数学填空题：
（1）x的8次方÷x的4次方=（ ）. 5的10次方÷5?=（ ）；
（2）（- 2 ）的6次方÷（- 2 ）的5次方=（ ），（- y）的8次方÷（- y）?=（ ）；
（3）（x+y）的6次方÷（x+y）=（ ），（2a）的5次方÷（2a）?）=（ ）.
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计算：1.y/4x²-1/12y²+1/6xy 2.3/x-6/1-x-x+5/x²-x3.x/x-y×y²/x+y-x四次方y/x四次方-y四次方÷x²/x²+y²解方程：1.x-1/（x-2）+1=1/2-x2.x+1/x-1-4/x²-1=13.1/x+3-2/3-x=1/x²-9
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解方程：1.x-1/（x-2）+1=1/2-xX-1+(X-2)=-12X=2X=1经检验X=1是原方程的解.2.x+1/x-1-4/x²-1=1(X+1)^2-4=X^2-12X=2X=1X=1是增根,原方程无解.3.1/x+3-2/3-x=1/x²-9(X-3)+2(X+3)=13X=-2X=-2/3经检验是原方程的解.
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扫描下载二维码计算：2x（½x²－1）－3x（3分之1x²＋3分之2）
计算：2x（½x²－1）－3x（3分之1x²＋3分之2）
=x立方-2x-x立方-2x=-4x
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=x-2-x-三分之二=-3分之4
8 90分之4 2分之1 20
1.同时乘以4：X=-2X+3 2.同时乘以3:8X-6=2X+6 3.同时乘以2:2X=3X+32 4.同时乘以2：2-3X=6X+53X=3 6X=12 -X=32 -9X=3X=1 X=2 X=-32 X=-三分之一
=16/(x^16-1)
1/(x-1)-1/(x+1) -2/(x²+1)-4/(x的4次方+1)-8/(x的8次方+1)-16/(x的16次方+1)=(x+1)/(x ²- )-(x-1) /(x²-1) -2/(x²+1)-4/(x的4次方+1)-8/(x的8次方+1)-16/(x的16次方+1)=
2x(x2-2x-1/3)+4(x2+x/12) - x/3(3x2-6x-1)=2x3-4x2-2x/3+4x2+x/3-x3+2x2+x/3=x3+2x2 =x2(x+2) = (1-x)(x+2) = -(x-1)(x+2)= -(x2+x-2)= 1
x+2/5x=350.x+8/3=5/6.-1/3x=13/15.则7/5x=350,x=250.3*=5/6-8/3=-11/6,x=-11/18.1/3x=1-13/15=2/15,x=2/15*3=2/5
1/(x+1)-x/(x²-1)+3/x²-x²/(2x+1)+4x+3=1/(-2+1)+2/(2²-1)+3/2²-2²/(-4+1)-8+3=-13/4 再问： 不对，老师说答案是2 再答： 那题目1/(x+1)-x/(x²-1)+3/x&#1
(-1)的n+1次方乘以(n+1)分之nx的n次方 观察：可知分母是n+1,分子的系数是n,x的次方和第几项是一样的,而正负号则是正负交替,因此用(-1)的n+1次方就可以了,所以是(-1)的n+1次方乘以(n+1)分之nx的n次方
(x²-2x+1分之x²-1+x+1分之1-x)÷x-1分之x=[(x-1)(x+1)/(x-1)² -(x-1)/(x+1)]×(x-1)/x=[(x+1)/(x-1) -(x-1)/(x+1)]×(x-1)/x=[(x+1)²-(x-1)²]/(x-1)(x+1)×
1+45%X=14.50.45x=13.5x=304分之3x-12%=63x-0.48=243x=24.48x=8.163分之3x+4分之1x=6分之5x+x/4=5/65x=10/3x=2/37分之2*20%+7分之5*5分之1=2/7*0.2+1/7=(0.4+1)/7=1.4/7=0.2
7x=7分之5x=49分之55分之3x=8分之3x=8分之54分之1x=10分之9x=5分之18 再问： 写下计算过程，我就将你的回答采纳！ 再答： 7x=7分之5 x=（5/7）÷7 x=（5/7）×1/7 x=5/49 5分之3x=8分之3 x=3/8×(5/3) x=5/8 4分之1x=10分之9 x=9/10*
60分之8x+60分之10x=5分之210分之3x=5分之2x=5分之2×3分之10x=3分之46分之3x-6分之2x=10分之16分之1x=10分之1x=10分之1×6x=0.6很高兴为您解答,【学习宝典】团队为您答题.请点击下面的【选为满意回答】按钮,
5-5分之x+1=x 25-(x+1)=5x24=6xx=42分之1x-3=5分之1x 5x-30=2x3x=30x=103分之2x-1=6分之2x+1-1 2(2x-1)=2x+1-64x-2=2x-52x=-3x=-3/22分之x+1-1=3分之2-3x3(x+1)-6=2(2-3x)3x+3-6=4-6x9x=7
3分之2x+6分之1x=4分之1 5/6x=1/4x=1/4÷5/6x=3/10x-9分之7x=12分之5 2/9x=5/12x=5/12÷2/9x=15/8x+4分之3x=140 7/4x=140x=140÷7/4x=80 5分之3x+20=503/5x=30x=30÷3/5x=50 再问： 本人先去吃饭，稍等 再答
3分之1X+4分之3X=5分之26 4x/12+9x/12=26/5;13x/12=26/5;x=24/5;X÷7分之3=10×5分之27x/3=4;x=12/7;3、递等式计算.8分之7-（16分之5-4分之1）÷27分之26 =7/8-(5/16-4/16)×(27/26)=7/8-27/16×26=(52×7-2
3-4x=2-x-3x=-1x=三分之一0.2X+1=-1.8X2X=-1X=-0.53分之1x=9-3分之2x 3分之1x+3分之2x =9X=9
1）2分之3x+2y=12y=1-3/2xy=1/2-3/4x2)4分之1x+4分之7y=2x+7y=87y=8-xy=8/7-1/7x3）5x-3y=x+2y2y+3y=5x-x5y=4xy=4/5x4) 2(3y-3）=6x+46(y-1)=6x+4y-1=x+2/3y=x+2/3+1y=x+5/3如果本题有什么不
1.两边加上1/3x得1/2x+1/3x=1-1/3x+1/3x5/6x=1两边乘以6/5得5/6x*6/5=1*6/5x=6/52.两边减去2x得 5x+2=0 减去2得 5x=-2 除以 5得 x=-2/53.原式=2x²+3ax-2x-1+6ax-6=2x²+9ax-2x-7当x=-1 a=1
1-3分之4-5X=4分之2X+1-2(2-X) :1-4/3-5x=2/4 x+1-2(2-x)-1/3-5x=1/2 x+1-4+2x两边同时乘以6可得：-2-30x=3x+6-24+12x-2-6+24=3x+12x+30x16=45xx=16/455分之2X-3-6分之3X-1=3分之1X :2/5x-3-3/404网页出错信息提示_查字典
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Journal of ChemistryVolume ), Article ID
pagesResearch Article
