- Consequent Construction of C-C and C-N Bonds via Palladium-Catalyzed Dual C-H Activation: Synthesis of Benzo[ c]cinnoline Derivatives
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A highly efficient palladium-catalyzed cascade annulation of pyrazolones and aryl iodides to access various benzo[c]cinnoline derivatives has been achieved at 80 °C. A pyridine-type ligand could improve the reaction efficiency under current reaction conditions, giving a higher product yield up to 94%. This novel approach provided a one-pot dual C-H activation strategy with good functional group tolerance, such as halogen, methoxy, nitro, ester, phenol, and so forth. The product could readily convert into cinnoline derivatives.
- Li, Hongsheng,Zhao, Junhao,Yi, Songjian,Hu, Kongzhen,Feng, Pengju
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- Well-defined styryl and biphenyl calcium complexes from dilithio compounds and calcium iodide: Synthesis, structure and reactivity toward nitrous oxide
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Efficient synthesis and structure elucidation of carbon-calcium σ-bonded compounds are of remarkable interest and importance in organometallic chemistry of the heavier s-block metals. In this paper, we report that styryl and biphenyl calcium complexes wit
- Wei, Baosheng,Zhang, Wen-Xiong,Xi, Zhenfeng
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- Cooperative effect of acid sites in the photocyclization of azobenzene within the zeolite microenvironment
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Photolysis of azobenzene in the presence of a series of acidic zeolites with different crystal size (0.8 and 0.3 μm), crystalline structure (Y, β, ZSM-5), and framework Si-to-Al ratio (Al/cage ranging from 4.6 to 0.25) gives rise to benzo[c]cinnoline and benzidine. The latter remains protonated within the zeolite cavities, as has been established by FT-IR spectroscopy of the hosts. The lack of influence of the crystallite size on the activity of the zeolite reveals that the reaction is mainly taking place on the internal surface of these microporous solids. Finally, the relationship between the activity of the zeolite and the number of Bro?nsted sites per α-cage indicates that only two H+ per supercavity can participate in the photocyclization of azobenzene. This result agrees with the relative size of the zeolite cavities and the reactant molecules.
- Corma, Avelino,García, Hermenegildo,Iborra, Sara,Martí, Vicente,Miranda, Miguel A.,Primo, Jaime
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- Stable Organic Neutral Diradical via Reversible Coordination
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We report the formation of a stable neutral diboron diradical simply by coordination of an aromatic dinitrogen compound to an ortho-phenyldiborane. This process is reversible upon addition of pyridine. The diradical species is stable above 200 °C. Computations are consistent with an open-shell triplet diradical with a very small open-shell singlet-triplet energy gap that is indicative of the electronic disjointness of the two radical sites. This opens a new way of generating stable radicals with fascinating electronic properties useful for a large variety of applications.
- Lu, Zhenpin,Quanz, Henrik,Burghaus, Olaf,Hofmann, Jonas,Logemann, Christian,Beeck, Sebastian,Schreiner, Peter R.,Wegner, Hermann A.
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- Electrosynthesis of Azobenzenes Directly from Nitrobenzenes
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The electrochemical reduction strategy of nitrobenzenes is developed. The chemistry occurs under ambient conditions. The protocol uses inert electrodes and the solvent, DMSO, plays a dual role as a reducing agent. Its synthetic value has been demonstrated by the highly efficient synthesis of symmetric, unsymmetric and cyclic azo compounds.
- Ma, Yanfeng,Wu, Shanghui,Jiang, Shuxin,Xiao, Fuhong,Deng, Guo-Jun
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p. 3334 - 3338
(2021/10/29)
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- Chemoselective electrochemical reduction of nitroarenes with gaseous ammonia
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Valuable aromatic nitrogen compounds can be synthesized by reduction of nitroarenes. Herein, we report electrochemical reduction of nitroarenes by a protocol that uses inert graphite felt as electrodes and ammonia as a reductant. Depending on the cell voltage and the solvent, the protocol can be used to obtain aromatic azoxy, azo, and hydrazo compounds, as well as aniline derivatives with high chemoselectivities. The protocol can be readily scaled up to >10 g with no decrease in yield, demonstrating its potential synthetic utility. A stepwise cathodic reduction pathway was proposed to account for the generations of products in turn.
