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Amino Substituents (amino + substituent)
Selected AbstractsPreparation and Reactions of 1,3-Diphosphacyclobutane-2,4-diyls That Feature an Amino Substituent and/or a Carbonyl GroupCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2004Hiroki Sugiyama Abstract The preparation and properties of a 1-amino-1,3-diphosphacyclobutane-2,4-diyl and a 1-benzoyl-1,3-diphosphacyclobutane-2,4-diyl, which can be regarded as functionalized cyclic biradical derivatives, were investigated. Hydrolysis of 1-diisopropylamino-3-methyl-2,4-bis(2,4,6-tri- tert -butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl (7), which is formed by reaction of Mes*CP (4; Mes*=2,4,6- tBu3C6H2) with lithium diisopropylamide and iodomethane, resulted in ring-opening of the 1,3-diphosphacyclobutane-2,4-diyl skeleton, as well as de-aromatization of one of the Mes* rings. 3-Oxo-1,3-diphosphapropene 8 and 7-phosphabicyclo[4.2.0]octa-1(8),2,4-triene 9 were the resultant products, and these were subsequently characterized. Isomerization and oxidation of 7 occurred in the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinoxy) to give the first example of a cyclic dimethylenephosphorane derivative, namely 3-oxo-1,3-diphospha-1,4-diene 10. 1-Benzoyl-3- tert -butyl-2,4-bis(2,4,6-tri -tert -butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl (12) was isolated and characterized from the reaction of 4 with tert -butyllithium and benzoyl chloride. Compound 12 was subsequently heated and underwent rearrangement of the benzoyl group and ring-expansion to afford 1-oxo-1H -[1,3]diphosphole 13. Reaction of 4 with lithium diisopropylamide and benzoyl chloride afforded the 2H -[1,2,4]oxadiphosphinine 15, which was probably formed through the 1,3-diphosphacyclobutane-2,4-diyl intermediate 14. Thermolysis of 15 afforded 1-oxo-1H -[1,3]diphosphole 16 in an Arbuzov-type rearrangement. [source] Amino-substituted O6 -benzyl-5-nitrosopyrimidines: interplay of molecular, molecular-electronic and supramolecular structuresACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2002Antonio Quesada The structures of eight 2,4,6-trisubstituted-5-nitrosopyrimidines (one of which crystallizes in two polymorphs) have been determined, including seven O6 -benzyl derivatives which are potential, or proven, in vitro inhibitors of the human DNA-repair protein O6 -alkylguanine-DNA-transferase. In the derivatives having an amino substituent at the 4-position, an intramolecular N,H,O hydrogen bond with the nitroso O as an acceptor leads to an overall molecular shape similar to that of substituted purines. There is a marked propensity for these nitroso compounds to crystallize with Z, = 2. The structure of an analogue with no nitroso group is also reported for comparative purposes. Compounds containing the N -alkyl substituents ,NHCH2COOEt, ,NHCH2CH2COOEt and ,NHCH(CH2Ph)COOEt, derived from amino acid esters, exhibit a rich variety of conformational behaviour, and in all of the nitroso compounds the bond lengths provide strong evidence for a highly polarized electronic structure. Associated with this polarization is extensive charge-assisted hydrogen bonding between the molecules, leading to supramolecular aggregation in the form of finite (zero-dimensional) aggregates, chains, molecular ladders, sheets and frameworks. [source] Amino and cyano N atoms in competitive situations: which is the best hydrogen-bond acceptor?ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2001A crystallographic database investigation The relative hydrogen-bond acceptor abilities of amino and cyano N atoms have been investigated using data retrieved from the Cambridge Structural Database and via ab initio molecular orbital calculations. Surveys of the CSD for hydrogen bonds between HX (X = N, O) donors, N,T,C,N (push,pull nitriles) and N,(Csp3)n,C,N molecular fragments show that the hydrogen bonds are more abundant on the nitrile than on the amino nitrogen. In the push,pull family, in which T is a transmitter of resonance effects, the hydrogen-bonding ability of the