- Second-generation aryl isonitrile compounds targeting multidrug-resistant Staphylococcus aureus
-
Antibiotic resistance remains a major global public health threat that requires sustained discovery of novel antibacterial agents with unexploited scaffolds. Structure-activity relationship of the first-generation aryl isonitrile compounds we synthesized led to an initial lead molecule that informed the synthesis of a second-generation of aryl isonitriles. From this new series of 20 compounds, three analogues inhibited growth of methicillin-resistant Staphylococcus aureus (MRSA) (from 1 to 4 μM) and were safe to human keratinocytes. Compound 19, with an additional isonitrile group exhibited improved activity against MRSA compared to the first-generation lead compound. This compound emerged as a candidate worthy of further investigation and further reinforced the importance of the isonitrile functionality in the compounds’ anti-MRSA activity. In a murine skin wound model, 19 significantly reduced the burden of MRSA, similar to the antibiotic fusidic acid. In summary, 19 was identified as a new lead aryl isonitrile compound effective against MRSA.
- Kyei-Baffour, Kwaku,Mohammad, Haroon,Seleem, Mohamed N.,Dai, Mingji
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supporting information
p. 1845 - 1854
(2019/03/28)
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- Olefin cross-metathesis/Suzuki-Miyaura reactions on vinylphenylboronic acid pinacol esters
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A series of alkenyl phenylboronic acid pinacol esters has been synthesized via an olefin cross-metathesis reaction of vinylphenylboronic acid pinacol ester derivatives. After catalytic hydrogenation, the resulting boronates were coupled via a microwave-mediated Suzuki-Miyaura reaction to afford a library of biarylethyl aryl and biarylethyl cycloalkyl derivatives. A complementary reaction sequence involved an initial Suzuki-Miyaura coupling.
- Baltus, Christine B.,Chuckowree, Irina S.,Press, Neil J.,Day, Iain J.,Coles, Simon J.,Tizzard, Graham J.,Spencer, John
-
supporting information
p. 1211 - 1217
(2013/03/13)
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- Supported palladium nanoparticles as heterogeneous ligand-free catalysts for the Hiyama C-C coupling of vinylsilanes and halobenzenes leading to styrenes
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The Hiyama C-C coupling reaction of a wide range of aryl iodides and vinylsilanes has been performed using ligand-free solid catalysts based on supported palladium nanoparticles. Among the supports tested (Mg, TiO 2, CeO2 and active carbon), the most active catalysts were those in which palladium is supported on MgO and TiO2. Analogous Pt and Au materials were inefficient to promote this reaction. Leaching tests suggest that there is some contribution of dissolved Pd since Pd in solution has been detected and the scavenging test decreases the initial reaction rate. Although the solid Pd catalysts can be reused, it was, however, observed that they undergo a certain deactivation upon use that can be attributed to several factors including the presence of inorganic compounds on the catalyst, Pd leaching or agglomeration of Pd NPs.
- Grirrane, Abdessamad,Garcia, Hermenegildo,Corma, Avelino
-
-
- Dehydrogenation of nitro derivatives of bibenzyl to corresponding nitro stilbene with dioxygen catalyzed by 2,2,6,6-tetramethylpiperidine-1-oxyl
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A simple and effective oxidative dehydrogenation of nitro derivatives of bibenzyl was developed using a mixture of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and metal salts as catalyst under an atmospheric pressure of oxygen. The oxidation of several nitro derivatives of bibenzyl led to corresponding nitro stilbene in good yields, and the yields increased with the increase in the substituted nitro group on the bibenzyl. For example, the aerobic dehydrogenation of 2,2,4,4,6,6-hexanitrobibenzyl in the presence of a catalytic amount of TEMPO with metal salts gave 2,2,4,4,6,6-hexanitrostilbene in 81 % yield and 4,4-dinitrostilbene-2,2-disulfonic acid (75 %) was obtained from 4,4-dinitrobibenzyl-2,2-disulfonic acid. Iranian Chemical Society 2012.
