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Versatile applications and unique performance of 1,1’-bis(diphenylphosphanyl)ferrocene (dppf) in coordination chemistry and catalysis prompted the search for its analogs. This contribution describes the synthesis of the first donor-unsymmetric dppf congeners bearing bulky and rigid 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphaadamantyl (CgP) donor groups, viz. Ph2PfcPCg (1) and Ph2PfcCH2PCg (2; fc=ferrocene-1,1’-diyl). Bis-phosphanes 1 and 2 were converted into air-stable Pd(0) complexes, [Pd(ma)(L^L)] (L^L=1 and 2; ma=maleic anhydride). Together with [Pd(ma)(dppf)], these complexes were applied as catalysts in Pd-catalyzed C?H arylation of benzoxazoles with aryl chlorides in n-butanol as an environmentally benign solvent. Among all catalysts tested in this study, complex [Pd(ma)(2)] performed the best, providing a high-yield and selective synthesis of 2-arylbenzoxazoles from a range of the generally less reactive chloroarenes at low catalyst loading (typically 1 mol.%). Under similar conditions, the structurally related heterocycles (e. g., 1-methylbenzimidazole and benzothiazole) did not react.

In this work simple efficient, one pot and environmentally friendly method was developed for the synthesis of 2-Aryl-1H-benzoxazole derivatives at 80oC using ortho-aminophenol and various aldehydes. It has been found that Dowex 50W is an effective catalyst to prepare moderate to high yield of a variety of benzoxazole derivatives through a clean and simple process. Aqueous medium, green methodology, rapid reaction, reusability of heterogeneous catalyst are the great advantages of this protocol.

Heterogeneous copper catalysis enabled photoinduced C?H arylations under exceedingly mild conditions at room temperature. The versatile hybrid copper catalyst provided step-economical access to arylated heteroarenes, terpenes and alkaloid natural products with various aryl halides. The hybrid copper catalyst could be reused without significant loss of catalytic efficacy. Detailed studies in terms of TEM, HRTEM and XPS analysis of the hybrid copper catalyst, among others, supported its outstanding stability and reusability.

Four mononuclear and dinuclear pyrazole-3-carboxylates assisted NHC–Pd complexes have been synthesized and characterized. Notably, the bridge-cleavage reactions of [Pd(μ-Cl)(Cl)(NHC)]2 with 1H-pyrazole-3-carboxylic acid afforded dinuclear complexes [(NHC)Pd(μ-1H-pyrazolato-3-carboxylate)]2, in which the 1H-pyrazolato-3-carboxylate was employed as a N^N^O dianionic chelating and bridging ligand. To further explore the structural features and catalytic properties of the complexes, 1-methyl-1H-pyrazole-3-carboxylic acid was introduced into the coordination with [Pd(μ-Cl)(Cl)(NHC)]2 and the corresponding mononuclear complexes (NHC)PdCl(1-methyl-1H-pyrazole-3-carboxylate) were obtained. The catalytic properties of the complexes in desulfitative arylation of azoles with arylsulfonyl hydrazides were initially investigated.

Sulfur/DABCO was found to be an efficient reagent in promoting- the reductive coupling/annulation of o -nitrophenols or o -nitroanilines with benzaldehydes. This method represents a simple, straightforward, and green approach to the construction of benz-oxazoles and benzimidazoles.

A series of mixed N-heterocycles/N-heterocyclic carbene palladium(II) allyl complexes with general formula [(NHC)Pd(η3-allyl)]2(μ2-N-heterocycles)(BF4)2 were prepared in one pot based on anion metathesis of (NHC)Pd(η3-allyl)Cl complexes and then ligand replacement with N-heterocycles [N-heterocycles = pyrazine (pyz), 4,4′-bipyridine (bpy) and trans-4,4′-bipyridylethylene (bpe)]. The solid-state structures shown dinuclear structures with two palladium(II) centers holding together by bridged N-heterocycles. Initially investigation of the obtained complexes as precatalysts for direct C[sbnd]H bond arylation of azoles with aryl bromides was carried out.

