The chemical transformation of β-bromodifluoromethyl β-enaminoketones: Synthesis of difluoromethylene thioether compounds

Article abstract of DOI:10.1016/j.jfluchem.2005.10.015

A series of 2-bromodifluoromethylquinoline derivatives were synthesized by cyclization of β-bromodifluoromethyl β-enaminoketones catalyzed by polyphosphoric acid. Difluoromethylene thioether or ether derivatives of quinoline and but-2-en-1-one were obtain

Full text of DOI:10.1016/j.jfluchem.2005.10.015

Journal of Fluorine Chemistry 127 (2006) 223–228
www.elsevier.com/locate/fluor
The chemical transformation of b-bromodifluoromethyl
b-enaminoketones: Synthesis of difluoromethylene
thioether compounds
*
Yong-Ming Wu , Ya Li, Juan Deng
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Rd, Shanghai 200032, China
Received 20 September 2005; received in revised form 18 October 2005; accepted 24 October 2005
Available online 18 January 2006
Abstract
A series of 2-bromodifluoromethylquinoline derivatives were synthesized by cyclization of b-bromodifluoromethyl b-enaminoketones
catalyzed by polyphosphoric acid. Difluoromethylene thioether or ether derivatives of quinoline and but-2-en-1-one were obtained by the
subustitute reaction of CF2Br with thio- and oxygen nucleophiles.
# 2005 Published by Elsevier B.V.
Keywords: b-Bromodifluoromethyl b-enaminoketones; 2-Bromodifluoromethyl-quinoline; Difluoromethylene thioether; Gem-difluorinated quinolines; Thiophe-
nols; Cyclization; Nucleophilic substitution
1. Introduction
[8], we found that b-bromodifluoromethyl b-enaminoketones
showed unique properties compared with their non-fluorinated
analogues because of the existence of BrCF2 group [9]. Herein,
we would like to report the research result of cyclization
reaction of b-bromodifluoromethyl b-enaminoketones to the
corresponding 2-bromodifluoromethyl quinolines by treatment
with PPA and the substitution reaction of bromine in CF2Br
group by thio-nucleophiles to afford difluoromethylene
thioether compounds.
The synthesis and reactivity of b-enaminoketones represent
an active area of investigation in organic chemistry [1]. The
special value of these compounds is due to their use as valuable
intermediate for the synthesis of several interesting compounds
[2]. They can also be used as starting materials for the
stereoselective preparation of g-amino alcohol [3]. b-Enam-
inoketones can usually be prepared in several ways: the direct
condensation of the appropriate amine with symmetrical b-
dicarbonyl compounds affording the simplest one [4], while the
acylation of lithium imines with ester supplies another way for
their regioselective preparation [5].
Quinolines have been an exceptionally important class of
heterocycles [10], and they occur in various natural products,
especially in alkaloids. Since the discovery of the antiprotozoal
drugmefloquine [11], the development of fluorinated quinolines
has received considerable attention in recent years due to their
unique biological activity [12]. Although many reports on the
synthesis of fluorinated quinolines are presented in the
literature [13], however, there are few reports on the synthesis
of halodifluoromethyl quinolines [14], and so far as we know,
no general method for preparing them was reported. Such
halodifluoromethyl quinolines would be a very useful starting
material to build a variety of CF2-containging quinolines as it is
anticipated that the carbon–halogen bond should be quite
reactive in SET reactions, both chemically and electrochemi-
cally.
In recent years, the introduction of the difluoromethylene
segment into organic compounds has been proved to be
attractive, due to the potential biological properties of such
molecules [6]. Bromodifluoroacetate, chlorodifluomethyl
ketones and bromodifluoromethyl acetylene are widely used
as reagents for introducing a CF2 moiety into molecules [7]. In
search for new CF2-containing reactive synthetic intermediates
* Corresponding author. Tel.: +86 2154925190; fax: +86 21 64166128.
E-mail address: ymwu@mail.sioc.ac.cn (Y.-M. Wu).
