Reactions of some nitrogen heterocycles with chlorodifluoromethane under conditions of phase-transfer catalysis

Article abstract of DOI:10.1016/j.jfluchem.2005.09.013

Aromatic heterocyclic compounds containing one to four nitrogen atoms react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and a catalyst, benzyltriethylammonium chloride (TEBAC) in dichloromethane or THF (phase-transfer catalysis, PTC) with formation of N-difluoromethyl substituted derivatives. The process takes place by reaction of N-anions from these heterocycles with difluorocarbene and protonation of difluoromethyl anions thus formed.

Full text of DOI:10.1016/j.jfluchem.2005.09.013

Journal of Fluorine Chemistry 126 (2005) 1587–1591
www.elsevier.com/locate/fluor
Reactions of some nitrogen heterocycles with chlorodifluoromethane
under conditions of phase-transfer catalysis
*
Andrzej Jonczyk , Ewelina Nawrot, Michał Kisielewski
´
Warsaw University of Technology, Faculty of Chemistry, Koszykowa St. 75, 00-662 Warszawa, Poland
Received 29 June 2005; received in revised form 15 September 2005; accepted 18 September 2005
Abstract
Aromatic heterocyclic compounds containing one to four nitrogen atoms react with chlorodifluoromethane in the presence of concentrated
aqueous sodium hydroxide and a catalyst, benzyltriethylammonium chloride (TEBAC) in dichloromethane or THF (phase-transfer catalysis, PTC)
with formation of N-difluoromethyl substituted derivatives. The process takes place by reaction of N-anions from these heterocycles with
difluorocarbene and protonation of difluoromethyl anions thus formed.
# 2005 Elsevier B.V. All rights reserved.
Keywords: Phase-transfer catalysis; Difluorocarbene; N-difluoromethylation; Nitrogen heterocycles
1. Introduction
Little is known about the application of alkali metal
hydroxides and a quaternary ammonium salt as a catalyst
(phase-transfer catalysis, PTC [12–14]) for difluoromethylation
of nitrogen heterocycles with 1. The preparation of N-
difluoromethylated herbicides from aryltriazolinones, under
these conditions, was patented [15,16].
Chlorodifluoromethane (1) treated with a base generates
difluorocarbene [1,2], possibly without intervention of chlor-
odifluoromethyl anion [3]. This electrophilic carbene generated
from 1 under different basic conditions has been utilized for
difluoromethylation of nitrogen heterocycles. Thus, the
reaction with pyrazole, benzopyrazoles or perimidines was
carried out in aqueous-acetone solution of potassium hydroxide
[4], with 4-ethoxycarbonylpyrazole in the presence of solid
potassium carbonate in DMF [5], with phenylazoles with
sodium hydride in THF or DMF [6], and with 2-mercaptoazoles
with potassium hydroxide in i-propanol–water mixture or DMF
[7]. In the case of indoles, the process was performed with
sodium t-butoxide [8] or sodium hydride in DMF [9]; the
former base was also applied for the reaction of carbostyril,
giving mixture of N- and O-derivatives [8]. Similarly,
quinoxalin-2-ones afforded mixtures of N- and O-difluoro-
methylated compounds in moderate yield when solid potassium
carbonate or casium fluoride in DMF were applied [10], while
the reaction of spiro[imidazolidine(quinazoline)]trione with
sodium hydride in DMF led to formation only of the N-
derivative [11].
2. Results and discussion
Chlorodifluoromethane (1) is not suitable for the preparation
of gem-difluorocyclopropanes from alkenes under PTC condi-
tions [17,18] since difluorocarbene generated from 1 by a
concerted a-elimination [3] at the interface of the two-phase
system, hydrolyzed at a high rate [19]. However, literature data
indicate that even large amounts of water in the basic system do
not disturb the reaction of 1 with nitrogen heterocycles, and
N-difluoromethylated products were formed in satisfactory
yields [4,7].
These results encouraged us to investigate reaction of
aromatic heterocycles which posses one to four nitrogen atoms
2a–k and 6 with 1, carried out in the presence of 50% aqueous
sodium hydroxide and benzyltriethylammonium chloride
(TEBAC) as a catalyst in dichloromethane or THF (liquid–
liquid variant of PTC).
Reaction of indole (2a) with 1 led to formation of
N-derivative 3a (yield 50%), while the products from
* Corresponding author. Fax: +48 22 628 27 41.
