Hypervalent iodine compounds bonding

V. V. Zhdankin, in his chapter, summarizes the use of hypervalent iodine reagents for carbon-carbon bond formations. The generation of radicals with hypervalent iodine compounds is used in decarboxylative alkylations of organic substrates, whereas phenols and phenol ethers seem to be ideal substrates for... 

This chapter presents methods of preparation for hypervalent iodine compounds with an emphasis on those which serve as reagents. In order to facilitate classification the families of compounds have been divided according to the type of bonds attached to iodine. Procedures described in Organic Syntheses will be only briefly mentioned. 

Such additions of nucleophiles to non-activated double bonds mediated by hypervalent iodine compounds are also possible in other cases (Section 3.5). This umpolung of reactivity is due to the formation of an adduct with hypervalent iodine which renders this intermediate highly electrophilic. In this way 6-propionylflavo-nols gave 1,2-dimethoxy-adducts in methanol-perchloric acid [10] ... 

Reactions of alkenes with hypervalent iodine compounds lead mostly to vicinally functionalised alkanes. This is the case with PhI(OAc)2, PhIO, PhI(OH)OTs, PhI(OTf)0(TfO)IPh and other related reagents.230,231,233,239-247 poj. example, treatment of alkenes with PhI(OH)OTs, (HTIB), affords vie bis(tosyloxy)alkanes with a syn stereospecificity.239,241 n generally admitted that this reaction proceeds by the electrophilic attack of the hypervalent iodine species on the ethylenic double bond to afford a carbonium ion intermediate (140). This intermediate undergoes two consecutive Sn2 substitution reactions to eventually give the final products. (Scheme 5.17)... 

Alkyl hypochlorites and hypobromites are relatively stable molecules alkyl hypoiodites can only be prepared in situ, usually by the reaction of alcohols with metal acetates or oxides and iodine or by the reaction of alcohols with a hypervalent iodine compound and iodine.1319 Alkyl hypochlorites and hypoiodites can be utilized in reactions that parallel those of the organic nitrites (Barton reaction Section 6.4.2). For example, the photochemistry of the steroidal hypoiodite 497, prepared by the reaction of the corresponding alcohol with iodine oxide (I2O) generated from mercury(II) oxide and molecular iodine in situ, affords a new five-membered ring via an O I bond fission, 1,5-hydrogen abstraction and substitution (Scheme 6.244).1353... 

A pyrrolone ring is formed from a methylene and a ring-carbon in a low-temperature cyclo-oxidation of the amide (104.2) which is promoted by [bis(tri-fluoroacetyloxy)iodo]benzene. The application of hypervalent iodine compounds to the formation of C—C bonds has been reviewed [3714]. A similar compound (104.3) is cyclized in lower yield by stirring it at 0 C with trifluoroacetic anhydride. 

Only 2-pyridyl reverse C-nucleosides are known. Coupling saccharide free radicals 831 and 834 with protonated pyridine derivatives gave the 2-pyridyl reverse C-nucleosides 832 and 835, respectively. Free radical 831 was obtained by decarboxylative photolysis of the uronic acid derivative 830 in the presence of hypervalent iodine compounds (92TL7575 (Scheme 232), whereas free radical 834 was obtained by thermal homolysis of the carbon-iodine bond in the 6-iodo-6-deoxy-o-galactopyranose derivative 833 in the presence of benzoyl peroxide (93JOC959) (Scheme 233). 

The self-assembly of hypervalent iodine compounds to form macrocyclic trimers was studied using MO calculations. The principal driving force for the self-assembly of iodonium units is the formation of secondary bonding interactions between iodonium units as well as a rearrangement of primary and secondary bonding around iodine to place the least electronegative substituent in the equatorial position for every iodine in the... 

The structure and reactivity of several specific classes of hypervalent iodine compounds have been investigated theoretically. Varvoglis, Tsipis and coauthors have studied the geometry and electronic stmcture of some hypervalent iodine compounds PhIX2 by means of extended Hlickel and CNDO/2 quantum chemical approaches [200], The bonding was analyzed in terms of both the model of delocalized MOs on the basis of interactions between fragment MOs derived from EHMO-SCCC calculations and that of localized MOs derived by the CNDO/2 method. The ability of these compounds to afford c -addition products with alkenes via a synchronous molecular addition mechanism was found to be theoretically feasible [200]. 

Aziridines are key structural motifs present in natural products such as mitomycins and azinomycins and versatile building blocks which can undergo various useful transformations. Hypervalent iodine-mediated intramolecular aziridinations of allylic carbamates and reaction of A-tosyliminophenyliodinane (Phi = NTs) with double bonds have been reported to be efficient and practical routes to access these three-membered rings. Allylic carbamates 71 undergo enantioselective aziridine formation on oxidation with chiral binaphthyl hypervalent iodine compound 72 (Scheme 28) [86]. 

In the older Hterature, the derivatives of iodine(III) were termed as iodi-nanes, while the compounds of pentavalent iodine were called periodinanes. According to the 1983 lUPAC recommendations (1984PAC769), these names were replaced by X -iodanes for iodine(III) and by X -iodanes for iodine(V) compounds. In the lambda nomenclature, the symbol X" is used to indicate any heteroatom in a nonstandard valence state (n) in a formally neutral compound for iodine the standard valence state is 1. The lambda terminology is broadly used in the modem hterature to indicate the general type of hypervalent iodine compounds and to specify the number of primary bonds at the iodine atom. 

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