Search results for "stereo"

o-(Hydroxyalkyl)phenyl P-Chirogenic Phosphines as Functional Chiral Lewis Bases

2013

The stereoselective synthesis of P-chirogenic phosphines bearing an o-hydroxyalkyl chelating arm is described. The synthesis is based either on the hydroxyalkylation of P-chirogenic o-bromophenylphosphines (borane) or on their carbonatation and then reduction. The hydroxyalkylation with benzaldehyde or pivalaldehyde affords a mixture of epimers which are isolated by chromatography and characterized by their X-ray structures. Preliminary assays of free P-chirogenic o-(hydroxyalkyl)phenyl phosphines, as new functional Lewis bases in catalyzed asymmetric aza-MBH reaction, lead to β-aminoester derivatives with ee values up to 74%.

Synthese und narkotische Wirkung von Pyrimido[1,2-a]benzimidazol-2,4-dionen Synthesis and Anesthetic Activity of Pyrimido[1,2-a]benzimidazole-2,4-dio…

1982

Eine betrachtliche Zahl zentral dampfender Verbindungen weist als gemeinsames Strukturelement die Carbonamidgruppierung in offenkettiger oder cyclischer Form auf. Unsere jungsten Untersuchungen uber antibakteriell1 und herbizid2 wirksame Pyrimido[1,2-a]benzimidazole legten nun nahe, in die Entwicklung dieser Strukturklasse die Carbonamidgruppierung einzubeziehen.

1,3-Dipolar cycloadditions of electrophilically activated benzonitrile N-oxides. Polar cycloaddition versus oxime formation.

2006

The reactions of electrophilically activated benzonitrile N-oxides (BNOs) toward 3-methylenephthalimidines (MPIs) have been studied using density functional theory (DFT) at the B3LYP/6-31G* level. For these reactions, two different channels allowing the formation of the [3 + 2] cycloadducts and two isomeric (E)- and (Z)-oximes have been characterized. The 1,3-dipolar cycloadditions take place along concerted but highly asynchronous transition states, while formation of the oximes is achieved through a stepwise mechanism involving zwitterionic intermediates. Both reactions are initiated by the nucleophilic attack of the methylene carbon of the MPIs to the carbon atom of the electrophilically…

Unique Bridging Function of the Triazole Core in Copper(II) Chloride Complexes with 1-Allylbenzotriazole

2005

During alternating-current electrochemical synthesis of copper(I) π-complex of [CuCl{C6H4N3(C3H5)}] composition, starting from ethanol solution, containing CuCl2·2H2O and 1-allylbenzotriazole, green crystals of intermediate [CuII3Cl6{C6H4N3(C3H5)}4] (I) compound has been obtained upon 24 h. After some days these crystals transform into red ones of [CuII2Cl4{C6H4N3(C3H5)}3] (II). Both compounds were X-Ray structurally investigated. Crystals of I are triclinic, sp.gr. a = 9.1329(9), b = 10.0352(4), c = 12.239(3) A, α = 76.443(13), β = 84.470(14), γ = 76.808(7)°, V = 1060.5(3) A3, R = 0.0414 for 3311 reflections. II: monoclinic, C2/c, a = 13.828(1), b = 15.044(2), c = 10.702(1) A, β = 91.36(1)…

1-Benz­yloxy-1H-benzotriazole

2012

In the title compound, C13H11N3O, the dihedral angle between the benzotriazole ring system [maximum deviation = 0.027 (16) Å] and the benzene ring is 10.28 (9)°. The C—C—O—N bond adopts an anti conformation [torsion angle = −177.11 (16)°]. In the crystal, the molecules interact via weak C—H...π interactions and aromatic π–π stacking [centroid-to-centroid distance = 3.731 (12) Å].

ChemInform Abstract: 2-Aryl-Substituted 4H-3,1-Benzoxazin-4-ones as Novel Active Substances for the Cardiovascular System.

2010

4H-3,1-Benzoxazin-4-ones of the structural types 3 and 4 are accessible by cyclization reactions. The introduction of the phosphonate group was achieved by way of Wohl-Ziegler bromination and subsequent Michaelis-Arbuzow reaction with a trialkyl phosphite. Pharmacological investigations on isolated left atria, ileum specimens, and Langendorff hearts as well as in vivo circulatory studies on anesthetized rats revealed that the phosphonates 4 exert calcium antagonistic effects. Whereas 2-(arylvinyl)benzoxazinones gave rise to pronounced negative inotropic effects, compound 3e exhibited relaxing effects on smooth musculature in particular and markedly increased the coronary flow through Langen…

Synthesis and Biological Properties of Benzothiazole, Benzoxazole, and Chromen-4-one Analogues of the Potent Antitumor Agent 2-(3,4-Dimethoxyphenyl)-…

2008

New fluorinated 2-aryl-benzothiazoles, -benzoxazoles, and -chromen-4-ones have been synthesized and their activity against MCF-7 and MDA 468 breast cancer cell lines compared with the potent antitumor benzothiazole 5. Analogues such as 9a, b and 12a, d yielded submicromolar GI50 values in both cell lines; however, none of the new compounds approached 5 in terms of antitumor potency. For 5, binding to the aryl hydrocarbon receptor appeared to be necessary but not sufficient for growth inhibition.

Chromatographic separation of chlorthalidone enantiomers using β-cyclodextrins as chiral additives

2000

Different beta-cyclodextrins have been tested as chiral additives in the mobile phase for the chromatographic analysis of chlorthalidone enantiomers in a C18 LiChrospher (125 x 4 mm I.D.) column. The effect on enantioresolution of different parameters was studied: composition of the mobile phase (percentage of organic solvent, type of buffer and pH), mobile phase flow-rate, and type and concentration of beta-cyclodextrin. A 25:75 mixture of methanol and 0.1 M phosphate buffer, pH 4, containing 2% triethylamine (v/v), and 12.5 mM beta-cyclodextrin, at a flow-rate of 0.8 ml/min, was found to be the best option for the resolution of chlorthalidone enantiomers. Under such conditions, linear cal…

1H and13C NMR assignments and conformational analysis of some tetracyclic compounds with a bicyclo[4.2.0]octane ring system

1998

Rhodium(III)-catalyzed ring-opening of strained olefins through C–H activation of O-acetyl ketoximes: an efficient synthesis of trans-functionalized …

2013

An efficient strategy for the stereoselective synthesis of functionalized cyclopentenes and spiro[2.4]heptenes from strained olefins via C–H activation of aryl ketone O-acetyl ketoximes using [RhCl2Cp∗]2 catalyst is described. The results revealed that a wide range of readily accessible aryl and heteroaryl ketoximes are compatible in this method for the ring opening of bicyclic and spirotricyclic olefins.