Iodonium salts structure

Complex (24) isolated from the reaction of (5) and 1, reveals the co-crystalliza-tion of both a spoke structure and an iodonium salt structure. This leads to the conclusion that an equilibrium as shown in Scheme 13.2, is established in solution. 

Arylethynyl(phenyl)iodonium salts, RC=CI+Ph 4-MeC6H4S03-, react as 1,3-dipolarophiles with nitrile oxides R CNO to afford phenyl(substituted isox-azolyl)iodonium salts 210, which give iodoisoxazoles on reaction with nucleophiles. The crystal structure of 210 (R = Ph, R1 = mesityl) has been determined (369). 

Levothyroxine is used to treat hypothyroidism (an underactive thyroid gland). Thyroid hormone can be made from beef and pork thyroid, but this lacks standardization and it is difficult to control dosage. The synthetic drug is more desirable. Levothyroxine is one of two important thyroid hormones. It is converted into the second important hormone, liothyronine, in the body. The key step in the synthesis of structures such as levothyroxine is the substitution of an iodonium salt by an iodinated phenol. Siql-like reactions on an aromatic ring are not common, but an iodonium salt provides a good leaving group. 

Tributylstannanes have also been used in the synthesis of alkynyl(aryl)iodonium salts, including 1,3-diynyl derivatives373 and the parent member of the family, HC=CIPh+TfO, which was characterized by X-ray structure analysis.374 The bisphenyliodonium triflate reagent 152 [Eq. (4.110)]372 and analogs375 were synthesized in a similar way. Alkynyltrimethylsilanes may also serve as similar useful starting materials.376,377 X-ray characterization of a variety of alkynyl(aryl)iodonium ion has been reported.332... 

The pareitropone project began quite by accident after an unexpected observation expanded our thinking about potentially accessible targets for alkynyliodonium salt/alkylidenecarbene chemistry (Scheme 18). Treatment of the tosylamide iodonium salt 125 with base under standard conditions was designed to provide no more than routine confirmation of the aryl C-H insertion capabilities, which were first exposed in indoleforming reactions using tosylanilide anion nucleophiles and propynyl(phenyl)iodonium triflate,5b of the intermediate carbene 126. However, this substrate did not perform as expected, since only trace amounts of the 1,5 C-H insertion product 127 was detected. One major product was formed, and analysis of its spectral data provided yet another surprising lesson in alkynyliodonium salt chemistry for us. The data was only consistent with the unusual cycloheptatriene structure 129. 

The stable (arylsulfonylmethyl)iodonium salts 49 and 50 can be conveniently prepared in two steps starting from the readily available iodomethyl sulfones 47 (Scheme 23) [41]. Iodonium salts 49 and 50 are not moisture sensitive, can be purified by crystallization from acetonitrile, and can be stored for several months in a refrigerator. The structure of iodonium triflate 50 was unambiguously established by a single crystal X-ray analysis [41]. 

Alkynyl(phenyl)iodonium salts have attracted a significant interest as stable and readily available powerful alkynylating reagents. The preparation, structure, and chemistry of alkynyliodonium salts was extensively covered in a recent review [4]. 

Iodonium salts with a hydroxyl or a carboxyl group are readily converted into their inner salts, i.e. zwitterionic compounds of various types. 2-(Phenyliodonio) benzoate, whose structure may be cyclic, belongs to this category it is prepared from o-iodobenzoic acid upon oxidation and coupling with benzene (or arenes) [51], On strong heating, iodobenzene and carbon dioxide are eliminated, with formation of benzyne ... 

Single-crystal X-ray structures of six alkynyliodonium compounds, all containing oxyanions and including four alkynyl(phenyl)iodonium salts, one alkynylbenziodoxolone and one dialkynyliodonium salt, have been reported. Selected structural data for these compounds are given in Table 3. 

The hypervalent iodine reagents discussed in this article are derived from iodoarenes and, for clarity of treatment, are separated into standard structural categories namely, the aryl-k3-iodanes, 1 and 2, the iodonium salts, 3-5, the iodonium ylides, 6 and 7, and the aryl-/.5-iodanes, 8 and 9. 

A photonic three-dimensional (3-D) crystal-type structure of a brominated thiirane/iodonium salt/ coumarin resin showed that it has a woodpile structure <2004JPST115>. 

A Practical Approach to Quantitative Metal Analysis of Organic Matrices The structures for iodonium salts and Bronsted acid precursors are ... 

Benzene formed from photolysis of the 1 1 complex is a cage-escape product from 3(Jul-CHO+ /Ph ). Benzene formed from the photolysis of the 2 1 complex is an in-cage product from 3((Jul-CHO)2 /Ph ). The formation of 2 1 complexes of amino-substituted ketones and iodonium salts has been suggested to account for the high photosensitivity of polymeric Mannich bases with iodonium salts [102]. Formation of 2 1 donor iodonium cation complexes has been rationalized by consideration of the crystal structures of diphenyliodonium halides, which crystallize as dimers with square planar iodine atoms with two bridging halide counterions [102,108]. 

