Ionic photodissociation in arylallyl acetates

We have synthesized several 3-arylallyl acetates 1, 2, 3, 5 and 6, and E-3-(1-naphthyl)-2-propene-1-ol 4 for studying ionic photodissociation. Compounds 1, 2 and 3 underwent an efficient ionic photodissociation in polar solvents like acetonitrile and methanol leading to the formation of rearranged acetate and methyl ether products, as well as undergoing an E-Z isomerization. The arylallyl alcohol 4 and the two arylallyl acetates 5 and 6 did not undergo ionic photodissociation. Quantum yields of product formation, quantum yields of fluorescence, solvent polarity effects and triplet-sensitization studies indicated that a highly polarized excited singlet state is responsible for the ionic photodissociation. Both the singlet- and triplet-excited states are effective in displaying E-Z isomerization in 1, 2, 3 and 4. Compounds 5 and 6 are highly fluorescent, and the fluorescence may be the excited state deactivation pathway along with internal conversion.     

Polyfluorinated enol acetates

The synthesis of polyfluorinated enol acetates has been performed by reductive dechlorination of chloropolyfluoroketones with zinc in Ac₂O. Under these conditions, hexafluoroacetone is preferably reduced at the carbonyl group.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 174–176, January, 1994.     

Ecdysteroid acetates fromAjuga reptans

The compounds 20-hydroxyecdysone-22-acetate and viticosterone E (20-hydroxyecdysone-25-acetate) are observed for the first time inAjuga reptans L. growing at the northern limit of its range in a middle taiga subzone of European northeastern Russia. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–610, September–October, 1999.     

Concerted catalytic reactions for conversion of ketones or enol acetates to chiral acetates

[reaction: see text] Enol acetates or ketones asymmetrically transformed to chiral acetates in high yields with high optical purities through multistep reactions catalyzed by a lipase and a ruthenium complex. 2,6-Dimethylheptan-4-ol was chosen as a suitable hydrogen donor, and 4-chlorophenyl acetate was used as an acyl donor for the conversion of ketones.     

Practical ruthenium/lipase-catalyzed asymmetric transformations of ketones and enol acetates to chiral acetates

Ketones were asymmetrically transformed to chiral acetates by one-pot processes using a lipase and an achiral ruthenium complex under 1 atm of hydrogen gas in ethyl acetate. Molecular hydrogen was also effective for the transformation of enol acetates to chiral acetates without additional acyl donors with the same catalyst system.     

4. Characteristics of cellulose acetates 4.1 Characterization and physical properties of cellulose acetates

An overview is provided of the basic features of cellulose acetate of various degree of substitution in the solid and liquid crystalline state as well as in solution. These features represent a necessity for an understanding of the properties of these cellulose derivatives and further for mixed esters, which are not presented in this paper. Specifically, the crystal structure of cellulose triacetate will be addressed as well as structures in dilute and semi-dilute solutions. Thermal, viscoelastic and further properties in the solid state are discussed as well as flow behavior of solutions and their application in molecular weight determination, including false viscosity of commercial 2.5 cellulose acetates.     

Iron(III) acetates

Summary The compound, Fe₂CI₂(OH)₂(MeCO₂)₂ · 2MeCO₂H · H₂O, combines with lithium and silver acetates to form Fe₂Cl(OH)₂(MeCO₂)₃ · 2MeCO₂H and Fe₂(OH)₂(MeCO₂)₄ · H₂O, respectively. Iron(III)chloride in tetrahydrofuran reacts with silver acetate to give a precipitate consisting of a mixture of Fe(MeCO₂)₃ and AgCl which, when extracted with boiling acetic acid, yields     

Packing in honeycomb networks

Molecules arranging themselves into predictable patterns on silicon chips could lead to microprocessors with much smaller circuit elements. Mathematically, assembling in predictable patterns is equivalent to packing in graphs. An H-packing of a graph G is a set of vertex disjoint subgraphs of G, each of which is isomorphic to a fixed graph H. If H is the complete graph K ₂, the maximum H-packing problem becomes the familiar maximum matching problem. In this paper we give algorithms to find a perfect packing of HC(n) with P ₆ and K _1,3 when n is even and thus determines their packing numbers. Further we also study the packing of HC(n) with 1, 3-dimethyl cyclohexane.     