- Lu, Tingting,Lu, Ming
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p. 971 - 975
(2013/02/25)
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- Synthesis of stilbene analogues by one-pot oxidation-Wittig and oxidation-Wittig-Heck reaction
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Synthesis of symmetrical (and unsymmetrical) stilbene derivatives is achieved by a combination of one-pot steps of Kornblum type oxidation of benzyl halide, its simultaneous in situ formation of phosphonium salt, and subsequently their Wittig reaction. In other variant it is oxidized to aldehyde, treated with ylide generated from phosphonium salt (CH3PPh3X) to give styrene, and subjected to Pd catalyzed Heck reaction with arylhalide to give stilbenes as the three-step one-pot sequence.
- Saiyed, Akeel S.,Patel, Krupa N.,Kamath, Bola V.,Bedekar, Ashutosh V.
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supporting information; experimental part
p. 4692 - 4696
(2012/09/10)
-
- On the dual role of N-heterocyclic carbenes as bases and nucleophiles in reactions with organic halides
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The synthetic consequences of different basicities, nucleophilicities, and sterics of N-heterocyclic carbenes have been studied in reactions of imidazolin-2-ylidenes with organic halides. Highly nucleophilic and less basic carbenes cleanly gave alkyli-deneimidazolines, the deoxy analogues of Breslow-type intermediates. More basic NHCs engaged in unwanted deprotonation or dehydrohalogenation reactions. Georg Thieme Verlag Stuttgart. New York.
- Knappke, Christiane E. I.,Arduengo, Anthony J.,Jiao, Haijun,Neudoerfl, Joerg-Martin,Jacobivonwangelin, Axel
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scheme or table
p. 3784 - 3795
(2012/01/11)
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- Gelation ability of novel oxamide-based derivatives bearing a stilbene as a photo-responsive unit
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Oxamide-based derivatives containing one or two oxamide moieties coupled to the 4- or 4,4′-positions of cis- and transstilbene have been synthesised. In order to modulate the solvent gelation tendencies, a series of derivatives with modified terminal functions were prepared from them. The transstilbene dioxamide-based derivatives were found to be sparingly soluble or insoluble in water and in organic solvents, whereas the trans-stilbene monooxamide-based derivatives are soluble in most organic solvents. Incorporation of a C 12 alkyl chain in the structure of the latter compounds results in a decreased solubility but in an increased gelation tendency of the substances. The ethyl ester oxamide-based derivative trans-3a and the amino acid oxamide-based derivative trans-3e act as efficient gelators of various organic solvents. In contrast, cis-3a shows a poor gelation ability or none at all, owing to its good solubility. Considering the difference in gelation abilities of the compounds trans-3a and cis-3a and the photo-responsive conformational changes of the stilbene part of the molecule, a controlled gelation by light was achieved. FT-IR and 1H NMR spectroscopic measurements support the view that hydrogen bonding between the oxamide fragments plays an important role in gel formation. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Miljanic, Snezana,Frkanec, Leo,Meic, Zlatko,Zinic, Mladen
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p. 1323 - 1334
(2007/10/03)
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- Aqueous Wittig reactions of aldehydes with in situ formed semistabilized phosphorus ylides
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The Wittig reactions of three semistabilized phosphorus ylides generated in situ from the corresponding phosphonium salts with aldehydes in water without any organic cosolvent were investigated. Most of the olefination reactions completed within between 5 min and 4.5 h in refluxing water containing 1.5 equiv of LiOH and 1.4M LiCl to afford the products in 65-100% yields. The E:Z selectivity depended not only on the substituent attached to the benzene ring of the ylides but also on the substituent bound to the aromatic aldehydes. LiCl promotes the aqueous Wittig reactions and suppresses decomposition of the ylide or the corresponding phosphonium salt. Copyright Taylor & Francis, Inc.
