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Cu-Catalyzed Direct C-P Bond Formation through Dehydrogenative Cross-Coupling Reactions between Azoles and Dialkyl Phosphites
A direct dehydrogenative cross-coupling of azoles [C(sp2)-H] with dialkyl phosphites [P(O)-H] to access 2-phosphonated azoles using Cu(I)/Cu(II) as catalyst and K2S2O8/di-tert-butylperoxide as oxidant has been achieved. A remarkable advantage over reported procedures includes that oxazoles, imidazoles, benz(ox/othi/imid)azoles, and indole are found to react under optimized reaction conditions to provide corresponding adducts in high yields. The mechanistic insight of cross-coupling was obtained by deuterium kinetic isotope effect studies.
Hore, Soumyadip,Srivastava, Abhijeet,Singh, Ravi P.
p. 6868 - 6878
(2019)
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Mild and efficient synthesis of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines catalyzed by Bi(III) salts under solvent-free conditions
A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3- hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts, such as Bi(TFA)3, Bi(OTf)3, and BiOClO4 ? xH2O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts. Springer-Verlag 2007.
Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad R.,Hojati, Seyedeh F.
p. 663 - 667
(2007)
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Palladium-catalyzed direct phosphonation of azoles with dialkyl phosphites
The first Pd-catalyzed direct phosphonation of azoles with dialkyl phosphites has been achieved without addition of base or acid. This method involves the oxidative cleavage of C-H and P(O)-H bonds and represents an atom-efficiency alternative to the classical phosphonation of Ar-X. A Pd II/PdIV mechanism has been studied and proposed.
Hou, Chaodong,Ren, Yunlai,Lang, Rui,Hu, Xiaoxue,Xia, Chungu,Li, Fuwei
p. 5181 - 5183
(2012)
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1,3-Dibromo-5,5-dimethylhydantoin as an efficient homogeneous catalyst for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines
A simple and highly efficient method for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines is described. Condensation of orthoesters with o-substituted anilines or 2-amino-3-hydroxypyridine was performed in the presence of catalytic amounts of commercially available, inexpensive, and moisture-stable 1,3-dibromo-5,5-dimethylhydantoin under solvent-free conditions. The corresponding heterocycles were obtained in good to excellent yields. The main advantages of the present procedure are mild reaction conditions, short reaction times, high yields of products, easy work-up, and absence of solvent. Graphical abstract: [Figure not available: see fulltext.]
Hojati, Seyedeh Fatemeh,Maleki, Behrooz,Beykzadeh, Zahra
p. 87 - 91
(2011)
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Unsymmetrical Pincer N -Heterocyclic Carbene-Nitrogen-Phosphine Chelated Palladium(II) Complexes: Synthesis, Structure, and Reactivity in Direct Csp2-H Arylation of Benzoxazoles
An unsymmetrical pincer N-heterocyclic carbene-nitrogen-phosphine (CNP) and its palladium complexes PdCl2(κ2-CP) (4) and [PdCl(κ3-CNP)]PF6 (5·PF6) were synthesized. NMR spectra disclosed that the transformation of complex 4 structure occurred in the solution. Further NMR experimental and single crystal structure analysis of complex 4 provided unequivocal and structural evidence for the formation of complex [PdCl(κ3-CNP)]Cl (5·Cl) in the solution of complex 4. The catalytic performance of palladium complexes 4 and 5·PF6 was investigated with the direct Csp2-H arylation of benzoxazoles with aryl bromides. Notably, aryl bromides could give up to 97% arylation products in the presence of 0.5% complex 4. For ortho-substituted substrates, the steric hindrance had a significant impact, but product yields could be improved remarkably by extending reaction time. This result implied the catalytic active species in this system was stable and kept in a long lifetime. The flexible backbone and unsymmetrical pincer structure with a flank N-heterocyclic carbine should be a feasible strategy to realize an efficient catalytic transformation. This simple catalyst system first realized the direct arylation of aryl bromides with a catalyst loading as low as 0.25% without excessive base and copper as assistant catalyst.
Li, Yaqiu,Yu, Xiaojun,Wang, Yangdiandian,Fu, Haiyan,Zheng, Xueli,Chen, Hua,Li, Ruixiang
p. 979 - 988
(2018)
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Tungstate sulfuric acid as an efficient catalyst for the synthesis of benzoxazoles and benzothiazoles under solvent-free conditions
Tungstate sulfuric acid (TSA) has been found to be an efficient and reusable catalyst for the synthesis of benzoxazole and benzothiazole derivatives via reactions of orthoesters with o-aminophenols or o-aminothiophenols in high yields.
Farahi, Mahnaz,Karami, Bahador,Azari, Masume
p. 1029 - 1034
(2013)
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Room-temperature palladium-catalyzed direct 2-arylation of benzoxazoles with aryl and heteroaryl bromides
An efficient room-temperature palladium-catalyzed direct 2-arylation of benzoxazoles with aryl bromides is presented. The Pd(OAc)2/ NiXantphos-based catalyst enables the introduction of various aryl and heteroaryl groups, via a deprotonative cross-coupling process (DCCP) in good to excellent yields (60-99%). This journal is the Partner Organisations 2014.
Gao, Feng,Kim, Byeong-Seon,Walsh, Patrick J.
p. 10661 - 10664
(2014)
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Synthesis of benzimidazoles and benzoxazoles using palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) as a novel catalyst
Structurally well-defined palladium bis(2,2,6,6-tetramethyl-3,5- heptanedionate) complex is reported to be an efficient catalyst for the synthesis of benzimidazole and benzoxazole derivatives in good yields. A novel approach for one-pot synthesis of benzimidazoles via direct reductive amination and N-arylation followed by hydrogenation-cyclization methodology is also described. Copyright
Bhor, Malhari D.,Bhanage, Bhalchandra M.
p. 1743 - 1749
(2010)
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Design, synthesis and biological evaluation of benz-fused five-membered heterocyclic compounds as tubulin polymerization inhibitors with anticancer activities
A series of benz-fused five-membered heterocyclic compounds were designed and synthesized as novel tubulin inhibitors targeting the colchicine binding site. Among them, compound 4d displayed the highest antiproliferative activity against four cancer cell lines with an IC50 value of 4.9?μM in B16-F10 cells. Compound 4d effectively inhibited tubulin polymerization in vitro (IC50 of 13.1?μM). Further, 4d induced cell cycle arrest in G2/M phase. Finally, 4d inhibited the migration of cancer cells in a dose-dependent manner. In summary, these results suggest that compound 4d represents a new class of tubulin inhibitors deserving further investigation.
Komuraiah, Buduma,Ren, Yichang,Xue, Mingming,Cheng, Binbin,Liu, Jin,Liu, Yao,Chen, Jianjun
p. 1109 - 1116
(2021/03/16)

