Efficient Syntheses of 2-Substituted Benzimidazoles and Benzoxazoles from β-Keto Esters

An efficient synthetic method was developed to synthesize 2-substituted benzimidazoles and benzo- xazoles with β-keto esters as starting materials under mild reaction conditions, during which other functional groups are bearable from reactants to products.

Expeditious and Efficient Synthesis of Benzoxazoles, Benzothiazoles, Benzimidazoles Catalyzed by Ga（OTf）3 under Solvent-Free Conditions

A new and efficient method for the synthesis of benzoxazoles, benzothiazoles, benzimidazoles from reactions of o-substituted aminoaromatics with orthoesters in the presence of catalytic amounts of Ga（OTf）3 under solvent-free conditions is presented. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straight forward procedure, and use of relatively non-toxic catalysts.

An Efficient Synthesis of 2-Substituted Benzoxazoles via RuCl3.3H2O Catalyzed Tandem Reactions in Ionic Liquid

An efficient synthesis of 2-substituted benzoxazoles through RuCl3·3H2O 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.

Synthesis of substituted benzoxazoles by the iron(Ⅲ)-catalyzed aerobic oxidation process

The FeCl3-catalyzed aerobic oxidation process for the synthesis of benzoxazoles,benzothiazole and benzimidazole has been discovered.This method has proved to be effective to a wide range of substrates,and it has been applied for the synthesis of JTP-426467.

Theoretical Study of Structure, Energetic, Hydrogen Bonds Strength and Intramolecular Proton Transfer of 2-（2-R （R=OH, NH2, SH） Phenyl （or Pyridyl）） Benzoxazoles （or Benzothiazoles）

The ground- and excited-state intramolecular proton transfer processes of 2-（2-R （R=OH, NH2, SH） phenyl （or pyridyl）） benzoxazoles （or benzothiazoles） are investigated by the DFT methods. The calculated results indicate that in the ground state there is a high correlation （R=0.9950） between the proton transfer barrier and the intramolecular hydrogen bonds （IMHB） strength. The increase of the strength of IMHB in the proton transfer processes leads to a larger barrier contributions. Intramolecular proton transfer process pathway is along with the minimal difference of change value in the IMHB angle. In the excited-state, there is a similar relationship between the IMHB and the bartier.

Synthesis of a novel benzoxazine containing benzoxazole structure

A high-purity benzoxazine（Boz-BOA） containing benzoxazole structure was successfully synthesized by three-step synthetic method using 2-（4-aminophenyl）-1H-benzoxazole-5-amine（BOA） and ortho-hydroxybenzaldehyde.The structure of Boz-BOA was confirmed by FTIR and;H NMR spectra.The DSC was utilized to probe the curing behavior of Boz-BOA and exhibited a narrow melting peak and curing exothermic peak.

Two novel fluorescent calix[4]arene derivatives with benzoazole units in 1,3-alternate conformation for selective recognition to Fe^(3+) and Cr^(3+)

Two novel fluorescent calix[4]arene derivatives la and lb with benzoxazole or benzothiazole units in 1,3-alternate conformation have been synthesized and characterized by IR, ^1H NMR, ^13C NMR and MS. Their complexation properties to different heavy and transition metal ions have been studied by UV-vis spectroscopy and fluorescence spectrometer. Compounds 1a and 1b show selective recognition to Fe^3＋ and Cr^3＋.

Design,synthesis and biological estimation of 1-(benzoxazole-2-yl)piperazine and 4-(benzoxazole-2-yl)piperidine derivatives as potentialα_1-AR antagonists

Two series of 1-（benzoxazole-2-yl）piperazine （Sa-i） and 4-（benzoxazole-2-yl）piperidine compounds （10a-i） were designed, synthesized and evaluated for their α1-AR antagonistic activities. Biological assay in vitro indicated that 10h showed slightly stronger α1-AR antagonistic activity to that of our lead compound 1.

Synthesis and characterization on semi-aromatic polyamide containing benzoxazole unit

In order to obtain a novel polyamide having excellent heat-resistant properties which could be anticipated as a thermal modifier for aliphatic polyamide,a series of new semi-aromatic polyamides (BO6,BO8,BO10) containing benzoxazole unit were synthesized based on 5-amino-2-(p-aminophenyl) benzoxazole (ABO) and aliphatic acids (adipic,suberic and sebacic acid) by means of Yamazaki phosphorylation method.The effect of reaction temperature on the inherent viscosity of the polymers was studied,and the structures of products were characterized by FTIR,1 H-NMR,and the heat resistance of the polymers was studied by DSC and TG.The results showed that the reaction temperature gives the polymers the highest viscosity at around 90 ℃,130 ℃ and 130 ℃ for BO6,BO8 and BO10,respectively.The heat resistance of the new semi-aromatic polyamides is much higher than that of the common aliphatic polyamides.In addition,the products show good solvent resistance and crystallization properties.

