Effects of Desilication in NaOH/Piperidine Medium and Phosphorus Modification on the Catalytic Activity of HZSM-5 Catalyst in Methanol to Propylene Conversion.

BACKGROUND: Propylene is one of the main petrochemical building blocks applied as a feedstock for various chemical and polymer intermediates. The methanol-to-propylene (MTP) processes are reliable options for propylene production from non-petroleum resources. The highsilica ZSM-5 zeolite is found to be a reliable candidate for the methanol to propylene catalysis. OBJECTIVE: In this study, the mesoporosity was first introduced into a high silica ZSM-5 zeolite via an alkaline treatment by NaOH solution with piperidine to decrease the diffusion limitation, and then the structure of zeolite was stabilized by phosphorus modification to improve the acidic properties and to enhance the catalyst stability. METHODS: High-silica H-ZSM-5 catalysts (Si/Al = 200) were successfully prepared through microwave-assisted hydrothermal technique in the presence of tetrapropyl ammonium hydroxide (TPAOH) structure-directing agent. The mesoporosity was efficiently introduced into the ZSM-5 crystals via desilication derived from alkaline NaOH/piperidine solution. Then, the acidity of the desilicated ZSM-5 samples was improved using phosphorus modification. The catalysts were subjected to XRD, ICP-OES, FE-SEM, BET, TGA, FT-IR and NH3-TPD analysis. RESULTS: The catalytic performance of the prepared catalysts in the methanol to propylene (MTP) reaction was examined in a fixed-bed reactor at 475 °C, atmospheric pressure and methanol WHSV of 0.9 h-1. The results showed that the alkaline treatment in NaOH/piperidine solution created uniform mesoporosity with no severe damage in the crystal structure. Similarly, phosphorus modification developed the acidic features and led to the optimal catalytic efficiency in terms of the maximum propylene selectivity (49.16%) and P/E ratio (5.97) as well as the catalyst lifetime. CONCLUSION: The results showed an excellent catalytic activity in terms of 99.21% methanol conversion, good propylene selectivity up to 49.16%, a high ratio of P/E of 5.97 and a low selectivity to C5 + hydrocarbons of 11.57% for ZS-D-PI-P sample.

Styryl-cinnamate hybrid inhibits glioma by alleviating translation, bioenergetics and other key cellular responses leading to apoptosis.

Gliomas are lethal and aggressive form of brain tumors with resistance to conventional radiation and cytotoxic chemotherapies; inviting continuous efforts for drug discovery and drug delivery. Interestingly, small molecule hybrids are one such pharmacophore that continues to capture interest owing to their pluripotent medicinal effects. Accordingly, we earlier reported synthesis of potent Styryl-cinnamate hybrids (analogues of Salvianolic acid F) along with its plausible mode of action (MOA). We explored iTRAQ-LC/MS-MS technique to deduce differentially expressed landscape of native & phospho-proteins in treated glioma cells. Based on this, Protein-Protein Interactome (PPI) was looked into by employing computational tools and further validated in vitro. We hereby report that the Styryl-cinnamate hybrid, an analogue of natural Salvianolic acid F, alters key regulatory proteins involved in translation, cytoskeleton development, bioenergetics, DNA repair, angiogenesis and ubiquitination. Cell cycle analysis dictates arrest at G0/G1 stage along with reduced levels of cyclin D; involved in G1 progression. We discovered that Styryl-cinnamate hybrid targets glioma by intrinsically triggering metabolite-mediated stress. Various oncological circuits alleviated by the potential drug candidate strongly supports the role of such pharmacophores as anticancer drugs. Although, further analysis of SC hybrid in treating xenografts or solid tumors is yet to be explored but their candidature has gained huge impetus through this study. This study equips us better in understanding the shift in proteomic landscape after treating glioma cells with SC hybrid. It also allows us to elicit molecular targets of this potential drug before progressing to preclinical studies.

The Effect of Copper Addition on the Activity and Stability of Iron-Based CO2 Hydrogenation Catalysts.

Iron-based CO2 catalysts have shown promise as a viable route to the production of olefins from CO2 and H2 gas. However, these catalysts can suffer from low conversion and high methane selectivity, as well as being particularly vulnerable to water produced during the reaction. In an effort to improve both the activity and durability of iron-based catalysts on an alumina support, copper (10-30%) has been added to the catalyst matrix. In this paper, the effects of copper addition on the catalyst activity and morphology are examined. The addition of 10% copper significantly increases the CO2 conversion, and decreases methane and carbon monoxide selectivity, without significantly altering the crystallinity and structure of the catalyst itself. The FeCu/K catalysts form an inverse spinel crystal phase that is independent of copper content and a metallic phase that increases in abundance with copper loading (>10% Cu). At higher loadings, copper separates from the iron oxide phase and produces metallic copper as shown by SEM-EDS. An addition of copper appears to increase the rate of the Fischer-Tropsch reaction step, as shown by modeling of the chemical kinetics and the inter- and intra-particle transport of mass and energy.

