Search results for "Adduct"
showing 10 items of 320 documents
Cover Feature: Highly Enantioselective Kinetic Resolution of Michael Adducts through N-Heterocyclic Carbene Catalysis: An Efficient Asymmetric Route …
2018
ChemInform Abstract: New Reactions of Amino-Functionalized 3-Vinyl-1H-indoles and Tetrahydropyridin-4-yl Analogues with Dienophiles.
2010
Reactions of 3-[2-(morpholin-4-yl)vinyl]-1H-indole (1), the 1,2-dihydro-9H-carbazole 2, as well as the 3-(tetrahydropyridin-4-yl)-1H-indoles 3a and 3b with some carbo- and heterodienophiles are described. The scope and limitations of the synthetic utility of these amino- (or homoamino)-functionalized 3-vinyl-1H-indoles are reported and some MO calculations for the qualitative prediction of their reactivities are presented. The reactions gave rise to substitution products, redox products, Diels-Alder adducts, ene adducts, and Michael-type adducts (Schemes 2 and 3).
Electrochemistry of copper complexes with polyaza[n]paracyclophanes. Influence of ATP as an exogen ligand on the relative stability of the Cu(II) and…
2000
Abstract Interaction of Cu 2+ with the macrocycle 2,6,9,13-tetraaza[14]paracyclophane (L) and ATP has been followed by pH-metric titration, cyclic voltammetry and differential pulse voltammetry (DPV). Mixed adduct species with various degrees of protonation were found to be stable for pH>4. In neutral and alkaline media reduction of mixed complexes occurs in a two-electron quasi-reversible step in contrast with binary Cu 2+ L complexes which display two successive one-electron couples. The potentiometric and voltammetric data suggest that in ternary adducts ATP binds to Cu 2+ ions through the phosphate chain and one N-site of the adenine ring system.
A 4-tert-butylcalix[4]arene tetrahydroxamate podand based on the 1-oxypiperidine-2-one (1,2-PIPO−) chelate. Self-assembly into a supramolecular ionop…
2014
An octadentate tetrahydroxamic calix[4]arene podand incorporating 1-hydroxypiperidine-2-one (1,2-PIPOH) binding units has been designed as a specific chelator for tetravalent metal cations like Zr4+ or Hf4+. This receptor, which can be considered as the first ever abiotic ligand possessing only cyclic six-membered hydroxamate groups, has been synthesized and characterized in its tetraprotonated form (1H4). Contrary to expectation, however, this new chelator did not form a 1 : 1 complex upon reaction with M(acac)4 (M = Zr and Hf; acac = acetylacetonate), but rather self-assembled into a dimeric species of 2 : 2 stoichiometry. The latter could be characterized in solution by mass spectrometry…
Mechanistic Study of Stepwise Methylisocyanide Coupling and C-H Activation Mediated by a Low-Valent Main Group Molecule
2013
An experimental and DFT investigation of the mechanism of the coupling of methylisocyanide and C-H activation mediated by the germylene (germanediyl) Ge(Ar(Me6))2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2) showed that it proceeded by initial MeNC adduct formation followed by an isomerization involving the migratory insertion of the MeNC carbon into the Ge-C ligand bond. Addition of excess MeNC led to sequential insertions of two further MeNC molecules into the Ge-C bond. The insertion of the third MeNC leads to methylisocyanide methyl group C-H activation to afford an azagermacyclopentadienyl species. The X-ray crystal structures of the 1:1 (Ar(Me6))2GeCNMe adduct, the first and final insertion …
Structurally simple complexes of CO2
2015
The ability to bind CO2 through the formation of low-energy, easily-broken, bonds could prove invaluable in a variety of chemical contexts. For example, weak bonds to CO2 would greatly decrease the cost of the energy-intensive sorbent-regeneration step common to most carbon capture technologies. Furthermore, exploration of this field could lead to the discovery of novel CO2 chemistry. Reduction of complexed carbon dioxide might generate chemical feedstocks for the preparation of value-added products, particularly transportation fuels or fuel precursors. Implementation on a large scale could help to drastically reduce CO2 concentrations in the atmosphere. However, literature examples of weak…
Antimony-121 Mössbauer and infrared spectral studies on 1,10-phenanthroline adducts of antimony(III) halides
1983
Abstract The syntheses of the mono-adducts of 1,10-phenanthroline with SbX 3 (X = F, Cl, Br) and PhSbI 2 are described. These compounds and the 1:1 adduct between 2,2′-bipyridine and PhSbI 2 have been characterized mainly in the solid state by infrared and Mossbauer spectroscopic techniques. The structures of the antimony trihalide complexes appear to be based on halogen bridged polymers in which the stereochemical activity of the lone pair of electrons varies with the halogen, the highest p-character of the lone pair being observed with the trifluoride adduct. Mossbauer results for the PhSbI 2 complexes suggest a ψ-octahedral stereochemistry with the lone pair and the Ph group in trans pos…
The role of distannoxanes in the synthesis of dimethyl carbonate from carbon dioxide
2003
Abstract The synthesis, characterization, and reactivity of 1,3-dimethoxytetrabutyldistannoxane were investigated in connection to the mechanism of the selective synthesis of dimethyl carbonate from CO2 and methanol. A new distannoxane, 1-methoxy-3-methylcarbonatotetrabutyldistannoxane, resulting from a 1:1 adduct with CO2 was isolated and characterised by volumetry, multinuclear NMR and IR spectroscopies. When this compound was submitted to 20 MPa of CO2 at 423 K in toluene no dimethyl carbonate was formed, conversely to dibutyldimethoxystannane. However, when methanol was the solvent, dimethyl carbonate was selectively produced. A promoting effect of Si(OCH3)4 was evidenced through methox…
Diastereoselective Michael addition of (S)-mandelic acid enolate to 2-arylidene-1,3-diketones: enantioselective diversity-oriented synthesis of dense…
2006
[EN] A diversity-oriented approach to enantiomerically pure densely substituted pyrazoles, ¿-aryl-¿-pyrazolylatrolactic acid and ¿-aryl-¿-pyrazolylacetophenones has been developed. The approach utilises the conjugated addition of the lithium enolate of the (2S,5S)-cis-1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde to several 2-arylidene-1,3-diketones, which proceeds readily to give the corresponding Michael adducts in good yields and diastereoselectivities. The cyclocondensation of the 1,3-diketone moieties present in Michael adducts with several hydrazines leads to enantiomerically pure densely substituted pyrazoles. Subsequent basic hydrolysis of the …
Synthesis and Stereochemistry of Diepoxynaphthacenes and Tetraepoxyheptacenes
1997
Cycloaddition reactions of 1,4-dihydro-1,4-epoxynaphthalenes (2) and benzo[c]furans (4), generated in situ from the tetracyclone adducts of 2, yield the diepoxynaphthacenes 5 (Schemes 1, 2). Out of 4 possible stereoisomers an exo-exo and an exo-endo geometry (A and C in Scheme 3) can be realized. The ratio A:C varies from pure A to pure C depending on the substituents of 2 and 4. Stereoisomeric heptacenes 7 can be obtained by a twofold cycloaddition of the same type (Scheme 4). Only one π bond of reactive alkynes such as cyclooctyne or acetylenedicarboxylate is capable of an addition to 4 (Schemes 5, 6).