A new method for introducing iodo and bromo fluorides into organic molecules using elemental fluorine

Abstract

A new method for introducing IF and BrF into organic compounds is developed. These reagents have been prepared by the direct action of elemental fluorine on the two respective halogens at low temperatures. The reactions of these interhalogen compounds with isolated double bonds are fast even at -75 °C. They were found to be stereospecific (anti mode addition) and in most cases regiospecific too. With conjugated enones the reactions were considerably slower. In this case an easy HF elimination takes place, producing eventually -halo enones. Since the benzylic C-I bond is very weak, the reaction of IF with stilbenes leads to the 1,2-difluoro adducts through a secondary attack of the nucleophilic fluorine on the iodine, either through SN2 or through the rare SNi mechanism. Bromine fluoride on the other hand gave the expected BrF adducts. The BrF reactions are much more forceful than the parallel IF ones, and a proton donor has to be present in order to tame this reagent. The halogen fluoride

Selective Trifluorination of Alkyl Aryl Sulfides Using IF5.

“…6 Addition of in situ-generated IF to the vinylic sulfide gives 1-arylthio-1-fluoro-2-iodopropane (6a). 3 Then elimination of an iodide, migration of the arylthio group, and fluorination at the terminal carbon take place successively to give 1,1-difluoro-2-arylthiopropane 3a. Finally, the oxidative fluorination of 3a takes place at the α-carbon of the sulfur to give 4a.…”

A mild method for halofluorination of alkenes with ionic liquid EMIMF(HF)2.3

“…The polypropylene tube used was a centrifuge tube (15 ml) with a screw cap, and was purchased from Corning. NMR spectra were recorded on a Varian Gemini 300 or Mercury 2000 in CDCl 3 . EMIMF(HF) 2.3 was prepared followed by the literature [10].…”

“…To prepare it, alkenes are treated with halonium ion and fluoride ion. However, fluoride ion source in these procedures, elemental fluorine [3,4], hydrogen fluoride [5,6], HF-pyridine (Olah's reagent) [7,8] and Et 3 N-3HF [9] contain difficulty to handle in some extent. In this situation, ionic liquid containing fluoride ion may have a possibility to solve these difficulty.…”

Halogenation of Tröger’s base analogues

“…[25][26][27][28] As part of a preliminary study aimed at alternate ways of accessing functionalised Tröger's base analogues, a methodology to brominate and chlorinate four Tröger's base compounds, as racemic mixtures, (Figure 1) was investigated. Numerous methods to halogenate aromatic compounds exist, [29][30][31][32][33][34] however, in terms of ease of handling and health issues, N-halosuccinimides are excellent reagents, especially if benzylic halogenation is suppressed.…”