Carolina S. Marques

Toxicity assessment of various ionic liquid families towards Vibrio fischeri marine bacteria

The increasing interest on the application of ionic liquids (ILs) to a wide range of processes and products has been hampered by a lack of toxicological data, mainly in what concerns novel cations, such as guanidinium, phosphonium, and functionalized and non-functionalized imidazolium-based ILs. The present study reports the toxicity of five guanidinium-, six phosphonium, and six imidazolium-based ILs, towards the luminescent marine bacteria Vibrio fischeri. These new results clearly show that guanidinium-, unlike the imidazolium- and phosphonium-based ILs, do not follow the trend of increasing toxicity with the increase in the alkyl chain length. Moreover, the introduction of oxygenated groups on the alkyl chains, such as ether and ester, leads to a decrease of the toxicity of guanidinium and also imidazolium compounds. In what respects the effect of the different cations, it is possible to recognize that the phosphonium-based ILs seem to be more toxic when compared to the analog imidazolium-based ILs (with the same anion and alkyl chains).

Advances in the Catalytic Asymmetric Arylation of Imines using Organoboron Reagents: An Approach to Chiral Arylamines

The production of chiral amines by means of catalytic asymmetric synthesis is a current challenge in the field of drug discovery and is discussed in this review. The use of cheap, easily handled, and low toxic organoboron reagents, such as boronic acids and derivatives, and easily prepared imine substrates, such as diphenylphosphinoyl, N‐Boc, N‐tosylaryl, N‐nosylaryl, or dimethylsulfamoyl imines, together with rhodium and palladium catalysts give the corresponding chiral amine products in excellent yields and enantioselectivities. A diverse range of chiral ligands, such as phosphines, phosphites, phosphoramidites, P,O‐ligands, olefins, NHCs, and N,N‐ligands can be used with this method, showing, therefore, its versatility. The application of aliphatic imine substrates and with the use of different palladium complexes show, on the other hand, the versatility of the method described.

Toxicological evaluation on human colon carcinoma cell line (CaCo-2) of ionic liquids based on imidazolium, guanidinium, ammonium, phosphonium, pyridinium and pyrrolidinium cations

Toxicological evaluation of a new group of ionic liquids was performed on human colon cancerous cells—CaCo-2. They belong to different classes of cations: imidazolium (IM), dimethyl-guanidinium (dmg) and tetramethyl-guanidinium (tmg), methyl-pyrrolidinium (MPyr), 2-methyl-1-ethyl-pyridinium (2-MEPy), quaternary ammonium (benzyltriethyl-ammonium–BzTEA; phenyltrimethyl-ammonium–PhTMA; tri-n-octyl-methylammonium-Aliquat) and tri-n-hexyl-tetra-n-decylphosphonium (P6,6,6,14). The new results were compared with data obtained in previous reported studies performed in our lab, and we clearly saw that toxicity can vary significantly with the type of anion. Dicyanoamide-[DCA] and bis(trifluoromethanesulfonyl)amide-[NTf2] were seen to visibly change the impact of some cations. Some were considerably less harmful for CaCo-2 monolayer when the anion was [DCA] or [NTf2], while others induced an abnormal increase of cellular metabolism when [NTf2] was present and therefore, they were considered toxic. However, some cations induced similar responses in the presence of a broad number of anions as (1-butyl-3-methylimidazolium)-[C4MIM] (with the exception of [FeCl4]), (1-(2-hydroxyethyl)-3-methylimidazolium)-[C2OHMIM] and [C4MPyr] and did not cause toxicity. Consequently, they are considered promising cations for building human friendlier solvents. But, a reasonable number of other combinations involving different classes of cations were also seen to not significantly affect viability of the CaCo-2 monolayer.

Asymmetric catalytic arylation of ethyl glyoxylate using organoboron reagents and Rh(I)–phosphane and phosphane–phosphite catalysts

Herein we report the first application of Rh(I)–phosphane and phosphane–phosphite catalysts in the enantioselective catalytic arylation of ethyl glyoxylate with organoboron reagents, providing access to ethyl mandelate derivatives in high yield (up to 99%) and moderate to very good enantioselectivities (up to 75% ee). Commercial phosphane ligands, such as (R)-MonoPhos and (R)-Phanephos were tested, as well as non-commercial (R,R)-TADDOL-derived phosphane–phosphite ligands. Those ligands containing bulky substituents in the ortho-and para-positions of the chiral phosphite moiety were found to be the most selective.

