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J. Kvõcala et al. / Journal of Fluorine Chemistry 113 ;2002) 211±218
216
stoppered and stirred for 3 days. Removal of solvents invacuo
afforded crystalline 2,3-dibromo-2-fluoroprop-2-enoic acid
afforded on short path distillation EZ)-1,2-di¯uoro-1-
iodoethene E1b, 1.079 g, 56.8%, bp 43±48 8C, [28] 49±
50 8C, Z/E 94:6). 1H NMR ECDCl3 [28]) d: 7.50 Ed,
1
E6, 0.79 g, 95%, mp 68±71 8C, [33] 71±72.5 8C). H NMR
2
3
2
ECDCl3 [34]) d: 4.08 Edd, 1H, JHH 11:5 Hz, JHF
1H, JHF 76:4 Hz). 13C NMR ECDCl3 [28]) d: 104.1
3
2
1
2
1
7:7 Hz); 4.24 Edd, 1H, JHF 29:1 Hz, JHH 11:5 Hz);
9.65 Ebs, 1H).
Edd, JCF 316 Hz, JCF 57 Hz); 146.2 Edd, JCF
248 Hz, JCF 56 Hz). 19F NMR ETHF-d8 [28]) d:
2
3
À133.8 Ed, 1F, JFF 145 Hz); À159.8 Edd. 1F,
2
4.2.1.3. 1-Bromo-1-fluoroethene ;1a). A 50 ml round
bottom flask was charged with dried acetophenone
E15 ml), 2,3-dibromo-2-fluoroprop-2-enoic acid E6, 0.79 g,
3.2 mmol), followed by NaHCO3 E0.6 g, 7 mmol) in small
portions while stirring. The mixture was heated slowly to
150 8C for 3 h and outgoing 1-bromo-1-fluoroethene E1a,
50 mg, 13%) was trapped in the cooled EÀ80 8C) receiver.
1H NMR E2-methyltetrahydrofuran/THF-d8 1:1) d: 4.91 Edd,
3JFF 145 Hz, JHF 76 Hz).
4.2.4. ;E)-Dimethylphenyl;1,2-difluoroethenyl)silane ;1f)
A 2 ml quartz cell was charged with EZ)-E1,2-di¯uoroethe-
nyl)dimethylphenylsilane E1e, 1.98 g, 10.0 mmol) and
diphenyl disul®de E66 mg, 0.30 mmol) and irradiated by a
medium pressure UV lamp at room temperature for 2 days.
EE)-DimethylphenylE1,2-di¯uoroethenyl)silane E1f) was
obtained in good yield by distillation E1.82 g, 91.5%, bp
85±91 8C/2.7 kPa [23] not given, Z/E 5:95). 1H NMR
1H, 3JHF 42:3 Hz, 2JHH 4:4 Hz); 5.34 Edd, 1H, 3JHF
9:9 Hz, JHH 4:4 Hz). 19F NMR E2-methyltetrahydro-
2
3
2
furan/THF-d8 1:1) d: À61.8 Edd, 1F, JHF 42 Hz,
ECDCl3) d: 0.48 Es, 6H); 6.21 Edd, 1H, JHF 74:7 Hz,
3JHF 10 Hz).
3JHF 22:0 Hz); 7.42 Em, 3H); 7.59 Em, 2H). 13C NMR
ECDCl3) d: À4.6 Es); 128.0 Es); 130.1 Es); 133.9 Es); 133.9 Es);
4.2.2. Preparation of ;Z)-;1,2-difluoroethenyl)-
dimethylphenylsilane ;1e)
143.7 Edd, 1JCF 277 Hz, 2JCF 9 Hz); 152.3 Edd, 1JCF
277 Hz, JCF 5 Hz). 19F NMR ETHF-d8) d: À134.5 Edd,
2
2
3
1F, JHF 75 Hz, JFF 21 Hz); À158.1 Edd, 1F,
3JFF 3JHF 22 Hz).
