Nucleophilic trifluoromethylation of arylidenemalononitriles

Article abstract of DOI:10.1016/j.tetlet.2008.05.039

A method for the nucleophilic trifluoromethylation of arylidenemalononitriles using Me₃SiCF₃ is described. The reaction is carried out in dimethylformamide in the presence of AcONa as a Lewis base, and affords products of Michael addition in high yield.

Full text of DOI:10.1016/j.tetlet.2008.05.039

Tetrahedron Letters 49 (2008) 4352–4354
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Nucleophilic trifluoromethylation of arylidenemalononitriles
*
Alexander D. Dilman , Vitalij V. Levin, Pavel A. Belyakov, Marina I. Struchkova, Vladimir A. Tartakovsky
N. D. Zelinsky Institute of Organic Chemistry, 119991 Moscow, Leninsky Prospect 47, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
A
method for the nucleophilic trifluoromethylation of arylidenemalononitriles using Me3SiCF3 is
Received 10 April 2008
Revised 28 April 2008
Accepted 7 May 2008
Available online 11 May 2008
described. The reaction is carried out in dimethylformamide in the presence of AcONa as a Lewis base,
and affords products of Michael addition in high yield.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Arylidenemalononitriles
Michael reaction
Trifluoromethylation
Table 1
Nucleophilic trifluoromethylation reactions using the Ruppert–
Prakash reagent (Me3SiCF3) have attracted significant attention in
recent years.1 In particular, procedures for the addition of a trifluo-
romethyl carbanion to C@O and C@N bonds have been the subject
of a number of papers.1–3
Variation of the alkene in trifluoromethylation reactions
CF3
1.5 eq. Me3SiCF3, 2 eq. AcONa
DMF, r.t., 3 h
X
Ph
X
Ph
Y
Y
At the same time, examples of the employment of Me3SiCF3 in
Michael addition reactions have remained virtually unexplored.
There are several reports on the successful Michael addition of
Me3SiCF3 to unconventional Michael acceptors—2-perfluoro-
alkylchromones and 2-perfluoroalkyl-4-quinolones.4 In another
publication, the trifluoromethylation of cyclohex-2-enone in com-
bination with sterically bulky aluminum reagents was studied, but
the yields of the products of conjugate addition were moderate.5 It
should be noted that in these reports strongly basic activators such
as Me4NF and t-BuOK were employed for the activation of
Me3SiCF3.
Entry
X
Y
Product
Yielda (%)
1
2
3
4
CO2Me
CO2Me
CO2Me
CN
H
0
b
CO2Me
CN
CN
1
2a
66c
94
a
Isolated yield.
In the 1H NMR spectrum of the crude mixture, the signals attributed to the
b
product did not exceed 15%.
c
The product was formed as a mixture of diastereomers in a 2.2:1 ratio.
Within the framework of our research devoted to the applica-
tions of fluorinated silanes,6,7 we decided to study the behavior
of different electron deficient alkenes toward Me3SiCF3. As a basic
activator we used sodium acetate in DMF, since this system had
been efficient for many other processes.2b,6a,b
As model substrates we employed benzylidene derivatives,
bearing a methoxycarbonyl or a cyano group (Table 1). The triflu-
oromethylation reactions were performed at room temperature
for 3 h, and then quenched with aqueous hydrochloric acid. Methyl
cinnamate was completely unreactive (entry 1), whereas dimethyl
benzylidenemalonate gave a complex mixture containing mostly
starting substrate (ca. 60%) (entry 2). The cyanoacetic ester deriv-
ative provided the corresponding product in 66% yield, with the
remainder of the material balance being unreacted starting alkene
(entry 3). Rewardingly, benzylidenemalononitrile afforded the
desired product in an excellent 94% yield (entry 4).
Given the greater stability of the malononitrile anion compared
to the dialkylmalonate anion,8 these data suggest that the effi-
ciency of trifluoromethylation depends on the electrophilicity of
the alkene substrate.9
Various arylidenemalononitriles were examined in the reaction
with Me3SiCF3 (Table 2). The aromatic ring of the substrate may
contain electron-withdrawing or -donating substituents with both
leading to products in high yields. Interestingly, in the case of a
substrate possessing two sites for possible nucleophilic attack, only
one product, corresponding to attack at the position adjacent to the
malononitrile moiety, was obtained (entry 7).
Besides the trifluoromethyl group, pentafluoroethyl-, pentafluo-
rophenyl-, and dichlorofluoromethyl groups can be transferred to
* Corresponding author. Fax: +7 499 135 53 28.
