Well-defined Cu(I) complexes based on [N,P]-pyrrole ligands catalyzed a highly endoselective 1,3-dipolar cycloaddition.

We herein report the synthesis and catalytic application of a new family of dinuclear Cu(I) complexes based on [N,P]-pyrrole ligands. The Cu(I) complexes (4a-d) were obtained in good yields and their catalytic properties were evaluated in the1,3-dipolar cycloaddition of azomethine ylides and electron-deficient alkenes. The air-stable complexes 4a-d exhibited high endo-diasteroselectivity to obtain substituted pyrrolidines, and the catalytic system showed excellent reactivity and wide substitution tolerance.

Synthesis of (µ2,η3-allyl-η5-oxapentadienyl)diiron pentacarbonyl complexes, an unusual reaction product from η4-(vinylketene)Fe(CO)3 complexes: structure and electron density distribution analysis.

The synthesis of a series of ferrocenylvinylketenes as stable η4-[Fe(CO)3] complexes (3a-f) was successfully accomplished through the reaction of η2-[Fe(CO)4] complexes under mild carbonylation conditions. The reactivity of 3a-f under thermal conditions afforded the unexpected formation of a novel family of (µ2,η3-allyl-η5-oxapentadienyl)diiron pentacarbonyl complexes 5a-f proposed to be formed by a sequence metathesis-haptotropic rearrangement between the starting η4-vinylketene iron(0) complex 3 and a η4-vinylcarbene iron(0) complex trapped in situ after a reversible carbonylation process favored by the thermal conditions. An electron density distribution analysis (EDD) of 5e using high-resolution X-ray diffraction data in combination with the DFT framework was performed to understand the electronic communication between the two iron fragments.

Iodine-promoted insertion of the oxygen atom from water in η4-vinylketene[Fe(CO)3] complexes.

Iodine promotes the in situ formation of iron(II) species from η4-vinylketene[Fe(CO)3] (3a-h) as a key intermediate for the synthesis of 2(5H)-furanones (4a-h) by a sequential water-insertion/carbon-oxygen coupling under mild reaction conditions. Compounds 4a-h were obtained in good to excellent yields. A possible reaction pathway was also proposed by DFT calculations. This methodology can be extended to the synthesis of (5H)-pyrrol-2-ones using anilines, with moderate yields and a few limitations.

Interrupted Intramolecular Hydroaminomethylation of N-Protected-2-vinyl Anilines: Novel Access to 3-Substitued Indoles or Indoline-2-ols.

A new synthetic alternative to the synthesis of 3-methyl indoles and 3-methyl indoline-2-ols with an excellent atomic economy is presented in this study. It is demonstrated that the intramolecular interrupted hydroaminomethylation (HAM) reaction is a powerful tool for the formation of these compounds, which exhibit wide-ranging biological activity. Several N-Protected-2-vinyl anilines were synthesized and involved in the reaction producing the corresponding 3-methylindole or 3-methyl indoline-2-ol depending on the nature of the N-protecting groups.

2-Thiazolines: an update on synthetic methods and catalysis.

2-Thiazolines are important building blocks in organic synthesis and are of great importance in many areas of chemistry. At the end of the last century, the use of 2-thiazolines increased in a significant way, especially in synthesis and catalysis. This review highlights the synthetic and catalytic value of 2-thiazolines in the last two decades. We will discuss the new synthetic methodologies for obtaining these heterocycles including new schemes for accessing their asymmetric versions. Most of the new catalytic applications include a variety of 2-thiazoline ligands containing diverse donor atoms, which in combination with metals like Pd, Ir, and Cu, among others, exhibit remarkable catalytic performances.

Two-photon induced isomerization through a cyaninic molecular antenna in azo compounds.

We present a new design for non-linear optically responsive molecules based on a modular scheme where a polymethinic antenna section with important two-photon absorption properties is bonded to an isomerizable actuator section composed of a stilbenyl-azopyrrole unit. Upon two photon excitation, energy migration from the antenna-localized second singlet excited state to the stilbenyl-azopyrrole section allows for efficient indirect excitation and phototransformation of this actuator.

Aluminum complexes with new non-symmetric ferrocenyl amidine ligands and their application in CO2 transformation into cyclic carbonates.