- Chang, Liu,Li, Jin,Wu, Na,Cheng, Xu
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supporting information
p. 2468 - 2472
(2021/04/02)
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- Cu-Catalyzed tandem: N -arylation of phthalhydrazides with cyclic iodoniums to yield dihydrobenzo [c] cinnolines
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Dihydrocinnolines have significant pharmacological properties. Herein, we investigate a Cu-catalyzed tandem N-arylation reaction of phthalhydrazides with cyclic iodonium salts to construct dihydrobenzo[c]cinnoline derivatives. Various iodonium salts, such as symmetrical, unsymmetrical, aryl-aryl, and aryl-heteroaryl ones, could react with phthalhydrazides smoothly and give the title products in moderate to high yields. Moreover, the -NH2 group, which has been diarylated by cyclic iodonium salts to form carbazoles in previous reports, is also well tolerated in this work. This journal is
- Kong, Xiangfei,Li, Shiqing,Lv, Hongxu,Xie, Rongrong,Ye, Xiuqing
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p. 4824 - 4830
(2020/07/13)
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- Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
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A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
- Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
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supporting information
(2020/02/15)
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- Catalytic Azoarene Synthesis from Aryl Azides Enabled by a Dinuclear Ni Complex
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Azoarenes are valuable chromophores that have been extensively incorporated as photoswitchable elements in molecular machines and biologically active compounds. Here, we report a catalytic nitrene dimerization reaction that provides access to structurally and electronically diverse azoarenes. The reaction utilizes aryl azides as nitrene precursors and generates only gaseous N2 as a byproduct. By circumventing the use of a stoichiometric redox reagent, a broad range of organic functional groups are tolerated, and common byproducts of current methods are avoided. A catalyst featuring a Ni - Ni bond is found to be uniquely effective relative to those containing only a single Ni center. The mechanistic origins of this nuclearity effect are described.
- Powers, Ian G.,Andjaba, John M.,Luo, Xuyi,Mei, Jianguo,Uyeda, Christopher
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supporting information
p. 4110 - 4118
(2018/03/29)
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- Metal-free deoxygenation and reductive disilylation of nitroarenes by organosilicon reducing reagents
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A metal-free deoxygenation and reductive disilylation of nitroarenes was achieved using N,N’-bis(trime-thylsilyl)-4,4’-bipyridinylidene (1) under mild and neutral reaction conditions, and a broad functional group tolerance was possible in this reaction. Mono-deoxygenation, giving a synthetically valuable N,O-bis(trimethylsilyl)phe-nylhydroxylamine (7a) as a readily available and safe phenylnitrene source from nitrobenzene, and double-deoxy-genation, giving N,N-bis(trimethylsilyl)anilines 8, were easily controlled by varying the amounts of 1 and reaction temperature as well as adding dibenzothiophene (DBTP). Reaction of 2-arylnitrobenzenes with 1 resulted in the formation of the corresponding carbazoles 14 via in situ-gen-erated phenylnitrene species derived by thermolysis of N,O-bis(trimethylsilyl)phenylhydroxylamines 7, followed by their subsequent intramolecular C H insertion. In addition, the intramolecular N N coupling reaction proceeded in the reduction of 2,2’-dinitrobiphenyl derivatives by 1, giving the corresponding benzo[c]cinnolines.
- Bhattacharjee, Argha,Hosoya, Hiromu,Ikeda, Hideaki,Nishi, Kohei,Tsurugi, Hayato,Mashima, Kazushi
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supporting information
p. 11278 - 11282
(2018/10/20)
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- Visible-Light-Induced Synthesis of Carbazoles by in Situ Formation of Photosensitizing Intermediate
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A visible-light-induced synthesis of N-H carbazoles from easily accessible 2,2′-diaminobiaryls in the absence of any external photosensitizer is reported. The process only requires tBuONO and natural resources, visible light, and molecular oxygen for the synthesis of N-H carbazoles. Experimental and computational studies support that the in situ formation of a visible-light-absorbing photosensitizing intermediate, benzocinnoline N-imide, is responsible for the activation of triplet molecular oxygen to singlet oxygen that, in turn, promotes the synthesis of carbazole.
