- Relationship between molecular association and re-entrant phenomena in polar calamitic liquid crystals
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The relationship between molecular association and re-entrant phase behavior in polar calamitic liquid crystals has been explored in two families of materials: the 4'-alkoxy-4-cyanobiphenyls (6OCB and 8OCB) and the 4'-alkoxy-4-nitrobiphenyls. Although re-entrant nematic phase behavior has previously been observed in the phase diagram of 6OCB/8OCB, this is not observed in mixtures of the analogous nitro materials. As there is no stabilization of the smectic A phase in mixture studies, it was conjectured that the degree of association for the nitro systems is greater than that for the cyano analogues. This hypothesis was tested by using measured dielectric anisotropies and computed molecular properties to obtain a value of the Kirkwood factor, g, which describes the degree of association of dipoles in a liquid. These computed values of g confirm that the degree of association for nitro materials is greater than that for cyano and offer a useful method for quantifying molecular association in systems exhibiting a re-entrant polymorphism.
- Mandle, Richard J.,Cowling, Stephen J.,Goodby, John W.,Sage, Ian,Colclough, M. Eamon
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- Effect of the functional diamine structure on the properties of a polyimide liquid crystal alignment film
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A novel functional diamine containing triphenylamine moiety and biphenyl as well as a long alkyl chain, 4-dodecyloxy-biphenyl-4′,4′′-diaminotriphenylamine (DBDTA), was synthesized and characterized. A series of polyimides (PIs) were copolymerized from DBDTA, 3,3′-dimethyl-4,4′-methylenedianiline (DMMDA) and 4,4′-oxydiphthalic anhydride (ODPA) via a one-step method. The chemical structures of the diamine and PIs were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR). Properties such as the solubility, rubbing resistance, thermal stability and pre-tilt angle of the PIs were investigated. Furthermore, the results were compared with the PIs-BZA derived from 4-dodecyloxy-biphenyl-3′,5′-diaminobenzoate (DBPDA). The PIs-TPA derived from DBDTA exhibited better transparency and thermal stability than the PIs-BZA from DBPDA. When the content of functional diamines was only 10%, the PI1-TPA derived from DBDTA displayed better solubility than the PI1-BZA from DBPDA. In addition, all PIs could induce uniform vertical alignment of the liquid crystals (LCs) before and after the rubbing process, but PI1-BZA only induced parallel alignment of the LCs after rubbing process. It is suggested that the PI1-TPA film is more resistant to the rubbing process than PI1-BZA. This journal is
- Liu, Ming,Zheng, Xinguo,Gong, Shiming,Liu, Lulu,Sun, Zhen,Shao, Leishan,Wang, Yinghan
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- Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters
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The amide C-N cleavage has drawn a broad interest in synthetic chemistry, biological process and pharmaceutical industry. Transition-metal, luxury ligand or excess base were always vital to the transformation. Here, we developed a transition-metal-free hydrogen-bond-assisted esterification of amides with only catalytic amount of base. The proposed crucial role of hydrogen bonding for assisting esterification was supported by control experiments, density functional theory (DFT) calculations and kinetic studies. Besides broad substrate scopes and excellent functional groups tolerance, this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C-N bonds for organic synthesis and pharmaceutical industry. [Figure not available: see fulltext.]
- Huang, Changyu,Li, Jinpeng,Wang, Jiaquan,Zheng, Qingshu,Li, Zhenhua,Tu, Tao
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- Dual aminoquinolate diarylboron and nickel catalysed metallaphotoredox platform for carbon-oxygen bond construction
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Herein, aminoquinolate diarylboron complexes are utilized as photocatalysts in dual Ni/photoredox catalyzed carbon-oxygen construction reactions. Via this unified metallaphotoredox platform, diverse (hetero)aryl halides can be conveniently coupled with acids, alcohols and water. This method features operational simplicity, broad substrate scope and good compatibility with functional groups. This journal is
- Day, Craig,Jia, Xin,Wei, Lanfeng,Xu, Liang,Zu, Weisai
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supporting information
p. 8273 - 8276
(2020/08/17)
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- Ligand-Controlled C?O Bond Coupling of Carboxylic Acids and Aryl Iodides: Experimental and Computational Insights
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Palladium-catalyzed cross-coupling reactions between carboxylic acids and aryl halides have several possible competitive pathways. Decarboxylative C?C bond coupling and C?H arylation are well established in the literature. However, direct C?O bond coupling between carboxylic acids and aryl halides has received little success. In this report, we describe a protocol for exclusive C?O bond formation, enabled by a bidentate N,N-ligand such as 1,10-phenanthroline. The reaction is general for a broad range of carboxylic acids and iodoarenes. Experimental evidence and computational results suggest a high energy barrier for the alternative pathway of decarboxylative carbon-carbon bond coupling. (Figure presented.).