´
E-mail address: anjon@ch.pw.edu.pl (A. Jonczyk).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.09.013

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1588
Scheme 1.
Scheme 3.
3-methylindole and carbazole were insufficiently stable for
isolation either by column chromatography or by vacuum
distillation. According to the literature, when 2,3-dimethylin-
dole was allowed to react with ethyl chlorodifluoroacetate and
potassium t-butoxide, 3-difluoromethyl-2,3-dimethyl-3H-
indole was formed [20]. Under the conditions studied, pyrrole
formed by PTC the product in ca. 8% yield (determined by GC).
Series of aromatic diazaheterocycles 2b–j reacted with
chlorodifluoromethane (1) affording N-difluoromethyl substi-
tuted derivatives 3b–j, often in good yields. In the case of
derivatives possessing, a hydroxy group 2i,j O-difluoromethy-
lation competed with N-difluoromethylation, giving the
products 3i,j and disubstituted derivatives 4 and 5. Bis-
difluoromethylation was already noticed during reactions of 2-
mercaptoazoles [6]. Amide 2f was exclusively difluoromethy-
lated at the ring nitrogen atom. Acetyl derivative 2g was rather
unstable under PTC conditions; hence, the yield of 3g was only
13%.
hydrolysis of N-difluoromethyl into N-formyl derivative is
facilitated by the presence of highly basic nitrogen atom. To
confirm the pathway (b), reaction of 2h with 1 was carried out
under PTC conditions, in excess of carbon tetrachloride. This
reagent chlorinates carbanions easily by an halophilic process
[24,25]. The reaction studied afforded 1-chlorodifluoromethyl-
2-phenylbenzimidazole (8) in 21% yield apart from the product
3h (Scheme 4).
This product is not formed when 3h was allowed to react
with carbon tetrachloride under PTC conditions. The results
described above testify that halogenation of N-difluoromethyl
anion competed with its protonation.
A liquid–liquid variant of PTC is a convenient tool for N-
difluoromethylation of a variety of aromatic nitrogen hetero-
cycles with chlorodifluoromethane (1) via reaction of their N-
anions with difluorocarbene. The procedure is simple and the
process is rather fast affording the products often in good
yields.
Chlorodifluoromethane (1) reacted smoothly with benzo-
triazole (2k) and less easily with 5-benzyl-1H-tetrazole (6)
giving the products 3k or 7 in 72 and 38% yield, respectively
(Schemes 1 and 2). In the latter case, a mixture of regioisomers
resulted, to which structures 7a and 7b have been tentatively
ascribed (NOE experiments did not solve this problem).
All reactions of 1 with nitrogen heterocycles were carried
out under mild conditions, at 20–40 8C, and occurred at a rather
high rate.
3. Experimental
3.1. General
Melting points were measured on a capillary melting point
apparatus and are uncorrected. 1H NMR spectra were
recorded on a Varian Mercury (at 400 MHz) or Varian
Gemini (at 200 MHz), 13C NMR spectra on a Varian Mercury
(at 100 MHz) spectrometers in CDCl3 with tetramethylsilane
as internal reference. 19F NMR spectra were recorded on a
Varian Mercury (at 376 MHz) in CDCl3 with trifluoroacetic
acid as internal reference. All chemical shifts are reported in
ppm (d = 0.00). The abbreviations used are as follows: s,
singlet; d, doublet; t, triplet; q, quartet; m, multiplet. Gas
chromatography (GC) analyses were carried out on a gas
chromatograph, Agilent 6850 Series GC System equipped
with HP-50+ (30 m) column. Microanalyses were obtained
using a CHN/S Perkin-Elmer 2400 element analyzer.
Column chromatography was performed using Merck basic
aluminiumoxid 90 (70–230 mesh) with hexane and ethyl
acetate mixtures (gradient) as eluents. Chlorodifluoromethane
Two mechanistic pathways leading to N-difluoromethyla-
tion of heterocycles have been considered [4,6,21]: (a) reaction
of difluorocarbene with p-electron pair of nitrogen atom leading
to a N-ylide which further enters [1,2]H shift or (b) its reaction
with a N-anion affording the basic N-difluoromethyl anion
which gave the product after protonation (Scheme 3).
It is well established that the PTC conditions are sufficiently
basic to cause deprotonation of a variety of azoles [22,23];
hence, mechanistic pathway (b) seems more plausible. When a
weak N–H acidic compound, not able to generate a N-anion
under PTC conditions is allowed to react with 1, N-formylation
occurred, e.g. morpholine gave N-formyl derivative in good
yield. In this case mechanistic pathway (a) is involved and
Scheme 4.
