Iodosobenzene,

Iodosobenzene explodes violently at about 220°, so that determinations of the melting point should not be attempted. It may, however, be converted into iodobenzene diacetate in the following manner. Dissolve 2 g. of iodosobenzene in 6 ml. of glacial acetic acid boiling is usually necessary. Cool. The resulting diacetate is readily soluble in acetic acid but is insoluble in ether. Add about 50 ml. of ether in order to precipitate the iodobenzene diacetate. Filter and wash with ether. The yield is 

It may be recrystallised from benzene, and will keep indefinitely (unlike the iodobenzene dichloride). 

It may be lecrystallised from benzene, and wiU keep indefinite V (unlike the Mobenzene dichloiide). 

Fit up a 1-litre round-bottomed flask for steam distillation (Fig. II, 40,1) and place in it 22 g. of iodosobenzene (Section IV,25) made into a thin paste with water (1). Steam distil until almost all the iodobenzene has been removed (about 9 g.) cool the residue in the flask at once, filter the white solid with suction and dry in the air. Wash it with a little chloroform, filter with suction, and dry in the air upon filter paper. The yield is 10-6 g. It may be recrystallised from 800-900 ml. of water, lodoxybenzene melts with explosive decomposition at 237°. 

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Alternatively, if it is not desired to collect the iodobenzene, the iodosobenzene can be added to about 150 ml. of water contained in an open beaker or conical flask, and the mixture gently boiled until a clear solution is obtained and the pale yellow colour has disappeared. On cooling the iodoxybenzene rapidly separates. 

This is converted by aqueous sodium hydroxide into iodosobenzene (II) C.HjICl, + 2NaOH —> CgHjI- 0 (II) + 2NaCl + H,0... 

Iodosobenzene undergoes a slow change on keeping this change can be accelerated by heat and consists in a disproportionation to iodoxybenzene (III) and iodobenzene ... 

I) Iodosobenzene when heated directly may decompose with explosive violence, particularly when dry. 

The perruthenate procedure (Entry 2) is also based on a general amine to imine oxidation. The iodosobenzene method (Entry 3) is an application of a... 

Another useful reagent for the preparation of alkynyl lodonium Inflates is [cyano(trifluoromethylsulfonyloxy)(phenyl)]iodine [/i7, 138, 139, 140] prepared from iodosobenzene, trimethylsilyl tnflate, and trimethylsilyl cyanide (equation 71). This reagent reacts with various stannylacetylenes under very mild conditions to form the corresponding alkynyl iodonium salts in high yields [139] (equation 72)... 

Generally yields are good. R can be alkyl or aryl. Modern variants of the Hofmann rearrangement use lead tetraacetate" or iodosobenzene instead of hypo-bromite. 

Low yields of the 5-acetyl-l0,11-epoxy derivative 11 (R = Me) are also obtained by oxidation of 5-acetyl-5//-dibenz[/>,/]azepine (10, R = Me) with iodoxybenzene and vanadium(lll) acetylacetonate, and with iodosobenzene and iron(lll) porphyrin.220... 

The purity of the iodosobenzene depends on the purity of the diacetate used. 

Iodosobenzene has been prepared by the action of sodium or potassium hydroxide solution on iodobenzenc dichloride and by addition of water to the dichloride.5... 

This method of preparing iodosobenzene is preferable to older ones based on iodosobenzene dichloride because iodosobenzene diaeetate2 is more stable and more conveniently prepared than the dichloride 3 and the overall yield is greater (75% versus 54%). 

Willgerodt4 prepared iodosobenzene diacetate by adding chlorine to iodobenzene and hydrolyzing the dichloride to iodosobenzene, which was then reacted with acetic acid. Pausacker 6 used this method to synthesize a number of analogs but found it... 

Iodosobenzene diacetate is best prepared by the action of peracetic acid and acetic acid on iodobenzene. The present procedure is superior to earlier ones 5-8 because it uses inexpensive, commercially available peracetic acid, is faster, and gives higher yields. The procedure seems general for aiyl iodides with electron-releasing substituents, for the submitters have obtained good yields of diacetates from o-, m- and />-iodoto uene, 2- and 4-iodo-wt-xyiene, 2-iodo-/>-xylene, o-iodophenetole, and 4-iodobi-phenyl. 

Iodosobenzene diacetate is used as a reagent for the preparation of glycol diacetates from olefins,9 for the oxidation of aromatic amines to corresponding azo compounds,10 for the ring acetylation of N-arylacetamides,11 for oxidation of some phenols to phenyl ethers,12 and as a coupling agent in the preparation of iodonium salts.13 Its hydrolysis to iodosobenzene constitutes the best synthesis of that compound.14... 

For a source and the specifications of 40% peracetic acid and precautions in handling it, see Notes 3 and 1 under the preparation of iodosobenzene diacetate, p. 62. 

