Iodosyl compounds preparation

Iodosyl compounds can be converted by sulfur tetrafluoride at —20 to — IOC into the corresponding difluoroiodides 24. These same products, e.g. 25, can also be obtained by treatment of bis(trifluoroacetoxy)iodine compounds with sulfur tetrafluoride at 70CC. The reactions are general and may be used for the preparation of aliphatic, aromatic and heterocyclic difluoroiodides.223-224... 

Organic iodosyl compounds usually have a polymeric structure, (RIO) , with a typical, for X -iodanes, T-shaped geometry at the iodine atom no structural evidence supporting the existence of an 1=0 double bond has been reported. Most known iodosyl compounds have low thermal stability and some are explosive upon heating. Iodosyl compounds can be prepared by direct oxidation of organic iodides, or, more commonly, by basic hydrolysis of other iodine(III) compounds. Table 2.4 summarizes the preparation methods for organic iodosyl compounds. 

The iodosyl elimination has been used in the preparation of unsaturated oxazolidinone 635 (Scheme 3.248), the key intermediate in the synthesis of valienamine [662], This reaction proceeds via oxidation of iodide 633 to the intermediate iodosyl compound 634, which spontaneously eliminates HOI to afford product 635. The Reich iodosyl yyn-elimination has also been used for the preparation of intermediate steroidal units of cephalostatin 7 [663],... 

Bis(iodosyl)benzene reacted with triflic anhydride to afford a bis iodine (III) derivative [21], DIB or iodosylbenzene, however, do not afford with triflic acid, or its anhydride, the expected analogues of HTI, although these are initially formed. The reaction of iodosylbenzene and triflic anhydride leads to two different products, depending on reaction time. When triflic acid was allowed to react with iodosylbenzene in dichloromethane for about 20 min the yellow p-compound 1 (m.p. 100-110°C) was obtained it was the same with the so-called Zefirov s reagent, which was originally prepared from DIB and triflic acid in chloroform. When the reaction time was extended to 12 h, then 1 isomerized to the slightly pale yellow compound 2 (m.p. 125-132°C). For preparative purposes the direct reaction of iodosylbenzene with triflic acid was preferable for 2, since it was isolated in 94% yield. 

Iodosyl fluorosulfate, OIOSO2F and the triflate, OIOTf, can be prepared as thermally stable, hygroscopic yellow solids by the reaction of iodine with iodine pentoxide or iodic acid in fluorosulfonic or trifluoromethanesulfonic acids, respectively [5]. Raman and infrared spectra of these compounds indicate a polymeric structure analogous to iodosyl sulfate [5], Iodine tris(fluorosulfate), I(0S02F)3 and tris(triflate), I(OTf)3, are also known [6,26]. I(0S02F)3 can be prepared by the reaction of iodine with peroxydisulfuryl ditluoride [26]. Salts such as KI(0S02F)4 have also been prepared and investigated by Raman spectroscopy [26,27]. I(OTf)3 was prepared from iodine tris(trifluoroacetate) and trifluoromethanesulfonic acid [6]. 

The first six-membered iodine(III) heterocycle, the cyclic tautomer of 2-iodosylphenylacetic acid, 221, was reported in 1963 by Leffler and coauthors [342]. This compound was synthesized by chlorination of 2-iodophenylacetic acid (220) followed by hydrolysis of the initially formed, unstable 2-(dichloroiodo)phenylacetic acid (Scheme 2.67). Compound 221 is stable at room temperature but decomposes in solution at 80-100 °C the proposed cyclic structure 221 is in agreement with its relatively low acidity (pXa = 7.45) [342]. 8-Iodosyl-l-naphthoic acid (222) was prepared by the peracetic oxidation of 8-iodo-1-naphthoic acid [343]. Anions of 2-iodosylphenylacetic acid (221) [328] and 222 [343] have a moderate reactivity in the cleavage of phosphate esters in aqueous micellar solution. The chiral, enantiomerically pure substituted 2-iodosylphenylacetic acid derivatives 223 and 224 were synthesized from the corresponding aryl iodides by oxidation with dimethyldioxirane [344]. 

A very mild and general method for the preparation of diaryl- and heteroaryliodonium triflates is based on iodonium transfer reactions of iodine(III) cyanides with the respective aryl- or heteroarylstannanes [146,148, 399-401]. Specifically, (dicyano)iodonium triflate (277), generated in situ from iodosyl triflate and MesSiCN, reacts with tributyltin derivatives of aromatic and heteroaromatic compounds to afford the corresponding symmetrical iodonium salts under very mild conditions (Scheme 2.80) [389,390]. 

Two structural types of cyanoiodonium salts are known (dicyano)iodonium triflate, (NC)2lOTf [399,400] and aryl(cyano)iodonium derivatives, Arl(CN)X [ 146,460,508,509]. (Dicyano)iodonium uiflate 277 can be prepared by the reaction of iodosyl triflate (375) (Section 2.1.1.2) with cyanotrimethylsilane in dichloromethane (Scheme 2.105). In the solid state, compound 277 is thermally unstable and air-sensitive it completely decomposes at room temperature in 2-5 min forming cyanogen iodine, ICN and explodes when exposed to air. However, it can be stored at -20 °C under nitrogen for several days [400]. Despite its low stability, cyanide 277 can be used in situ for the very mild and efficient preparation of various bis(heteroaryl)iodonium salts by an iodonium transfer reaction with the respective stannylated heteroarenes (Section 2.1.9.1.1). 

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