- Wu, Jinlong,Zhang, Da
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p. 2543 - 2551
(2007/10/03)
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- 3,5-Bis(trifluoromethyl)phenyl sulfones in the direct Julia-Kocienski olefination
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3,5-Bis(trifluoromethyl)phenyl (BTFP) sulfones 7 have been employed in the Julia-Kocienski olefination reaction with carbonyl compounds. Sulfones 7 are readily prepared in high yields (64-97%) from commercially available 3,5-bis(trifluoromethyl)thiophenol through an alkylation/oxidation two-step sequence. The stability of metalated BTFP sulfones has been studied and compared with heteroaryl benzothiazol-2-yl (BT), 1-phenyl-1H-tetrazol-5-yl (PT), and 1-tert-butyl-1H-tetrazol-5-yl (TBT) sulfones 9-11 under different reaction conditions. The Julia-Kocienski olefination between alkyl BTFP sulfones 7 and a wide variety of aldehydes affords the corresponding 1,2-disubstituted alkenes and dienes in good yields and stereoselectivities. This one-pot protocol can be performed using KOH at room temperature or the phosphazene bases P2-Et and P4-t-Bu at -78 °C or rt and has been successfully used in a high-yielding and stereoselective synthesis of various methoxylated stilbenes such as trimethylated resveratrol. These new reaction conditions for the Julia-Kocienski olefination reaction have been also studied with BT, PT, and TBT sulfones, giving poorer results. Methylenation of aliphatic and aromatic aldehydes, ketones, and 1,2-dicarbonyl compounds is carried out through the modified Julia olefination using BTFP methyl sulfone 7d to give terminal alkenes and dienes. Mechanistic studies of the olefination reaction between benzyl BTFP sulfone 7a and aromatic aldehydes performed by KOH-induced Smiles rearrangement of stereodefined syn- and anit-β-hydroxyalkyl BTFP sulfones indicate that the stereocontrol of the reaction is determined in the elimination step. 2005 American Chemical Society.
- Alonso, Diego A.,Fuensanta, Monica,Najera, Carmen,Varea, Montserrat
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p. 6404 - 6416
(2007/10/03)
-
- Experimental evidence for multiple oxidation pathways in the (salen)Mn-catalyzed epoxidation of alkenes
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The substrate electronic effects on the selectivity in the catalytic epoxidation of para-substituted cis stilbenes 2a-i were investigated by using (R,R)-[N,N′-bis(3,5-di-tBu-salicylidene)-1,2-cyclohexanediamine] manganese(III) chloride 1 in benzene as the catalyst with iodosobenzene as the terminal oxidant. A Hammett study of the selectivity results reveals a stronger electrophilic character than previously assumed in the (salen)Mn-catalyzed reaction. In general, the best correlations with the experimental values were obtained by using the Hammett σ+ values, which gave ρ = -1.37 for the rate of cisepoxide formation and ρ = -0.43 for the rate of the stepwise process leading to the corresponding trans product. The reaction involves two separate pathways as indicated also by the competitive breakdown of the intermediate on the path to trans epoxide for methoxy-substituted substrates. The asynchronicity in the concerted pathway leading to cis epoxide is apparent for 4-methoxy-4′-nitrostilbene, which yields cis epoxide with 75% ee entirely as a result of electronic effects.
- Linde, Christian,Koliai, Nordine,Norrby, Per-Ola,Akermark, Bjoern
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p. 2568 - 2573
(2007/10/03)
-
- InCl3-Zn. A novel reduction system for the deoxygenative coupling of carbonyl compounds to olefins
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A simple and inexpensive procedure for the deoxygenative homo-coupling and cross-coupling of carbonyl compounds with InCl3-Zn system in dry acetonitrile at ambient pressure is achieved. The procedure gives excellent yields of E-olefinic products.
- Barman,Thakur,Prajapati,Sandhu
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p. 515 - 516
(2007/10/03)
-
- Solvolytic stereoselective debromination of vic-dibromides with HMPA
-
A simple and efficient procedure for the debromination of vic-dibromides has been reported with hexamethylphosphoric triamide at 155-160°C under a nitrogen atmosphere without the aid of any reagent.
