro, cyano, chloro, and trifluoromethyl groups.
- Hu, Wei-Ye,Wang, Pei-Pei,Zhang, Song-Lin
-
supporting information
p. 42 - 48
(2015/02/02)
-
- Aerobic oxidation of alcohols and the synthesis of benzoxazoles catalyzed by a cuprocupric coordination polymer (Cu+-CP) assisted by TEMPO
-
A Cu+-CP based on the tetranuclear unit {[(HSQPA)2Cu4(bipy)4]·2H2O}n·2nH2O has been constructed through Cu2+ salt, 2-(sulfonylquinlium-8-yloxy)phthalic acid (H3SQPA), and 4,4′-bipyridine (bipy). This Cu+-CP combined with 2,2,6,6-tetramethylpiperidine-1-oxyl as the cocatalyst is an effective catalyst for aerobic oxidation of alcohols and the synthesis of benzoxazoles and can be recycled at least four times without losing its catalytic activity.
- Feng, Xun,Xu, Chen,Wang, Zhi-Qiang,Tang, Si-Fu,Fu, Wei-Jun,Ji, Bao-Ming,Wang, Li-Ya
-
supporting information
p. 2088 - 2090
(2015/03/18)
-
- Solid-phase synthesis of benzazoles, quinazolines, and quinazolinones using an alkoxyamine linker
-
An alkoxyamine linker was applied for the solid-phase synthesis of benzazoles, quinazolines, and quinazolinones. Aromatic aldehydes were anchored by aldoxime linkage. After some reactions on a solid support, the products were cleaved with paraformaldehyde under the acidic conditions to afford the corresponding aldehydes, which were subsequently subjected to oxidative coupling with 2-substituted anilines under air atmosphere to give the desired compounds.
- Yamaguchi, Kota,Noda, Takeshi,Higuchi, Yusuke,Aoki, Naoyuki,Yamaguchi, Rika,Kubo, Miwa,Harada, Kenichi,Fukuyama, Yoshiyasu,Hioki, Hideaki
-
p. 5793 - 5797
(2015/02/18)
-
- Synthesis of 2-substituted pyrimidines and benzoxazoles via a visible-light-driven organocatalytic aerobic oxidation: Enhancement of the reaction rate and selectivity by a base
-
An efficient visible-light-driven photocatalytic oxidation of various 2-substituted dihydropyrimidines and phenolic imines has been achieved using an organic photocatalyst eosin Y bis(tetrabutyl ammonium salt) (TBA-eosin Y) and inexpensive oxidant molecular oxygen. With the aid of a base, significantly enhanced photoinduced electron transfer from substrates dihydropyrimidines or phenolic imines to the excited state of TBA-eosin Y has enabled the aerobic oxidation to yield 2-(methylthio)pyrimidines or 2-arylbenzoxazoles selectively. This journal is the Partner Organisations 2014.
- Wang, Lin,Ma, Zhi-Gang,Wei, Xiao-Jing,Meng, Qing-Yuan,Yang, Deng-Tao,Du, Shao-Fu,Chen, Zi-Fei,Wu, Li-Zhu,Liu, Qiang
-
supporting information
p. 3752 - 3757
(2014/08/05)
-
- Nickel-catalyzed ligand-free synthesis of benzoxazoles and oxazolines via isocyanide insertion
-
A novel and efficient route to benzoxazoles and oxazolines involving a nickel-catalyzed three-component coupling reaction of iodobenzene, an amino alcohol and tert-butyl isocyanide has been developed. A wide array of products have been prepared in good to excellent yields in the absence of ligand.
- Wang, Jin-Mei,Jiang, Xiao,Tang, Ting,Zhu, Yong-Ming,Shen, Jing-Kang
-
p. 1441 - 1453
(2014/07/07)
-
- METHOD FOR PRODUCING PHENYL-SUBSTITUTED HETEROCYCLIC DERIVATIVE
-
The present invention is a method for producing a phenyl-substituted heterocyclic derivative represented by general formula (1), which has a step wherein a heteroaromatic compound represented by general formula (2) is reacted with a phenol derivative represented by general formula (3) in the presence of a nickel compound, 1,2-bis(dicyclohexylphosphino)ethane, and a base.
- -
-
Paragraph 0058-0062; 0105-0106
(2014/09/29)
-
- Catalytic Staudinger/aza-Wittig sequence by in situ phosphane oxide reduction
-
A Staudinger/aza-Wittig reaction sequence is described that is catalytic in phosphorus. Towards this end, the phosphane oxide is reduced in situ by diphenylsilane, which allows for substoichiometric amounts of the catalyst 5-phenyldibenzophosphole to be used. The substrate scope is investigated and benzoxazoles, benzodiazepine imidates and a 2-methoxypyrrole were successfully synthesized. These investigations show that a fast aza-Wittig reaction is required to obtain high yields. A catalytic Staudinger/aza-Wittig reaction sequence, involving in situ phosphane oxide reduction, was successfully developed. Benzoxazoles, benzodiazepine imidates and 2-methoxypyrrole were synthesized without phosphane oxide waste products. Copyright
- Van Kalkeren, Henri A.,Te Grotenhuis, Colet,Haasjes, Frank S.,Hommersom,Rutjes, Floris P. J. T.,Van Delft, Floris L.