0022-1139/$ – see front matter # 2005 Published by Elsevier B.V.
doi:10.1016/j.jfluchem.2005.10.015

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Y.-M. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 223–228
Table 1
Table 2
Synthesis of 2-bromodifluoromethyl quinolines
Synthesis of gem-difluorinated quinolines
Entry
R
Product
Yield (%)
Entry
1
R-XH
Product
Yield (%)
98
1
2
3
p-OCH3
o-Cl
2a
2b
2c
77
78
83
3a
o-CH3, p-Br
2
3
3b
3c
100
94
2. Results and discussion
4
5
3d
3e
94
88
N-Aryl enaminoketones are excellent precursor to quinolines
[15]. Cyclization of the b-enaminoketones 1 in polyphosphoric
acid at 120 8C for 5 h gave the corresponding 2-bromodifluor-
omethyl quinoline 2 in moderate to good yield (Table 1).
Expected with CF2Br group in 2 would be reactive with
sulfur nucleophiles. Initial experiments with 2a and sodium 4-
bromobenzenthiolate in DMF at room temperature led to the
observation that the reaction was rapid and cleanly affording
the desired product 3a in high yield. It was soon discovered that
a variety of anions derived from thiols, phenolic compounds
and ethyl alcohol were able to successfully react with 2a giving
the desired products in high yield (Scheme 1). The results are
shown in Table 2.
6
3f
87
the reductive product 5 in 16% yield (Scheme 2). Screening a
variety of solvents (DMA, THF, CH3CN and DMSO) to
minimize the reduction product only met with failure.
The results of the reaction with other nucleophiles are
illustrated in Table 3.
As shown in Table 3, the substitution reaction of 1 with
various anions derived from thiophenols proceeded readily with
satisfactory yields (Entries 1,2,3,4,5). However, when sodium
p-methoxylphenolate was used as the nucleophile, a competing
reaction occurred. The desired intermolecular product 4e was
isolated in 18% yield (Entry 5) together with the intramolecular
product9 in 35% yield in CH3CN after 24 h at room
temperature, while the product 3a was obtained as the sole
product when the reaction was carried out in dried DMF. The
reaction of 1a with the anions from ethanethiol or a-
toluenethiol gave the sole reductive product 5, this might be
due to the low nucleophility of the thio-reagents. The fact that
1,4-dinitrobenzene could not inhibit this transformation
indicated that halophilic process was involved.
The displacement of bromide from the CF2Br group does not
occur by a simple SN2 mechanism due to the presence of the
alpha fluorines. Instead, it proceeds by a SRN1 mechanism
involving a SET chain process. The inhibition by 1,4-
dinitrobenzene is the evidence for the SRN1 mechanism.
One can envision that when a thio-nucleophole was added to
b-bromodifluoromethyl b-enaminoketones 1,
a SET or
halophilic substitution also would occur. We carried out the
reaction using a mixture of 1a and benzenethiol in dried DMF
with NaOH as the base at room temperature. The desired
substitute product 4a was obtained in 76% yield together with
Scheme 1.
Scheme 2.

Y.-M. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 223–228
225
Table 3
The reaction of b-bromodifluoromethyl b-enaminoketones 1 with thio-nucleophiles
Entry
1
R-XH
Sovlent
DMF
Product
Yield(%)
69
4a
2
3
DMF
DMF
4b
4c
71
76
4
5
DMF
4d
4e
78
18
CH3CN
3. Conclusion
Mg2SO4. Filtration and subsequent concentration and column
chromatography (3% ethyl acetate in petroleum) gave 2a
(140 mg, 77%).
In conclusion, we have developed a general method for
the synthesis of 2-bromodifluoromethyl quinolines by the
cyclization of the b-bromodifluoromethyl enaminoketones
catalyzed by PPA. The CF2Br group in quinolines and b-
bromodifluoromethyl b-enaminoketones 1 can be converted
to the corresponding difluoromethylene thioether or ether
compounds by the substitution reaction with thiopehnol and
phenol anions.
4.2. 2-(Bromodifluoromethyl)-6-methoxyl-4-phenyl-
quinoline (2a)
1
Yield: 77%; white solid, mp 97–98 8C; H NMR (300 Hz,
CDCl3) d 8.18 (d, J = 9.60 Hz, 1H), 7.62 (s, 1H), 7.53–7.57 (m,
5H), 7.25 (dd, J1 = 9.60, 2.70 Hz, 1H), 7.23 (d, J = 2.70 Hz,
1H), 3.82 (s, 3H); 19F NMR (282 Hz, CDCl3) dÀ50.17 (s); IR
(film, cmÀ1) 2964, 1620, 1509, 1474, 1222, 1085; m/z (EI) 363
(6.16), 284 (100.00), 268 (6.38), 234 (1.73), 75 (1.87), 51
(1.80); Anal. Calcd for C17H12BrF2NO: C, 56.07; H, 3.32; N,
3.85; Found C, 56.27; H, 3.62; N, 3.81.