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)

Room-temperature palladium-catalyzed direct 2-alkenylation of azole derivatives with alkenyl bromides
Pd-catalyzed direct C2-alkenylation of azole derivatives proceeds efficiently under mild conditions, and the reaction of substituted benzoxazoles, oxazole and benzothiazole occurred even at room temperature. The substrate scope of the reaction was turned out to include mono-, di- and trisubstituted alkenyl bromides. To validate the scalability of this method, 5-Methyl-2-(prop-1-en-2-yl)benzoxazole (3c) was prepared on one-gram scale at room temperature.
Yao, Yun-Xin,Fang, Dong-Mei,Gao, Feng,Liang, Xiao-Xia
supporting information
p. 68 - 71
(2018/12/05)

Method for synthesizing benzoxazole through microwave radiation of benzamide compound in water phase
The invention discloses a method for synthesizing benzoxazole through microwave radiation of a benzamide compound in a water phase. The benzamide compound is added into the water phase under the microwave condition to be subjected to a cyclization reaction for generating the benzoxazole under the alkali condition, and the method for preparing the benzoxazole is environmentally friendly, easy and convenient to operate, safe, low in cost and efficient. Compared with the prior art, the method can be applied to a large number of functional groups, the yield is high, the number of by-products is small, and the method is easy to operate, safe, low in cost and environmentally friendly. (Please see the specifications for the formula).
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(2019/03/08)