- Chatterjee, Tanmay,Roh, Geum-Bee,Shoaib, Mahbubul Alam,Suhl, Chang-Heon,Kim, Jun Soo,Cho, Cheon-Gyu,Cho, Eun Jin
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p. 1906 - 1909
(2017/04/11)
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- Selective formation of benzo[c]cinnoline by photocatalytic reduction of 2,2′-dinitrobiphenyl using TiO2 and under UV light irradiation
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Photocatalytic reduction of 25 μmol 2,2′-dinitrobiphenyl in 50% aqueous iso-propanol and 50 mg P25-TiO2 under an argon atmosphere and 20 h UV light irradiation selectively produced 23.8 μmol of benzo[c]cinnoline (95%), and 2,2′-biphenyldiamine (5%) whose amount gradually increased with the irradiation time beyond 20-24 h due to further reduction of benzo[c]cinnoline. This journal is
- Kaur, Jaspreet,Pal, Bonamali
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supporting information
p. 8500 - 8503
(2015/05/20)
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- A facile synthesis of functionalized 7,8-diaza[5]helicenes through an oxidative ring-closure of 1,1'-binaphthalene- 2,2'-diamines (BINAMs)
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A facile and moderately functional-group-tolerant synthetic method for the preparation of 7,8-diaza[5]helicenes has been developed. It comprises of an oxidative ring-closing process of 1,1'-binaphthalene-2,2'-diamine (BINAM) derivatives with a chlorinecontaining oxidant (t - BuOCl) in the presence of a base (2,6-lutidine). In addition the basic physicochemical properties of newly synthesized compounds have been investigated.
- Takeda, Youhei,Okazaki, Masato,Maruoka, Yoshiaki,Minakata, Satoshi
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supporting information
p. 9 - 15
(2015/01/30)
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- Oxidative skeletal rearrangement of 1,1′-binaphthalene-2,2′- diamines (BINAMs) via C-C bond cleavage and nitrogen migration: A versatile synthesis of U-shaped azaacenes
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An oxidative skeletal rearrangement of 1,1′-binaphthalene-2,2′- diamines (BINAMs) that involves the cleavage of a strong C-C single bond of the binaphthalene unit and the nitrogen migration has been discovered. The unprecedented rearrangement enables access to a series of U-shaped azaacenes otherwise difficult to prepare in a selective manner by classical methods. Moreover, physicochemical properties of the unique azaacenes have been comprehensively investigated. This journal is the Partner Organisations 2014.
- Takeda, Youhei,Okazaki, Masato,Minakata, Satoshi
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supporting information
p. 10291 - 10294
(2014/08/18)
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- One-pot preparation of azobenzenes from nitrobenzenes by the combination of an indium-catalyzed reductive coupling and a subsequent oxidation
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We demonstrated how a reduction step with a reducing system comprised of In(OTf)3 and Et3SiH and a subsequent oxidation that occurred under an ambient (oxygen) atmosphere allowed the highly selective and catalytic conversion of aromatic nitro compounds into symmetrical or unsymmetrical azobenzene derivatives. This catalytic system displayed a tolerance for the functional groups on a benzene ring: an alkyl group, a halogen, an acetyl group, an ester, a nitrile group, an acetyl group, an ester moiety, and a sulfonamide group.