- Khurana,Bansal,Chauhan
-
p. 1089 - 1091
(2007/10/03)
-
- REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEUR DERIVATIVES. PART II. THE REACTION OF TRIVALENT PHOSPHORUS ACID SALTS WITH THE BENZYLIC HALIDES SYSTEM
-
The reaction of the benzylic halides systems with sodium dialkylphosphites as well as the sodium salt of dibenzylphosphine oxide in THF and alcohols as the solvents is described.According to the constitution of the starting materials, the formation of the P-C bond, dehalogenation or dimerization occurs.Probable mechanisms namely SET and X-philic substitution are discussed.Key words: Benzylic halides system, dialkylphosphites, dibenzylphosphine oxide, Michaelis-Becker reaction, X-philic substitution.
- Witt, Dariusz,Rachon, Janusz
-
p. 153 - 164
(2007/10/02)
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- Electron-transfer versus Nucleophilic Substitution in the Reactions of α-Halogenated 4-Nitrotoluenes with Base
-
A comparative study of the reactions of 4-nitrobenzyl and 4-nitrobenzylidene halides (ArCHXY; Ar = 4-NO2C6H4-; X = H or Halogen; Y = Halogen) with alkali shows that the reaction is sensitive to the nature of the side chain halogen substituent(s) as well as the reaction conditions.In alcoholic alkali, only 4-nitrobenzyl chloride (ArCH2Cl) reacts smoothly via the electron transfer (ET)-radical pathway to give mainly dimeric products while the corresponding bromide (ArCH2Br) and iodide (ArCH2I) give exclusively SN products.The ET pathway is enhanced for these substrates by the application of phase-transfer catalysis.In the case of the 4-nitrobenzylidene dihalides (ArCHXY; X = Y = Cl; X = Cl, Y = Br; X = Y = Br; X = F, Y = Br) it is also shown that although progressive bromine substitution suppresses the ET pathway, application of phase-transfer catalysis minimises competing solvolytic reactions and enhances the radical reaction.
- Kam, Toh-Seok,Lim, Tuck-Meng
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p. 147 - 150
(2007/10/02)
-
- Electrochemical reduction of certain fluorenyl and xanthenyl olefins
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The reduction of certain fluorene and xanthene containing olefins at a mercury electrode using cyclic voltammetry has been investigated.In DMF, fluorene-9-(4-nitrophenyl)methylene (1) reveals two distinct reversible one-electron redox waves corresponding to anion radical and dianion formation.Some other olefins particularly stilbenes (9-14) and substituted propenones (7,8) show commonality in the emergence of at least one distinct reversible reduction couple.Anion radicals of nearly all of the olefins (1-14) studied in this work generated electrochemically or by chemical 1-electron reductants, exhibited considerable stability.
- Handoo, Kishan L,Kaul, Anju
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p. 579 - 583
(2007/10/02)
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- C-ALKYLATION OF β-DIKETONES WITH BENZYLPYRIDINIUM SALTS. EVIDENCE FOR CHAIN RADICAL MECHANISMS
-
1-(p-Substituted benzyl)-2,4,6-triphenylpyridinium cations react with β-diketone anions by mechanisms which depend on the para-substituent.The p-methoxybenzyl derivative undergoes SN1 displacement yielding O- and C-benzylated products.The p-nitrobenzyl compound reacts by a chain radicaloid mechanism and gives high yields of C-p-nitrobenzylated diketones.The parent benzyl compound forms some C- and some O-benzylated products, together with bibenzyl, probably by a radical chain reaction which was suppressed by radical traps.
