Search results for "Heteroatom"
showing 10 items of 63 documents
Valence Topological Charge-Transfer Indices for Reflecting Polarity: Correction for Heteromolecules
2005
Valence topological charge-transfer (CT) indices are applied to the calculation of dipole moments mu. The mu calculated by algebraic and vector semisums of the CT indices are defined. The model is generalized for molecules with heteroatoms and corrected for sp(3)-heteromolecules. The ability of the indices for the description of the molecular charge distribution is established by comparing them with mu of the valence-isoelectronic series of cyclopentadiene, benzene and styrene. Two CT indices, mu(vec) (vector semisum of vertex-pair mu) and mu(vec)V (valence mu(vec)) are proposed. The mu(vec) behaviour is intermediate between mu(vec) and mu(experiment). The correction is produced in the corr…
Improvement of charge-transfer indices for multifunctional amino acids: Application to lysozyme
2008
Valence topological Charge-Transfer (CT) indices are applied to the calculation of pH at the isoelectric point (pI). The model is generalized for molecules with heteroatoms. The ability of the indices for the description of molecular charge distribution is established by comparing them with the pI of 21 amino acids. Linear correlation models are obtained. The CT indices improve multivariable regression equations for pI. The variance decreases by 95%. No superimposition of the corresponding G(k)-J(k) and G(k)(V)-J(k)(V) pairs is observed in most fits, which diminishes the risk of collinearity. The inclusion of heteroatoms in pi-electron system is beneficial for the description of pI, the bec…
Cu(I) complexes with diethoxyphosphoryl-1,10-phenanthrolines in catalysis of C–C and C–heteroatom bonds formation
2015
Abstract Diethoxyphosphoryl substituted 1,10-phenanthroline copper(I) complexes were tested as catalysts in the Sonogashira-type reaction, α-arylation of phosphoryl-stabilized C–H acids, C–N, C–P bond forming reactions (substitution reactions) and in the reaction of phenylacetylene and bis(pinacolato)diboron (addition reaction). The complexes demonstrate fairly high catalytic activity and in some cases their efficiency is superior to that of the parent Cu(phen)(PPh 3 )Br (phen = phenanthroline).
Syntheses and structure of bis(pentamethylcyclopentadienyl)dithiophosphinato complexes
1997
Bis(pentamethylcyclopentadienyl)phosphane Cp*2PH reacts with sulfur under basic conditions to give the corresponding dithiophosphinate salts M+ CP*2PS−2 (5 M+ = HNEt+3, 6 M+ = Li+), which are formed via the intermediate CP*2P(S)H (4). Both salts on treatment with cobalt(II) chloride give rise to the transition metal dithiophosphinate 7. The structures of this new type of diorganodithiophosphinate complexes in the solid state have been investigated. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 521–525, 1997
ChemInform Abstract: Benzothietes. Versatile Synthons for the Preparation of Heterocycles
2010
Abstract Thermal or photochemical ring opening transforms benzo[b]thiete to o-thiobenzoquinonemethide, a highly reactive 8π electron system. Cycloaddition reactions or linear additions with subsequent cyclizations lead to larger heterocyclic rings. A variety of compounds containing sulfur and possibly further heteroatoms like nitrogen, oxygen or phosphorus in normal, medium and large ring systems can be synthesized on this route.
BENZOTHIETES—VERSATILE SYNTHONS FOR THE PREPARATION OF HETEROCYCLES
1994
Abstract Thermal or photochemical ring opening transforms benzo[b]thiete to o-thiobenzoquinonemethide, a highly reactive 8π electron system. Cycloaddition reactions or linear additions with subsequent cyclizations lead to larger heterocyclic rings. A variety of compounds containing sulfur and possibly further heteroatoms like nitrogen, oxygen or phosphorus in normal, medium and large ring systems can be synthesized on this route.
Unveiling the nature of supramolecular crown ether–C60 interactions
2015
A series of exTTF-(crown ether)2 receptors, designed to host C60, has been prepared. The size of the crown ether and the nature of the heteroatoms have been systematically changed to fine tune the association constants, which were determined by a number of complementary spectroscopic techniques. Electrochemical measurements and transient absorption spectroscopy assisted in corroborating charge transfer in the ground state and in the excited state, leading to the formation of radical ion pairs featuring lifetimes in the range from 12 to 21 ps. To rationalize the nature of the exTTF-(crown ether)2$C60 stabilizing interactions, theoretical calculations have been carried out, suggesting a syner…
Asymmetric addition of a nitrogen nucleophile to an enoate in the presence of a chiral phase-transfer catalyst: A novel approach toward enantiomerica…
2012
A proof of concept for the asymmetric organocatalytic aza-Michael addition reaction of nitrogen nucleophiles with simple and readily available alkyl enoates as acceptor molecules in the presence of a chiral phase-transfer catalyst has been demonstrated. The desired enantiomerically enriched beta-amino acid derivatives were obtained in up to 86% yield and with enantioselectivities of up to 37% ee. (C) 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:202209, 2012; View this article online at . DOI 10.1002/hc.21004
Recurrence of the oxazole motif in tubulin colchicine site inhibitors with anti-tumor activity
2021
Abstract Because of its wide spectrum of targets and biological activities, the oxazole ring is a valuable heterocyclic scaffold in the design of new therapeutic agents with anticancer, antiviral, antibacterial, anti-inflammatory, neuroprotective, antidiabetic and antidepressant properties. The presence of two heteroatoms, oxygen and nitrogen, offers possible interactions (hydrogen, hydrophobic, van der Waals or dipoles bonds) with a broad range of receptors and enzymes. Furthermore, the oxazole core conjugates low cytotoxicity with improved compound solubility and is well suited to structural modifications such as substitution with different groups and condensation to aromatic, heteroaroma…
Theoretical search for low-band-gap vinylene linked polymers: heteroarylene vinylene copolymers
1993
Abstract We report a study of the role of the heteroatoms on the electronic properties of poly(thienylene vinylene-co-furylene vinylene), poly(thienylene vinylene-co-pyrrylene vinylene) and poly(furylene vinylene-co-pyrrylene vinylene) at the VEH level. The theoretical calculations show that the electronic properties depend on the nature of the heteroatoms present in the copolymer. The VEH trends are in accord with experimental and theoretical data reported in the literature.