Sodium dithionite initiated addition of CF2Br2, CF3I and (CF3)2CFI to allylaromatics. Synthesis and the reactivity of 4-aryl-1,1-difluorodienes and 4-aryl-1,1-bis(trifluoromethyl)dienes

Article abstract of DOI:10.1016/j.jfluchem.2007.04.028

Sodium dithionite initiated addition of CF₂Br₂, CF₃I and (CF₃)₂CFI to the terminal double bond of allylbenzenes and of (CF₃)₂CFI to allylpyridines in a MeCN/H₂O system

Full text of DOI:10.1016/j.jfluchem.2007.04.028

Journal of Fluorine Chemistry 128 (2007) 997–1006
www.elsevier.com/locate/fluor
Sodium dithionite initiated addition of CF2Br2, CF3I
and (CF3)2CFI to allylaromatics
Synthesis and the reactivity of 4-aryl-1,1-difluorodienes
and 4-aryl-1,1-bis(trifluoromethyl)dienes
*
Jolanta Ignatowska, Wojciech Dmowski
Institute of Organic Chemistry, Polish Academy of Sciences, 44 Kasprzaka St., 01-224 Warsaw, Poland
Received 2 February 2007; received in revised form 26 April 2007; accepted 28 April 2007
Available online 3 May 2007
Abstract
Sodium dithionite initiated addition of CF2Br2, CF3I and (CF3)2CFI to the terminal double bond of allylbenzenes and of (CF3)2CFI to
allylpyridines in a MeCN/H2O system were investigated. The reactions of CF2Br2 with allylbenzenes gave comparable amounts of adducts, 1-
(2,4-dibromo-4,4-difluorobutyl)benzenes, debrominated products,1-(4-bromo-4,4-difluorobutyl)benzenes, and dimeric compounds in total
yields 40–66%. Treatment of the adducts with DBU resulted in double dehydrohalogenation affording 4-aryl-1,1-difluorobutadienes which
undergo Diels–Alder condensation with nitrogen dienophiles to give N-heterocycles with difluoromethylene group in the ring. The reactions of
CF3I and (CF3)2CFI with allylbenzenes gave the respective adducts, (4,4,4-trifluoro-2-iodobutyl)benzenes and 1-(4,5,5,5-tetrafluoro-4-
(trifluoromethyl)-2-iodopentyl)benzenes as the main products. Dehydrohalogenation of these adducts resulted, respectively, in (4,4,4-
trifluoro-but-1-enyl)benzenes and 4-aryl-1,1-bis(trifluoromethyl)butadienes in high yields. (CF3)2CFI reacted rapidly with allylpyridines to
give mixtures from which, after treatment with DBU, 4-pyridyl-1,1-bis(trifluoromethyl)butadienes were isolated in a ca. 60% yield.
# 2007 Elsevier B.V. All rights reserved.
Keywords: Dibromodifluoromethane; Trifluoroiodomethane; 2-Iodoheptafluoropropane; Radical addition; Sodium dithionite; Allylaromatics; 1,1,-Difluorodienes;
1,1-Bis(trifluoromethyl)dienes
1. Introduction
CuCl and ethanolamine were used as initiators for the additions,
reactions with allylbenzenes were limited to only two examples
and yields were rather low. Nevertheless, the work by
Elsheimer has shown that 1,1-difluorodienes are very active
in the 4 + 2 cycloadditions what additionally prompted us to
look for a new method of their synthesis. Synthesis of dienes
terminated with two geminal CF3 groups, via additions of 2-
iodoheptafluoropropane to allylaromatics, and reactivity of
such dienes were also investigated.
In the preceding paper we reported the sodium dithionite
initiated additions of 1-bromo-1-chloro-2,2,2-trifluoroethane
(Halothane1) to a number of allylaromatics [1]. Dehydroha-
logenation of the resulting (2-bromo-4-chloro-5,5,5-trifluor-
opentyl)benzenes afforded high yields of conjugated dienes
terminated with the CF3 group at the one end and an aryl group
at the other. With the aim to extend this method to the synthesis
of dienes terminated with the CF2 group (1,1-difluorodienes)
we investigated sodium dithionite initiated additions of
dibromodifluoromethane and trifluoroiodomethane to allylben-
zenes and dehydrohalogenation of the adducts. Although such
reactions have been previously studied by Elsheimer et al. [2],
2. Results and discussion
2.1. Reactions involving CF2Br2
The reactions of dibromodifluoromethane with allylben-
zenes 1, because of the volatility of the former, were carried out
in a closed system (pressure glass ampoule). Water–acetonitrile
solution (1: 1 by volume) was used as the reaction medium in
* Corresponding author. Fax: +48 22 632 66 81.
E-mail address: dmowski@icho.edu.pl (W. Dmowski).
0022-1139/$ – see front matter # 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2007.04.028

998
J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
Scheme 1.
which sodium dithionite and trisodium phosphate (HBr
scavanger) were suspended (the salts are only partially soluble
in the reaction mixture). Using phosphate instead of the usually
used bicarbonate was necessary to avoid evolution of CO2 and,
therefore, increasing pressure. The reactions were carried out at
ambient temperature for 0.5–24 h (vigorous stirring was
applied). The crude mixtures of products (after extraction with
Et2O) consisted of comparable amounts of the expected adducts
2 [1-(2,4-dibromo-4,4-difluorobutyl)benzenes], reductively deb-
rominated compounds 3 and dimeric products 4 (Scheme 1) in
total yields reaching 40–66%. Numerous unidentified com-
pounds of higher molecular weight were also present.
and appearance of two AB systems in the 19F NMR spectra. The
structure of compound 4a was confirmed by the 13C NMR DEPT
135 spectrum which exhibited four signals of the CH2 groups and
two signals of the CH groups.
Treatment of mixtures of compounds 2, 3, and 4 with DBU
(1,8-diazabicyclo[5.4.0]undece-7-ene) at ambient temperature
resulted in double dehydrobromination of 2 to give mixtures of
dienes with terminal CF2 group, 1,1-difluoro-4-phenyl-1,3-
butadienes (5), and unchanged compounds 3 and 4. Easy
elimination of HBr, also from the CH2CF2Br group in 2, could
be explain in term of increased acidity of the CH2 group protons
in the intermediate alkene formed after elimination of the first
HBr molecule from the C-1–C-2 positions. Since 1,1-
difluorodienes were reported to be very unstable [2] their
isolation was not attempted. The presence of dienes 5 in these
mixtures was confirmed by addition of the most reactive
dienophile known, 4-phenyl-3H-1,2,4-triazoline-3,5-dione (6);
immediate reaction occurred to give cycloadducts 7. The
isolated yields of 7 did not exceed 9% with respect to starting
allylbenzenes 1, however, when the reaction sequence started
from pure 2a, it was converted to adduct 7a in a 44% yield
(Scheme 2).
Electron donating substituents increase, while electron
withdrawing substituents evidently decreases the reactivity of
allylbenzenes. Thus, the reaction with 3,4-dimethoxyallylben-
zene (1c) was completed within 30 min and gave 26% of 2c
(total yield 66%) but with 4-chloroallylbenzene (1d) only 11%
of 2d (total yield 40%) was achieved after 24 h. In both cases
the 2:3:4 ratio was only little affected.
Compounds 2, 3 and 4 were isolated by column chromato-
graphy and the spectral and analytical data fully confirmed their
structures. The characteristic feature of compounds 2 is
1
appearance of two AB systems in the H NMR spectra and,
Diene 5a, generated from adduct 2a, reacted also with
diethyl azodicarboxylate (8) to give reasonable yield of
cycloadduct 9 but in this case a catalyst (ZnCl2) and prolonged
reaction time were required (Scheme 3). The attempted
interestingly, a broad AB system in the 19F NMR spectra. The
dimeric structure of compounds 4 (two diastereoisomers) were
elucidated from the exact mass of molecular ions in the HRMS
Scheme 2.

J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
999
Scheme 3.
Scheme 4.
(pressure glass ampoule), under similar conditions. The
reactions proceeded cleanly to give adducts, (4,4,4-trifluoro-
2-iodobutyl)benzenes (10), as the main products with only
negligible amounts of reductively deiodinated compounds 11
(Scheme 4).