A set of alkyl aluminum complexes supported by non-symmetric ferrocenyl amidine ligands were used as catalysts for the preparation of cyclic carbonates from epoxides and carbon dioxide using Bu4NI as a co-catalyst. A modified method for the synthesis of aminoferrocene allowed us to obtain this precursor in quantitative yield. Treatment of aminoferrocene with the corresponding acetimidoyl chloride afforded the desired ferrocenyl amidine ligands L1H, (E)-N-(2,6-diisopropylphenyl)-N'-(ferrocenyl)acetimidamide, and L2H, (E)-N-(2,6-dimethylphenyl)-N'-(ferrocenyl)acetimidamide. The reaction of these ligands with 1.0 or 0.5 equiv. of AlMe3 led to the synthesis of aminoferrocene based aluminum complexes ((L1)AlMe2 (1), (L2)AlMe2 (2), (L1)2AlMe (3), and (L2)2AlMe (4)) in excellent yields, which were characterized by spectroscopic and X-ray diffraction methods. In addition, we have studied their electrochemical properties and complex 1 was found to be the most active catalyst for the formation of cyclic carbonates 6a-j from their corresponding epoxides 5a-j and CO2.

Development of rosemary essential oil nanoemulsions using a wheat biomass-derived surfactant.

In the present work aqueous-based emulsions formulated with bio-based solvents and surfactants were studied. The droplet size distribution, rheology and physical stability of rosemary essential oil/water emulsions formulated with an emulsifier derived from wheat waste (alkyl polypentoside) were investigated as a function of the dispersed phase concentration (10-50 wt%) by means of laser diffraction, multiple light scattering and rheology measurements. Subsequently, processing variables, such as the pressure and the number of microfluidization passes, were studied to the best formulation (20 wt% rosemary oil). The laser diffraction technique revealed that monodispersed submicron emulsions were obtained for oil phase concentrations below 20 wt%. All emulsions showed Newtonian behavior, except for the emulsion containing 50 wt% oil, which exhibited shear-thinning properties. Moreover, the main destabilization mechanism of all the emulsions was creaming. The combination of techniques used demonstrated that the emulsion containing 20 wt% rosemary essential oil (REO) and prepared by microfluidization at 2500 psi (17.2 MPa) exhibited the longest physical stability and the smallest droplet size after 3passes. This research is a contribution to sustainable development not only by using chemicals derived from renewable raw materials but also by achieving stable emulsions with a low surfactant/oil mass ratio.

Effect of temperature and shear on the microstructure of a microbial polysaccharide secreted by Sphingomonas species in aqueous solution.

Diutan gum is a biological polymer produced by Sphingomonas sp. In aqueous solution it shows gel-like structure under quiescent conditions. However, the flow-induced evolution of its viscoelastic properties and its microstructure are not known. In this work, the viscoelastic moduli were obtained under a flow field, applied in parallel, as a function of the temperature for 0.5 wt% diutan gum aqueous solutions. As both stress and temperature increase a decrease in the viscoelastic properties occurred, due to the fact that the molecular interactions decreased. Nevertheless, at stresses within the zero-shear viscosity region of the flow curves, no changes were observed. In addition, high stress values dampened the effect of the temperature. The results obtained are very interesting from an industrial application perspective.

Rheology of sheared gels based on low acyl-gellan gum.

Sheared gels containing 0.2 wt% low-acyl gellan gum were prepared by different processing protocols using Na(+) or Ca(2+) as gel-promoting ions. Rheology and confocal laser scanning microscopy were used to gain information on the sample structure. Confocal laser scanning microscopy revealed the formation of a heterogeneous microstructure consisting of a dispersion of gel-like clusters. Small amplitude oscillatory shear stress results indicated that their viscoelastic properties had a predominant elastic component. Flow curves exhibited very high viscosities at low shear stress, an apparent yield stress and very shear thinning behaviour, supporting their applications as a stabilizer.

Nanostructured Thin Films Obtained from Fischer Aminocarbene Complexes.

