Hypervalent iodine in synthesis 92. A facile synthesis of 3-substituted-5,6-dihydroimidazo[2,1-b]thiazoles by cyclocondensation of alkynyl(phenyl)iodonium salts and imidazolidine-2-thione

A simple method for the synthesis of 3-substituted 5,6-dihydroimidazo[2,1-b]thiazoles is achieved by cyclocondensation of alkynyl(phenyl)iodonium salts with imidazolidine-2-thione.

Hypervalent Iodine in Synthesis. 94. A Facile Synthesis of 2-Substituted-imidazo[1,2-a]pyridines by Cyclocondensation of Alkynyl(phenyl) iodonium Salts and 2-Aminopyridine

A facile method for the synthesis of 2-substituted-imidazo[1,2-a]pyridines is achieved by cyclocondensation of alkynyl(phenyl)iodonium salts with 2-aminopyridine.

Hypervalent iodine in synthesis 93. A facile synthesis of 2-substituted imidazo[1,2-a]pyrimidines by cyclocondensation of alkynyl(phenyl)iodonium salts and 2-aminopyrimidine

Simple stirring of a mixture of the alkynyl(phenyl)iodonium salts 1 with 2-aminopyrimidine 2 in chloroform under reflux for two hours in the presence of K2CO3 gave, after workup, the 2-substituted imidazo[1,2-]pyrimidines 3 in moderate to good yields. A possible mechanism for the formation of 3 involves the intramolecular cyclization of the intermediate alkylidenecarbene 6.

Hypervalent iodine in synthesis. 90. A mild and efficient method for the iodination of pyrazoles

The combined reagent of iodobenzene diacetate (or polymer-supported iodobenzene diacetate) with iodine was used as an effective iodinating agent of pyrazoles to the corresponding 4-iodopyrazole derivatives at room temperature with high yields.

Hypervalent iodine in synthesis 91: a mild and efficient method for the halogenation of 6-methyluracil derivatives

The combined reagent of iodobenzene diacetate (or polymer-supported iodobenzene diacetate) with iodine or bromine was used as an effective halogenative agent of 6-methyluracil derivatives to the corresponding 5-halo-6-methyluracil derivatives at room temperature with high yields.

Hypervalent iodine in synthesis 64:Syntheses of diaryl selenides and alkyl aryl selenides by palladium-catalyzed arylation of areneselenyl or alkaneselenyl magnesium bromide with diaryliodonium salt

Areneselenyl or alkaneselenyl magnesium bromide reacts rapidly with diaryliodonium salt to give the corresponding diaryl or alkyl aryl selenide in the presence of catalytic amounts of Pd-(PPh3)4 in good yield.

The geochemistry of radioactive waste disposal

The present study attempted to identify the significant parameters which affect radionuclide migration from a low level radioactive waste disposal site located in a clay deposit. From initial sorption studies on smectite minerals, increased Kd with decreasing initial cation concentration was observed, and three sorption mechanisms were identified. The observation of anion dependent sorption was related to the existence of a mechanism in which an anion-cation pair are bound to the clay surface through the anion. The influence of competing cations, typical of inorganic groundwater constituents, depended on: (1) Ni/Co:Mn+(Mn+ = competing cation) ratio, (2) nature of M^n+, (3) total solution ionic strength. The presence of organic material in groundwater is well documented, but its effect on cation sorption has not been established. An initial qualitative investigation involving addition of simple organic ligands to Ni(Co)-hectorite samples demonstrated the formation of metal complexes in the clay interlayers, although some modified behaviour was observed. Further quantitative examination involving likely groundwater organic constituents and more comprehensive physical investigation confirmed this behaviour and enabled separation of the organic compounds used into two classes, according to their effect on cation sorption; (i) acids, (ii) amine compounds. X-ray photoelectron spectroscopy, scanning electron microscopy and Mossbauer spectroscopy were used to investigate the nature of transition metal ions sorbed onto montmorillonite and hectorite. Evidence strongly favoured the sorption of the hexaaquo cation, although a series of sorption sites of slightly different chemical characteristics were responsible for broadened peak widths observed in XPS and Mossbauer investigations. The surface sensitivity of XPS enabled recognition of the two surface sorption sites proposed in earlier sorption studies. Although thermal treatment of Fe^3+/Fe^2+-hectorite samples left iron atoms bonded to the silicate sheet structure, Mossbauer evidence indicated the presence of both ferric and ferrous iron in all samples.

Novel reaction products from the hypervalent iodine oxidation of hydroxylated stilbenes and isoflavones

Novel reaction pathways for the hypervalent iodine-mediated oxidation of bioactive phenols containing extended conjugated π-systems are described. Oxidation of 4-hydroxystilbenes in methanol using a hypervalent iodine-based oxidant led to the formal 1,2-addition of methoxy groups across the central stilbene double bond. Treatment of the structurally related 4-hydroxyisoflavone with di(trifluoroacetoxy)iodobenzene leads to the surprising formation of 2,4′-dihydroxybenzil. Potential mechanisms for these new reaction pathways are discussed, and the X-ray crystal structure of 2,4′-dihydroxybenzil is presented. In contrast, oxidation of the corresponding 3-hydroxystilbenes and 3-hydroxyisoflavone led to conventional dienone oxidation products. The antitumour implications of these oxidation processes are briefly highlighted; the novel 4-substituted phenolic oxidation products were found to be inactive in terms of in vitro antitumour cellular activity, whereas the 3-substituted phenol products gave novel agents with potent and enhanced antitumour activity in the HCT 116 cancer cell line. © The Royal Society of Chemistry 2005.