Synthesis and structures of ethoxymethylene derivatives of 1,3-diethoxycyclohexenylium perchlorate

1,3-Diethoxy-4,6-di(ethoxymethylene)-5,5-dimethylcyclohexenylium perchlorate (6a) was synthesized from 1,3-diethoxy-5,5-dimethylcyclohexenylium perchlorate by successive introduction of ethoxymethylene groups. Perchlorate6a was also obtained from dimedone in one preparative step. Compound6a was studied by X-ray diffraction analysis. The bond lengths in the fragment containing the C(1)–C(4) and C(6) atoms of the six-membered ring of the cation are substantially equalized and close to the C_arom-C_arom bond length. Apparently, this fact indicates that the positive charge is primarily delocalized over the aromatic system. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2300–2304, November, 1998.     

An Example of a Concircular Vector Field on a Locally Conformally Kähler Manifold

Mathematical Notes - An example of a concircular vector field on a locally conformally Kähler manifold is constructed and the geometric meaning of its characteristic form is studied. It is...     

Synthesis of novel asymmetric dendritic‐linear‐dendritic block copolymers via “living” anionic polymerization of ethylene oxide initiated by dendritic macroinitiators

The first synthesis of asymmetric dendritic‐linear‐dendritic ABC block copolymers, that contain a linear B block and dissimilar A and C dendritic fragments is reported. Third generation poly(benzyl ether) monodendrons having benzyl alcohol moiety at their “focal” point were activated by quantitative titration with organometallic anions and the resulting alkoxides were used as initiators in the “living” ring‐opening polymerization of ethylene oxide. The reaction proceeded in controlled fashion at 40–50 °C affording linear‐dendritic AB block copolymers with predictable molecular weights (M_w = 6000–13,000) and narrow molecular weight distributions (M_w/M_n = 1.02–1.04). The propagation process was monitored by size‐exclusion chromatography with multiple detection. The resulting “living” copolymers were terminated by reaction either with HCl/tetrahydrofuran or with a reactive monodendron that differed from the initiating dendron not only in size, but also in chemical composition. The asymmetric triblock copolymers follow a peculiar structure‐induced self‐assembly pattern in block‐selective solvents as evidenced by size‐exclusion chromatography in combination with multi‐angle light scattering. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5136–5148, 2007     

Low temperature NO disproportionation by Mn porphyrin. Spectroscopic characterization of the unstable nitrosyl nitrito complex MnIII(TPP)(NO)(ONO)

Reaction of NO gas with sublimed layers of the Mn(II)TPP (TPP =meso-tetraphenylporphyrinato2-) at low temperature leads to nitric oxide disproportionation. UV-Vis and FTIR spectroscopy with isotopically substituted nitrogen oxides revealed formation of the unstable species identified as trans-Mn(III)(TPP)(NO)(ONO).     

Polarized Neutron Diffraction as a Tool for Mapping Molecular Magnetic Anisotropy: Local Susceptibility Tensors in CoII Complexes

Polarized neutron diffraction (PND) experiments were carried out at low temperature to characterize with high precision the local magnetic anisotropy in two paramagnetic high‐spin cobalt(II) complexes, namely [Co^II(dmf)₆](BPh₄)₂ ( 1 ) and [Co^II₂(sym‐hmp)₂](BPh₄)₂ ( 2 ), in which dmf=N,N‐dimethylformamide; sym‐hmp=2,6‐bis[(2‐hydroxyethyl)methylaminomethyl]‐4‐methylphenolate, and BPh₄^?=tetraphenylborate. This allowed a unique and direct determination of the local magnetic susceptibility tensor on each individual Co^II site. In compound 1 , this approach reveals the correlation between the single‐ion easy magnetization direction and a trigonal elongation axis of the Co^II coordination octahedron. In exchange‐coupled dimer 2 , the determination of the individual Co^II magnetic susceptibility tensors provides a clear outlook of how the local magnetic properties on both Co^II sites deviate from the single‐ion behavior because of antiferromagnetic exchange coupling.     

Synthesis of derivatives of the new condensed system 4H,7H-furo[3′,4′:6,7]cyclohepta[1,2-<Emphasis Type="Italic">b</Emphasis>]pyran

8-Hydroxy-1,3-dimethyl-4H-cyclohepta[c]furan-4-one reacts with arylidenemalononitriles and, like 1,3-oxo enols, forms the corresponding condensed 2-amino-4H-pyrans. The analogous reaction with 3-(dicyanomethylene)indolin-2-ones give spirocyclic 2-amino-4H-pyrans. The 4-aminopyrimidine ring is formed on the basis of the enamino nitrile fragment of the new pyrans by successive reaction with triethoxymethane and then with aqueous ammonia. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 188–195, February, 2008.     

Binuclear Triphenylantimony(V) Catecholate Based on Redox-Active Bis-<Emphasis Type="Italic">o</Emphasis>-Benzoquinone,a Bis-Catechol-Aldimine Derivative

The oxidative addition of bis-o-benzoquinone Q–(CH=N–N=CH)–Q (L), in which two 3,5-ditert-butyl-o-benzoquinones are linked to each other in positions 6 via the CH=N–N=CH group, to triphenylstibine gave a new binuclear triphenylantimony(V) bis-catecholate complex, Ph₃Sb(Cat–(CH=N–N=CH)–Cat)SbPh₃ (I). Recrystallization of I from a methanol–trichloromethane mixture resulted in an additional coordination of a methanol molecule to each antimony atom to give the binuclear complex, (CH₃OH)Ph₃Sb(Cat–(CH=N–N=CH)–Cat)SbPh₃(CH₃OH) (I · 2CH₃OH), the crystals of which (I · 2CH₃OH) · 2CH₃OH · CHCl₃ (II) contain additionally two methanol solvate molecules, which fix the geometry of the nitrogen-containing bridging group, and a trichloromethane molecule. The molecular structure of compound II in the crystalline state was determined by X-ray diffraction (CIF file CCDC no. 1560840).     

Photoreduction of 9,10-Phenanthrenequinone in the Presence of Dimethacrylate Oligomers and Their Polymers

The effective rate constants for the photoreduction (k_H) of 9,10-phenanthrenequinone (PQ) in the presence of dimethacrylate monomers (ethylene glycol dimethacrylate (DMEG), triethylene glycol dimethacrylate (TGM-3), and oligocarbonate dimethacrylate (OKM-2)) and porous polymers based on them have been spectrophotometrically determined. The values of k_H in the presence of DMEG and TGM-3 in benzene solutions and in the monomer media are two times greater than in the presence of OKM-2. The values of k_H for PQ in pores of polyDMEG, polyTGM-3, and polyOKM-2 are approximately identical and do not depend on the pore size (up to hundreds of nanometers) and the specific surface area.