The identity of minor compound 11 was confirmed by
comparison of weak signals in the NMR spectra of mixtures of
products 10 + 11 with the spectra of pure compounds 11 which
were obtained by treatment of these mixtures with zinc metal in
ethanol. Unfortunately, adducts 10 on treatment with DBU
(1,8-diazabicyclo[5.4.0]undece-7-ene) eliminate only HI mole-
cule to give (4,4,4-trifluoro-but-1-enyl)benzenes 12 (Scheme
5). The attemped simultaneous elimination of HF to form 1,1-
difluorodienes 5 failed, even by treatment with very strong
bases like LDA or t-BuOK.
Scheme 5.
reactions of diene 5a with common dienophiles like maleic
anhydride, diethyl acetylenedicarboxylate, cis-1,2-bis(phenyl-
sulphonyl)ethylene and others, failed because decomposition of
the diene occurred faster than the cycloaddition reaction.
In conclusion, although dehydrobromination of adducts 2
gives acceptable yields of highly reactive 1,1-difluorodienes 5
(as determined by cycloaddition reactions), low yields of these
adducts in the sodium dithionite initiated reactions of
allylbenzenes with CF2Br2 makes this procedure of little
practical value.
2.3. Reactions involving (CF3)2CFI
These reactions were carried out in an open system under
standard conditions using NaHCO3 as the HI scavanger. The
reactions proceeded readily at ambient temperature to give
in most cases high yields of the expected adducts, 1-(4,5,5,5-
tetrafluoro-4-(trifluoromethyl)-2-iodopentyl)benzenes (13)
(Scheme 6). Deiodinated compounds 14 were formed in only
insignificant amounts. Similarly to compounds 11, the identity
of minor compounds 14 was confirmed by comparison of weak
signals in the NMR spectra of the crude reaction mixtures with
2.2. Reactions involving CF3I
The reactions of trifluoroiodomethane with allylbenzenes 1,
as those with CF2Br2, were carried out in a closed system
Scheme 6.

1000
J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
than like a diene and undergoes 4 + 2 cycloadditions with
dienes. However, the attemped reactions of compounds 15 and
19 with various nucleophilic reagents, including dienes, also
failed.
3. Experimental
Melting points were determined in capillaries and are
1
uncorrected. H NMR, 19F NMR and 13C NMR spectra were
recorded (at 400, 376 and 100 MHz, respectively) with a Varian
400 spectrometer in CDCl3 solutions (or as indicated
otherwise). Chemical shifts are quoted in ppm from internal
Scheme 7.
the H NMR and 19F NMR spectra of pure compound 14a,
which was obtained by treatment of a mixtures of 13 + 14 with
zinc metal in ethanol.
TMS for H and 13C and from internal CFCl3 for 19F nuclei.
1
1
Coupling constants (J) values are in Hz. GC–MS analyses were
performed with a Hewlett–Packard 5890 apparatus (30 m
capillary column, HP-5 oil). Mass spectra of pure compounds
were obtained with an AMD-604 spectrometer.
The best result was achieved in the reaction of (CF3)2CFI
with 4-methoxyallylbenzene 1e which gave a 90% yield of
isolated adduct 13e and, as expected, the bromo-substituted
adduct 13f was obtained in the lowest yield (42%).
Adducts 13 on treatment with DBU eliminate both HI and
HF to give high yields of conjugated dienes 15 terminated with
two CF3 groups (Scheme 7), which were easily isolated by
Dibromodifluoromethane, trifluoroiodomethane, hepta-
fluoro-2-iodopropane, allylbenzenes 1a, 1c, and 1e, and diethyl
azodicarboxylate were commercial reagents. Other allylben-
zenes and allylpyridines were prepared by allylation of the
appropriate magnesium aryl bromides with allylbromide [4–7].
4-Phenyl-3H-1,2,4-triazoline-3,5-dione was prepared accord-
ing to the literature procedure [8].
1
column chromatography. The H NMR spectra of dienes 15
revealed that they are formed exclusive as the trans-form
trans
(
J
= ca. 15 Hz). These dienes were found to be very
HH
stable and unreactive. Prolonged heating with common
dienophiles (maleic anhydride, diethyl acetylenedicarboxylate)
do not lead to any products; both substrates were recovered
unchanged. Even the reaction of 15a with 4-phenyl-3H-1,2,4-
triazoline-3,5-dione (7) conducted at 80 8C for 96 h resulted in
only 12% conversion to cycloadduct 16 (not isolated).
In contrast to sluggish reactions with CF3CHClBr reported
earlier [1], (CF3)2CFI reacts with 2- and 3-allylpyridines 17
rapidly at ambient temperature to give complex mixtures of
products. Initial cooling was necessary to control the rates of
these reactions and to achieve better yields of the supposed
adducts 18. These adducts were expected to be not stable and
therefore their isolation was not attempted. The crude reaction
mixtures were treated with DBU to give mixtures from which
1,1-bis(trifluoromethyl)dienes 19 were isolated in 58–60%
yield (Scheme 8).
3.1. Addition of CF2Br2 to allylbenzenes
3.1.1. Addition of CF2Br2 to allylbenzene (1a)
A pressure glass ampoule (150 ml) fitted with a Rotaflo1
valve and magnetic stirring bar was filled with a water–
acetonitrile solution (1:1, 60 ml), sodium dithionite (2.5 g,
12 mmol [85%]), Na3PO4Á12H2O (7.0 g, 18 mmol), allylben-
zene (1a) (1.5 g, 12 mmol) and dibromodifluoromethane (2.9 g,
14 mmol). The ampoule was closed and vigorously stirred at
ambient temperature (20–25 8C) for 3 h after which water was
added (20 ml), the reaction mixture was extracted with diethyl
ether (3 Â 50 ml) and the combined extract were dried over
MgSO4. The crude mixture of products obtained after
evaporation of the solvent (3.06 g, yellowish oil) was subjected
to column chromatography (silica gel, hexanes) to give
compounds 2a, 3a and 4a. Usually, 1:1 ratios of Na2S2O4 to
alkenes 1 were used but decreased Na2S2O4/1 ratio does not
diminish formation of compounds 3 and 4.
It has been reported [3] that unsubstituted 1,1-bis(trifluor-
omethyl)butadiene behaves like an electrophilic alkene rather
Scheme 8.

J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
1001
(2,4-Dibromo-4,4-difluorobutyl)benzene (2a): yield: 0.65 g
1
(16%). Colorless liquid. H NMR: 3.01 (complex AB system,
1-(2,4-Dibromo-4,4-difluorobutyl)-4-methylbenzene (2b):
1
yield: 0.54 g (21%). Colorless liquid. H NMR: 2.34 (s, 3H);
2
2JHH = 14.4, 2H); 3.17 (dd, 2JHH = 14.4; 3JHH = 8.0, 1H); 3.28
3.0 (complex AB system, 2H); 3.14 (dd, JHH = 14.5;
2
3
3
2
3
(dd, JHH = 14.4; JHH = 6.0, 1H); 4.41 (dq, JHH = 3JHH = ca.
3JHH = 8.0, 1H); 3.23 (dd, JHH = 14.5; JHH = 6.2, 1H); 4.39
(dq, 3JHH = 3JHH = ca. 7.8; 3JHH = 3JHH = ca. 6.3, 1H); 7.11 (d,
3JHH = 8.1, 2H); 7.15 (d, 3JHH = 8.1 Hz, 2H). 19F NMR: À42.3
7.9; 3JHH = 3JHH = ca. 6.2, 1H); 7.22 (d, 3JHH = 8.0, 2H); 7.29
(m, 1H); 7.35 (m, 2H). 19F NMR: À42.4 (ddd, JFF = 158.2,
2
3JFH = 14.2; JFH = 11.8, 1F); À43.5 (ddd, JFF = 158.2;
(dt, JFF = 158.0 Hz; JFH = ca. 13.2 Hz, 1F); À43.5 (dt,
3
2
2
3
3
3
3JFH = 14.5; JFH = 13.0, 1F). MS (EI): m/z (rel. int., ion):
2JFF = 158.0; JFH = 13.8, 1F). MS: m/z, (rel. int., ion): 344,
330, 328, 326 (10, 22, 12, M+); 297 [<1, (M À C6H5)+]; 249,
247 [4, 4, (M À Br)+]; 248, 246 [5, 1, (M À HBr)+]; 229, 227
[16,17, (C10H9BrF)+]; 215 (1); 195 (1); 185, 183 [10,10
(M À CH2CF2Br)+]; 167 [34, (C10H9F2)+]; 147 [64,
(C10H8F)+]; 127 (12); 117 (11); 115 (12); 104 [14, (C8H8)+];
91 [100, (C7H7)+]. Analysis: found: C, 37.0; H, 3.3; F, 11.7; Br,
48.4%. Calculated for C10H10F2Br2 (327.99): C, 36.6; H, 3.1; F,
11.6; Br, 48.7%. HRMS: found: 325.91119. Calculated for
C10H10F279Br2: 325.91173.