-Promoted Solvent-Free Synthesis of Benzoxazoles, Benzimidazoles, and Benzothiazole Derivatives,1 ,2 and 11Research and Development Division, RA Chem Pharma Limited, Prasanth Nagar, Hyderabad 500072,
India2Department of Chemistry, Acharya Nagarjuna University, Nagarjuna Nagar, Guntur 522510,
IndiaReceived 10 June 2012; Revised 17 August 2012; Accepted 21 August 2012Academic Editor: Antonio Romerosa Copyright (C) 2013 K. Ravi Kumar et al. This is an open access article distributed under the , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.An efficient protocol has been developed for the preparation of a library of benzoxazole, benzimidazole, and benzothiazole derivatives from reactions of acyl chlorides with o-substituted aminoaromatics in the presence of catalytic amount of silica-supported sodium hydrogen sulphate under solvent-free conditions. Simple workup procedure, high yield, easy availability, reusability, and use of ecofriendly catalyst are some of the striking features of the present protocol.1. IntroductionMolecules with benzoxazole, benzimidazole, and benzothiazoles moieties are attractive targets for synthesis since they often exhibit diverse and important biological properties. These heterocycles have shown different pharmacological activities such as antibiotic [], antifungal [], antiviral [], anticancer [], antimicrobial [], and anti-Parkinson [] properties. They have also been used as ligands for asymmetric transformations []. Benzimidazole derivatives are a unique and broad spectrum class of antirhino/enteroviral agents such as antiulcerative [] and antiallergic []; they are effective against the human cytomegalovirus [] and are also efficient selective neuropeptide Y Y1 receptor antagonists []. A number of methods are reported for the synthesis of these heterocycles by using different catalysts such as Pd-catalyzed oxidative cyclization [], ionic liquid-mediated synthesis [], base-assisted reaction of 1,1-dibromoethanes [], SiO2-ZnCl2 [], ZrOCl2·8H2O [], In(OTf)3 [], polyethylene-glycol-mediated catalysts [], and different heteropolyacid catalysts [], which include condensation of orthoesters [–], nitriles [], aldehydes [–], carboxylic acids [–], acid chlorides [], amides [] and esters [] with o-substituted aminoaromatics in the presence of different acids and catalysts. Beckmann rearrangement of o-acylphenol oximes [], photocyclization of phenolic Schiff bases [], and benzimidazole, synthesis in solvent-free conditions [] were also used. More recently benzoxazole, benzimidazole, and benzothiozoles were prepared from condensation of aldehydes with o-substituted aminoaromatics in the presence of Indion 190 resin []. However, many of these methods suffer from one or more of the drawbacks such as requirement of strong acidic conditions, long reaction times, low yields, tedious workup procedures, requirement of excess amounts of reagents, and use of toxic reagents, catalysts or solvents. Therefore, there is a strong demand for a highly efficient and environmentally benign method for the synthesis of these heterocycles.In recent years, heterogeneous catalysts [–] have gained importance in several organic transformations due to their interesting reactivity as well as for economic and environmental reasons. In continuation of our work to develop new methodologies for organic transformations [–], we observed that silica-supported sodium hydrogen sulphate is highly efficient catalyst for the synthesis of substituted benzoxazole, benzimidazole, and benzothiazole derivatives through the reaction of o-substitued aminoaromatics with different acyl chlorides under solvent-free conditions. The catalyst NaHSO4-SiO2 can easily be prepared [] from the readily available NaHSO4 and silica gel (230&#x mesh) and these are inexpensive and nontoxic. Besides, as the reaction is heterogeneous in nature, the catalyst can easily be removed by simple filtration (Scheme ).Scheme 12. Results and DiscussionsIn order to find the optimum reaction conditions for the condensation reaction, preliminary efforts were mainly focused on the evaluation of different solvents. The model reaction has been carried out between o-phenylenediamine and benzoyl chloride in the presence of NaHSO4-SiO2 catalyst under different solvents and at different temperatures, and results are shown in Table .Table 1: Preparation of 2-phenyl benzimidazole using various solvents and temperauresa.The effect of solvent, reaction temperature, and time on the reaction was systematically investigated, and the results were summarized in Table . The optimized reaction conditions for the reaction were found to be NaHSO4-SiO2 under solvent-free condition for 12 hr at the temperature of 100°C. Thus, we used NaHSO4-SiO2 as a catalyst in the present work. In order to elucidate the role of NaHSO4-SiO2 as catalyst, a controlled reaction was conducted using o-phenylenediamine and benzoyl chloride under solvent-free condition in the absence of catalyst. This resulted in the formation of only 7% of the fused product after 12 hr at 100°C. However, reaction with same substrate using 25%/wt of NaHSO4-SiO2 at 100°C for 12 hr afforded the product in quantitative yield. Lower temperatures required more time for the completion of the reaction and obtained low yields compared to the optimized reaction condition.As shown in Table , different acyl chlorides reacted with different o-substituted aminoaromatics without any significant difference in the reaction time to give the corresponding 2-substituted benzoxazole, benzimidazole, and benzothiazole derivatives in good yield. The method has the ability to tolerate other functional groups such as methoxy, methyl, and halides. The products were synthesized in good to excellent yields and characterized by 1H NMR, LCMS, and physical constant. Physical and spectral data of known compounds are in agreement with those reported in literature [–].Table 2: Synthesis of 2-substituted benzoxazoles, benzimidazoles, and benzothiazolesa.The reusability of catalyst is important for the large-scale operation and industrial point of view. Therefore, the recovery and reusability of NaHSO4-SiO2 was examined. The catalyst was separated and reused after washing with EtOAc and drying at 100°C. The reusability of catalyst was investigated in the reaction of o-phenylenediamine with benzoyl chloride (Figure ). The results illustrated in Figure
