Linear polyisophthalamides from the trifunctional monomer 5-hydroxyisophthalic acid. A convenient approach towards functionalized aromatic polymers

Wholly aromatic polyisophthalamides (PIPAs) containing free hydroxylic groups were prepared from 5-hydroxyisophthalic acid and sulfonyldianiline by the condensation phosphorylation method, using triphenylphosphite as a condensing agent, in the presence of pyridine. Linear polymers were attained in high yield and high molecular weight, and the properties of the polymers were investigated in comparison with homologous polyisophthalamides without OH groups. The presence of OH groups did not much modified the solubility of hydroxyl-containing polyisophthalamides as they behaved against common solvents in a similar manner as that of reference polyisophthalamides. However, hydroxyl side groups greatly enhanced the water affinity of polyisophthalamides, which showed up to 16% water uptake in 98% relative humidity, and contact angles about 10° smaller than those of classical PIPAs. The presence of free OH groups slightly diminished the thermal resistance, as evaluated by TGA, but the glass transition temperatures were higher by 20–30 °C, with a maximum of 345 °C. The mechanical properties of hydroxyl-containing polyisophthalamides were reasonably acceptable, with modulus around 2000 MPa and tensile strength up to 60 MPa.     

A fully conjugated TTF-π-TCAQ system: synthesis, structure, and electronic properties

The synthesis of the first fully conjugated tetrathiafulvalene–tetracyano‐p‐quinodimethane ((TTF)–TCNQ)‐type system has been carried out by means of a Julia–Kocienski olefination reaction. In particular, a tetracyanoanthraquinodimethane (TCAQ) formyl derivative and two new sulfonylmethyl‐exTTFs (exTTF=2‐[9‐(1,3‐dithiol‐2‐ylidene)anthracen‐10(9H)‐ylidene]‐1,3‐dithiole)—prepared as new building blocks—were linked. A variety of experimental conditions reveal that the use of sodium hexamethyldisilazane (NaHMDS) as base in THF afforded the E olefins with excellent stereoselectivity. Theoretical calculations at the B3LYP/6‐31G** level point to highly distorted exTTF and TCAQ that form an almost planar stilbene unit between them. Although calculations predicted appreciable electronic communication between the donor and the acceptor, cyclic voltammetric studies did not substantiate this effect. It was only in photophysical assays that the electronic communication emerged in the form of a charge‐transfer (CT) absorption and emission. Once photoexcited (i.e., the locally excited state or excited charge‐transfer state), an ultrafast, subpicosecond charge separation leads to a radical ion pair state in which the spectroscopic features of the radical cation of exTTF as well as the radical anion of TCAQ are discernable. The radical ion pair is metastable and undergoes a fast ((1.0±0.2) ps) charge recombination to reconstitute the electronic ground state. Such ultrafast charge separation and recombination processes come as a consequence of the very short vinyl linkage between the two electroactive units.     

Silver-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with β-boryl acrylates

The Ag-catalyzed 1,3-dipolar cycloaddition of (Ε)-β-borylacrylates with azomethine ylides is described. The resulting 3-borylpyrrolidine derivatives were obtained in high yields and complete endo selectivities using AgOAc/dppe as catalyst system and B(dam) as boryl group. Transformation of the B(dam) group into pinacol borane and oxidation afforded 3-hydroxyproline derivatives in high yields.     

Novel dipolarophiles and dipoles in the metal-catalyzed enantioselective 1,3-dipolar cycloaddition of azomethine ylides

The catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides constitutes one of the most powerful and atom economical methods for the enantioselective construction of pyrrolidines. This article highlights the recent developments in this area, with special focus on contributions improving the structural scope at the dipolarophile and azomethine ylide partners.     

Voltammetric Electronic Tongue for the Qualitative Analysis of Beers

This paper deals with the application of a voltammetric electronic tongue (ET) towards beers classification. For this purpose, samples were analyzed using cyclic voltammetry without performing any sample pretreatment, albeit its dilution with distilled water. The voltammetric signals were first preprocessed employing Fast Fourier Transform (FFT). Then, using the obtained coefficients, responses were evaluated using three different clustering techniques: Principal Component Analysis (PCA), Partial Least Squares Discriminant Analysis (PLS‐DA) and Linear Discriminant Analysis (LDA). In this case, the ET has demonstrated a good capability to correctly discriminate and classify the different beer samples according to its type (Lager, Stout and IPA) and manufacture process (commercial and craft).     

Bis-sulfonyl ethylene as masked acetylene equivalent in catalytic asymmetric [3 + 2] cycloaddition of azomethine ylides

Enantioenriched 3-pyrrolines have been synthesized by highly enantioselective Fesulphos-Cu-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with trans-1,2-bisphenylsulfonyl ethylene, followed by reductive sulfonyl elimination. High levels of reactivity, exoselectivity, and enantioselectivity have been accomplished for a variety of substituted azomethine ylides. This cycloaddition-desulfonylation strategy has been applied as a key step in the enantioselective synthesis of a biologically active C-azanucleoside.     

Cu-catalyzed asymmetric [3+2] cycloaddition of α-iminoamides with activated olefins

A variety of 2-amido pyrrolidines, including Weinreb-type amides, have been prepared with very high exo diastereoselectivity and enantioselectivitiy in the reaction of α-iminoamides with activated alkenes catalyzed by Cu(I)-Segphos ligands.     

Catalytic asymmetric Mannich reaction of glycine Schiff bases with α-amido sulfones as precursors of aliphatic imines

A general and practical Cu(I)-Fesulphos-catalyzed Mannich reaction of glycinate Schiff bases with aliphatic imines generated in situ from α-amido sulfones is described. Imines with linear and branched alkyl chains, including substrates bearing functional groups, can be efficiently applied. The resulting syn-configured orthogonally protected β-alkyl-α,β-diamino acid derivatives are produced with excellent levels of diastereo- (typically syn/anti >90?:?<10) and enantioselectivity (generally ≥90% ee).     

2D supramolecular assemblies of benzene-1,3,5-triyl-tribenzoic acid: temperature-induced phase transformations and hierarchical organization with macrocyclic molecules

Two-dimensional supramolecular honeycomb networks with cavities of an internal diameter of 2.95 nm were formed by the self-assembly of 4,4',4' '-benzene-1,3,5-triyl-tribenzoic acid (BTA) on a Ag(111) surface at room temperature. Annealing to higher temperatures resulted in two sequential phase transformations into closer-packed supramolecular arrangements. The phase transformations are associated with stepwise deprotonation of the carboxylic acid groups. The voids of the honeycomb network of BTA have a suitable size for the construction of hierarchical structures with guest molecules. Single molecules of the macrocyclic compound mt-33 were successfully confined inside 2D nanocavities of the honeycomb networks and released when the phase was transformed to the close-packed structure.     

Gold-catalyzed synthesis of alkylidene 2-oxazolidinones and 1,3-oxazin-2-ones

N-Boc-protected alkynylamines are converted into the corresponding alkylidene 2-oxazolidinones or 2-oxazinones under very mild reaction conditions in the presence of 1-5 mol % of a cationic Au(I) complex. The scope of the reaction is very general, providing the cyclic carbamates in high yield regardless of the substitution at nitrogen and alkyne terminus.