Cobalt(II) catalyzed tosylation of alcohols with p-toluenesulfonic acid

Cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) has been found to catalyze the tosylation of both aliphatic and aromatic alcohols with p-toluenesulfonic acid (p-TsOH) in high yields in 1,2-dichloroethane under reflux (ca. 80 °C). In the case of aliphatic alcohols, secondary alcohols undergo tosylation chemoselectively in the presence of primary hydroxy groups.     

p-Toluenesulfonic acid mediated hydroarylation of cinnamic acids with anisoles and phenols under metal and solvent-free conditions

Hydroarylation of cinnamic acids with anisoles and phenols mediated by p-toluenesulfonic acid (p-TSA) under metal and solvent-free conditions gave 3-(4-methoxyphenyl)-3-phenylpropanoic acids and dihydrocoumarins, respectively, in high yields and excellent selectivity.     

Sensitive and selective electrochemical detection of artemisinin based on its reaction with p-aminophenylboronic acid

The electrochemical detection of artemisinin generally requires high oxidation potential or the use of complex electrode modification. We find that artemisinin can react with p-aminophenylboronic acid to produce easily electrochemically detectable aminophenol for the first time. By making use of the new reaction, we report an alternative method to detect artemisinin through the determination of p-aminophenol. The calibration curve for the determination of artemisinin is linear in the range of 2 μmol L⁻¹ to 200 μmol L⁻¹ with the detection limit of 0.8 μmol L⁻¹, which is more sensitive than other reported electrochemical methods. The relative standard deviation is 4.83% for the determination of 10 μM artemisinin. Because the oxidation potential of p-aminophenol is around 0 V, the present method is high selective. When 40 μM, 90 μM and 140 μM of artemisinin were spiked to compound naphthoquine phosphate tablet samples, the recoveries are 107.6%, 105.4% and 101.7%, respectively. This detection strategy is attractive for the detection of artemisinin and its derivatives. The finding that artemisinin can react with aromatic boronic acid has the potential to be exploited for the development of other sensors, such as fluorescence artemisinin sensors.     

p-Toluenesulfonic acid-promoted selective functionalization of unsymmetrical arylalkynes: a regioselective access to various arylketones and heterocycles

Regioselective hydration of a wide range of internal alkynes has been afforded in high to good yields by using PTSA in EtOH. The scope of the reaction of alkynes has been delineated. Arylaliphatic alkynes and diarylalkynes were regioselectively hydrated in good to excellent yields and short reaction times when the reaction was achieved under microwave irradiation. Moreover, diarylalkynes, arylenynes as well as diaryldiynes bearing a methoxy- or a thiomethyl substituent on the ortho position underwent a regioselective 5-endo-dig-cyclization to give a variety of 2-aryl- and 2-styrylbenzofuran or benzothiphene derivatives. We believe that, this new environmentally metal-free procedure combined to microwave irradiation would be in importance in the search of green laboratory-scale synthesis.     

Lanthanum(III) nitrate hexahydrate or p-toluenesulfonic acid catalyzed one-pot synthesis of 4(3H)-quinazolinones under solvent-free conditions

The one-pot synthesis of quinazolinone derivatives from the reaction of anthranilic acid, trialkyl orthoformate and amines in the presence of lanthanum(III) nitrate hexahydrate or p-toluenesulfonic acid has been carried out. The reaction occurred in a few minutes under solvent-free conditions and in excellent yields.     

An efficient and selective tosylation of alcohols with p-toluenesulfonic acid

Silica chloride has been found to be an efficient catalyst for facile tosylation of alcohols directly with p-toluenesulfonic acid in methylene chloride under reflux. The process is associated with selective tosylation of secondary alcohols over primary alcohols.     

Selective N-debenzylation of amides with p-TsOH

N-Benzylamides were debenzylated efficiently with 4 equiv. of p-TsOH in refluxing toluene. Good to quantitative yields of the desired primary amides were obtained within 2-4 h from a wide variety of N-2,4-dimethoxybenzylamides. N-4-Methoxylbenzyl amides and N-benzylamides were also debenzylated cleanly. In the case of N-2,4-dimethoxylbenzylamides, selective N-debenzylation was possible in the presence of N-Fmoc, N-t-BOC or N-trityl-protection. Protected amino acid amides survived these conditions without any detectable epimerization.     

