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A novel iron-catalyzed ring opening of cyclopropanols and their 1,6-conjugate addition to p-quinone methides for accessing substituted phenols is disclosed. In this protocol, various cyclopropanols are converted to alkyl radicals and undergo 1,6-conjugate addition to p-quinone methides toward C-C bond formation. The salient features of this methodology include operationally simple and mild reaction conditions, environmentally benign protocol, high efficiency, inexpensive catalyst, good to excellent yield, and a wide range of substrate scope.

A novel one-pot transition metal-free and Brönsted acid mediated 1,6-conjugate addition of bisnuleophilic diol on biselectrophilc para-quinone methide followed by ipso cyclization assisted by NBS has been developed under mild reaction conditions, offers a new approach to synthesize spiro 1,4-dioxane cyclohexadienone derivatives. This strategy features broad substrate scope of p-QMs with high functional group tolerance and good yields of spirocyclic scaffolds (60-92 %). N-Bromo succinimide an important role in an ipso spirocyclization with high efficiency.

Vanillic acid has always been in high-demand in pharmaceutical, cosmetic, food, flavor, alcohol and polymer industries. Present study achieved highly pure synthesis of vanillic acid from vanillin using whole cells of Ochrobactrum anthropi strain T5_1. The complete biotransformation of vanillin (2 g/L) in to vanillic acid (2.2 g/L) with 95 % yield was achieved in single step in 7 h, whereas 5 g/L vanillin was converted to vanillic acid in 31 h. The vanillic acid thus produced was validated using LC-MS, GC-MS, FTIR and NMR. Further, vanillic acid was evaluated for in vitro anti-tyrosinase and cytotoxic properties on B16F1 skin cell line in dose dependent manner with IC

As a part of our ongoing research on the synthesis of bioactive constituents or molecules by using an organocatalytic approach, enantioselective total syntheses of ligraminol D and ligraminol E were achieved starting from a commercially available nonchiral aldehyde. Key steps in this synthesis were an asymmetric α-aminoxylation of an aldehyde and a Mitsunobu reaction.

New simplistic, one pot synthesis of series of substituted β-keto sulfones from styrenes, NBS and aromatic sodium sulfinate salts were synthesized by sonication. The reactions were transition-metal catalyst free and the reactions were also co-oxidant free as NBS plays a dual role of both the bromine source and oxidant in green solvent water at moderate temperature.

The 3,4-dihydroquinazolinone (DHQ) moiety is a highly valued scaffold in medicinal chemistry due to the vast number of biologically-active compounds based on this core structure. Current synthetic methods to access these compounds are limited in terms of diversity and flexibility and often require the use of toxic reagents or expensive transition-metal catalysts. Herein, we describe the discovery and development of a novel cascade cyclization/Leuckart–Wallach type strategy to prepare substituted DHQs in a modular and efficient process using readily-available starting materials. Notably, the reaction requires only the addition of formic acid or acetic acid/formic acid and produces H2O, CO2 and methanol as the sole reaction byproducts. Overall, the reaction provides an attractive entry point into this important class of compounds and could even be extended to isotopic labelling via the site-selective incorporation of a deuterium atom.

The 3,4-dihydroquinazolinone (DHQ) moiety is a highly valued scaffold in medicinal chemistry due to the vast number of biologically-active compounds based on this core structure. Current synthetic methods to access these compounds are limited in terms of diversity and flexibility and often require the use of toxic reagents or expensive transition-metal catalysts. Herein, we describe the discovery and development of a novel cascade cyclization/Leuckart-Wallach type strategy to prepare substituted DHQs in a modular and efficient process using readily-available starting materials. Notably, the reaction requires only the addition of formic acid or acetic acid/formic acid and produces H

An efficient enantioselective total synthesis of pyrrolo-[2,1-c][1,4]benzodiazepine (PBD) monomers (S)-(−)-barmumycin and (S)-(+)-boseongazepine B and collective formal total syntheses of oxoprothracarcin, prothracarcin and (S)-(+)-boseongazepine C are described. The present approach is based on an efficient construction of an ethylidene substituted C-4 pyrrolidine core, that is the stereocontrolled introduction of a trisubstituted double bond through simple enolate α-alkylation of an ester, which also relies on a proline catalysed asymmetric α-amination followed by HWE olefination. The present synthetic route possesses superior stereocontrol over the C-4 ethylidene substituent as well as the C-(S) stereogenic center, which allows more functional variations on the five-membered prolinol core as compared to the existing PBD synthesis.