4. Experimental
Unless otherwise noted, solvents and reagents were
1
commercial available and used as received. H NMR spectra
were recorded on a Brucker AM-300 (300 MHz) spectrometer
with Me4Si as internal standard. 19F NMR spectra were taken
on Brucher AM-300 (282 MHz) spectrometer with CFCl3 as
external standard, downfield shifts being designed as positive.
The 13C NMR spectra were measured at Brucker AM-300
(75 MHz) spectrometer with all protons decoupled, and the
chemical shifts are reported in ppm downfield of SiMe4. Mass
spectra were taken on a HP 5989a spectrometer, and accurate
mass measurements were performed on Finnigan MAT
instrument, while elemental analysis were performed by this
institute.
4.3. 2-(Bromodifluoromethyl) -8-chloro-4-phenyl-quinoline
(2b)
Yield: 78%; yellow solid, mp 94–96 8C; 1H NMR (300 Hz,
CDCl3) d 7.90–7.96 (m, 2H), 7.42 (s, 1H), 7.51–7.59 (m, 6H);
19F NMR(282 Hz, CDCl3) d–50.99 (s); IR (film, cmÀ1) 1760,
1607, 1556, 1489, 1228, 1097, 823; m/z (EI) 369 (11.48), 288
(100.00), 238 (19.60), 203 (32.18); HRMS (EI): M+, found
366.9580650. C16H9BrClF2N requires 366.95749.
4.4. 6-Bromo-2-(bromodifluoromethyl)-8-methyl-4-phenyl-
quinoline (2c)
4.1. Preparation of 2-bromodifluoromethyl quinolines 2
1
General procedure: A mixture of b-bromodifluoromethyl
enaminoketone 1a (191 mg, 0.5 mmol), polyphosphoric acid
(4 ml) was stirred at 120 8C for 3 h. The cooled mixture was
then neutralized with aqueous 5 N NaOH with ice bath
cooling. The mixture was extracted with ethyl ether
(3 Â 15 ml). The combined organic layers were dried over
Yield: 83%; white solid, mp 97–99 8C; H NMR (300 Hz,
CDCl3) d 7.94 (d, J = 1.80 Hz, 1H), 7.77–7.78 (m, 1H), 7.67 (s,
1H), 7.56–7.59 (m, 3H), 7.49–7.52 (m, 2H), 2.88 (s, 3H); 19F
NMR (282 Hz, CDCl3) dÀ50.37 (s); IR (film, cmÀ1) 2964,
1620, 1509, 1474, 1222, 1085, 869, 761; m/z (EI) 427 (32.81),
346 (100.00), 298 (5.40), 217 (26.62), 75 (2.96); Anal. Calcd

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Y.-M. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 223–228
for C17H11Br2F2N: C, 47.81; H, 2.60; N, 3.28; Found C, 48.05;
H, 2.63; N, 3.18.
7.52–7.55 (m, 5H), 7.43 (dd, J = 9.30, 3.00 Hz, 1H), 7.20 (d,
J = 2.70 Hz, 1H), 3.79 (s, 3H), 3.05 (q, J = 7.50 Hz, 2H),
1.42 (t, J = 7.50 Hz, 3H); 19F NMR (282 Hz, CDCl3)
dÀ74.36 (s); IR (film, cmÀ1) 3049, 2974, 1624, 1587,
1494, 1475, 1266, 1222, 1086; m/z (EI) 326 (0.30), 285
(100.00), 270 (9.25), 253 (3.14), 241 (4.91), 191 (14.34);
Anal. Calcd for C19H17F2NOS: C, 66.07; H, 4.96; N, 4.06;
Found C, 66.04; H, 4.93; N, 4.01.