Optical-activity anisotropy of ordered phases in cellulose acetates

The optical activity of anisotropic solutions of cellulose diacetate in nitromethane and dimethyl sulfoxide and of diand triacetate films with vitrified ordered structure has been studied. The systems under study are characterized by high specific optical rotation [α], suggesting formation of a cholesteric mesophase. The value of [α] is found to depend on the angle of rotation of the samples relative to the direction of the polarization vector of an incident light beam in the plane perpendicular to this beam (the anisotropy of optical activity). This dependence (indicatrix) shows an irregular pattern and, when plotted in Cartesian coordinates, can be described with a distorted sinusoid. The data on the resolution of indicatrices into harmonic constituents and isolation of contributions due to isotropic components and anisotropic components, each of which is determined by the structural element with the corresponding asymmetry, are analyzed.     

Asymmetric synthesis of polymer-supported cyanohydrin acetates

A bimetallic titanium(salen) complex has been used to catalyze the asymmetric addition of potassium cyanide to aldehydes attached to Wang resin giving polymer supported cyanohydrin propionates with up to 91% enantiomeric excesses.     

Binuclear iron(III) acetates

Summary The binuclear iron(III) compound, Fe₂Cl(OH)₂(MeCO₂)₃ 2 AcOH combines with pyridine, -picoline and 2,2-bipyridyl (B) to form Fe₂Cl(OH)₂(AcO)₃·B adducts. The secondary bases, pyrrolidine and diethylamine (RNH), on the other hand, combine with the complete elimination of chlorine to form, Fe₂(NR)(OH)₂(AcO)₃. These products have been characterised by molecular weight, i.r. spectra, magnetic susceptibility and Mössbauer measurements.     

Conductometric titration of metal acetates in aqueous medium

Fifteen metal acetates in aqueous medium have been conductometrically titrated with trichloro-acetic acid. The method has been applied to the titration of mono- and bivalent metals and angles at the equivalence point are sharp enough to allow accurate results to be obtained. Metal salts of acids weaker than acetic can be determined following solution in an excess of acetic acid and titration, because the weaker acid which is displaced does not interfere.     

Novel diphenysulphapyrimidine acetates derived from chalcones

Cyclocondensation of sulphaguanidine acetate with chalcones in dimethylsulphoxide at 110° gave 4,6-diphenylsulphapyrimidine acetates.     

Zinc mediated propenylation of Baylis-Hillman acetates

Allyl bromide efficiently reacts with Baylis-Hillman acetates in the presence of zinc and copper iodide resulting in substituted 1,5-dienes.     

Synthesis of hexopyranosyl acetates and 2,3-disubstituted tetrahydropyrans via chemoselective hydrogenation of hex-2-enopyranosyl acetates

A simple and easy method for chemoselective synthesis of hexopyranosyl acetates and 2,3-disubstituted tetrahydropyrans from hex-2-enopyranosyl acetates was demonstrated. The former was achieved by hydrogenation catalyzed by Rh/Al₂O₃ in EtOAc/toluene solvent at 0 °C, while the latter was carried out using Pd/C in EtOH/AcOH at 25 °C.     

Glycosylation of betulin acetates with glycals

Betulin 2-deoxy-α-d-, 2-deoxy-α-l-, and 2,6-dideoxy-α-l-arabino-hexopyranosides were synthesized by acid-catalyzed glycosylation (cationite in the H⁺ form, LiBr) of betulin 3- and 28-monoacetates with glycal acetates. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 531–534, March, 1998.     

Mass-spectrometric behavior of some C-glycopyranoside acetates

Conclusions The mass-spectrometric behavior of a number of C-glycopyranoside acetates was studiedTranslated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1157–1160, May, 1976.