showed that the catalyst can be used four times with consistent yield.3. ConclusionIn conclusion, NaHSO4-SiO2 was found to be an efficient catalyst for the formation of benzoxazole, benzimidazole, and benzothiazole derivatives. The use of this inexpensive, easily available, and reusable catalyst makes this protocol practical, environment friendly, and economically attractive. The simple workup procedure, high yields of products, and nontoxic nature of the catalyst are other advantages of the present method.4. Experimental SectionAll 1H NMR spectra were recorded on 400 MHz Varian FT-NMR spectrometers. All chemical shifts are given as
value with reference to Tetra methyl silane (TMS) as an internal standard. Melting points were taken in open capillaries. The IR spectra were recorded on a PerkinElmer 257 spectrometer using KBr discs. Products were purified by flash chromatography on 100&#x mesh silica gel. The chemicals and solvents were purchased from commercial suppliers either from Aldrich, Spectrochem, and they were used without purification prior to use.5. FT-IR Spectrum of NaHSO
The FT-IR spectrum of the catalyst is shown in Figure . The catalyst is solid, and its solid-state IR spectrum was recorded using the KBr-disc technique. For silica (SiO2), the major peaks are broad antisymmetric Si-O-Si stretching from 1000&#x cm−1 and symmetric Si-O-Si stretching near 798 cm−1, and bending modes of Si-O-Si lie around 467 cm−1. The spectrum also shows a broad Si-OH stretching absorption from 3300 to 3500 cm−1.Figure 1: FT-IR spectra of silica-supported sodium hydrogen sulphate.6. X-Ray Diffraction (XRD) Spectrum of NaHSO
Powder X-ray diffraction measurement was performed using D8 advance diffractometer. The strongest peaks of XRD pattern correspond to the SiO2 plane with the other peaks indexed as the [, , ] planes of supported sodium hydrogen sulphate (Figure ).Figure 2: XRD spectra of silica-supported sodium hydrogen sulphate.Figure 3: Investigation of reusability of NaHSO4-SiO2.7. General Experimental ProcedureA mixture of 2-amino phenols or o-phenylenediamines (1 mmol) and acyl chloride (1 mmol) were place in a sealed vessel containing NaHSO4-SiO2 (25%/wt) the reaction mixture was stirred at 100°C for 12 hrs. The progress of the reaction was monitored by TLC Hexane: EtOAc (4 : 1) after completion of the reaction, the reaction mixture was cooled and treated by dilution with EtOAc and the catalyst was removed by filtration. Obtained filtrate was evaporated under reduced pressure to get the crude product, which was purified by column chromatography to give 2-substituted benzoxazoles, benzimidazole, and benzothioazole derivatives.8. Representative Spectral Data2-Phenyl-1H-benzo [d]Imidazole (Table , Entry 1).1H NMR (DMSO-d6):
13.02 (br s, 1H), 8.20 (d, J = 7.6 Hz, 2H), 7.67&#x (m, 1H), 7.56&#x (m, 4H), 7.22&#x (m, 2H); (LC-MS)
: 195.08 [M + H]+; IR (KBr, cm−1): , , , , 738. Anal. Calcd. For C13H10N2: C, 80.39; H, 5.19; N, 14.42. Found: C, 80.11; H, 5.01; N, 14.38.2-Heptyl-1H-benzo [d]Imidazole (Table , Entry 9). 1H NMR (DMSO-d6): δ12.11 (br s, 1H), 7.49 (d, J = 8 Hz, 1H), 7.38 (d, J = 6.4 Hz, 1H), 7.09&#x (m, 2H), 2.78 (t, J = 7.6 Hz, 2H), 1.77&#x (m, 2H), 1.31&#x (m, 8H), 0.85 (t, J = 6.4 Hz, 3H); (LC-MS)
: 217.21 [M+H]+; IR (KBr, cm−1): , , , . Anal. Calcd. For C14H20N2: C, 77.73; H, 9.32; N, 12.95. Found: C, 77.70; H, 9.28; N, 12.86.2-Heptyl-5-methyl-1H-Benzo [d]Imidazole (Table , Entry 10).1H NMR (DMSO-d6): δ11.98 (br s, 1H), 7.36&#x (m, 2H), 6.93-6.89 (m, 1H), 2.74 (t, J = 7.6 Hz, 2H), 2.37 (s, 3H), 1.78&#x (m, 2H), 1.30&#x (m, 8H), 0.85 (t, J = 6.4 Hz, 3H); (LC-MS)