4.5. Preparation of gem-difluorinated quinolines 3
Sodium p-bromobenzenethiolate (46 mg, 0.22 mmol) in
DMF (1 ml) was added to 2-bromodifluoromethyl quinoline 2a
at room temperature. Half saturated NaCl (5 ml) was added
after 20 min. The mixture was extracted with ethyl ether
(2 Â 10 ml). The combined organic layers were dried over
Mg2SO4. Filtration and subsequent concentration and column
chromatography (10% ethyl acetate in petroleum) gave 3a
(87 mg, 98%).
4.10. 2-[(4-Methoxylphenoxy)difluoromethyl]-6-methoxy-
4-phenyl-quinoline (3e)
Yield: 88%; white solid, mp 110–112 8C; 1H NMR
(300 Hz, CDCl3) d 8.31 (d, J = 9.30 Hz, 1H), 7.61 (s, 1H),
7.56 (s, 5H), 7.47 (dd, J = 9.30, 2.70 Hz, 1H), 7.30 (d,
J = 9.00 Hz, 2H), 7.23 (d, J = 2.70 Hz, 1H), 6.89 (d,
J = 9.00 Hz, 2H), 3.82 (s, 3H), 3.81 (s, 3H); 19F NMR
(282 Hz, CDCl3) dÀ70.14 (s); IR (film, cmÀ1) 3004, 2960,
2833, 1620, 1594, 1505, 1475, 1265, 1168; m/z (EI) 407
(13.80), 388 (0.56), 341 (0.85), 284 (100.00), 252 (1.88);
Anal. Calcd. for C24H19F2NO3: C, 70.75; H, 4.70; N, 3.44;
Found C, 70.77; H, 4.71; N, 3.42.
4.6. 2-[(4-Bromophenylsulfanyl)-difluoromethyl]-6-
methoxyl-4-phenyl-quinoline (3a)
Yield: 98%; white solid, mp 150–151 8C; 1H NMR (300 Hz,
CDCl3) d 8.18 (d, J = 9.00 Hz, 1H), 7.43–7.58 (m, 11H), 7.21
(d, = 3.00 Hz, 1H), 3.81 (s, 3H); 19F NMR (282 Hz, CDCl3)
dÀ73.03 (s); IR (film, cmÀ1) 3053, 2833, 1622, 1587, 1492,
1474, 1220, 1043, 954; m/z (EI) 471 (1.24), 284 (100.00), 268
(4.00), 252 (1.64), 241 (5.24), 191 (6.81); Anal. Calcd for
C23H16BrF2NOS: C, 58.48; H, 3.44; N, 2.97; Found C, 58.57;
H, 3.45; N, 2.84.
4.11. 2-Ethoxydifluoromethyl-6-methoxy-4-phenyl-
quinoline (3f)
4.7. 2- (4-Methoxylphenylsulfanyl) difluoromethyl-6-
methoxyl-4-phenylquinoline (3b)
Yield: 87%; white solid, mp 99–100 8C; 1H NMR (300 Hz,
CDCl3) d 8.23 (d, J = 9.30 Hz, 1H), 7.65 (s, 1H), 7.54–7.56 (m,
5H), 7.43 (dd, J = 9.30, 2.70 Hz, 1H), 7.20 (d, J = 2.70 Hz, 1H),
4.21 (q, J = 7.50 Hz, 2H), 3.80 (s, 3H), 1.41 (t, J = 7.50 Hz,
Yield: 100%; white solid, mp 106–107 8C; 1H NMR
(300 Hz, CDCl3) d 8.22 (d, J = 9.00 Hz, 1H), 7.62 (d,
J = 9.00 Hz, 2H), 7.48–7.54 (m, 6H), 7.45 (dd, J = 9.30,
2.70 Hz, 1H), 7.20 (d, J = 2.70 Hz, 1H), 6.91 (dd, J = 9.30,
1.80 Hz, 2H), 3.83 (s, 3H), 3.81 (s, 3H); 19F NMR (282 Hz,
CDCl3) dÀ74.89 (s); IR (film, cmÀ1) 3010, 2944, 1622, 1589,
1494, 1474, 1251, 1221, 1069, 954; m/z (EI) 423 (6.55), 284
(100.00), 268 (4.21), 268 (3.83), 252 (1.73), 241 (5.40), 191
(8.33); Anal. Calcd for C24H19F2NO2S: C, 68.07; H, 4.52; N,
3.31; Found C, 68.05; H, 4.78; N, 3.23.