An efficient stereodivergent total synthesis of anti-Alzheimer agent (R)-(−) and (S)-(+)-arundic acid has been achieved from both chiral and nonchiral materials. This strategy features an efficient approach to separable diastereomeric C-2 chiral 4-pentenol intermediates employing proline catalysed asymmetric α-aminooxylation and [3,3] sigmatropic Claisen rearrangement are the highlights of present synthesis.

Development of an effective method for the detection of picric acid (PA) in aqueous phase has attracted great attention. In this work, the luminescent probe Eu-1 involving a hexadentate −2-Amino-3-phenylpropanol based ligand L was successfully exploited for the selective detection of PA in presence of other nitro analytes in aqueous medium. The selective detection of PA and nitrite by Eu-1 was rationalized through DFT computational study.

A concise asymmetric total synthesis of dihydroisocoumarins such as 6-methoxymellein, kigelin and fusarentin 6,7-dimethyl ether in high enantiopurity have been achieved from non-chiral aldehydes by employing proline catalysed asymmetric α-aminoxylation reaction. The required stereochemistry of hydroxyl group have been generated by alternating L or D proline as a organocatalyst in α-aminoxylation step and lactone ring is assembled by oxa-Pictet-Spengler cyclisation reaction as the key steps.

A novel, green, eco-friendly and cost-effective biological route for the synthesis of palladium nanoparticles (PdNPs) from commercially available palladium chloride and easily isolable hormone Oxytocin as reducing agent is reported here. Characterization of PdNPs were done using various techniques, UV–visible spectroscopy, XRD, TEM and EDAX, characterization data confirmed the formation of Pd0 from Pd2+. The size of synthesized PdNPs were 15–20 nm. The scope of Pd nanoparticles was studied for the C–C bond formation Suzuki reaction. The catalytic activity of PdNPs was excellent in short reaction time and reaction works in green solvent water as well as catalyst can be recycled. Simple and efficient approach for total synthesis of aspongpyrazine A of the recently isolated natural substance is described.

An efficient collective formal/total synthesis of Sceletium alkaloids and their seco-congeners has been reported. The bicyclic core of (±)-mesembrine, (±)-tortuosamine, and (±)-N-formyltortuosamine with all required functionalities including the characteristic quaternary benzylic carbon is achieved by employing the Wittig olefination–Claisen rearrangement protocol and synergistic Cu(I)/iminium catalyzed [3 + 3] condensation of O-acetylketoxime and α,β-unsaturated aldehyde (acrolein).

Hydrogen released in nuclear reactor containment under severe accident scenario poses a threat to containment and hence needs to be regulated by catalytic recombination. Mixed noble metal catalysts with platinum–palladium supported on stainless steel wire gauze and cordierite support have been developed for this purpose. The developed catalysts have been found to be highly efficient for removal of hydrogen concentration in the range of 1.5 to 7.0% v/v in air. Though both the catalysts exhibit similar kinetics for lower hydrogen concentration, cordierite supported catalysts exhibits better kinetic rate at higher hydrogen concentration. The performances of these catalysts in presence of various probable catalytic poison like carbon monoxide and catalytic inhibitors like moisture, carbon dioxide, and hydrocarbons provide data for use of these catalysts under the actual scenario. Compared to stainless steel wire gauze supported catalyst, the cordierite based catalyst are found to exhibit enhanced resistance towards carbon monoxide and limited temperature rise for safer application at higher hydrogen concentrations.

Accidents at TMI, USA and the recent one at Fukushima, JAPAN has emphasized the need for mitigation of hydrogen generated in nuclear reactor containment during accidental conditions. Passive Autocatalytic Recombiner (PAR) is one of the best solutions to deal with such situations during loss of coolant accidents. A novel breed of catalysts based on cordierite supported Pt nanoparticles has been prepared by chemical reduction route for mitigating the hydrogen generated during such accidents. These catalysts have been characterized for their phase purity, surface composition, surface area, particle size, morphology and elemental loading of the noble metal. The supported noble metal particles are found to be of 7 nm–11 nm dimensions, depending on the extent of noble metal loading. The catalytic activity of these catalysts has been evaluated in presence and absence of various prospective contaminants like carbon monoxide, carbon dioxide, methane, humidity, and condensed water in a laboratory scale reactor. Developed catalysts have been found to be catalytically active for H 2 –O 2 recombination reaction in presence of 100% relative humidity and 2000 ppm of carbon monoxide.

