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Clay minerals are considered one of the materials of the 20th century for their peculiar physico-chemical features. Among them, halloysite nanotubes (HNTs) are an emerging nanomaterial with a particular tubular structure that makes them a low cost and valuable alternative to the most common carbon nanotubes. Due to their tubular morphology, HNTs are employed in several fields acting as nanocontainers for different compounds for applications in drug carrier and delivery fields, catalysis, and as filler for polymeric matrices. The modification of HNTs’ surfaces allows to the synthesis of different nanoarchitectures that can improve the mechanical and thermal performance of polymer as well as they can enhance the use for the loading and release of chemicals. In this review, we summarize our recent results on halloysite functionalization, both supramolecular and covalent, and the application aforementioned fields.

Hybrid diimidazolium-based ionogels were obtained by dispersing nitrogen-doped carbon nanodots (NCNDs) in ionic liquid (IL) solutions and by using dicationic organic salts as gelators. The properties of the NCND-ionogels were studied in terms of thermal stability, mechanical strength, morphology, rheological, and microscopic analyses. Insights into the formation of the hybrid soft material were attained from kinetics of sol–gel phase transition and from estimating the size of the aggregates, obtained from opacity and resonance light-scattering measurements. We demonstrate that, on one hand, NCNDs were able to favor the gel formation both in the presence of gelating and nongelating ILs. On the other hand, the gelatinous matrix retains and, in some cases, improves the properties of NCNDs. The NCND-ionogels showed the typical fluorescence emission of the carbon dots and a notable antiradical activity, with higher efficiency as compared to the single components. The presented hybrid materials hold great promise for topical applications in antioxidant fields.

The grafting of poly(N-isopropylacrylamide) (PNIPAAM) onto the halloysite external surface is proposed in order to obtain a novel thermoresponsive drug carrier for curcumin delivery. The new nanomaterial is characterized by means of FT-IR spectroscopy, thermogravimetric analysis, and SEM investigations. A high density of polymer chain was achieved at the nanoparticle surface. The PNIPAAM dehydration phenomenon was observed in water above 32 °C that is nearly coincident with the lower critical solution temperature for the polymer. The colloidal stability as well as the wettability of the obtained nanomaterial may be triggered by temperature stimuli. In vitro tests simulating the gastro-intestinal transit demonstrated that the proposed delivery system allows a targeted release of curcumin, preventing its degradation in an acidic medium. We synthesized a new hybrid nanoparticle that is very promising for several applications due to the copresence of a biocompatible region, to the temperature response, and to the hollow cavity, which can load active species.

Selective modification of the inner surface of halloysite nanotubes (HNTs) by the cycloaddition of azides and alkynes (click reaction) was successfully achieved. Fourier transform infrared spectroscopy and thermogravimetry confirmed that the modification involved only the HNT cavity. Morphological investigations evidenced that the functionalized nanotubes formed microfibers and clusters in the micrometer range. By means of the casting method, these nanomaterials were dispersed into biopolymeric matrixes (chitosan and hydroxypropyl cellulose) with the aim of obtaining nanocomposite films with tunable properties from the physicochemical viewpoint. For comparison purposes, we also characterized composite nanomaterials based on pristine halloysite. The mesoscopic structure of the nanocomposites was correlated with their tensile, thermal, and wettability properties, which were found to be strongly dependent on both the nature of the polymer and the HNT functionalization. The attained knowledge represents a basic point for designing new hybrid nanostructures that are useful in specific purposes such as biocompatible packaging.

Here we describe for the first time a sequential Suzuki/asymmetric aldol reaction. Such sequential approach was achieved through the combined use of an ionic liquid supported palladium catalyst and the organocatalyst trans‐4‐(2,2‐diphenylacetoxy)proline. Suzuki and asymmetric aldol reactions were performed under aqueous conditions. The use of a palladium catalyst under basic conditions allowed also the first example of sequential Suzuki/Knoevenagel reaction. Reactions were carried out under aqueous conditions and products were isolated in good to high yields and, in the case of the Suzuki/aldol reaction, with diastereoselectivities up to 91:9 and enantioselectivities up to at least 99 %.