The major by-products in this reaction are iodobenzene and iodosobenzene diacetate. An excess of 20 ml. of peracetic acid over the 65 ml. recommended results in an increase in the amount of iodobenzene. Both impurities are removed from the product by washing with chloroform. 

Iodoxybenzene has been prepared by the disproportionation of iodosobenzene,4Hi by oxidation of iodosobenzene with hypo-chlorous add or bleaching powder,7 and by oxidation of iodobenzene with hypochlorous acid or with sodium hydroxide and bromine.8 Other oxidizing agents used with iodobenzene include air,3 chlorine in pyridine,9 Caro s acid,19-11 concentrated chloric acid,15 and peracetic acid solution.13 Hypochlorite oxidation of iodobenzene dichloride has also been employed.14... 

Peracetic acid, far oxidation of iodo-benzene to iodosobenzene diacetate, 43, 62... 

Two azido groups can be added to double bonds by treatment with sodium azide and iodosobenzene in acetic acid." ... 

Silyi enol ethers can be dimerized to symmetrical 1,4-diketones by treatment with Ag20 in DMSO or certain other polar aprotic solvents." The reaction has been performed with R , R = hydrogen or alkyl, though best yields are obtained when r = r = H. In certain cases, unsymmetrical 1,4-diketones have been prepared by using a mixture of two silyi enol ethers. Other reagents that have been used to achieve either symmetrical or cross-coupled products are iodosobenzene-Bp3-Et20," ceric ammonium nitrate," and lead tetraacetate." If R =0R (in which case the substrate is a ketene silyi acetal), dimerization with TiCU leads to a dialkyl succinate (34, r =0R)." ... 

Sulfur trioxide reacts with MesSiCl 14 to give the trimethylsilyl ester of chloro-sulfonic acid 1334 [96], which on treatment vvdth iodosobenzene forms iodosoben-zenedichloride 1335, HMDSO 7, and regenerated SO3 [97]. Addition of olefins such as cyclohexene leads to the formation of sulfones such as 1336 [97]. With... 

Triphenylphosphine oxide (and PhsAsO or Ph2SeO) are reduced by MesSiNs 19, via the labile diazidophosphines 1780, to triphenylphosphine (triphenylarsine or diphenylselenide), nitrogen, and HMDSO 7, whereas iodosobenzene gives, via 1781, iodobenzene, nitrogen, and HMDSO 7 [30] (Scheme 12.9). 

Hydroxy(tosyloxy)iodobenzene 2014 reacts with phenyltrimethylsilane 81 in boiling acetonitrile to give diphenyliodonium tosylate 2015 and trimethylsilanol 4 or HMDSO 7 [184, 185]. Likewise, treatment of 2,5-bis(trimethylsilyl)furan 2016 with 2014 in boiling acetonitrile/methanol affords 78% iodonium tosylate 2017 and trimethylsilanol 4 [185]. In the presence of Bp3-OEt2 iodosobenzene oxidizes allyl-trimethylsilanes such as 2018 to unsaturated aldehydes such as 2019 in 63% yield, with formation of iodobenzene and trimethylsilanol 4 [186]. Analogously, vinyltrimethylsilanes such as (Z)-l-trimethylsilyl-2-phenylethylene 2020 afford, via 2021, acetylenes such as phenylacetylene in 61% yield and iodobenzene and trimethylsilanol 4 [187] (Scheme 12.54). 

The iodosobenzene HBF4 complex 2022 adds to the enol silyl ether 653 of acetophenone to give the labile iodonium salt 2023, which reacts with cyclohexene or tetramethylethylene to give the adducts 2024 and 2025 [188] (Scheme 12.55). 

Iodosobenzene reacts with TMSOTf 20 (or with TMSONf 21) to give the adducts 2026 or 2027, which are transformed by TMSCN 18 to the adduct 2028 [189]. 2028 is also obtained from iodobenzene by treatment with pertrifluoroacetic acid then reaction with TMSOTf 20 and Me3SiCN 18 [190] (Scheme 12.56). The... 

Reaction of N,N-dimethylaniline with 1-cyanobenziodoxol 1783 to afford N-methyl-N-cyanomethylaniline 1784 in 97% yield has been discussed in Section 12.1 [31]. Analogously, oxidation of dimethylaniline with iodosobenzene and trimethylsilyl azide 19 at 0°C in CDCI3 gives the azido compound 2040 in 95% yield, iodobenzene, and HMDSO 7 [194, 195] (Scheme 12.56). Likewise, the nucleophilic catalyst 4-dimethylaminopyridine (DMAP) is oxidized, in 95% yield, to the azide 2041, which is too sensitive toward hydrolysis to 4-N-methylaminopyri-dine to enable isolation [194, 195]. Amides such as 2042, in combination with tri-... 

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