Constructing Hierarchical Zeolites with Highly Complete Framework via Controlled Desilication.

Desilication in alkaline medium has been widely used in construction of hierarchical zeolites for industrially relevant catalytic processes. The built of hierarchy in zeolites, especially with low aluminum stability or high Si/Al ratio, often suffers from uncontrolled destruction of zeolitic framework, accompanied by a significant loss of microporous domains and intrinsic acidity after desilication. Here, we report a novel and simple methodology for preparation of hierarchical zeolites with highly complete framework and minimum sacrifice of microporosity and acidity. The pre-impregnated amines in zeolite micropores act as inner pore-directing agents (iPDAs), largely protecting the zeolitic framework and moderating the silicon extraction during the alkaline treatment. The resulting hierarchical zeolites exhibit high crystallinity, tunable hierarchy, stable framework, and well-preserved acidity, endowing them with significantly improved mass transport properties and enhanced activities in catalytic conversion of methanol or furfural.

Controlling Factors and Formation Models of Organic Matter Accumulation for the Upper Permian Dalong Formation Black Shale in the Lower Yangtze Region, South China: Constraints from Geochemical Evidence.

The black shale in the upper Permian Dalong Formation is considered as an excellent source rock in the Lower Yangtze region. However, mechanisms of organic matter (OM) accumulation in such a setting are scarcely understood. Here, the characteristics of total organic carbon (TOC) and elemental geochemistry of 33 rock samples from GD1 well are systematically investigated to characterize the paleoenvironmental conditions and OM accumulation mechanisms. Results show that the lower and middle parts of Dalong Formation (section A) display high TOC contents ranging from 1.19 to 6.45% (average 3.19%), whereas the upper part (section B) exhibits medium TOC contents varying from 1.18 to 4.90% (average 2.09%). These data also elucidate that the target shales were deposited in a complex paleoenvironment with moderate to strong water-mass restriction that was characterized by warm and semiarid-semihumid paleoclimate, high biotic productivity, fluctuating plaeoredox conditions, and a relatively high sedimentary rate. Compared to the organic-rich shales from section A mainly developed under an anoxic condition, shales from section B formed in an oxic-to-dysoxic water environment exhibited a comparatively higher sedimentary rate. Moreover, among all these factors that might affect OM accumulation, the paleoredox conditions appear to be the dominant controlling factors for section A, whereas the biotic productivity, paleoredox conditions, and sedimentary rate are the main controlling factors for section B. Finally, two formation models for OM accumulation in Dalong Formation shale in the Lower Yangtze region are proposed. The "preservation model" for OM accumulation in section A emphasizes that the reducing deep-water environment, which was mainly caused by the regional sea level rise, is favorable for OM preservation. The "integrated model" for OM accumulation in section B stresses that greater biotic productivity intensifies respiratory oxygen consumption in a water column and a higher sedimentary rate can greatly shorten OM exposure time for respiration by oxygen, both of which cause OM accumulation under an oxidizing water environment. These findings also add to our knowledge that despite the oxygenated water environment during shale deposition, TOC contents are not necessarily lower.

Organic-Free Synthesis of Zeolite Y with High Si/Al Ratios: Combined Strategy of In Situ Hydroxyl Radical Assistance and Post-Synthesis Treatment.

Zeolite Y, with a high SiO2 /Al2 O3 ratio (SAR), plays an important role in fluidized catalytic cracking processes. However, in situ synthesis of zeolite Y with high SARs remains a challenge because of kinetic limitations. Here, zeolite Y with an SAR of 6.35 is synthesized by a hydroxyl radical assisted route. Density-functional theory (DFT) calculations suggest that hydroxyl radicals preferentially enhanced the formation of Si-O-Si bonds, thus leading to an increased SAR. To further increase the SAR, a dealumination process was carried out using citric acid, with a subsequent second-step hydrothermal crystallization, giving an SAR of up to 7.5 while maintaining good crystallinity and high product yield. The resultant zeolite Y shows good performance in cumene cracking. Introduced here is a new strategy for synthesizing high SAR zeolite Y, which is widely used in commercial applications.

Competitive adsorption desulfurization performance over K - Doped NiY zeolite.