Synthesis of a Functionalized Benzofuran as a Synthon for Salvianolic Acid C Analogues as Potential LDL Antioxidants.

A palladium mediated synthesis of a common synthon for the syntheses of antioxidant analogues of naturally occurring salvianolic acids is presented. The synthetic route may be used to obtain analogues with a balanced lipophilicity/hydrophilicity which may result in potentially interesting LDL antioxidants for the prevention of cardiovascular diseases.

Hierarchical structured α-Al2O3 supported S-promoted Fe catalysts for direct conversion of syngas to lower olefins.

Hierarchical structured α-Al2O3 is shown to be able to effectively disperse and immobilize iron species, in comparison with commercial α-Al2O3. After promotion using an appropriate amount of sulfur, iron catalysts exhibit not only enhanced Fischer-Tropsch synthesis activity and selectivity toward lower olefins, but also increased resistance against carbon deposits.

Engineering isoprenoid biosynthesis in Artemisia annua L. for the production of taxadiene: a key intermediate of taxol.

Taxadiene is the first committed precursor to paclitaxel, marketed as Taxol, arguably the most important anticancer agent against ovarian and breast cancer. In Taxus, taxadiene is directly synthesized from geranylgeranyl diphosphate (GGPP) that is the common precursor for diterpenoids and is found in most plants and microbes. In this study, Artemisia annua L., a Chinese medicinal herb that grows fast and is rich in terpenoids, was used as a genetic engineering host to produce taxadiene. The TXS (taxadiene synthase) gene, cloned from Taxus and inserted into pCAMBIA1304, was transformed into Artemisia annua L. using the Agrobacterium tumefaciens-mediated method. Thirty independent transgenic plants were obtained, and GC-MS analysis was used to confirm that taxadiene was produced and accumulated up to 129.7 µg/g dry mass. However, the high expression of TXS did not affect plant growth or photosynthesis in transgenic Artemisia annua L. It is notable that artemisinin is produced and stored in leaves and most taxadiene accumulated in the stem of transgenic Artemisia annua L., suggesting a new way to produce two important compounds in one transgenic plant: leaves for artemisinin and stem for taxadiene. Overall, this study demonstrates that genetic engineering of the taxane biosynthetic pathway in Artemisia annua L. for the production of taxadiene is feasible.

Catalyst-controlled stereoselective olefin metathesis as a principal strategy in multistep synthesis design: a concise route to (+)-neopeltolide.

Molybdenum-, tungsten-, and ruthenium-based complexes that control the stereochemical outcome of olefin metathesis reactions have been recently introduced. However, the complementary nature of these systems through their combined use in multistep complex molecule synthesis has not been illustrated. A concise diastereo- and enantioselective route that furnishes the anti-proliferative natural product neopeltolide is now disclosed. Catalytic transformations are employed to address every stereochemical issue. Among the featured processes are an enantioselective ring-opening/cross-metathesis promoted by a Mo monoaryloxide pyrrolide (MAP) complex and a macrocyclic ring-closing metathesis that affords a trisubstituted alkene and is catalyzed by a Mo bis(aryloxide) species. Furthermore, Z-selective cross-metathesis reactions, facilitated by Mo and Ru complexes, have been employed in the stereoselective synthesis of the acyclic dienyl moiety of the target molecule.

Catalyst-free synthesis of skipped dienes from phosphorus ylides, allylic carbonates, and aldehydes via a one-pot SN2' allylation-Wittig strategy.

A catalyst-free allylic alkylation of stabilized phosphorus ylides with allylic carbonates via a regioselective SN2' process is presented. Subsequent one-pot Wittig reaction with both aliphatic and aromatic aldehydes as well as ketenes provides structurally diverse skipped dienes (1,4-dienes) in generally high yields and moderate to excellent stereoselectivity with flexible substituent patterns. This one-pot SN2' allylation-Wittig strategy constitutes a convenient and efficient synthetic method for highly functionalized skipped dienes from readily available starting materials.

Synthesis of sterically-crowded olefins, gem-dihaloalkenes, butatrienes, and thioketenes through the reaction of substituted bornane-2-thiones or bornane-2-selones with conventional carbenes or metal carbenoids.

Reaction of highly-substituted bornane-2-selones with a diazoalkane in the presence of either Rh2(OAc)4 or CuCl formed sterically-crowded exo-methylenic products, and similar treatment of the thiones or selones with dihalocarbenes or a propadienylidene carbene also formed dihaloalkenes, butatrienes, and thioketenes. All these reactions were assumed to proceed through a pathway involving the in situ formation and subsequent ring closure of chalcogenocarbonyl ylides.

Biomass catalytic pyrolysis to produce olefins and aromatics with a physically mixed catalyst.