342, 340 (6, 13, 6, M+); 263, 261 [1, 1, (M À Br)+]; 264, 262 [3,
3 (M À HBr)+]; 241 [1, (C11H11FBr)+]; 199, 197 [1, 1,
(M À CH2CF2Br)+]; 182 [14, (M À 2Br)+]; 167 (6); 161 (6);
146 (4); 131 (3); 117 (4); 105 [100, (C8H9)+]; 91 [5, (C7H7)+].
HRMS: found: 339.92835. Calculated for C11H12F279Br2:
339.92738.
1-(4-Bromo-4,4-difluorobutyl)-4-methylbenzene (3b):
yield: 0.31 g (16%). Colorless liquid. 1H NMR: 1.94 (m,
2H); 2.32 (s, 3H); 2.36 (m, 2H); 2.65 (t, 3JHH = 7.5, 2H); 7.07
(d, 3JHH = 7.9, 2H); 7.11 (d, 3JHH = 7.9, 2H). 19F NMR: À43.8
(4-Bromo-4,4-difluorobutyl)benzene (3a): yield: 0.52 g
1
(17%). Colorless liquid. H NMR: 1.91–2.01 (m, 2H); 2.69
3
(t, JFH = 13.9, 2F). MS: m/z (rel. int., ion): 264, 262 (12, 14,
(t, 3JHH = 7.5, 2H); 2.29–2.41 (m, 3JHF = 13.7, 2H); 7.15–7.20
(m, 2H); 7.20–7.24 (m, 1H); 7.28–7.33 (m, 2H). 19F NMR:
À43.8 (t, 3JFH = 13.7, 2F). MS (EI): m/z (rel. int., ion): 250, 248
(56, 57, M+); 169 [20, (M À Br)+]; 149 [55, (C10H10F)+]; 127
(10); 105 [16, (C8H9)+]; 91 [100, (C7H7)+]. Analysis: found: C,
48.2; H, 4.2; F, 15.2; Br, 32.2%. Calculated for C10H11F2Br
(249.10): C, 48.2%; H, 4.4%, F, 15.2%; Br, 32.1%.
M+); 218 (5); 183 [3, (M À Br)+]; 163 [7, (C11H12F)+]; 146 (3);
117 (13); 105 [100, (C8H9)+]. HRMS: found: 262.01606.
Calculated for C11H13F279Br: 262.01687.
2,3-Bis(2-bromo-2,2-difluoroethyl)-1,4-bis(4-methylphe-
nyl)butane (4b): yield: 0.62 g (16%). Viscous resin. 1H NMR:
2.32 (s, 6H); 2.35–2.83 (m, 10H); 6.93 (d, 3JHH = 8.0, 2H); 7.01
3
3
(d, JHH = 8.0, 2H); 7.06 (d, JHH = 7.7, 2H); 7.11 (d,
2
2,3-Bis(2-bromo-2,2-difluoroethyl)-1,4-diphenylbutane
(4a): yield: 0.69 g (11%). Viscous resin. 1H NMR: 2.28 (m, 3H);
2.46 (m, 3H); 2.66 (complex AB system, 3H); 2.82 (dd,
2JHH = 14.1; 3JHH = 7.0, 1H); 7.02 (m, 2H); 7.12 (m, 2H); 7.23
3JHH = 7.7, 2H). 19F NMR: À40.2 (ddd, JFF = 157.4;
3JFH = 16.8; JFH = 10.7, 1F); À41.7 (m, 2F); À42.1 (dt,
3
2JFF = 157.4; 3JFH = 15.4, 1F). MS: m/z (rel. int., ion): 526, 524,
522 (2, 4, 2, M+); 393, 391 [1, 2, (C21H22F2Br)+]; 311 [1,
(C21H21F2)+]; 301 (2); 287 (<1); 261 (2); 241 (1); 231 (1); 197
(1); 181 (3); 161 (4); 141 (2); 131 (4); 105 [100, (C8H9)+].
Analysis: found: C, 50.7; H, 4.2; Br, 30.2; F, 14.4%. Calculated
for C22H24F4Br2 (524.24): C, 50.4; H, 4.6; Br, 30.5; F, 14.5%.
HRMS: found: 522.01728. Calculated for C22H24F479Br2:
522.01809.
2
(m, 4H); 7.31 (m, 2H). 19F NMR: À40.6 (ddd, JFF = 157.6;
3
2
3JFH = ca. 16.5; JFH = ca. 11.9, 1F); À42.0 (dt, JFF = 157.6;
3JFH = ca. 15.0, 1F); À41.3 (dt, JFF = 157.2; 3JFH = 14.0, 1F);
2
À41.8 (dt, JFF = 157.2; JFH = 14.0, 1F). 13C NMR: 36.1 (s,
2
3
CH2); 36.18 (s, CH2); 36.96 (s, CH); 37.0 (s, CH); 44.18 (t,
3JCF = 20.7 Hz, CH2); 44.2 (t, JCF = 20.7 Hz, CH2); 122.7
3
1
(2 Â t, JCF = 306.5 Hz, CF2Br); 126.5 (s, CHarom.); 126.7 (s,
CHarom.); 128.5 (s, CHarom.); 128.7 (s, CHarom.); 128.9 (s,
CHarom.); 129.03 (s, CHarom.); 138.5 (s, Carom.); 138.6 (s, Carom.).
13C NMR DEPT 135: À36.1 (s, CH2); À36.2 (s, CH2); 36.9 (s,
3.1.3. Addition of CF2Br2 to 3,4-dimethoxyallylbenzene
(1c)
3,4-Dimethoxyallylbenzene (1c) (0.6 g, 3.3 mmol), CF2Br2
(0.83 g, 4 mmol), Na2S2O4 (0.7 g, 3.3 mmol), and
Na3PO4Á12H2O (1.9 g, 5 mmol) were reacted at ambient
temperature for 0.5 h and worked up as in Section 3.1.1.
Compounds 2c and 3c were isolated and identified as a mixture;
yield: 0.58 g, 2c:3c = 1.3:1. Colorless liquid.
3
CH); 37.0 (s, CH); À44.2 (t, JCF = 20.7 Hz, CH2); À44.2 (t,
3JCF = 20.7 Hz, CH2); 126.5 (s, CHarom.); 126.7 (s, CHarom.);
128.5 (s, CHarom.); 128.7 (s, CHarom.); 128.9 (s, CHarom.); 129.0
(s, CHarom.). MS (EI): m/z (rel. int., ion): 498, 496, 494 (8, 16, 8,
M+); 418 (<1); 377, 375 [1, 1, (C20H18F2Br)+]; 289, 287 [1, 1,
(C13H14F2Br)+]; 275, 273[1, 1, (C12H12F2Br)+];259 (1); 249 (3);
229 (1); 181 [4, (C11H11F2)+]; 159 [2, (C12H15)+]; 147 (8); 117
(8); 105 (3); 91 [100, (C7H7)+]. Analysis: found: C, 48.3; H, 4.2;
Br, 32.4;F, 15.1%. CalculatedforC20H20F4Br2 (496.17):C, 48.4;
H, 4.1; Br, 32.2; F, 15.3%. HRMS: found: 493.98763. Calculated
for C20H20F479Br2: 493.98679.
1-(2,4-Dibromo-4,4-difluorobutyl)-3,4-dimethoxybenzene
1
(2c): yield: 26%. H NMR: 2.98 (dd, JFH = 12.9; JHH = 6.3,
3
3
3
1H); 3.01 (dd, JFH = 13.9; JHH = 6.7, 1H); 3.14 (dd, JHH
3
2
=
14.5; JHH = 7.6, 1H); 3.21 (dd, JHH = 14.5; JHH = 6.5, 1H);
3
2
3
3
3.88 (s, 3H); 3.89 (s, 3H); 4.39 (dq, JHH = 3JHH = ca. 7.5;
3JHH = 3JHH = ca. 6.7; 1H); 6.67–6.90 (m, overlapping signals of
aromatic protons of 2c and 3c). 19F NMR: À42.3 (dt,
3
2
3
3.1.2. Addition of CF2Br2 to 4-methylallylbenzene (1b)
4-Methylallylbenzene (1b) (1.0 g, 7.5 mmol), CF2Br2 (1.9 g,
9 mmol), Na2S2O4 (1.6 g, 7.5 mmol), and Na3PO4Á12H2O
(4.2 g, 11 mmol) were reacted at ambient temperature for 2 h
and worked up as in Section 3.1.1.
