Acid In Dichloromethane Research Articles

Lycopene (Z) – isomers enrichment and separation

Summary(All‐E)‐ Lycopene undergoes geometrical isomerisation into (Z)‐lycopene isomers with thermal treatment. Influence of three isomerisation methods including ethyl acetate reflux, microwave‐assisted reflux and ultrasound/microwave‐assisted reflux, and isolation of (all‐E)‐lycopene from other carotenoids and (Z) lycopene isomers through selective inclusion by deoxycholic acid (3α, 12α dihydroxy‐5βcolan‐24‐oic‐acid, DCA) were investigated. The results showed that microwave and ultrasound/microwave‐assisted reflux were not significantly different at P < 0.05, but both were significantly different (P < 0.05) over refluxing in ethyl acetate, proportion of (Z)‐lycopene isomers reached 54% after refluxing for 5 h. Heterogeneous mixture of isomerised tomato oleoresin containing 54% (Z)‐lycopene isomers and 40% (all‐E)‐lycopene and deoxycholic acid in dichloromethane was incubated at 25 °C for 2 h. Then, the mixture was filtered and from the filtrate 96.6% (Z)‐isomers enriched lycopene was obtained. The processes can be used in the production of enriched (Z)‐lycopene isomers for food supplements and functional food industry as a natural bioactive ingredient.

5-Hydroxypent-2-enenitriles as precursors toward dihydropyranones, dienenitriles and functionalized naphthalenes

5-Hydroxypent-2-enenitriles were found to be precursors toward several classes of compounds with synthetic and biological interests. To be specific, upon treatment with sulfuric acid in dichloromethane and depending on the configuration of the C–C double bond and the nature of substituents attached on the C–C double bond, 5-hydroxypent-2-enenitriles could afford 5,6-dihydropyran-2-ones, 2,4-dienenitriles, or functionalized naphthalenes through intramolecular Pinner reaction, β-elimination or intramolecular Friedel–Crafts reaction, respectively.

Method of obtaining 6-ethoxycarbonylmethyl-sulfinyl-2,3-dihydroxy-1,2,3,4-tetrahydropyridine

Oxidation of the sulfur atom in methyl 4-(2-chlorophenyl)-5-cyano-6-ethoxycarbonylmethylsulfanyl-2-methyl-1,4-dihydropyridine-3-carboxylate with m-chloroperbenzoic acid in dichloromethane gave methyl 4-(2-chlorophenyl)-5-cyano-6-ethoxycarbonylmethylsulfinyl-2,3-dihydroxy-2-methyl-1,2,3,4-tetra-hydropyridine-3-carboxylate. The structure of the compound obtained was identified by 1H NMR spectroscopy and by X-ray structural analysis.

Protonation of metal–metal bonds in coordinatively unsaturated diruthenium cores

The addition reaction of a proton towards the coordinatively unsaturated diruthenium complexes [Ru2(CO)4(μ-H)(μ-PtBu2)(μ-P^P)] (RuRu) (P^P=Ph2PC(CH2)PPh2, dppen, 1b; P^P=Ph2PN(H)PPh2, dppa, 1c; P^P=Ph2PN(Ph)PPh2, dpppha, 1d) has been investigated. Thus the species 1b–d exhibit a high metal basicity and react with protons from tetrafluoroboric acid in dichloromethane to afford the corresponding oxidative addition products [Ru2(CO)4(μ-H)2(μ-PtBu2)(μ-P^P)]BF4 (2b–d) in good yields. During these reactions a shortening of the metal–metal bond in each case was observed as confirmed by X-ray diffraction studies.

Elaboration of the carbocyclic ring systems in plumarellide and rameswaralide using a coordinated intramolecular cycloaddition approach, based on a common biosynthesis model

Treatment of the furanbutenolide 18a with trifluoroacetic acid in dichloromethane results in hydrolysis and rearrangement leading to the cycloheptene ring-containing system 19a found in rameswaralide (5). Similar treatment of the diastereoisomeric furanbutenolide 17 produces the cyclohexene ring-containing system 23 present in plumarellide (1), together with the C-7 epimer 24 of 19a. The acid-catalysed conversions 18a→19a and 17→23 are rationalised implicating [6+4] and [4+2] cycloaddition pathways and/or two-step carbocation cyclisation sequences.