The synthesis of four amphiphilic organometallic complexes with the general formula RC = M(CO)5NH(CH2)15CH3, where R is a ferrocenyl 2(a-b) or a phenyl 4(a-b) group as a donor moiety and a Fischer carbene of chromium (0) or tungsten (0) as an acceptor group, are reported. These four push-pull systems formed Langmuir (L) monolayers at the air-water interface, which were characterized by isotherms of surface pressure versus molecular area and compression/expansion cycles (hysteresis curves); Brewster angle microscopic images were also obtained. By using the Langmuir-Blodgett (LB) method, molecular monolayers were transferred onto glass substrates forming Z-type multilayers. LB films were characterized through ultraviolet-visible spectroscopy, atomic force microscopy and X-ray diffraction techniques. Results indicated that films obtained from 2b complex [(Ferrocenyl)(hexadecylamine)methylidene] pentacarbonyl tungsten (0) are the most stable and homogeneous; due to their properties, these materials may be incorporated into organic electronic devices.

An expedient approach to synthesize fluorescent 3-substituted 4H-quinolizin-4-ones via (η(4)-vinylketene)-Fe(CO)3 complexes.

An efficient and practical methodology for the synthesis of 3-substituted 4H-quinolizin-4-ones using (η(4)-vinylketene)-Fe(CO)3 complexes as key intermediates has been developed. The advantage of this transformation lies in the use of simple and readily available starting materials and mild carbonylation conditions. The fluorescent properties of these compounds were determined and the quantum yield was obtained, ranging from 0.04 to 0.36 depending on the substituent.

2-Ferrocenyl-2-thiazoline as a building block of novel phosphine-free ligands.

New 1,2-disubstituted ferrocenes [5(b-j), in which R = -SMe, -SPh, -SiPr, -SiMe3, -SePh, -SnBu3, -B(OH)2, -Me, -I] with a thiazoline ring in the ferrocene backbone using as key intermediate a ferrocenyl Fischer carbene complex were synthesized. The capability of the 2-thiazoline moiety as an ortho-directed metalation group was demonstrated by subsequent quenching of lithium intermediate with several electrophiles, proving to be an excellent method for synthesizing bidentate ligands. The catalytic scope of the [N,S] ligand 5b as the corresponding palladium complex 5b-PdCl(2) in a microwave-promoted Heck reaction was also tested. Results obtained showed better catalytic activity of 5b-PdCl(2) compared to other catalytic systems based on a [N,S] ferrocenyl ligand.

Synthesis of Fischer type-carbene complexes containing a coordinated thioimidate structural motif.

This paper describes a tandem strategy to synthesize a series of new Fischer carbene complexes [(CO)(4)M=C[N-(CH(2))(4)-]CH=C(NRR')(SR'); M = Cr, W; R = Ar, R' = Me, -(CH(2))(2)-] with a thioimide or thiazoline fragment, in which the sulfur or nitrogen atom is coordinated to a metal center, depending on the nature of alkylating groups included as R'. We have trapped by protonation the proposed intermediate as the thioamide 12 [(CO)(5)W=[N-(CH(2))(4)-]CH(2)C(S)NHPh], which reveals the pathway of this reaction.

Ferrocenylselenoamides: synthesis, characterization and cytotoxic properties.

A new series of ferrocenyl selenoamides 7-11 (FcSeNH(CH(2))(n)CH(2)(R)OH, n = 1, 2, 3, R = H, Me, Ph) were prepared in good yields by selenative demetalation of Fischer aminocarbene complexes. The crystal structures of 7 [FcSeNH(CH(2))(2)OH] and 19 [PhSeNH(CH(2))(2)OH] reveal their capability to form intermolecular hydrogen bonding in solid state. Results of SRB assays show that these new selenium compounds have a good anticancer potency superior to tamoxifen and cisplatin, with IC(50) values ranging from 4.5 to 13.32 µM against human breast cancer cell lines. A preliminary model to explain the structure-cytotoxic activity relation is proposed where different structural parameters such as the alkyl chain length, the presence of bulky groups in the same chain, the effect of hydroxyl group, and also the role of ferrocene moiety are included as being responsible for the cytotoxic response.

Synthesis, characterization, and tautomerism of four novel copper(I) complexes from 3-hydroxy-3-(p-R-phenyl)-2-propenedithioic acids.

The paper describes the synthesis and structural characterization of four novel copper(I) complexes [CuL(PPh(3))(2)] (L = 3-hydroxy-3-(p-R-phenyl)-2-propenedithioate). In addition, a tautomeric equilibrium in solution was found and Hammett correlations with (13)C NMR parameters were studied. The structure of one complex was fully established by X-ray diffraction analysis.