A highly efficient palladium-catalyzed arylation of azoles at the C2-position using 1-aryltriazenes as aryl reagents was developed. Azoles including oxazoles, thiazoles, imidazoles, 1,3,4-oxadiazoles, and oxazolines could react with 1-aryltriazenes smoothly to generate the corresponding products in good to excellent yields, and various substitution patterns were tolerated toward the reaction.

We describe herein the synthetic method to benzoxazole derivatives via the copper-catalyzed hydroamination of alkynones with 2-aminophenols. The method produced a wide variety of functionalized benzoxazole derivatives in good yields. Preliminary mechanistic experiments revealed that the reaction would proceed through the copper-catalyzed hydroamination of alkynones and the sequential intramolecular cyclization of β-iminoketones/elimination of acetophenone promoted by the copper catalyst.

A series of N-heterocyclic carboxylate-stabilized N-heterocyclic carbene palladium complexes have been synthesized and fully characterized. The solid-state structures indicate that each of the palladium centers is coordinated by an N-heterocyclic carbene, a chloride and a bidentate N,O-donor N-heterocyclic carboxylate ligand. The catalytic performance of the complexes was screened and the results revealed that the complexes exhibit moderate to high catalytic activities for the direct C─H bond arylation of benzoxazoles with aryl bromides.

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.

A novel and efficient methodology for the arylation of benzoxazoles with aromatic aldehydes catalyzed by deep eutectic solvent has been developed. The reaction smoothly proceeded with a wide range of substrates to give the desired products in high yields within short reaction time. Deep eutectic solvents are easily recovered and reused without significant loss of catalytic activity.

A highly efficient and green strategy for the synthesis of 2-Arylbenzoxazoles, 2-Arylbenzimidazoles, and 2-Arylbenzothiazoles catalyzed by phosphonium acidic ionic liquid has been developed via the condensation of o-Aminophenol, o-phenylenediamines, and o-Aminothiophenol, respectively, with aldehydes. The reaction has a good yield, the broad substrate scope, and mild condition. Triphenyl(butyl-3-sulphonyl)phosphonium toluenesulfonate catalyst was easily obtained from cheap and available starting materials through a one-pot synthesis. Its structure was identified by 1H NMR, 13C NMR, 31P NMR, and FT-IR techniques. Other properties including thermal stability and acidity were determined by TGA and Hammett acidity function method. Interestingly, the catalyst can maintain its constantly outstanding performance till the fourth recovery.

N-Heterocyclic carbene (NHC), generated in situ from easily available N-heterocyclic imidazolium salt with air as terminal oxidant, has successfully been utilized as a cheap and efficient catalyst for one-pot aerobic oxidative synthesis of 2-arylbenzo[ d ]oxazoles, 2-substituted benzo[ d ]thiazoles, and 1,2-disubstituted benzo[ d ]imidazoles.

The invention relates to a preparation method of a 2-phenylbenzoxazole compound, comprising the following steps: (1) condensation reaction: a 2-amino phenol compound and a benzoyl chloride compound, which are used as raw materials, react in an organic solvent to obtain a condensation reaction solution; and (2) cyclization reaction: as a cyclization catalyst, acid is added into the condensation reaction solution to carry out a cyclization reaction at a certain temperature so as to obtain a cyclization reaction solution; after the reaction, an organic solvent is added for heating refluxing; andcooling filtration or liquid-separation condensation is finally carried out to obtain a 2-phenylbenzoxazole compound. The technology is simple; product post-treatment is simple; environmental pollution is less; the prepared 2-phenylbenzoxazole compound has high product quality and good stability; in addition to general use purpose, the prepared product also can be used for preparation of a high-end luminescent material; and the preparation method is a method suitable for industrial preparation.