A new strategy toward biologically active enantiomerically pure benzomorphan analogues is described. The key steps in the synthesis are the l -proline catalyzed asymmetric α-aminooxylation of an aldehyde and the titanium tetrachloride promoted intramolecular oxa-Pictet–Spengler cyclization of (4 R )-2-(bromomethyl)-4-(2,5-dimethoxybenzyl)-1,3-dioxolane. In the intramolecular oxa-Pictet–Spengler cyclization, cis -pyran 8a (71%) formed over the trans -pyran 8b (14%). Computational modeling studies provided an insight into the stereoselectivity of the products. Docking studies of benzomorphan derivatives indicated that compound 6c had the best binding efficiency, and that it formed extensive hydrogen bonding with TYR148 on transmembrane (TM) helix 3 and HIS297 on TM6 of the μ-opioid receptor, which belong to the G-protein coupled receptor super family.

A rapid method for selective cleavage of aryl methylethers can be achieved in the presence of a protic acid and a catalytic amount of phase-transfer catalyst (Aliquat-336). Aliquat-336 accelerates the rate of reaction and affords the corresponding phenols in excellent to good yields on a wide variety of substrates. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]

PdCl2 catalyzed carbon–carbon bond formation (Heck reaction) between substituted aryl halides and olefins was carried out without a ligand, under irradiation with UV–visible light. The results demonstrated that UV–visible light accelerated the rate of the reaction, leading to an excellent yield of corresponding products. The recovered palladium nanoparticles could be thermally recycled several times. PdCl2 gave excellent conversion up to the fifth addition of substrate.

The rate coefficients for the reactions of OH radicals with three fluoroalcohols, CF 3 CH 2 OH ( k 1 ), CF 3 CF 2 CF 2 CH 2 OH ( k 2 ), and CHF 2 CF 2 CH 2 OH ( k 3 ), have been measured in the temperature range of 298–363 K, at a total pressure of ∼55 torr, using LP-LIF method. The kinetic parameters measured for CF 3 CH 2 OH, which is well studied, matches with the previous reports within error limits. The rate expression for k 2 is (1.54 ± 0.80) × 10 −12 exp (−765 ± 170)/ T ), and for k 3 is (1.12 ± 0.26) × 10 −12 exp (−560 ± 80)/ T ). Based on the above values of the rate coefficients, the tropospheric lifetimes with respect to removal by reaction with OH have been estimated to be 0.38 and 0.26 years for CF 3 CF 2 CF 2 CH 2 OH and CHF 2 CF 2 CH 2 OH respectively, supporting their potential use as HFC alternatives. The results are discussed along with the literature data on other fluoroalcohols. The present study is aimed to assess the effect of additional CF 2 groups and H atoms on tropospheric lifetime and global warming potential of fluoroalcohols. The results confirm that the rate coefficients at room temperature and activation energy parameters are independent of n, for the reaction of OH with fluoroalcohols of general formula CF 3 (CF 2 ) n CH 2 OH, which are potential CFC/HFC alternatives.

A series of diester-dicarboxylic acids, L1H2, L2H2, L3H2, L4H2, and L5H2 and their dinuclear Cu2 complexes [Cu(L1)CH3CN]2 (1), [Cu(L2)H2O]2 (2), [Cu(L3)CH3CN]2 (3), [Cu(L4)EtOH]2 (4), and [Cu(L5)CH3CN]2 (5), were synthesized. The crystal structures obtained for 1, 2, and 4 and the density functional theory optimized structures for 2, 3, and 5 illustrated the formation of tetracarboxylate “paddle wheel” complexes. The phthalyl and diphenyl head groups and the spacer moieties were appropriately altered and the size of the chelate ring expanded from 15-membered in 1 to 21-membered in 5. The dinuclear units have strong Cu–Cu interaction with EPR spectra exploring spin coupled features.

The Zn-mediated elimination of N-Boc protected iodo acetonide undergoes intramolecular cyclization to afford N-Boc-C1 vinyl tetrahydroisoquinoline in good yield.

A large amount of hydrogen is generated in nuclear reactor during loss of coolant accident (LOCA) conditions. This can be a threat to containment integrity if flammable limit (4% in air) is crossed. Passive autocatalytic recombiner is one of the most feasible remedies for this. Here we report a new class of mixed noble metal catalysts prepared by modified methods, viz Pt, Pt + Pd or Pt followed Pd on stainless steel wire gauze. These catalysts were characterised for noble metal loading, phase purity by XRD, morphology of surface by Scanning Electron Microscopy (SEM). They were then evaluated for their catalytic activity for H 2 –O 2 recombination reaction under static air condition and in presence of various poisons like carbon dioxide, methane, carbon monoxide and water.