- Marquet, Jorge,Moreno-Manas, Marcial,Pacheco, Pedro,Prat, Maria,Katritzky, Alan R.,Brycki, Bogumil
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p. 5333 - 5346
(2007/10/02)
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- Nucleophilic C-C Linkages of 2-Nitro- and 3-Nitro-1,6-methanoannulenes
-
By "vicarious nucleophilic substitutions" of 2- and 3-nitro-1,6-methanoannulenes (2, 3) the new compounds 4 - 13 are obtained.Reactions of 2, 3 with sodium methoxide lead to the Ethers 16 and 17, oxidative coupling reactions in the presence of MnO2 to 18, and Meisenheimer complexes, followed by oxidation to the nitromethane derivatives 14 and 15. - Keywords: 1,6-Methanoannulenes, 2- and 3-nitro/ Vicarious nucleophilic substitution
- Neidlein, Richard,Lautenschlaeger, Gabriele
-
p. 493 - 498
(2007/10/02)
-
- PREPARATION AND ELECTRON TRANSFER-INDUCED cis-trans ISOMERIZATION REACTIONS OF 1-(5-NITRO-2-FURYL)-, 1-(5-NITRO-2-THIENYL)-, AND 1-(4-NITROPHENYL)-2-R ETHYLENES
-
Mixtures of E- and Z-isomers of 1,2-bis(5-nitro-2-furyl)ethylene (I), 1-(5-nitro-2-furyl)-2-(4-nitrophenyl)ethylene (II), 1,2-bis(4-nitrophenyl)ethylene (III), 1-(5-methoxycarbonyl-2-furyl)-2-(4-nitrophenyl)ethylene (IV), 1-(5-methoxycarbonyl-2-furyl)-2-(5-nitro-2-furyl)ethylene (V) and 1-(5-methoxycarbonyl-2-furyl)-2-(5-nitro-2-thienyl)ethylene (VI) were prepared by the Wittig reaction.These derivatives were isomerized by electron transfer-induced reactions via the radical anion in the CT-complex using aniline as electron donor at 25 deg C in the light or at 80 deg C in the dark.The starting as well as the final E:Z ratio was determined by 1H NMR spectroscopy.In all cases only the cistrans isomerization was observed.
- Prousek, Josef,Hayden, Viktor
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p. 1675 - 1682
(2007/10/02)
-
- Application of Phase-Transfer Catalysis to the Synthesis of Mono- and Bis-stilbenes and Styryls
-
A novel and convenient method has been developed for the synthesis of substituted stilbenes by the condensation of active methyl group in suitably substituted toluenes with aromatic aldehydes in aq. medium at room temperature using benzyltriethylammonium chloride as a phase-transfer catalyst.This method has also been applied for the preparation of heterocyclic styryls and extended to the synthesis of bis-stilbenes and bis-styryls using aromatic dialdehydes in place of monoaldehydes.A comparison of the results shows that the present method is superior to the conventional methods in many respects.
- Lokhande, S. B.,Rangnekar, D. W.
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p. 485 - 488
(2007/10/02)
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- REACTIONS AT HIGH PRESSURE, PART 18; VOLUMES OF ACTIVATION AND OF REACTION FOR THE WITTIG REACTION
-
Volumes of activation have been obtained from rate measurements between 1 and 1000 bar of reactions between triphenyl-p-nitrobenzylidenephosphorane and a series of substituted benzaldehydes.Values of ΔVexcit. lie in the range -20 to -30 cm3mol-1 and are somewhat solvent-dependent.These measurements are in agreement with the accepted reaction mechanism and suggest that the scope of the reaction may be extended by the use of high pressures.
- Isaacs, Neil S.,Abed, Obeid Hassan
-
p. 995 - 996
(2007/10/02)
-
- Electron Apportionment in Cleavage of Radical Anions. 1. Nitro-Substituted Benzyl Phenyl Ethers
-
The radical anions of 4-nitrobenzyl phenyl ethers undergo cleavage at least 10E4 times faster than the radical anions of corresponding 4-nitrophenyl benzyl ethers despite a perceived thermodynamic advantage for the latter set of reactions.It is suggested that this results reflects a kinetic advantage for cleavage reactions which take place with regioconservation of spin density.
- Maslak, Przemyslaw,Guthrie, Robert D.
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p. 2628 - 2636
(2007/10/02)
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- Electron Transfer in Competition with Loss of Nitrogen in Photochemical Reactions of Aryldiazomethane with Diethylamine
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The photolysis of aryldiazomethanes was studied as a function of aryl substituents and the p-nitro group was found to exert a special effect of product distribution.