- Sakai, Norio,Asama, Shun,Anai, Satsuki,Konakahara, Takeo
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p. 2027 - 2033
(2014/03/21)
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- Reduction of 2,2′-dinitrobiphenyl with hydrazine hydrate catalyzed by Pd/C: Cobalt(II), zinc(II) and mercury(II) complexes with benzo[c]cinnoline and N2,N2′-bis(3-phenylallylidene)biphenyl-2,2′- diamine
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The catalytic reduction of 2,2′-dinitrobiphenyl with different molar ratios of hydrazine hydrate resulted in two different compounds; benzo[c]cinnoline (L1) and 2,2′-diaminobiphenyl. N 2,N2′-bis(3-phenylallylidene)biphenyl-2,2′- diamine (L2) has been synthesized by the condensation of 2,2′-diaminobiphenyl with cinnamaldehyde. Complexes of the type ML 12X2 and ML2X2 (M = Co(II), Zn(II); X = Cl, Br or I and Hg(L2)Cl2) have been synthesized and characterized by CHN analysis, IR, 1H NMR and UV-Vis spectroscopy. The crystal structures of Co(L1)2Cl 2, Zn(L1)2Br2 and Hg(L 2)Cl2 were determined using single crystal X-ray diffraction. In these three complexes, the coordination polyhedron about the central metal ion is best described as a distorted tetrahedron. The Co(L 1)2Cl2, and Zn(L1) 2Br2 complexes exhibit supramolecular structures resulting from π-π stacking of the benzo[c]cinnoline ligands. The diimine ligand, L2, in the Hg(L2)Cl2 complex coordinates to Hg(II) through the two nitrogens of the two phenyl rings to form a seven-membered metallocycle. Furthermore, the ligand prefers a trans-trans arrangement in the Hg(L2)Cl2 complex.
- Dehghanpour, Saeed,Afshariazar, Farzaneh,Assoud, Jalil
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experimental part
p. 69 - 76
(2012/05/20)
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- Synthesis of Carbazole, Acridine, Phenazine, 4H-Benzo[def]carbazole and Their Derivatives by Thermal Cyclization Reaction of Aromatic Amines
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A variety of nitrogen-containing heterocycles were synthesized by passing vapors of aromatic amines over calcium oxide at 450-650 °C under nitrogen carrier gas. Reaction of 2-aminobiphenyl 3a at 560 °C gave carbazole 4 in 80% yield. Reaction of 2,2′-diaminobiphenyl 3b afforded a mixture of carbazole 4 and 4-aminocarbozole 6b. In the case of 2-amino-2′ -nitrobiphenyl 3c, benzo[c]cinnoline 7 was obtained along with carbazole 4. Reaction of 2-amino-2′-methoxybiphenyl 3d gave four products of carbazole 4, 4-hydroxycarbazole 6e, phenanthridine 8 and dibenzofuran 9. Reaction of 2-aminodiphenylmethane 5a afforded acridine 10. In the case of 2-aminobenzophenone 5b, acridone 11 was obtained as a major product. Reaction of 2-aminobenzhydrol 5c gave acridine 10. When 2-aminodiphenylamine 5d was reacted, phenazine 12 was obtained in good yield. In contrast, reaction of 2-aminodiphenyl ether 5e produced only 2-hydroxydiphenylamine 13. Reaction of 4-aminophenanthrene 14 produced 4H-benzo[def]carbazole 15 in 61% yield.
- Horaguchi, Takaaki,Oyanagi, Takako,Creencia, Evelyn Cuevas,Tanemura, Kiyoshi,Suzuki, Tsuneo
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- Investigations of a novel process to the framework of benzo[c]cinnoline
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A novel synthetic process leading to the framework of benzo[c]cinnoline has been discovered and investigated. The process is composed of two separate reactions, the first of which is a partial reduction of the nitro groups of the 2,2′-dinitrobiphenyl, a process that we believe proceeds via a SET mechanism to yield the hydroxyamino and nitroso groups. In the following step the cyclization takes place under formation of the -N=N- bond. We believe that this process take place via a radical mechanism through the nitroso radical anion. The novel process affords either benzo[c]cinnoline or benzo[c]cinnoline N-oxide, both in high yields, 93% and 91%, respectively. To obtain benzo[c]cinnoline, the reaction is conducted with an alcohol as solvent and an alkoxide as the base, while for benzo[c]cinnoline N-oxide, water is used as solvent with sodium hydroxide as the base. To establish the latter procedure, statistical experimental design and multivariate modeling were utilized to reveal the response surface for the reaction and to determine the optimal conditions for the reaction. A proposal for the complex reaction mechanism is given. During the corroboration of the mechanism, a new deoxygenation reaction for converting benzo[c]cinnoline N-oxide into benzo[c]cinnoline was discovered. The reaction is conducted by treating the N-oxide with sodium ethoxide at elevated temperature to achieve near-quantitative conversion into benzo[c]cinnoline in a yield of 96%.
