- Hemoglobin: A New Biocatalyst for the Synthesis of 2-substituted Benzoxazoles via Oxidative Cyclization
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Efficient and mild synthesis of a series of 2-substituted benzoxazoles via oxidative cyclization catalyzed by hemoglobins reported here for the first time. Satisfactory yields (84 %–97 %) and mild reaction conditions make this method highly viable for practical applications.
- Li, Fengxi,Li, Zhengqiang,Tang, Xuyong,Cao, Xinyu,Wang, Chunyu,Li, Jialin,Wang, Lei
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p. 1192 - 1195
(2019/02/07)
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- Effect of substituents on the UV spectra of supermolecular system: Silver nanoparticles with bi-aryl Schiff bases containing hydroxyl
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Effect of substituents on the ultraviolet (UV) spectra of supermolecular system involving silver nanoparticles (AgNPs) and Schiff bases was investigated. AgNPs and 49 samples of model compounds (MC), bi-aryl Schiff bases containing hydroxyl (XBAY, involving 4-OHArCH?NArY, 2-OHArCH?NArY, XArCH?NAr-4′-OH, and XArCH?NAr-2′-OH), were synthesized. The size of AgNPs was characterized by transmission electron microscopy (TEM), and the UV absorption spectra of AgNPs, XBAYs, and MC-AgNPs mixed solutions were measured, respectively. The results show that (1) the size of AgNPs is larger in MC-AgNPs solutions than that in AgNPs solution due to the distribution of MC molecules on the surface of AgNPs; (2) the UV absorption wavelength of XBAYs changes in the action of AgNPs and their wavelength shift exists limitation between XBAY and MC-AgNPs solutions; and (3) the wavelength shift limit of MC-AgNPs (λWSL) is influenced by the substituents X and Y and the position of hydroxyl OH. The wavenumber ΔνWSL of λWSL can be quantified by employing the excited-state substituent constant σexCC and Hammett constant σ of substituents X and Y. Comparing with the 4-OH, the 4′-OH makes the ΔνWSL a red shift, whereas the 2′-OH, comparing with the 2-OH, makes the ΔνWSL a blue shift.
- Cao, Chao-Tun,Cheng, Shimao,Zhang, Jingyuan,Cao, Chenzhong
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- Enantioselective Strecker and Allylation Reactions with Aldimines Catalyzed by Chiral Oxazaborolidinium Ions
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Chiral oxazaborolidinium ion (COBI)-catalyzed enantioselective nucleophilic addition reactions of aldimines using tributyltin cyanide and allyltributylstannane have been developed. Various α-aminonitriles and homoallylic amines were synthesized in high yi
- Kang, Ki-Tae,Park, Sang Hyun,Ryu, Do Hyun
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supporting information
p. 6679 - 6683
(2019/09/12)
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- Synthesis, theoretical investigations, biocidal screening, DNA binding, in vitro cytotoxicity and molecular docking of novel Cu (II), Pd (II) and Ag (I) complexes of chlorobenzylidene Schiff base: Promising antibiotic and anticancer agents
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Three new Cu (II), Pd (II) and Ag (I) complexes of bidentate Schiff base ligand 2-[(4-chlorobenzylidene)amino] phenol (HL) were synthesized. The stoichiometric ratios and physicochemical properties of these complexes were determined using elemental analys
- Abdel-Rahman, Laila H.,Adam, Mohamed Shaker S.,Abu-Dief, Ahmed M.,Moustafa,Basha, Maram T.,Aboraia, Ahmed S.,Al-Farhan, Badriah Saad,Ahmed, Hanan El-Sayed
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- Oxidative NHC Catalysis for the Generation of Imidoyl Azoliums: Synthesis of Benzoxazoles
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N-Heterocyclic carbene (NHC)-catalyzed intramolecular cyclization of aldimines generated from 2-amino phenols and aromatic aldehydes leading to the synthesis of 2-arylbenzoxazoles under mild conditions is presented. The reaction proceeds via the generation of the aza-Breslow intermediates from imines and NHC, which under oxidative conditions form the key imidoyl azoliums and a subsequent intramolecular cyclization furnishes the product. The reaction tolerates a broad range of functional groups, and the products are formed in generally good yields.