1,3,5-Tris(hydrogensulfato) Benzene: A New and Efficient Catalyst for Synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) Derivatives

1,3,5-Tris(hydrogensulfato) benzene (THSB) was easily prepared by the reaction between phloroglucinol and chlorosulfonic acid in dichloromethane at room temperature. This compound was then used as an efficient catalyst for the synthesis of 4,4′-(arylmethylene)bis(1 H -pyrazol-5-ols) through the condensation reactions of 1-phenyl-3-methylpyrazol-5-one with several different aromatic aldehydes in ethanol at 75 °C. The present methodology offers several advantages over existing methodologies, such as excellent yields, simple procedure, easy work-up and ecofriendly reaction conditions. 1,3,5-Tris(hydrogensulfato) benzene has been used as an new and efficient catalyst for the one-pot synthesis of 4,4′-(arylmethylene)bis(1 H -pyrazol-5-ols) through the condensation reactions of 1-phenyl-3-methylpyrazol-5-one with a variety of different aromatic aldehydes in ethanol at 75 °C.

Synthesis and application of Nα‐Fmoc‐Nπ‐4‐methoxybenzyloxymethylhistidine in solid phase peptide synthesis

The 4-methoxybenzyloxymethyl (MBom) group was introduced at the Nπ-position of the histidine (His) residue by using a regioselective procedure, and its utility was examined under standard conditions used for the conventional and the microwave (MW)-assisted solid phase peptide synthesis (SPPS) with 9-fluorenylmethyoxycarbonyl (Fmoc) chemistry. The Nπ-MBom group fulfilling the requirements for the Fmoc strategy was found to prevent side-chain-induced racemization during incorporation of the His residue even in the case of MW-assisted SPPS performed at a high temperature. In particular, the MBom group proved to be a suitable protecting group for the convergent synthesis because it remains attached to the imidazole ring during detachment of the protected His-containing peptide segments from acid-sensitive linkers by treatment with a weak acid such as 1% trifluoroacetic acid in dichloromethane. We also demonstrated the facile synthesis of Fmoc-His(π-MBom)-OH with the aid of purification procedure by crystallization to effectively remove the undesired τ-isomer without resorting to silica gel column chromatography. This means that the present synthetic procedure can be used for large-scale production without any obstacles.

Some Transformative Reactions of Odollactone

Oxidative rearrangement of odollactone has been carried out with hydrogen peroxide containing p-toluene sulphonic acid in dichloromethane. The products obtained were characterised by chemical transformation using selenium dioxide in acetic acid, sodium dichromate in acetic acid and Li in ethylenediamine followed by spectral analysis. The in- troduction of olefinic double bond at AB-ring juncture influences the cleavage of γ-lactone ring to the diol in contrast to the parent odollactone that gives the carboxylic acid.

Synthesis and reactions of new 1,2- and 1,3-cyclopentadienyl disubstituted cobalt sandwich compounds (η5-C5H3R2)Co(η4-C4Ph4) (R[dbnd]CH2OH, CHO, C[tbnd]CH, CH2N3, CH2NH2, CH2OAc, CH[dbnd]NPh)