Photodissociation of 2-(bromomethyl)hexafluoro-2-propanol (BMHFP) and 3-bromo-1-propanol (BP), involving σ C – Br * ← n Br transition at 193 nm, has been investigated by measuring laser-induced fluorescence spectra of the expected OH product. The OH channel is a minor dissociation pathway with a quantum yield of 0.17 ± 0.05 in BMHFP, whereas it was not observed in BP. Partitioning of the available energy into translation, rotation, and vibration of the photoproducts has been measured by state selective detection of the nascent OH product in BMHFP. OH is produced mostly in the ground vibrational level ( v ″ = 0), with a rotational distribution being characterized by a temperature of 465 ± 25 K. But, a significant fraction of the available energy of 30.2 kcal mol −1 is partitioned into translation of OH (14.6 kcal mol −1 ). The OH( v ″ = 0, J ″) populations in the spin-orbit states as well as in the Λ-doublet states are statistical. A plausible mechanism of OH formation on excitation of BMHFP at 193 nm is suggested, with the primary reaction channel being elimination of Br atom by direct C–Br bond dissociation from a repulsive surface. The Br radical is detected using (2 + 1) resonance-enhanced multiphoton ionization (REMPI) at ∼234 nm. It is produced in both the ground ( 2 P 3/2 ) and the excited ( 2 P 1/2 ) spin-orbit states with the relative quantum yield of the latter to be 0.36. The co-fragment of Br undergoes secondary C–O bond dissociation to produce OH and F 3 C–C( CH 2 )–CF 3 , with the reaction having a barrier located in the exit channel. In this two-step three-body dissociation process, a major fraction of the available energy is released into translation (〈 f T 〉 ∼ 0.75), resulting from an impulsive C–Br bond dissociation in the primary step and presence of an exit barrier in the secondary process. Experimental results combined with theoretical calculations provide a clear picture of the dynamics of OH formation from BMHFP at 193 nm. In addition, the energetics of another channel, competing with OH, have been calculated from the primary product F 3 C–C(CH 2 )(OH)–CF 3 . In contrast to BMHFP, the OH product could not be observed from the photolysis of 3-bromo-1-propanol (another saturated halogenated propanol) at 193 nm under the detection limit of the present experimental condition, although it has a higher absorption cross-section at 193 nm.

An efficient organocatalytic route for the preparation of enantioselective synthesis of (S)-1-arylpropan-2-ols derivatives, including the key intermediate of antiepileptic agent (−)-talampanel is described. The key steps involved are L-proline-catalyzed asymmetric α-aminooxylation of aldehydes and regioselective tosylation of diols followed by reduction.

A concise high yielding enantioselective synthesis of (R)-N-Boc-2-hydroxymethylmorpholine, N-(3,4-dichlorobenzyl)(R)-2-hydroxymethylmorpholine, and (R)-benzylmorpholine has been achieved by employing proline-catalyzed asymmetric α-aminooxylation of aldehyde and palladium-catalyzed intramolecular reductive amination of azido aldehyde as the key steps.

A short and efficient organocatalytic enantioselective formal synthesis of HRV 3C-protease inhibitor (1 R ,3 S )-thysanone is achieved in a nine-step with 98.7% enantiomeric excess, by employing l -proline-catalyzed asymmetric α-aminooxylation of aldehyde and Oxa-Pictet–Spengler cyclization as the key steps.

Phosphine-free palladium–salen complexes, N , N ′-bis(salicylidene)-ethylenediamino-palladium and N , N ′-bis(salicylidene)-1,2-phenylenediamino palladium, are found to be highly active catalysts for the Heck olefination of aryl iodides and Suzuki reaction of aryl iodides and bromides giving excellent yields (70–90%) of products under aerobic conditions, in short reaction times (10–60 min).