The dichotomic nature of ionic liquids (ILs, simple solvents or supramolecular fluids) induced us to carry out a structural investigation of some mono‐ and dicationic ionic liquids using 1D and 2D NMR, resonance light scattering, and UV/Vis spectroscopy. Ionic liquids with different cation π‐surface areas were used, namely [bmim][NTf2], [Bzmim][NTf2], [Bzbim][NTf2], [p‐Xyl‐(bim)2][NTf2]2, and [m‐Xyl‐(bim)2][NTf2]2[bmim = 1‐butyl‐3‐methylimidazolium, Bzmim = 1‐benzyl‐3‐methylimidazolium, Bzbim = 1‐benzyl‐3‐butylimidazolium, NTf2= bis(trifluoromethansulfonyl)imide]. In order to verify to what extent the structural investigation, coupled with the determination of solvent parameters, could help to rationalize the effects of the solvent media on a given reaction, the thermally induced mononuclear rearrangement of heterocycles was studied. Variation of the cation structure has significant repercussions on the 3D structure of the ILs and on the effect they can exert on a given reaction.

The reaction between an excess of 1,4‐bis(3‐vinylimidazolium‐1‐yl) bromide and a mercaptopropyl‐modified amorphous silica gel or ordered mesoporous silica SBA‐15 in the presence of azobisisobutyronitrile (AIBN) afforded new materials, which have a high loading of imidazolium moieties. These materials, which contain a highly cross‐linked polymeric network, have been denoted as multi‐layered, covalently supported ionic liquid phase (mlc‐SILP) and have been used as support for palladium catalysts containing a high loading of the metal (10 wt%). Such materials were characterized by several techniques (13C magic angle spinning nuclear magnetic resonance, the Brunauer–Emmett–Teller technique, small‐angle X‐ray scattering, X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy). The presence of a homogeneous distribution of palladium nanoparticles was established. The palladium catalysts displayed good activity allowing the synthesis of several biphenyl compounds in high yields working with only 0.1 mol% of palladium loading at mild temperatures (room temperature or 50 °C) in ethanol/water. Reactions carried out on a 10‐mmol scale required only 10 mg of catalysts. Good recyclability was observed.

Ten 4‐acyloxy‐L‐prolines were screened as catalysts at loadings of 2–0.1 mol‐% for the direct asymmetric aldol reaction in water by using variable amounts of water. Among them, a new catalyst, the L‐proline carrying a trans‐4‐(2,2‐diphenylacetoxy) group, and a catalyst previously synthesized by us, the L‐proline carrying a trans‐4‐(4‐phenylbutanoyloxy) group, were found to be excellent catalysts for the aldol reaction between cyclohexanone or cyclopentanone and substituted benzaldehydes when employed in only 1 and 0.5 mol‐%,respectively, at room temperature without additives. For such catalysts, high turnover numbers were obtained, which are among the highest values obtained for enamine organocatalysis. Finally, these catalysts can be synthesized by direct O‐acylation from inexpensive molecules and successfully used in scaled‐up reactions.

Different investigations, such as 1D and 2D NMR spectroscopy, resonance light scattering spectroscopy and molecular dynamics simulations, have been jointly used to achieve a deeper understanding of the degree of structural order in two geminal ionic liquids. In particular, 3,3′‐di‐n‐butyl‐1,1′‐(1,3‐phenylenedimethylene)diimidazolium and 3,3′‐di‐n‐butyl‐1,1′‐(1,4‐phenylenedimethylene)diimidazolium bis[bis(trifluoromethanesulfonyl)imide] have been studied. These geminal ionic liquids were chosen because of the presence of both a rigid phenylenedimethylene link between two imidazolium rings, which should give a high degree of order to the solvent system, and the different shapes of the two cations of the isomers, which could induce different properties and packing in the liquid state. Data collected here show that the two geminal ionic liquids are characterised by a different degree of structural order that induces, for example, a different sensitivity of the two solvent systems to temperature changes or to the presence of a co‐solvent such as methanol.