Scheme 2.

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1589
(1) and heterocycles 2a–d,h were commercial materials,
while benzimidazoles 2e [26], 2f [27], 2g [28], 2i,2j [29],
benzotriazole 2k [30] and benzyltetrazole 6 [31] were
prepared by literature procedures.
phase was decanted, worked up and the product was isolated by
column chromatography (Table 1).
3a, liquid, b.p. 76–78 8C/3.5 Torr, 1H NMR d 6.65 (d,
J = 3.2 Hz,1H), 7.27 (t, J = 61 Hz, 1H, CHF2), 7.29 (d,
J = 3.6 Hz, 1H),, 7.24–7.31 (m, 2H), 7.56–7.58 (m, 1H),
7.64–7.66 (m, 1H). 13C NMR d 105.9, 110.0 (t, J = 246 Hz,
CHF2), 110.6, 121.4, 121.9, 123.1, 129.6, 134.0. 19F NMR d –
95.7 (d, JH–F = 61 Hz, 2F). HRMS calcd. for C9H7NF2:
167.0546. Found: 167.0544.
3.2. General procedure for N-difluoromethylation of
nitrogen heterocycles (2a–d)
Into a three-necked, round-bottomed flask equipped with
reflux condenser, mechanical stirrer and glass pipe for
introducing 1, heterocycle 2a–d (40 mmol), 50% aq. NaOH
(6.4 ml, 9.6 g, 120 mmol), TEBAC (0.454 g, 2 mmol) and
CH2Cl2 or THF (ca. 50 ml) were placed. The content of the
flask was stirred for ca. 2 min, then chlorodifluoromethane (1)
was bubbled through the mixture for 0.5–3 h, and the progress
of the reaction was monitored by GC. The mixture was diluted
with CH2Cl2 (50 ml), the organic phase was decanted from
semisolid inorganic one which sticks to the wall of the reaction
flask, and dried over MgSO4. The solvent was evaporated under
reduced pressure and the residue was purified by vacuum
distillation (Table 1).
3b, liquid, b.p. 62–63 8C/15 Torr, literature [3] b.p. 155–
1
156 8C/740 Torr, H NMR d 7.10 (t, J = 61 Hz, 1H, CHF2),
7.15 (s, 1H), 7.20 (t, J = 1.4 Hz, 1H), 7.81 (s, 1H). 13C NMR d
108 (t, J = 251 Hz, CHF2), 114.9, 130.9, 134.4. 19F NMR d
À96.2 (d, JH–F = 61 Hz, 2F). HRMS calcd. for C4H4N2F2:
118.0342. Found: 118.0343.
3c1, liquid, b.p. 65–66 8C/10 Torr, 1H NMR d 2.21 (d,
J = 0.4 Hz, 3H), 6.79 (t, J = 1.2 Hz, 1H), 7.02 (t, J = 61 Hz, 1H,
CHF2), 7.67 (d, J = 1.2 Hz, 1H). 13C NMR d 8.6, 108.0 (t,
J = 248 Hz, CHF2),110.7, 128.1, 133.7. 19F NMR d À96.6 (d,
J
H–F = 61 Hz, 2F).
3c2, liquid, b.p. 65–66 8C/10 Torr, 1H NMR d 2.30 (d,
J = 0.8 Hz, 3H), 6.89 (s, 1H), 7.00 (t, J = 60 Hz, 1H, CHF2),
7.70 (s, 1H). 13C NMR d 12.7, 108.5 (t, J = 248 Hz, CHF2),
110.7, 128.1, 134.6. 19F NMR d À98.3 (d, JH–F = 60 Hz, 2F).
HRMS calcd. for C5H6N2F2: 132.0499. Found: 132.0495.
3d, solid, b.p. 67–68 8C/0.3 Torr, literature [3] b.p. 102–
103 8C/2 Torr, m.p. 40–41 8C, literature [3] m.p. 42–43 8C, 1H
NMR d 7.37 (t, J = 60 Hz, 1H, CHF2) 7.35–7.40 (m, 2H), 7.59–
7.62 (m, 1H), 7.82–7.84 (m, 1H), 8.16 (s, 1H). 13C NMR d
3.3. General procedure for N-difluoromethylation of
nitrogen heterocycles (2e–k) and (6)
The reactions were carried out as described in p. 3.1 starting
from heterocycle 2e–k or 6 (6 mmol), 50% aq. NaOH (0.96 ml,
1.44 g, 18 mmol), TEBAC (68 g, 0.3 mmol) and THF (20 ml).