: 231.18 [M+H]+; IR (KBr, cm−1): , , , 803. Anal. Calcd. For C15H22N2: C, 78.21; H, 9.63; N, 12.16. Found: C, 78.19; H, 9.58; N, 12.15.2-Phenyl Benzo [d]Oxazole (Table , Entry 11).1H NMR (CDCl3): δ 8.27&#x (m, 2H), 7.79&#x (m, 1H), 7.60&#x (m, 1H), 7.54&#x (m, 3H), 7.38&#x (m, 2H); (LC-MS)
: 196.20 [M+H]+; IR (KBr, cm−1): , , . Anal. Calcd. For C13H9NO: C, 79.98; H, 4.65; N, 7.17. Found: C, 79.86; H, 4.61; N, 7.14; O.2-Phenyl Benzo [d]Thiazole (Table , Entry 24).1H NMR (CDCl3): δ8.11&#x (m, 3H), 7.91 (d, J = 8.4 Hz, 1H), 7.51-7.40 (m, 4H), 7.39-7.37 (m, 1H); (LC-MS)
: 212.12 [M+H]+; IR (KBr, cm−1): , , , 961, 766, 685. Anal. Calcd. For C13H9NS: C, 73.90; H, 4.29; N, 6.63. Found: C, 73.87; H, 4.27; N, 6.59.AcknowledgmentsWe sincerely thank the RA chem. Pharma Ltd for financial support and encouragement. Support from the analytical department is also acknowledged.References
D. A. Evans, C. E. Sacks, W. A. Kleschick, and T. R. Taber, “Polyether antibiotics synthesis. Total synthesis and absolute configuration of the ionophore A-23187,” Journal of the American Chemical Society, vol. 101, no. 22, pp. , 1979.
· M. Yamato, “Study on the development of biological-active compounds after the model of natural products,” Journal of the Pharmaceutical Society of Japan, vol. 112, no. 2, pp. 81–99, 1992. X. Song, B. S. Vig, P. L. Lorenzi, J. C. Drach, L. B. Townsend, and G. L. Amidon, “Amino acid ester prodrugs of the antiviral agent 2-bromo-5,6-dichloro-1- (β-D-ribofuranosyl)benzimidazole as potential substrates of hPEPT1 transporter,” Journal of Medicinal Chemistry, vol. 48, no. 4, pp. , 2005.
· D. Kumar, M. R. Jacob, M. B. Reynolds, and S. M. Kerwin, “Synthesis and evaluation of anticancer benzoxazoles and benzimidazoles related to UK-1,” Bioorganic and Medicinal Chemistry, vol. 10, no. 12, pp. , 2002.
· I. Yildiz-Oren, I. Yalcin, E. Aki-Sener, and N. Ucarturk, “Synthesis and structure-activity relationships of new antimicrobial active multisubstituted benzazole derivatives,” European Journal of Medicinal Chemistry, vol. 39, no. 3, pp. 291–298, 2004.
· A. Benazzouz, T. Boraud, P. Dubedat, A. Boireau, J.-M. Stutzmann, and C. Gross, “Riluzole prevents MPTP-induced parkinsonism in the rhesus monkey: a pilot study,” European Journal of Pharmacology, vol. 284, no. 3, pp. 299–307, 1995.
· A. Figge, H. J. Altenbach, D. J. Brauer, and P. Tielmann, “Synthesis and resolution of 2-(2-diphenylphosphinyl-naphthalen-1-yl)-1-isopropyl-1H- a new atropisomeric P,N-chelating ligand for asymmetric catalysis,” Tetrahedron Asymmetry, vol. 13, no. 2, pp. 137–144, 2002.
· L. J. Scott, C. J. Dunn, G. Mallarkey, and M. Sharpe, “Esomeprazole: a review of its use in the management of acid-related disorders,” Drugs, vol. 62, no. 10, pp. , 2002.
· H. Nakano, T. Inoue, N. Kawasaki et al., “Synthesis and biological activities of novel antiallergic agents with 5- lipoxygenase inhibiting action,” Bioorganic and Medicinal Chemistry, vol. 8, no. 2, pp. 373–380, 2000.
· Z. Zhu, B. Lippa, J. C. Drach, and L. B. Townsend, “Design, synthesis, and biological evaluation of tricyclic nucleosides (dimensional probes) as analogues of certain antiviral polyhalogenated benzimidazole ribonucleosides,” Journal of Medicinal Chemistry, vol. 43, no. 12, pp. , 2000.