3H); 19F NMR (282 Hz, CDCl3) dÀ73.82 (s); IR (film, cmÀ1
)
3055, 2984, 2836, 1624, 1591, 1494, 1283, 1172, 1108; m/z (EI)
329 (0.30), 285 (100.00), 270 (25.34), 242 (5.44), 190 (14.68),
126 (3.60); Anal. Calcd for C19H17F2NO2: C, 69.29; H, 5.20; N,
4.25; Found C, 69.58; H, 5.10; N, 4.19.
4.12. Preparation of g, g-difluorinated b-enaminoketones 4
A mixture of b-bromodifluoromethyl enaminoketone 1a
(191 mg, 0.5 mmol), benzenethiol (77 mg, 0.7 mmol) and
NaOH (32 mg, 0.8 mmol) in dried DMF (2 ml) was stirred at
room temperature for 5 h. Then saturated NaCl (5 ml) was
added. The mixture was extracted with ethyl ether (2 Â 10 ml).
The combined organic layers were dried over Mg2SO4.
Filtration and subsequent concentration and column chromato-
graphy (10% ethyl acetate in petroleum) gave 4a (142 mg,
69%) and 5 (24 mg, 16%).
4.8. 2-Benzylsulfanyldifluoromethyl-6-methoxyl-4-phenyl-
quinoline (3c)
Yield: 94%, oil; 1H NMR (300 Hz, CDCl3) 8.18 (d,
J = 9.60 Hz, 1H), 7.64 (s, 1H), 7.52–7.56 (m, 5H), 7.26–7.46
(m, 6H), 7.21 (d, J = 2.70 Hz, 1H), 4.29 (s, 2H), 3.81 (s, 3H);
19F NMR (282 Hz, CDCl3) dÀ74.12 (s); IR (neat, cmÀ1) 3061,
2936, 2832, 1621, 1589, 1494, 1474, 1268, 1079; m/z (EI) 408
(6.95), 316 (0.80), 285 (100.00), 270 (9.11), 253 (2.69), 234
(4.31); Anal. Calcd for C24H19BrF2NOS: C, 70.74; H, 4.70; N,
3.44; Found C, 70.67; H, 4.84; N, 3.30.
4.13. 4,4-Difluoro-4-phenylsulfanyl-3-(4-
methoxylphenylamino)-1-phenylbut-2-en-1-one (4a)
Yield: 69%; yellow solid, mp 102–103 8C; 1H NMR
(300 Hz, CDCl3) d 12.41 (s, 1H), 7.83–7.86 (m, 2H), 7.28–
7.51 (m, 10H), 6.91 (d, J = 9.00 Hz, 2H), 6.16 (s, 1H), 3.85 (s,
4.9. 2-Ethylsulfanyldifluoromethyl-6-methoxyl-4-phenyl-
quinoline (3d)
3H); 19F NMR (282 Hz, CDCl3) dÀ72.45 (s); IR (film, cmÀ1
)
2996, 2836, 1609, 1584, 1512, 1247, 1088, 964; m/z (EI) 411
(13.36), 282 (3.29), 252 (59.62), 105 (97.25), 77 (100.00);
Yield: 94%; white solid, mp 102–103 8C; 1H NMR
(300 Hz, CDCl3) d 8.20 (d, J = 9.30 Hz, 1H), 7.63 (s, 1H),

Y.-M. Wu et al. / Journal of Fluorine Chemistry 127 (2006) 223–228
227
Anal. Calcd for C23H19F2NO2S: C, 67.14; H, 4.65; N, 3.40;
Found C, 67.01; H, 4.63; N, 3.32.
(25.08), 105 (100.00); HRMS (EI): M+, found 426.1502.
C24H22F2NO4 requires 426.15114.
