Iodine generation

Treatment of anions derived from 2-(diphenylmethyl)benzotriazole 447 with iodine generates relatively stable radicals 448 which undergo spontaneous dimerization to adducts 449 (Scheme 73) <1998JOC9992>. When one of the phenyl rings in starting material 447 is substituted in the para position, similar dimerization occurs readily, but it... 

Consequently, the equivalent amount of iodine generated by the above reaction may be conveniently assayed by titration against a standard sodium thiosulphate solution. In this context a point of caution must be observed while KI is being oxidized under a strongly acidic medium so as to avoid simultaneous oxidation of the iodide by atmospheric oxygen that may result high erroneous titer values leading to false estimations. 

Molecular iodine is oxidised in acetonitrile at about the same potential as alkyl iodides. It forms iodine(l), co-ordinated with one molecule of acetonitrile [18]. lodine(l) will oxidise alkyl iodides to form a carbonium ion and molecular iodine. Thus the iodine generated during electrochemical oxidation of an alkyl iodide can function as an electron transfer agent in the latter stages of reaction [19]. 

The chemical dehydrodimcnzaiion of malonate esters can be carried out by the action of iodine on the sodium enolate [23], This route is adapted as an electrochemical process using alcoholic sodium iodide as electrolyte in an undivided cell with carbon electrodes [24, 25]. Base generated at the cathode and iodine generated at the anode serve in a catalytic cycle. 

Alternatively, incorporation of Phe(4-NHBoc) into a peptide is followed by deprotection to regenerate the 4-amino group. Iodination generates the Phe(3,5-I2,4-NH2)-containing peptide, which is then converted into the tritium-labeled Phe(3,5-3H2,4-NH2) for the formation of the [(Asu)21 6,Phe2(3,5-3H2,4-NH2),Arg8]-VP.[31]... 

Epimines. Irradiation of nitroamines and cyanoamines in the presence of phenyliodine(III) diacetate and iodine generates an aminyl radical which undergoes intramolecular hydrogen abstraction to produce epimines. 

The condensation of 3-acetylindole (XXXII) with isoquinoline in the presence of iodine generates a quaternary ketonic compound (XXXIII), and this upon reduction with lithium aluminum hydride furnishes the unstable enamine XXXIV which finally, in an acid medium, cyclizes to XXXI (21, 22). 

Note 3. The ozone generator was a Welsbach model T-408 operated at 95 V. Measurement of ozone concentration at its source, or of unconsumed ozone during sample treatment, may be made by titration of the iodine generated from aqueous potassium iodide solutions placed in downstream bubblers. 

The shortest synthesis of triquinacene is the four-step conversion from cyclo-pentadiene described by Wyvratt and Paquette (Scheme 59).351,352) Oxidative coupling of sodium cyclopentadienide with iodine generated 9,10-dihydrofulvalene (368)3S3,354) which was treated in situ with diethyl azodicarboxylate. The resulting... 

Desilylation. Allylic iodination, generation of 2,2-difluorocyclopropyl anions and... 

The iodine generated coulometrically or present in the reagent can be reduced by oxidizable species such as ascorbic acid, ammonia, thiols, Tl, Sn ", In, hydroxyl amines, and thiosulfite. This results in consumption of F and water determinations that are too high. Phenolic derivatives and bicarbonates also cause reduction of F. 

The iodine generated is prevented from being lost as vapor by ensuring that an excess of potassium iodide is present, which forms the stable ionic complex, KI3. The liberated iodine is measured by the familiar sodium thiosulfate titration, using starch as an indicator near the end point of the titration to sharpen its observation (Eq. 4.21). 

Palladium(0)-catalysed coupling of an orf/to-halophenolic ether (thioether) with a terminal alkyne (or with an alkynylboronic ester ) and ring closure promoted with an electrophile - iodine has been most often used - is an excellent method to make both benzothiophenes °° ° and benzofurans. ortfto-AIkynyl-phenols can be comparably closed with palladium catalysis in the presence of copper(II) halides to give the corresponding 3-halo-benzofurans, ° and ortfto-alkynyl pyridin-2- and -3-yl acetates likewise ring close with iodine, generating furopyridines. ... 

Iodine Addition of iodine generates pits on the surface of the magnesium metal. Additionally. the initial formation of magnesium ]) iodide serves as a start for the attack on the alkyl halide, which then continues as a chain reaction. Instead of adding iodine, preformed Gilman catalyst (prepared hy heating with iodine) can be used. 

A sin e bonding model for a C v symmetry was used. Two equivalent bonding orbitals on the central iodine, generated from the s,Px and Py atomic orbitals, overlap pure p orbitals of the terminal atoms. The remaining orbitals of the central iodine as well as all other atomic orbitals were considered as being filled and non-bonding. 

Hypoiodite-type reaction. Treatment of the allylic alcohol 1 with QHsI (OAc)2 and iodine generates an alkyloxy radical, which undergoes -scission to a followed by cyclization to a cis-hydroazulenone ring system (2). The CH2I group of 2 can be reduced to a methyl group by a catalytic amount of BusSnH (60% yield). Treatment of 2... 

Benzoxazoles have also been aminated with secondary or primary aliphatic amines (1 equiv.) in the presence of catalytic amount of iodine (5 mol%), aqueous f-butyl hydroperoxide (1 equiv.), and acetic acid (1.1 equiv.) at ambient temperature for 12 h [102]. Authors believe that protonation of benzoxazole results in the formation of equilibrium amount of the salt 69, which adds alkylamine to form 2-aminobenoxazoline 70 (Scheme 46). Interaction of 70 with iodine generates 2-amino-3-iodobenzoxazoline 68, which eliminates HI to give the amination product. The reaction cycle is maintained due to oxidation of iodide ions with t-BuOOH. It is important to note that this envirorunentally benign method produces tertiary butanol and water as by-products. Use of iV-iodosuccinimide catalyst in combination with aqueous hydrogen peroxide in acetonitrile solution allows to reduce the reaction time to 4 h [103]. Benzothiazole under the same conditions remaines unchanged. 

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