- Patra, Atanu,James, Anjima,Das, Tamal Kanti,Biju, Akkattu T.
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p. 14820 - 14826
(2019/01/03)
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- Unexpected Decarboxylation-Triggered o-Hydroxyl-Controlled Redox Condensation of Phenylglycines with 2-Nitrophenols in Aqueous Media
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A decarboxylation-triggered and o-hydroxyl-controlled hydrogen-transfer strategy for the one-pot synthesis of benzoxazoles from readily available amino acids and 2-nitrophenols is reported. On the basis of this autoredox reaction, the C?N bond can be efficiently constructed to afford the desired products in moderate to good yields under transition-metal-free conditions in aqueous media. (Figure presented.).
- Tang, Lin,Yang, Zhen,Sun, Tian,Zhang, Di,Ma, Xiantao,Rao, Weihao,Zhou, Yuqiang
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supporting information
p. 3055 - 3062
(2018/08/01)
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- Catalyst-free allylation of 2-aminophenol–derived aldimines with allyltrichlorosilane under thermal conditions
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Allylation of 2-aminophenol-derived aldimines using allyltrichlorosilane under catalyst free conditions has been developed. This reaction afforded the corresponding homoallylic amines in good to excellent yields (68–94%). The salicylaldehyde-derived aldimines as well as benzoylhydrazone also found to react with allyltrichlorosilane smoothly under the same conditions, to furnish the corresponding homoallylic amine derivatives. This study suggests that the phenolic –OH group acts as an anchoring group for the transfer of allyl group from allyl silane reagent.
- Venkatanna, Kesa,Ramanathan, Chinnasamy Ramaraj
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supporting information
p. 3650 - 3653
(2017/08/22)
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- Abnormal effect of hydroxyl on the longest wavelength maximum in ultraviolet absorption spectra for bis-aryl Schiff bases
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Two sets of bis-aryl Schiff bases that contain 4(or 4′)-OH and 2(or 2′)-OH were synthesized. The first set consists of 4-HOArCH=NArY and XArCH=NArOH-4′, and the second set consists of 2-HOArCH=NArY and XArCH=NArOH-2′. Their ultraviolet absorption spectra were measured and investigated. A very interesting phenomenon was observed by analyzing their wave number νmax (cm?1) of longest wavelength maximum λmax (nm) of ultraviolet. Compared with the change regularity of the νmax of XArCH=NArY (where the X and Y excluded OH), the 4′-position hydroxyl (4′-OH) and 2′-position hydroxyl (2′-OH) have abnormal performance. The details are the following: the 4′-OH contributes an additional red shift to the νmax of XArCH=NArOH-4′ (λmax increase), whereas the 2′-OH contributes an additional blue shift to the νmax of XArCH=NArOH-2′ (λmax decrease). In addition, there are ortho steric effects of all 2-OH and 2′-OH on the νmax for 2-HOArCH=NArY and XArCH=NArOH-2′, and the ortho steric effect contributes a red shift to their νmax. These experimental facts can provide an important theoretical reference for us using aryl Schiff base compounds as optical materials and performing the molecular design.
- Cao, Chao-Tun,Zhou, Wei,Cao, Chenzhong
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- OMS-2/H2O2/Dimethyl Carbonate: An Environmentally-Friendly Heterogeneous Catalytic System for the Oxidative Synthesis of Benzoxazoles at Room Temperature
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A manganese octahedral molecular sieve (OMS-2) was found to be an efficient and recyclable heterogeneous catalyst for the oxidative synthesis of benzoxazoles in the gram-scale from phenolic imines at room temperature. H2O2 and biobased reagent dimethyl carbonate (DMC) were successfully employed as the environmentally friendly oxidant and solvent, respectively, in an OMS-2-catalysted redox reaction for the first time. Benzoxazoles could also be obtained from N-substituted 2-aminophenols via Cu(OH)x/OMS-2-catalyzed sequential oxidative transformation at elevated temperatures.
