1.1- difluoro-2-phenylethane

Fluorodediazoniation of 2-fluoro-2-phenylethylamines with sodium nitrite m Olah s reagent (70% anhydrous hydrogen fluoride-30% pyridine) gives high yields of 1,1-difluoro-2-phenylethanes arising from 1,2 migration of phenyl fJ] (equation 2)... 

Another common situation that can lead to second order spectra is an open chain system such as meso-l,2-difluoro-l,2-phenylethane whose magnetically nonequivalent spin system and resultant second order fluorine NMR spectrum (Fig. 2.7) can only be understood by examination of the contributing conformations about its fluorine bearing carbons.10... 

Reaction of AT-fluorobis(trifluoromethylsulfonyl)amine (Id) with alkenes gives various products, depending on the reaction conditions and the structure of the substrate. In solvents of higher nucleophilicity such as water, acetic acid, aqueous hydrochloric acid, and 70 % hydrogen fluoride/pyridine, a-fluorohydrins or their acetates, a-chloro-fl-fluoroalkanes or a,/ -difluoroal-kanes, e.g. 14. are obtained.146 Reaction of styrene and ( >l-phenylpropene with Id in dich-loromethane/acetic acid gives l-acetoxy-2-fluoro-l-phenylethane and -propane, in 92 and 99 % yield, respectively, the latter product in a ratio (erythrojthreo) 1 l.146... 

The elimination of hydrogen fluoride from vicinal fluorohalo compounds proceeds by a carb-anionic E1 cB mechanism, in which the acidity of the hydrogen plays a decisive role. The acidity of hydrogen is enhanced by the number of fluorine atoms in the /(-position,27-29 or by chlorine or bromine atoms in the a-position.30-39 For example, the rate of dehydrofluorination from 2-chloro-l,l,l-trifluoro-2-phenylethane (31) to give l-chloro-2,2-difluoro-l-phenylethene (32) is 85 times as high as the rate from l,l.l-trifluoro-2-phenylethane (33) to l,l-difluoro-2-phenyl-cthene (34).40... 

O Hagan D, Rzepa HS, Schbler M, Slawin AMZ (2006) The vicinal difluoro motif the synthesis and conformation of erythro- and tltreo-diastereomers of 1,2-difluorodi-phenylethanes, 2,3-difluorosuccinic acids and their derivatives. Beilstein J Oig Chem. doi 10.1186/1860-5397-2-19... 

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