The ethylation of biphenyl (BP) with ethene was examined over dealuminated H-mordenite (MOR; SiO 2 /Al 2 O 3 = 206). The ethylation occurred non-shape-selectively, and gave a mixture of ethylbiphenyls (EBPs), diethylbiphenyls (DEBPs), and higher ethylates. The ethylation of BP to EBPs was yielded in the ratio, 2-EBP:3-EBP:4-EBP = 2:2:1 at the initial stages. The reaction occurs under kinetic control. The formation of 4,4′-DEBP was less selective than that of the other isomers; however, the combined selectivity for DEBPs with 4-ethyl groups was higher than 80% during the reaction. 4-EBP was consumed rapidly than the other EBPs in the ethylation of EBPs to DEBPs. Less bulky DEBPs, particularly, 4,4′-DEBP disappeared preferentially compared to the other DEBPs in the ethylation of EBPs to higher ethylates. These results show that the MOR channels are too large for the shape-selective formation of 4-EBP and 4,4′-DEBP by the “restricted transition state selectivity mechanism”. The reactivities of reaction intermediates in the ethylation of BP decreased in the order: 4,4′-DEBP > 4-EBP > BP ≫ 3-EBP ≫ 2-EBP. These three EBP isomers have quite different reactivities for the further ethylation: 4-EBP was preferentially consumed to yield DEBPs with 4-ethyl groups. 3-EBP partly participated in the ethylation to DEBPs, particularly, at high conversion; however, 2-EBP was not ethylated even at the high conversion. Further, 4,4′-DEBP was preferentially ethylated to higher ethylates because it is the most reactive among BP, EBPs, and DEBPs. These high reactivities of 4-EBP and 4,4′-DEBP among their isomers were due to the “reactant selectivity mechanism”. Molecular modeling of the diffusion of the products suggests that the MOR channels are too large for the selective formation of 4,4′-DEBP because all DEBPs can diffuse in the channels. The preferential disappearance of 4-EBP and 4,4′-DEBP is due to the difference of the diffusion in the channels among their isomers. These simulations are corresponding to the experimental results.

Regioselective nuclear bromination of aromatic compounds is investigated with N-bromosuccinimide as the brominating agent under UV irradiation to afford the corresponding brominated compounds. The reaction proceeds at ambient temperature (30 ± 2 °C) without any catalyst. In most of the reactions, regioselectively mono-brominated products are obtained in good to high yields. The conversion and selectivity for bromination depend on the nature of the substituent on the aromatic ring.

Metalloaluminophosphates with AFI topology (MAPO-5; M: Mg, Ca, Sr, Ba, and Zn) synthesized by the dry gel conversion (DGC) method were used as catalysts for the alkylation of biphenyl (BP). MgAPO-5 and ZnAPO-5 had high catalytic activities of the isopropylation; however, activities of CaAPO-5, SrAPO-5, and BaAPO-5 were much lower than those of MgAPO-5 and ZnAPO-5. These results suggest that the catalytic activity of MAPO-5 molecular sieves was originated by the acidity due to the isomorphous substitution of M2+ for Al3+. The selectivities for 4,4′-diisopropylbiphenyl (4,4′-DIPB) for all MAPO-5 molecular sieves are at the level of 70%. On the basis of various reaction behaviors, the predominant formation of 4,4′-DIBP was considered to be mainly due to the steric restriction on the transition state of the isopropylation to the least bulky isomer inside the channel of MAPO-5 molecular sieves. The isopropylation of BP over MgAPO-5 and ZnAPO-5 was accompanied by the isomerization of 4,4′-DIPB to thermodynamically more stable isomers, 3,4′-DIPB at the higher temperatures; the decrease in the selectivity for 4,4′-DIPB was observed in both bulk and encapsulated products. These results show that 4,4′-DIPB formed inside channels was isomerized inside the channels in addition to external acid sites. The channels of MAPO-5 molecular sieves are large enough to allow the isomerization of 4,4′-DIPB especially at higher temperatures: this is quite different from those of H-mordenite. The sec- and tert-butylations of BP over MgAPO-5 and ZnAPO-5 gave selectively the least bulky isomers, 4,4′-di-sec-butylbiphenyl (4,4′-DSBB) and 4,4′-di-tert-butylbiphenyl (4,4′-DTBB), respectively. The selectivity for the least bulky isomer increased with increasing the bulkiness of alkylating agents in the order: isopropylation

Passive autocatalytic recombiner (PAR) is one of the most suitable devices for mitigation of hydrogen, generated in nuclear power plant under accidental conditions. For this purpose we report development of stainless steel wire gauze supported Pt-Ru nanoparticles as catalysts. Simultaneous electroless deposition has been employed for the synthesis of the catalysts. Pt-Ru based bimetallic catalysts were characterized for their rate of coating kinetics, noble metal loading, phase purity by XRD and surface morphology by SEM, TEM and elemental analysis by SIMS. Developed catalysts were found to be active for efficient recombination of hydrogen and oxygen in air as well as in presence of various prospective poisons like CO2, CH4, CO and relative humidity. Pt-Ru based bimetallic catalyst with 0.9% loading was found to be active for CO poisoning up to 400 ppm of CO.