cyano nitrogen is increased by conjugative interactions between the lone pair of the amino substituent and the C,N group: a clear example of resonance-assisted hydrogen bonding. The strength of the hydrogen-bonds on the cyano nitrogen in this family follows the experimental order of hydrogen-bond basicity, as observed in solution through the pKHB scale. The number of hydrogen bonds established on the amino nitrogen is greater for aliphatic aminonitriles N,(Csp3)n,C,N, but remains low. This behaviour reflects the greater sensitivity of the amino nitrogen to steric hindrance and the electron-withdrawing inductive effect compared with the cyano nitrogen. Ab initio molecular orbital calculations (B3LYP/6-31+G** level) of electrostatic potentials on the molecular surface around each nitrogen confirm the experimental observations. [source] Dehydrogenation of Hydridoirida-,-diketones in Methanol: The Selective Formation of Mono- and Dinuclear Acyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2010Roberto Ciganda Abstract The hydridoirida-,-diketone [IrH{(PPh2(o -C6H4CO))2H}Cl] (1) reacts with diimines (NN) or with pyridine (py) in refluxing methanol to undergo dehydrogenation. The reactions afford selectively the cis -acyl, trans -phosphane isomers of the cationic [Ir(PPh2(o -C6H4CO))2(NN)]+ {NN = 2,2,-bipyridine (2); R,N=C(CH3),C(CH3)=N,R, [R = R, = NH2 (3); R = R, = OH (4); R = OH, R, = NH2 (5)]} or neutral [IrCl(PPh2(o -C6H4CO))2(py)] (6) derivatives. The reactions are faster for ligands containing amino substituents. Refluxing 1 in MeOH affords the formation of an equimolar mixture of dimercationic species [Ir2(,-Cl)(,-PPh2(o -C6H4CO))2(PPh2(o -C6H4CO))2]+ (7a and 7b) containing two acyls and a chloride as bridging groups. The isomers could be separated by fractional precipitation. Compound [3]Cl, containing amino substituents in the imino functionalities, catalyses the hydrogen transfer from 2-propanol to cyclohexanone to afford cyclohexanol. All the complexes were fully characterised spectroscopically. Single crystal X-ray diffraction analysis was performed on complexes 6 and [7b]ClO4. [source] Chemical bonding in zwitterionic diamino- meta -quinonoids and their isomersJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2005Tibor Höltzl Abstract Quantum chemical calculations using molecular orbital (HF) and density functional (B3LYP) methods, in conjunction with the 6-311,+,+,G(d,p) basis set, have been applied to investigate the electronic structure of a series of diamino- meta -quinonoid molecules, each containing a six-membered ring coupled with two exocyclic CO bonds situated in a meta position, along with two amino substituents (NH2 and NHR). The chemical bonding phenomena in these zwitterions and isomers where one or two hydrogens are transferred from N to O are analyzed with the aid of the atoms-in-molecules (AIM) approach. The relative energies between zwitterionic and quinonoid isomers in both neutral and ionized states also have been evaluated. Substituents exert a strong effect that in many cases changes the energy ordering. Copyright © 2005 John Wiley & Sons, Ltd. [source] Photophysics of Aminoxanthone Derivatives and Their Application as Binding Probes for DNA,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2006Tamara C. S. Pace ABSTRACT Xanthones with amino substituents were synthesized to diminish the photoreactivity of the xanthone chromophore with DNA, with the objective of using these molecules to study their binding dynamics with DNA. The aminoxanthones showed a strong solvatochromic effect on their singlet and triplet excited-state photophysics, where polar solvents led to a decrease of the energies for the excited states. Quenching of the triplet excited states by nitrite anions was used to determine the binding dynamics, and a residence time in the microsecond time domain was estimated for the bound 2-aminoxanthone with DNA. The quenching experiments performed showed that this methodology will not be applicable to study the binding dynamics of a wide variety of guests with DNA. [source] | ||||||||||