The mixture was diluted with CH2Cl2 (20 ml), the organic
Table 1
Difluoromethylation of nitrogen heterocycles 2a–k with chlorodifluoromethane (1) under PTC conditions
Nos. 2 and 3
R1
R2
Y
Z
Temperature (8C)
Solvent
CH2Cl2
Product
Puritya (%)
96
Yield (%)
50b
a
CH=CH–
CH=CH
H
CH
CH
40
b
c
d
H
H
CH
CH
CH
N
N
N
20
40
20
CH2Cl2
CH2Cl2
THF
99
99
97
40b
46b,c
65b
Me
CH=CH–
CH=CH
CH=CH–
CH=CH
CH=CH–
CH=CH
CH=CH–
CH=CH
CH=CH–
CH=CH
CH=CH–
CH=CH
CH=CH–
CH=CH
CH=CH–
CH=CH
e
f
CMe
N
N
N
N
N
N
N
20
20
20
20
20
20
20
THF
THF
THF
THF
THF
THF
THF
99
67d
69d
13d
91d
50d,e
36d,f
72d
CCONH2
CCOMe
CPh
98
g
h
i
96
ca. 100
95
CCH(OH)Me
CCH(OH)Ph
N
j
98
k
99
a
Determined by GC.
b
c
d
e
f
Isolated by vacuum distillation.
Mixture of 1-difluoromethyl-4-methylimidazole (3c1) and 1-difluoromethyl-5-methylimidazole (3c2), ratio 2:1.
Isolated by column chromatography.
Additionally, 1-difluoromethyl-2-(1-difluoromethoxy)ethylbenzimidazole (4) was isolated in 11% yield (purity 99%).
Additionally, 1-difluoromethyl-2-(1-difluoromethoxy)benzylbenzimidazole (5) was isolated in 28% yield (purity 96%).

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A. Jonczyk et al. / Journal of Fluorine Chemistry 126 (2005) 1587–1591
1590
108.9 (t, J = 248.4 Hz, 1C, CHF2), 111.1, 120.6, 124.2, 124.8,
130.3, 139.1, 143.4. 19F NMR d À98.6 (d, JH–F = 60 Hz, 2F).
Anal. calcd. for C8H6F2N2: C, 57.2, H, 3.6, N, 16.7. Found: C,
57.3, H, 3.5, N, 16.7.
5, liquid, 1H NMR d 6.52 (t, J = 73 Hz, 1H, OCHF2), 6.73 (s,
1H), 7.35 (t, J = 58 Hz, 1H, NCHF2), 7.34–7.42 (m, 7H), 7.40–
7.85 (m, 2H). 13C NMR d 72.9, 108.8 (t, J = 247.2 Hz, 1H
NCHF2), 112.8, 115.9 (t, J = 262 Hz, 1H, OCHF2), 120.8,
124.3, 125.3, 125.6, 129.1, 129.2, 132.1, 134.8, 142.1, 148.9,
166.6. 19F NMR d –86.8, –89.4 (part AB of ABX, JF–
F = 161.1 Hz, JH–F = 73 Hz, 2F, OCHF2), –100.3, À101.6 (part
AB of ABX, JF–F = 226.7 Hz, JH–F = 58 Hz, 2F, NCHF2). Anal.
calcd. for C16H12F4N2O: C, 59.3, H, 3.7, N, 8.6. Found: C, 59.3,
H, 3.7, N, 8.7.
1
3e, solid, m.p. 61–62 8C, literature [3] m.p. 62–63 8C, H
NMR d 2.70 (s, 3H), 7.28 (t, J = 59 Hz, 1H, CHF2), 7.27–7.33
(m, 2H), 7.51–7.55 (m, 1H), 7.68–7.72 (m, 1H). 13C NMR d
14.5, 108.8 (t, J = 246.5 Hz, 1C, CHF2), 110.5, 119.7, 123.7,
123.8, 132.0, 142.5, 149.4. 19F NMR d –99.2 (d, JH–F = 58 Hz,
2F). Anal. calcd. for C9H8F2N2: C, 59.3, H, 4.4, N, 15.4. Found:
C, 59.3, H, 4.5, N, 15.4.