Electronic, steric and leaving group effects for Ni-catalyzed direct arylations using C?O electrophiles were benchmarked. The scope of arylations with pivalates was general with respect to both the electronics on the electrophile and the azoles. Furthermore, the arylation of azoles with tosylates, mesylates and carbamates with varying electronics was explored, and showed electronic trends similar to those of the pivalate reactions. Finally, the relative rate of arylation of 5-methyl benzoxazole with two electronically-similar electrophiles bearing different leaving groups was established. The results from these studies implicate the following order of relative reactivity: mesylates>pivalates>carbamates.

A new crystalline porous superacid material was prepared by sulfation of a Hf-MOF constructed from a 6-connected Hf node and 1,3,5-benzenetricarboxylate. The new superacid MOF with the presence of sulfate groups coordinated to a Hf-oxo cluster as superacid sites was found to be an effective heterogeneous catalyst for solvent-free heterocyclization for benzoxazole synthesis.

This work reports a simple, efficient and alternative synthetic route for the preparation of benzoxazoles via tandem cyclization of 2-halophenols with amidines. The developed methodology is free from ligands and uses inexpensive and easily available CuCl as a catalyst. This protocol avoids the use of any oxidant or inorganic acids. Various benzoxazole derivatives were synthesized in good to excellent yields. To the best of our knowledge, this is the first time that the synthesis of benzoxazoles from 2-halophenols with both aromatic and aliphatic amidines is reported. Owing to the simplicity of this protocol, the preparation of benzoxazoles could be achieved at a gram scale level.

An iron(II) bromide-catalyzed oxidative coupling of benzylamines with 2-amino/hydroxy/mercapto-anilines has been developed, allowing the synthesis of a diversity of substituted 1,3-benzazoles in good to excellent yields. This transformation is compatible with a wide range of functional groups. The method is practical, economical and employs molecular oxygen as an oxidant.

The synthesis of novel chelating palladium complexes containing pyridine/pyrimidine hydroxyalkyl di-functionalized N-heterocyclic carbenes (NHCs) via direct metallation of the precursor imidazolium salts is presented. The structure has been characterized unambiguously by X-ray single crystal analysis. Catalytic activity investigation showed that the complexes catalyse the direct C-H bond arylation of (benzo)oxazoles efficiently when using tBuOLi as base and DMF as solvent.

The facile and efficient one-pot construction of benzimidazoles and benzoxazoles through the Mo(CO)6-mediated carbonylation of aryl halides was examined. In the process, Mo(CO)6 acted as a convenient and safe solid source of carbon monoxide. A wide range of substrates were tolerated to provide the corresponding products in fair to good yields without the need of gaseous CO or palladium catalysts. The facile and efficient one-pot construction of benzimidazoles and benzoxazoles is described. The reaction proceeds through Mo(CO)6-mediated carbonylation of aryl halides, in which Mo(CO)6 acts as a convenient and safe solid source of carbon monoxide.

Well-defined and efficient POCN-ligated palladium complexes have been developed for the direct C-H bond arylation of azoles with aryl iodides. The phosphinite-amine pincer ligands 1-(R2PO)-C6H4-3-(CH2NiPr2) [R2POCNiPr2-H; R = iPr (1a), R = tBu (1b)] and corresponding palladium complexes {2-(R2PO)-C6H3-6-(CH2NiPr2)}PdCl [(R2POCNiPr2)PdCl; R = iPr (2a), R = tBu (2b)] were synthesized in good yields. Treatment of palladium complex 2a with KI and AgOAc afforded the complexes (iPr2POCNiPr2)PdI (3a) and (iPr2POCNiPr2)Pd(OAc) (4a), respectively. Similarly, the reaction of 2a with benzothiazolyl-lithium produces the (iPr2POCNiPr2)Pd(benzothiazolyl) (5a) complex in a quantitative yield. The pincer palladium complex 2a efficiently catalyzes the C-H bond arylation of benzothiazole, substituted-benzoxazoles and 5-aryl oxazoles with diverse aryl iodides in the presence of CuI as a co-catalyst under mild reaction conditions. This represents the first example of a pincer palladium complex being applied for the direct C-H bond arylation of any heterocycle with low catalyst loading. A preliminary mechanistic investigation reveals that palladium nanoparticles are presumably not the catalytically active form of 2a and supports the direct involvement of the catalyst 2a, with complex 5a being a probable key intermediate in the catalytic reaction. This journal is