· H. Zarrinmayeh, A. M. Nunes, P. L. Ornstein et al., “Synthesis and evaluation of a series of novel 2-[(4- chlorophenoxy)methyl]benzimidazoles as selective neuropeptide Y Y1 receptor antagonists,” Journal of Medicinal Chemistry, vol. 41, no. 15, pp. , 1998.
· W. H. Chen and Y. Pang, “Efficient synthesis of 2-(2′-hydroxyphenyl)benzoxazole by palladium(II)-catalyzed oxidative cyclization,” Tetrahedron Letters, vol. 50, no. 48, pp. , 2009.
· A. K. Yadav, M. Kumar, T. Yadav, and R. Jain, “An ionic liquid mediated one-pot synthesis of substituted thiazolidinones and benzimidazoles,” Tetrahedron Letters, vol. 50, no. 35, pp. , 2009.
· W. Shen, T. Kohn, Z. Fu, X. Jiao, S. Lai, and M. Schmitt, “Synthesis of benzimidazoles from 1,1-dibromoethenes,” Tetrahedron Letters, vol. 49, no. 51, pp. , 2008.
· R. G. Jacob, L. G. Dutra, C. S. Radatz, S. R. Mendes, G. Perin, and E. J. Lenardão, “Synthesis of 1,2-disubstitued benzimidazoles using SiO2/ZnCl2,” Tetrahedron Letters, vol. 50, no. 13, pp. , 2009.
· I. Mohammadpoor-Baltork, A. R. Khosropour, and S. F. Hojati, “ZrOCl2·8H2O as an efficient, environmentally friendly and reusable catalyst for synthesis of benzoxazoles, benzothiazoles, benzimidazoles and oxazolo[4,5-b]pyridines under solvent-free conditions,” Catalysis Communications, vol. 8, no. 12, pp. , 2007.
· R. Trivedi, S. K. De, and R. A. Gibbs, “A convenient one-pot synthesis of 2-substituted benzimidazoles,” Journal of Molecular Catalysis A, vol. 245, no. 1-2, pp. 8–11, 2006.
· C. Mukhopadhyay and P. K. Tapaswi, “PEG-mediated catalyst-free expeditious synthesis of 2-substituted benzimidazoles and bis-benzimidazoles under solvent-less conditions,” Tetrahedron Letters, vol. 49, no. 43, pp. , 2008.
· M. M. Heravi, S. Sadjadi, H. A. Oskooie, R. H. Shoar, and F. F. Bamoharram, “Heteropolyacids as heterogeneous and recyclable catalysts for the synthesis of benzimidazoles,” Catalysis Communications, vol. 9, no. 4, pp. 504–507, 2008.
· D. Villemin, M. Hammadi, and B. Martin, “Clay catalysis: condensation of orthoesters with O-substituted aminoaromatics into heterocycles,” Synthetic Communications, vol. 26, no. 15, pp. , 1996.
· M. Doise, F. Dennin, D. Blondeau, and H. Sliwa, “Synthesis of novel heterocycles: oxazolo[4,5-b]pyridines and oxazolo[4,5-d]pyrimidines,” Tetrahedron Letters, vol. 31, no. 8, pp. , 1990.
· G. L. Jenkins, A. M. Knevel, and C. S. Davis, “A new synthesis of the benzothiazole and benzoxazole rings,” Journal of Organic Chemistry, vol. 26, no. 1, p. 274, 1961.
· D. W. Hein, R. J. Alheim, and J. J. Leavitt, “The use of polyphosphoric acid in the synthesis of 2-aryl- and 2-alkyl-substituted benzimidazoles, benzoxazoles and benzothiazoles,” Journal of the American Chemical Society, vol. 79, no. 2, pp. 427–429, 1957.
· P. Salehi, M. Dabiri, M. A. Zolfigol, S. Otokesh, and M. Baghbanzadeh, “Selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles in water at ambient temperature,” Tetrahedron Letters, vol. 47, no. 15, pp. , 2006.
· N. Parikh, D. Kumar, S. R. Roy, and A. K. Chakraborti, “Surfactant mediated oxygen reuptake in water for green aerobic oxidation: mass-spectrometric determination of discrete intermediates to correlate oxygen uptake with oxidation efficiency,” Chemical Communications, vol. 47, no. 6, pp. , 2011.
· A. K. Chakraborti, S. Rudrawar, K. B. Jadhav, G. Kaur, and S. V. Chankeshwara, “‘on water’ organic synthesis: a highly efficient and clean synthesis of 2-aryl/heteroaryl/styryl benzothiazoles and 2-alkyl/aryl alkyl benzothiazolines,” Green Chemistry, vol. 9, no. 12, pp. , 2007.