NiY and KNiY were successfully prepared by impregnation method and characterized by X-ray diffraction (XRD), N2 sorption (BET), scanning electron microscope (SEM), infrared spectrum (IR) and X-ray Photoelectron Spectroscopy (XPS). The competitive adsorption mechanisms of adsorbents were studied by in situ FTIR to explain different desulfurization performance which was evaluated in a miniature fixed-bed flow by gasoline model compounds with 1-hexene or toluene. NiY and KNiY adsorbents showed better desulfurization performance than HY zeolite due to the high selectivity of loaded active metals. Especially, KNiY adsorbent showed its advantages in desulfurization performance with 5vol% olefins or 5vol% aromatics involvement. It could be assigned that introduced K cation enhanced dispersion and content of active Ni species on the surface which made Ni species reduce easily. On the other hand, adsorption mechanisms showed that the protonation reactions of thiophene and 1-hexene occurred on the Brönsted acid sites of NiY, which resulted in pore blockage and the coverage of adsorption active centers. By doping K cation on NiY, the amount of the Brönsted acid sites of NiY was decreased and protonation reactions were weaken. Therefore, the negative effects of Brönsted acid sites were reduced.

Iron-Catalyzed Divergent Tandem Radical Annulation of Aldehydes with Olefins toward Indolines and Dihydropyrans.

Iron-catalyzed divergent tandem radical annulations of aldehydes with olefins are reported. The new strategy allows the rapid and efficient construction of various multifunctionlized indolines (R = Ar) and dihydropyrans (R = Me), which are significant skeletons in bioactive natural products and pharmaceuticals. The substituents of tertiary amines play vital roles to facilitate the desired transformation. Mechanistic studies on indoline formation disclose that the homolytic cleavage of the carbonyl C-H bond might be involved in the rate-determining step, while dissociation of the aromatic C-H bond was most likely included in the product-determining step.

Iron-catalyzed acylation-oxygenation of terminal alkenes for the synthesis of dihydrofurans bearing a quaternary carbon.

Iron-catalyzed acylation-oxygenation of terminal alkenes is reported. Acyl radicals generated by the oxidation of aldehydes add to terminal alkenes and followed by intramolecular oxygenation give functionalized 2,3-dihydrofuran derivatives bearing a quaternary carbon.

Synthesis and characterization of multi-active site grafting starch copolymer initiated by KMnO4 and HIO4/H2SO4 systems.

A novel initiator system containing KMO4, HIO4, and H2SO4 for synthesizing grafting starch copolymers is reported. In this system, KMnO4 was used to oxidize the primary hydroxyl group to aldehyde group of glucose in the starch, and the formed aldehyde group reacted with Mn(4+), Mn(3+) to afford starch free radical. At the same time HIO4 perform as the oxidant to open the C2C3 bond of glucose ring in starch to form two more aldehyde groups, and then two more free radicals are generated. As a result one glucose unit could provide ultimately three active sites for starch grafting reaction. Graft copolymers with a higher grafting ratio and grafting efficiency could be obtained by using the composite initiation system than the KMnO4/H2SO4 initiation system. The grafting of polyacrylamide onto the corn starch backbone was confirmed by viscometry, elemental analysis, infrared spectroscopy, nuclear magnetic resonance, X-ray diffraction and scanning electron microscopy.

Total synthesis of (±)-clavilactones†A, B, and proposed†D through iron-catalyzed carbonylation-peroxidation of olefin.

Biologically significant clavilactones A, B, and the previously proposed D have been synthesized through iron-catalyzed carbonylation-peroxidation of a 1,5-diene. Three steps from aldehydes, alkenes, and tert-butylhydroperoxide build up α,ß-epoxy-γ-butyrolactone skeleton as a key building block for synthesis of clavilactone family and its derivatives. Based on our results, the structure of the proposed clavilactone D is not correct and requires revision.

Unstable-Fe-site-induced formation of mesopores in microporous zeolite Y without using organic templates.

A novel organic template-free strategy for generating mesoporosity in Y zeolites is reported. It is revealed that Fe(3+) functioned as unstable sites in the Fe-NaY zeolite, which promotes deferrization-dealumination, leading to enhanced formation of intra-crystalline mesopores as well as desirable interconnectivity. The mesopore-enriched zeolite exhibits a remarkable ability in conversion of the bulky substrate.

