Search results for "regioselectivity."
showing 8 items of 298 documents
Synthesis of 2,4,6-trisubstituted tetrahydropyrans via 6-exo selenoetherification of unsaturated alcohols
2001
Stereoselectivity, regioselectivity and yields in the 6-exo selenoetherification of four unsaturated diols were found to depend on the stereochemistry of the diols and on the presence of an oxygen atom close to the intermediate seleniranium ring. Silica gel was useful in order to obtain good yields. Reactions performed both under kinetic and thermodynamic control led to the same products. Stereoselectivity, regioselectivity and yields in the 6-exo selenoetherification of four unsaturated diols were found to depend on several factors such as the stereochemistry of the diols, the nature of the R group, the nature of the counter anion of the PhSe+ species and the presence of silica gel.
Nanolayered Cobalt-Molybdenum Sulfides as Highly Chemo- and Regioselective Catalysts for the Hydrogenation of Quinoline Derivatives
2018
[EN] Herein, a general protocol for the preparation of a broad range of valuable N-heterocyclic products by hydrogenation of quinolines and related N-heteroarenes is described. Interestingly, the catalytic hydrogenation of the N-heteroarene ring is chemoselectively performed when other facile reducible functional groups, including alkenes, ketones, cyanides, carboxylic acids, esters, and amides, are present. The key to successful catalysis relies on the use of a nanolayered cobalt-molybdenum sulfide catalyst hydrothermally synthesized from earth-abundant metal precursors. This heterogeneous system displays a tunable composition of phases that allows for catalyst regeneration. Its catalytic …
ChemInform Abstract: Gold(I)-Catalyzed Intermolecular Oxyarylation of Alkynes: Unexpected Regiochemistry in the Alkylation of Arenes.
2010
The reaction between acetylenes and sulfoxides, studied as a test case for gold-catalyzed intermolecular addition, provides the oxyarylation compounds 3 in good yields. Unpredictably, in all cases a single regioisomer arising from the electrophilic aromatic alkylation at the position adjacent to the sulfur atom is obtained instead of the expected Friedel−Crafts regioisomer. A new concerted mechanism based on DFT calculations is proposed to account for the products in this intermolecular gold(I)-catalyzed reaction.
Crystal structure of diethyl 2-amino-5-{4-[bis-(4-methyl-phen-yl)amino]-benzamido}-thio-phene-3,4-di-carboxyl-ate.
2019
The title compound forms a head-to-head centrosymmetric dimer, involving a pair of intermolecular N—H⋯O hydrogen bonds. It also forms two intramolecular bonds between its amine and amide and the ester carbonyl groups.
Angular Regioselectivity in the Reactions of 2-Thioxopyrimidin-4-ones and Hydrazonoyl Chlorides : Synthesis of Novel Stereoisomeric Octahydro[1,2,4]t…
2020
The regioselective synthesis of cis and trans stereoisomers of variously functionalized octahydro[1,2,4]triazolo[4,3-a]quinazolin-5-ones was performed. The 2-thioxopyrimidin-4-ones used in the synthesis reacted with hydrazonoyl chlorides in a regioselective manner to produce the angular regioisomers [1,2,4]triazolo[4,3-a]quinazolin-5-ones rather than the linear isomers [1,2,4]triazolo[4,3-a]quinazolin-5-ones. The synthesis process took place with electronic control. The angular regiochemistry of the products was confirmed by X-ray experiments and two-dimensional NMR studies.
Triazolopyridines 22.1 Description of new 7,9-di(2-pyridyl)[1,2,3]triazolo[5',1':6,1]pyrido[3,2-d]pyrimidines
2002
The new heteroaromatic compounds, 7,9-di(2-pyridyl)(1,2,3)triazolo(5',1':6,1)pyrido(3,2-d) pyrimidines 11a-c, were synthesized in two steps from readily available triazolopyridines 1a-c. Regioselective lithiation of 1a-c followed by treatment with 2-cyanopyridine gave a mixture of compounds 5a-c, and 11a-c in moderate to low yields, together with gums. Similar reactions with the triazolopyridine 1d gave as the only identified compound the triazolopyridine derivative 5d.
Diversity of Isomerization Patterns and Protolytic Forms in Aminocarbene PdII and PtII Complexes Formed upon Addition of N,N′-Diphenylguanidine to Me…
2017
Reaction of the palladium(II) and platinum(II) isocyanide complexes cis-[MCl2(CNR)2] [M = Pd, R = C6H3(2,6-Me2) (Xyl), 2-Cl-6-MeC6H3, cyclohexyl (Cy), t-Bu, C(Me)2CH2(Me)3 (1,1,3,3-tetramethylbuth-1-yl abbreviated as tmbu); M = Pt, R = Xyl, 2-Cl-6-MeC6H3, Cy, t-Bu, and tmbu] with N,N′-diphenylguanidine (DPG) leads to DPG-derived metal-bound deprotonated acyclic diaminocarbene (ADC) species. This reaction occurs via a two-step process, involving the initial coupling of the guanidine with one of the isocyanides and leading to deprotonated monocarbene monochelated species, while the next addition grants the deprotonated bis-carbene bis-chelated metal compounds. DPG behaves as nucleophile, depr…
Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds
2018
In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively th…