- Meng, Xu,Wang, Yuanguang,Chen, Baohua,Chen, Gexin,Jing, Zhenqiang,Zhao, Peiqing
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supporting information
p. 2018 - 2024
(2017/12/26)
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- Synthesis and biological activities of 2-aminophenol-based Schiff bases and their structure-activity relationship
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Six Schiff bases 8-13 were synthesized by condensation of 2-aminophenol (1) with various chloro- and nitro-benzaldehydes (2-7), characterized, and evaluated for antioxidant, antibacterial, lipoxygenase, and urease inhibitory potentials. All Schiff bases e
- Aslam, Muhammad,Anis, Itrat,Mehmood, Rashad,Iqbal, Lubna,Iqbal, Samina,Khan, Inamullah,Chishti, Muhammad Salman,Perveen, Shagufta
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p. 109 - 115
(2016/01/25)
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- Synthesis of 4-imino-2H,3H,5H-[1,2,5]thiadiazolidin-1-oxide through cycloaddition reaction of N-sulphinylanilines and N-(α-cyano-α-aryl) -methylanilines
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Through the normal mode of cycloaddition reaction of N-(α-cyano- α-aryl)-methylanilines (II) onto N-sulphinylanilines (III) has provided 2,3,5-triaryl-4-imino-2H,3H,5H-[1,2,5]thiadiazolidin-1-oxides (IV). The present protocol has advantage of convenient operation to synthesize heterocyclics in good yield.
- Kaur, Manpreet,Singh, Baldev
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p. 1157 - 1161
(2014/08/05)
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- Cyanide as a powerful catalyst for facile synthesis of benzofused heteroaromatic compounds via aerobic oxidation
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Highly efficient synthesis of benzofused heteroaromatic compounds via aerobic oxidation catalyzed by cyanide anion has been developed. The Schiff bases derived from 2-aminophenol and aldehydes provided the corresponding benzoxazoles in high yields in the presence of a catalytic amount of cyanide in an open flask under ambient conditions without the use of any external metal co-oxidants and bases. Furthermore, we have developed a catalytic sequential one-step protocol for the synthesis of benzoxazoles by adding a catalytic amount of NaCN to Schiff bases generated in situ from 2-aminophenol and aldehydes without the isolation of imine intermediates. This one-pot protocol was further extended to the synthesis of benzothiazoles from 2-aminothiophenol and aldehydes. A variety of aldehydes could be applied to this sequential one-pot protocol and the desired benzofused azole products were obtained in high yields.
- Cho, Yeon-Ho,Lee, Chun-Young,Cheon, Cheol-Hong
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p. 6565 - 6573
(2013/07/26)
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- Ni nanoparticles: Mild and efficient catalyst for the chemoselective synthesis of 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines
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(Chemical Equation Presented) A new and efficient method has been developed for the synthesis of biologically significant 2-arylbenzimidazoles, 2-arylbenzothiazoles, and azomethines using recyclable and inexpensive polyvinyl pyrrolidone (PVP)-stabilized Ni nanoparticles in ethylene glycol at room temperature in excellent yields. Copyright Taylor & Francis Group, LLC.
- Khurana, Jitender M.,Sneha,Vij, Kanika
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experimental part
p. 2606 - 2616
(2012/08/08)
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- Cyanide as a powerful catalyst for facile preparation of 2-substituted benzoxazoles via aerobic oxidation
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A cyanide-catalyzed synthesis of 2-substituted benzoxazoles from Schiff bases via aerobic oxidation has been developed. The products from various Schiff bases were obtained in high yields in an open flask under ambient conditions without other external oxidants. We have also developed a simple one-step protocol for the synthesis of benzoxazoles from aminophenol and the corresponding aldehydes in the presence of cyanide without isolation of imine intermediates. Copyright
- Cho, Yeon Ho,Lee, Chun-Young,Ha, Deok-Chan,Cheon, Cheol-Hong
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supporting information
p. 2992 - 2996
(2013/01/15)
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- An efficient synthesis of 2-substituted benzoxazoles using cerium(III) chloride/sodium iodide as catalyst
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An efficient and environmentally benign method for the synthesis of 2-substituted benzoxazoles is reported. The condensation of 2-aminophenol with an aldehyde gave an imine intermediate, which was cyclized and dehydrogenated to 2-substituted benzoxazole with good yield in the presence of CeCl 3 /NaI as catalyst. The one-pot synthesis was carried out in toluene at 100 ° C using O 2 as the oxidant.
