Letters in Organic Chemistry - Volume 13, Issue 5, 2016

Background: The energetic properties and relative aromaticity of some derivatives of Benzamide (BEA) structure were investigated in which the BEA was substituted by CH3, NO2, CN, Cl and OCH3 groups in two meta and para positions. For this purpose, density functional theory (DFT) calculations were applied using B3LYP/6-31+G (d, p) method. The obtained results indicated that the stability of on the derivatives changed in the order of Cl> NO2 OCH3 CN> CH3 for para and meta positions. Methods: Density functional theory (DFT) calculations of BEA structure with different para and meta substitutions were conducted in which geometries, energies, electrophilicity HOMA, HOSE, Aj, and HOMED values were obtained at the B3LYP/6-31+G(d, p) level. Results: To calculate the stability of various derivatives of BEA we investigated the electronic energy levels, the values of relative energy. If the structure with the lowest energy is considered zero, and other structures are measured in term that, the para and meta stability for both position is obtained as the following: Cl> NO2 OCH3 CN> CH3 (Fig. 3 and 4). These results suggest that with the increasing of atomic radius of substituted and the reducing of the electronic attraction power of substituted, at the viewpoint of energy, the structure will be more stable. Conclusion: Density functional theory calculations in B3LYP/6-31+G (d, p) level of theory on the structure of BEA structure with various substituent in the para and meta position indicate that from the viewpoint of energy, all of the meta structures with ER-substituent are more stable than the para structures and BEA structure with EW-substituent are more stable than the meta structure. Aromaticity indices of BEA derivatives including HOMA, HOMED, HOSE, Aj, NICS (0) and NICS (1) were calculated in which the aromaticity increased in the order of NO2 CN> Cl> OCH3 CH3 for meta position whereas, this order for para substitutions was as NO2 CN> Cl> CH3 OCH3. Finally, it was included that placing EW substituents at both meta and para positions enhance the aromaticity while substituting BEA by ER groups, weakens the aromaticity.

DFT calculations (B3LYP/6-311G+(d,p)) on antiaromatic compounds showed that these compounds are characterized by the presence of nonoccupied bonding π orbitals. The D index cne be used to characterize this type of compounds. The correlations between D and NICS for some pentalene derivatives have been examined. The aromaticity of antiaromatic pentalene in the excited triplet state has been discussed. The aromaticity of fullerene and of some other bowl-shaped molecules has been examined.

Thymol (1) and Carvacrol (2) are monoterpenoid natural products that display in vitro antimicrobial activity against Campylobacter jejuni and coli, food-borne pathogens found in animal distal guts/avian crops that commonly contaminate meat and poultry during processing. Recently, it has been shown that thymol-β-D-glucopyranoside (3), a glucosylated variant of the free monoterpenoid, also induces Campylobacter reductions within collected gut contents. Unfortunately, commercial sources of 3 are prohibitively expensive for large-scale use, and syntheses of glucosylated variants of either thymol or carvacrol are low yielding. Herein we report on an improved synthesis of both 3 as well as carvacrol-β- D-glucopyranoside (4). This synthesis utilizes phase transfer catalysis glycosylation conditions in lieu of the previously reported, low-yielding and expensive Koenigs-Knorr reactions.

Background: Fe(II) and Zn(II) complex series have been synthesized from Schiff base ligands derived from furan-2-carbaldehyde and thiophene-2-carbaldehyde. Elemental, infrared, ultraviolet- visible, NMR and thermal analysis, also mass spectroscopy and magnetic susceptibility measurements were performed to explain the structures of these synthesized ligands and their metal complexes. The formulas based on analytical, spectral, and magnetic studies, the complexes can be demonstrated as [M(L1)2](H2O)n, [M(L2)2](H2O)n, where M = Zn(II) and Fe(II). An octahedral geometry was suggested for the Zn(II) and Fe(II) complexes. The antioxidant, antiradical and antimicrobial properties of the Zn(II) and Fe(II) complexes were investigated using different in vitro assays. Some of the complexes showed reasonable amount of antioxidant and antimicrobial activity.

A new and convenient synthesis of the P1 fragment of HCV inhibitor, boceprevir is described. This approach efficiently provides P1 fragment of boceprevir using simple and easy handling reagents suitable for scale up. This synthetic route involves the conversion of ester intermediate into novel intermediate, α-chloro ketone via chloroacetate Claisen condensation, followed by further simple conversions to β-amino-α-hydroxy amide, P1 fragment of boceprevir in high yield.

Background: Michaelis-Arbuzov reaction is one of the well studied reaction in phosphorus chemistry and used for the synthesis of phosphonates, phosphinates and phosphine oxides. Phosphonates are not only versatile intermediates in synthetic organic chemistry but also plays a vital role in biological activity. The usage of niobium(V) chloride as a catalyst has attracted the considerable attention due to its low hygroscopic character, high stability, cost effective, low loading and ease of handling. Methods: The present study describes the synthesis of a series of various aryl/heterocyclic substituted phosphonates/ phosphinates of 2-chloroquinoxaline 3(a-e) and 6-iododibenzo[d,f][1,3]dioxepine 5(a-e) using an expeditious catalyst, niobium(V) chloride by Michaelis-Arbuzov reaction and evaluated their antimicrobial and antioxidant activities. Results: A simple, efficient and new synthetic protocol was developed for the synthesis of quinoxalinyl and dibenzodioxepinyl phosphonate/phosphinate derivatives (3a-e/5a-e) in good yields using niobium(V) chloride as a catalyst. Biological data revealed that compound 5c exhibited potent antimicrobial activity and the compounds 3e and 5e good antioxidant activity. Conclusion: From the results it was concluded that niobium(V) chloride was an efficient catalyst for the synthesis of quinoxalinyl and dibenzodioxepinyl phosphonate/phosphinate derivatives and also exhibited good antimicrobial and antioxidant activities.