E-mail address: adil25@mail.ru (A. D. Dilman).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.05.039

A. D. Dilman et al. / Tetrahedron Letters 49 (2008) 4352–4354
4353
Table 2
Russian Science Support Foundation, and the Russian Foundation
for Basic Research (Project 08-03-00428). We thank Dr. M. Elinson
and Dr. A. Shestopalov for gifts of starting compounds.
Trifluoromethylation of arylidenemalononitriles
CF3
1.5 eq. Me3SiCF3, 2 eq. AcONa
CN
CN
CN
Ar
Ar
DMF, r.t., 3 h
References and notes
CN
1. For reviews on the chemistry of Me3SiCF3, see: (a) Prakash, G. K. S.; Yudin, A. K.
Chem. Rev. 1997, 97, 757; (b) Prakash, G. K. S.; Mandal, M. J. Fluorine Chem.
2001, 112, 123; (c) Singh, R. P.; Shreeve, J. M. Tetrahedron 2000, 56, 7613; (d)
Ma, J.-A.; Cahard, D. J. Fluorine Chem. 2007, 128, 975.
2. For addition to C@O bonds, see: (a) Prakash, G. K. S.; Panja, C.; Vaghoo, H.;
Surampudi, V.; Kultyshev, R.; Mandal, M.; Rasul, G.; Mathew, T.; Olah, G. A. J.
Org. Chem. 2006, 71, 6806; (b) Kawano, Y.; Kaneko, N.; Mukaiyama, T. Bull.
Chem. Soc. Jpn. 2006, 79, 1133; (c) Mizuta, S.; Shibata, N.; Akiti, S.; Fujimoto, H.;
Nakamura, S.; Toru, T. Org. Lett. 2007, 9, 3707; (d) Fustero, S.; Albert, L.; Acena, J.
L.; Sanz-Cervera, J. F.; Asensio, A. Org. Lett. 2008, 10, 605.
3. For addition to C@N bonds, see: (a) Prakash, G. K. S.; Mandal, M.; Olah, G. A.
Synlett 2001, 77; (b) Prakash, G. K. S.; Mogi, R.; Olah, G. A. Org. Lett. 2006, 8,
3589; (c) Kirij, N. V.; Babadzhanova, L. A.; Movchun, V. N.; Yagupolskii, Y. L.;
Tyrra, W.; Naumann, D.; Fischer, H. T. M.; Scherer, H. J. Fluorine Chem. 2008,
129, 14; (d) Nelson, D. W.; Owens, J.; Hiraldo, D. J. Org. Chem. 2001, 66,
2572.
4. (a) Sosnovskikh, V. Ya.; Sevenard, D. V.; Usachev, B. I.; Röschenthaler, G.-V.
Tetrahedron Lett. 2003, 44, 2097; (b) Sosnovskikh, V. Ya. V. Ya.; Usachev, B. I.;
Sevenard, D. V.; Röschenthaler, G.-V. J. Org. Chem. 2003, 68, 7747; (c)
Sosnovskikh, V. Ya. V. Ya.; Usachev, B. I.; Sevenard, D. V.; Röschenthaler, G.-V.
J. Fluorine Chem. 2005, 126, 779; (d) Sosnovskikh, V. Ya. V. Ya.; Usachev, B. I.;
Permyakov, M. N.; Sevenard, D. V.; Röeschenthaler, G.-V. Russ. Chem. Bull. 2006,
55, 1687.
Entry
Substrate
Product
Yielda (%)
95
CN
CN
1
2
3
4
5
6
2b
MeO
MeO
CN
CN
2c
2d
2e
2f
98
96
75
83
84
MeO
OMe
CN
CN
CN
CN
O2N
Br
5. Sevenard, D. V.; Sosnovskikh, V. Ya.; Kolomeitsev, A. A.; Königsmann, M. H.;
Röschenthaler, G.-V. Tetrahedron Lett. 2003, 44, 7623.
CN
CN
6. For reactions using Me3SiCF3, see: (a) Dilman, A. D.; Arkhipov, D. E.; Levin, V.
V.; Belyakov, P. A.; Korlyukov, A. A.; Struchkova, M. I.; Tartakovsky, V. A. J. Org.