- Li, Li,Song, Feifei,Zhong, Xiumei,Wu, Yun-Dong,Zhang, Xinhao,Chen, Jiean,Huang, Yong
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supporting information
p. 126 - 132
(2019/11/28)
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- Visible light-mediated transition metal-free esterification of amides with boronic acids
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A novel strategy for visible light-mediated esterification of amides with boronic acids in air has been described. This method is characterized by mild reaction conditions and low cost owing to no need of any catalyst, which implies high potential utility in late-stage functionalization of amide drugs and materials.
- Ding, Hao,Qi, Wan-Ying,Zhen, Jing-Song,Ding, Qiuping,Luo, Yong
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supporting information
(2020/10/02)
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- Enol Ester Intermediate Induced Metal-Free Oxidative Coupling of Carboxylic Acids and Arylboronic Acids
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A facile, efficient and environmentally friendly methodology for the preparation of phenolic esters is realized via metal-free coupling of carboxylic acids and arylboronic acids. This sequential one pot reaction, employing methyl propiolate as an activating reagent, proceeds through the formation of enol ester intermediate, followed by a nucleophilic attack on the C-O bond under the oxidation of hydrogen peroxide. These studies display that enol esters, despite previously being overlooked as synthetic intermediates, would be the valuable building blocks for developing carbon–carbon and carbon–heteroatom bond-forming reactions.
- Xu, Xianjun,Feng, Huangdi,Li, Huiqiong,Huang, Liliang
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p. 3921 - 3928
(2019/06/24)
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- Oxime palladacycle in PEG as a highly efficient and recyclable catalytic system for phenoxycarbonylation of aryl iodides with phenols
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In this report, we have developed a sustainable protocol for the synthesis of aromatic esters by a carbonylative method using di-μ-chlorobis [5-hydroxy-2-[1-(hydroxyimino-?N) ethyl] phenyl-?C] palladium (II) dimer (1) catalyst in PEG-400 as a greener and recyclable solvent. The reaction is carried out at room temperature using CO in a balloon. Good to excellent yield of various esters can be synthesize using this protocol. Direct insertion of CO moiety leads to the high atom and step economy. Compared to previous protocol this phosphine free approach for the synthesis of aromatic esters provides high Turnover Number (TON) and Turnover Frequency (TOF). Developed approach has an alternative route for use of conventional palladium precursor with high conversion and selectivity. The catalyst system and product can easily be separated using diethyl ether as a solvent. The Pd/PEG-400 system could be reused up to a fifth consecutive cycle without any loss of its activity and selectivity.
- Gaikwad, Vinayak V.,Bhanage, Bhalchandra M.
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- Selectivity in the photo-fries rearrangement of some aryl benzoates in green and sustainable media. Preparative and mechanistic studies
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Irradiation of a series of p-substituted aryl benzoates under N2 atmosphere in homogeneous and micellar media was investigated by means of steady-state condition and of time-resolved spectroscopy. A notable selectivity in favor of the 2-hydroxybenzophenone derivatives was observed in micellar media. The benzophenone derivatives were the main photoproduct. On the other hand, in homogeneous media (cyclohexane, acetonitrile, and methanol) the observed product distribution was entirely different, viz. substituted 2-hydroxybenzophenones, p-substituted phenols, benzyl and benzoic acid were found. The binding constants in the surfactant were also measured and NOESY experiments showed that the aryl benzoates were located in the hydrophobic core of the micelle. Laser flash photolysis experiments led to the characterization of both p-substituted phenoxy radical and substituted 2-benzoylcyclohexadienone transients in homogeneous and micellar environment.