- Zhu, Xun,Wei, Yunyang
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p. 211 - 214
(2013/01/16)
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- Facile preparation of 2-substituted benzoxazoles and benzothiazoles via aerobic oxidation of phenolic and thiophenolic imines catalyzed by polymer-incarcerated platinum nanoclusters
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Platinum nanoclusters supported on a polymer/carbon black composite material was found to be an excellent catalyst for the oxidative cyclization of phenolic and thiophenolic Schiff bases to 2-substituted benzoxazoles and benzothiazoles under ambient conditions. Copyright
- Yoo, Woo-Jin,Yuan, Hao,Miyamura, Hiroyuki,Kobayashi, Shu
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supporting information; experimental part
p. 3085 - 3089
(2012/01/02)
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- Simple and efficient one-pot synthesis of 2-substituted benzoxazole and benzothiazole
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2-Substituted benzoxazole and benzothiazole were synthesized from condensation of aldehyde and 2-aminophenol or 2-aminothiophenol via a one-pot process using diethyl bromo phoshonate and tert-butyl hypochlorite.
- Patil, Sachin S.,Bobade, Vivek D.
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experimental part
p. 206 - 212
(2010/03/30)
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- Selective alkylation of aminophenols
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O-or N-Alkylated derivatives of aminophenols are important synthetic intermediates in organic synthesis. A series of aminophenols were selectively alkylated on their hydroxyl group in good yields via benzaldehyde protection of the amino group, subsequent alkylation, and hydrolysis; or on their amino group via imination and following reduction. ARKAT USA, Inc.
- Wang, Renchao,Xu, Jiaxi
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experimental part
p. 293 - 299
(2010/10/02)
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- Efficient aerobic oxidative synthesis of 2-substituted benzoxazoles, benzothiazoles, and benzimidazoles catalyzed by 4-Methoxy-TEMPO
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(Chemical Equation Presented) Setting the TEMPO: The scheme shows the efficient aerobic synthesis of 2-substituted benzoxazoles, benzothiazoles, and benzimidazoles where 4-methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy free radical (4-Methoxy-TEMPO) is used as the catalyst.
- Chen, Yong-Xing,Qian, Ling-Feng,Zhang, Wei,Han, Bing
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scheme or table
p. 9330 - 9333
(2009/05/15)
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- Hypervalent iodine(III) mediated synthesis of 2-substituted benzoxazoles
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2-Substituted benzoxazoles (6a-j, 7a-e, 7j-l) have been synthesized via the oxidative intramolecular cyclization of Schiff's bases (4a-j, 5a-e, 5j-l) using iodobenzene diacetate (IBD) as an oxidant in dry methanol. A one-pot procedure for the synthesis of 6a-j, 7a-e and 7j-l starting from o-aminophenol/p-chloro-o- aminophenol and aldehydes has also been developed.
- Prakash, Om,Batra, Anita,Sharma, Vijay,Saini, Rajesh K.,Verma, Rajender S.
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p. 1031 - 1034
(2007/10/03)
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- Synthesis of 2-arylbenzoxazoles via DDQ promoted oxidative cyclization of phenolic Schiff bases - A solution-phase strategy for library synthesis
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The Schiff base derived from the condensation of o-aminophenol with benzaldehydes was induced to undergo oxidative cyclization in the presence of DDQ. The resulting 2-arylbenzoxazoles were separated from the reduced DDQ by product by treatment of reaction mixture with a strongly basic ion-exchange resin. The applicability of this chemistry to spatially separate library synthesis is demonstrated by the preparation of a 352-member library.
- Chang, Junbiao,Zhao, Kang,Pan, Shifeng
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p. 951 - 954
(2007/10/03)
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- Sodium borohydride on wet clay: Solvent-free reductive amination of carbonyl compounds using microwaves
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A solvent-flee reductive amination of carbonyl compounds by wet montmorillonite K 10 clay supported sodium borohydride is described; microwave irradiation facilitates the procedure.
- Varma, Rajender S.,Dahiya, Rajender
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p. 6293 - 6298
(2007/10/03)
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