Method of coupling, and the coupling method using the aromatic group-substituted heterocyclic compound
Provided is an easy method (coupling method) capable of easily synthesizing a compound group in which aromatic molecules and aromatic molecules are coupled, a compound group in which aromatic molecules and alkene molecules are coupled, and the like without producing halogen waste and without the need to use scarce and expensive palladium. A compound (A) shown by general formula (A): Ar-H and a compound (B1) shown by general formula (B1): RaOCO-Ar', a compound (B2) shown by general formula (B2): RbCH=C(Ar")2, or a compound (B3) shown by general formula (B3): RcOCOCH=C(Ar")2 are reacted in the presence of a nickel compound.
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Paragraph 0196-0198

(2020/09/17)

Direct C-H iodination of 1,3-azoles catalysed by CuBr2
A mild method was developed for the direct C-H iodination of 1,3-azoles catalysed by CuBr2. Compared with the traditional metalation/iodination sequences carried out with nBuLi or TMPLi (TMP = 2,2,6,6-tetramethylpiperidino), a relatively weaker base, LiOtBu, was used in the presence of 1,10-phenanthroline. Five series of 1,3-azoles, including benzoxazole, benzothiozole, N-methyl-benzoimidazole, 5-phenyloxazole and 2-phenyl-1,3,4-oxadiazole were tested and afforded the corresponding iodination products.
Zhao, Xia,Ding, Fang,Li, Jingyu,Lu, Kui,Lu, Xiaoyu,Wang, Bin,Yu, Peng
supporting information
p. 511 - 513
(2015/02/19)

Application of nano SnO2 as a green and recyclable catalyst for the synthesis of 2-aryl or alkylbenzoxazole derivatives under ambient temperature
Application of nano SnO2 as an efficient and benign catalyst has been explored for the synthesis of 2-aryl or alkylbenzoxazole derivatives via condensation reaction of aldehyde with 2-aminophenol. The reactions proceed under heterogeneous and mild conditions in ethanol at room temperature to provide 2-aryl or alkylbenzoxazoles in high yields.
Vahdat, Seyed Mohammad,Raz, Shima Ghafouri,Baghery, Saeed
p. 579 - 585
(2014/07/07)

A green and efficient protocol for the synthesis of quinoxaline, benzoxazole and benzimidazole derivatives using heteropolyanion-based ionic liquids: As a recyclable solid catalyst
In this paper, we introduce two nonconventional ionic liquid compounds which are composed of propane sulfonate functionalized organic cations and heteropolyanions as green solid acid catalysts for the highly efficient and green synthesis of 2,3-disubstitutedquinoxaline derivatives. These ionic liquids are in the solid state at room temperature and the synthesis is carried out via the one-pot condensation reaction of various o-phenylenediamine with 1,2-diketone derivatives. Benzoxazole and benzimidazole derivatives were also synthesized by these novel catalysts via the one-pot condensation from reaction orthoester with o-aminophenol (synthesis of benzoxazole derivatives) and ophenylenediamine (synthesis of benzimidazole derivatives). All experiments successfully resulted in the desired products. The described novel synthesis method has several advantages of safety, mild condition, high yields, short reaction times, simplicity and easy workup compared to the traditional method of synthesis.
Vahdat, Seyed Mohammad,Baghery, Saeed
p. 618 - 627
(2013/09/12)

C-H alkenylation of azoles with enols and esters by nickel catalysis
Rather u(Ni)que: Two new C-H alkenylation reactions, that is C-H/Ci￡O alkenylation and decarbonylative C-H alkenylation, of azoles are uniquely catalyzed by Ni/dcype. These azole alkenylation reactions are successfully applied to the convergent formal synthesis of siphonazoleB.
Meng, Lingkui,Kamada, Yuko,Muto, Kei,Yamaguchi, Junichiro,Itami, Kenichiro
supporting information
p. 10048 - 10051
(2013/10/01)