- Siano, Gastón,Bonesi, Sergio M.,Crespi, Stefano,Mella, Mariella
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p. 4338 - 4352
(2019/05/01)
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- Rhodium-catalysed aryloxycarbonylation of iodo-aromatics by 4-substituted phenols with carbon monoxide or paraformaldehyde
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Rhodium-catalysed phenoxycarbonylation of aryl iodides were carried out under carbon-monoxide atmosphere and in the absence of CO, using paraformaldehyde as an alternative surrogate for carbonylation reactions. Both strategies proved to be efficient for the synthesis of the corresponding phenyl esters. High pressure reactions provided the ester products with good selectivity, however lower activity was achieved compared to palladium containing systems. Using paraformaldehyde as carbon-monoxide source special reaction conditions are required, thus dramatic changes observed during optimisation reactions. Using in situ generated Rh-diphosphine catalyst systems, remarkable influence of ligand structure and solvent composition was observed on the activity and chemoselectivity. The substrate scope and the substituent effect were also investigated.
- Seni, Anas Abu,Kollár, László,Mika, László T.,Pongrácz, Péter
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- Pd/C catalyzed phenoxycarbonylation using: N -formylsaccharin as a CO surrogate in propylene carbonate, a sustainable solvent
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This work reports the first Pd/C catalyzed phenoxycarbonylation of aryl iodides using N-formylsaccharin as a CO surrogate. Advantageously, the reaction could be carried out in propylene carbonate, an environmentally benign and sustainable polar aprotic solvent under CO surrogacy. Using N-formylsaccharin as a CO surrogate allows the usage of cheaper and readily available phenols as the coupling partner. A range of phenyl esters could be synthesized under mild, co-catalyst free, ligand free and additive free conditions, including multi-substituted novel phenyl esters. The Pd/C catalyst could be recycled up to four times with only a slight loss in activity. The reaction could be scaled up to gram scale synthesis.
- Gautam, Prashant,Kathe, Prasad,Bhanage, Bhalchandra M.
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supporting information
p. 823 - 830
(2017/08/15)
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- Solid-Phase Benzoylation of Phenols and Alcohols in Microwave Reactor: An Ecofriendly Protocol
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An efficient solid-phase benzoylation of phenols and alcohols was developed under microwave irradiation. A stoichiometric amount of benzoyl chloride was sufficient to carry out the reaction. This benzoylation features short reaction time, good yields, and easy workup procedures. Furthermore, the scope of the reaction was extended to prepare 3,5-dinitrobenzoyl derivatives of alcohols.
- Chakraborty, Suchandra,Saha, Ahana,Basu, Kaushik,Saha, Chandan
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supporting information
p. 2331 - 2343
(2015/10/12)
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- Metal-free synthesis of aryl esters by coupling aryl carboxylic acids and aryl boronic acids
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A facile synthesis of aryl esters is developed by coupling aryl carboxylic acids and aryl boronic acids in the presence of PhI(OAc)2 and carbonyl diimidazole. A wide range of functional groups were tolerant to the metal-free reaction condition that led to the desired products in good yields.
- Ruso, Jayaraman Sembian,Rajendiran, Nagappan,Kumaran, Rajendran Senthil
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supporting information
p. 2345 - 2347
(2014/05/06)
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- Synthesis and mesomorphic behavior of calamitic liquid crystals with a biphenyl moiety
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A new mesogenic homologous series having a biphenyl moiety has been synthesized by condensing 4-hydroxy-4′-nitrobiphenyl- and methoxy-substituted 4-n-alkoxy cinnamoyl chlorides, and their liquid crystalline properties have been studied. All the members of the series are enantiotropic liquid crystals. The methyl to n-pentyl derivatives exhibit both Smectic A (SmA) and Nematic (N) phases; the higher members, starting with the n-hexyl derivative show only a SmA phase. The plot of transition temperatures versus number of carbon atoms in the alkoxy chain exhibits zig-zag pattern for Sm-N and NIsotropic (Iso) transition temperature curves. The average thermal stability is compared with other related homologous series. The introduction of polar nitro group increases significant intermolecular force of attraction which stabilizes the molecular orientation. This results into the increase in the thermal stability of the system.
- Tandel,Patel, Nilesh K.
