Reaction of 2-Tetrafluoropropoxy-5,6-benzo-1,3,2-dioxaphosphorinan-4-one with Pyruvonitrile

The reaction of pyruvonitrile with 2-tetrafluoropropoxy-5,6-benzo-1,3,2-dioxaphosphorinan-4-one results mainly in the enlargement of the starting heteroring to form 4-cyano-4-methyl-2-tetrafluoropropoxy-6,7-benzo-1,3,2⁵-dioxaphosphepin-5-one 2-oxide as a mixture of two diastereomers (14:1) along with minor amounts of 3-cyano-3-methyl-2-tetrafluoropropoxy-6,7-benzo-1,4,2⁵-dioxaphosphepin-5-one 2-oxide.     

Synthesis and Spatial Structure of the Derivatives of 2,5-Dioxo-3,3-Bis(Trifluoromethyl)-6,7-Benzo-1,4,2-and 2,5-Dioxo-4,4-Bis(Trifluoromethyl)-6,7-Benzo-1,3,2-Oxazaphosphepines

Abstract

Hexafluoroacetone imine easily interacts with compounds (I, R = OMe, OCH₂CF₂CHF₂, NEt₂, Ph) in two directions unlike hexafluoroacttone and gives 1,4,2-oxazaphosphepines (II) (pathway I) or 1,3,2-oxszaphosphepines (III) (pathway 2). The compound (II) (R = NEt₂) lightly hydrolyzes to yield the salt (IV). The structure of heterocycles II-IV) has been confirmed by X-ray analysis (see fig. I, II, R = OMe; fig. 2, IV). The detail structural peculiarities of the compounds am discussed.     

Tetracoordinate phosphorus cage compounds with endocyclic P–C bonds: Synthesis and reactivity

The survey summarizes modern methods of synthesis and reactivity of tetracoordinated phosphorus cage compounds containing one or more endocyclic P–C bonds (phosphine oxides, phosphinates and phosphonates, phosphatripticenes and others). Intramolecular cyclization reactions including electrophilic aromatic substitution with unsaturated organophosphorus compounds, reactions of P–H-derivatives with carbonyl compounds as well as cycloaddition reactions involving I–IV-coordinated phosphorus derivatives are considered.     

Low-temperature Crystallizational Preconcentration of Impurities in Environmental Analysis

Phenols of natural and antropogenic derivations are respected to the dangerous and wide occurring organical impurities coining in the environment with waste waters of chemical plants. Maximum permissible concentration (MPC) of phenol for unchlorinated water is 0.1 mg/l, and for chlorinated one - 0.001-0.002 mg/l. For the determination of such small contents of phenol in waters preliminary extractional or sorptional concentration is used.     

FLUORESCENCE AND THE LOCATION OF TRYPTOPHAN RESIDUES IN PROTEIN MOLECULES

Abstract— Fluorescence spectra of a number of native and denaturated proteins have been analysed, using spectral band width (ΔΛ), spectral maximum position (Λ_m), fluorescence quenching by external ionic quenchers, lifetime (b), and quantum yield ( q ) and its changes upon denaturation. The results enabled a model of fluorescence properties of tryptophan residues in the proteins to be substantiated by considering the existence of three discrete spectral classes, one buried in nonpolar regions of the protein (Λ_m 330–332 nm, ΔΛ= 48–49nm, q 0.11, τ= 2.1 ns) and two on the surface. One of the latter is completely exposed to water (Λ_m# 350–353 nm, ΔΛ= 59–61 nm, q # 0.2, τ= 5.4 ns); the other is in limited contact with water which is probably immobilized by bonding at the macromolecular surface (Λ_m# 340–342 nm, ΔΛ= 53–55 nm, q # 0.3, = 4.4 ns). Some quantitative predictions from the model, for (a) the fraction of fluorescence that is quenched by ionic quenchers, (b) the mean values of quantum yield, and (c) the mean values of fluorescence lifetime for various proteins, show good concordance with independent experimentally determined values.     

1,3,2(1,4,2)-Dioxaphosphepins annelated with naphthalene fragment: Synthesis and steric structure

Reaction of hexafluoroacetone and chloral with 2-R-naphtho-1,3,2-dioxaphosphorin-4-ones yields 2-R-2,5-dioxo-4,4-bis(trifluoromethyl)naphthol-1,3,2-and 2-R-2,5-dioxo-3-trichloromethylnaphtho-1,4,2λ⁵-dioxaphosphepins. Hydrolysis of the fluorophosphepins gives naphthyl-substituted fluorinated hydroxy ketones. The steric structure of the dioxaphosphepins and some fluorinated ketones was confirmed by single crystal X-ray diffraction. A competition between the π-π and halogen-halogen interactions and hydrogen bonds of classic type in the formation of crystal packing and supramolecular structure was revealed.     

Synthesis and Spatial Structure of 2,5-Dioxo-4-Dialkoxy-Phosphoryl-4-Aryl-6,7-Benzo-1,3,2-Dioxaphosphepines

Abstract

Phosphorus (111) containing dcrivatives of salicylic acid easily react with carbonyl compounds with formation of cycloexpansion products - 1,3,2- or 1,4,2-dioxaphosphepines. For the first time we have shown that dialkyl-l-oxólkylphosphonates react with 2-R-4-oxo-5,5-benzo-1,3,2-dioxaphosphorinanes and yield 1,3,2-dioxaphosphepines (I) with high stereoselectivity. The configuration of the preferable diastereoisomer (IId) has been determined by X-ray analysis. The hydrolysis of compounds (IIa-c) leads to formation of 2-hydroxy-2-oxo-1,3,2-dioxaphosphepines (III). The structure of phosphepine (IIIb) in crystal is shown on the figure. The work is supported by the Leading Scientific School Foundation of Russia (grant N 96-15-97330) and the Russian Foundation for Basic Research (grant N 98-03-33266).