- Bjorsvik, Hans-Rene,Gonzalez, Raquel Rodriguez,Liguori, Lucia
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p. 7720 - 7727
(2007/10/03)
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- The newborn surface of dull metals in organic synthesis. Bismuth-mediated solvent-free one-step conversion of nitroarenes to azoxy- and azoarenes
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When milled together with bismuth shots, nitroarenes are readily converted to azoxy- and/or azoarenes depending on substrates and conditions employed. Simple extraction with organic solvent followed by evaporation of the resulting dark pasty solid gave the product in good yield.
- Wada, Shinobu,Urano, Mika,Suzuki, Hitomi
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p. 8254 - 8257
(2007/10/03)
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- Formation of 1,10-Disubstituted Benzo[c]cinnolines. Synthesis and Molecular Structure of 1-Amino-10-propylthiobenzo[c]cinnoline and Cyclization to 4-Propylcinnolino[5,4,3][c,d,e][1,2]benzothiazine
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The first 1,10-heterodisubstituted benzo[c]cinnoline derivative 1 was prepared from the trinitrobiphenyl 2. Investigation of the mechanism of ring closure in 2, 5, and 8 revealed a complex reduction-oxidation-cyclization sequence. The mechanism is discussed in light of the stereoelectronic demands of the substituent functionalities. Benzo[c]cinnoline derivative 1 [C15H15N3S, monoclinic, P21/c: a = 7.4063(3) A, b = 10.3739(5) A, c = 16.7642(8) A, β = 91.816(1)°, Z = 4] and its 5-N-oxide 7(N5) [C18H18N3OS, triclinic, P1: a = 8.1510(7) A, b = 8.6106(7) A, c = 12.102(1) A, α = 86.262(1)°, β = 83.364(1)°, γ = 74.711(1)°, Z = 4] were structurally characterized and showed a significant helical distortion of the heterocyclic ring. Oxidation of 1 with NCS or triamine 12 with PhI(OAc)2 led to a new heterocyclic ring system, ylide 13. Both benzo[c]cinnoline 1 and ylide 13 were characterized spectroscopically and the absorption spectra were correlated with the results of ZINDO calculations.
- Benin, Vladimir,Kaszynski, Piotr,Pink, Maren,Young Jr., Victor G.
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p. 6388 - 6397
(2007/10/03)
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- Bi-KOH. An efficient reagent for the coupling of nitroarenes to azo and azoxy compounds
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A simple and inexpensive procedure for the coupling of nitroarenes to azoxy compounds with bismuth and potassium hydroxide in methanol at ambient temperature is achieved. When carried out under microwave irradiation it gives exclusively azo compounds in excellent yields.
- Laskar, Dhrubojyoti Dey,Prajapati, Dipak,Sandhu, Jagir S.
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- Microbial deoxygenation of N-oxides with Baker's yeast-NaOH
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The microbial deoxygenation of a series of aromatic and heteroaromatic N-oxide compounds, including quinoline N-oxides, isoquinoline N-oxides, 2-aryl-2H-benzotriazole 1-oxides, benzo[c]cinnoline N-oxide and azoxybenzenes, has been performed with bakers'yeast-NaOH.
- Baik, Woonphil,Kim, Dong Ik,Koo, Sangho,Rhee, Jong Uk,Shin, Sung Hee,Kim, Byeong Hyo
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p. 845 - 848
(2007/10/03)
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- Modification of photochemical reactivity by nafion. Photocyclization and photochemical cis-trans isomerization of azobenzene
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The photophysical and photochemical behavior of azobenzene (AB) incorporated into solvent-swollen acid form Nafion (Nafion-H+) membranes were examined. In water-swollen Nafion-H+ membrane AB exhibits strong fluorescence at room temperature, which has never been observed in isotropic solvents. Photolysis of AB adsorbed in water-swollen Nafion-H+ results in its cyclization to give benzo[c]cinnoline (BC) and benzidine (BZ) in quantitative yield. The product distribution is very dependent upon the number of AB molecules in each water cluster of the Nafion membrane (occupancy number). In the case of the occupancy number greater than 2, BC and BZ are formed equimolarly, while when only one AB molecule exists in each water cluster, BC is exclusively produced. The AB molecules incorporated into methanol-swollen Nafion-H+ membrane do not emit fluorescence and only undergo cis-trans isomerization when they are photoirradiated. These observations suggest that in water-swollen Nafion-H+ AB molecules are solublized in the fluorocarbon/water interface, and the protons of the Nafion-H+ participate in the photochemical and photophysical processes of AB. On the other hand, in methanol-swollen Nafion-H+ membrane AB molecules are located in the methanol pools, and their photochemical and photophysical behaviors are not intervened by the Nafion protons.