Vapor-phase ethylation of biphenyl (BP) with ethanol over the MTW zeolites was examined by using a fixed-bed flow reactor, and compared to the catalyses over MOR and MFI zeolites. Two types of MTW zeolites: MTW-S (small crystal) and MTW-L (large crystal) were synthesized under hydrothermal conditions. The selectivity for 4,4'-diethyl-biphenyl (4,4'-DEBP) over the MTW zeolites was the highest among the other zeolites, such as MOR and MFI. The catalytic activity of MTW-S was higher than MTW-L. The selectivities for 4,4'-DEBP at 300°C were ca. 30% for MTW-S and ca. 22% for MTW-L among the DEBP isomers. The dealumination of the MTW zeolites enhanced the selectivity for 4,4'-DEBP although the catalytic activity was slightly decreased. In particular, the selectivity for 4,4'-DEBP over dealuminated MTW-L by steaming and subsequent refluxing in hydrochloric acid increased from 22 to 42% at 300 °C. The enhancement of the selectivity for 4,4'-DEBP is due to the decrease in non-selective reactions at external acid sites because these sites are removed by the dealumination. The selectivities are higher than those of equilibrium mixtures, and the slimmest isomer. 4,4'-DEBP is preferentially formed due to the steric interaction of reactants and products with acidic sites in the MTW channels. Molecular modeling on the diffusion of products in the MTW channel suggests that 4,4'-DEBP isomer can diffuse most easily among DEBP isomers. 4,4'-DEBP and other isomers easily diffuse inside MOR channel; however, they cannot in the MFI channels. These results show that the formation of 4,4'-DEBP is the most favorable due to the diffusion and the restriction of transition state in the MTW channels.

MgAPO-36, a magnesioaluminophosphate molecular sieves with ATS topology, was successfully synthesized by means of dry-gel conversion (DGC) method. Heating protocol during the synthesis was a key factor for the crystallization of pure MgAPO-36. The best results were obtained by heating at 140 °C for 24 h after aging of the gel at 105 °C for 48 h. However, ATS phase without magnesium was not obtained under our synthesis conditions because of co-crystallization of AFI phase. MgAPO-36 with high surface area was obtained by the calcination of as-synthesized samples in nitrogen stream or in vacuo; however, the calcinations in air stream resulted in decrease of surface area due to collapse of microporous structure. Characterization was performed by XRD, NH 3 -TPD, TG-DTA, SEM, N 2 adsorption, and ICP analyses. Bronsted acidic character appeared in MgAPO-36 because of the replacement of a part of Al 3+ with Mg 2+ in the framework. The selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) was about 30–35% among DIPB isomers in the isopropylation of biphenyl (BP) over MgAPO-36: this value is lower than MOR and other zeolites with straight channels. Because the selectivity of 4,4′-DIPB is higher than the composition in equilibrium, the catalysis is controlled by the pores of MgAPO-36. The relative low selectivity for MgAPO-36 is not due to their pore entrance, but to differences in their pore structure. ATS channel with annular side pocket is too loose for selective formation of the transition state to 4,4′-DIPB, and the formation of bulkier transition states for the other isomers, such as 3,3′- and 3,4′-DIPB, are also allowed inside the channel.

Metalloaluminophosphate molecular sieves with AFI topology, in which a part of aluminum is substituted isomorphously to alkaline earth metals: Mg, Ca, Sr, and Ba (MAPO-5; M = Mg, Ca, Sr and Ba), were synthesized by hydrothermal synthesis (HTS) method and two types of dry–gel conversion (DGC) methods: vapor-phase transport (VPT) and steam-assisted conversion (SAC) methods, using triethylamine (Et3N) as a structure-directing agent (SDA). Systematic studies were carried out by varying the synthesis parameters such as gel composition including content of alkaline earth metals and SDA, amount of external bulk water, and heating time. It has been observed that MO/Al2O3 ratio of starting gel plays an important role in the crystallization of the molecular sieves. The ratios from 0.025 to 0.10 gave pure MAPO-5 with AFI topology; however, MAPO-34 with CHA topology was observed as an impurity with further increase of the Mg content. The amount of Et3N also played important role for the crystallization: Et3N/Al2O3 ratios from 0.38 to 0.76 gave pure MgAPO-5 and CaAPO-5, whereas SrAPO-5 and BaAPO-5 were obtained as pure phase from 0.76 to 1.52. MAPO-5 molecular sieves were crystallized even in the absence of external bulk water. Period for crystallization was studied from 3 to 48 h; the highest intensities were observed between 12 and 18 h for all cases. The occluded SDA was removed by calcination at 550 °C. The molecular sieves were characterized by XRD, ICP, TG-DTA, SEM, FT-IR, N2 and pyridine adsorption, and NH3-TPD. Alkaline earth metals, at least a part of them, are isomorphously substituted in the framework of AFI topology judging from NH3-TPD, unit cell parameters, and their FT-IR spectra of adsorbed pyridine. The substitution of alkaline earth metal with aluminum produced acidic sites in the molecular sieves: substitution of Al3+ to Mg2+ enhanced the appearance of strong acidity; however, only weak acidities appeared for CaAPO-5, SrAPO-5, and BaAPO-5 in small amount. The isopropylation of benzene and biphenyl was examined over MAPO-5 by VPT method to characterize their acidic properties. Their catalytic activity decreases in the order: MgAPO-5 ≫ CaAPO-5 ⩾ SrAPO-5 ⩾ BaAPO-5; ≫ APO-5; moderate to good selectivity for 4,4′-DIPB was observed in the level of 50–70% for all MAPO-5. These catalytic properties support strongly the incorporation of alkaline earth metals in the AFI framework.