4.2.2.1. Dimethylphenyl;1,2,2-trifluoroethenyl)silane ;3).
From chlorotrifluoroethene E17.5 g, 150 mmol), chloro-
dimethylphenylsilane E17.1 g, 100 mmol) and butyllithium
E48 ml, 2.5 M in hexanes, 120 mmol), dimethylphenyl-
E1,2,2-trifluoroethenyl)silane E3, 17.51 g, 76.8%, bp 81±
86 8C/2.4 kPa, [28] 82±83 8C/2.3 kPa) was prepared
accordingto [35]. 1H NMR ECDCl3) d: 0.76 Ed, 6H,
4JHF 1:1 Hz); 7.64 Em, 3H); 7.83 Em, 2H). 13C NMR
ECDCl3) d: À4.4 Es); 128.2 Es); 130.1 Es); 131.4 Eddd,
4.2.5. ;E)-1,2-Difluoro-1-iodoethene ;1c)
A 20 ml round bottom ¯ask charged with EE)-E1,2-di¯uor-
oethenyl)dimethylphenylsilane E1f, 1.53 g, 7.72 mmol), dry
DMSO E8 ml), dried potassium ¯uoride E1.34 g, 23 mmol)
and iodine E3.95 g, 15.6 mmol) was attached to the source
of vacuum E2.5 kPa) and heated while stirred at 70 8C for
1.5 h. Crude product E1.18 g) collected in a cooled trap
EÀ80 8C) afforded on short path distillation EE)-1,2-
di¯uoro-1-iodoethene E1c, 963 mg, 65.7%, bp 48±51 8C,
2
2
1JCF 256 Hz, JCF 83 Hz, JCF 65 Hz); 133.8 Es);
134.2 Es); 161.6 Eddd, 1JCF 317, 1JCF 277, 2JCF 40).
1
2
Z/E 5:95). H NMR ECDCl3) d: 6.32 Edd, 1H, JHF
73:6, 3JHF 25:4 Hz). 13C NMR ECDCl3) d: 97.9 Edd, 1JCF
331 Hz, 2JCF 19 Hz); d: 138.5 Edd, 1JCF 273 Hz, 2JCF
4.2.2.2. ;Z)-;1,2-Difluoroethenyl)dimethylphenylsilane
;1e). From dimethylphenylE1,2,2-trifluoroethenyl)silane E3,
12.17 g, 56.3 mmol) and lithium aluminum hydride E2.67 g,
70.3 mmol), EZ)-E1,2-difluoroethenyl)dimethylphenylsilane
E1e, 9.95 g, 89.2%, bp 87±94 8C/2.7 kPa [28] not given,
Z/E 94:6) was prepared accordingto [23]. 1H NMR
ECDCl3) d: 0.54 Es, 6H); 7.42 Em, 3H); 7.61 Em, 2H);
9 Hz). 19F NMR ETHF-d8) d: À109.2 Em, 1F); À135.5 Ed, 1F,
2JHF 75 Hz).
4.2.6. ;Z)-1-Bromo-1-fluoro-2-phenylethene ;1g)
Preparation of EZ)-1-bromo-1-¯uoro-2-phenylethene E1g)
was accomplished accordingto [30]. From ethyl Ediethox-
yphosphoryl)¯uoroacetate E4, 5.33 g, 22.0 mmol), benzal-
dehyde E2.12 g, 20.0 mmol) and butyllithium E2.25 ml,
9.85 M in hexanes, 22.0 mmol), ethyl EE)-2-¯uoro-3-phe-
nylprop-2-enoate E3.38 g, 87.1%, bp 90±104 8C/100 Pa,
[36] 73±77 8C/100 Pa, Z/E 5:95) was prepared, which
E3.38 g, 17.4 mmol) afforded by hydrolysis with sodium
hydroxide E2.78 g, 69.6 mmol) crude EE)-2-¯uoro-3-phenyl-
prop-2-enoic acid E7, 2.79 g, 96.5%, Z/E 5:95) as color-
less oil. Bromination E2.95 g, 18.5 mmol) of EE)-2-¯uoro-3-
phenylprop-2-enoic acid E7, 2.79 g, 16.8 mmol) yielded
2,3-dibromo-2-¯uoro-3-phenylpropanoic acid E9, 5.28 g,
96.5%), which E5.28 g, 16.2 mmol) was reacted with
NaHCO3 E2.72 g, 32.4 mmol) in acetone E50 ml) to afford
2
3
7.64 Edd, 1H, JHF 79:1 Hz, JHF 11:0 Hz). 13C NMR
ECDCl3) d: À4.2 Es); 128.1 Es); 129.8 Es); 133.8 Es); 133.9 Es);
1
2
154.1 Edd, JCF 244 Hz, JCF 56 Hz); 160.5 Edd,
1JCF 259 Hz, JCF 55 Hz). 19F NMR ETHF-d8 [28])
2
3
2
d: À171.0 Edd, 1F, JFF 130 Hz, JHF 79 Hz); À179.9
3
3
Edd, 1F, JFF 130 Hz, JHF 11 Hz).
4.2.3. ;Z)-1,2-Difluoro-1-iodoethene ;1b)
A 25 ml round bottom ¯ask charged with EZ)-E1,2-di¯uor-
oethenyl)dimethylphenylsilane E1e, 1.99 g, 10.0 mmol), dry
DMSO E10 ml), dried potassium ¯uoride E1.74 g, 30 mmol)
and iodine E5.08 g, 20.0 mmol) was attached to the source of
vacuum E2.5 kPa) and heated while stirred at 70 8C for 1.5 h.
Crude product E1.40 g) collected in a cooled trap EÀ80 8C)