Iodosobenzene dichloride

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%). 

Preparation. The reagent is prepared by stirring iodosobenzene diacetate with iN sodium hydroxide, collecting and drying the solid, and macerating it with chloroform to remove a little iodobenzene. This procedure is preferable to an older one involving alkaline hydrolysis of iodosobenzene dichloride because iodoso-... 

Dihydropyrans. Ozonolysis of 3,4-dihydropyran gives the expected 4-formyl-oxybutyraldehyde (240) which is then easily converted into 2-methoxy- or 2-ethoxy-tetrahydrofuran. 3,4-Dihydropyran reacts with iodosobenzene dichloride to give traw-2,3-dichlorotetrahydropyran (241). ... 

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... 

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... 

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... 

Iodosobenzene explodes violently at about 220 °C, so that determinations of the melting point should not be attempted. It may, however, be converted into iodobenzene diacetate in the following manner. Dissolve 2g 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 2g, m.p. 157°C. It may be recrystallised from benzene, and will keep indefinitely (unlike the iodobenzene dichloride). 

In a 1-1. three-necked flask, protected from the light and equipped with a mechanical stirrer, an inlet tube for the introduction of chlorine (Note 1), and an exit tube carrying a calcium chloride drying tube, are placed 150 cc. of dry chloroform (Note 2) and 102 g. (0.5 mole) of iodobenzene (Org. Syn. 19, 55). The flask is cooled in an ice-salt mixture, and dry chlorine (Note 3) is introduced, as rapidly as the solution will absorb it, until an excess is present (usually about three hours is required). The yellow, crystalline iodobenzene dichloride is filtered with suction, washed sparingly with chloroform, and dried in the air on filter paper. The yield is 120-134 g. (87-94 per cent of the theoretical amount) (Notes 4 and 5). The product is quite pure and may be used directly for the preparation of iodosobenzene and iodoxy-benzene. Since iodobenzene dichloride decomposes slowly on standing, it should not be stored indefinitely. 

Whereas internal acetylenes are oxidized to a-diketones, terminal acetylenes give carboxylic acids with one less carbon on treatment with thallium trinitrate [413], potassium permanganate [843], iodosobenzene with tris(triphenylphosphine)ruthenium dichloride as a catalyst [787], or a rather rare oxidant, pentafluoroiodobenzene bis(trifluoroacetate) [797] (equation 144). 

Alkyl acetylenyl ethers treated with iodosobenzene in dichloromethane in the presence of 1% of tris(triphenylphosphine)ruthenium dichloride for 15 min at room temperature furnish keto esters in 59-70% yields (equation 335) [786]. 

The unusual oxidant nickel peroxide converts aromatic aldehydes into carboxylic acids at 30-60 °C after 1.5-3 h in 58-100% yields [934. The oxidation of aldehydes to acids by pure ruthenium tetroxide results in very low yields [940. On the contrary, potassium ruthenate, prepared in situ from ruthenium trichloride and potassium persulfate in water and used in catalytic amounts, leads to a 99% yield of m-nitrobenzoic acid at room temperature after 2 h. Another oxidant, iodosobenzene in the presence of tris(triphenylphosphine)ruthenium dichloride, converts benzaldehyde into benzoic acid in 96% yield at room temperature [785]. The same reaction with a 91% yield is accomplished by treatment of benzaldehyde with osmium tetroxide as a catalyst and cumene hydroperoxide as a reoxidant [1163]. 

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