Several polystyrenesupported proline dipeptides and a prolinamide derivative were prepared by thiol–ene coupling. These materials were used as catalysts for the direct asymmetric aldol reaction in water, and results compared with unsupported catalysts in water. Such an approach gave more active or stereoselective catalysts compared to the unsupported compounds, showing that our immobilization procedure may be useful to develop catalytic materials with enhanced performance. Moreover, these catalysts can be recovered and reused for at least nine times without loss of activity or can be easily regenerated when their activity has decreased. © WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009

The morpholino‐induced elimination of 5‐nitrobenzisoxazole into the relevant 2‐cyano‐4‐nitrophenolate has been used as a sample reaction in order to investigate molecular properties of some room temperature ionic liquids. The kinetic study was carried out at 298 K by means of spectrophotometric measurements. Ionic liquids, which differ in both their cation and anion properties, were used as solvent systems. In particular, aliphatic (pyrrolidinium, piperidinium, and ammonium) and aromatic (imidazolium and pyridinium) ionic liquids were used. For aromatic cations, imidazolium ions having different hydrogen‐bond donor ability or a different alkyl‐chain length were taken into account. The anions chosen ([BF4−], [PF6−], [SbF6−], and [NTf2−]; where NTf2=bis(trifluoromethansulfonyl)imide) showed different shape, size, and coordination ability. Solvent parameters of all ionic liquids used were determined by using spectroscopic probes, such as 4‐nitroaniline, N,N‐diethyl‐4‐nitroaniline, Nile Red, and Reichardt’s dye. Finally, in order to obtain information on the structural organization of the solvent systems, resonance light‐scattering measurements were carried out. The collected data provide evidence that ionic liquids are solvent media which exhibit peculiar features, whose effects can be rationalized only considering all parameters affecting their three‐dimensional structure.

In this review, recent advances in asymmetric organocatalytic reactions carried out with variable amounts of water, from substoichiometric to a large excess reaction medium, are discussed. We also summarize several proposed mechanisms for the different possibilities of the action of water both in the increased activity of the catalyst and in the asymmetric induction. Finally, the application of this catalytic methodology to the enantioselective synthesis of valuable compounds through enamine or iminium catalysis is presented.

New 4substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones cyclohexanone and cyclopentanone and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains 4phenylbutanoate and 4pyren1ylbutanoate provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These results demonstrate that derivatization of the proline moiety with the proper simple hydrophobic substituent in the 4position can furnish highly active and stereoselective catalysts without the need of additional chiral backbones in the molecule. Finally, an explanation of the observed stereoselectivities in the presence of water is provided.

A new prolinamide derivative anchored to a polystyrene support has been straightforwardly prepared and employed as heterogeneous catalyst in the direct asymmetric aldol reaction with good results in terms of yield and stereoselectivity. The optimal reaction conditions were found when a 1:2 vv waterchloroform mixture was used. This mixture was the best compromise between the good swelling properties of chloroform and the formation of a concentrated organic phase due to the presence of water. Noticeably, the enantioselectivities obtained employing acetone as ketone were, to the best of our knowledge, the highest achieved with a supported proline derivative. This catalyst can be easily recovered, regenerated and recycled, without loss of activity, at least for twelve cycles.

Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum-mechanical calculations (PM3/COSMO and ab initio 3-21G/COSMO) support this mechanism and give more insight into the role of hydrogen carbonate.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A simple synthetic methodology for the preparation of a polystyrene-supported L-proline material is reported, and this material has been used as catalyst in direct asymmetric aldol reactions between several ketones and arylaldehydes to furnish aldol products in high yields and stereoselectivities. Screening of solvents showed that these reactions take place only in the presence of water or methanol, at lower levels of conversion in the latter case. This solvent effect, coupled with the observed high stereoselectivities, has been explained in terms of the formation of a hydrophobic core in the inner surface of the resin, whereas the hydrophilic proline moiety lies at the resin/water interface. Such a microenvironment both promotes the aldol reaction and increases the stereoselectivity. Recycling investigations have shown that this material can be reused, without loss in levels of conversion and stereoselectivity, for at least five cycles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

New materials for L-proline recycling have been developed. These materials have been applied to the L-proline-catalyzed aldol reaction between acetone and several aldehydes. The L-proline has been supported on the surface of modified silica gels with a monolayer of covalently attached ionic liquid with or without additional adsorbed ionic liquid. Good yields and ee values, comparable with those obtained under homogeneous conditions, have been obtained especially with imidazolinium-modified and 4-methylpyridinium-modified silica gels. Moreover, these materials have been easily recovered by simple filtration and studies about their reuse have been carried out. These studies showed that these materials can be used at least up to seven times. Finally, in the case of imidazolinium-modified silica gel, investigations showed that this support can be regenerated giving again a recyclable material with high isolated yields and reproducible ee values up to 13 cycles.

