Search

A novel strategy for the synthesis of 4-amino-3-cyano-2,2′- and 5′-amino-4′-cyano-2,3′-bipyrroles via readily available 1-amino-3-imino-3H-pyrrolizine-2-carbonitriles has been developed. The rearrangement leading to 5′-amino-4′-cyano-2,3′-bipyrroles involves formation of the intermediate aziridine, which undergoes other side ring-opening.

Herein, we reported a general, convenient, and efficient synthesis of 3,5-disubstituted-1,2,4-oxadiazoles via cyclodehydration of O -acylamidoximes in the superbase system MOH/DMSO (M = Li, Na, K). Excellent isolated yields (up to 98%) were attained within short reaction times (10–20 min). In addition, mild reaction conditions and a simple work-up procedure allow the synthesis of a wide range of heat-labile 1,2,4-oxadiazole-containing substances.

A method for the synthesis of 5-fluoro- and 5-bromoalkylisoxazoles via nitrosation of alkylated gem -dihalocyclopropanes with a nitrosyl chloride sulfur trioxide adduct has been developed. In the case of bromofluorocyclopropanes the reaction proceeded with excellent chemoselectivity thus providing exclusively 5-fluoroisoxazoles.

The CN-functionalized pyrrole(indole)-3(2H)-furanone derivatives are readily synthesized via the domino reaction of diverse pyrrole(indole) carboxylic acids with tertiary cyanopropargylic alcohols (Et3N, MeCN, MW reactor, 100 °C, 1.2 atm) in up to 93% yield.

ZnII-activated cyanamides NCNR2 (R2 = Me2, Et2, C5H10, (CH2)2O(CH2)2, Ph2) react with the acyclic N-alkyl ketonitrones Ph2CN+(O−)R′ (R′ = Me, CH2Ph) and N-aryl ketonitrones (R′ = Ph, p-BrC6H4, p-EtC6H4) under mild conditions. Uncomplexed 5-aminosubstituted 2,3-dihydro-1,2,4-oxadiazoles (6 examples; 49–82%) were obtained in zinc(II)-involving cycloaddition of the N-alkyl ketonitrones to the cyanamide substrates; these 2,3-dihydro-1,2,4-oxadiazoles undergo ring-opening giving carbamoylamidines and methylidenureas. The N-aryl ketonitrones react with ZnII-activated cyanamides giving the open-chain systems, viz. carbamoylamidines, N′-(2-(diphenylmethylidene)amino)-phenyl-N,N-carbamimidic acids, and methylidenureas, which are presumably formed via the cycloaddition route followed by the N–O cleavage induced by the acceptor character of the aryl groups.

Ketones with bulky aromatic, heteroaromatic and ferrocene substituents react with acetylene in the presence of a KOH/DMSO super-base suspension (90 °C, 15 min) to give polysubstituted furans in up to 86 % isolated yields in a one-pot fashion. This assembly of the furan scaffold involves a domino sequence in which one molecule of ketone reacts with two molecules of acetylene.

PPA-activated nitroalkanes are employed in the design of a one-pot cascade transformation involving metal-free and oxidant-free direct ortho-C–H functionalization, followed by Beckman rearrangement and intramolecular cyclocondensation to produce benzoxazoles and benzobisoxazoles directly from easily available phenols.

A method for the iododifluoromethylation of aromatic aldehydes using (bromodifluoromethyl)trimethylsilane (Me3SiCF2Br) is described. The selective formation of the CF2I group is based on using sodium iodide, with the sodium serving as a scavenger of bromide and iodide serving as a nucleophile with respect to difluorocarbene. The primary CF2I-addition products can undergo HI-elimination or iodine/zinc exchange followed by allylation in a one-pot manner.

A new gem-difluorinated silicon reagent bearing a pyrrolidine dithiocarbamate substituent was prepared by the reaction of (bromodifluoromethyl)trimethylsilane with the corresponding potassium dithiocarbamate. The obtained reagent was employed in the nucleophilic addition to aldehydes and ketones.

The title reaction proceeds under mild conditions to form the corresponding products with high regio- and stereoselectivity.

This article presents an analytical review of the author’s results and the literature concerning the nature of species resulting from NO and CO adsorption on the unreconstructed (1 × 1) and reconstructed hexagonal (hex) Pt(100) surfaces, including specific features of the reactions between these species. At 300 K, both surfaces adsorb NO and CO mainly in their molecular states. When adsorbed on Pt(100)-1 × 1, the NOads and COads molecules are uniformly distributed on the surface. Under the same conditions, the hexagonal surface undergoes adsorption-induced reconstruction with the formation of NOads/1 × 1 and COads/1 × 1 islands, which are areas of the unreconstructed phase saturated with adsorbed molecules and surrounded with the adsorbate-free hex phase. In adsorption on structurally heterogeneous surfaces containing both hex and 1 × 1 areas, the 1 × 1 and hex phases are occupied in succession, the latter undergoing reconstruction into the 1 × 1 phase. The reaction between NO and CO on the unreconstructed surfaces occurs even at room temperature and results in the formation of N2 and CO2 in quantitative yield. On the hexagonal surface, a stable layer of adsorbed molecules as (NOads + COads)/1 × 1 mixed islands forms under these conditions. Above 350 K, the reaction in the mixed islands is initiated by the desorption of small amounts of the initial compounds, and this is followed by rapid self-acceleration leading to a surface explosion yielding N2, CO2, and N2O (minor product). These products show themselves as very narrow desorption peaks in the temperature-programmed reaction spectrum.

5-Acylethynylpyrrole-2-carbaldehydes have been synthesized from the protected pyrrole-2-carbaldehydes by their transition-metal-free topochemical mechanoactivated ethynylation with acylbromoacetylenes in a solid Al2O3 medium (room temperature, 6 h, 41–54% yields).