- Tung, Chen-Ho,Guan, Jing-Qu
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p. 9417 - 9421
(2007/10/03)
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- Role of Alkali Halides in the Synthesis of Nitrogen Containing Heterocycles by Reductive Carbonylation of Aromatic Nitro-Derivatives Catalysed by Ru3(CO)12
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The presence of alkali halides as co-catalysts in the reductive carbonylation of o-nitrobiphenyl 1 catalysed by Ru3(CO)12 strongly increases the rate of reactions and slectivity towards heterocyclization products .With sodium halides, depending on the anion, the selectivity for carbazole is in the order Cl- > Br- ca.F- I-; whereas the selectivity for 5H-phenanthridin-6-one is the reverse I- > Br- ca.F- > Cl-.The influence of the cation can be explained with the polarization of a CO ligand of the ruthenium cluster, due to the interaction of the alkali cation with the oxygen lone pair.In fact high yields (>80percent) of heterocyclization products are obtained when the alkali cation is free to coordinate the CO.When this interaction is reduced, by sequestering the cation with crown-ethers, or better with cryptands, the yield of heterocyclic products is 14percent and 0percent respectively.The role of the anion and cation in the catalytic mechanism are discussed.The attempted extension of this reaction to other nitro-derivatives for the potential synthesis of aromatic heterocycles with larger rings are also reported.
- Pizzotti, Maddalena,Cenini, Sergio,Quici, Silvio,Tollari, Stefano
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p. 913 - 918
(2007/10/02)
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- Photolysis of 2-Amino-2'-azidobiphenyls: Formal Formation of Internally Trapped Didehydroazepines
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Photolysis of 2-amino-2'-azidobiphenyls in diethylamine gave 4,10-dihydroazepinoindoles (7), the structure of which corresponded to the didehydroazepines formally trapped with an internal amino group.However, the yields of 7 were considered low, which was due to the significant intramolecular interaction of the photolytically generated nitrene with an amino group, to afford benzocinnoline as a final product.
- Murata, Shigeru,Tsuji, Hiroshi,Tomioka, Hideo
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p. 895 - 897
(2007/10/02)
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- The Photo-Deoxygenation Of Heterocyclic N-Oxides
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2-Methoxy and 2-nitrophenazine 10-oxide are deoxygenated by irradiation in the presence of triethylamine, 2,3-dimethyl-2-butene and triethylphosphite via electron transfer to the singlet excited state, as shown by the comparison of reaction quantum yield and fluorescence quenching. 1,4-Dimethoxybenzene quenches the singlet, but causes no deoxygenation.The same mechanism operates in the photoreduction of benzocinnoline 5-oxide, but it is too slow to compete efficiently with the rearrangement in the case of quinoline 1-oxide.The photo-deoxygenation of the borontrifluoride ground state complexes of these substrate is in every case unefficient.
- Fasani, Elisa,Amer, Atef M.,Albini, Angelo
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p. 985 - 992
(2007/10/02)
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- Reduction of Nitroarenes Using an Activated Catalyst Prepared by the Reduction of Nickel Nitrate with Excess Zinc in the Presence of Hydrazine Monohydrate
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An activated catalyst prepared from a mixture of nickel nitrate hexahydrate with zinc in dry ethanol under reflux showed exceptional catalytic activity for the reduction of nitroarenes to the corresponding azoxy compounds exclusively in the presence of hydrazine monohydrate.However when nickel nitrate hexahydrate was replaced by nickel chloride dihydrate with zinc, only the aminoarenes were formed in high yields.With unactivated catalyst, the reduction reaction from a mixture of nitroarenes, nickel nitrate or chloride, excess zinc and hydrazine monohydrate gave the corresponding azo, azoxy and amino compounds in much lower yields.
