Iodine derivatives, hypervalent

CF,C02)2lPh, H2O, CH3CN, 85-99% yield. In the presence of ethylene glycol the dithiane can be converted to a dioxolane (91% yield) or in the presence of methanol to the dimethyl acetal. The reaction conditions are not compatible with primary amides. Thioesters are not affected. A phenylthio ester is stable to these conditions, but amides are not. The hypervalent iodine derivative l-(t-butylperoxy)-l,2-benziodoxol-3(l/f)-one similarly cleaves thioketals."... 

In a similar manner these hypervalent iodine derivatives promote the addition of the non-nucleophilic 4-nitrofur-azan-3-olate functions to cycloalkenes to give product 210 (Scheme 49) <2001RCB2479>. 

Collections of fundamental and thermodynamic data can be found in an earlier review [158] and in standard resources [13, 14]. However, due to the reactivity of iodine there are many less common or more reactive forms of iodine that have been less well characterized. For example, a blue 12 cation, a brown I3+, or a green I5+ cation are formed in concentrated sulfuric acid and 1+ is stabilized in donor environments such as pyridine [159]. So-called hypervalent iodine reagents have been developed as a versatile oxidation tool in organic synthesis and often iodine derivatives are employed as electron transfer catalysts. Some fundamental thermodynamic data and typical applications of iodine are summarized in Scheme 5. 

Both sarin and soman react with aqueous KHSO5 to produce the corresponding phosphonic acids (Yang et al., 1992). Valuable studies of the use of hypervalent iodine derivatives (below) to hydrolyze phosphorus esters have been reported (Moss et al., 1983, 1984, 1986 Katritzky et al., 1988). 

In the case of perfluoroalkyl iodides the relatively stable hypervalent iodine derivatives of type RfI(0S02F)2 can be isolated they are also readily transformed into the corresponding fluoro-sulfates Rf0S02F. ... 

Perhaps inspired by the 1903 discovery by Tschemiac that phthalimide affords anthranilic acid upon exposure to iodosobenzene (iodosylbenzene), several workers have explored different hypervalent iodine reagents in what has become the most widely adopted variation of the HR. Iodosobenzene itself continues to find use e.g., 25— 26, although hypervalent iodine derivatives are more frequently employed (vide infra). 

The noncyclic CF3-substituted trivalent iodine derivatives lack stability and cannot be isolated at room temperature however, the incorporation of a hypervalent iodine atom into a five-membered heterocycle has a significant stabilization efiect. The synthesis of stable trifluoromethylbenziodoxoles 141 and 143—145 by treatment of the corresponding methoxybenziodoxole... 

Under certain conditions, amides can add directly to alkenes to form N-alkylated amides. 3-Pentenamide was cyclized to 5-methyl-2-pyrrolidinone by treatment with trifluorosulfonic acid. Acylbydrazine derivatives also cyclized in the presence of hypervalent iodine reagents to give lactams. When a carbamate was treated with Bu3SnH, and AIBN, addition to an alkene led to a bicyclic lactam. 

A Sml2-induced reductive cyclization of (V-(alkylketo)pyrroles provided an entry into medium ring 1,2-annelated pyrroles <06EJO4989>. An oxidative radical alkylation of pyrroles with xanthates promoted by triethylborane provided access to a-(pyrrol-2-yl)carboxylic acid derivatives <06TL2517>. An oxidative coupling of pyrroles promoted by a hypervalent iodine(III) reagent provided bipyrroles directly <060L2007>. 

A series of benzisothiazolone derivatives 238 has been prepared from methylthiosalicylate 235 O60L4811>. The key cyclization step features the formation of a TV-acylnitrenium ion 237, generated by the hypervalent iodine reagent, phenyliodine(III)bis(trifluoroacetate) (PIFA). This ion cyclizes to benzisothiazol-3-one 238 upon intramolecular trapping of the thiol moiety. 

In these latter compounds, the hypervalent iodine may be associated with oxyanions such as perchlorate, trifluoroacetate, and triflate, as verified by the crystal structure of the trifluoroacetate derivative (41). It seems likely that the mode of binding of... 