In the present study, three divergent reaction paths emerged when o-haloanilides were subjected to CuO nanoparticles in water. o-Halo (I, Br) phenylbenzamides in the presence of CuO nanoparticles and Cs2CO 3 in water at 100 °C provided o-hydroxyphenyl benzamides as the major product. However, a complete change in selectivity was observed in the presence of an organic base/ligand (TMEDA), giving 2-arylbenzoxazole as the exclusive product. The above selectivities were not clearly distinct when the corresponding alkylamides were treated either in the presence or absence of the ligand. A number of o-halophenyl alkylamides provided either exclusively o-dehalogenated products or a mixture of o-dehalogenated and o-hydroxylated products, but none gave 2-alkylbenzoxazoles. In addition to the above selectivities, the use of an environmentally friendly solvent (water) and base, and the recyclability of the catalyst make this procedure a benign alternative to the existing methods for the synthesis of these molecules, viz. o-hydroxybenzamides and o-arylbenzoxazoles.

A green and efficient strategy for the synthesis of benzoxazoles, benzothiazoles and benzimidazoles has been developed by using inexpensive, readily available, dioxygen-stable and recyclable CuFe2O4 as the nanocatalyst, and o-substituted aminobenzene and various aldehydes as the starting materials. The CuFe2O4 nanoparticles are dioxygen insensitive and easily recoverable with an external magnet from the reaction medium. The catalyst can be reused ten times without significant loss of catalytic activity. This journal is the Partner Organisations 2014.

A simple, highly efficient, and sustainable strategy for the synthesis of benzoxazole and benzothiazole derivatives was developed by using inexpensive, green, readily available, and recyclable mesoporous poly(melamine-formaldehyde) as a green, heterogeneous organocatalyst. The corresponding substituted benzoxazoles and benzothiazoles were obtained in good to excellent yields by aerobic oxidation of o-substituted aminobenzenes with various aldehydes under dioxygen atmosphere. The catalyst can be completely recovered through simple filtration to be reused more than six times without significant loss of catalytic activity.

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.

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.

A highly efficient palladium-catalyzed direct desulfitative arylation of azoles at C2-position has been developed using sodium arylsulfinates as aryl sources. Azoles including benzoxazoles, benzothiazoles, oxazoles, thiazoles, and 1,3,4-oxadiazoles reacted with sodium arylsulfinates smoothly to generate the corresponding products in good to excellent yields, and various substitution patterns were tolerated toward the reaction.

Using CuBr2 as an additive, the Pd-catalyzed intermolecular C-H-C-H cross-coupling between benzoxazoles and unactivated simple arenes has been developed. This protocol provides a straightforward approach for the biological activity of 2-arylbenzoxazole derivatives.

Palladium-catalyzed desulfitative and denitrogenative arylation of azoles with arylsulfonyl hydrazides has been achieved. A broad scope of azoles and arylsulfonyl hydrazides has been used to produce arylated azoles in high yields.

This study describes a direct oxidative C-2 arylation of benzoxazoles using arylsulfonyl hydrazides as the aryl sources. A simple catalyst system [Pd(OAc)2 and Ph3P] allows the reactions to proceed smoothly under oxidative reaction conditions. Other heteroarenes such as caffeine and benzothiazole are also applicable substrates. Notably, this catalytic system tolerates halogen substituents which provides a useful complement to the current cross-coupling reactions which use aryl halides.

