Hypervalent iodine reagents preparative methods

Fukase, K, Kinoshita, I, Kanoh, T, Nakai, Y, Hasuoka, A, Kusumoto, S, A novel method for stereoselective glycosidation with thioglycosides promotion by hypervalent iodine reagents prepared from PhIO and various acids. Tetrahedron, 52, 3897-3904, 1996. 

CF3)2CH0H in 1994 (For details, see Scheme 23). In 2006, Nishiyama et al. also used the hypervalent iodine reagent prepared from iodobenzene under electrolytic conditions and developed a new method for the synthesis of tetrahydroquinolines (Scheme 8). Thus, the reaction of the methoxyamide 16 with the active species... 

Various [hydroxy(tosyloxy)iodo]arenes 64 can be conveniently prepared by a ligand-exchange reaction of (diacetoxyiodo)arenes with p-toluenesulfonic acid monohydrate in acetonitrile (Scheme 2.26). This method has been apphed to the synthesis of derivatives with various substituted aromatic groups [150,166,186,209, 210], [hydroxy(tosyloxy)iodo]heteroarenes [206] and the recyclable hypervalent iodine reagents 65-68 (also see Chapter 5) [154,155,158]. Similarly, numerous polylluoroalkyl derivatives of the types C F2 +iI(OH)OTs [135,176,211] andC F2 +iCH2l(OH)OTs [176,212] can be prepared from the respective bis(trifluoroacetates) and p-toluenesulfonic acid. 

A simple method for the preparation of a-azido ketones and esters 500 in good yields by direct azidation of carbonyl derivatives 499 at the a-carbon using 4,4 -bis-(dichloroiodo)biphenyl and sodium azide has been reported (Scheme 3.198) [575]. The hypervalent iodine reagent, 4,4 -bis-(dichloroiodo)biphenyl, can be easily recycled from the reaction mixture. 

The first polymer-supported hypervalent iodine reagent, poly[(dichloroiodo)styrene], was prepared by chlorination of iodinated polystyrene in the early 1980s [8]. This method, however, involves the initial preparation of iodinated polystyrene under harsh conditions (160 h, 110 °C), requires the use of hazardous chlorine gas and affords poly[(dichloroiodo)styrene] with a relatively low loading of active chlorine. An optimized one-pot preparation of polystyrene-supported (dichloroiodo)benzene 2 (loading of -ICI2 up to 1.35 mmol g" ) from polystyrene 1, iodine and aqueous sodium hypochlorite (bleach) was reported in 2011 (Scheme 5.1) [10]. 

Solvent-free reactions have many advantages such as reduced pollution, lower costs and the simplicity of the processes involved [60]. The solvent-free preparation of several important hypervalent iodine reagents has been reported [61,62], [Hydroxy(sulfonyloxy)iodo]arenes (42) have been prepared in excellent yields by the solid-state reaction simply by grinding (diacetoxyiodo)arenes and appropriate sulfonic acids for several minutes in an agate mortar [61]. Tosyloxy- and mesyloxy benziodoxoles 44 can be prepared by a similar solvent-free procedure starting from 2-iodosylbenzoic acid (43) [61], Likewise, [hydroxy(phosphoryloxy)iodo]arenes 46 have been conveniently prepared by a solvent-free method from (diacetoxyiodo)arenes and phosphate esters 45 (Scheme 6.17) [62],... 

Kita and coworkers reported a novel method to prepare 2,2 -substituted biphenyl compounds using phenyliodine(III) bis(trifluoroacetate) (FIFA), a hypervalent iodine reagent. The substrate for the coupling was first prepared by reacting 1 equiv of di-f-butylsilyl bis(trifluoromethanesulfonate) with 2 equiv of the phenol 46. Di-f-butylsilylene 47 then underwent an intramolecular cyclization in the presence of BF3 -OEt2 to provide the desired tricyclic compound 48. Removal of silylene ether was accomplished by TBAF in excellent yields. This sequence worked well for both 2,2 -disubstituted symmetrical and unsymmetrical biphenyls (eq 17). ... 

Papoutsis et al. and Malamidoli-Xenikaki and Spyroudis developed a method to transform 2-hydroxy-1,4-benzo-quinones, such as 132, into 2-cyclopentene-l,4-diones, like 124 112,113 rpjjg pjojocol is based on the thermolysis of a phenyl iodonium, such as 133, ° " which can be prepared treating a hydroxy quinine 132 with the commercially available hypervalent iodine reagent diacetoxy iodobenzene (PhI(OAc)2) (Scheme 18.29). 

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. 

Polymer-supported hypervalent iodine compounds in general are readily prepared and they have gained recently considerable popularity as reagents for clean oxidations. However, they are not newcomers since they have been known since 1961. A detailed procedure for the iodination of polystyrene and its conversion to poly[(diacetoxyiodo)styrene] appeared in 1972 [85]. However, this and other related methods were time consuming and despite encouraging results did not gain popularity. 

Vinyliodonium ions, 35 and 36, are hypervalent iodine species in which one or two alkenyl ligands are bound to a positively charged iodine(III) atom. Although they are reactive with nucleophilic reagents, they are less labile than alkynyliodonium ions, and stable halide salts of vinyliodonium ions can be prepared. The first vinyliodonium compounds [i.e. (a, / -dichlorovinyl)iodonium salts] were synthesized by the treatment of silver acetylide-silver chloride complexes with (dichloroiodo)arenes or l-(dichloroiodo)-2-chloroethene in the presence of water (equation 152). The early work was summarized by Willgerodt in 1914115. This is, of course, a limited and rather impractical synthetic method, and some time elapsed before the chemistry of vinyliodonium salts was developed. Contemporary synthetic approaches to vinyliodonium compounds include the treatment of (1) vinylsilanes and vinylstannanes with 23-iodanes, (2) terminal alkynes with x3-iodanes, (3) alkynyliodonium salts with nucleophilic reagents and (4) alkynyliodonium salts with dienes. 

In our total synthesis of discorhabdin A, the A,(9-acetal compound 96 acted as a key compound for the construction of the A,5-acetal compound (see Scheme 31), and was prepared by the oxidative fragmentation reaction of an a-amino alcohol 95 initially using the highly toxic lead tetraacetate. We then developed a new method using the low toxic hypervalent iodine(III) reagent. Thus, the reaction of the... 

A convenient and mild experimental procedure for the preparation of (diacetoxyiodo)arenes using Select-fluor as the oxidant in acetic acid has been developed by Shreeve and coworkers [33]. This method, in particular, has been utilized in the syntheses of a chiral hypervalent iodine(III) reagent having a rigid spiro-biindane backbone [134] and the C2-symmetric chiral (diacetoxyiodo)arene 35 from the respective iodide 34 (Scheme 2.15) [169,170]. 

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