Thionyl fluoride formation

The fluorosulfonyl group as an excellent leaving group can be substituted by fluorine in aromatic and fluoroaliphaticcompounds. " Metal fluorides serve as the fluoride source. The fluoro-sulfinate anion cleaved oif decomposes into sulfur dioxide and fluoride. Therefore, at least in theory, only catalytic amounts of added fluoride are required. In practice there is a loss of fluorine by formation of thionyl fluoride, which has to be compensated for. 

Although the procedure described utilizes metal vessels for ease of treating the cesium fluoride and to avoid the formation of large amounts of silicon tetrafluoride, glass may be used. This procedure has been used for preparation of up to 0.015 mole of CF2(0F)2 at a time with the aid of liquid nitrogen to condense excess fluorine into the vessel. The method is analogous to that used in the preparation of pentafluorosulfur hypofluorite by the static, catalytic fluorination of thionyl fluoride in the presence of cesium fluoride. ... 

A study of the reaction of fluorine with SO2 has shown that at temperatures up to 500 °C the reaction rapidly gives sulphuryl fluoride. If the quantity of fluorine is large enough, then SFe is formed, but only slowly, and via the formation of thionyl fluoride, thionyl tetrafluoride, and pentafluorosulphur hypo-fluorite. The fluorination of SO2 by Xep2, in the presence of compounds of the type MX (M = NMe4, Cs, or K X = F or Cl), has been studied. A variety of products were observed (Table 2) and reaction mechanisms were proposed in which the Xep2 functions as a weak Lewis acid. 

Potassium nitrite by-product can react with nitroaromatic substrate to suppress yields of aryl fluorides Modest yields (40-60%) of fluorophthafic anhydride are obtained from 3- or 4-nitiophthalic anhydride and potassium fluonde due to formation of by-product dipotassium salt of 3- or 4-nitrophtlialic acid [1/3,114, 115] (equation 33) Higher yields (93%) of 3-fluorophfhalic anhydride can be realized by regenera tion of 3-nitrophthalic anhydride from the dipotassium salt with thionyl chloride, followed by addition of fresh potassium fluoride [7/5] (equation 33)... 

The diols (97) from asymmetric dil droxylation are easily converted to cyclic sii e esters (98) and thence to cyclic sulfate esters (99).This two-step process, reaction of the diol (97) with thionyl chloride followed by ruthenium tetroxide catalyzed oxidation, can be done in one pot if desired and transforms the relatively unreactive diol into an epoxide mimic, ue. the 1,2-cyclic sulfate (99), which is an excellent electrophile. A survey of reactions shows that cyclic sulfates can be opened by hydride, azide, fluoride, thiocyanide, carboxylate and nitrate ions. Benzylmagnesium chloride and thie anion of dimethyl malonate can also be used to open the cyclic sulfates. Opening by a nucleophile leads to formation of an intermediate 3-sidfate aiuon (100) which is easily hydrolyzed to a -hydroxy compound (101). Conditions for cat ytic acid hydrolysis have been developed that allow for selective removal of the sulfate ester in the presence of other acid sensitive groups such as acetals, ketals and silyl ethers. 

The synthesis of alkylidene and allylidene cyclopropanes reported in this section takes advantage of the availability 77 78,81 a-82) of l-(l-silyl) cyclopropyl carbinols from a-lithio cyclopropylsilanes and carbonyl compounds. It, however, suffers from the sometimes modest yields obtained when ketones are involved (Schemes 21 a, 47) in the Peterson olefination reaction 77,78,81a) (Schemes 21, 48). This reaction seems much more difficult to achieve than when straight-chain analogs are involved and resembles the cases of allenes 1211 and chlorocyclopropenes120) reported by Chan. For example, thionyl chloride alone is not suitable for that purpose 77,136) but further addition of tetra-n-butylammonium fluoride (20 °C, 15 hrs) leads to the formation of undecylidene cyclopropane77,136 in 46% yield from the corresponding l-(l-silyl)cyclopropyl... 

Reaction of the j8-hydroxysilanes with thionyl chloride in triethylamine followed by treatment with fluoride, or with potassium hydride or tert-butoxide, leads to elimination of both the hydroxy and silyl groups and to the formation of alkylidenecyclopropanes (see Section 52.2.1.2). 

Nitrosyl fluoride also catalyses the addition of chlorine monofluoride (and of fluorine) across G=0 bonds in fluorocarbonyl compounds, the reaction apparently proceeding via initial formation of a-fluoro-nitrites. Apparently, no reaction occurs between carbon dioxide and chlorine monofiuoride in the presence of caesium fluoride in the temperature range -78 to 80 G [c/. CO3 + 2F °S GF COF), (100%)], but thionyl... 

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