2JFF = 157.9; JFH = 12.9, 1F); À43.6 (dt, JFF = 157.9; JFH
= 13.9, 1F). GC–MS: m/z (rel. int., ion): 390, 388, 386 (4, 7, 4,
M+); 209, 207 [3, 3, (M À Br)+]; 227 [3, (C12H13O2F2)+]; 207 [3,
(C12H12O2F)+]; 151 [100, (C9H11O2)+]. HRMS: found:
385.93375. Calculated for C12H14O2F279Br2: 385.93286.

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J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
1-(4-Bromo-4,4-difluorobutyl)-3,4-dimethoxybenzene (3c):
10.8, 1F); À41.3 (dt, 2JFF = 157.3; 3JFH = 15.3, 1F); À41.7 (dt,
1
3
2
yield: 26%. H NMR: 1.94 (m, 2H); 2.36 (m, 2H); 2.65 (t,
3JHH = 7.6, 2H); 3.86 (s, 3H); 3.88 (s, 3H). 19F NMR: À43.8 (t,
3JFH = 13.9, 2F). GC–MS: m/z (rel. int., ion): 310, 308 (20, 25,
M+); 229 [7, (M À Br)+]; 209 [3, (C12H14O2F)+]; 151 [100,
(C9H11O2)+]. HRMS: found: 308.02113. Calculated for
C12H15O2F279Br: 308.02235.
2JFF = 157.3; JFH = 14.8, 1F); À42.0 (dt, JFF = 157.3;
3JFH = 14.8, 1F). MS: m/z (rel. int., ion): 566, 564, 562 (6,
7, 3, M+); 323, 321 [<1, <1, (C13H13F2BrCl)+]; 203, 201 [1, 2,
(C10H8F2Cl)+]; 181 (1); 151 (3); 127, 125 [33, 100, (C7H6Cl)+].
Analysis: found: C, 42.9; H, 3.2; F, 13.0%. Calculated for
C20H18F4Br2Cl2: (565.07): C, 42.5; H, 3.2; F, 13.4%. HRMS:
found: 561.90795; Calculated for C20H18F479Br235Cl2:
561.90884.
2,3-Bis(2-bromo-2,2-difluoroethyl)-1,4-bis(3,4-dimethoxy-
phenyl)butane (4c): yield: 0.3 g (15%). Viscous resin. 1H NMR:
2.16–2.50 (m, 6H); 2.5–2.8 (complex AB system, 2JHH = 14.2;
3JHH = 7.0, 4H); 3.76 (s, 3H); 3.80 (s, 3H); 3.85 (s, 3H); 3.86 (s,
3H); 6.52 (dd, 3JHH = 9.2; 3JHH = 1.9, 1H); 6.56 (dd, 3JHH = 8.0,
3JHH = 1.9, 1H); 6.70 (m, 3H); 6.79 (m, 1H). 19F NMR: 40.4
(m); À40.8 (m); À41.4 (m); À41.5 (m); À41.9 (m); À42.0 (dt,
3.2. Dehydrohalogenation of adducts 2 and in situ’
reactions of intermediate dienes 5 with dienophiles
3.2.1. Dehydrohalogeniation of mixtures of 2, 3, and 4
followed by reactions with 4-phenyl-3H-1,2,4-triazoline-
3,5-dione (6)
3
2JFF = 155.95; JFH = 16.3). MS: m/z (rel. int., ion): 618, 616,
614 (7, 14, 7, M+); 566 (2); 486 [2, (C23H27F2BrO4)+]; 349, 347
[1, 1, (C15H18F2BrO2)+]; 335, 333 [2, 2, (C14H16F2BrO2)+]; 307
(1); 290 (1); 207 (1); 189 (<1); 177 (10); 151 [100,
(C9H11O2)+]. Analysis: found: C, 46.7; H, 5.1; Br, 25.2; F,
11.9%. Calculated for C24H28F4Br2O4 (616.28): C, 46.7; H,
4.9; Br, 25.6; F, 12.3%. HRMS: found: 614.03015. Calculated
for C24H28F479Br2O4: 614.02904.
Allylbenzene 1a, 1b or 1c (10 mmol), CF2Br2 (2.7 g,
13 mmol), Na2S2O4 (2.1 g, 10 mmol), and Na3PO4Á12H2O
(3.7 g, 9.7 mmol) were reacted at ambient temperature for 3 h
and worked up as in Section 3.1.1. The crude mixture of
compounds 2, 3 and 4, obtained after evaporation of the
solvents, was re-dissolved in diethyl ether and stirred with
added DBU (4.56 g, 30 mmol) at ambient temperature for
20 min, then an excess of the base was removed by washing
with hydrochloric acid (5%, 2 Â 30 ml) followed by brine
(10 ml) The organic phase was dried over MgSO4 and
evaporated to ca. 3–5 ml capacity. This residue, containing
dienes 5 and unchanged 3 and 4, was dissolved in CH2Cl2
(30 ml) and, while stirring, 4-phenyl-3H-1,2,4-triazoline-3,5-
dione (6) (0.81 g, 46 mmol) was added portion-wise (after each
addition initial purple colour of 6 quickly disappeared). The
stirring was continued for 40 min, the solvents were removed
on a rotary evaporator and the residue was crystallized from
hexane–ethyl acetate (3:2) to give cycloadducts 7a, 7b and 7c
as white solids.
3.1.4. Addition of CF2Br2 to 4-chloroallylbenzene (1d)
4-Chloroallylbenzene (1d) (1.0 g, 6.5 mmol), CF2Br2
(2.15 g, 10.4 mmol), Na2S2O4 (1.4 g, 6.5 mmol), and
Na3PO4Á12H2O (3.7 g, 9.7 mmol) were reacted at ambient
temperature for 24 h and worked up as in Section 3.1.1.
1-(2,4-Dibromo-4,4-difluorobutyl)-4-chlorobenzene (2d):
yield: 0.27 g, (11%). Colorless liquid. 1H NMR: d: 3.01
2
3
(complex AB system, 2H); 3.10 (dd JHH = 14.6; JHH = 8.5,
2
1H); 3.28 (dd, JHH = 14.6; JHH = 5.4, 1H); 4.36 (dq,
3
3
3JHH = 3JHH = ca. 8.5; JHH = 3JHH = ca. 6.0, 1H); 7.17 (d,
3
3JHH = 8.6, 2H); 7.32 (d, JHH = 8.6, 2H). 19F NMR: À42.7
2
3
3
(ddd, JFF = 158.8; JFH = 14.5; JFH = 12.2, 1F); À43.4 (ddd,
3
3
2JFF = 158.8; JFH = 14.8; JFH = 12.1, 1F). MS: m/z (rel. int.,
ion): 364, 362, 360 (5, 7, 3, M+); 263, 261 [1, 1,
(C10H8ClBrF)+]; 219, 217 [2, 1, (M À CH2CF2Br)+]; 201 [4,
(C10H8F2Cl)+]; 181 [6, (C10H7FCl)+]; 161 (1); 146 (7); 127,
125 [32, 100, (C7H6Cl)+]. Analysis: found: C, 33.5; H, 2.6; F,
10.9%. Calculated for C10H9F2Br2Cl (362.44): C, 33.1; H, 2.5;
F, 10.5%.
5,5-Difluoro-2,8-diphenyl-5,8-dihydro-[1,2,4]triazolo[1,2-
a]pirydazine-1,3-dione (7a): yield: 0.3 g (9%). Mp 183–184 8C
(lit. 184–187 8C [2]). 1H NMR: 5.95 (t, 3JHH = JHF = 4.8, 1H);
6.43 (ddm, 3JHH = 10.2, 3JHF = 6.2, 1H); 6.80 (dd, 3JHH = 10.2,
3JHH = 4.8, 1H); 7.40–7.45 (m, 5H); 7.46–7.52 (m, 5H). 19F
2
3
4
NMR: À73.5 (ddd, JFF = 220.7, JFH = 4.8 Hz, JFH = 0.96,
2
3
4
1F); À82.5 (ddd, JFF = 220.7, JFH = 6.2, JFH = 1.44, 1F).