Significantly shorter reaction times together with higher yields are the benefits when the addition reaction is carried out under solvent-free conditions.

The reaction of phenylenediamines and 2-aminophenols (I) with nitroalkanes (II) in PPA leads to desired benzimidazoles and benzoxazoles (III) in high yields, whilst the reaction with 2-nitro-1-phenylethan-1-one (IV) affords unexpected 2-phenyl substituted products.

A previously reported condensation reaction of ambiphilic 2-(1H-pyrazol-5-yl)phenols with various o-chloro-substituted nitroaromatic synthons to provide medicinally important tetracyclic pyrazolo[1,5-d][1,4]oxazepines was extended to more readily available and convenient-to-use 1,2-dihaloazines. Although 4,5-dichloropyridazin-3(2H)-ones and 2,3-dichloropyrazine are popular bis(electrophilic) partners in various SNAr-type condensations and also were efficiently used in the reaction reported herein, the facility with which various 3-bromo-2-chloropyridines underwent the same cyclization was unexpected. These reactions are presumed to occur as sequential intermolecular SNAr/Smiles rearrangement/intramolecular SNAr tandem reactions and provide a rare example of the transition-metal-free substitution of a bromine atom at the 3-position of a pyridine ring.

The redox properties of metallic nanoparticles are discussed, in particular the relationships between excess charge, size and the Fermi level of the electrons. The redox potentials are derived using simple electrostatic models to provide a straightforward understanding of the basic phenomena. The different techniques used to measure the variation of Fermi level are presented. Finally, redox aspects of processes such as toxicity, electrochromicity and surface plasmon spectroscopy are discussed.

The title compounds are obtained by a novel acid-mediated cascade transformation via the ANRORC (addition of nucleophile, ring opening, and ring closure) mechanism.

A method for the synthesis of gem-difluorinated nitroso compounds is described. The reaction involves interaction of organozinc reagents with (bromodifluoromethyl)trimethylsilane followed by nitrosation of difluorinated organozinc species with an n-butyl nitrite/chlorotrimethylsilane system.

A modular approach to 3-substituted 2-quinolones via a cascade annulation reaction between 4-nitroketones and hydrazines has been developed.

An operationally simple way for the direct installation of aryl groups at the C-7 position of indolines is reported.

Under catalyst- and solvent-free conditions, secondary phosphine selenides easily add to diverse alkenes [acrylonitrile, allyl alcohol, styrene, vinyl ethers, vinyl sulfides, and trimethyl(vinyl)silane] at 80 °C (3–20 h) to give anti-Markovnikov adducts in 70–95% yield.

A new method has been developed for the synthesis of benzimidazole carbothioamides, which have potential pharmacological activity, by a three-component reaction of 1-substituted benzimidazoles, phenylcyanoacetylene, and methyl, allyl, or phenyl isothiocyanates. The reaction of these components proceeds under mild conditions in acetonitrile at 50-55°C for 12-20 h and stereoselectively leads to N-[(Z)-2-cyano-1-phenylethenyl]benzimidazole-2-carbothioamides in 43-82% yield.

The facile protocol allows the catalyst- and solvent-free addition of phosphine sulfides to terminal and internal alkenes.

The process consists of nucleophilic aromatic substitution, Smiles rearrangement, and denitrocyclization.

It's as easy as 1, 2, 3: In a one-pot sequence, two stereocenters and three new bonds were created with high selectivity through an asymmetric alkynylation of acyl silanes, a tandem Brook-type rearrangement and Zn-ene-allene cyclization, the addition of an electrophile, and finally oxidation. The straightforward nature of the synthetic procedure contrasts strongly with the complexity of the densely functionalized products obtained.

Nitration of acylperimidines (I) using NaNO2 in formic acid gives predominantly the 6(7)-nitro-derivatives (II), which can be smoothly transformed into tetraazapyrenes (IV) via a Schmidt Reaction, or triazacyclopentaphenalenes (V) via simple Zn-reduction.

Literature data on structure of coordination sphere of selected monoatomic cations in aqueous and methanol solutions have been reviewed and compared. The following structural parameters have been considered: coordination number, interparticle distances, the second coordination sphere features, and ionic association type. It has been revealed that for doubly charged ions the parameters of the first coordination sphere are similar in the both solvents. The second coordination sphere of the same cation consists of fewer solvating molecules located farther from the ion in the case of methanol as compared to water.

3-Substituted 2-quinolones are obtained via a novel, metal-free transannulation reaction of 2-substituted indoles with 2-nitroalkenes in polyphosphoric acid. The reaction can be used in conjunction with the Fisher indole synthesis offering a practical three-component heteroannulation methodology to produce 2-quinolones from arylhydrazines, 2-nitroalkenes and acetophenone.

Three of the title compounds are synthesized in moderate yields by reaction of naphthotriazine (I) with β-nitrostyrenes.

Previously unknown title compounds are smoothly synthesized by treatment of perimidines (I) with β-nitrostyrene via in situ generated oximes and subsequent Beckmann rearrangement.

Condensation of 2-(1H-pyrazol-5-yl)phenols with 1-chloro-2-nitrobenzenes under basic conditions in N,N-dimethyl­formamide results in a tandem, atom-economical, aromatic nucleophilic substitution–Smiles rearrangement–denitrocyclization process to provide pyrazolo-fused dibenzo[b,f][1,4]oxazepines as a single regioisomer.

Gaseous phosphine reacts with p-methoxystyrene at 70°C to afford bis(methoxyphenylethyl)phosphine (II) in high yield.

The electronic structure and vibrational properties of a Cs2Te4O12 crystal (space group Rm, Z = 1) are characterized by IR and Raman spectroscopy and DFT and lattice-dynamical model calculations.