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p. 114 - 125
(2014/07/07)
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- Trichlorophenyl formate: Highly reactive and easily accessible crystalline CO surrogate for palladium-catalyzed carbonylation of aryl/alkenyl halides and triflates
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The high utility of 2,4,6-trichlorophenyl formate, a highly reactive and easily accessible crystalline CO surrogate, is demonstrated. The decarbonylation with NEt3 to generate CO proceeded rapidly at rt, thereby allowing external-CO-free Pd-catalyzed carbonylation of aryl/alkenyl halides and triflates. The high reactivity of the CO surrogate enabled carbonylation at rt and significantly reduced the quantities of formate to near-stoichiometric levels. The obtained trichlorophenyl esters can be readily converted to a variety of carboxylic acid derivatives in high yields.
- Ueda, Tsuyoshi,Konishi, Hideyuki,Manabe, Kei
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supporting information
p. 5370 - 5373,4
(2012/12/12)
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- Palladium-catalyzed aerobic oxidative coupling of acyl chlorides with arylboronic acids
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The first example of a palladium-catalyzed aerobic oxidative coupling of acyl chlorides with arylboronic acids has been developed, leading to a wide range of aryl benzoates in good to excellent yields. This catalytic system shows broad functional group tolerance. Preliminary mechanistic experiments using deuterium labeling showed that the oxygen atom was derived from dioxygen. Copyright
- Chen, Jiuxi,Peng, Yong,Liu, Miaochang,Ding, Jinchang,Su, Weike,Wu, Huayue
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supporting information
p. 2117 - 2122
(2012/11/07)
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- Equilibrium shift in the rhodium-catalyzed acyl transfer reactions
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Rhodium/phosphine complexes catalyze equilibrium acyl transfer reactions between acid fluorides, aryl esters, acylphosphine sulfides, and thioesters. The use of appropriate co-substrates to accept heteroatom groups shifted the equilibrium to desired products. Acylphosphine sulfides and aryl esters were converted to acid fluorides using benzoylpentafluorobenzene as the fluoride donor, and the fluorination reaction of thioesters employed (4-tolylthio) pentafluorobenzene. Acid fluorides were converted into acylphosphine sulfides and thioesters using diphosphine disulfides and disulfides/triphenylphosphine, respectively. Aryl esters were obtained from acid fluorides and phenols in the presence of triphenylsilane. Aryl esters, acylphosphine sulfides, and thioesters were also interconverted in the presence of rhodium complexes. These rhodium-catalyzed acyl transfer reactions proceeded under neutral conditions without using acid or base. The involvement of acyl rhodium intermediates in these reactions was suggested by the carbothiolation reaction of thioesters and alkynes.
- Arisawa, Mieko,Igarashi, Yui,Kobayashi, Haruki,Yamada, Toru,Bando, Kentaro,Ichikawa, Takuya,Yamaguchi, Masahiko
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supporting information; experimental part
p. 7846 - 7859
(2011/10/12)
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- Radical OfC transposition: A metal-free process for conversion of phenols into benzoates and benzamides
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We report a metal-free procedure for transformation of phenols into esters and amides of benzoic acids via a new radical cascade. Diaryl thiocarbonates and thiocarbamates, available in a single high-yielding step from phenols, selectively add silyl radicals at the sulfur atom of the CdS moiety. This addition step, analogous to the first step of the Barton-McCombie reaction, produces a carbon radical which undergoes 1,2 OfC transposition through an O-neophyl rearrangement. The usually unfavorable equilibrium in the reversible rearrangement step is shifted forward via a highly exothermic C-S bond scission in the O-centered radical, which furnishes the final benzoic ester or benzamide product. The metal-free preparation of benzoic acid derivatives from phenols provides a potentially useful alternative to metal-catalyzed carbonylation of aryl triflates.
- Baroudi, Abdulkader,Alicea, Jeremiah,Flack, Phillip,Kirincich, Jason,Alabugin, Igor V.
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experimental part
p. 1521 - 1537
(2011/06/11)
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- Radical 1,2-o→c transposition for conversion of phenols into benzoates by o-neophyl rearrangement/fragmentation cascade
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Figure Presented Radical merry-go-round! Diaryl thiocarbonates, available in a single step from phenols, can be directly transformed into benzoates by a new radical cascade that transposes O and C atoms at the aromatic core. The cascade bypasses the common Barton McCombie fragmentation in favor of the usually unfavorable O-neophyl rearrangement, which is rendered irreversible and efficient by a highly exothermic C-S bond scission in the O-centered radical (see scheme; FG = functional group).