The methoxide‐promoted elimination reaction of some 1,1,1‐trichloro‐2,2‐bis(phenyl‐substituted)ethanes (1) was investigated. The ortho‐substituted derivatives were found to be less reactive than the corresponding ortho‐unsubstituted derivatives, irrespective of the nature of their substituent. The reactivity data were correlated with the 13C NMR chemical shift values of C‐β of either 1,1,1‐trichloro‐2,2‐bis(phenyl‐substituted)ethanes or 1,1‐dichloro‐2,2‐bis(phenyl‐substituted)ethenes and the better result was obtained for the former correlation. Activation parameters for the methoxide‐promoted elimination of 1show very similar values for ortho‐substituted derivatives. The total data set seems to be more indicative, even if not compelling, of an irreversible E1cBmechanism. Copyright © 2001 John Wiley & Sons, Ltd.

The methoxide-promoted elimination reaction of some 1,1,1-trichloro-2,2-bis(phenyl-substituted)ethanes (1) was investigated. The ortho-substituted derivatives were found to be less reactive than the corresponding ortho-unsubstituted derivatives, irrespective of the nature of their substituent. The reactivity data were correlated with the ¹³C NMR chemical shift values of C-β of either 1,1,1-trichloro-2,2-bis(phenyl-substituted)ethanes or 1,1-dichloro-2,2-bis(phenyl-substituted)ethenes and the better result was obtained for the former correlation. Activation parameters for the methoxide-promoted elimination of 1 show very similar values for ortho-substituted derivatives. The total data set seems to be more indicative, even if not compelling, of an irreversible E1cB mechanism. Copyright © 2001 John Wiley & Sons, Ltd.

Nonionic Triton X-100 micelles solubilize the otherwise water-insoluble (Z)-phenylhydrazones of some 5-substituted 3-benzoyl-1,2,4-oxadiazoles to an extent suitable for studying the occurrence of a general-base-catalyzed rearrangement in the presence of borate buffers (pH 9.6). The kinetic data, obtained at 40.0°C over a wide range of surfactant concentrations, are found to conform to a reaction scheme which implies partitioning of the substrates and the base between water and the micellar pseudophase. Evidence that both the rate of the rearrangement reactions and the binding of the substrates to the micellar aggregates are primarily governed by the steric requirements of the 5-substituent group is obtained.

The reactivity of hydroxy selenides with catalytic amounts of perchloric acid in dichloromethane was investigated. Four different cyclisation modes (4-exo, 5-endo, 5-exoand 6-endo) of the intermediate seleniranium ion could occur. The reaction of the hydroxy selenides with primary and secondary hydroxyl groups in the same side chain led first to a mixture of tetrahydrofurans from the 5-exocyclisation (kinetic products), then to a 68/32 mixture of tetrahydropyrans from the 6-endocyclisation (thermodynamic products) probably via two diasteromeric seleniranium ions. Both experimental and ab initio (HF/3-21G∗) studies showed that the order of cyclisation of the intermediate seleniranium ion was 5-exo-tet<6-endo-tet<5-endo-tet<4-exo-tet.The factors on which regiochemistry of the 4-exovs the 5-endocyclisation and the 5-exovs the 6-endocyclisation of the seleniranium ions depend were analysed.

The formation of tetrahydrofurans and tetrahydropyrans by acid catalyzed cyclization of hydroxy selenides can be explained by kinetic and thermodynamic control. The tetrahydropyrans from the hybrid 7-endo6-exocyclization are the thermodynamic products of the acid catalyzed cyclization of hydroxy selenides 1, whereas the tetrahydrofurans from the 5- exocyclization are the kinetic products.

