1,720,973 research outputs found
Stereoselective Alkylation of Chiral 2-Imidoylphenols with Organolithium Reagents: Synthesis of Enantiopure 2-Aminoalkylphenols
No full textIn this paper the addition of organolithium reagents to chiral imidoylphenols to prepare enantiopure phenolic Mannich-type bases is described. The experimental data show that this kind of imine is surprisingly reactive toward organolithium reagents, differently from classical imines, and does not need any Lewis acid or base activation. Moreover, interesting results have been obtained with aldimines but more unusually with ketimines. This reaction results in high yields and diastereoselectivities and allows the preparation of aminophenols quaternary at the C-1 carbon atom, which cannot be prepared with the methods available till now. The sense of asymmetric induction has been explained and confirmed in agreement with the results previously obtained by hydride reduction of the same substrates. In some cases this procedure is complementary to the reductive one, allowing the preparation of the diastereomers less abundant in the reduction. The reaction allows the synthesis of one or the other of the two diastereomers, choosing the opportune starting imidoylphenol and the organolithium reagent
A facile synthesis of 3,4-dialkyl-3,4-dihydro-2H-1,3-benzoxazin-2-ones and naphthoxazin-2-ones and their reactions with organolithium and grignard reagents - preparation of N-[1-(2'-hydroxyphenyl)alkyl]amides
No full textA facile and simple method for the preparation of 3,4-dialkyl-3,4-dihydro-2H-1,3-benzoxazin-2-ones or naphthoxazin-2-ones in high yields from aminoalkylphenols and aminoalkylnaphthols is described. The reactions of the products obtained with organolithium and Grignard reagents were studied, and a method for the preparation of N-[1-(2-hydroxyphenyl)alkyl]-N-alkylamides, which are of pharmaceutica interest, from benzoxazinones was developed. A opssible reaction mechanism is also proposed. The relative configuration of chiral products was determined from conformational analysis of 1H-NMR spectra
Ready N-Alkylation Of Enantiopure Aminophenols: Synthesis Of Tertiary Aminophenols
No full textA regioselective indirect alkylation of aminophenols to enantiopure tertiary aminophenols, which are useful chiral ligands for metal-catalysed asymmetric reactions, is reported. This very simple synthetic methodology, through reduction or alkylation of an intermediate benzoxazine, was performed in mild conditions, suitable for the conservation of the configuration of the stereogenic centres. Some crystalline aminophenols show the phenomenon of ‘crystallization-induced asymmetric transformation’
Reduction of 4H-Chromen-4-ylidene Amines: Synthesis of 2-[(1-Aminoalkyl)-3-Aryl-2-propenyl] Phenols
No full textSynthesis of enantiopure 2-aminoalkylphenols by stereoselective addition of Grignard reagents to chiral 2-imidoylphenols
No full textThe reaction of beta-enaminoesters with organolithium reagents: a convenient method for the regioselective synthesis of enaminoketones
No full textA simple and practical method for the regioselective preparation of beta-enaminoketones is described. The method relies on the reaction of beta-enaminoesters with organolithium reagents, and allows the preparation of a range of unusual beta-enaminoketones
A practical stereoselective synthesis of secondary and tertiary aminonaphthols: chiral ligands for enantioselective catalysts in the addition of diethylzinc to benzaldehyde
No full textA practical procedure for the stereoselective synthesis of a wide group of functionalized aminoalkylnaphthols, using inexpensive starting materials, is reported. Selective N-alkylation was carried out by cyclization of secondary aminoalkylnaphthols with formaldehyde, followed by reduction or alkylation with organometallic reagents. The catalytic activity of this class of compounds was tested in the addition of diethylzinc to benzaldehyde, resulting in moderate to good enantioselectivities. It is noteworthy that the aminonaphthols obtained as the major diastereomer in the solvent free synthesis, have the best asymmetric induction properties in the alkylation reaction
Pulmonary changes in a man affected by von Recklinghausen's disease.
No full textLung involvement in von Recklinghausen's disease is very rare and only sporadic cases have been reported in the literature. We present the case of a man affected by neurofibromatosis type 1 (NF1). The man complained of shortness of breath of 3-4 years duration. Chest radiograph and computed tomographic (CT) scan showed the presence of severe bullous emphysema, with extensive widespread bulky subpleural bullae, involving mainly the upper lobes and apical segments of the lower lobes, bilaterally. Functional respiratory tests documented a picture of severe obstruction associated with marked alveolar hyperinflation (vital capacity (VC) 80% of predicted, forced expiratory volume in one second (FEV1) 49% pred, maximal mid-expiratory flow (MMEF) 22% pred, residual volume (RV) 151% pred). Capillary alveolar diffusion was also markedly altered (transfer factor of the lungs for carbon monoxide (TL,co) 41% pred). The eventual prospect of a lung transplant, never previously considered for this disease, has been advised by the thoracic surgeons. In the light of this possibility, multidisciplinary assessment and monitoring of respiratory function over time are indispensable, in order to identify the transplant window correctly
Solvent-free asymmetric aminoalkylation of electron-rich aromatic compounds: stereoselective synthesis of aminoalkylnaphthols by crystallization-induced asymmetric transformation
No full textElectron-rich aromatic compounds such as 2-naphthol give a faster and asymmetric 1-aminoalky-lation with high yields when treated with (R)-1-phenylethylamine and aromatic aldehydes in solvent-free conditions. An asymmetric transformation of a second kind, probably induced by the preferential crystallization of one diastereomer, affords the straightforward and stereoselective synthesis of aminoalkylnaphthols. Mechanisms predictable for this asymmetric reaction are reported. The absolute configurations and the conformations of the unknown aminonaphthols are widely ascertained
The International Congresses Hypogea / UIS 2015-2021
No full textUIS International Union of Speleology is the world reference organization for the scientific speleological activities, formed in 1965, counting members from all continents, represented by a delegate from each country (this delegate acts as the representative of all the country's cavers and speleologists). An elected Bureau runs the affairs of the UIS between the once-every-four-years General Assembly meetings held at the International Congresses. The actual speleological work of the UIS is done by the members of its Commissions and Working Groups, which are open to everyone who is interested.
The Commission on Artificial Cavities is a part of the Department of Scientific research at UIS. The updated members of the Commission belong from the following countries: Australia, Belgium, France, Great Britain, Ireland, Israel, Italy, Netherlands, Portugal, Russia, Turkey and United States of America
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