MS: m/z (rel. int., ion): 341 (46, M+); 264 [5, (M À Ph)+]; 166
[100, (C10H8F2)+]; 146 [46, (C10H7F)+]; 115 [17, (C9H7)+].
Analysis: found: C, 62.9; H, 4.0; F,10.8; N, 11.9%. Calculated
for C18H13F2O2N3 (341.31): C, 63.3; H, 3.8; F, 11.1; N, 12.3%.
Analogical reaction sequence starting from isolated 2a
(5.5 mmol) gave cycloadduct 7a in a 44% yield.
1-(4-Bromo-4,4-difluorobutyl)-4-chlorobenzene (3d): yield:
1
0.31 g (17%). Colorless liquid. H NMR: 1.91 (m, 2H); 2.34
(m, 2H); 2.67 (t, 3JHH = 7.6, 2H); 7.11 (d, 3JHH = 8.6, 2H); 7.27
(d, 3JHH = 8.6, 2H). 19F NMR: À43.9 (t, 3JFH = 13.8, 2F). MS:
m/z (rel. int., ion): 284, 282 (16, 14, M+); 249 (1); 222 (1); 203
[7, (M À Br)+]; 183 [16, (C10H9FCl)+]; 161 (3); 151 (5); 146
(8); 127, 125 [32, 100, (C7H6Cl)+]. Analysis: found: C, 42.6; H,
3.5; F, 13.6%. Calculated for C10H10F2BrCl (283.54): C, 42.4;
H, 3.5; F, 13.4%.
5,5-Difluoro-2-phenyl-8-p-tolyl-5,8-dihydro-[1,2,4]tria-
zolo[1,2-a]pirydazine-1,3-dione (7b): yield: 0.48 g (9%). Mp
1
159–160 8C. H NMR (in C2D6CO): 2.35 (s, 3H); 5.70 (t,
2,3-Bis(2-bromo-2,2-difluoroethyl)-1,4-bis(4-chlorophe-
1
nyl)butane (4d): yield: 0.42g (11%). Viscous resin. H NMR:
3JHH = JHF = 4.7, 1H); 6.21 (ddm, 3JHH = 10.3, 3JHF = 6.0, 1H);
3
6.47 (dd, JHH = 10.3, JHH = 4.8, 1H); 7.20 (d, JHH = 8.0,
3
3
3
2.27 (m, 4H); 2.48 (m, 4H); 2.69 (complex AB system,
2JHH = 14.1; 3JHH = 7.0, 2H); 6.90 (d, 3JHH = 8.4, 2H); 7.04 (d,
2H); 7.33 (d, JHH = 8.0, 2H); 7.35–7.46 (m, 5H). 19F NMR:
2
3
2
À77.6 (dd, JFF = 220.1, JFH = 4.7, 1F); À87.6 (ddd, JFF
=
3
3
3JHH = 8.4, 2H); 7.20 (d, JHH = 8.4, 2H); 7.30 (d, JHH = 8.4,
220.1, 3JFH = 6.0, 4JFH = 1.0, 1F).). MS: m/z (rel. int., ion): 355
(60, M+); 335 [5, (M À HF)+]; 264 [4, (M À NPh)+]; 236 [1,
2H). 19F NMR: À40.4 (ddd, JFF = 157.3; JFH = 16.2; JFH
=
2
3
3

J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
1003
(C12H10ON2F2)+]; 180 [100, (C11H10F2)+]; 165 [29,
(C10H7F2)+]. Analysis: found: C, 64.0; H, 4.2; F, 10.3; N,
11.4%. Calculated for C19H15F2O2N3 (355.34): C, 64.2; H, 4.2;
F, 10.7; N, 11.8%. HRMS: found: 355.11258. Calculated for
C19H15F2O2N3: 355.11323.
stirred for 6 h, then water was added (20 ml), the reaction
mixture was extracted with diethyl ether (3 Â 50 ml) and the
combined extract were dried over MgSO4. The crude product
obtained after evaporation of the solvent was subjected to
column chromatography (hexanes) to give (4,4,4-trifluoro-2-
iodobutyl)benzene (10a) as colorless liquid. Yield: 1.51 g
8-(3,4-Dimethoxyphenyl)-5,5-difluoro-2-phenyl-5,8-dihy-
dro-[1,2,4]triazolo[1,2-a]pir-ydazine-1,3-dione (7c): yield:
0.21 g (9%). Mp 132 8C (lit. 130–134 [2]). 1H NMR (in
C2D6CO): 3.78 (s, 3H); 3.80 (s, 3H); 5.87 (t, 3JHH = JHF = 4.8,
2
3
(57%). 1H NMR: 2.81 (dqd, JHH = 15.7; JHF = 10.0;
2
3
3JHH = 6.5, 1H); 2.87 (dqd, JHH = 15.7; JHF = 10.0;
3JHH = 7.0, 1H); 2.20 (dd, JHH = 14.5; JHH = 8.3, 1H); 3.25
2
3
1H); 6.40 (ddm, 3JHH = 10.2, 3JHF = 6.2, 1H); 6.77 (dd, 3JHH
=
(dd, JHH = 14.5; JHH = 6.5, 1H); 4.33 (dq, JHH = 8.2;
3JHH = 6.7, 1H); 7.19 (m, 2H); 7.32 (m, 3H). 19F NMR:
À64.1 (t, 3JHF = 10.0, 3F). MS: m/z (rel. int., ion): 314 (4, M+);
255 [12, (C10H9I)+]; 235 (1); 215 (3); 195 (3); 187 [100,
(M À I)+]; 159 (15); 147 [43, (C10H9F2)+]; 117 [23, (C9H10)+];
103 (11); 91 [49, (C7H7)+]. Analysis: found: C, 38.6; H, 3.4; F,
18.5; I, 40.8%. Calculated for C10H11F3I (314.09): C, 38.2; H,
3.2; F, 18.1; I, 40.4%.
2
3
3
10.2, 3JHH = 4.8, 1H); 6.98 (m, 2H); 7.05 (s, 1H); 7.39–7.56 (m,
2
3
4
5H). 19F NMR: À73.2 (ddd, JFF = 220.8, JFH = 4.9, JFH
=
1.05, 1F); À82.4 (ddd, 2JFF = 220.8; 3JFH = 6.3 Hz, 4JFH = 1.05,
1F). MS: m/z (rel. int., ion): 401 (100, M+); 370 [2,
(M À OCH3)+]; 309 (6); 264 (9); 226 [66, (C12H12O2F2)+];
195 [15, (C11H9OF2)+]; 151 [10, (C9H11O2)+]. Analysis: found:
C, 59.4; H, 4.7; F, 9.1; N, 10.4%. Calculated for C20H17F2O4N3
(401.34): C, 59.8; H, 4.3; F, 9.5; N, 10.5%. HRMS: found:
401.11991. Calculated for C20H17F2O4N3: 401.11871.
3.3.2. Addition of CF3I to 3,4-dimethoxyallylbenzene (1c)
3,4-Dimethoxyallylbenzene (1c) (1.5 g, 8.4 mmol), sodium
dithionite (1.8 g, 8.5 mmol [85%]), Na3PO4Á12H2O (6.5 g,
17 mmol) and CF3I (2.5 g, 13 mmol) were reacted and worked
up as above. The crude product obtained after evaporation of the
solvent was subjected to column chromatography (hexanes/
ethanol 4:1) to give 1-(4,4,4-trifluoro-2-iodobutyl)-3,4-
dimethoxybenzene (10c) as yellowish liquid. Yield: 2.45 g
3.2.2. Dehydrohalogenation of pure 2a followed by the
reaction with diethyl azodicarboxylate (8)
Compound 2a (0.3 g, 0.92 mmol) was dissolved in CH2Cl2
(10 ml) and treated with DBU (0.42 g, 2.7 mmol) at room
temperature for 20 min. After work up as described in Section
3.2.1, the resultant oil was dissolved in dry CH2Cl2, diethyl
azodicarboxylate (0.32 g, 1.6 mmol), and ZnCl2 (20 mg) were
added and the reaction mixture was stirred at ambient
temperature for 3 days under the argon atmosphere. An orange
colored oil obtained after removal of the solvent was purified by
column chromatography (silica gel, hexanes/AcOEt 1:1) to
give 9 as a colorless oil. Yield 0.1 g (32%).
1
3
(78%). H NMR: 2.83 (complex m, JHF = 10.3, 2H); 3.17 (d,
3JHH = 7.3, 2H); 3.88 (s, 3H); 3.89 (s, 3H); 4.31 (qn, 3JHH = ca.