4.14. 4,4-Difluoro-4-(4-methylphenylsulfanyl)-3-(4-
methoxyphenylamino)-1-phenylbut-2-en-1-one (4b)
4.18. 4,4-Difluoro-3-(4-methoxyphenylamino)-1-
phenylbut-2-en-1-one (5)
Yield: 71%; yellow solid, mp 98–100 8C; 1H NMR
(300 Hz, CDCl3) d 12.41 (s, 1H), 7.882–7.85 (m, 2H), 7.28–
7.51 (m, 7H), 7.15 (d, J = 8.40 Hz, 2H), 6.90 (d, J = 8.40 Hz,
2H), 6.11 (s, 1H), 3.85 (s, 3H), 2.33 (s, 3H); 19F NMR
(282 Hz, CDCl3) dÀ72.97 (s); 13C NMR d 190.56, 158.42,
154.93 (t, J = 24.5 Hz), 140.94, 139.29, 136.71, 131.78,
131.15, 129.97, 128.52, 128.43, 127.37, 123.89 (t,
J = 283.7 Hz), 122.41, 113.74, 91.77 (m), 55.47, 21.27; IR
(film, cmÀ1) 3007, 2971, 2839, 1608, 1561, 1511, 1278,
1089, 963; m/z (EI) 425 (21.75), 302 (3.76), 282 (6.87), 270
(3.42), 252 (94.56), 105 (100.00); HRMS (MALDI):
M+ + H+, found 426.1309. C24H22F2NO2S+ requires
426.13393.
Yield: 16%; yellow solid, mp 59–60 8C; 1H NMR (300 Hz,
CDCl3) d 12.29 (s, 1H), 7.98 (dd, J = 8.10, 1.50 Hz, 2H), 7.48–
7.52 (m, 3H), 7.19 (d, J = 8.70 Hz, 2H), 6.93 (d, J = 8.70 Hz,
2H), 6.37 (s, 1H), 6.26 (t, J = 53.0 Hz, 1H), 3.85 (s, 3H); 19F
NMR (282 Hz, CDCl3) dÀ118.00 (d, J = 53.0 Hz, 2F); IR (film,
cmÀ1) 3066, 2910, 2837, 1615, 1585, 1558, 1507, 1380, 1276,
1246, 1116; m/z (EI) 303 (100.00), 252 (89.24), 198 (12.34),
174 (6.80), 146 (9.61); Anal. Calcd for C17H15F2NO2: C, 67.32;
H, 4.98; N, 4.62; Found C, 67.28; H, 5.00; N, 4.50.
Acknowledgment
The authors thank the National Natural Science Foundation
of China (NNSFC) (No. 20472104 and 20532040) for financial
support.
4.15. 4-(2-Chlorophenylsulfanyl)-4,4-difluoro-3-(4-
methoxy-phenylamino)-1-phenylbut-2-en-1-one (4c)
References
Yield: 76%; yellow solid, mp 71–72 8C; 1H NMR
(300 Hz, CDCl3) d 12.42 (s, 1H), 7.86 (dd, J = 8.40,
1.20 Hz, 2H), 7.60 (dd, J = 7.80, 1.20 Hz, 1H), 7.42–7.52
(m, 4H), 7.25–7.32 (m, 3H), 7.25–7.28 (m, 1H), 6.90 (d,
J = 9.00 Hz, 2H), 6.18 (s, 1H), 3.84 (s, 3H); 19F NMR
(282 Hz, CDCl3) dÀ72.24 (s); IR (film, cmÀ1) 3011, 2968,
2835, 1609, 1585, 1562, 1514, 1275, 1120; m/z (EI) 445
(10.45), 302 (2.50), 282 (2.80), 252 (61.08), 105 (71.71);
Anal. Calcd for C23H18ClF2NO2S: C, 61.95; H, 4.07; N, 3.14;
Found C, 61.81; H, 3.92; N, 3.10.
´
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Yield: 78%; yellow solid, mp 105–107 8C; 1H NMR
(300 Hz, CDCl3) d 12.38 (s, 1H), 7.83–7.86 (m, 2H), 7.46–
7.52 (m, 5H), 7.29–7.34 (m, 4H), 6.90 (d, J = 9.00 Hz, 2H),
6.15 (s, 1H), 3.85 (s, 3H); 19F NMR (282 Hz, CDCl3)
dÀ72.28 (s); IR (film, cmÀ1) 2954, 2835, 1609, 1583, 1507,
1471, 1273, 1243; m/z (EI) 489 (12.08), 302 (4.81), 282
(5.85), 252 (100.00), 105 (84.68); Anal. Calcd for
C23H18BrF2NO2S: C, 56.34; H, 3.70; N, 2.86; Found C,
56.59; H, 3.69; N, 2.76.
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