Uptake of weathered p,p′-DDE by plant species effective at accumulating soil elements

Ten plant species previously shown to accumulate inorganic elements effectively from natural solids were grown under field conditions in p,p′-dichlorodiphenyldichloroethane (p,p′-DDE) contaminated soil. The plant species, which included rye, mustard, canola, vetch, pigeonpea, clover, peanut, and 3 cultivars of white lupin, represented both monocots and dicots, as well as two major families within the dicots: the Brassicaceae and the Fabaceae. The plants varied widely in their ability to phytoextract and translocate weathered p,p′-DDE. The percentage of contaminant phytoextracted ranged from 0.06% (white lupin) to 0.22% (clover, vetch), and the translocation factors (TF; contaminant concentration ratio of stems to roots) ranged from 0.04 (clover, white lupin) to 0.37 (canola). An inverse relationship exists between the amount of contaminant in the roots as measured by the root BCF (bioconcentration factor; dry weight contaminant concentration ratio of root to soil) and the TF. Duplicate mounds of each species were periodically amended with nitrogen (N), phosphorus (P), nitrogen and phosphorus together (N/P); a minus phosphorus treatment involved the addition of AlSO₄ to the soil prior to planting. The effect of nutrient regime on plant biomass, p,p′-DDE uptake and translocation, and inorganic element content varied greatly among the 10 plant species. For some species (rye, vetch, pigeonpea, clover, white lupin), reductions or non-significant changes in p,p′-DDE uptake were observed under the nutrient treatments and were not correlated with plant biomass effects. For mustard, canola, and peanut, the percentage of p,p′-DDE phytoextracted in the various treatments was more than doubled and was directly correlated with a two-fold increase in total plant biomass. Although it is generally assumed that fertilizer amendments will enhance the phytoremediation of organic and inorganic pollutants, the data here suggest that such effects are highly species specific and in some cases may actually decrease remediation potential.     

Rare earth metal triflates catalyzed electrophilic nitration using N2O5

A mild,efficient and eco-friendly process for the electrophilic nitration is described using N₂O₅ as a green nitrating agent in the presence of rare earth metal triflates[RE（OTf）₃]under mild conditions.     

Suzuki-Miyaura monocouplings of p-dibromobiphenyl and substituted p-dibromo(penta-p-phenylenes)

The mono/bis ratio for the Suzuki-Miyaura cross coupling of p-dibromobiphenyl and p-dibromo(penta-p-phenylenes) with arylboronic acids and esters has been studied. The coupling reaction is demonstrated to be highly selective for monoarylation when the substrate is a p-dibromooligoarene, while selective biarylation is obtained for p-diiodoterphenyl. The mono/bis coupling-ratio for these compounds was highly sensitive to the nature of the halogen involved, however steric hindrance or electronic characteristics of the boronic derivative did not affect the selectivity of the reaction. The reaction yields observed were higher at room temperature and when arylboronic pinacol esters were used. These reactions also offer a useful method for the preparation of asymmetrically substituted terphenyls and hexa-p-phenylenes, giving good yields.     

PhI- and polymer-supported PhI-catalyzed oxidative conversion of ketones and alcohols to α-tosyloxyketones with m-chloroperbenzoic acid and p-toluenesulfonic acid

Various ketones were converted to the corresponding α-tosyloxyketones with mCPBA and p-toluenesulfonic acid in the presence of a catalytic amount of iodobenzene. Moreover, secondary alcohols were directly converted to the corresponding α-tosyloxyketones using mCPBA and catalytic amounts of iodobenzene and potassium bromide, followed by treatment with p-toluenesulfonic acid in a one-pot manner. Poly(4-iodostyrene) could be also used as a recyclable catalyst for the same α-tosyloxylation of ketone     

Preparation of three terbium complexes with p-aminobenzoic acid and investigation of crystal structure influence on luminescence property

Three new rare earth p-aminobenzoic acid complexes, [Tb₂L₆(H₂O)₂]_n (1), [Tb₂L₆(H₂O)₄]·2H₂O (2) and [Tb(phen)₂L₂(H₂O)₂](phen)L·4H₂O (3) (HL: p-aminobenzoic acid; phen: 1, 10-phenanthroline), with different structural forms are reported in this paper. Complex 1 is a polymolecule with a two-dimensional plane structure. Compound 2 is a binuclear molecule, and 3 appears to be a mononuclear complex. The fluorescence intensity, the fluorescence life-time and emission quantum yield of 2, which has two coordination water molecules, is better than those of 1, which has only one coordination water molecule. This is an unusual phenomenon for general fluorescent rare earth complexes. The fluorescence performance of 3 is the most unsatisfactory among the three complexes. Their crystal structures show that the coordination mode of the ligand is an important factor influencing the luminescence properties of a fluorescent rare earth complex.     

Selective nitration of phenols using bismuth subnitrate/charcoal in the presence of trichloroisocyanuric acid under aprotic conditions

<正>A mild,efficient and regioselective method for the mononitration of phenolic compounds is described using bismuth subnitrate/ charcoal in the presence of trichloroisocyanuric acid in CH_2Cl_2 at room temperature.     