To date, six single-crystal X-ray molecular structures of alkynyliodonium compounds have been reported four aIkynyl(phenyl)iodonium salts including the substituted cyanoethynyl salt, one heterocyclic and one dialkynyliodonium salt, all with oxyanions. Key structural data for these compounds are summarized in Table 3-1. 

When di-iodine reacts with heterocycles like thioamides or selonoamides new charge transfer complexes containing iodine are obtained [1-10], Various types of such complexes have been obtained thus far, including so called spoke or extended spoke structures (DS 1 or DS l -1 ) (D is the hgand donor) [1], Also iodine coordinated to two thioamides to form iodonium salts ([DS-I-DS] (Ij) )... 

Iodonium salts R2I+ X generally have a typical distance between iodine and the nearest anion X of 2.6-2.S A and in principle can be considered as ionic compounds with pseudo-tetrahedral geometry about the central iodine atom. However, with consideration of the anionic part of the molecule, the overall experimentally determined geometry is distorted T-shaped structure similar to the -iodanes RIX2. 

A detailed mechanism of the process shown in Scheme 1.3 is unknown. Two general mechanistic pathways, dissociative and associative, have been proposed for the ligand exchange reactions of X -iodanes (Scheme 1.4) [26, 127]. The dissociative pathway seems to be less likely to occur, because of the low stability of the dico-ordinated iodonium ion [PhIL]+ involved in this mechanism [127]. Such iodonium 8-1-2 species, however, have been frequently observed in the gas phase, for example, in mass spectrometry studies of protonated iodosylbenzene, [PhIOH]+ [101], or in the mass spectra of all known iodonium salts, [ArIR]+. The presence of cationic iodonium species in aqueous solution has been confirmed by spectroscopic measurements and potentiometric titrations of PhI(OH)OTs and PhI(OH)OMs [198] however, all available experimental data show that the iodonium species in solution are coordinated with solvent molecules or with available counteranions. X-Ray diffraction analysis of the protonated iodosylbenzene aqua complexes [PhI(H20)0H]+ isolated from aqueous solutions revealed a T-shaped stmcture, ligated with one water molecule at the apical site of the iodine(III) atom of hydroxy(phenyl)iodonium ion, with a near-linear O-I-O triad (173.96°), which is in agreement with a regular X -iodane structure [178]. 

Single-crystal X-ray structures have been reported for the following aryl- and heteroaryliodo-nium salts diphenyliodonium triiodide [412], (2-methylphenyl)(2-methoxyphenyl)iodonium chloride [413], (2-methoxy-5-methylphenyl)(4-methoxy-2-methylphenyl)iodonium trifluoroacetate [414], (2-methoxy-5-methylphenyl)(4-methoxyphenyl)iodonium trifluoroacetate [415], a complex of diphenyliodonium tetrafluoroborate with pyridine [416], a complex of diphenyliodonium tetrafluoroborate with 1,10-phenanthroline [417], a complex of diphenyliodonium tetrafluoroborate with 18-crown-6 [418], 1-naphthylphenyliodonium tetrafluoroborate [419], 3,10-dimethyl-10//-dibenzo[, e]iodinium tetrafluoroborate [420], aryl(pentafluorophenyl)iodonium tetrafluoroborates [421], 4,4 -[bis(phenyliodonium)]-diphenylmethane ditriflate [422], [bis(4-methoxyphenyl)](diethylaminocarbodithioato)iodine(in) [423], di(p-tolyl)iodonium bromide [424], diphenyliodonium chloride, bromide and iodide [425,426], diphenyliodonium nitrate [427], diphenyliodonium tetrafluoroborate [428], thienyl(phenyl)iodonium salts [401], (anft-dimethanoanthracenyl)phenyliodonium tosylate and hexafluorophosphate [429] and 3-mesityl-5-phenylisoxazol-4-yl(phenyl)iodonium p-toluenesulfonate [409]. 

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). 

DesMarteau and coworkers reported the preparation, X-ray crystal structure and chemistry of trifluo-roethyliodonium salts 391 by the reaction of fluoroalkyliodo-bis(trifluoroacetates) 389 with benzene and triflimide acid (390) (Scheme 2.113) [68,531,532], The structure of trifluoroethyl(phenyl)iodonium salt 391 (n = 1) was established by a single-crystal X-ray analysis [68], In contrast to fluoroalkyliodonium triflates 383, compounds 391 are stable to water and can be used as reagents for fluoroalkylation reactions in aqueous media. 

The structure of iodonium triflate 395 was unambiguously established by a single-crystal X-ray analysis [138], The structural data revealed the expected geometry for iodonium salts with a C—I—C bond angle of 91.53°. The I—C bond distances of 2.131 and 2.209 A are longer than the typical bond length in diaryliodonium salts (2.0-2.1 A). The I - O distance between the iodine atom and the nearest oxygen of the triflate anion is 2.797 A. 

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