Difluorodiidomethane from Difluoro(fluorosulfonyl)acetyl Fluoride
1321
CF2BrCl 10, treatm en t of 1 with ph en oxides in DMF at room tem perature
gave ArOCF2I on ly in 7–15% yields, th e diph en yl carbon ates bein g th e m a-
jor products, wh ile with ben zen eth iolates afforded difluorom eth ylen e de-
rivatives (ArSCF2I, ArSCF2SAr an d ArSCF2H) also in low yields11.
In prin ciple, 1 can be prepared by th e addition of difluorocarben e to io-
din e. However, previous m eth ods from various difluorocarben e precursors
suffered from low yields (ca 20%)12. Th e fluorin ation of CI4 with HgF2 gives
1, but th e yields are un satisfactory (27%)1. It was foun d th at usin g m eth yl
brom odifluoroacetate or potassium brom odifluoroacetate as difluorocarben e
source, 1 can be obtain ed in 50–60% yield with KI/I2 in th e presen ce of a
catalytic am oun t of CuI in DMF 13. A h igh er yield (85%) of 1 was also
reported on h eatin g 1,2-epoxyh exafluoropropan e with I2 in autoclave at
185 °C 14
.
In order to in vestigate furth er th e reaction s of 1, it seem s n ecessary to
h ave a sim pler way to syn th esize 1, because th e startin g m aterials of th e
above m en tion ed approach es are n ot readily available or a special equip-
m en t is n eeded. Fortun ately, a syn th etic m eth od for 1 from difluoro-
(fluorosulfon yl)acetyl fluoride(FSO2CF2COF, 2) was foun d to serve th e
purpose. Usin g 2, 1 can be prepared on 100 g scale in a ordin ary glassware.
We presen t h erein th e results.
EXPERIMENTAL
Difluoro(fluorosulfon yl)acetyl fluoride was obtain ed from En gin eerin g Research Cen ter in
Organ ic Syn th esis, Ch in ese Academ y of Scien ces. Aceton itrile (CH3CN) was dried over ph os-
ph orus pen toxide an d fresh ly distilled prior to use. Potassium iodide (KI) was dried over a
direct flam e. Silica gel (SiO2, 300–400 m esh ) was baked in an oven at 120 °C for 6 h . 19F NMR
spectra (δ, ppm ) were recorded on a Bruker AM-300 (282 MHz) spectrom eter usin g CFCl3 as
extern al stan dard, upfield sh ifts bein g design ated as n egative. Mass spectra were taken on a
Hewlett–Packard HP-5989A spectrom eter.
Difluorodiiodom eth an e (1)
A solution of dry KI (0.8 m ol, 132.8 g) an d I2 (0.8 m ol, 203.2 g) in CH3CN (600 m l) was
placed in a 1 000 m l th ree-n ecked flask fitted with a droppin g fun n el, a water con den ser
con n ected to a dry ice con den ser, a th erm om eter an d a m agn etic stirrer. To th e solution dry
silica gel (0.06 m ol, 3.6 g) was added durin g stirrin g. After h eatin g th e con ten t to 60–65 °C,
com poun d 2 (1.1 m ol, 198 g) was slowly added un der vigorous stirrin g durin g 8 h for fin ish -
in g th e reaction . Th en th e m ixture was kept for addition al tim e un til th e 19F NMR spectros-
copy sh owed th e en d of th e reaction (ca 2 h ). Sim ple distillation gave a solution of 1 in
CH3CN wh ich th en was poured in to H2O (2 l). Th e oil was separated, wash ed with H2O (5 ×
50 m l) an d dried over an h ydrous Na2SO4. About 171 g (0.56 m ol, 70%) of crude product 1
was obtain ed. Redistillation gave 148 g (0.49 m ol, 61%); b.p. 101 °C. MS, m/z: 304 (8.6, M+),
Collect. Czech. Chem. Commun. (Vol. 67) (2002)