- Yun, Tae Ho,Park, Moon Keu,Han, Byung Hee
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p. 2774 - 2788
(2007/10/02)
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- The role of alcohol in the catalytic reductive carbonylation of nitrobenzenes to carbamates in the presence of Rh(CO)4- or Ru3(CO)12
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The selectivity of N-phenylcarbamate from the reductive carbonylation of nitrobenzene using Rh(CO)4- or Ru3(CO)12-Et4N+Cl- as the catalyst is much higher in t-butyl alcohol than in primary or secondary alcohols; the latter two alcohols are readily involved in the reduction of nitrobenzene to aniline leading to lower selectivity of the corresponding carbamates.For example, when 2-butanol was used as the solvent for the reductive carbonylation of nitrobenzene, 2-butanone and aniline were observed in a molar ratio of 1:1.Similarly, the reductive carbonylation of p-n itrotoluene to give the corresponding carbamate in t-butyl alcohol is also higher in yield than in 2-butanol or in butanol.However, for dinitroarenes the selectivity of carbamates is low using either tBuOH or other primary and secondary alcohols.
- Liu, Charng-Hing,Cheng, Chien-Hong
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p. 119 - 123
(2007/10/02)
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- Photochemistry of Tetrabenzotetraazacyclododecine in 2-Propanol
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The photochemical properties of the tetraazacyclododecine 1 were investigated.The trans,trans isomer 1tt can be photoisomerized yielding the stable cis,cis isomer 1cc.The isomerization requires two photons and proceeds via the unstable trans,cis isomer 1tc.In nitrogen-purged 2-propanol as solvent 1 yields five stable photoproducts as a result of a number of consecutive photoreduction reactions.Our attempts to convert 1 by light into the tetraazetidine 4 were not successful. Key Words: cis-Azo compounds / Photoreduction / Tetrabenzotetraazacyclododecine
- Tauer, Erich,Grellmann, Karl-Heinz,Heinrich, Angelika
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p. 2053 - 2055
(2007/10/02)
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- Radical Cations and Anions of Benzocinnolines: An Electron Spin Resonance Study
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The radical cations of benzocinnoline and its four symmetrical dimethyl derivatives have been prepared by exposure of the parent compounds as dilute solutions in CFCl3 to 60Co γ-rays at 77 K.The e.s.r. spectra were all characterised by large hyperfine coupling to two equivalent nitrogen atoms.Analysis of the data gave ca. 9percent 2s and 44percent 2p character on each nitrogen, thereby establishing a ?-structure.Clear deviation from axial symmetry shows that the orbital axes are tilted with respect to each other, an estimate of the angle between the two principle directions being ca. 40 deg.This accords reasonably well with that derived from the p:s ratio of 4.9.The estimated total spin-density on nitrogen is 1.06, showing that the SOMO is strongly localised.Similar treatment of the 2,9- and 3,8-dimethoxy derivatives gave a broad unresolved singlet.This establishes that the SOMO has switched from the ?-(N)-orbital to a ?-orbital.Clearly this has very low spin-density on the two nitrogen atoms.We were not able to detect any of the radical cations in the liquid phase.Exposure of dilute solutions of all six compounds as dilute solutions in CD3OD gave parallel features characteristic of two equivalent 14N nuclei.The perpendicular splittings were close to zero, thus confirming that the SOMO is ?, the estimated spin-density on the two nitrogen atoms being ca. 34percent each.These anions were also prepared in liquid dimethoxyethane and hexamethylphosphoric triamide, and their e.s.r. and ENDOR spectra were recorded.Relative signs of the 1H coupling constants were obtained using general triple resonance.This has led to full assignments in all cases.Our assignment for the anion of the parent compound differs from that previously proposed.
- Fischer, Hans,Neugebauer, Franz A.,Chandra, Harish,Symons, Martyn C. R.
