Search results for "CONDENSATION"
showing 10 items of 468 documents
ChemInform Abstract: Attempted Preparation of Trisphenol-II.
2010
Abstract Condensation of 4,4-bis-(4-methoxyphenyl)-2-methyl-2-pentanol with phenol, in the presence of hydrogen chloride, gives 1,3,3-trimethyl-1-(4-methoxyphenyl)-5-methoxyindan and tris-(4-methoxyphenyl)-ethane instead of expected 2,2,4-tris-(4-methoxyphenyl)-4-methylpentane (trisphenol-II). tris-(4-Hydroxyphenyl)-ethane was obtained, together with bisphenol-A, by condensation of phenol with acetylacetone.
Dimethoxy Aromatic Compounds. VIII. Degenerate Dealkylation-Realkylation Reaction of 1-Bis(2,4-dimethoxyphenyl)-2-methylpropane.
1994
The condensation reaction under acid condition of the benzylic alcohols 1, 2 and 3 with the hexadeutero dimethoxybenzenes 4, 5 and 6 leads to the expected hexadeutero bis(dimethoxyphenyl)-2-methylpropanes 7, 8 and 9, respectively. However, the presence of both dodecadeutero and unlabelled 1-bis(2, 4-dimethoxyphenyl)-2-methylpropanes 10 and 11 indicates that 9 undergoes a rapid degenerate dealkylation-alkylation reaction.
Metal-organic frameworks-based catalysts for biomass valorization
2020
Abstract The objective of this chapter is to review the most promising metal-organic framework (MOF) catalysts in biomass valorization processes in the bulk and fine chemical industries. Either bulk metal-organic frameworks, encapsulated catalytic species in MOFs, or MOF-derived catalysts are revised in terms of activity, selectivity, and stability for biomass valorization applications. The work revised here is focused on the transformation of lignocellulose biomass through purely chemical pathways. In the first part of the chapter, the few studies of cellulose hydrolysis into monosaccharides reported are commented, since this crucial first step in the valorization of hemicellulose is expec…
ChemInform Abstract: Access to Pyrazolidin-3,5-diones Through Anodic N-N Bond Formation.
2016
Pyrazolidin-3,5-diones are important motifs in heterocyclic chemistry and are of high interest for pharmaceutical applications. In classic organic synthesis, the hydrazinic moiety is installed through condensation using the corresponding hydrazine building blocks. However, most N,N'-diaryl hydrazines are toxic and require upstream preparation owing to their low commercial availability. We present an alternative and sustainable synthetic approach to pyrazolidin-3,5-diones that employs readily accessible dianilides as precursors, which are anodically converted to furnish the N-N bond. The electroconversion is conducted in a simple undivided cell under constant-current conditions.
Polycondensed nitrogen heterocycles. X. 5,6,7,8-Tetrahydropyrrolo[1,2-e][1,5]benzodiazocin-7-ones. A new ring system
1981
The synthesis of a new heterocyclic ring system is described. Condensation of 1,4-diketones 1a,b with β-alanine gave the substituted propionic acids 2a,b which upon reduction with palladium on charcoal afforded compounds 3a,b. Title compounds 4a,b were obtained by refluxing 3a,b in toluene with p-toluenesulphonic acid as catalyst.
A Facile Synthesis of New 3-Substituted-2,3- dihydropyrido[3,2-d]pyrimidine-2,4-diones
2004
Abstract Pyrido[3,2-d]pyrimidine-2,4-diones derivatives have been synthesized in good yields by two efficient synthetic routes, the first one through an hetero-cyclization on the ureas derivatives 3a–e under alkaline conditions, the second one by condensation of the isocyanate 2 with various arylalkylamines in pyridine.
Apical seal comparison of low-temperature thermoplasticized gutta-percha technique and lateral condensation with two different master cones
2007
Aim: To compare the apical sealing in mesio-buccal canals of extracted molars obturated with low-temperature thermoplasticized gutta-percha or cold lateral condensation techniques using a .06 or a .02 mm/mm tapered gutta-percha master cone. The secondary aim was to evaluate the depth of spreader penetration in root canals using a .06 or a .02 mm/mm tapered gutta-percha master cone. Methodology: Forty-four mesio-buccal curved canals (25-40º) were instrumented with .06 nickel-titanium rotary instruments and randomly distributed into two control groups (n=4) and three experimental groups (n=12) for obturation by the Ultrafil® 3D system or by cold lateral condensation with .06 or .02 tapered ma…
On the synthesis of functionalized porphyrins and porphyrin conjugates via β-aminoporphyrins
2016
International audience; The synthesis of functionalized porphyrins and their conjugates from meso-tetraarylporphyrins through the acylation and the oxidation of beta-aminoporphyrins was investigated. 2,3-Dioxochlorins were prepared by the oxidation of a variety of beta-aminoporphyrins and subsequently used in a condensation reaction with functionalized aromatic aldehydes and ammonium acetate to form beta-functionalized porphyrins bearing a fused imidazole ring. Under optimized experimental conditions both reactions tolerate various functional groups and afford the products in an appropriate overall yield. The mildness and usefulness of this methodology are illustrated by several examples in…
Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign
2005
Environmental Context. Secondary processes leading to the production of ultra-fine particles by nucle- ation are still poorly understood. A fraction of new particles formed can grow into radiatively active sizes, where they can directly scatter incoming solar radiation and, if partly water soluble, contribute to the cloud condensation nuclei population. New particle formation events have been frequently observed at the Mace Head Atmospheric Research Station (western Ireland), under low tide and sunny conditions, leading to the hypothesis that new particles are formed from iodo-species emitted from macroalgae. Abstract. New particle formation processes were studied during the BIOFLUX campaig…
New particle formation inside ice clouds: In-situ observations in the tropical tropopause layer of the 2017 Asian Monsoon Anticyclone
2021
Abstract. From 27 July to 10 August 2017 the airborne StratoClim mission took place in Kathmandu, Nepal where eight mission flights were conducted with the M-55 Geophysica up to altitudes of 20 km. New Particle Formation (NPF) was identified by the abundant presence of ultrafine aerosols, with particle diameters dp smaller than 15 nm, which were in-situ detected by means of condensation nuclei counting techniques. NPF fields in clear-skies as well as in the presence of cloud ice particles (dp > 3 µm) were encountered at upper troposphere/lowermost stratosphere (UT/LS) levels and within the Asian Monsoon Anticyclone (AMA). NPF-generated ultrafine particles in elevated concentrations (Nuf)…