Chem. 2007, 72, 8604; (b) Levin, V. V.; Kozlov, M. A.; Song, Y.-H.; Dilman, A. D.;
Belyakov, P. A.; Struchkova, M. I.; Tartakovsky, V. A. Tetrahedron Lett. 2008, 49,
3108; (c) Dilman, A. D.; Gorokhov, V. V.; Belyakov, P. A.; Struchkova, M. I.;
Tartakovsky, V. A. Russ. Chem. Bull. 2007, 56, 1522.
7. For reactions of C6F5-substituted silanes, see: (a) Dilman, A. D.; Belyakov, P. A.;
Korlyukov, A. A.; Struchkova, M. I.; Tartakovsky, V. A. Org. Lett. 2005, 7, 2913;
(b) Dilman, A. D.; Levin, V. V.; Karni, M.; Apeloig, Y. J. Org. Chem. 2006, 71, 7214;
(c) Dilman, A. D.; Levin, V. V.; Belyakov, P. A.; Struchkova, M. I.; Tartakovsky, V.
A. Synthesis 2006, 447; (d) Levin, V. V.; Dilman, A. D.; Belyakov, P. A.; Korlyukov,
A. A.; Struchkova, M. I.; Antipin, M. Y.; Tartakovsky, V. A. Synthesis 2006, 489;
(e) Levin, V. V.; Dilman, A. D.; Belyakov, P. A.; Korlyukov, A. A.; Struchkova, M.
I.; Tartakovsky, V. A. Mendeleev Commun. 2007, 105; (f) Dilman, A. D.;
Gorokhov, V. V.; Belyakov, P. A.; Struchkova, M. I.; Tartakovsky, V. A.
Tetrahedron Lett. 2006, 47, 6217; (g) Levin, V. V.; Dilman, A. D.; Belyakov, P.
A.; Struchkova, M. I.; Tartakovsky, V. A. Tetrahedron Lett. 2006, 47, 8959.
8. Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456.
CN
CN
2g
CN
CN
7
2h
87b
a
Isolated yield.
b
2-[3-Phenyl-1-(trifluoromethyl)prop-2-enyl]malononitrile was obtained as the
sole product.
9. For the electrophilicity parameters of arylidenemalononitriles, see: Lemek, T.;
Mayr, H. J. Org. Chem. 2003, 68, 6880.
10. For the synthesis of silanes, see: (a) Me3SiC2F5: Bardin, V. V.; Pressman, L. S.;
Cherstkov, V. F. Synth. Commun. 1995, 25, 2425; Me3SiC6F5: (b) Eaborn, C.;
Treverton, J. A.; Walton, D. R. M. . D. R. M. . J. Organomet. Chem. 1967, 9, 259;
Me3SiCCl2F: (c) Joste, R.; Ruppert, I. J. Organomet. Chem. 1987, 329, 313.
11. Generalprocedure: Sodium acetate (164 mg, 2 mmol) was added to a solution of
arylidenemalononitrile (1 mmol) and Me3SiRf (1.5 mmol) in DMF (2 mL) and
the mixture was stirred for 3 h at room temperature [in the case of Me3SiCCl2F,
the temperature was 0 °C]. For the work-up, the reaction flask was cooled to
0 °C, aq HCl (1.07 mL of 1.4 M) was added, the mixture was stirred for an
additional 2 min, then diluted with water (10 mL), and extracted with ether
(3 Â 5 mL). The combined organic phase was filtered through Na2SO4,
concentrated under vacuum, and the crude product was chromatographed
on silica gel eluting with hexanes/ethyl acetate.
benzylidenemalononitrile from the corresponding silanes10 under
the reported conditions (Scheme 1).
In summary, a convenient method for the Michael addition of a
trifluoromethyl group, as well as other fluorinated fragments, to
arylidenemalononitriles has been elaborated. The reaction pro-
ceeds under mildly basic conditions and leads to the products in
high yields.11 Importantly, this method provides ready access to
functionalized compounds bearing a fluorinated group at the b-
position, which are difficult to synthesize by other means. Our
current research is focused on further development of the
methodology of conjugate addition reactions using fluorinated
silanes.
Methyl 2-cyano-4,4,4-trifluoro-3-phenylbutanoate (1): Oil, Rf = 0.27 (hexanes/
EtOAc, 5:1). Mixture of isomers, ratio 2.2:1. 1H NMR (300 MHz, CDCl3): 3.69 (s,
3H, Me, minor), 3.75 (s, 3H, Me, major), 4.03 (d, 1H, J = 7.3, CHCN, minor), 4.12–
4.23 (m, 1H, CHCF3, both isomers), 4.25 (d, 1H, J = 5.5, CHCN, major), 7.39–7.52
(m, 5H, Ph, both isomers). 13C NMR (75 MHz, CDCl3). Major isomer: 38.5, 49.0
(q, J = 29.3), 54.0, 113.5, 125.0 (q, J = 280.9), 129.1, 129.3, 129.7, 130.4, 163.8.