The first metal complex of p-nitrobenzoxasulfamate. Synthesis, spectral and structural characterization of triaquabis(p-nitrobenzoxasulfamato)copper(II) monohydrate

The local structure of molten LaCl₃ was investigated by X-ray absorption fine structure of the La K-edge. The nearest La³⁺-Cl⁻ distance and coordination number were 2.89±0.01 Å and 7.4±0.5 from the curve fitting of the first peak in the Fourier transform magnitude |FT|. The coordination number larger than 6 suggests that the local structure of molten LaCl₃ is not a simple octahedral coordination (LaCl₆)³⁻, but 7-fold (LaCl₇)⁴⁻ and/or 8-fold (LaCl₈)⁵⁻ complexes. The first La³⁺-La³⁺ distance, of which correlation was observed as a weak second peak in the |FT|, was evaluated to be 4.9 Å. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, in contrast with molten YCl₃ in which the edge-sharing connection of the 6-fold (YCl₆)³⁻ mainly exists.     

Coupling of butyl vinyl tellurides with metal acetylides catalyzed by nickel complexes

Z-Vinylic tellurides react with metal acetylides under nickel complexes catalysis to give Z-enynes and Z-enediynes in good yields.     

Sulfonylamidation of alkylbenzenes at benzylic position with p-toluenesulfonamide and 1,3-diiodo-5,5-dimethylhydantoin

Treatment of alkylbenzenes with p-toluenesulfonamide and 1,3-diiodo-5,5-dimethylhydantoin (DIH) in a small amount of carbon tetrachloride at 60 °C gave the corresponding α-p-toluenesulfonylamido)alkylbenzenes in good to moderate yields. The present reaction is a simple method for the α-sulfonylamidation of the benzylic position in alkylbenzenes.     

New soluble aromatic polyamides containing ether linkages and laterally attached p-terphenyls

Two series of new polyamides containing flexible ether linkages and laterally attached side rods (3a-i and 4a-i) were synthesized from 2^′,5^′-bis(4-aminophenoxy)-[1,1^′;4^′,1^″]terphenyl (1a) and 2^′,5^′-bis(4-amino-2-trifluoromethylphenoxy)-[1,1^′;4^′,1^″]terphenyl (1b), respectively, with various aromatic dicarboxylic acids by the direct phosphorylation polycondensation. The polymers were produced with high yields and moderate to high inherent viscosities (0.41-0.97 dl/g) that corresponded to weight-average molecular weights (by size exclusion chromatography) of 47,000-65,000. Except for some polyamides that derived from rigid diacids, the obtained polyamides were readily soluble in aprotic polar solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc), and could afford flexible and tough films via solvent casting. The polymer films cast from DMAc solutions possessed tensile strengths of 85-106 MPa and initial moduli of 1.82-2.96 GPa. These polyamides showed glass-transition temperatures (T_g) in the range of 206-263 °C (by DSC) and softening temperatures (T_s) in the range of 211-253 °C (by TMA). Decomposition temperatures (T_d) for 10% weight loss all occurred above 400 °C (by TGA) in both nitrogen and air atmospheres. The polyamides 4a-i derived from trifluoromethyl-substituted diamine 1b generally showed a higher solubility, T_g and T_s but lower thermal stability as compared to the analogous polyamides 3a-i based on diamine 1a.     

Ab initio study of the mechanism of the formation of p-rosolic acid from trifluoromethoxybenzene under HF/Lewis acid conditions

The mechanism of the formation of p-rosolic acid from trifluoromethoxybenzene under HF/Lewis acid conditions was studied using ab initio methods. A series of cationic intermediates is initiated by the expulsion of a fluorine atom of trifluoromethoxybenzene with anomeric assistance of the trifluoromethoxy oxygen. The resulting difluorocarbonium ion is attacked by a second trifluoromethoxybenzene to generate the first carbon-carbon bond on what will be the central carbon of p-rosolic acid. Elimination of phenol results in the formation of cationic intermediate 4 which is susceptible to carbon-alkylation by the same phenol to form the second carbon-carbon bond. Attack on subsequent difluorocarbonium ions by trifluoromethoxybenzene strips trifluoromethyl groups from the downstream intermediates, eventually leading to p-rosolic acid, and continues the generation of 4, each of which initiate a fresh mechanistic series toward another p-rosolic acid molecule.     

Reductive alkylation of p-benzoquinone using mixed organoboranes

Mixed organoboranes based on diphenyl- or dimethylalkylboranes transfer the alkyl group in the reductive alkylation of p-benzoquinone to form the alkylhydroquinones in very high yields. The auxiliary groups do not transfer or have a low migratory aptitude. Primary and secondary alkyl groups are transferred with retention of regio- and stereochemistry to the hydroquinone. O-Alkylation is the major product with tertiary and secondary groups with steric bulk in proximity to the site of attachment. The presence of metal salts, such as magnesium, results in reduction to the unsubstituted hydroquinone. This reaction makes the first practical route to alkylhydroquinones via organoboranes.     

Regioselective ipso formylation of p-tert-butylcalix[4]arene

A convenient procedure for direct introduction of one formyl group into p-tert-butylcalix[4]arenes through ipso substitution is described.