1
3k, solid, m.p. 38–40 8C, H NMR d 7.46–7.50, (m, 1H),
7.59–7.64 (m, 1H), 7.81 (d, J = 8.4 Hz, 1H), 7.86 (t, J = 58 Hz,
1
3f, solid, m.p. 182–184 8C, H NMR d 6.03 (s, 1H), 7.42–
7.51 (m, 2H), 7.63 (s, 1H), 7.80–7.85 (m, 2H), 8.77 (t,
J = 59 Hz, 1H, CHF2). 13C NMR d 109.5 (t, J = 249.5 Hz, 1H,
CHF2), 113.8, 121.3, 125.0, 126.7, 132.6, 141.1, 160.6. 19F
NMR d À100.6 (d, JH–F = 59 Hz, 2F). Anal. calcd. for
C9H7F2N3O: C, 51.2, H, 3.3, N, 19.9. Found: C, 51.2, H,
3.4, N, 19.8.
1H, CHF2), 8.11–8.13 (m, 1H). 13C NMR d 110.7, 111.3 (t,
J = 249.5 Hz, 1C, CHF2), 120.4, 125.5, 129.4, 129.9, 146.4. 19
F
NMR d À101.9 (d, JH–F = 58 Hz, 2F). Anal. calcd. for
C7H5F2N3: C, 49.7, H, 3.0, N, 24.8. Found: C, 49.8, H, 3.1,
N, 24.6.
7a, liquid, 1H NMR d 4.34 (s, 2H), 7.28–7.36 (m, 5H), 7.58
(t, J = 56 Hz, 1H, CHF2). 13C NMR d 31.7, 108.7 (t,
J = 258.2 Hz, 1C, CHF2), 127.2, 128.7, 128.8, 135.4, 167.1.
19F NMR d À102.6 (d, JH–F = 58 Hz, 2F). Anal. calcd. for
C9H8F2N4: C, 51.4, H, 3.8, N, 26.7. Found: C, 51.4, H, 3.8, N,
26.7.
7b, liquid, 1H NMR d 4.43 (s, 2H), 7.28–7.37 (m, 5H), 7.57
(t, J = 58 Hz, 1H, CHF2). 13C NMR d 29.6, 108.7 (t,
J = 255.9 Hz, 1C, CHF2), 127.8, 128.7, 128.9, 132.9, 153.7.
19F NMR d À91.2 (d, JH–F = 58 Hz, 2F). Anal. calcd. for
C9H8F2N4: C, 51.4, H, 3.8, N, 26.7. Found: C, 51.3, H, 3.9, N,
26.5.
3g, liquid, 1H NMR d 2.86 (s, 3H), 7.43–7.53 (m, 2H), 7.80–
7.83 (m, 1H), 7.90–7.93 (m, 1H), 8.49 (t, J = 59 Hz, 1H, CHF2).
13C NMR d 27.8, 109.4 (t, J = 249.6 Hz, 1C, CHF2), 113.9,
122.3, 125.2, 127.8, 130.9, 141.6, 144.4, 192.9. 19F NMR d
À100.0 (d, JH–F = 59 Hz, 2F). Anal. calcd. for C10H8F2N2O: C,
57.2, H, 3.8, N, 13.3. Found: C, 57.3, H, 3.9, N, 13.5.
3h, solid, m.p. 35–37 8C, 1H NMR d 7.29 (t, J = 58 Hz, 1H,
CHF2), 7.39–7.42 (m, 2H), 7.56–7.589 (m, 3H), 7.72–7.87 (m,
4H). 13C NMRd 110.1(t, J = 246.8 Hz, 1C, CHF2), 112.7, 120.4,
124.3, 124.5, 128.6, 129.2, 129.4, 130.9, 131.7, 142.9, 151.8. 19
F
NMR d À99.1 (d, JH–F = 58 Hz, 2F). Anal. calcd. for
C14H10F2N2: C, 68.9, H, 4.1, N, 11.5. Found: C, 68.8, H, 4.1,
N, 11.5.