Copper-mediated C-H/C-H biaryl coupling of benzoic acid derivatives and 1,3-azoles
Hot couple: A precious-metal-free copper-mediated intermolecular direct biaryl coupling of benzoic acid derivatives and 1,3-azoles has been developed. The key to success is the installation of an amide-based bidentate coordinating group, which is easily removed and transformed into the parent ester groups after the coupling reaction. Kinetic studies indicate that the rate-limiting step is the aromatic C-H bond cleavage of benzoic acid derivatives. Copyright
Nishino, Mayuko,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
supporting information
p. 4457 - 4461
(2013/05/22)

Room-temperature copper-catalyzed oxidation of electron-deficient arenes and heteroarenes using air
No pressure: The oxidation of aromatic C-H bonds at room temperature was realized through a copper-catalyzed "oxygenase-type" oxidation of arenes and heteroarenes in the presence of air (see scheme). The reaction involves an oxygen-atom transfer from O2 in the air onto the substrates. Copyright
Liu, Qiang,Wu, Pan,Yang, Yuhong,Zeng, Ziqi,Liu, Jie,Yi, Hong,Lei, Aiwen
supporting information; experimental part
p. 4666 - 4670
(2012/06/30)

Direct arylation of benzoxazole C-H bonds with iodobenzene diacetates
A Pd (OAc)2-catalyzed direct arylation of benzoxazole C-H bonds has been achieved with iodobenzene diacetates as the arylation reagent in moderate to good yields. The procedure tolerates a series of functional groups, such as methoxy, nitro, cyano, chloro, and bromo groups.
Yu, Peng,Zhang, Guangyou,Chen, Fan,Cheng, Jiang
supporting information; experimental part
p. 4588 - 4590
(2012/09/22)

Nickel-catalyzed C-H direct amination of benzoxazoles with secondary amines
In this article, a facile, efficient and practical method for Ni-catalyzed direct C-H amination of benzoxazole with secondary amines has been developed. This procedure requires Ni(OAc)2·4H2O as catalyst, TBHP as oxidant and acid as the additive. A variety of substituted benzoxazol-2-amines were synthesized in moderate to good yields.
Li, Yaming,Liu, Jin,Xie, Yusheng,Zhang, Rong,Jin, Kun,Wang, Xiuna,Duan, Chunying
supporting information; experimental part
p. 3715 - 3720
(2012/05/21)

Copper-mediated and copper-catalyzed cross-coupling of indoles and 1,3-azoles: Double C-H activation
A new bronze age: The described copper-mediated cross-coupling with double C-H activation can provide a convergent access to indole-containing biheteroaryls that are of high interest in pharmaceutical and medicinal chemistry. In this strategy an easily attachable and detachable 2-pyrimidyl directing group is used. Moreover, a variant that is catalytic in copper is achieved by using atmospheric oxygen as an ideal co-oxidant (see scheme). Copyright
Nishino, Mayuko,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
supporting information; experimental part
p. 6993 - 6997
(2012/10/07)

Palladium-catalyzed direct arylation of heteroarenes with aryl mesylates
Not so challenging after all! The first general examples of the direct arylation of heteroarenes by using challenging aryl mesylates as electrophiles are disclosed. These easy reaction conditions also allow the functionalization of other heterocycles, such as caffeine, triazole and benzathiazole (see scheme). Copyright
So, Chau Ming,Lau, Chak Po,Kwong, Fuk Yee
supporting information; experimental part
p. 761 - 765
(2011/03/20)

Amination of benzoxazoles and 1,3,4-oxadiazoles using 2,2,6,6- tetramethylpiperidine-N-oxoammonium tetrafluoroborate as an organic oxidant
No transition metals are necessary to convert benzoxazoles and 1,3,4-oxadiazoles into the corresponding pharmacologically interesting 2-aminated heterocycles by formal direct C(2)-amination using tetramethylpiperidine-N-oxoammonium tetrafluoroborate (TEMPO+BF 4-) as an oxidant (see scheme; TEMP=2,2,6,6- tetramethylpiperidine; TfOH=trifluoromethanesulfonic acid).
Wertz, Sebastian,Kodama, Shintaro,Studer, Armido
supporting information; experimental part
p. 11511 - 11515
(2012/01/11)