Syntheses, Crystal Structures and Biological Activities of Three New Benzoxazole Derivatives Containing Pyridyl Moiety

Three novel benzoxazole derivatives based on the pyridyl group were designed and synthesized from 2-methylbenzoxazole and three different types of pyridylaldehyde.Their structures were confirmed by HRMS,1H NMR,13C NMR and IR.Among them,the crystal structures of compounds 1 and 3 were also determined by single-crystal X-ray diffraction.Compound 1 crystallizes in monoclinic system,space group P21/c with a=0.66725(4),b=1.04750(7),c=1.61138(10)nm,β=93.884(2)o,V=1.12368(12)nm3,Z=4,Dc=1.314 g/cm3,μ=0.085 mm-1,F(000)=464,R=0.0731 and wR=0.2412.Compound 3 crystallizes in monoclinic system,P21/c space group with a=0.6585(7),b=1.3840(7),c=2.5364(6)nm,β=103.4220(4)o,V=2.249(3)nm3,Z=8,Dc=1.313 g/cm3,μ=0.085 mm-1,F(000)=928,R=0.0584 and wR=0.1151.The three compounds were screened for their antitumor activities against the human cancer HepG2 cells in vitro by MTT assay.All compounds could inhibit the proliferation of HepG2 cells,whose IC50 values are 87.7,9.6 and 33.5μmol/L for compounds 1,2 and 3,respectively.Most noticeably of all,the inhibition rate of complex 2 was up to 85%at 100μmol/L.

Theoretical Study on the Reaction Mechanism of o-Aminophenol, Acetic Acid and Phosphorus Oxytrichloride One-pot to Form 2-Methyl Benzoxazole

The reaction mechanism of o-aminophenol, acetic acid and phosphorus oxytrichloride in one-pot to form 2-methyl benzoxazole was studied by density functional theory. The geometries of the reactants, transition states, intermediates and products were optimized at the GGA/PW91/DNP level. Vibration analysis was carried out to confirm the transition state structure. Two possible reaction pathways were investigated in this study. The result indicates that the reaction Re→TS1→IM1→TSA2→IMA2→TSA3→IMA3→TSA4→IMA4→TSA5→P2 is the main pathway, the activation energy of which is the lowest. Re→TS1→IM1 is the rate-limiting step, with the activation energy being 221.54 kJ·mol;and the reaction heat being 10.06 kJ·mol;. The dominant product predicted theoretically is in agreement with the experiment results.

STUDIES ON CROWN ETHER CYANINE DYES (X). THE SYNTHESIS OF BENZOXAZOLE CROWN ETHER CYANINE DYES

A simple method for synthesis of benoxazole crown ether cyanine dyes is described.

Design, Synthesis and Biological Evaluation of Novel Antitubercular Agents by Combining Pyrazoline and Benzoxazole Pharmacophores

Various recent reports on Tuberculosis have alarmed an increase in the patient class and subsequent death rates across the globe. Over and above the spread of more dangerous and fatal forms of tuberculosis like MDR-TB i.e. multiple-drug resistance tuberculosis, XDR-TB i.e. extensively-drug resistance tuberculosis & TDR-TB i.e. total-drug resistance tuberculosis has forwarded an urgent need to discover novel antitubercular agents. The current work is aimed at combining two previously well-known pharmacophores (pyrazoline and benzoxazole nucleus) in order to design and synthesize a series of novel benzoxazole-based pyrazoline derivatives. The synthesized target compounds were structurally confirmed by LCMS, 1H-NMR and 13C-NMR analysis. The target compounds were In vitro evaluated against M. tuberculosis H37Rv strain, multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) strains. The In vitro screening results depicted that majority of the target compounds displayed potent activity with MIC in a range of ~0.8 to 6.25 μg/mL. Many compounds were found to be more potent than isoniazid against MDR-TB with MIC value 3.12 μg/mL and XDR-TB with MIC value 12.5 μg/mL. Cytotoxicity assay of these active compounds on VERO cell lines also displayed good selectivity index.

Corrosion Inhibition Studies of Benzoxazole Derivates for N80 Steel in 1 M HCl Solution: Synthesis, Experimental, and DTF Studies

Three benzoxazole corrosion inhibitors, namely 2-(benzo [d]oxazol-2-yl)phenol (BOP), 6-(benzo [d]oxazol-2-yl)pyridin-2-ol (BOPO), and 2-(quinolin-2-yl) benzo [d]oxazole (QBO), were synthesized. Moreover, their corrosion inhibition performance for N80 steel in 1 M HCl solution at 303 K was measured by the electrochemical measurements and surface analysis studies. The results show that the inhibition efficiency of all corrosion inhibitors increases with the increase of concentration. At the same concentration, the order of inhibition efficiency is BOP < BOPO < QBO. Moreover, the studied inhibitors act as mixed-type inhibitors, and the adsorption of all inhibitors on N80 steel followed the Langmuir adsorption isotherm. Further, we have examined the effect of iodide ions on inhibition efficiency. The results show that BOP and KI are synergistic, BOPO and QBO are competitive adsorptions with KI. The quantum chemical parameters such as highest occupied molecular orbital, lowest unoccupied molecular orbital energy levels, and energy gap were calculated by the density functional theory (DTF). The relations between the inhibition efficiency and some quantum parameters have been discussed. The protective effect of the three inhibitors followed the sequence of BOP < BOPO < QBO. The results obtained from quantum chemicals and electrochemical were in reasonable agreement.