Direct benzothiophene formation via oxygen-triggered intermolecular cyclization of thiophenols and alkynes assisted by manganese/PhCOOH.

An intermolecular oxidative cyclization between thiophenols and alkynes for benzothiophene formation has been established. A variety of multifunctional benzothiophenes are synthesized. In addition, we demonstrated that the obtained benzothiophenes can be used for further transformation to give diverse benzothiophene derivatives efficiently and selectively.

Zirconium-mediated selective synthesis of 1,2,4,5-tetrasubstituted benzenes from two silyl-substituted alkynes and one internal alkyne.

Selective synthesis of 1,2,4,5-tetrasubstituted benzenes was achieved via formation of 2,5-bis(trimethylsilyl)zirconacyclopentadienes from 2 equiv of TMS-substituted alkynes with Cp(2)ZrBu(2) and Cu-mediated formation of 1,4-disilylbenzene by cycloaddition of zirconacyclopentadienes to disubstituted alkynes. Preparation of 1,2,3,4,9,10-hexasubstituted pentacene and 2,3,6,11-tetrasubstituted naphthacene derivatives were demonstrated by a homologation or coupling method using tetrasubstituted benzene.

Homologation method for preparation of substituted pentacenes and naphthacenes.

Multi-substituted pentacenes, such as 1,2,3,4,6,8,9,10,11,13-decasubstituted pentacenes (Type I), 1,2,3,4,6,13-hexasubstituted pentacenes (Type II), 1,2,3,4-tetrasubstituted pentacenes (Type III), and 2,3-disubstituted pentacenes (Type IV), 1,2,3,4,6,11-hexasubstituted naphthacenes (Type V), 1,2,3,4-tetrasubstituted naphthacenes (Type VI), and 2,3-disubstituted naphthacenes (Type VII), were prepared by a homologation method. The homologation method involved the conversion of phthalic acid ester derivatives to two ring extended phthalic acid ester derivatives via diynes and metallacyclopentadienes using transition metals, such as Zr and Rh. For the formation of pentacenes of Type III and Type IV and naphthacenes of Type VII, trimethylsilyl-substituted diynes were used for zirconocene-mediated cyclization. Elimination of the trimethylsilyl groups after the cyclization afforded nonsubstituted position on pentacenes or naphthacenes. Structures of 1,4,6,8,9,10,11,13-octaethyl-2,3-bis(methoxycarbonyl)pentacene (9a) and 8,9,10,11-tetraethyl-2,3-bis(methoxycarbonyl)-1,4,6,13-tetrapropylpentacene (9b) were determined by X-ray analysis. The structure of 9a had the herringbone packing system in the crystal like nonsubstituted pentacene. However, 9b, whose substituents at 1,4,6,13-positions were changed from Et to Pr at 1,4,6,13-positions of 9a, had the face parallel plane system in the crystal.

Direct addition of Zr-C bonds of alkylzirconocenes to activated alkenes.

Direct addition of alkylzirconocenes to activated alkenes was found, for the first time. Octyl- and decylzirconocene chloride reacted with benzylidenemalononitrile to give the corresponding addition products after hydrolysis in 86% and 79% yield, respectively. Zirconacyclopentanes showed a similar reactivity toward activated alkenes with a two-electron-withdrawing group. On the other hand, treatment of the reaction mixture of zirconacyclopentanes and ylidenemalononitriles with iodine afforded six-membered cyclic compounds in high yields. The diastereoselectivity of the cyclized compound was remarkably high and the high selectivity originated from the Zr-promoted cyclization. The structures of cyclic compounds 10b and the major diastereoisomer of 10d were determined by X-ray analysis. Zirconacyclopentenes reacted with ylidenemalononitrile with high chemoselectivity in which the sp(3)-carbon attached to zirconium reacted with ylidenemalononitrile.

Inter- or Intramolecular Carbometalation of Nonactivated Alkynes by Zirconacyclopentanes in the Presence of Copper Chloride.

Five- and six-membered carbocyles 2 and 3 can be obtained from zirconacyclopentanes of type 1 by a novel carbometalation with nonactivated alkynes in the presence of CuCl (see reaction scheme).