Background: Recently a new index, D, has been introduced to quantitatively describe the aromatic properties of an organic compound. Methods: The D index was calcuted optimizing the structure of the selected compound and examining the energy of π orbitals. Results: The index D shows to correlate with NICS of pentaatomic heterocyclic compounds. Several correlations were found depending on the nature, number and relative position of the heteroatoms. The same type of correlations were found by using ASE to correlate with NICS. Conclusion: The D index confirms to be able to describe the aromatic character of pentaatomic aromatic compounds.

Background: The synthesis of triazole derivatives is a major interest among synthetic organic chemists. Indeed, triazole derivatives, especially containing fluorine atom, present wide applications in the field of science materials. In this aim, we have developed this work to propose a new route for the synthesis of fluorinated triazole derivatives. Methods: Various acetylenic compounds derived from γ- and δ-lactam on reaction with using γ- and δ-lactam and sodium azide in the presence of 5 mol% of copper nanoparticles in water to offered triazole derivatives. Results: Replacement of CH3CN with H2O as a solvent, for the reaction catalyzed by CuNPs to produce fluorinated triazole, was finished within 1 h in 90% yield. Conclusion: A simple and efficient protocol for the synthesis of 1,2,3-triazole derivatives using 5 % of copper nanoparticles was developed.

Background: In recent years CO2 utilization and conversion of CO2 into the value added chemicals have attracted great attention of leading research groups. However, CO2 is widely accepted as reagent for the synthesis of carbonates and other important chemicals such as methanol, aspirin, formic acid etc, but CO2 reduction is still a major challenge for the scientific community as they are extremely thermodynamically stable. In this report, we are offering the synthesis of silica-tethered ruthenium catalyst (SRUC) for the hydrogenation of CO2 to formic acid. Methods: The SIRUC catalytic system was synthesized by a multistep grafting process using iminophophine ligand tethered to mesoporus SBA-15 inorganic support. After activating the SRUC catalyst with hydrogen gas, it was applied as hydrogenating catalyst for CO2 gas. It is worth noted that, SBA-15 was synthesized as per reported protocol and the important IV- type isotherm was recorded while performing N2 physisorption analysis. Results: The catalytic efficiency of silica-tethered Ru catalysts was screened for the hydrogenation of CO2 to formic acid. The hydrogenation reaction was carried out in 100 mL autoclave with triethyl amine (NEt3) and water under the pressure of CO2 and hydrogen gas (40 bar, CO2: H2=1:1) at 75°C. The formation of formic acid (or formate) was calculated through 1H NMR. As per the experimental data, it was clearly observed that catalyst system only works effectively with phosphine ligands and offered the formic acid with significant TON/TOF value opposite to SRUC-4A catalytic system. Higher catalytic activity in terms of TON/TOF value was obtained with SRUC-1A material carries the bidentate phosphine ligand at 100°C. Conclusion: In this manuscript, we reported a new protocol to synthesize mesoporous silica-tethered Ru complexes (SRUC 1A-4A). Among these, materials, SRUC 1A was found and effective heterogeneous catalyst for the selective CO2 hydrogenation reaction to obtain formic acid under normal reaction condition. In terms of catalyst recycling, this catalytic system was found highly active in catalyst recycling test up to 6 cycles without any significant loss of TON value of formic acid. In parallel, we also performed the filtration experiment and the obtained results were found in good agreement with recycling test results.

Background: Rigid receptor molecules based on triphenylene ketals exhibit a strong affinity towards some particular guests such as caffeine and trinitrobenzene, thus being good candidates for caffeine or trinitrobenzene sensing applications. It is most important to produce cuppy receptor molecules with special and rigidly oriented functional moieties for the application of molecular recognition. It is still necessary to introduce the bicyclic moiety into the ketal in order to benefit to molecular recognition. Hence, we report a more direct synthesis of triphenylene ketal from commercially available 2,3,6,7,10,11- hexamethoxytriphenylene, which could lead to an easy way to functionalize rigid receptor. Methods: An optimized synthetic protocol has been developed based on triketalizion of 2,3,6,7,10,11-hexahydroxytriphenylene to prepare the rigid triphenylene ketal having bicyclic moieties. To bring in the bicyclic subunits, we synthesized 1-carbethoxy-bicyclo[3.3.1]nonan-9-one starting from the commercially available 2-carbethoxycyclohexanone. Results: Reaction of hexahydroxytriphenylene with the bicyclic ketone in toluene under reflux using a Dean-Stark apparatus yielded a statistical mixture of isomers comprising of 22% of all-syn (2a) and 67% of anti,anti,syn (2b). The process of isomerization of 2b to the statistical mixture and subsequent separation can repeat three times to increase the total yield of 2a to ~60%. The structures of triphenylene ketals were confirmed from their spectroscopic data. Conclusion: Easier and higher-yielding synthesis of rigid triphenylene ketal was developed based on the triketalization of hexahydroxytriphenylene, which eliminates the electrochemical oxidative trimerization step typically required to produce the versatile and rigid receptor molecule. This makes the present route useful for large-scale production.