Positive Solutions for Nonlinear Periodic Problems with the Scalar p-Laplacian

We study the existence of positive solutions for a nonlinear periodic problem driven by the scalar p-Laplacian and having a nonsmooth potential. We impose a nonuniform nonresonance condition at +?∞ and a uniform nonresonance condition at 0^?+?. Using degree theoretic argument based on a fixed point index for multifunctions, we prove the existence of a strict positive solution.     

6-(Arylvinylene)-3-pyridinylboronic esters. Part 1: Versatile building blocks for conjugated chromophores via Suzuki cross-coupling

This paper describes a general approach for the synthesis of conjugated 6,6′-disubstituted-3,3′-bipyridine chromophores. As preliminary results, 6-(4-hexyl-2-thienylvinylene)-5-methyl-3-bromopyridine, 6-(4-ethanol-2-thienylvinylene)-5-methyl-3-bromopyridine, and the corresponding 3-pyridinylboronic esters have been prepared. Coupled by Suzuki reaction, they gave the conjugated chromophores (I) and (II) in high yields and multigram scales.     

Non-defluorinative electrochemical silylation of ethyl trifluoroacetate: a practical synthesis of trifluoroacetyltrimethylsilane via its ethyltrimethylsilyl ketal

An efficient method for the preparation of original trifluoroacetyltrimethylsilane, CF₃COSiMe₃ (3), in two steps from readily available ethyl trifluoroacetate is described. Electrochemical reduction of this ester using a sacrificial anode and performed on a semimolar scale afforded the unprecedented corresponding ketal, CF₃C(SiMe₃)(OSiMe₃)OEt (2) in 30-56% isolated yield. Treated with concentrated sulphuric acid at room temperature, the latter directly led to pure acylsilane 3 in 86% yield.     

6-(Arylvinylene)-3-pyridinylboronic esters. Part 2: Versatile building blocks for push-pull nonlinear optical chromophores

This paper describes a general approach for the synthesis of push-pull 6,6′-disubstituted-3,3′-bipyridine chromophores. As examples, 6-(4-ethanol-2-thienylvinylene)-5-methyl-3-bromopyridine, 6-(4-hydroxy-phenylvinylene)-5-methyl-3-bromopyridine, and the corresponding 3-pyridinylboronic esters have been prepared as building blocks end-capped with electron donor groups (D). 6-(4-Cyano-phenylvinylene)-5-methyl-3-bromopyridine, and 6-(4-cyano-phenylvinylene)-3-bromopyridine have been synthesized as building blocks end-capped with electron acceptor groups (A). {A x D} type cross-couplings via Suzuki reaction gave the push-pull chromophores (I) and (II) in high yields and multigram scales.     

Synthesis of amphiphilic phenylazophenyl glycosides and a study of their liquid crystal properties

Several 4-(4'-N,N-didodecylaminophenylazo)phenyl 1,2-trans glycosides 5a-e with various carbohydrate heads (beta-D-gluco, beta-D-galacto, beta-lacto, beta-D-xylo, and alpha-D-manno) have been synthesized. The key step was the formation of phenyldiazonium tetrafluoroborates 2a-e from the per-O-acetylated 4-aminophenyl glycosides 1a-e. These salts were condensed with N,N-didodecylaniline under phase transfer conditions and the per-O-acetylated 4-(4'-N,N-didodecylaminophenylazo)phenyl 1,2-trans glycosides 4a-e were fully de-O-acetylated by the Zemplén method. The self-organizing liquid crystal properties of the compounds were investigated by a variety of techniques, including polarized light microscopy, differential scanning calorimetry, and X-ray diffraction. All but one of the materials exhibited smectic A, lamellar phases. Remarkably, the glucose derivative exhibited a rectangular disordered columnar phase. This result has implications with respect to the induced curvature created by the recognition processes of the glucose headgroup relative to the other sugar moieties and to the prevalence of various glycolipids in cell membranes     

An efficient one-pot approach to bridged bicyclic ring-systems through consecutive hetero-domino transformations: a mechanistic rationale and further rearrangements

This article describes the design of olefin-generated/reagent-modulated consecutive hetero-domino reactions of 1,2-unsaturated bicyclic diols, which are potentially of great use, initiated by PhI(OAc)(2), continued by [Pb(OAc)(4)], and completed by use of a mild base (K(2)CO(3)). Inversion of a quaternary center has been achieved through a three-reaction sequence: a domino transformation followed by an m-CPBA-mediated Baeyer-Villiger oxidation and subsequent reductive lactone ring opening.     

Sequential acid/base-catalyzed polycyclization of tryptamine derivatives. A rapid access to Büchi's ketone

[reaction: see text] The development of an efficient and diastereoselective methodology that allows the rapid construction of the tetracyclic core of the Aspidosperma and Strychnos alkaloid families is described. Our approach relies upon two key steps: a sequential silica gel/potassium tert-butoxide polycyclization of a tryptamine precursor and a tandem oxidative decarboxylation/ring-closing reaction. The assembly of Büchi's ketone, a key intermediate in the synthesis of vindorosine, has been accomplished using this approach.     

Designing a non-volatile imaging switch for mass-persistent,chemically amplified photolithography: a model study

An acid catalysed rearrangement that transforms a bicyclic lactone into a phenolic carboxylic acid has been tested for potential use in chemically amplified microlithographic imaging.     

Molecular dynamics simulations of the Ag+ or Na+ cation with an excess electron in bulk water

The properties of an excess electron interacting with a monovalent cation in bulk water are studied by molecular dynamics simulations. Sodium and silver cations are chosen as prototypical cases because of their very different redox properties. In both cases, mixed quantum classical molecular dynamics simulations reproduce the experimental UV-Vis spectra. In the case of silver, we observe a highly polarized neutral atom, corresponding to a dipolar excitonic state. For sodium a contact cation/electron pair is observed. Free energy curves along the cation electron coordinate are calculated using quantum Umbrella Sampling technique. The relative stability of the different chemical species is discussed.     

A one-pot process for the enantioselective preparation of saturated secondary alcohols from propargyl ketones under hydrogen transfer conditions

Propargyl ketones can be directly transformed to enantio-enriched saturated secondary alcohols in a one-pot reaction using chiral RuCl[N-(tosyl)-1,2-diphenylethylenediamine)(p-cymene) and Pd/BaSO₄ as catalysts, under transfer hydrogenation conditions.