W.R. Dolbier Jr. et al. / Journal of Fluorine Chemistry 128 (2007) 1091–1093
1093
solid–liquid exchange followed by increasing degrees of
liquid–liquid exchange.
mixture into 300 mL of 10% aqueous NaOH. The residual
organic phase was then washed three times with 100 mL of 5%
aqueous NaOH, and then three times with 300 mL of water.
Neither the ortho- nor the meta-isomer of bis-(trichlor-
omethyl)benzene has been examined under these conditions of
chlorine/fluorine exchange, so it is not known whether they will
exhibit similar selectivity with respect to formation of the
respective bis-(chlorodifluoromethyl)benzene compounds.
Subsequently, the organic phase was dried over MgSO , which
4
was followed by simple distillation at reduced pressure to give
three fractions:
ꢀ
Fraction #1: (71–90 8C at ꢁ35 mmHg) yielded 27.5 g of
material comprised of approximately 68 mol% 1 (19 g) with
the remaining material (8.5 g) being largely chloropenta-
3
. Conclusion
1
9
In conclusion, a highly selective process for partial exchange
of the benzylic chlorines of p-bis-(trichloromethyl)benzene to
allow the high yield formation of AF4 precursor, p-bis-
fluoro product, as determined by F NMR.
ꢀ Fraction #2: (90–95 8C at ꢁ35 mmHg) yielded 174 g of
product comprised of 97% pure 1.
(
chlorodifluoromethyl)benzene, is reported.
ꢀ Fraction #3: (95–107 8C at ꢁ35 mmHg) yielded 37 g of
material comprised of approximately 69 mol% (25 g) 1, with
the remaining material (12 g) being mainly comprised of
4
. Experimental
1
9
trichloro trifluoro product, as determined by F NMR.
4
.1. General
The total yield of p-bis-(chlorodifluoromethyl)benzene, 1,
from the three fractions amounted to about 218 g (79%).
NMR spectra were run using CDCl as solvent, unless
3
1
19
otherwise indicated. Proton, carbon and fluorine spectra were
measured at 300, 75.46 and 282 MHz, respectively, using TMS
1: bp 59–60 8C/11 mmHg [13]; H NMR, d 7.73 (s);
NMR, d À50.4 (s); C NMR, d 125.3 (t, J = 4.9), 125.7 (t,
CF
F
1
3
3
1
as internal standard for H and C spectra and CFCl for
13
19
1
2
F
J
= 308), 139.2 (t, J = 26.9).
CF CF
3
spectra. Coupling constants are reported in Hertz.
Acknowledgement
4
.2. p-Bis-(difluoromethyl)benzene, 2
Support of this research in part by Alpha Metals, Inc. is
gratefully acknowledged.
CsF (about 300 g) and p-bis-(dichloromethyl)benzene, 3 [4],
about 100 g) were added to a 500 mL three-necked flask. This
(
mixture resulted in a molar ratio of CsF:3 of about 4.8:1. The CsF
and 3 were thoroughly mixed and heated to about 180 8C. At this
temperature 3 melted and a slurry of 3 and CsF was formed. This
slurry was maintained at about 180 8C and stirred for about 8 h.
The liquid phase was then distilled from the flask at aspirator
pressure (about 20 mmHg). Gas chromatographic analysis of the
distillate was performed using a 10 ft SE-30 column, and the
analysis indicated a clean conversion to product, with 58 g (80%)
of p-bis-(difluoromethyl)benzene, 2, being isolated.
References
[
[
[
[
1] W.R. Dolbier Jr., J.-X. Duan, A.J. Roche, Org. Lett. 2 (2000) 1867–
869.
2] S.A. Fuqua, R.M. Parkhurst, R.M. Silverstein, Tetrahedron 20 (1964)
625–1632.
1
1
3] S.W. Chow, L.A. Pilato, W.L. Wheelwright, J. Org. Chem. 35 (1970) 20–
22.
4] The required tetrachloride, 3, could be obtained with high selectivity via a
controlled photochemical chlorination of p-xylene [5].
5] W.R. Dolbier Jr., X.X. Rong, W.E. Stalzer, USP 6,284,933 (2001).
6] A.K. Barbour, L.J. Belf, M.W. Buxton, in: M. Stacey, J.C. Tatlow, A.J.
Sharpe (Eds.), Adv. Fluor. Chem., Butterworths, Washington, 1963, pp.
181–270.
[
[
1
2
2
: bp 83–84 8C/30 mmHg [2]; H NMR, d 6.63 (t, J = 56,
FH
19 2 13
2H), 7.56 (s, 4H); F NMR, d À112.1 (d, J = 56.5);
NMR, d 114.2 (t, J = 238), 126.0 (t, J = 5.8), 136.8 (t,
JCF = 22.4).
C
FH
1
3
CF
CF
2
[
[
[
7] E.T. McBee, H.B. Hass, P.E. Weimer, g.M. Rothrock, W.E. Burt, R.M.
Robb, A.R. Van Dyken, Ind. Eng. Chem. 39 (1947) 298–301.
8] R.L. Murray, W.S. Beanblossom, B.H. Wojcik, Ind. Eng. Chem. 39 (1947)
4
.3. p-Bis-(chlorodifluoromethyl)benzene, 1
3
02–305.
9] W.R. Dolbier Jr., J.X. Duan, A.J. Roche, USP 6,150,499 (2000).
has been selectively converted to PhCF Cl by appropriate treat-
ment with either Et N-3HF [11] or Na (CH SiF ) [12]. It is not known
p-Bis-(trichloromethyl)benzene, 4, (350 g, 1.1 mol) was
placed into a 600 mL autoclave. To this was added 100 mL of
,2-dichloroethane and 200 g (10 mol) anhydrous HF. The
[10] PhCCl
3
2
3
2
3
5
whether these conditions would also produce 1 from 2.
11] L. Saint-Jalmes, J. Fluorine Chem. 127 (2006) 85–90.
12] R. Mueller, C. Dothe, H.J. Frey, Chem. Ber. 99 (1966) 1614–1617.
13] W.R. Dolbier Jr., M.A. Asghar, H.Q. Pan, L. Celewicz, J. Org. Chem. 58
(1993) 1827–1830.
1
[
[
[
mixture was stirred at 45 8C for about 10 h, during which time
the pressure rose to approximately 3 atm. Upon completion of
the reaction, residual HF and HCl were removed by venting the