Synthesis and characterization of a series of 1,3- and 1,2-cyclopentadienyl disubstituted derivatives of η5-CpCo(η4-C4Ph4) has been described. The 1,3- and 1,2-cyclopentadienyl diester derived cobalt sandwich compounds {η5-C5H3[C(O)OMe]2}Co(η4-C4Ph4) were prepared by literature procedure and were separated by column chromatography. The reduction of these diester derivatives using LiAlH4 gave the bis(hydroxymethyl) derivatives, [1,3-η5-C5H3(CH2OH)2] Co(η4-C4Ph4) 1 and [1,2-η5-C5H3(CH2OH)2]Co(η4-C4Ph4) 2 which were oxidized to the dialdehydes [1,3-η5-C5H3(CHO)2]Co(η4-C4Ph4) 3 and [1,2-η5-C5H3(CHO)2]Co(η4-C4Ph4) 4 by using tetrapropylammonium perruthenate along with N-methyl morpholine oxide. Reaction of the dialdehydes with (chloromethyl)triphenylphosphonium chloride/n-BuLi followed by elimination of HCl using n-BuLi resulted in the 1,2- and 1,3-cyclopentadienyl disubstituted dialkynes [1,3-η5-C5H3(CCH)2]Co(η4-C4Ph4) 5 and [1,2-η5-C5H3(CCH)2]Co(η4-C4Ph4) 6. The reactions of 1 and 2 with NaN3 in acetic acid resulted in the bis(azidomethyl) derivatives [1,3-η5-C5H3(CH2N3)2]Co(η4-C4Ph4) 7 and [1,2-η5-C5H3(CH2N3)2]Co(η4-C4Ph4) 8. Heating of bis(hydroxymethyl) compounds 1 and 2 in acetic acid at 85–90 °C resulted in the formation of bis(2-acetoxymethyl) derivatives [1,3-η5-C5H3(CH2OAc)2]Co(η4-C4Ph4) 9 and [1,2-η5-C5H3(CH2OAc)2]Co(η4-C4Ph4) 10. The reactions of 1 and 2 with thiophenol in the presence of trifluoroacetic acid in dichloromethane gave bis(phenylmethyl thioether) derivatives 11 [1,3-η5-C5H3(CH2SPh)2]Co(η4-C4Ph4) and [1,2-η5-C5H3(CH2SPh)2]Co(η4-C4Ph4) 12. The click reaction of the 1,2-dialkyne 6 with benzyl azide resulted in the 1,2-bis(triazole) derivative 13. The 1,3-diazide 8 was reduced to bis(aminomethyl) derivative [1,3-η5-C5H3(CH2NH2)2]Co(η4-C4Ph4) 14. Condensation of the 1,3-dialdehyde 3 with aniline resulted in the 1,3-bis(phenylimino) derivative 15. All the new compounds synthesized in this study were characterized by 1H and 13C NMR, FT-IR, HRMS, CHN analysis. The compounds 2–6, 8 and 10 have also been structurally characterized by single crystal X-ray diffraction analysis.

ChemInform Abstract: A New Method for the Mononitration of Phenol Derivatives by Poly(4‐vinylpyridinium nitrate) and Silica Sulfuric Acid under Mild Conditions.

Abstract This procedure works efficiently for high selective mono nitration of phenol and substituted phenol to corresponding nitro compounds in moderate to high yield using poly(4-vinylpyridinium nitrate) and silica sulfuric acid in dichloromethane at room temperature.

Preliminary Analysis of Several Attractants and Spatial Repellents for the Mosquito, Aedesalbopictususing an Olfactometer

Mosquito attractants and spatial repellents hold great promise in controlling mosquito pests. In assessing the effectiveness of mosquito attractants and repellents, a good olfactometer system, and optimized testing conditions, are essential. In this research, we demonstrated the usefulness of an olfactometer system, and optimized testing conditions for Aedes albopictus (Diptera: Culicidae). We found no significant difference in the biting activity of the insect between 8:00 and 22:00. Furthermore, 5–10 day old mosquitoes were relatively strongly attracted, with bloodsucking rate 75.8%. The random capture rate (entered trap in absence of odor) was less than 20% for the 20–40 tested insects. Capture rates and systematic errors increased as the number of testing insects increased. Wind speed affected the capture rate significantly, whereas variations in temperature between 25–28°C did not result in significant difference. The wind speed of 0.2 m/s exhibited a higher capture rate, which was significantly different from those at either 0.1 m/s or 0.4 m/s (P < 0.05). At the wind speed of 0.2 m/s, time durations within the first 8 minutes correlated positively with capture rates (r2 = 0.997), but further increase in time duration to 10 minutes did not result in further increase in capture rates. One percent of L-lactic acid in dichloromethane resulted in a consistently higher capture rate (43.8%) than that from a human odor (31.2%). Under our testing conditions, eugenol, anisaldehyde, geraniol, citronellal, citral, and linalool all exhibited some inhibition effect on mosquitoes to successfully trace human odor or 1% of L-lactic acid in dichloromethane. The results of these two tests indicate that the L-lactic acid/dichloromethane mixture may be used as an effective attractant to evaluate the effect of possible spatial repellents on Ae. albopictus.

Solubility of Stearic Acid in Ethanol, 1-Propanol, 2-Propanol, L-Butanol, Acetone, Methylene Chloride, Ethyl Acetate and 95% Ethanol from (293 to 315) K

Solubility of stearic acid in ethanol, 1-propanol, 2-propanol,l-butanol, acetone, methylene chloride, ethyl acetate and 95% ethanol was experimentally determined by the synthetic method from (293 to 315)K. The laser monitoring observation technique was used to determine the disappearance of the solid phase in a solid + liquid mixture. The solubility of stearic acid in methylene chloride was found to be the highest, and the value in 95% ethanol was the lowest. Results are correlated by semi-empirical equations, which show a good fit to the experimental data.