Effective synthesis of spiroisoxazoline derivatives was elaborated using hypervalent iodine reagents. Thus, treatment of o-phenolic oximes 217 with phenyliodonium diacetate (PIDA) in MeCN at 0°C afforded spiroisoxazoUnes 218 in moderate yields (equation 94) . Oximes 219, prepared in situ from 2-trifluoromethylchromones, in the acidic media also led to spiroisoxazoUnes 220 (equation 95) . ... 

Kita, Y. Tohma, H. Inagaki, M. Hatanaka, K. Yakura, T. (1992) Total synthesis of discorhabdin C a general aza spiro dienone formation from O-silylated phenol derivatives using a hypervalent iodine reagent. J. Am. Chem. Soc., 114,2175-80. 

The AuCl-catalysed 4 + 2-cycloaddition of benzyne with o-alkynyl(oxo)benzenes produced anthracene derivatives having a ketone in the 9-position, in good to high yields under mild conditions.118 Hypervalent iodine compounds, [5-acyl-2-(trimethyl-silyl)]iodonium triflates, readily yielded acylbenzynes which could be trapped with furan.119 Both DMAD and benzyne reacted with borabenzene to yield substituted borabarrelenes and borabenzobarrelenes, respectively.120... 

A novel hypervalent iodine-induced direct intramolecular cyclization of a-(aryl)alkyl-jS-dicarbonyl compounds 33 has been recently reported (Scheme 15) [30]. Both meta- and para-substituted phenol ether derivatives containing acyclic or cyclic 1,3-dicarbonyl moieties at the side chain undergo this reaction in a facile manner affording spirobenzannulated compounds 34 that are of biological importance. 

The five-membered hypervalent iodine heterocycles, benziodoxoles, are commonly used as convenient radical precursors [3,33]. The main advantage of benziodoxoles over the non-cyclic hypervalent iodine reagents is the higher thermal stability allowing the preparation of otherwise unstable derivatives with I-Br, I-OOR, I-N3, and I-CN bonds. The stable cyanobenziodoxoles 36-38 are prepared in one step by the reaction of cyanotrimethylsilane with the respective hydroxybenziodoxoles 35 (Scheme 16) [34, 35], or from acetoxybenziodoxole... 

Recent progress on the use of hypervalent iodine reagents for the construction of carbon-het-eroatom (N, O, P, S, Se, Te, X) bonds is reviewed. Reactions of aryl-A3-iodanes with organic substrates are considered first and are loosely organized by functional group, separate sections being devoted to carbon-azide and carbon-fluorine bond formation. Arylations and alkenyla-tions of nucleophilic species with diaryliodonium and alkenyl(aryl)iodonium salts, and a variety of transformations of alkynyl(aryl)iodonium salts with heteroatom nucleophiles are then detailed. Finally, the use of sulfonyliminoiodanes as aziridination and amidation reagents, and reactions of iodonium enolates formally derived from monoketones are summarized. 

The use of hypervalent iodine reagents for heteroatom-heteroatom bond forming reactions is well established in the context of classical oxidation chemistry [1-11]. For example, oxidations of anilines to azobenzenes, thiols to disulfides, and sulfides to sulfoxides with aryl-A3-iodanes were documented decades ago [1-5]. During the last ten years, particular attention has also been given to oxidative transformations of compounds derived from heavier elements, including the interception of reaction intermediates or initially formed products with external nucleophiles. A second important development is the utilization of sulfonyliminoiodanes, ArI = NS02R, for heteroatom-nitrogen bond formation, especially for imidations of sulfur, selenium, phosphorus and arsenic com-... 

The oxidation of phenols with hypervalent iodine compounds has been used frequently and nucleophilic additions can be performed as well as cyclization reactions using this technique. The resulting quinone derivatives show high reactivity and they have been used in a various subsequent reactions. Substituted phenols like 32 [78] or 34 [79] have been oxidized by hypervalent iodine reagents and, depending on the substitution pattern, cyclizations have taken place as shown in Scheme 16. Product 33 is unstable and undergoes subsequent... 

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