4
7.0, 1H); 6.70 (d, JHH = 2.0, 1H); 6.74 (dd, JHH = 8.1;
3
3
4JHH = 2.0, 1H); 6.83 (d, JHH = 8.1, 1H). 19F NMR: À64.1 (t,
3JHF = 10.3, 3F). MS: m/z (rel. int., ion): 374 (67, M+); 355 [<1,
(M À F)+];315[5, (C12H12IO2)+];285[1, (C11H10IO)+];247[91,
(M À I)+]; 219 (10); 207 (7); 164 [12, (C10H12O2)+]; 151 [100,
(C9H11O2)+]. Analysis: found: C, 38.9; H, 3.7; F, 15.2; I, 33.6%.
Calculated for C12H14F3IO2 (374.14): C, 38.5; H, 3.8; F, 15.2; I,
33.9%.
Diethyl 3,3-difluoro-6-phenyl-3,6-dihydro-pirydazine-1,2-
1
dicarboxylate (9): H NMR: 1.06 (m, 3H); 1.28 (m, 3H); 4.05
3
(m, 2H); 4.27 (m, 2H); 5.99 (m, 1H); 6.08 (dd, JHH = 9.0,
3JHF = 6.8, 1H); 6.60 (dd, 3JHH = 9.0, 3JHH = 4.9, 1H); 7.35 (m,
5H). 19F NMR: À72.1 (m, 1F); À72.7 (m, 1F). MS: m/z (rel. int.,
ion): 340 (3, M+); 320 [<1, (M À HF)+]; 296 [3, (M À CO2)+];
269, 268 [12, 81, (M À HCO2Et)+]; 253 [6, (M À NCO2Et)+];
248 [5, (C12H6F2N2O2)+]; 223 [8, (C12H13F2N2)+]; 195 [28,
(M À 2CO2Et)+]; 180 [19, (C10H8F2N)+]; 175 [81, (C12H12F)+];
166 [100, (C10H8F2)+]; 146 [40, (C10H7F)+]; 127 [12, (C10H7)+];
115 (20); 99 (38); 91 (9). HRMS: found: 340.12284. Calculated
for C16H18O4N2F2: 340.12346.
3.3.3. Reductive deiodination of compounds 10a and 10c
(4,4,4-Trifluoro-2-iodobutyl)benzene (10a) (1.26 g, 4 mmol)
or 1-(4,4,4-trifluoro-2-iodobutyl)-3,4-dimethoxybenzene (10c)
(2.45 g, 6.5 mmol) and zinc powder (0.9 g 13 mmol) were
refluxed in ethanol (50 ml) for 10 h. After cooling to ambient
temperature, brine was added, organic oil was extracted with
diethyl ether (4 Â 40 ml) and the combined extracts were dried
over MgSO4. The crude products obtained after removal of the
solvent were purified by column chromatography (silica gel,
hexanes or hexanes–ethanol 19:1, respectively) to give
compounds 11a and 11c as colorless oils.
3.3. Addition of CF3I to allylbenzenes and reactions of the
adducts
3.3.1. Addition of CF3I to allylbenzene (1a)
(4,4,4-Trifluorobutyl)benzene (11a): yield 0.32 g (43%). 1H
A pressure glass ampoule (150 ml) fitted with a Rotaflo1
valve and magnetic stirring bar was filled with a water–
acetonitrile solution (1:1, 40 ml), sodium dithionite (1.8 g,
8.5 mmol [85%]), Na3PO4Á12H2O (6.5 g, 17 mmol) and
allylbenzene (1a) (1.0 g, 8.5 mmol). The ampoule was cooled
to À78 8C (dry ice/acetone), evacuated, then trifluoroiodo-
methane (2.5 g, 13 mmol) was condensed in it. After warming
up to ambient temperature the contents of the ampoule was
NMR: 1.91 (m, 2H); 2.08 (complex m, JHF = 10.9, 2H); 2.69
3
3
(t, JHH = 7.6, 2H); 7.21 (m, 3H); 7.31 (m, 2H). 19F NMR:
À66.7 (t, 3JHF = 10.9, 3F). MS: m/z (rel. int., ion): 188 (18, M+);
149 [2, (C10H10F)+]; 117 [3, (C9H9)+]; 115 (2); 105 [2,
(M À CF3CH2)+]; 91 [100, (C7H7)+]. Analysis: found: C, 63.4;
H, 5.7; F, 30.1%. Calculated for C10H11F3 (188.19): C, 63.8; H,
5.9; F, 30.3%. HRMS: found: 188.08211. Calculated for
C10H11F3: 188.08129.

1004
J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
2
3
2
1-(4,4,4-Trifluorobutyl)-3,4-dimethoxybenzene (11c):
1
yield: 1.18 g, (73%). H NMR: 1.87 (m, 2H); 2.08 (complex
3.11 (dd, JHH = 14.6; JHH = 9.1, 1H); 3.23 (dd, JHH = 14.6;
3JHH = 5.4, 1H); 4.42 (m, 1H); 7.06 (d, 3JHH = 8.2, 2H); 7.14 (d,
m, 3JHF = 10.8, 2H); 2.64 (t, 3JHH = 7.6, 2H); 3.86 (s, 3H); 3.88
3JHH = 8.2, 2H). 19F NMR: À76.7 (qn, JFF = 9.0, 3F); À77.7
4
(dq, 4JFF = 9.0, 3JFF = 2.1, 3F); À185.8 (complex m, 1F). MS:
m/z (rel. int., ion): 428 (7, M+); 409 [1, (M À F)+]; 301 [100,
(M À I)+]; 282 [1, (C13H12F6)+]; 261 (<1); 209 (1); 182 (5);
145 (2); 131 (13); 117 (16); 105 [56, (C8H9)+]; 91 [13,
(C7H7)+]. Analysis: found: C, 36.8; H, 2.8; F, 31.5; I, 29.3%.
Calculated for C13H12F7I (428.13): C, 36.5, H, 2.8; F, 31.1; I,
29.6%.
4
(s, 3H); 6.70 (d, JHH = 2.0, 1H); 6.72 (dd, JHH = 8.0;
3
3
4JHH = 2.0, 1H); 6.80 (d, JHH = 8.0, 1H). 19F NMR: À66.6
(t, 3JHF = 10.8, 3F). MS: m/z (rel. int., ion): 248 (43, M+); 233
[2, (M À CH3)+]; 219 (5); 209 [1, (C12H14FO2)+]; 165 [2,
(M À CF3CH2)+]; 151 [100, (C9H11O2)+]. Analysis: found: C,
57.7; H, 5.7; F, 23.2%. Calculated for C12H15F3O2 (248.24): C,
58.1; H, 6.1; F, 22.9%.
1-Methoxy-4-(4,5,5,5-tetrafluoro-2-iodo-4-trifluoromethyl-
pentyl)benzene (13e): yield: 4.0 g (90%). 1H NMR: 2.83–2.99
3.3.4. Dehydroiodination of compound 10a
2
(complex AB systems, JHH 16.3, 2H); 3.09 (dd, JHH = 14.7,
2
(4,4,4-Trifluoro-2-iodobutyl)benzene (10a) (1.18 g,
3.7 mmol) and DBU (1.7 g 11 mmol) were refluxed in hexanes
(50 ml) for 12 h. The base was removed by washing with
hydrochloric acid (5%) followed by brine. The organic phase
was dried over MgSO4, evaporated, and the residue was
subjected to column chromatography go give (4,4,4-trifluor-
obut-1-enyl)benzene (12) as colorless liquid. Yield: 0.36 g
2
3
3JHH = 8.9 Hz, 1H); 3.20 (dd, JHH = 14.7, JHH = 5.6, 1H);
3
3
4.40 (m, 1H); 6.86 (d, JHH = 8.8, 2H); 7.10 (d, JHH = 8.8, 2
H). 19F NMR: À76.8 (qn, 4JFF = 9.0, 3F); À77.7 (dq complex,
4JFF = 9.0, JFF = 2.1, 3F); À185.8 (complex m, 1F). MS: m/z
3
(rel. int., ion): 444 (24, M+); 425 [2, (M À F)+]; 317 [100,
(M À I)+]; 298 (3); 147 [17, (C10H11O)+]; 134 [18, (C9H10O)+];
121 [67, (C8H9O)+]. Analysis: found: C, 35.2; H, 2.6, F, 30.1%.
Calculated for C13H12F7OI (444.13): C, 35.2; H, 2.7, F, 29.9%.