The 13C chemical shifts of the title compounds (1) were determined in CDCl3and in CD3OD as well as in D2SO4solutions. Moreover 17O chemical shifts of 1in CDCl3were measured. The SCS (substituent‐induced chemical shift) values were analyzed by means of linear free energy (LFE) relationships and also by cross‐correlations with those of both the corresponding 5‐substituted 2‐acetylthiophenes (2) and 4‐substituted acetophenones (3). The 13C SCS values indicate a transmission pattern of the substituent effect which is more complex than those observed in 2and 3. On the other hand, the 17O SCS values are more significant and reliable indicators of the transmission of the electronic effects on to the carbonyl group of 1, clearly underlining the different propensities of the phenyl and the thiophen‐2′‐yl groups in accomplishing such a transmission. Some apparent discrepancies observed between protonation and 17O NMR data of compounds 1, 2and 3are also discussed. Copyright © 1999 John Wiley & Sons, Ltd.

The ¹³C chemical shifts of the title compounds (1) were determined in CDCl3 and in CD3OD as well as in D2SO4 solutions. Moreover ¹⁷O chemical shifts of 1 in CDCl3 were measured. The SCS (substituent-induced chemical shift) values were analyzed by means of linear free energy (LFE) relationships and also by cross-correlations with those of both the corresponding 5-substituted 2-acetylthiophenes (2) and 4-substituted acetophenones (3). The ¹³C SCS values indicate a transmission pattern of the substituent effect which is more complex than those observed in 2 and 3. On the other hand, the ¹⁷O SCS values are more significant and reliable indicators of the transmission of the electronic effects on to the carbonyl group of 1, clearly underlining the different propensities of the phenyl and the thiophen-2'-yl groups in accomplishing such a transmission. Some apparent discrepancies observed between protonation and ¹⁷O NMR data of compounds 1, 2 and 3 are also discussed. Copyright © 1999 John Wiley & Sons, Ltd.

As a development of our previous work, we performed a kinetic study of the oxidative cyclization reaction of some 2,4diarylsubstituted aldehyde thiosemicarbazones 1aninduced by ferric chloride and by cupric perchlorate. The results of cyclization of 1anwere compared to those of the corresponding 2methyl derivatives. The kinetic data were analyzed by means of the Hammetts equation.

The base–promoted elimination reactions of 1,1,1‐trichloro‐2,2‐bis(dimethoxyphenyl)ethanes were investigated. The bis(3,4‐dimethoxyphenyl)ethane was found to be more reactive than the bis(2,5‐dimethoxyphenyl)ethane and the latter more reactive than the bis(2,4‐dimethoxyphenyl)ethane. Kinetic data relative to 1,1,1‐trihalo(chloro or bromo)‐2,2‐bis(3,4‐dimethoxyphenyl)ethanes show that the tribromo reacts faster than trichloro derivative and that the reactions are general‐base promoted with Brønsted β values of about 0.6. A kinetic isotope effect, with kH/kDratio ranging from 3.5 to 5.7, for the base‐promoted elimination reaction of 1,1,1‐trichloro‐2,2‐bis(3,4‐dimethoxyphenyl)ethane was found. Tunneling occurs for methoxide and ethoxide ion‐promoted eliminations. Activation parameters for alkoxy‐promoted elimination show a similar trend for chloride and bromide derivatives. The data collected seem to confirm that there is contiguity between E1cBirrand E2 mechanisms. © 1998 John Wiley & Sons, Ltd.

The stereoselective synthesis of a 2substituted tetrahydropyran with adjacent alkoxybearing stereogenic centre is described. The key steps of this synthesis were the stereoselective epoxidation of an allylic alcohol and the regioselective epoxide ring opening by lithium aluminum hydride. The regio and stereoselective synthesis of a trihydroxyselenide and a trihydroxysulfide is also described. The latter compounds are not suitable for cyclization to tetrahydrofuran ring.

The reactivity of some dinitro-benzene and -thiophene derivatives with piperidine and sodium benzenethiolate has been examined giving evidence that benzenes show large and thiophenes show small kinetic secondary steric effects, respectively. The acid dissociation reaction and the UV–VIS spectra of some nitrothiophenamines have also been studied. The crystal structure and the absolute conformation of 2-iodo-3,5-dinitrothiophene and of 2-iodo-4-methyl-3,5-dinitrothiophene have been determined. For different conformations of the analogous chlorodinitro derivatives in the thiophene and benzene series, ab initio energy calculations have been performed. The results collected show that steric strain among adjacent groups affects the benzene and thiophene compounds and the kinetic, thermodynamic and spectroscopic properties of the molecules examined differently. Differences in geometry of the two aromatic rings and then in rotation of nitro groups with respect to the rings themselves as well as differences along reaction coordinates (essentially depending on hybridation changes) are used to explain the above data.