Minor isomer: 38.5, 49.6 (q, J = 28.8), 53.9, 113.6, 124.8 (q, J = 280.9), 128.8,
129.1, 129.6, 130.5, 163.7. 19F NMR (282 MHz, CDCl3): À68.6 (d, J = 8.5, major),
À67.2 (d, J = 8.5, minor). Calcd for C12H10F3NO2 (257.21): C, 56.04; H, 3.92; N,
5.45. Found: C, 56.28; H, 3.72; N, 5.33.
Acknowledgments
This work was supported by the Ministry of Science (Project
MK-4483.2007.3), Russian Academy of Sciences (Program # 8),
Rf
3a, Rf = C2F5, 97%
1.5 eq. Me3SiRf, 2 eq. AcONa
CN
CN
Ph
CN
3b, Rf = C6F5, 99%
3c, Rf = CCl2F, 81%
Ph
DMF, 3 h
CN
r.t. for Rf = C2F5, C6F5
0 ˚C for Rf = CCl2F
Scheme 1.

4354
A. D. Dilman et al. / Tetrahedron Letters 49 (2008) 4352–4354
2-(2,2,2-Trifluoro-1-phenylethyl)malononitrile (2a): Oil, Rf = 0.20 (hexanes/
123.5, 123.6 (q, J = 281.3), 127.5, 129.9 (q, J = 1.4), 131.1, 132.0 (q, J = 1.4), 134.0.
19F NMR (282 MHz, CDCl3): À67.5 (d, J = 8.5). Anal. Calcd for C11H6BrF3N2
(303.08): C, 43.59; H, 2.00; N, 9.24. Found: C, 43.54; H, 1.98; N, 9.28.
2-[2,2,2-Trifluoro-1-(1-naphthyl)ethyl]malononitrile (2g): Oil, Rf = 0.21 (hexanes/
EtOAc, 6:1). 1H NMR (200 MHz, CDCl3): 4.56 (d, 1H, J = 7.3, CH(CN)2), 5.00–5.19
(m, 1H, CHCF3), 7.55–7.73 (m, 3H, CHAr), 7.84 (d, 1H, J = 7.3, CHAr), 7.95–8.06 (m,
3H, CHAr). 13C NMR (50 MHz, CDCl3): 24.6 (q, J = 2.5), 43.4 (q, J = 29.0), 110.1,
110.3, 121.2, 124.3 (q, J = 281.9), 124.3, 125.1, 126.0 (br s, Dm1/2 = 5.9 Hz), 126.6,
127.8, 129.5, 131.2, 131.4, 134.0. 19F NMR (282 MHz, CDCl3): À66.8 (d, J = 8.5).
Anal. Calcd for C15H9F3N2 (274.24): C, 65.69; H, 3.31; N, 10.21. Found: C, 65.51;
H, 3.35; N, 10.02.
2-[(2E)-3-Phenyl-1-(trifluoromethyl)prop-2-enyl]malononitrile (2h): Oil, Rf = 0.22
(hexanes/EtOAc, 5:1). 1H NMR (300 MHz, CDCl3), d: 3.47–3.60 (m, 1H, CHCF3),
4.23 (d, 1H, J = 4.2, CH(CN)2), 6.16 (dd, 1H, J = 15.8, 9.7, @CHCHCF3), 6.94 (d, 1H,
J = 15.8, PhCH@), 7.33–7.54 (m, 5H, Ph). 13C NMR (75 MHz, CDCl3) d: 24.2 (q,
J = 2.8), 48.6 (q, J = 29.7), 109.4, 110.1, 113.4 (q, J = 2.0), 123.8 (q, J = 281.4),
127.2, 128.9, 129.6, 134.2, 142.1. 19F NMR (282 MHz, CDCl3) d: À69.9 (d, 3F,
J = 8.5). Anal. Calcd for C13H9F3N2 (250.22): C, 62.40; H, 3.63; N, 11.20. Found: C,
62.45; H, 3.69; N, 10.97.