-
supporting information
p. 7059 - 7066
(2013/11/06)
-
- Iodine-mediated arylation of benzoxazoles with aldehydes
-
A simple and efficient methodology for the arylation of benzoxazoles with aldehydes using iodine as the mediator has been developed. The reaction proceeded smoothly with a range of substrates to give the corresponding arylated products in moderate to good yields.
- Teo, Yew Chin,Riduan, Siti Nurhanna,Zhang, Yugen
-
supporting information
p. 2365 - 2368
(2013/09/12)
-
- Palladium-catalyzed desulfitative C-arylation of a benzo[d]oxazole C-H bond with arene sulfonyl chlorides
-
A palladium-catalyzed direct desulfitative C-arylation of a benzo[d]oxazole C-H bond with arene sulfonyl chlorides is described. The procedure tolerates halo, cyano, nitro, trifluoromethyl, acetyl and acetylamino groups on the phenyl ring of sulfonyl chlorides, providing the arylation products in moderate to good yields. It represents a practical and attractive alternative for the synthesis of 2-aryl benzoxazoles.
- Zhang, Manli,Zhang, Shouhui,Liu, Miaochang,Cheng, Jiang
-
supporting information; experimental part
p. 11522 - 11524
(2011/11/12)
-
- Direct arylation of benzothiazoles and benzoxazoles with aryl boronic acids
-
A breath of fresh air: Without the need for organohalide precursors, the convenient and general synthesis of aryl-substituted benzothiazoles and benzoxazoles can be achieved by use of aryl boronic acids through direct arylation reactions catalyzed by a bimetallic system (see scheme).
- Ranjit, Sadananda,Liu, Xiaogang
-
supporting information; experimental part
p. 1105 - 1108
(2011/04/16)
-
- Palladium-catalyzed direct arylations, alkenylations, and benzylations through C-H bond cleavages with sulfamates or phosphates as electrophiles
-
(Figure Presented) catalytic system comprised of Pd(OAc)2 and bldentate ligand dppe enabled first direct arylatlons with moisture-stable aryl sulfamates as electrophlles, and proved applicable to unprecedented C-H bond functlonallzations with e
- Ackermann, Lutz,Barfuesser, Sebastian,Pospech, Jola
-
supporting information; experimental part
p. 724 - 726
(2010/04/02)
-
- Efficient one-step synthesis of benzazoles in aqueous media
-
Benzazoles (benzoxazoles, benzothiazoles, and benzimidazoles) were efficiently prepared by the aquatic reaction of the corresponding thioamidinium salts and 2-aminophenol, 2-aminothiophenol, and 1,2-diaminobenzene, respectively. The thioamidinium salt was successfully applied as an alternative to a carboxylic acid derivative to react smoothly with an amino precursor and in the presence of catalytic amounts of hexadecyltrimethylammonium bromide salt to produce benzazoles in good to excellent yields. Wiley-VCH Verlag GmbH & Co. KGaA 2009.
- Boeini, Hassan Zali,Najafabadi, Khadijeh Hajibabaei
-
supporting information; experimental part
p. 4926 - 4929
(2010/01/18)
-
- LIGAND-COUPLING IN THE ALKALINE HYDROLYSIS OF ARYLPHOSPHONIUM SALTS
-
Biaryls are formed via a ligand-coupling process in the alkaline hydrolysis of a series of tetraarylphosphonium salts which bear electron-withdrawing substituents in the para position of one of the aryl rings.Key words: Biaryls; tetraarylphosphonium salt hydrolysis; hypervalent intermediates.
- Allen, David W.,Benke, Peter
-
p. 259 - 262
(2007/10/02)
-
- Synthesis of 2-Arylbenzoxazoles via the Palladium-Catalyzed Carbonylation and Condensation of Aromatic Halides and o-Aminophenols
-
A new synthetic method is reported in which 2-arylbenzoxazoles can be prepared by palladium-catalyzed condensation of aryl halides with o-aminophenols followed by dehydrative cyclization.This method is tolerant of a wide variety of functional groups on either aromatic ring and gives good to excellent yields of products.An aliphatic vicinal amino alcohol gave a bis-acylated product as well as a chlorine-containing product with only a small amount of the desired 2-aryloxazole being formed.Methyl iodide and benzyl bromide gave only alkylated products.
- Perry, Robert J.,Wilson, B. David,Miller, Richard J.
-
p. 2883 - 2887
(2007/10/02)
-
- Synthesis of heterocyclic compounds
-
A new synthetic method is reported in which 2-arylbenz(ox,imid,thi)azoles can be prepared by the palladium catalyzed condensation of aromatic halides with o-amino(phenol, aniline, thiophenol)s followed by dehydrative cyclization. This method is tolerant of a wide variety of functional groups on either aromatic ring and gives good to excellent yields of products.
- -
-
-