Zincoaluminophosphates, ZnAPO-5 and ZnAPO-36 with AFI and ATS topologies, were successfully synthesized by dry-gel conversion (DGC) method: vapor-phase transport (VPT) and steam-assisted conversion (SAC) methods. ZnAPO-5 was synthesized successfully at 175°C by VPT and SAC methods using Et 3 N as structure directing agent (SDA). ZnAPO-36 was also obtained by VPT and SAC methods using Pr 3 N as SDA. The heating protocol was a key factor for the crystallization in the synthesis of ZnAPO-36: the best result was obtained by heating at 140°C for 1 d after aging of the gel at 105°C for 2 d. Calcination procedure is important to get microporous molecular sieves. ZnAPO-5 by VPT method calcined at 550°C gave clear XRD with high microporosity. Highly microporous ZnAPO-36 by VPT method was obtained by careful calcination. Characterization of these zincoaluminophosphates was performed by XRD, NH 3 -TPD, TG, SEM, N 2 adsorption, and ICP analysis. ZnAPO-5 and ZnAPO-36 have the Bronsted acidic characters by the substitution of a part of aluminum with zinc. The isopropylation of biphenyl (BP) over these molecular sieves gave different level of the selectivities for 4,4'-DIPB: 60-75% for ZnAPO-5 and 35-45% for ZnAPO-36: these selectivities are in the similar level to corresponding magnesioaluminophosphates corresponding magnesioaluminophosphates. These differences of ZnAPO-5 and ZnAPO-36 in the selectivity are due to the pore structure: ZnAPO-5 has one-dimensional straight channel; however, ZnAPO-36 has one-dimensional channel with side pocket. The steric restriction by ZnAPO-5 effectively controls the transition state to differentiate the slim isomers from others; however, pores of ZnAPO-36 cannot differentiate effectively the isomers because of their side pockets.

Aluminophosphate (AlPO 4 -5) molecular sieves partly substituted with alkaline earth metal in the framework (MAPO-5; M = Mg, Ca, Sr, and Ba) have been employed as catalysts for the isopropylation of benzene with 2-propanol. The incorporation of alkaline earth metal ions gives rise to Bronsted acidity of different acidic strengths. The influence of type of alkaline earth metals, MO/Al 2 O 3 ratio, reaction parameters such as reaction temperature, molar ratio of benzene and 2-propanol (B/IP), space velocity, and time on stream were studied. The selectivity of cumene (IPB) and benzene conversion was in the order Mg ≫ Ca > Sr > BaAPO-5. This order is correlated with acidity of the molecular sieves. The selectivity of IPB for MgAPO-5 was maximized at MgO/Al 2 O 3 = 0.1. It increased with reaction temperature, low WHSV, high B/IP ratio, whereas it decreased with time on stream. The major by-products were 1,3- and 1,4-diisopropylbenzenes (1,3- and 1,4-DIPBs): among them, 1,3-DIPB was predominant over 1,4-DIPB at higher temperatures. The dealkylation of 1,3- and 1,4-DIPBs gives IPB as a major product. Molecular modeling studies reveal that 1,3-DIPB is the most stable and bulkier among DIPB isomers.