EtOAc, 6:1). 1H NMR (300 MHz, CDCl3): 3.96 (qd, 1H, J = 6.5, 8.2, CHCF3), 4.40
(d, 1H, J = 6.5, CH(CN)2), 7.40–7.68 (m, 5H, Ph). 13C NMR (50 MHz, CDCl3): 24.8
(q, J = 2.5), 50.2 (q, 29.0), 109.8, 110.1, 124.0 (q, J = 282.1), 128.0 (q, J = 1.5),
128.9, 129.7, 130.7. 19F NMR (282 MHz, CDCl3): À67.6 (d, J = 8.2). Anal. Calcd
for C11H7F3N2 (224.18): C, 58.93; H, 3.15; N, 12.50. Found: C, 59.02; H, 3.11; N,
12.44.
2-[2,2,2-Trifluoro-1-(4-methoxyphenyl)ethyl]malononitrile (2b): Mp 40–41 °C,
Rf = 0.26 (hexanes/EtOAc, 4:1). 1H NMR (300 MHz, CDCl3), d: 3.83 (s, 3H,
OMe), 3.91 (dq, 1H, J = 8.4, 6.4, CHCF3), 4.37 (d, 1H, J = 6.4, CH(CN)2), 6.99 (d,2H,
J = 8.8, 2HAr), 7.38 (d, 2H, J = 8.8, 2HAr). 13C NMR (75 MHz, CDCl3) d: 24.9 (q,
J = 2.6), 49.4 (q, J = 29.3), 55.2, 110.0, 110.3, 115.0, 119.7 (q, J = 1.4), 124.1 (q,
J = 281.4), 130.2, 161.2. 19F NMR (282 MHz, CDCl3) d: À68.0 (d, 3F, J = 8.4). Anal.
Calcd for C12H9F3N2O (254.21): C, 56.70; H, 3.57; N, 11.02. Found: C, 56.71; H,
3.52; N, 10.92.
2-[1-(3,4-Dimethoxyphenyl)-2,2,2-trifluoroethyl]malononitrile (2c): Mp 110–
111 °C, Rf = 0.3 (hexanes/EtOAc, 2:1). 1H NMR (300 MHz, CDCl3), d: 3.79–3.98
(m, 7H, 2OMe + CHCF3), 4.40 (d, 1H, J = 6.1, CH(CN)2), 6.92 (d, 1H, J = 8.3, 1HAr),
6.95 (s, 1H, 1HAr), 7.00 (d, 1H, J = 8.3, 1HAr). 13C NMR (75 MHz, CDCl3) d: 25.0 (q,
J = 2.6), 49.9 (q, J = 29.3), 55.9, 56.0, 110.0, 110.2, 111.5 (q, J = 1.1), 111.7, 120.0
(q, J = 1.7), 122.0, 124.0 (q, J = 281.4), 149.6, 150.8. 19F NMR (282 MHz, CDCl3)
d: À67.9 (d, 3F, J = 8.5). Anal. Calcd for C13H11F3N2O2 (284.23): C, 54.93; H,
3.90; N, 9.86. Found: C, 54.91; H, 3.91; N, 9.84.
2-[2,2,2-Trifluoro-1-(2-methoxyphenyl)ethyl]malononitrile (2d): Oil, Rf = 0.26
(hexanes/EtOAc, 4:1). 1H NMR (200 MHz, CDCl3): 3.91 (s, 3H, OMe), 4.50 (d,
1H, J = 7.1, CH(CN)2), 4.63–4.80 (m, 1H, CHCF3), 7.00–7.14 (m, 2H, CHAr), 7.43–
7.54 (m, 2H, CHAr). 13C NMR (50 MHz, CDCl3): 23.6 (q, J = 2.2), 42.6 (q,
J = 29.8), 55.7, 110.3, 110.4, 111.4, 116.5 (q, J = 1.5), 121.3, 124.3 (q, J = 281.4),
128.8 (q, J = 1.5), 131.7, 157.1. 19F NMR (282 MHz, CDCl3): À66.8 (d, J = 8.5).
Anal. Calcd for C12H9F3N2O (254.21): C, 56.70; H, 3.57; N, 11.02. Found: C,
56.77; H, 3.58; N, 10.88.
