原位生成的Ph3C+均相有机催化剂催化4,4’-芳亚甲基-二（3-甲基-1-苯基-1H-吡唑-5-醇）高效合成（英文）简

Trityl chloride (Ph₃CCl) efficiently catalyzes the condensation of 3-methyl-1-phenyl-1H-pyrazol- 5(4H)-one and aromatic aldehydes under mild and solvent-free conditions, affording 4,4''- (arylmethylene)-bis(3-methyl-1-phenyl-1H- pyrazol-5-ol)s in high to excellent yields and in short reaction time. The presence of the requisite organocatalytic trityl carbocation (Ph₃C⁺) species was confirmed by analysis of infrared, ¹H NMR, and ultra violet spectral data. A plausible mechanism was proposed for the reaction based on the observations and literature precedent.     

One-pot synthesis of 2-amino-3-cyanopyridine derivatives under solvent-free conditions

A series of 2-amino-3-cyanopyridines were obtained from aryl aldehydes, substituted acetophenones, malononitrile and ammonium acetate in good to excellent yields by proceeding through a simple, mild and efficient procedure utilizing N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] and poly(N-bromo-N-ethylbenzene-1,3-disulfonamide) [PBBS] as catalysts.     

Brønsted acidic ionic liquid supported on rice husk ash (RHA-[pmim]HSO4): A highly efficient and reusable catalyst for the synthesis of 1-(benzothiazolylamino)phenylmethyl-2-naphthols

In this work, rice husk ash (RHA), as a natural source of amorphous silica, was used as a support for the immobilization of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium hydrogen sulfate. The immobilized acidic ionic liquid was characterized with a variety of techniques, including infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and pH analysis. This reagent showed excellent catalytic activity for the preparation of 1-(benzothiazolylamino)phenylmethyl-2-naphthols from the one-pot condensation of an aldehyde, 2-aminobenzothiazole and 2-naphthol, at 100 °C under solvent-free conditions. The procedure gave the products in excellent yields in very short reaction times with high TOF. Also, this catalyst can be reused six times without loss of its catalytic activity.     

无溶剂合成SAPO-5沸石中表面活性剂对其片状形貌的控制

在表面活性剂如十六烷基三甲基溴化铵(CTAB)的存在下,采用无溶剂法合成出具有片状形貌的SAPO-5沸石晶体。 X射线衍射和扫描电镜结果表明,所合成的样品具有很好的结晶度和可控的片状形貌,在合成过程中, CTAB的添加量对其片状形貌特别是片状的厚度的影响很大。考虑到一维的微孔AFI结构独特,具有特殊片状形貌的SAPO-5晶体有望应用于催化方面。     

Ultrasound-assisted enzymatic synthesis of xylitol fatty acid esters in solvent-free conditions

A commercial immobilized lipase was successfully used for the synthesis of five xylityl acyl esters by means of the esterification of free fatty acids (caprylic, capric, lauric and myristic, respectively) with xylitol under solvent-free conditions. Ultrasound-assistance was shown to be a key tool to overcome the handicap imposed by both the mutual immiscibility of fatty acids and xylitol substrates, and the semisolid character of the initial reaction mixtures. In such semisolid systems, ultrasonic irradiation may enable the transport of substrate molecules to the enzyme catalytic-site, leading to the efficient synthesis of xylityl fatty ester (e.g. up to 95% yield after 90 min at 40 °C), with xylityl monoacyl ester and xylitol diacyl ester appearing as the main products (greater than 96%), assessed by HPLC and NMR analyses. The separation of products was carried out by heating and simple centrifugation of the reaction medium, which was possible due to different densities of the resulting fractions.     

The first synthesis of β-phenylchalcogeno-α,β-unsaturated esters via hydrochalcogenation of acetylenes using microwave and solvent-free conditions

A simple, clean, and efficient solvent-free protocol was developed for hydrochalcogenation of methyl propiolate derivatives with phenylchalcogenolate anion generated in situ from the respective diphenyl dichalcogenide (S, Se, Te) using alumina supported sodium borohydride. This efficient and improved method is general and furnishes the (Z)-β-phenylchalcogeno-α,β-unsaturated esters in yields and with selectivity comparable to those using organic solvent and inert atmosphere. The use of MW irradiation facilitates the procedure and accelerates the reaction.     

Catalytic significance of organometallic compounds immobilized on mesoporous silica: economically and environmentally important examples

Because of the availability of well-defined nanoporous silicas, possessing (controllable) pore diameters of 30 Å to ca. 500 Å, bulky organometallic species may be readily introduced on to the inner walls of these thermally stable, solid supports. Four kinds of highly active catalysts that may be derived from the combination of these two materials are illustrated. First, starting from titanocene dichloride, single-site Ti^IV-centered epoxidation catalysts of exceptional activity may be formed. These are now used in the preparation of epoxy polymers and other products from naturally occurring methyl esters of fatty acids, a novel example of sustainable development. Second, asymmetric organometallic species that exhibit good enantioselectivity as homogeneous catalysts (in the hydrogenation of keto-esters, for example) may be significantly improved in their catalytic performance when they are anchored to a concave silica surface, their ee values are boosted by the spatial restrictions imposed by the mesopores within which they are anchored. Examples of three distinct diamino-complexes of Rh(I) are illustrated for the selective hydrogenations of methylbenzoylformate and E-α-phenylcinnamic acid. In the third kind of catalyst immobilized on nanoporous silica, several mixed-metal carbonylates are used as precursors. They are firmly anchored to the inner walls and may, by gentle calcining, be converted to bimetallic catalysts [e.g., Ru₆Pd₆, Ru₅Pt and Ru₁₀Pt₂] that exhibit very high activity, under mild conditions, in the single-step, solvent-free hydrogenation of a range of economically important unsaturated compounds. The fourth category of immobilized, organometallics illustrated here is of the “ship-in-bottle” kind, where, typically, a chlorinated copper-phthalocyanine incarcerated within the cages of zeolite-X efficiently converts methane to methanol and also smoothly oxyhalogenates a range of aromatic compounds (e.g., benzene, phenol, toluene, aniline, anisole and resorcinol) in air, again under mild conditions. The unconventional techniques, both in situ and ex situ, required to characterize all these immobilized catalysts are outlined.     

Solid State Cleavage of Semicarbazones with Cerium Ammonium Nitrate Supported by Wet Alumina

Summary.  Cerium ammonium nitrate on wet alumina rapidly regenerates carbonyl compounds from their corresponding semicarbazone derivatives under solvent-free conditions; the process is expedited by microwave irradiation. Received April 25, 2001. Accepted (revised) July 9, 2001     

Kröhnke pyridines: an efficient solvent-free synthesis of 2,4,6-triarylpyridines

A simple and efficient synthesis of 2,4,6-triarylpyridines is described from a novel reaction between chalcones and ammonium acetate under solvent-free conditions in excellent yields.     

A mild and efficient acetylation of alcohols, phenols and amines with acetic anhydride using La(NO3)3·6H2O as a catalyst under solvent-free conditions

A wide variety of alcohols, phenols and amines are efficiently and selectively converted into the corresponding acetates by treatment with acetic anhydride in the presence of catalytic amounts of La(NO₃)₃·6H₂O under solvent-free conditions at room temperature. The method is compatible with acid sensitive hydroxyl protecting groups such as TBDMS, THP, OBz, OBn, Boc and some isopropylidenes and offers excellent yields of the mono acetates of 1,3-, 1,4- and 1,5-diols.