1-Bromo-4-(4,5,5,5-tetrafluoro-2-iodo-4-trifluoromethyl-
3
3
(53%). 1H NMR: 2.99 (qdd, JHF = 10.7; JHH = 7.3;
3
3
4JHH = 1.4, 2H); 6.11 (dt, JHH = 15.8; JHH = 7.3, 1H); 6.60
(d, JHH = 15.8, 1H); 7.32 (m, 5H). 19F NMR: À66.7 (t,
3
1
3JHF = 10.7, 3F). MS: m/z (rel. int., ion): 186 (100, M+); 165
(14); 147 [8, (C10H8F)+]; 117 [69, (M À CF3)+]; 91 [16,
(C7H7)+]; 69 (9). Analysis: found: C, 64.9; H, 4.9; F, 30.3%.
Calculated for C10H9F3 (186.17): C, 64.5; H, 4.9; F, 30.6%.
pentyl)benzene (13f): yield: 0.73 g (42%). H NMR: 2.8–3.0
(complex AB systems, 2JHH = 16.3, 2H); 3.05 (dd, 2JHH = 14.7,
3JHH = 9.6, 1H); 3.26 (dd, JHH = 14.7, JHH = 4.7 Hz, 1H);
2
3
4.40 (m, 1H); 7.06 (d, 3JHH = 8.4, 2H); 7.46 (d, 3JHH = 8.4, 2H).
19F NMR: À76.4 (qn, JFF = 8.7, 3F); À77.8 (dq, JFF = 9.4,
3JFF = 2.0, 3F); À185.6 (complex m, 1F). MS: m/z (rel. int.,
ion): 494, 492 (15, 16, M+); 367, 365 [98, 100, (M À I)+]; 286
[25, (C12H9F7)+]; 169, 171 [14, 14, (C7H6Br)+]; 117 (21).
Analysis: found: C, 29.4; H, 1.8; F, 27.0%. Calculated for
C12H9F7IBr (493.00): C, 29.2; H, 1.8; F, 27.0%.
4
4
3.4. Addition of (CF3)2CFI to allylbenzenes and reactions
of the adducts
3.4.1. Addition of (CF3)2CFI to allylbenzenes
Sodium dithionite (2.1 g, 10 mmol [85%]), sodium hydro-
gen carbonate (1.68 g, 20 mmol), allylbenzene 1a–f (10 mol)
and 2-iodo-heptafluoropropane (4.14 g, 14 mol) were added to
a water–acetonitrile solution (1:1, 40 ml) and the reaction
mixture was vigorously stirred at ambient temperature for 2 h
(CO2 evolution occurred). After completion of the reaction
water (20 ml) was added, the reaction mixture was extracted
with diethyl ether (3 Â 50 ml) and the combined extracts were
dried over MgSO4. The crude mixtures of products obtained
after removal of the solvent was subjected to column
chromatography (silica gel, hexanes:ethanol, 19:1) to give
compounds 13 as colorless liquids.
3.4.2. Reductive deiodination of compound 13a
(4,5,5,5-Tetrafluoro-2-iodo-4-trifluoromethylpentyl)ben-
zene (13a) (2.5 g, 6 mmol) and zinc powder (0.9 g 13 mmol)
were refluxed in ethanol (50 ml) for 10 h and worked up as in
Section 3.3.3 to give (4,5,5,5-tetrafluoro-4-trifluoromethylo-
pentyl)benzene (14a). Colorless liquid. Yield: 0.8 g (46%). 1H
NMR: 1.91 (m, 2H); 2.09 (m, 2H); 2.68 (t, 3JHH = 7.5, 2H); 7.18
(dm, 3JHH = 7.5, 4JHH = 0.6, 2H); 7.22 (tm, 3JHH = ca. 7.3, 1H);
7.31 (m, 2H). 19F NMR: À76.8 (d, 3JFF = 6.05, 6F); À184.2 (m,
3JFF = 6.05, 1F). MS: m/z (rel. int., ion): 288 (8, M+); 266 [52,
(C12H8F6)+]; 259 (19); 197 [44, (C11H8F3)+]; 177 [100,
(C11H7F2)+]; 128 [36, (C10H8)+]; 91 [70, (C7H7)+]. Analysis:
found: C, 50.1; H, 3.8; F, 46.4%. Calculated for C12H11F7
(288.21): C, 50.0; H, 3.8; F, 46.1%. HRMS: found: 288.07528.
Calculated for C12H11F7: 288.07490.
(4,5,5,5-Tetrafluoro-2-iodo-4-trifluoromethylpentyl)ben-
zene (13a): yield: 3.27 g (79%). 1H NMR: 2.84–3.01 (complex
2
AB systems, JHH = 16.4, 2H); 3.13 (dd, JHH = 14.6,
2
2
3
3JHH = 9.2, 1H); 3.28 (dd, JHH = 14.6, JHH = 5.4, 1H); 4.44
(m, 1H, CHI); 7.18 (m, 2H); 7.32 (m, 3H). 19F NMR: À76.7
4
4
(qn, JFF = 8.7, 3F); À77.7 (qn, JFF = 8.7 Hz, 3F); À185.9
(complex m, 1F). MS: m/z (rel. int., ion): 414 (3, M+); 287 [100,
(M À I)+]; 268 [1, (C12H10F6)+]; 247 (1); 189 (4); 127 (9); 117
[31, (C9H9)+]; 91 [87, (C7H7)+]. Analysis: found: C, 35.1, H,
2.6, F, 32.5, I, 30.2%. Calculated for C12H10F7I (414.10): C,
34.8, H, 2.4; F, 32.1, I, 30.6%.
3.4.3. Dehydrohalogenation of compounds 13: preparation
of bis(trifluoromethyl)dienes (15)
Compound 13 (6.2 mmol) was dissolved in hexanes (60 ml)
then DBU (2.82 g, 18.5 mmol) was added (immediately a white
precipitate was formed) and the reaction mixture was refluxed
for 12 h. An excess of the base was removed by washing with
hydrochloric acid (5%, 2 Â 40 ml) followed by brine (40 ml)
and the organic phase was dried over MgSO4. The residue
1-Methyl-4-(4,5,5,5-tetrafluoro-2-iodo-4-trifluoromethyl-
1
pentyl)benzene (13b): yield: 2.52 g (65%). H NMR: 2.33 (s,
2
3H); 2.83–3.02 (complex AB systems, JHH = 16.4 Hz, 2H);

J. Ignatowska, W. Dmowski / Journal of Fluorine Chemistry 128 (2007) 997–1006
1005
obtained after removal of the solvent was subjected to column
chromatography (silica gel, hexanes/ethanol 19:1) to give
dienes 15.
of the reaction mixture exhibited the presence of 12% of
cycloadduct, 2,8-diphenyl-5,5-bis(trifluoromethyl)-5,8-dihy-
dro-[1,2,4]-triazolo[1,2-a]pyridazine-1,3-dione (16). GC–
MS: m/z (rel. int., ion): 441 (100, M+); 422 [4, (M À F)+];
372 [2, (M À CF3)+]; 294 [7, (M À PhC2O2N)+]; 280 [<1,
(C12H8F6N)+]; 225 [50, (C11H8F3N2)+]; 197 [25, (C11H8F3)+];
177 [27, (C11H7F2)+]; 132 [50, (C10H12)+]; 91 [21, (C7H7)+].
(5,5,5-Trifluoro-4-trifluoromethylpenta-1,3-dienyl)benzene
(15a): yield: 1.38 g (84%). Colorless liquid. 1H NMR
3
3
5
(C2D6CO): 7.27 (ddq, JHH = 15.3, JHH = 11.7, JHF = 1.0,
1H); 7.45 (m, 3H); 7.46 (d, overlapped by Ph signal, 3JHH = ca.
3
15 Hz, 1H); 7.59 (dm, JHH = ca.11.6 Hz, 1H); 7.68 (m, 2H).
4
4
19F NMR (C2D6CO): À57.2 (qdd, JFF = 6.8, JHF = 2.0,
5JHF = 1.0, 3F); À62.7 (qdd, 4JFF = 6.8, 4JHF = 2.0, 5JHF = 1.0,
3F). MS: m/z (rel. int., ion): 266 (62, M+); 247 [12, (M À F)+];
227 [7, (C12H7F5)+]; 197 [48, (M À CF3)+]; 177 [100,
(M À HF,CF3)+]; 164 (2); 151 (5); 146 (9); 128 [38,
(M À 2CF3)+]; 115 (9); 91 (18). Analysis: found: C, 54.1; H,
3.1; F, 42.7%. Calculated for C12H8F6 (266.18): C, 54.1; H, 3.0;
F, 42.8%.