Zeolite catalysts with micropores present good catalytic characteristics in biomass catalytic pyrolysis process. However, large-molecule oxygenates produced from pyrolysis cannot enter their pores and would form coke on their surfaces, which decreases hydrocarbon yield and deactivates catalyst rapidly. This paper proposed adding some mesoporous and macroporous catalysts (Gamma-Al2O3, CaO and MCM-41) in the microporous catalyst (LOSA-1) for biomass catalytic pyrolysis. The added catalysts were used to crack the large-molecule oxygenates into small-molecule oxygenates, while LOSA-1 was used to convert these small-molecule oxygenates into olefins and aromatics. The results show that all the additives in LOSA-1 enhanced hydrocarbon yield obviously. The maximum aromatic+olefin yield of 25.3% obtained with 10% Gamma-Al2O3/90% LOSA-1, which was boosted by 39.8% compared to that obtained with pure LOSA-1. Besides, all the additives in LOSA-1 improved the selectivities of low-carbon components in olefins and aromatics significantly.

Total synthesis of (+)-pentamethylsalvianolic acid C.

The total synthesis of a methylated analogue of (+)-Salvianolic acid C has been achieved. Key aspects of the synthetic route include an economical Cu(I) acetylide coupling, unique carboxyl activation conditions via microwave irradiation and a novel lipase catalysed kinetic resolution of a racemic mixture of secondary alcohol Danshensu. The preparation of this methylated analogue will not only improve the bioavailability, but also enable access to new and wider bioactivity applications for (+)-Salvianolic acid C.

Selective conversion of bio-oil to light olefins: controlling catalytic cracking for maximum olefins.

Light olefins are the basic building blocks for the petrochemical industry. In this work, selective production of light olefins from catalytic cracking of bio-oil was performed by using the La/HZSM-5 catalyst. With a nearly complete conversion of bio-oil, the maximum yield reached 0.28±0.02 kg olefins/(kg bio-oil), which was close to that from methanol. Addition of La into zeolite efficiently changed the total acid amount of HZSM-5, especially the acid distribution among the strong, medium and weak acid sites. A moderate increase of the number of the medium acid sites effectively enhanced the olefins selectivity and improved the catalyst stability. The comparison between the catalytic cracking and pyrolysis of bio-oil was studied. The mechanism of the conversion of bio-oil to light olefins was also discussed.

Stereoselective synthesis of five biologically active, naturally occurring medium and large ring lactones.

Stereoselective syntheses of five naturally occurring, pharmacologically active medium and large ring lactones are described. Key synthetic methods used were, depending on the cases, olefin metatheses, asymmetric allylations and C-glycosidations.

Catalytic Z-selective olefin cross-metathesis for natural product synthesis.

Alkenes are found in many biologically active molecules, and there are a large number of chemical transformations in which alkenes act as the reactants or products (or both) of the reaction. Many alkenes exist as either the E or the higher-energy Z stereoisomer. Catalytic procedures for the stereoselective formation of alkenes are valuable, yet methods enabling the synthesis of 1,2-disubstituted Z alkenes are scarce. Here we report catalytic Z-selective cross-metathesis reactions of terminal enol ethers, which have not been reported previously, and of allylic amides, used until now only in E-selective processes. The corresponding disubstituted alkenes are formed in up to >98% Z selectivity and 97% yield. These transformations, promoted by catalysts that contain the highly abundant and inexpensive metal molybdenum, are amenable to gram-scale operations. Use of reduced pressure is introduced as a simple and effective strategy for achieving high stereoselectivity. The utility of this method is demonstrated by its use in syntheses of an anti-oxidant plasmalogen phospholipid, found in electrically active tissues and implicated in Alzheimer's disease, and the potent immunostimulant KRN7000.

Stereoselective syntheses of trisubstituted olefins via platinum catalysis: alpha-silylenones with geometrical complementarity.

The stereoselective syntheses of alpha-silylenones using catalytic PtCl(2) are reported. Via alkyne activation, alpha-hydroxypropargylsilanes are converted to (Z)-silylenones through a highly selective silicon migration. The complementary (E)-silylenones are accessed by a regioselective hydrosilylation of the ynone precursor. The synthetic utility of these compounds is demonstrated in cross-coupling reactions, highlighting the potential of these protocols for the syntheses of geometrically defined trisubstituted olefins.

Tuning the shape of nanoparticles to control their catalytic properties: selective hydrogenation of 1,3-butadiene on Pd/Al2O3.

Shape-controlled Pd nanoparticles supported on powder alumina are more efficient for selective butadiene hydrogenation to butene when they exhibit high fractions of (111) facets.

Modification of the side chain of micromolide, an anti-tuberculosis natural product.

This paper describes a series of modifications of the side chain of micromolide, an anti-tuberculosis natural product. Most of the synthesized compounds showed significantly decreased activities, which suggests that the long aliphatic side chain of micromolide and its double bond are essential to its activity.

Palladium-catalysed cis- and trans-silaboration of terminal alkynes: complementary access to stereo-defined trisubstituted alkenes.

Palladium-catalysed cis- and trans-silaboration of terminal alkynes has been developed via the addition of (chlorodimethylsilyl)pinacolborane, followed by a one-pot conversion of the chloro group on the silicon atom to an isopropoxy group.