2-[2,2,2-Trifluoro-1-(4-nitrophenyl)ethyl]malononitrile (2e): Oil, Rf = 0.24
(hexanes/EtOAc, 4:1). Mp 97–98 °C. 1H NMR (200 MHz, CDCl3): 4.05–4.22 (m,
1H, CHCF3), 4.53 (d, 1H, J = 5.9, CH(CN)2), 7.74 (d, 2H, J = 8.9, CHAr), 8.39 (d, 2H,
J = 8.9, CHAr). 13C NMR (50 MHz, CDCl3): 24.4 (q, J = 2.5), 49.6 (q, J = 29.8),
109.4, 109.6, 123.5 (q, J = 281.8), 124.7, 130.4, 134.5, 149.3. 19F NMR (282 MHz,
CDCl3): À67.3 (d, J = 6.8). Anal. Calcd for C11H6F3N3O2 (269.18): C, 49.08; H,
2.25; N, 15.61. Found: C, 49.18; H, 2.19; N, 15.56.
2-(2,2,3,3,3-Pentafluoro-1-phenylpropyl)malononitrile
(3a):
Oil,
Rf = 0.26
(hexanes/EtOAc, 6:1). 1H NMR (300 MHz, CDCl3): 3.96 (dt, 1H, J = 23.6, 5.6,
CHC2F5), 4.53 (d, 1H, J = 5.6, CH(CN)2), 7.46–7.56 (m, 5H, Ph). 13C NMR (75 MHz,
CDCl3): 24.3 (m), 47.7 (t, J = 19.6), 110.2, 110.4, 114.0 (ddq, J = 264.3, 259.3,
37.6), 118.1 (qt, J = 287.5, 35.4), 127.6 (d, J = 5.5), 129.3 (d, J = 2.2), 129.6, 130.8.
19F NMR (282 MHz, CDCl3): À122.5 (dd, 1F, J = 23.6, 270.0, CFAFB), À111.3 (dd,
1F, J = 270.0, 5.6, CFAFB), À82.3 (s, 3F, CF3). Anal. Calcd for C12H7F5N2 (274.19): C,
52.57; H, 2.57; N, 10.22. Found: C, 52.64; H, 2.59; N, 10.14.
2-[(Pentafluorophenyl)(phenyl)methyl]malononitrile (3b): Mp 89–90 °C, Rf = 0.30
(hexanes/EtOAc, 6:1). 1H NMR (300 MHz, CDCl3), d: 4.79 (d, 1H, J = 12.1,
CH(CN)2), 5.00 (d, 1H, J = 12.1, CHC6F5), 7.30–7.55 (m, 5H, Ph). 13C NMR
(75 MHz, CDCl3) d: 26.8 (t, J = 5.3), 43.2, 111.0, 111.1, 111.3 (tm, J = 14.6),
127.4 (t, J = 1.4), 129.7, 129.8, 134.0, 138.0 (dm, J = 251.0), 141.4 (dm,
J = 257.6), 144.9 (dm, J = 247.7). 19F NMR (282 MHz, CDCl3) d: À159.8 (m, 2F),
À152.0 (t, 1F, J = 21.1), À141.8 (d, 2F, J = 17.8). Anal. Calcd for C16H7F5N2
(322.23): C, 59.64; H, 2.19; N, 8.69. Found: C, 59.54; H, 2.02; N, 8.57.
2-(2,2-Dichloro-2-fluoro-1-phenylethyl)malononitrile
(3c): Mp
77–78 °C,
Rf = 0.25 (hexanes/EtOAc, 6:1). 1H NMR (200 MHz, CDCl3): 4.16 (dd, 1H,
J = 5.6, 16.2, CHCCl2F), 4.77 (d, 1H, J = 5.6, CH(CN)2), 7.45–7.63 (m, 5H, Ph). 13C
NMR (50 MHz, CDCl3): 26.1, 60.5 (d, J = 20.8), 110.2, 110.6, 119.7 (d, J = 302.9),
129.4, 129.5 (d, J = 2.2), 130.1, 130.6. 19F NMR (282 MHz, CDCl3): À55.7 (d,
J = 16.2). Anal. Calcd for C11H7Cl2FN2 (257.09): C, 51.39; H, 2.74; N, 10.90.
Found: C, 51.27; H, 2.63; N, 10.79.
2-[1-(3-Bromophenyl)-2,2,2-trifluoroethyl]malononitrile (2f): Oil, Rf = 0.29
(hexanes/EtOAc, 5:1). 1H NMR (200 MHz, CDCl3): 3.85–4.02 (m, 1H, CHCF3),
4.40 (d, 1H, J = 6.4, CH(CN)2), 7.34–7.50 (m, 2H, CHAr), 7.48–7.74 (m, 2H, CHAr).
13C NMR (50 MHz, CDCl3): 24.6 (q, J = 2.8), 49.6 (q, J = 29.1), 109.6, 109.8,