Maria Rosaria Acocella

A convenient catalytic procedure for the highly enantioselective aldol condensation of O-silyldienolates

Abstract In the presence of catalytic amount of chiral Ti(OiPr)4/BINOL (0.08 equiv.) the asymmetric aldol condensation of 6-methyl-4H-[1,3]-dioxin-4-one-derived silyloxydienes takes place in high yields and enantiomeric excesses with aromatic, heteroaromatic, unsaturated and aliphatic aldehydes. Notable amplification of enantiomeric excesses have been obtained by using enantioenriched catalytic systems.

Regio- and enantioselective friedel-crafts reactions of indoles to epoxides catalyzed by graphene oxide: a green approach.

Graphene oxide efficiently promotes high regio- and enantioselective ring opening reactions of aromatic epoxides by indoles addition, in solvent- and metal-free conditions. The Friedel-Crafts products were obtained with enantioselectivity up to 99 % ee. The complete inversion of stereochemistry indicates the occurrence of SN 2-type reaction, which assures high level of enantioselectivity.

Asymmetric Friedel-Crafts Alkylation of Indole with Chalcones Catalyzed by Chiral Phosphoric Acids

The reaction of indole with chalcones, to give Michael-type adducts, was found to occur with good efficiency (up to 98% yield) and moderate enantioselectivity (up to 52% e.e.) in the presence of a chiral BINOL-based phosphoric acid. Furthermore, the alkylation products can be obtained in much higher e.e.s after one only crystallization.

Graphene oxide as a catalyst for ring opening reactions in amine crosslinking of epoxy resins

The influence of different graphite-based nanofillers on epoxide ring opening reactions, as induced by amines for diglycidyl ether of bisphenol A (DGEBA), is studied. Direct kinetic studies, with full chemical characterization and quantitative evaluation of the low molecular mass products, for reactions of DGEBA with primary and secondary monoamines as well with alcohols, are conducted. Moreover, the kinetic behavior of a commercial epoxy resin based on DGEBA and a diamine, leading to crosslinked insoluble networks, is studied by indirect methods, such as differential scanning calorimetry (DSC) and rheometry. The reported results show a relevant catalytic activity of graphene oxide on epoxy resin crosslinking by amines. For instance, for a graphene oxide content of 3 wt%, the exothermic crosslinking DSC peak is shifted (upon heating at 10 °C min−1) from 113 °C down to 96 °C, while the gel time at 50 °C is reduced by a factor of 2.5. This behavior is due to the ability of graphene oxide to catalyze primary amine–epoxy, secondary amine–epoxy and mainly hydroxyl–epoxy additions.

Ti(IV)/BINOL-catalyzed asymmetric aldol reaction of a masked acetoacetic ester: pronounced influence of catalyst concentration on nonlinear effects

Initial concentration of enantioenriched or enantiopure catalysts proved to be an important factor for the achievement of a more pronounced amplification of ees in the Ti(IV)/BINOL-catalyzed aldol reaction of an O-silyldienolate.

Asymmetric auto-inductive aldol reaction by self-assembly of chiral ligands

Abstract The Ti(IV)/( R )-BINOL catalyzed aldol condensation of trimethylsilyloxydiene, deriving from 2,2,6-trimethyl-4H-[1,3]-dioxin-4-one, is shown to proceed through an auto-inductive process with amplification of enantiomeric excess (e.e.).

Mo(CO)6-Catalyzed oxidation of furan derivatives to E- and Z-enediones by cumyl hydroperoxide

Abstract E- and Z-Enediones are easily accessible by controlled oxidation of 2,5-disubstituted furans with Mo(CO)6/cumyl hydroperoxide system. The use of t-butyl hydroperoxide, as oxygen donor, leads to the formation of 2H-pyran-3(6H)-one derivatives.

Green Regio‐ and Enantioselective Aminolysis Catalyzed by Graphite and Graphene Oxide under Solvent‐Free Conditions

The ring‐opening reactions of epoxides with amines were efficiently and regioselectively catalyzed by high‐surface‐area graphite and graphene oxide under metal‐free and solvent‐free conditions. For epoxides without aryl groups, catalytic activity was observed only for graphene oxide, and hence, the activity must have been due to its acidic groups. For styrene oxide, instead, graphite and graphene oxide exhibited rather similar catalytic activities, and hence, the activity was mainly due to activation of the electrophilic epoxide by π‐stacking interactions with the graphitic π system. The described aminolysis procedure is green and cheap because the catalyst can be recovered and recycled without loss of efficiency. Moreover, these heterogeneous catalysts exert high stereoselective control in the presence of nonracemic epoxides and provide chiral β‐amino alcohols with enantiomeric excess values up to 99 %.

Thermally stable, solvent resistant and flexible graphene oxide paper

The ability of graphene oxide (GO) aqueous suspensions to form robust GO paper is largely improved by basification of the suspension before processing. In particular, casting procedures, which are generally unsuitable for production of robust GO paper, become suitable for basified GO (b-GO) suspensions, leading to dense and free-standing papers, which are also highly flexible. Thermal or microwave treatments of paper from b-GO suspensions (b-GO paper) easily produce loss in stacking order of graphene oxide layers, with maintenance of a high degree of parallelism (0.6 < f ≡ orientation function < 0.7) with respect to the paper surface. Differently from usual GO papers, b-GO papers maintain their dimensional integrity when thermally treated or when dispersed in organic solvents or in aqueous solutions. Many relevant b-GO features (improved film ability by casting, maintenance of film integrity and reduced deoxygenation by heating and improved solvent resistance) can be rationalized by formation of covalent bridges between GO layers. Infrared spectra and simple chemical arguments suggest that these covalent bridges between GO layers could be mainly constituted by ether bonds.

Intercalation compounds of oxidized carbon black

Oxidation studies on carbon black (CB) show that the degree of oxidation largely increases with initial BET surface areas. WAXD patterns suggest that oCB samples are mainly constituted by a disordered spatial arrangement of highly defective graphene oxide structural layers, with short in-plane correlation length (2–3 nm). This is confirmed by the ability of oCB to form ordered intercalation compounds, as for the first time reported here. In fact, tetraalkylammonium cations in which two of the alkyl groups possess long hydrocarbon tails (2HT) are able to induce formation of intercalate crystalline structures not only by ion exchange in ordered GO crystals but also by self-assembling with small and disordered oCB layers. WAXD patterns of oCB/2HT adducts show few 00l reflections, indicating formation of an intercalate structure with a spacing between graphitic layers of 4.8 nm, as well as a diffraction peak at d = 0.42 nm, indicating the occurrence of a hexagonal rotator order of the intercalated hydrocarbon chains. The spacing between graphitic layers for oCB/2HT adducts (4.8 nm) is definitely higher than for the analogous GO/2HT adducts (3.4 nm) and corresponds to an orientation of the hydrocarbon tails nearly perpendicular to graphene planes.