Sodium iodide, halogen exchange

Bromo-3-methyl-4-nitroisothiazole can be converted into the 5-iodo analogue by reaction with sodium iodide in acetone (65AHC(4)107). Halogen exchange also takes place when 4-bromo-3-methylisothiazole-5-diazonium chloride is treated with methyl methacrylate and hydrolyzed, giving the chloro compound (150) (72AHC(14)l). 

Astatobenzene has also been prepared by heterogeneous halogen-exchange reaction between At adsorbed on solid sodium iodide, and bromobenzene at its boiling point 84). A further development in this technique has been to allow the reaction of bromobenzene in sealed ampuls at 250°C with At adsorbed on sodiiun hydroxide this resulted in high yields of about 70% 141,142). 

The chlorine atom in a-chloroalkylbenzotriazoles (560) undergoes exchange with other halogen atoms (Scheme 108). Thus, treatment of (560) with KF in the presence of 18-crown-6 gives the fluoro derivatives (561) <93PJC1243>. Sodium bromide or sodium iodide reacts with (560) to form (559, X = Br, I), whilst treatment of (560) with silver nitrate produces benzotriazol-l-ylmethyl... 

The most widely used example of halogen exchange is provided by the preparation of alkyl iodides from chlorides or bromides using sodium iodide in a... 

AUcoxycarbonylsulfenyl chlorides react at 20 ° with aqueous potassium iodide primarily with halogen exchange. The sulfenyl iodides, R8I, are unstable and combine in a bimolecular reaction to give the disulfane and elemental iodine (equation 19), which is removed by washing the organic phase with sodium thiosulfate (equation 20). " " ... 

Sulfides can be a-halogenated. 5-Chloro-2-methylthiopyrimidine was monochlorinated in the methyl group (462) using sulfuryl chloride, and the chlorine in the side-chain exchanged with iodine (463) by heating with sodium iodide in acetone <82CSI1>. 

Preparative Methods although more than 20 methods have been reported for the preparation of TMS-I, only a few are summarized here. Chlorotrimethylsilane undergoes halogen exchange with either Lithium lodid in CHCI3 or Sodium Iodide in MeCN, which allows in situ reagent formation (eq 1). Alternatively, HexamethyldisUane reacts with Iodine at 25-61 °C to afford TMS-I with no byproducts (eq 2). ... 

High-Purity Alkali Metal Halides. Alkali metal halides are refined by reaction in the gas phase with alkyl-, aryl-, or alkoxy-halosilanes. This brings about an exchange between the Si-bound halogen and the anion of the contaminant, while the C-containing radical has a reducing effect. Diiododimethylsilane is used to purify Sodium Iodide in this manner. 

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