- Baroudi, Abdulkader,Alicea, Jeremiah,Alabugin, Igor Y.
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experimental part
p. 7683 - 7687
(2010/08/22)
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- Zinc oxide (ZnO) as a new, highly efficient, and reusable catalyst for acylation of alcohols, phenols and amines under solvent free conditions
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Zinc oxide (ZnO) is a highly efficient catalyst for the acylation of a variety of alcohols, phenols and amines with acid chlorides or acid anhydrides under solvent free conditions. Primary, secondary, tertiary, allylic and benzylic alcohols, diols and phenols with electron donating or withdrawing substituents can be easily acylated in good to excellent yield.
- Hosseini Sarvari, Mona,Sharghi, Hashem
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p. 10903 - 10907
(2007/10/03)
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- Cesium fluoride-Celite: A solid base for efficient syntheses of aromatic esters and ethers
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Coupling reactions of a number of aromatic and heteroaromatic phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride-Celite are described, demonstrating that this reagent provides an efficient, convenient and practical method for the syntheses of aromatic esters and ethers.
- Shah, Syed Tasadaque Ali,Khan, Khalid Mohammed,Hussain, Hidayat,Anwar, Muhammad Usman,Fecker, Miriam,Voelter, Wolfgang
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p. 6652 - 6656
(2007/10/03)
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- An efficient approach towards syntheses of ethers and esters using CsF-Celite as a solid base
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The coupling reactions of a number of alcohols and phenols with alkyl, acyl or benzoyl halides in acetonitrile with cesium fluoride-Celite are described. It has been found that CsF-Celite combinations provide an efficient, convenient and practical method for syntheses of both, ethers and esters.
- Shah, Syed Tasadaque A,Khan, Khalid M,Heinrich, Angelica M,Choudhary, M.Iqbal,Voelter
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p. 8603 - 8606
(2007/10/03)
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- Syntheses and photophysical properties of some 4-arylpyridinium salts
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A number of 4-arylpyridines, many methoxy substituted, were prepared by an efficient two-step method involving aryl Grignard addition to 1-methyl-4-piperidone and direct aromatization of the resulting 4-aryl-4-piperidinols. The pyridines were N-alkylated to give sulfonate salts desired for their fluorescent properties. Study of selected compounds as laser dyes revealed several structures to be efficient dyes lasing in the 530-550 nm range. Two new diazaquaterphenyls were prepared and were quaternized. These salts exhibited intense fluorescence in the 420-450 nm range, but would not lase. A phenolic azaterphenyl suitably substituted for excited state intramolecular proton transfer (ESIPT) did not fluoresce at all.
- Kelley,Ansu,Budisusetyo,Ghiorghis,Qin,Kauffman
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- DEVELOPMENT OF POLYMERIC NONLINEAR OPTICAL MATERIALS
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The molecular structural characteristics which give rise to large optical nonlinearities have been delineated.This has been accomplished by several key steps and has led to the development of a structural algorithm for the design of β molecules with high
- Leslie, Thomas M.,Demartino, Ronald N.,Choe, E. Won,Khanarian, Garo,Haas, David,et al.
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p. 451 - 478
(2007/10/02)
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- Nucleophilic Displacements of N-Aryl and Heteroaryl Groups. Part 1. Pyrylium-mediated Transformation of Anilines into Phenols
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Aromatic amines with 2,4-diphenyl-5,6,7,8-tetrahydrochromenylium trifluoromethanesulphonate (5) gave the corresponding pyridinium salts (6; R = aryl) which were converted by base into the anhydrobases (7).Benzoyl chloride converted (7) into the new pyridinium anhydrobases (9).These anhydrobases (9) rearrangement at 150 deg C into the isomeric phenol enol ethers (10) which were readily hydrolysed to yield the corresponding phenols.The mechanistic and synthetic significance of the results are assessed.
- Katritzky, Alan R.,Langthorne, Ronald T.,Muathin, Hussni A.,Patel, Ranjian C.
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p. 2601 - 2604
(2007/10/02)
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