3.4. Preparation of 1-chlorodifluoromethyl-2-
phenylbenzimidazole (8)
1
3i, solid, m.p. 65–67 8C, H NMR d 1.51 (m,3H), 5.07 (q,
J = 6.9 Hz, 1H), 5.99 (s, 1H, OH), 7.15–7.64 (m, 4H), 8.02 (t,
J = 59 Hz, NCHF2). 13C NMR d 22.1, 64.6, 109.3 (t,
J = 246.5 Hz, 1C, NCHF2), 112.6, 119.4, 123.9, 124.6,
131.6, 141.1, 154.9. 19F NMR d À100.6, –101.5 (part AB of
ABX, JF–F = 229.3 Hz, JH–F = 59 Hz, 2F, NCHF2). Anal. calcd.
for C10H10F2N2O: C, 56.6, H, 4.8, N, 13.2. Found: C, 56.5, H,
4.7, N, 13.1.
To three-necked, round-bottomed flask equipped with reflux
condenser, mechanical stirrer and glass pipe for introducing 1,
imidazole 2h (970 mg, 5 mmol), 50% aq. NaOH (0.8 ml, 1.2 g,
15 mmol), TEBAC (57 mg, 0.25 mmol), CCl4 (20 ml) and THF
(10 ml) were placed. The content of the flask was stirred for ca.
2 min, then 1 was bubbled through the reaction mixture at ca.
20 8C for 3 h and at 50 8C for 2 h. The mixture was diluted with
CH2Cl2 (20 ml), worked up as described in p. 3.1 (GC indicated
47% of 8, 27% of 3h and 24% of unreacted 2h) and the product
was isolated by column chromatography.
8, liquid, 1H NMR d 7.49–7.53 (m, 5H), 7.66–7.92 (m, 3H),
7.84–7.86 (m, 1H). 13C NMR d 112.9, 120.6, 121.3 (t,
J = 290 Hz, 1C, CHF2), 124.7, 125.1, 128.1, 129.5, 130.2,
130.3, 132.3, 142.7, 151.1. 19F NMR d À35.6 (s, 2F). Anal.
calcd. for C13H9ClF2N2: C, 60.3, H, 3.3, N, 10.1, Cl, 12.7.
Found: C, 60.3, H, 3.4, N, 10.0, Cl, 12.7.
1
4, liquid, H NMR d 1.82 (d, J = 1.7 Hz, 3H), 5.71 (q,
J = 6.8 Hz, 1H), 6.35, (t, J = 73 Hz, 1H, –OCHF2), 7.36–7.39
(m, 2H), 7.68 (t, J = 59 Hz, 1H, –NCHF2), 7.69–7.79 (m, 2H).
13C NMR d 20.9, 67.9, 108.9 (t, J = 246.9 Hz, 1C, NCHF2),
112.6, 115.7 (t, J = 261 Hz, 1C, OCHF2), 120.6, 124.2, 125.1,
132.0, 141.9, 150.1. 19F NMR d À87.6, À88.1 (part AB of
ABX, JF–F = 161.7 Hz, JH–F = 73 Hz, 2F, OCHF2), À99.3,
À100.6 (part AB of ABX, JF–F = 228.6 Hz, JH–F = 59 Hz, 2F,
NCHF2). Anal. calcd. for C11H10F4N2O: C, 50.4, H, 3.8, N,
10.7. Found: C, 50.3, H, 3.8, N, 10.7.
3j, solid, m.p. 126–128 8C, 1H NMR d 6.27 (s, 1H), 6.69 (s,
1H), 7.25–7.36 (m, 7H), 7.57–7.61 (m, 2H), 7.63 (t, J = 58 Hz,
1H, –NCHF2). 13C NMR d 69.9, 108.9 (t, J = 247.2 Hz, 1C,
NCHF2), 112.7, 119.7, 124.1, 124.8, 125.4, 128.3, 128.8, 131.7,
138.7, 141.1, 153.7. 19F NMR d À91.9, À92.4 (part AB of
ABX, JF–F = 213.4 Hz, JH–F = 58 Hz, 2F, NCHF2). Anal. calcd.
for C15H12F2N2O: C, 65.7, H, 4.4, N, 10.2. Found: C, 65.9, H,
4.8, N, 10.0.
References
[1] E.V. Dehmlow, in: M. Regitz (Ed.), Houben-Weyl, Methoden der Orga-
nischen Chemie, George Thieme Verlag, Stuttgart, New York E19b, 1989,
pp. 1467–1486.
[2] P. Kirsch, Modern Fluoroorganic Chemistry: Synthesis, Reactivity Appli-
cations, Wiley, VCH, 2004, pp. 141–143.
[3] J. Hine, J.J. Porter, J. Am. Chem. Soc. 79 (1957) 5493–5496.

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