Copper-catalyzed oxidative amination of benzoxazoles via C-H and C-N bond activation: A new strategy for using tertiary amines as nitrogen group sources
An efficient and conceptually new method for oxidative amination of azoles with tertiary amines via copper-catalyzed C-H and C-N bond activation has been developed. This protocol can be performed in the absence of external base and only requires atmospheric oxygen as oxidant. The catalyst system is very simple and efficient, which opens a new way for using tertiary amines as nitrogen group sources for C-N bond formation reactions.
Guo, Shengmei,Qian, Bo,Xie, Yinjun,Xia, Chungu,Huang, Hanmin
experimental part
p. 522 - 525
(2011/04/18)

Copper-catalyzed direct oxidative C-H amination of benzoxazoles with formamides or secondary amines under mild conditions
A facile, efficient, and practical method for copper-catalyzed direct C-H amination of benzoxazoles with formamides or secondary amines has been developed. The system can be performed in the absence of external base and only requires O2 or even air as oxidant. A variety of substituted benzoxazol-2-amines were synthesized with moderate to excellent yield.
Li, Yaming,Xie, Yusheng,Zhang, Rong,Jin, Kun,Wang, Xiuna,Duan, Chunying
supporting information; experimental part
p. 5444 - 5449
(2011/08/06)

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)

Cobalt- and manganese-catalyzed direct amination of azoles under mild reaction conditions and the mechanistic details
A bonding moment: A new cobalt- or manganese-catalyzed amination of azoles has been developed using peroxide and an acid additive to couple various types of azoles with ammonia, and primary or secondary amines (see scheme). The catalyst loadings are low, the optimal reaction conditions are mild, and the substrate scope is broad. The product azoles are an important pharmacophore of high biological activity. Copyright
Kim, Ji Young,Cho, Seung Hwan,Joseph, Jomy,Chang, Sukbok
supporting information; experimental part
p. 9899 - 9903
(2011/02/25)

Carbon dioxide as the C1 source for direct C-H functionalization of aromatic heterocycles
(Equation Presented). A simple and straightforward method has been developed for the direct carboxylation of aromatic heterocylces such as oxazoles, thiazoles, and oxadiazoles using CO2 as the C1 source. The reactions require no metal catalyst and only Cs2CO3 as the base. A good functional group tolerance is achieved.
Vechorkin, Oleg,Hirt, Nathalie,Hu, Xile
supporting information; experimental part
p. 3567 - 3569
(2010/10/02)

Indium-mediated one-pot synthesis of benzoxazoles or oxazoles from 2-nitrophenols or 1-aryl-2-nitroethanones
One-pot reduction-triggered heterocyclizations from 2-nitrophenols to benzoxazoles and from 1-aryl-2-nitroethanones to oxazoles were investigated. In the presence of indium/AcOH in benzene at reflux, 2-nitrophenols and R-C(OMe)3 (R=H, Me, Ph) produced excellent yields of corresponding benzoxazoles within an hour. Similarly, 1-aryl-2-nitroethanones and Ph-C(OMe)3 in the presence of indium/AcOH in acetonitrile transformed into the corresponding oxazoles with good yields.
Lee, Jung June,Kim, Jihye,Jun, Young Moo,Lee, Byung Min,Kim, Byeong Hyo
experimental part
p. 8821 - 8831
(2009/12/26)

ONE ATOM LYNCH PIN TRANSFORMATIONS OF GOLD'S REAGENT
A series of o-phenylenediamines and o-aminophenols have been reacted with Gold's reagent to yield benzimidazoles and benzoxazoles, respectively.Additionally, o-hydroxyacetophenone and anthranilamide, when reacted with Gold's reagent, were found to produce chromone and 3H-quinazoline-4-one, respectively.These transformations represent the use of Gold's reagent as a one atom lynch pin.
Gupton, John T.,Correia, Keith F.,Foster, Bruce S.
p. 365 - 376
(2007/10/02)