Treatment of benzaldehyde semicarbazones 1a‐iwith cupric perchlorate in acetonitrile at 40 provided selectively the corresponding 1,2,4‐triazolin‐5‐ones 2a‐i. The relative rate constants for 2a‐iformation were determined by the competitive method. The results obtained showed that electron‐donating substituents (methyl and methoxy) increase the reaction rate, while the reverse was found for electron‐withdrawing substituents (chloro and nitro group). The reactivity data are discussed on the grounds of two possible mechanisms.

The base–promoted elimination reactions of 1,1,1-trichloro-2,2-bis(dimethoxyphenyl)ethanes were investigated. The bis(3,4-dimethoxyphenyl)ethane was found to be more reactive than the bis(2,5-dimethoxyphenyl)ethane and the latter more reactive than the bis(2,4-dimethoxyphenyl)ethane. Kinetic data relative to 1,1,1-trihalo(chloro or bromo)-2,2-bis(3,4-dimethoxyphenyl)ethanes show that the tribromo reacts faster than trichloro derivative and that the reactions are general-base promoted with Brønsted β values of about 0.6. A kinetic isotope effect, with kH/kD ratio ranging from 3.5 to 5.7, for the base-promoted elimination reaction of 1,1,1-trichloro-2,2-bis(3,4-dimethoxyphenyl)ethane was found. Tunneling occurs for methoxide and ethoxide ion-promoted eliminations. Activation parameters for alkoxy-promoted elimination show a similar trend for chloride and bromide derivatives. The data collected seem to confirm that there is contiguity between E1cBirr and E2 mechanisms. © 1998 John Wiley & Sons, Ltd.

The reactions beetwen 2,4disubstituted thiosemicarbazides and orthoesters in refluxing xylene led to the formation of the 1,2,4triazoline5thione ring and to the 1,2,4triazolium5thiolate ring. The formation of the mesoionic componds is due to rearrangement of the easily available 2,4disubstituted thiosemicarbazides to 1,4disubstituted thiosemicarbazides under the reaction conditions adopted. This method can be usefully used for the synthesis of mesoionic compounds, especially in the case of the 2methyl4phenylthiosemicarbazide.

The stereoselective rearrangement of tetrahydrofuran or tetrahydropyran rings having a phenylsulfanyl group in an exoposition, viathe intermediate thiiranium ions, is reported. The 5 or 6exotet cyclization of hydroxy sulfides gave the kinetic products while the 6endotet or 5endotet gave the thermodynamic products. The rearrangement of the 5exoproduct to the 6endo one is an interesting way for the stereoselective synthesis of substituted tetrahydropyrans.

An efficient semihydrogenation of CC triple bonds was achieved using palladium on pumice as the catalyst with a metal loading of 3 % wt. The results obtained showed better selectivity when compared with Pd/C and better activity when compared with Lindlar's catalyst. Hydrogenation of sterically hindered alkynes is slow on Pd/pumice. The selectivity with respect to alkenes is probably due to the presence of sodium ions in the pumice structure that increases the electron density on the supported metal.

Review: 148 refs.

Review: 180 refs.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

The cover picture shows the aldol reaction between ketones and arylaldehydes carried out by using a polystyrene-supported L-proline catalyst. This material furnishes aldol products in high yields and stereoselectivities. Screening of solvents showed that these reactions take place only in the presence of water. This solvent effect, coupled with the high stereoselectivities observed, has been explained by the formation of a hydrophobic core in the inner surface of the resin with the hydrophilic proline moiety in the resin/water interface. Such a microenvironment promotes the aldol reaction and increases the stereoselectivity. Recycling investigations have shown that this material can be reused, without loss in conversion and stereoselectivity for, at least, five cycles. This catalyst can be considered a better mimic of natural Class I aldolase enzymes that use an enamine-mediated mechanism in water. Details are discussed in the article by M. Gruttadauria et al. on p. 4688 ff. This work is dedicated to Professor Domenico Spinelli on the occasion of his 75th birthday.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

For Abstract see ChemInform Abstract in Full Text.