Heterocyclic benzoxazole-based liquid crystals:Synthesis and mesomorphic properties

New Schiff base liquid crystals containing benzoxazole core and alkanoyloxy chain at the end group of the molecules （C_（n-1）H_（2n-1）COO-,n=14,16,18） was synthesized.The present compounds are enantiotropic smectic A liquid crystals.It was also found that the end groups of the molecules and polar chloro substituent at the benzoxazole fragment had effect on the mesomorphic properties.

Simple and efficient protocol for the synthesis of benzoxazole,benzoimidazole and benzothiazole heterocycles using Fe(Ⅲ)–Schiff base/SBA-15 as a nanocatalyst

Benzimidazoles, benzoxazoles, and benzothiazoles derivatives were synthesized from condensation of aldehydes and 1,2-phenylenediamine or ortho-aminophenol or ortho-aminothiophenol in the presence of catalytic amount of Fe（Ⅲ）-Schiff base/SBA-15 in water medium. Short reaction times, good to excellent yields, easy availability, reusability, and use of an eco-friendly catalyst are some of the significant attributes of the present method.

Design,synthesis and screening of some novel benzoxazole based 1,3,4-oxadiazoles as potential antimicrobial agents

A series of novel 2-（5-substituted-[ 1,3,4]oxadiazol-2-yl）-benzoxazoles （Ta-h） were synthesized in good yields in two different directions by involving benzoxazole-2-carboxylic acid （1） as raw material and benzoxazole-2-carbonyl chloride （2）, benzoxazole-2-carboxylic acid methyl ester （3）, benzoxazole-2- carboxylic acid hydrazide （4）, benzoxazole-2-carboxylic acid N＇-acetyl hydrazide （Sa-d） and benzoxazole-2-carboxylic acid-ethylidene-hydrazides （6a-d） as reactive intermediates. The chemical structures of all the synthesized compounds were elucidated by their IR, 1H NMR and 13C NMR and mass spectral data. Further, the target compounds were screened for their antimicrobial activity against various Gram-positive and Gram-negative bacteria.

Synthesis and anti-inflammatory activity of 2-substituted-((N,N-disubstituted)-1,3-benzoxazole)-5-carboxamides

A series of 2-substituted-((N,N-disubstituted)-1,3-benzoxazole)-5-carboxamides derivatives were synthesized by the reaction of 2-substituted-5-carbomethoxy benzoxazole with different secondary amines.The newly synthesized compounds were characterized on the basis of spectral(FT-IR,1H NMR,MS) & elemental analysis.All these compounds were screened for anti-inflammatory activity using carrageenan induced rat paw edema method.All of these compounds exhibited significant activity.Among the tested compounds Ve,Vg,Vf and Va were considered to have potent anti-inflammatory activity and was comparable with standard.

A Convenient Synthesis of 2-Oxazolines and 2-Benoxazoles with PPh3-DDQ as the Dehydrating Reagent

2-Oxazolines and 2-benoxazoles were synthesized in high yields from acylamino alcohols and acylaminophenols, respectively, with triphenylphosphine-2,3-dichloro-5,6-dicyanobenzoquinone （PPh3-DDQ） as the dehydrating and activating reagent. The synthesis was accomplished under neutral conditions.

Synthesis and photoconductivities of bisazo charge generation materials

Six bisazo compounds were synthesized by coupling 2-(49-aminophenyl)-6-aminobenzoxazole as diazo component with N-phenyl-N9-(2-hydroxy-3-naphthoyl)urea derivatives,and characterized by ultraviolet and visible spectroscopy(UV-Vis),Fourier transform infrared spectroscopy(FT-IR)and elemental analysis(EA).Using these bisazo compounds as charge generation materials and CT-191(2-methyl-4-(N,N-dibenzyl)aminobenzoaldehyde-1,1-diphenylhydrazone)as charge transportation material,organic photoconductive devices were prepared.The result from photoconductivity measurement of the devices shows that the bisazo compound from N-(2-methylphenyl)-N9-(2-hydroxy-3-naphthoyl)urea has the best xerographic performance,V_(0)=600 V,V_(R)=30 V,R_(d)=15 V·s^(-1),E_(1/2)=3.5 lx·s.