- Tomioka, Hideo,Tabayashi, Kazuo,Izava, Yasuji
-
p. 906 - 907
(2007/10/02)
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- The Autoxidation of Alkylnitroaromatic Compounds in Base-catalysed Phase-transfer Catalysis by Polyethylene Glycol under Ultrasonic Radiation
-
The use of ultrasonic agitation in the base-catalysed autoxidation of alkylnitrobenzenes in polyethylene glycol phase-transfer systems changes reaction selectivity fron the usual dimeric products to the carboxylic acid.
- Neumann, Ronny,Sasson, Yoel
-
p. 616 - 617
(2007/10/02)
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- ANALYSIS OF THE PATHWAYS FOR CIS reversible reaction TRANS PHOTOISOMERIZATION OF 4-NITRO-,4,4 prime -DINITRO-, AND 4-NITRO-4 prime -METHOXYSTILBENE IN SOLUTION. XII.
-
Quantum yields for the direct trans yields cis ( PHI //t// yields //c) and cis yields trans ( PHI //c// yields //t) photoisomerization of 4-nitro-,4,4 prime -dinitro-, and 4-nitro-4 prime -methoxystilbene (NS, DNS, and NMS, respectively) were measured in solution at room temperature as a function of the concentration of quenchers (ferrocene, azulene, and oxygen). The results are in full agreement with a previously proposed reaction scheme for NMS, involving a triplet state as an intermediate in the trans yields cis photoisomerization and both triplet and excited singlet states in the cis yields trans photoisomerization. The branching ratios for decay of twisted configurations of the first excited singlet (**1p*) and the lowest triplet (**3p*) into the ground states and the yields for intersystem crossing from the first excited trans and cis singlet configurations to the lowest triplet state ( PHI //i//s//c**t and PHI //i//s//c**c, respectively) were determined.
- Goerner
-
p. 1199 - 1208
(2007/10/02)
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- A HIGHLY EFFICIENT VERSION OF THE PALLADIUM-CATALYSED ARYLATION OF ALKENES WITH ARYL BROMIDES
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The palladium-catalysed arylation of alkenes with aryl bromides or iodides is shown to proceed in high yields at very low palladium concentration when carried out in a suitable strongly polar solvent with a carboxylate anion as base.The preferred combination is N,N-dimethylformamide with sodium acetate.The reaction is markedly dependent on the substituents in the aryl bromide, being favoured by electron-withdrawing groups.Turnover numbers up to 134,000 have been achieved.
- Spencer, Alwyn
-
p. 101 - 108
(2007/10/02)
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- RHODIUM ION CATALYZED DECOMPOSITION OF ARYLDIAZOALKANES
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Aryldiazomethanes are converted by rhodium(II)acetate and iodorhodium(III) tetraphenylporphyrin to cis- rather than trans-1,2-diarylethylenes.Secondary aryldiazoalkanes react with rhodium(II) acetate to give azines.
- Shankar, B.K. Ravi,Shechter, Harold
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p. 2277 - 2280
(2007/10/02)
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- REACTIONS OF ORGANIC ANIONS. PART C. PHASE-TRANSFER ALKYLATION OF C-H ACIDS ACTIVATED BY THE ISONITRILE FUNCTION. UNPRECENDENTED β-ELIMINATION OF THE ISONITRILE GROUP
-
Benzylation and nitrobenzylation reactions of isocyanides in a catalytic two-phase system and in some homolytic systems were studied.Elimination of the isocyanide group has been observed in the products obtained.
- Jawdosiuk, Mikolaj,Uminski, Maciej,Kmiotek-Skarzynska, Irena,Makasza, Mieczyslaw
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p. 1309 - 1320
(2007/10/02)
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- Pyrazolopyridines. The Preparation of 1-Protected-1H-pyrazolopyridines and Attempts to Remove the 1-Substituent. Some Reactions of 1-Benzyl-1H-pyrazolopyridine and its 7-Oxide
-
1-Protected-1H-pyrazolopyridines and -1H-pyrazolopyridin-6(7H)-ones have been obtained from 1-substituted-5-aminopyrazoles , and the removal of the protecting groups has been investigated.Cyclisation of 1-substituted-5-aminopyrazoles with ethyl acetoacetate under acidic conditions or of the β-aminopropionic acid derivative (19) under the same conditions gave only the 1H-pyrazolopyridin-6(7H)-one isomer .N-Oxidation of 1-benzyl-1H-pyrazolopyridine (4) gave the 7-oxide (21) which yielded (20) and the less usual β-substitution product (22) with acetic anhydride.Nitration of either (4) or (21) gave only substitution at the para-position of the 1-benzyl substituent, but bromination or chlorination gave substitution at the 3-position of the heterocycle.
