Fluonne addition

In addition, fluonne [97, 98], trifluoromethyl hypofluorite [99, 100], bisftri-fluoromethyOperoxide [100, 101], trifluoromethyl disulfide [100]. and xenon difluoride [102, lOi, 104] react with phosphines to give the corresponding diflu-orophosphoranes in yields ranging from 25% to near quantitative. Phosphites are fluorinated by carbonyl fluoride [95, 96] or 2-hydroperfIuoropropyl azide [f05J (equation 15). 

Many reagents enable the addition fluonne and another element or group across multiple bonds... 

Tnfluoromethyl hypofluonte will fluorinate Schiff bases, giving N,a,a-tn-fluoroatmnes and a-fluoroimines [144] and reacts with diazoketones to give adducts in modest yields [145] (equation 6) At-Substituted aziridines give nng opened products by 1,3 addition of fluonne on nitrogen and trifluoromethoxy on carbon [146] (equation 7)... 

The combination of a hydrogen fluoride addition and a chlorine-fluonne displacement converts 1,1 2,2-tetrachloroethylene-l,2 di(isocyanidedichloride)to perfluoro-A, A -dimethylethylenediamine [37] (equation 28)... 

In the [2+4] pencyclic cycloaddition reaction known as the Diels-Alder reaction, fluonne-containing compounds have been widely used as dienes, dieno-philes, or both Much of the fundamental work, including many comprehensive and systematic studies, was done before 1972, and Hudlicky provides an exeellent summary of this work [9] Additional sources for early work in this area are reviews in Organic Reactions [61] and Fluorine Chemistry Reviews [62]... 

P-Fluonne or fluonne further removed from the cation center always inductively destabilizes carbocabons [115, 116] No simple p-fluoroalkyl cations have been observed in either the gas phase or solution, and unhke the cases of the other halogens, there is no evidence for formation of alkyl fltioronium ions (5) in solution [117, 118], although (CH3)2F is long-hved m the gas phase [119] The only P-fluonnated cations observed in solution are those that benefit from additional conjugativc stabilization, such as a-trifluoromethylbenzyl cations [112] and per-fluonnated allyl [120], cydopropenium [112], and tropylium [121] ions... 

The course of each of the free radical reactions shown in equations 19-21, where fluorine substitution alters the normal trans stereochemistry of addition, is ascnbed to endo fluonne stenc effects... 

Burton [92J published extensive NMR information forjluorinatedquaternary phosphanium salts that are used as Wittig reagents Clear data-structure correlations allow NMR mformauon on other compounds to be predicted The trifluo-romethyl analogue is a recent addition to this senes [93] The fluonne NMR of... 

The most widely used fluoroelastomers are copolymers of VDF and HFP and optionally also TFE. HFP interrupts the crystallimty of otherwise crystaUme PVDF TFE increases the fluonne content for mcreased solvent and heat resistance without raising the glass transition temperature as much as would an equivalent amount of additional HFP The dipolymer is random except that there are no contiguous HFP units and can therefore be represented as follows... 

Fluorination of naphthalene in a stream of dilute fluorine over cobalt trifluoride yields a mixture of perfluorodecalins and partially fluonnated naphthalene derivatives that are fully fluonnated to perfluorodecalins by a subsequent treatment with dilute fluonne [23] Perfluorodecalins are also final products ot fluorination of tetralin over cobalt trifluoride at 250 °C. A more thorough investigation of this reaction revealed seven additional compounds as products and intermediates [//] (equation 6). 

A fluorinated enol ether formed by the reaction of sodium ethoxide with chlorotrifluoroethylene is much less reactive than the starting fluoroolefin To replace the second fluonne atom, it is necessary to reflux the reaction mixture. The nucleophilic substitution proceeds by the addition-elimination mechanism [30] (equation 26). 

The effect of monofluorination on alkene or aromatic reactivity toward electrophiles is more difficult to predict Although a-fluonne stabilizes a carbocation relative to hydrogen, its opposing inductive effect makes olefins and aromatics more electron deficient. Fluorine therefore is activating only for electrophilic reactions with very late transition states where its resonance stabilization is maximized The faster rate of addition of trifluoroacetic acid and sulfuric acid to 2-fluoropropene vs propene is an example [775,116], but cases of such enhanced fluoroalkene reactivity in solution are quite rare [127] By contrast, there are many examples where the ortho-para-dueeting fluorine substituent is also activating in electrophilic aromatic substitutions [128]... 

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