Catalytic arylation methods : from the academic lab to industrial processes

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Rh(I)-Catalyzed Asymmetric Hydrosilylation and Hydroboration/Oxidation Reactions Using Berens Ligand

Abstract The Berens ligand 2 was used in a number of Rh(I)-catalyzed asymmetric hydrosilylations of acetophenones under standard conditions, affording the corresponding 1-arylalcohols in ees up to 65%. Some novel Rh catalysts were generated in situ from the neutral precatalyst [Rh(µ-Cl)(COD)]2 and screened in the catalytic asymmetric hydroboration/oxidation of styrenes, gave enantioselectivities of up to 62%.

New cholinesterase inhibitors for Alzheimer's disease: Structure Activity Studies (SARs) and molecular docking of isoquinolone and azepanone derivatives.

A library of isoquinolinone and azepanone derivatives were screened for both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activity. The strategy adopted included (a) in vitro biological assays, against eel AChE (EeAChE) and equine serum BuChE (EqBuChE) in order to determine the compounds IC50 and their dose-response activity, consolidated by (b) molecular docking studies to evaluate the docking poses and interatomic interactions in the case of the hit compounds, validated by STD-NMR studies. Compound (1f) was identified as one of these hits with an IC50 of 89.5μM for EeAChE and 153.8μM for EqBuChE, (2a) was identified as a second hit with an IC50 of 108.4μM (EeAChE) and 277.8μM (EqBuChE). In order to gain insights into the binding mode and principle active site interactions of these molecules, (R)-(1f) along with 3 other analogues (also as the R-enantiomer) were docked into both RhAChE and hBuChE models. Galantamine was used as the benchmark. The docking study was validated by performing an STD-NMR study of (1f) with EeAChE using galantamine as the benchmark.

Transition-metal-catalyzed intramolecular cyclization of amido(hetero)arylboronic acid aldehydes to isoquinolinones and derivatives

We report an innovative and simple three step high yielding synthesis of a library of 14 chiral isoquinolinone and azepinone derivatives with benzyl, pyridyl and thiophene cores starting from amidoarylboronic acid aldehydes. These products have potential for treating neurodegenerative diseases. The key reaction in this synthetic pathway was an efficient metal-catalyzed (with Rh, Cu and Pd catalysts) intramolecular cyclization. A maximum yield of 87% was obtained using a Rh(I) catalyst.

New Route to N‐Alkylated trans‐Pyrrolidine Diols from 2,2,3,3‐Tetramethoxybutane‐Protected Dimethyl Tartrate

Abstract A short synthesis of some trans‐pyrrolidine diols is described starting from (2R,3R,5R,6R)‐5,6‐dimethoxy‐5,6‐dimethyl[1,4]dioxane‐2,3‐dicarboxylic acid dimethyl ester 3. The key step was the occurrence of a tandem azide reduction/cyclization sequence on mono‐azide intermediate 6 upon catalytic hydrogenation. This method afforded both (3R,4R)‐(+)‐1‐benzyl‐3,4‐pyrrolidinediol 9a and (3R,4R)‐(+)‐1‐allyl‐3,4‐pyrrolidinediol 9b starting from 3. Cytotoxicity tests were performed on compounds 9a and 9b using the brine shrimp bioassay, but each showed no activity, as were anti‐oxidant tests using the stable free radical diphenylpicrylhydrazyl (DPPH).

Enantioselective Rh(I)‐Catalyzed additions of arylboronic acids to N‐1,2,3‐Triazole‐Isatin Derivatives: Accesing N‐(1,2,3‐Triazolmethyl)‐3‐Hydroxy‐3‐aryloxindoles

Oxindoles and triazoles are very privileged frameworks in medicinal chemistry, and thus for the first time we report a catalytic asymmetric route that affords hitherto unknown families of N‐(1,2,3‐triazolmethyl)‐3‐hydroxy‐3‐phenyloxindoles using cheap biomass‐derived isatin precursors, rhodium catalysts (at only 3 mol % loading), phosphane ligands, and arylboron reagents under mild conditions. We successfully obtained these compounds with good yields (up to 98 % in the nonasymmetric series) and enantioselectivities in the range 84–95 % ee. The reaction is very versatile, tolerant of a wide range of functional groups, and broad in reaction scope.