· B. Sadeghi and M. G. Nejad, “Silica sulfuric acid: an eco-friendly and reusable catalyst for synthesis of benzimidazole derivatives,” Journal of Chemistry, vol. 2013, Article ID
pages, 2013.
· Y. H. So and J. P. Heeschen, “Mechanism of polyphosphoric acid and phosphorus pentoxide-methanesulfonic acid as synthetic reagents for benzoxazole formation,” Journal of Organic Chemistry, vol. 62, no. 11, pp. , 1997.
· S. Rudrawar, A. Kondaskar, and A. K. Chakraborti, “An efficient acid- and metal-free one-pot synthesis of benzothiazoles from carboxylic acids,” Synthesis, no. 15, Article ID Z05105SS, pp. , 2005.
· A. K. Chakraborti, C. Selvam, G. Kaur, and S. Bhagat, “An efficient synthesis of benzothiazoles by direct condensation of carboxylic acids with 2-aminothiophenol under microwave irradiation,” Synlett, no. 5, pp. 851–855, 2004.
· R. Kumar, C. Selvam, G. Kaur, and A. K. Chakraborti, “Microwave-assisted direct synthesis of 2-substituted benzoxazoles from carboxylic acids under catalyst and solvent-free conditions,” Synlett, no. 9, pp. , 2005.
· D. Kumar, S. Rudrawar, and A. K. Chakraborti, “One-pot synthesis of 2-substituted benzoxazoles directly from carboxylic acids,” Australian Journal of Chemistry, vol. 61, no. 11, pp. 881–887, 2008.
· R. N. Nadaf, S. A. Siddiqui, T. Daniel, R. J. Lahoti, and K. V. Srinivasan, “Room temperature ionic liquid promoted regioselective synthesis of 2-aryl benzimidazoles, benzoxazoles and benzthiazoles under ambient conditions,” Journal of Molecular Catalysis A, vol. 214, no. 1, pp. 155–160, 2004.
· M. Terashima and M. A. Ishii, “A facile synthesis of 2-substituted benzoxazoles,” Synthesis, vol. 1982, pp. 484–485, 1982. A. K. Chakraborti, S. Rudrawar, G. Kaur, and L. Sharma, “An efficient conversion of phenolic esters to benzothiazoles under mild and virtually neutral conditions,” Synlett, no. 9, pp. , 2004.
· B. M. Bhawal, S. P. Mayabhate, A. P. Likhite, and A. R. A. S. Deshmukh, “Use of zeolite catalysts for efficient synthesis of benzoxazoles via Beckmann rearrangement,” Synthetic Communications, vol. 25, no. 21, pp. , 1995.
· Y. Chen and D. X. Zeng, “Study on photochromic diarylethene with phenolic schiff base: preparation and photochromism of diarylethene with benzoxazole,” Journal of Organic Chemistry, vol. 69, no. 15, pp. , 2004.
· H. Thakuria and G. Das, “An expeditious one-pot solvent-free synthesis of benzimidazole derivatives,” Arkivoc, vol. 2008, no. 15, pp. 321–328, 2008.
· V. S. Padalkar, V. D. Gupta, K. R. Phatangare, V. S. Patil, P. G. Umape, and N. Sekar, “Indion 190 resin: efficient, environmentally friendly, and reusable catalyst for synthesis of benzimidazoles, benzoxazoles, and benzothiazoles,” Green Chemistry Letters and Reviews, vol. 5, no. 2, pp. 139–145, 2012.
· R. G. Jacob, C. S. Radatz, M. B. Rodrigues et al., “Synthesis of 1-H-1,5-benzodiazepines derivatives using SiO2/ZnCl2,” Heteroatom Chemistry, vol. 22, no. 2, pp. 180–185, 2011.
· R. G. Lara, E. L. Borges, E. J. Lenardao, D. Alves, R. G. Jacob, and G. Perin, “Addition of thiols to phenylselenoalkynes using KF/Alumina under solvent-free conditions,” Journal of the Brazilian Chemical Society, vol. 21, pp. , 2010. R. G. Jacob, M. S. Silva, S. R. Mendes, E. L. Borges, E. J. Lenardao, and G. Perin, “Atom-economic synthesis of functionalized octahydroacridines from citronellal or 3-(phenylthio)-citronellal,” Synthetic Communications, vol. 39, no. 15, pp. , 2009.