3.5. Addition of (CF3)2CFI to allylpyridines 17 followed by
dehydrohalogenation: preparation of
bis(trifluoromethyl)dienes (19)
Allylpyridine 17a or 17b (0.29 g, 2.1 mmol or 1.03 g,
8.6 mmol), Na2S2O4 (0.45 g, 2.1 mmol or 1.8 g, 8.7 mmol),
and NaHCO3 (0.33 g, 4 mmol or 1.68 g, 20 mmol) were
suspended in water–acetonitrile solution (1:1, 10 or 40 ml,
respectively), the suspension was cooled to 0 8C then
(CF3)2CFI (0.68 g, 2.3 mmol or 2.96 g, 10 mmol) was added.
The reaction mixture was stirred at 0 8C for 0.5 h followed by
1 h at ambient temperature. Organic products were extracted
with diethyl ether (3 Â 30 ml), the combined extracts were
dried over MgSO4 and evaporated. The yellowish residue was
dissolved in hexanes, DBU was added (0.95 g, 6.3 mmol or
2.84 g, 18 mmol) and the solution was left at ambient
temperature for 12 h. The residue obtained after removal of
the solvent was subjected to column chromatography (silica
gel, hexanes/ethyl acetate 3:2) to give dienes 19a and 19b as
yellowish solids.
1-Methyl-4-(5,5,5-trifluoro-4-trifluoromethylpenta-1,3-die-
1
nyl)benzene (15b): yield: 1.14 g (81%). Colorless liquid. H
3
NMR (C2D6CO): 2.37 (s, 3H); 7.21 (ddq, JHH = 15.2,
5
3
3JHH = 11.8, JHF = 1.0, 1H); 7.28 (d, JHH = 8.0, 2H); 7.43
(d, 3JHH = 15.2, 1H); 7.55 (overlapped by Ph signal, 1H); 7.57
(d, JHH = 8.0, 2H). 19F NMR (C2D6CO): À57.2 (qd,
3
4JFF = 6.8, JHF = 1.0, 3F); À62.7 (qd, JFF = 6.8, JHF = 1.0,
3F). MS: m/z (rel. int., ion): 280 (100, M+); 261 [14, (M À F)+];
245 [8, (C12H6F5)+]; 211 [40, (M À CF3)+]; 191 [33,
(C12H9F2)+]; 182 (4); 142 [8, (C11H10)+]; 115 (3); 105 (4);
91 (3); 69 (3). Analysis: found: C, 55.4; H, 3.5; F 40.4%.
Calculated for C13H10F6 (280.21): C, 55.7; H, 3.6; F, 40.7%.
1-Methoxy-4-(5,5,5-trifluoro-4-trifluoromethylpenta-1,3-
dienyl)benzene (15e): yield: 2.16 g (82%). White solid. Mp 53–
55 8C. 1H NMR: 3.84 (s, 3H); 6.92 (d, 3JHH = 8.8 Hz, 2H); 7.01
5
4
5
2-(5,5,5-Trifluoro-4-trifluoromethylpenta-1,3-dienyl)pyri-
dine (19a): yield: 0.34 g (60%). Mp 37–39 8C. 1H NMR: 7.40
(ddd, JHH = 7.6, JHH = 4.7, JHH = 1.2, 1Harom.); 7.49 (d,
3
3
4
3
3
4
3JHH = 14.8, 1H); 7.60 (d, 3JHH = 7.6, 1Harom.); 7.66 (d, 3JHH
=
12.0, 1H); 7.80 (dm, JHH = 14.8, 1H); 7.87 (td, JHH = 7.6,
(dm, JHH = ca. 11.3, 2H); 7.16 (dd, JHH = 11.3, JHF = 1.1,
1H); 7.47 (d, 3JHH = 8.8, 2H). 19F NMR: À58.0 (q, 4JFF = 6.8,
3F); À63.5 (q, 4JFF = 6.8, 3F). MS: m/z (rel. int., ion): 296 (100,
M+); 277 [18, (M À F)+]; 227 [82, (M À CF3)+]; 212 [29,
(C10H5F6)+]; 207 [50, (C11H7F2)+]; 195 (9); 183 (10); 164 (31);
158 [30, (C10H8)+]; 145 (12); 133 (13); 115 (30); 69 (16).
Analysis: found: C, 52.3; H, 3.2; F, 38.8%. Calculated for
C13H10F6O (296.21): C, 52.7; H, 3.4; F, 38.5%.
3
3
3
4JHH = 1.8, 1Harom.); 8.67 (dm, JHH = ca. 4.7, 1Harom.). 19F
4
4
5
NMR: À53.3 (qdd, JFF = 6.9; JHF = 2.2, JHF = 1.0, 3F);
À59.1 (qd, 4JFF = 6.9; 5JHF = 1.0, 3F). MS: m/z (rel. int., ion):
267 (39, M+); 248 [17, (M À F)+]; 228 [2, (C11H6F4N)+]; 198
[100, (M À CF3)+]; 178 [17, (C10H6F2N)+]; 148 (5); 128 (5);
104 (3). Analysis: found: C, 49.5; H, 2.5; F, 42.4%. Calculated
for C11H7F6N (267.17): C, 49.4; H, 2.6; F, 42.7%.
1-Bromo-4-(5,5,5-trifluoro-4-trifluoromethylpenta-1,3-die-
1
nyl)benzene (15f): yield: 0.33 g (82%). Colorless liquid. H
3-(5,5,5-Trifluoro-4-trifluoromethylpenta-1,3-dienyl)pyri-
dine (19b): yield:1.24 g (54%). Mp 54–55 8C. 1H NMR:
(C2D6CO): 7.40 (ddd, JHH = 7.6, JHH = 4.7, JHH = 1.2,
3
NMR (C2D6CO): 7.30 (ddq, JHH = 15.3, JHH = 11.6,
3
3
5JHF = 1.0, 1H); 7.45 (d, JHH = 15.3, 1H); 7.59 (dd,
3
3
4
4
3JHH = 11.6, JHF = 0.6, 1H); 7.64 (m, 4H). 19F NMR
3
3
1Harom.); 7.49 (d, JHH = 14.8, 1H); 7.60 (d, JHH = 7.6,
4
4
3
1Harom.); 7.66 (d, JHH = 12.0, 1H); 7.80 (dm, JHH = 14.8,
3
(C2D6CO): À57.2 (q, JFF = 6.8, 3F); À62.8 (q, JFF = 6.8,
3F). MS: m/z (rel. int., ion): 346, 344 (47, 47, M+); 325 (4); 265
[3, (M À Br)+]; 245 [58, (M À Br,HF)+]; 196 [100,
(M À Br,CF3)+]; 177 (7); 146 (10). Analysis: found: C, 41.6;
H, 2.1; Br, 23.2; F, 33.2%. Calculated for C12H7F6Br (345.08):
C, 41.8; H, 2.0; Br, 23.2; F, 33.0%.
3
4
1H); 7.87 (td, JHH = 7.6, JHH = 1.8, 1Harom.); 8.67 (dm,
3JHH = ca. 4.7, 1Harom.). 19F NMR: À53.3 (qdd, JFF = 6.9;
4
4JHF = 2.2, JHF = 1.0, 3F); À59.1 (qd, JFF = 6.9; JHF = 1.0,
3F). MS: m/z (rel. int., ion): 267 (39, M+); 248 [17, (M À F)+];
228 [2, (C11H6F4N)+]; 198 [100, (M À CF3)+]; 178 [17,
(C10H6F2N)+]; 148 (5); 128 (5); 104 (3). Analysis: found: C,
49.5; H, 2.5; F, 42.4%. Calculated for C11H7F6N (267.17): C,
49.4; H, 2.6; F, 42.7%.
5
4
5
3.4.4. Reaction of diene 15a with 4-phenyl-3H-1,2,4-
triazoline-3,5-dione (6)
(5,5,5-Trifluoro-4-trifluoromethylpenta-1,3-dienyl)benzene
(15a) (0.4 g, 1.5 mmol), 4-phenyl-3H-1,2,4-triazoline-3,5-
dione (6) (0.28 g, 1.6 mmol) and MeCN (10 ml) were heated
in a pressure glass ampoule at 80 8C for 96 h. GC–MS analysis
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