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p. 727 - 730
(2007/10/02)
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- Metathesis and reduction reactions of nitroso compounds with metal carbenes and metal carbonyls
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Reaction of nitroso compounds with metal-carbene complexes and metal carbonyls has been investigated.These reactions lead to reduction of the nitroso compounds, primarily to the corresponding azo- and azoxy compounds.Metal-nitrene complexes have been proposed as intermediates in these reactions.These intermediates couple rapidly with the unreacted nitroso compound, or enter into nitrene-like reactions with external or internal trapping agents.Reaction of metal carbonyls with nitrosoarenes and photolysis has been found to be an effective method for the reduction of nitrosoarenes to azoxyarenes, with few problems resulting from overreduction to amines or azo compounds.
- Herndon, James W.,McMullen, Leonard A.
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- The Reduction of Some 2,2'-Dinitrodiaryl Compounds and Related Compounds by Thiourea S,S-Dioxide (Formamidinesulfinic Acid)
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The reaction of thiourea S,S-dioxide (formamidinesulfinic acid) in ethanolic alkali with 2,2'-dinitrobiphenyl and several related dinitro compounds possessing an-X-bridge (where X = NH, NMe, O and S), located at the 1,1'-positions, has been investigated.With 2,2'-dinitrobiphenyl (which gives good yields of benzocinnoline and its oxides) and, to a minor extent, with 2,2'-dinitrodiphenylamine, an intramolecular reaction occured to give heterocyclic products; with each of the other dinitro compounds, the only product obtained was formed as the result of a Smiles rearrangement.
- Wilshire, John F. K.
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p. 995 - 1001
(2007/10/02)
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- Observations on the Reduction of Aryl Nitro Groups with Palladium-Sodium Borohydride
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The reduction of aryl nitro groups by the palladium-sodium borohydride system can be controlled in some instances to give products differing from those of catalytic hydrogenation.With six equivalents of borohydride added to the catalyst 2,2'-dinitrobiphenyl formed only 2,2'-diaminobiphenyl.With added sodium hydroxide and varying amounts of borohydride and catalyst, the reduction can be controlled to give benzocinnoline, benzocinnoline 5-oxide or benzocinnoline 5,6-dioxide.In a closed system, the reagents reduce both the nitro and olefin functional groups in 6-nitro-5,8-dimethoxy-1,4-dihydro-1,4-ethanonaphtalene.In an open flask flushed with argon, the reduction is confirmed to the nitro group.Reduction of 2-chloro and 4-chloronitrobenzene with palladium-borohydride gives substantial yields of the appropriate chloroanilines.In contrast, hydrogen and palladium give aniline as the major product from each of these.These results suggest that the addition of sodium borohydride to palladium on carbon produces a reductive entity differing from that of catalytic hydrogenation.
- Smith, William B.
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p. 745 - 748
(2007/10/02)
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- Reaction of Benzocinnolinium-5-(N-acyl- and N-benzimido-imides) with Diphenylcyclopropenone
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Benzocinnolinium-5-(N-acylimides) (6; R = Ph, OEt, or Me) give benzocinnoline and 2-substituted-4,5-diphenyloxazin-6-ones (7) on reaction with diphenylcyclopropenone.In contrast, the related benzocinnolinium-5-(N-benzimidoimides) (11; R = H, Ph, or p-tolyl) give stable adduct (12), which on pyrolysis yield benzocinnoline and 1-substituted-2,5,6-triphenylpyrimidin-4-ones.
- Barr, John J.,Storr, Richard C.,Tandon, Vishnu K.
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p. 1147 - 1149
(2007/10/02)
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- BIPHENYLENES AND HETEROCYCLIC ANALOGUES OF BIPHENYLENE. PART I. PREPARATION OF BIPHENYLENE AND OCTACHLOROBIPHENYLENE BY VACUUM PYROLYSIS OF BENZO(c)CINNOLINES; PYROLYSIS OF BENZOCINNOLINE N-OXIDE.
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Vacuum sublimation of benzocinnolines through a silica tube at 700-950 deg C gives biphenylenes in good yield.The first reaction when benzocinnoline N-oxide is similarly pyrolysed is deoxygenation to benzocinnoline.
- Kanoktanaporn, Santhi,MacBride, J. A. Hugh
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p. 2901 - 2910
(2007/10/02)
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