Aluminophosphate molecular sieves with AFI topology, in which framework Al3+ is partly substituted with Mg2+ (MgAPO-5), were synthesized by dry-gel conversion (DGC, including vapor-phase transport [VPT] and steam-assisted conversion [SAC]) method using triethylamine (Et3N) as a structure-directing agent (SDA). Systematic studies were carried out in DGC method using different compositions of gel (concentration of Mg and SDA), amount of external bulk water and period of synthesis. MgO/Al2O3 ratios in the range of 0.025

Zirconia-pillared montmorillonite was synthesized by an ultrasonication method and characterized by XRD, FT-IR of adsorbed pyridine, XPS, XRF and low temperature nitrogen adsorption techniques. The basal spacing of d (0 0 1) reflection of the pillared clay estimated by XRD was found to be 20 A. XRD study showed well distribution of pillars without any non-pillared portion of the clay. FT-IR studies showed the formation of both Lewis and Bronsted acid sites due to pillaring. Pyridine desorption studies revealed that the Bronsted sites were stronger than Lewis acid sites. The activity of the Zr-PILC for the alkylation of benzene with long chain α-olefins [C 10 –C 13 ] was investigated. The Bronsted acid sites played major role in this reaction.

The electronic property of Pt supported on cation-exchanged Pt-M-ETS-10 [where M = Li, Na, K, Rb, Cs, Mg(OH), Ca(OH), Sr(OH), and Ba(OH) ions] depends on the location of Pt and the nature of the exchanged metal ion. Electronic changes on the Pt cluster are highly influenced when it is near TiO6 rather than SiO4 units. The benzene selectivity in the transformation of n-hexane over Pt-M-ETS-10 molecular sieves is found to correlate with the basicity of the exchanged cations and the average electron density of Pt. The relationship between electron density on Pt and the amount of CO2 adsorbed (from TPD) and the frequency of the ν3 band of CO2 adsorbed in FTIR is established. We report here the results of ab initio Hartree−Fock calculations on model clusters representing the Pt (active) site, molecular sieve with cations, Pt-M-molecular sieve, benzene, and H2S adsorbed over Pt-molecular sieve. Generally, the charge density on Pt decreases in the order Cs > Rb > K > Ba(OH) > Na > Sr(OH) > Ca(OH) > Li > Mg(OH) a...

A palladium-loaded ETS-10 molecular sieve has been used as a catalyst in Heck reaction. The catalyst exhibits high activity and selectivity towards the carbon–carbon coupling of aryl halides with olefins, even at low concentrations of Pd (0.009 to 1.4 mol% with respect to the substrate). In the case of the coupling of ethyl acrylate with iodobenzene, 96% conversion of iodobenzene with greater than 98% selectivity could be obtained within 1 h over a 0.2 wt % Pd-loaded catalyst. The catalyst activates aryl bromide and chloride substrates, and appears to be heterogeneous. The reaction has been investigated with different alkyl halides, olefins and bases.

The regio-selective nitration of toluene to para-nitrotoluene with dilute HNO3 has been studied over catalyst beta zeolite. The effect of reaction temperature, concentration of HNO3 and molar ratio of toluene to HNO3 is reported. The maximum conversion of 55% (toluene to HNO3 ratio, 1.7:1), selectivity to para-nitrotoluene of 70%, and catalyst life of 75 h (weight hourly space velocity (WHSV)=0.2) were obtained using 20% nitric acid at temperature of 120 °C. The catalyst deactivated faster when the concentration of acid and the temperature of reaction and WHSV was increased. The physicochemical characterization of the deactivated catalyst showed the structural stability of beta zeolite under the reaction conditions, but the para-nitrotoluene, and other oxidation products 4-nitrobenzoic acid, benzaldehyde, benzoic acid and anthraquinone were found deposited on the catalyst surface. Even then, the selectivity for para-nitrotoluene remains nearly constant. The molecular modeling study revealed that para-nitrotoluene encounters the least resistance for diffusion in the beta zeolite. These observations indicate that the shape selective nitration of toluene takes place inside the zeolite pores. The catalyst with alumina binder was found to be more active than the catalyst without binder because of higher acidity. The deactivated catalyst can almost be regenerated by washing the catalyst with organic solvents.

Although single-cell oil (SCO) has been studied for decades, lipid production from lignocellulosic biomass has received substantial attention only in recent years as biofuel research moves toward producing drop-in fuels. This review gives an overview of the feasibility and challenges that exist in realizing microbial lipid production from lignocellulosic biomass in a biorefinery. The aspects covered here include biorefinery technologies, the microbial oil market, oleaginous microbes, lipid accumulation metabolism, strain development, process configurations, lignocellulosic lipid production, technical hurdles, lipid recovery, and technoeconomics. The lignocellulosic SCO-based biorefinery will be feasible only if a combination of low- and high-value lipids are coproduced, while lignin and protein are upgraded to high-value products.

The intramolecular oxa-Pictet—Spengler cyclization of optically active dioxolane (I) yields cis-pyran as the major product.

The radical scavenging activities of most of the title pyridobenzoxazines (II) (13 examples) are close to or even better than commercial standards ascorbic acid and BHT.