REACTIONS OF XENON DIFLUORIDE WITH ORGANO-SULPHUR MOLECULES

Abstract

Xenon difluoride readily reacts with various organo-sulphur compounds. In general, three types of products were isolated, the course of the reactions depending on the structure of the organo-sulphur substrate. Alkyl-phenyl substituted sulphides, 3,3-dibromothiochroman-4-one and thiochroman-4-ol reacted to form α-fluoro substituted products, 2,5-diphenyltetrahydrothiopyran-4-one, thiochroman-4-one and 3-bromothiochroman-4-one formed dehydrogenated products, while diphenyl-sulphide, dibenzothiophene and 10-thioxanthenone reacted to form sulphoxide and sulphone. The reaction mechanism and the reaction pathways, which are shown on the Scheme, will be discussed.     

α-Brominatjon of Ketones with the Bromine Complex of Poly(styrene-co-4-vinylpyridine)

The bromine complex of poly(styrene-co-4-vinylpyridine) reacted with ketones and 1,3-diketones to form a -bromo or α,α-dibromo products in high yields     

Synthesis and Properties of Cross-Linked 4-Vinylpyridine-Styrene-Halogen Complexes

Cross-linked 4-vinylpyridine-styrene beads (PVPS) containing various amounts of pyridine rings were synthesized and reaction with methyliodide and peroxyacetic acid gave corresponding N-methylpyridinium salts and N-oxides with more than 92% of the pyridine rings being transformed. PVPS formed stable complexes with bromine and chlorine in the ratio 1:1, and when a higher amount of halogen was used, complexes with two molecules of halogen on each pyridine were formed. Similar complexes were also formed with PVPS-N-oxides in the presence of bromine and chlorine, while the reaction of PVPS-hydrohalide with bromine and chlorine resulted in hydrobromide perbromide and hydrochloride perchloride resins. The chemical activity of halo-substituted resins was tested in the reaction with 1,1-diphenylethylene. Chi or o-substituted resins are very stable, while bromo-substituted beads gave bromoalkene, dibromide, and alkoxybromide, depending on the structure of the reagent, solvent, and reaction temperature.     

Kohonen classification applying ‘missing variables’ criterion to evaluate the p‐boronophenylalanine human‐body‐concentration decreasing profile of boron neutron capture therapy patients

The irradiation dose in tumor and healthy tissue of a boron neutron capture therapy (BNCT) patient depends on the boron concentration in blood. In most treatments, this concentration is experimentally determined before and after irradiation but not while irradiation is being carried out because it is troublesome to take the blood samples when the patient remains isolated in the irradiation room. A few models are used to predict the boron profile during that period, which until now involves a biexponential decay. For the prediction of decay concentration profiles of the p‐boronophenylalanine (BPA) in the human body during BNCT treatment, a Kohonen‐based neural network method is suggested. The results of various (20 × 20 × 40 Kohonen network) models based on different trainings on the data set of 67 concentration sets (profiles) are described and discussed. The prediction ability and robustness of the modeling method were tested by the leave‐one‐out procedure. The results show that the method is very robust and mostly independent of small variations. It can yield predictions, root mean squared prediction error (RMSPE), with a maximum of 3.30 µg g⁻¹ for the present cases. In order to show the abilities and limitations of the method, the best and the few worst results are discussed in detail. It should be emphasized that one of the main advantages of this method is the automatic improvement in the prediction ability and robustness of the model by feeding it with an increasing number of data. Copyright © 2011 John Wiley & Sons, Ltd.     

Remarkable effect of water on functionalization of the phenyl ring in methyl-substituted benzene derivatives with F-TEDA-BF4

Various N-F reagents reacted with hexamethylbenzene (1) forming side chain substituted alkoxides or esters in protic solvents, Ritter type side chain functionalization was observed in acetonitrile in the presence of trifluoroacetic acid, while in aqueous acetonitrile solution phenyl ring transformation took place, starting with ipso attack of water and further rearrangement of the methyl group as the main process. Rearranged 2,3,4,5,6,6-hexamethylcyclohexa-2,4-dienone (7) was transformed to 5-fluoro-2,3,5,6,6-pentamethyl-4-methylenecyclohex-2-en-1-one (8) or 5-hydroxy-2,3,5,6,6-pentamethyl-4-methylenecyclohex-2-en-1-one (9). 1,2,3,4,5,6-Hexamethyl-bicyclo[2.2.0]hexa-2,5-diene reacted with F-TEDA-BF4 in the presence of water and 7 was formed in high yield. Durene (12) followed similar ipso attack of water as 1, but on the other hand 1,2,3,4-tetramethylbenzene displayed different regioselectivity and 2,3,4,5-tetramethylphenol was formed, further transforming to 4-fluoro-2,3,4,5-tetramethylcyclohexa-2,5-dienone. The functionalizations of methylbenzenes obeyed a second-order rate equation v = d[N-F]/dt = k2[N-F][substrate], and DeltaG# values between 77 and 94 kJ/mol were determined. The presence of water did not significantly influence DeltaG# but considerably affected DeltaS# and positive values were found where methyl group migration was the dominant process (9.1 J/(mol K) for 1 and 0.5 J/(mol K) for 12). A higher reactivity of durene than mesitylene (k2(MES)/k2(DUR) = 0.23) was found, supporting the assumption that single electron transfer (SET) is the dominant process in the functionalizations of methyl-substituted benzene derivatives with F-TEDA-BF4.     

Iodine as a catalyst for efficient conversion of ketones to gem-dihydroperoxides by aqueous hydrogen peroxide

Iodine has been shown to be an efficient catalyst for the selective dihydroperoxidation of ketones with aqueous hydrogen peroxide. Ketones were directly converted to their corresponding gem-dihydroperoxides using a "green" oxidant (30% aq H(2)O(2)) and a simple catalyst (iodine) under neutral conditions in acetonitrile. The yield of hydroperoxidation of various cyclic ketones was 60-98% including androstane-3,17-dione, and acyclic ketones were converted with a similar efficiency. [reaction: see text]     

Role of the Polymer Backbone in the Oxidative Properties of Polymer-Supported Dichromate

Crosslinked co/poly(styrene-4-vinylpyridine)/ (1) was converted with hydrogen bromide or alkyl bromide to a pyridinium salt (2) which was further converted in water medium to various immobilized dichromates (3) with CrO₃. The insoluble reagent containing 0.6–1.0 mmol of dichromate on a gram of resin (depending on the structure of the polymer backbone) oxidized several secondary alcohols to ketones. The rate of conversion of alcohols to ketones depended on the structure of the polymer backbone, the structure of the alcohol, and the amount of water (5% or 20%) occluded in the reagent 3.     

One loop scalar functions in the heavy-quark effective theory

We find general solutions for the dimensionally regularized scalar one-loop three-point and four-point functions with one heavy-quark propagator. The scalar one-point function vanishes, while the expression for the two-point function has been found before. For the latter we give a detailed derivation. We also discuss some special cases and compile useful formulae. Received: 15 February 2002 / Revised version: 15 April 2002 / Published online: 12 July 2002