Synthesis and Dynamic NMR Study of New Stable Ylides Derived from the Reaction of Triphenylphosphine, Dialkyl Acetylenedicarboxylates, and 5-ACYL Meldrum’s Acid

Triphenylphosphine and dialkyl acetylenedicarboxylate react smoothly in the presence of 5-acyl Meldrum's acid in dichloromethane at room temperature and lead to synthesis of new stable ylide derivatives of dimethyl (5-acetyl-2,2-dimethyl-4,6-dioxo-1,3-dioxane-5-yl)-3-(triphenyl-λ5-phosphanylidene) succinate. Dynamic NMR study results of rotamers are reported and compared with the previous-related reports.

Synthesis of sulfonated polynaphthalene, polyanthracene, and polypyrene as strong solid acids via oxidative coupling polymerization

AbstractOxidative coupling polymerization of naphthalene, anthracene, and pyrene with FeCl3 in nitrobenzene under nitrogen gave polynaphthalene (PNP), polyanthracene (PAT), and polypyrene (PPR) in good yields, respectively. PNP, PAT, and PPR were transformed into sulfonated PNP (S‐PNP), S‐PAT, and S‐PPR by the treatment with chlorosulfonic acid in dichloromethane at 25°C for 24 h under nitrogen, respectively. The activities of S‐PPR were higher than those of S‐PNP and S‐PAT. For the hydrolysis of cyclohexyl acetate and oleyl acetate in water, activities of S‐PPR, S‐PAT, and S‐PNP were considerably higher than those of the other conventional solid acids. Rate constants of S‐PPR were 2.8 and 11.7 times larger than those of the sulfonated condensed polynuclear aromatic (S‐COPNA(PR)) resin (PR = pyrene) for the hydrolysis of cyclohexyl acetate and oleyl acetate, respectively. S‐PPR, S‐PAT, and S‐PNP were reused without significant loss of activities. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

A new method for the mononitration of phenol derivatives by poly(4-vinylpyridinium nitrate) and silica sulfuric acid under mild conditions

Abstract This procedure works efficiently for high selective mono nitration of phenol and substituted phenol to corresponding nitro compounds in moderate to high yield using poly(4-vinylpyridinium nitrate) and silica sulfuric acid in dichloromethane at room temperature.

Efficacious N-protection of O-aryl sulfamates with 2,4-dimethoxybenzyl groups

Sulfamates are important functional groups in certain areas of current medicinal chemistry and drug development. Alcohols and phenols are generally converted into the corresponding primary sulfamates (ROSO(2)NH(2) and ArOSO(2)NH(2), respectively) by reaction with sulfamoyl chloride (H(2)NSO(2)Cl). The lability of the O-sulfamate group, especially to basic conditions, usually restricts this method to a later stage of a synthesis. To enable a more flexible approach to the synthesis of phenolic O-sulfamates, a protecting group strategy for sulfamates has been developed. Both sulfamate NH protons were replaced with either 4-methoxybenzyl or 2,4-dimethoxybenzyl. These N-protected sulfamates were stable to oxidising and reducing agents, as well as bases and nucleophiles, thus rendering such masked sulfamates suitable for multi-step synthesis. The protected sulfamates were synthesised by microwave heating of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a substituted phenol to give an aryl 2-methyl-1H-imidazole-1-sulfonate. This imidazole-sulfonate was N-methylated by reaction with trimethyloxonium tetrafluoroborate, which enabled subsequent displacement of 1,2-dimethylimidazole by a dibenzylamine (e.g. bis-2,4-dimethoxybenzylamine). The resulting N-diprotected, ring-substituted phenol O-sulfamates were further manipulated through reactions at the aryl substituent and finally deprotected with trifluoroacetic acid to afford a phenol O-sulfamate. The use of 2,4-dimethoxybenzyl was particularly attractive because deprotection occurred quantitatively within 2 h at room temperature with 10% trifluoroacetic acid in dichloromethane. The four key steps in the protocol described [reaction of 1,1'-sulfonylbis(2-methyl-1H-imidazole) with a phenol, methylation, displacement with a dibenzylamine and deprotection] all proceeded in very high yields.