This study describes a direct oxidative C-2 arylation of benzoxazoles using arylsulfonyl hydrazides as the aryl sources. A simple catalyst system [Pd(OAc)2 and Ph3P] allows the reactions to proceed smoothly under oxidative reaction conditions. Other heteroarenes such as caffeine and benzothiazole are also applicable substrates. Notably, this catalytic system tolerates halogen substituents which provides a useful complement to the current cross-coupling reactions which use aryl halides. Georg Thieme Verlag KG Stuttgart · New York.

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.

A palladium-catalyzed desulfitative C-H arylation of azoles with sodium sulfinates using Cu(OAc)2·H2O as oxidant has been discovered. The reaction proceeded well for a range of different substrates under oxidative conditions. A series of aryl-substituted azoles have been synthesized in moderate to good yields.

A simple protocol for the preparation of 2-arylbenzoxazoles has been developed based on the oxidation of phenolic Schiff bases with o-iodoxybenzoic acid (IBX), wherein the oxidant can be recycled. The robustness of this new protocol has been demonstrated in the synthesis of arylbenzoxazole-containing amino acids.

An efficient synthesis of 2-substituted benzoxazoles through RuCl 3·3H2O catalyzed, air oxidized tandem reactions of 2-aminophenols and aldehydes in [bmim]BF4 was developed. This synthetic strategy has such advantages as mild reaction conditions, cost-free oxidant, readily available starting materials, and recyclable catalyst and solvent. As an application, it was successfully used in the synthesis of the unreported 5-(benzoxazol-2-yl)-2′-deoxyuridines with potential biological activities. A novel and efficient synthesis of 2-substituted benzoxazoles through RuCl3 catalyzed, air oxidized tandem reactions of 2-aminophenols and aldehydes in [bmim]BF4 was developed.

Benzoxazole derivatives have been prepared through the reaction of substituted 2-aminophenols and acyl chlorides in the presence of catalytic amount of In(OTf)3 under solvent-free reaction conditions in good to excellent yields. The method is simple, convenient, environmental-friendly, efficient and practical.

(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

Benzoxazoles are synthesised directly by oxidative condensation of primary and secondary amines with o-aminophenols under hydrogen transfer catalysis. The optimal system utilises 1 mol % of the Shvo catalyst, with dimethoxybenzoquinone as the hydrogen-acc

Benzoxazoles can be rapidly and efficiently synthesized from acyl chloride with 2-aminophenols in one simple step, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds. Copyright Taylor & Francis Group, LLC.

A simple, convenient and general method has been developed for the synthesis of 2-arylbenzoxazole via condensation of o-aminophenols and benzoyl chloride derivatives under solvent-free conditions in the presence of a catalytic amount of heteropolyacids in good yields.

Transition-metal-catalyzed hydrogen-transfer reactions have been used for the conversion of alcohols into benzimidazoles and aldehydes into benzoxazoles and benzothiazoles.

2-Arylbenzoxazoles were prepared in good yields through the intramolecular cyclization of phenolic Schiff's base in conjunction with poly[styrene(iodoso diacetate)], and the regenerated reagent kept the same activity in the reaction.

An efficient synthetic method is reported in which 2-arylbenzoxazoles have been prepared in good to excellent yields under mild reaction conditions by the palladium-catalysed carbonylation of diaryliodonium salts with o-aminophenols followed by dehydrative cyclisation.

The synthesis and microbiological activity of a series of 5-methyl-2-(p-substituted phenyl)benzoxazoles 7a-7g are described.The in vitro microbiological activity of these compounds was determined against some Gram-positive and Gram-negative bacteria and C albicans.The observed minimum inhibitory concentration (MIC) values of the derivatives were compared to some other 2,5-disubstituted benzoxazoles and clinically used drugs.The in vitro microbiological data showed that the derivatives 7a-7g exhibited a broad spectrum of antibacterial activity and 7a-c and 7g were significantly active against E coli and/or K pneumoniae at an MIC of 6.2 μg/ml.