- Dorgan, Roderick J.J.,Parrick, John,Hardy, Christopher R.
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p. 938 - 942
(2007/10/02)
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- New Olefin and Oxiran Syntheses from Carbonyl Compounds, and Diethyl Sodiophosphonate Anions and 1-Aminophosphonate Amino-anions
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Reaction of aromatic aldehydes, and phthalic and thiophthalic anhydrides, with diethyl sodiophosphonate (1) gives the trans-stilbenes (3), 3,3'-biphthalidylidene (30), and 3,3'-bis-(2-thiophthalidylidene) (33).Similar treatment of fluorenone (8) and xanthone (17) with (1) leads to 9,9'-bis(fluororenylidene) (9) and 9,10-dihydro-9-oxophenanthrene-10-spiro-9'-fluorene (10), and to 9,9'-bixanthenylidene (18) and 9,9'-bixanthenyl (19), respectively, but the reaction using anthrone (11) as a carbonyl reagent yields only anthraquinone (12) and anthracene (13).Similar treatment using N-methylisatoic anhydride (34) and N-methylisatin (36) produces NN'-dimethylisoindigo (35).Reaction of benzaldehyde and p-chlorobenzaldehyde with diethyl 1--cyclohexylphosphonate (40) gives mainly corresponding mixtures of trans- (41a,b) and cis-stilbene epoxides (42a,b), while similar treatment of p-nitrobenzaldehyde with (40) produces 4,4'-dinitrostilbene (3e).Reaction of (8) with (40), as well as with (1), gives (9) and (10).The mechanism of formation of these products is discussed.
- Minami, Toru,Matsuzaki, Narihide,Ohshiro, Yoshiki,Agawa, Toshio
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p. 1731 - 1738
(2007/10/02)
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- Proton-Transfer and Electron-Transfer Processes in Reaction of p-Nitrotoluene with Bases. A Spectrophotometric Study
-
The interaction of p-nitrotoluene (PNT) with a variety of basic systems has been studied spectrophotometrically.The bases employed, in decreasing order of base strength, were potassium hydride, dimsyl potassium, triphenylmethylpotassium, fluorenylpotassium, and potassium p-nitroanilide, while the solvents used were dimethyl sulfoxide, tetrahydrofuran, and dimethoxyethane, with 18-crown-6 ether present in the latter two cases.The major species produced in the reactions were p-nitrobenzyl anion (PNT-), p-nitrotoluene radical anion (PNT-.), and p,p'-dinitrostilbene radical anion (DNS-.).The principal processes in the PNT-base systems are believed to be (i) PNT + B- PNT- + BH; (ii) PNT + B- PNT-. + B.; (iii) PNT- + PNT PNT. + PNT-..DNS-. is formed through secondary processes via p,p'-dinitrobibenzyl.Discussion of process (i) is given in terms of the relative pKas of PNT and the respective BH species, while (ii) is analysed on the basis of the reduction potential of PNT and the oxidation potential of B-.For the case of the PNT/Ph3C- system, the electron-transfer process (ii) is kinetically preferred but this equilibrium is rapidly established.On the other hand the proton-transfer process (i) is greatly favored thermodynamically and is effectively irreversible; as a result the proton transfer predominates.This is in accord with observation of PNT- as the initially formed species in this system.The processes occurring in the other base systems are similarly analysed.The assignment of the absorption due to the p-nitrobenzyl anion is at variance with an earlier literature report deduced from examination of the PNT/t-BuOK/t-BuOH system.Electron-transfer and proton-transfer processes in the PNT/t-BuO- system are also discussed.
- Buncel, E.,Menon, B. C.
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p. 3499 - 3507
(2007/10/02)
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