In-situ ATR-IR investigation of methylcinnamic acid adsorption and hydrogenation on Pd/Al2O3

Abstract The adsorption and hydrogenation of C = C in α-methylcinnamic acid in dichloromethane over the concentration range 2–16 mM have been studied on Al2O3 and Pd/Al2O3 using in-situ attenuated total reflection infrared (ATR-IR) spectroscopy. For Al2O3, the spectra reveal that the acid adsorbs both molecularly and dissociatively, while for 1 wt.% Pd/Al2O3 only the latter is observed. In the case of molecular adsorption, C = O stretching vibrations arising from adsorbed monomer (1710 cm− 1) and dimer (1684 cm− 1) species were observed. In the case of dissociatively adsorbed carboxylate, the typical asymmetric (1522 cm− 1) and symmetric (1378 cm− 1) vibrations are observed. No changes in adsorbed species were observed in the presence of solution-phase H2 over alumina, whereas significant changes occurred for Pd/Al2O3. While bands associated with monomer/dimer and carboxylate species still persist on the surface in the presence of H2, new vibrational features associated with adsorbed product (i.e., α-methylhydrocinnamic acid) are detected. The results demonstrate that the product is strongly adsorbed under hydrogenation conditions, which likely influences the catalytic performance of this system.

Side Chain Anchoring of Tryptophan to Solid Supports Using a Dihydropyranyl Handle: Synthesis of Brevianamide F

The multifunctional character of tryptophan has made it a target for the development of new molecules with therapeutic applications. In this sense the design of alternative solid phase routes would allow the widening of synthetic possibilities to access these molecules through conventional or combinatorial strategies. The present work describes a new strategy for side-chain anchoring of tryptophan to dihydropyranyl-functionalized polystyrene resins and its application to the synthesis of the natural diketopiperazine Brevianamide F. For this study a new handle (4-[(3,4-dihydro-2H-pyran-2-yl)methoxy]benzoic acid) was prepared in order to functionalize aminomethyl or methylbenzhydrylamine resins. A preliminary study in solution using Fmoc-Trp-OR (R = Allyl or Me) and suitable resin models showed that the formation of an hemiaminal linkage with the indole system could be brought about by either conventional or microwave heating in 1,2-dichloroethane and in the presence of pyridine p-toluenesulfonate in yields of 70–95% practically without the formation of sub-products. On the other hand the amino acid could be liberated from the resin at room temperature in yields of up to 90% using trifluoroacetic acid in dichloromethane in the presence of 1,3-dimethoxybenzene as a cation scavenger. The conditions found in solution for the reversible formation of the hemiaminal were only reproducible in solid-phase work using conventional heating. These conditions were used in the synthesis of Brevianamide F, furnishing the diketopiperazine in an overall yield of 56%. These results demonstrate the potential of this strategy for the preparation of new molecules based upon tryptophan as a synthetic precursor.

Liquid–liquid extraction of scandium with nalidixic acid in dichloromethane

The extraction behavior of nalidixic acid (HNA) in CH2Cl2 has been studied for various di- and trivalent metal ions such as Cu(II), Fe(II), Ni(II), Mn(II), Sb(II), Co(II), Sc(III), Y(III), Nd(III) and Eu(III) from aqueous buffer solutions of pH 1–7 with 0.1 mol dm−3 nalidixic acid in dichloromethane. Separation factors of Sc(III) from these metals has shown that its clean separation is possible at pH 3.4–4. The parameters affecting the extraction of Sc(III) were optimized. The composition of the extracted adduct was determined by slope analysis method that came out to be Sc(NA)3. Extraction of Sc(III) was studied in the presence of various cations and anions. Among the anions studied only fluoride, citrate and oxalate have significant interference whereas, Fe(III) has reduced the extraction to 53% that can be removed by using ascorbic acid as reducing agent. The proposed extraction system proved good stability up to six extraction-stripping stages for the extraction of Sc(III).

Syntheses of terminally functionalized polyisobutylene derivatives using diazonium salts

AbstractA new strategy for the synthesis of end‐functionalized polyisobutylene (PIB) oligomers is detailed. Commercially available vinyl‐terminated PIB oligomers were modified to form aniline‐terminated PIB via an aromatic electrophilic substitution reaction. The PIB‐bound aryl amines so formed were then converted into diazonium salts using isopentyl nitrite and an acid in methylene chloride. These salts served as versatile intermediates in synthetic reactions affording azo dye‐containing PIB derivatives and other terminally‐functionalized PIB derivatives not readily available by other reactions. The advantages and limitations of various name reactions including diazo couplings, Sandmeyer reactions, dediazoniations, and Heck reactions are discussed. The kinetics of polar substitution reactions at the termini of these nonpolar oligomers and the effects of solvent on these reactions were also examined. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011