· K. R. Kumar, P. V. V. Satyanarayana, and B. S. Reddy, “Simple and efficient method for deprotection of tetrahydropyranyl ethers by using Silica supported sodium hydrogen sulphate,” Chinese Journal of Chemistry, vol. 30, no. 5, pp. , 2012.
· K. Ravi Kumar, P. V. V. Satyanarayana, and B. Srinivasa Reddy, “Simple and efficient method for tetrahydropyranylation of alcohols and phenols by using silica supported sodium hydrogen sulphate as a catalyst,” Asian Journal of Chemistry, vol. 24, no. 9, pp. , 2012.
· R. K. Kumar, P. V. V. Satyanarayana, and S. B. Reddy, “NaHSO4-SiO2 promoted synthesis of Benzimidazole derivatives,” Archives of Applied Science Research, vol. 4, no. 3, pp. , 2012. K. R. Kumar, P. V. V. Satyanarayana, and B. Srinivasa Reddy, “Direct and practical synthesis of 2-arylbenzoxazoles promoted by silica supported sodium hydrogen sulphate,” Der Pharma Chemica, vol. 4, no. 2, pp. 761–766, 2012.
· G. W. Breton, “Selective monoacetylation of unsymmetrical diols catalyzed by silica gel-supported sodium hydrogen sulf,” Journal of Organic Chemistry, vol. 62, p. . A. J. Blacker, M. M. Farah, M. I. Hall, S. P. Marsden, O. Saidi, and J. M. J. Williams, “Synthesis of benzazoles by hydrogen-transfer catalysis,” Organic Letters, vol. 11, no. 9, pp. , 2009.
· S. B. Sapkal, K. F. Shelke, S. S. Sonar, B. B. Shingate, and M. S. Shingare, “Acidic ionic liquid catalyzed environmentally friendly synthesis of benzimidazole derivatives,” Bulletin of the Catalysis Society of India, pp. 78–83, 2009. J. Peng, M. Ye, C. Zong et al., “Copper-catalyzed intramolecular C-N bond formation: a straightforward synthesis of benzimidazole derivatives in water,” Journal of Organic Chemistry, vol. 76, no. 2, pp. 716–719, 2011.
· C. S. Cho, D. T. Kim, J. Q. Zhang, S. L. Ho, T. J. Kim, and S. C. Shim, “Tin(II) chloride-mediated synthesis of 2-substituted benzoxazoles,” Journal of Heterocyclic Chemistry, vol. 39, no. 2, pp. 421–423, 2002.
· M. M. Guru, M. A. Ali, and T. Punniyamurthy, “Copper-mediated synthesis of substituted 2-aryl-N-benzylbenzimidazoles and 2-arylbenzoxazoles via C-H functionalization/C-N/C-O bond formation,” Journal of Organic Chemistry, vol. 76, no. 13, pp. , 2011.
· J. Bonnamour and C. Bolm, “Iron-catalyzed intramolecular O-arylation: synthesis of 2-aryl benzoxazoles,” Organic Letters, vol. 10, no. 13, pp. , 2008.
· B. Wang, Y. Zhang, P. Li, and L. Wang, “An Efficient and practical synthesis of benzoxazoles from acyl chlorides and 2-aminophenols catalyzed by Lewis acid in(OTf)3 under solvent-free reaction conditions,” Chinese Journal of Chemistry, vol. 28, no. 9, pp. , 2010.
· M. Zhang, S. Zhang, M. Liu, and J. Cheng, “Palladium-catalyzed desulfitative C-arylation of a benzo[d]oxazole C-H bond with arene sulfonyl chlorides,” Chemical Communications, vol. 47, no. 41, pp. 1, 2011.
· H.-J. Lim, D. Myung, I. Y. C. Lee, and H. J. Myung, “Microwave-assisted synthesis of benzimidazoles, benzoxazoles, and benzothiazoles from resin-bound esters,” Journal of Combinatorial Chemistry, vol. 10, no. 4, pp. 501–503, 2008.
· C. Praveen, A. Nandakumar, P. Dheenkumar, D. Muralidharan, and P. T. Perumal, “Microwave-assisted one-pot synthesis of benzothiazole and benzoxazole libraries as analgesic agents,” Journal of Chemical Sciences, vol. 124, no. 3, pp. 609–624, 2012.