Two ways of preparing benzonitriles using BrCCl3-PPh3 as the reagent

Article abstract of DOI:10.3184/174751914X13891131118347

Benzamides were converted into benzonitriles with BrCCl₃- PPh₃-Et₃N in CH₂Cl₂ in an Appel-type reaction. Benzaldoximes could be transformed to benzonitriles under identical conditions. It was found that the reaction system BrCCl₃-(2 equiv.)PPh₃ was also suitable for these transformations with PPh ₃ replacing Et₃N.

Full text of DOI:10.3184/174751914X13891131118347

80 RESEARCH PAPER
FEBRUARY, 80–84
JOURNAL OF CHEMICAL RESEARCH 2014
Two ways of preparing benzonitriles using BrCCl3–PPh3 as the reagent
Yosef Al Jasema, Mohamed Barkhada, Mona Al Khazalib, Hifsa Pervez Butta,
Noha Ashraf El-Khwassc, Mariam AlAzanid, Bassam al Hindawid and Thies Thiemannd*
aDepartment of Chemical Engineering and bDepartment of Petroleum Engineering, Faculty of Engineering, United Arab Emirates University, Al
Ain, Abu Dhabi, UAE
cDepartment of Chemistry, Cairo University, Cairo, Egypt
dDepartment of Chemistry, Faculty of Science, United Arab Emirates University, Al Ain, Abu Dhabi, UAE
Benzamides were converted into benzonitriles with BrCCl3–PPh3–Et3N in CH2Cl2 in an Appel-type reaction. Benzaldoximes could
be transformed to benzonitriles under identical conditions. It was found that the reaction system BrCCl3–(2 equiv.)PPh3 was
also suitable for these transformations with PPh3 replacing Et3N.
Keywords: Appel-type reaction, benzamides, benzaldoximes, benzonitriles, bromotrichloromethane
The combination of triphenylphosphine and tetrachlorocarbon
(PPh3–CCl4) as a reagent has been used extensively, such as
in the exchange of an alcohol group for a chloro substituent,
which is the original “Appel reaction”, in the synthesis of gem-
dichloroalkenes from aldehydes and ketones, and in amidation
reactions.1 These transformations have been grouped under
the name of “Appel-type” reactions. In some instances,
tetrachlorocarbon has been exchanged for tetrabromocarbon
(CBr4)2,3 such as for the preparation of gem-dibromoalkenes4,5
from aldehydes and ketones, which is also used as the first
step in the Corey–Fuchs reaction to form alkynes. CBr4 is
more expensive than CCl4 and thus does not lend itself readily
as a replacement for CCl4 in other transformations such as in
activating acids for dehydrative coupling and other dehydration
reactions. On the other hand, CCl4 is listed as an ozone class
one depletor, and for many purposes, CCl4 has been phased
out, due to the provisions of the Montreal protocol.6 However,
recent observations have documented a continuing increase
of atmospheric CCl4 concentration, most likely due to its long
lifetime in the atmosphere, but perhaps also due to continuing
emissions.7 Additionally, it has been noted that CCl4 is a
probable human carcinogen.8 This is all the more reason that
CCl4 is no longer used as a solvent for chemical reactions.
Against this background, there is an interest in exchanging
one chloro atom in CCl4 for a bromo atom. As the C–Br bond
exhibits a lower dissociation energy than the C–Cl bond,
photochemically induced homolytic cleavage will produce
a bromo radical at a comparatively longer wavelength.
Additionally, the replacement of one chloro atom in CCl4 for
a bromo atom as in bromotrichloromethane (BrCCl3) leads to
an albeit small dipole moment (0.4 Debye), which makes for
slightly better scavenging of BrCCl3 from the atmosphere
through moisture scavenging and precipitation. Both of the
above would lead to a greater likelihood of BrCCl3 over CCl4
being scavenged from the atmosphere before reaching the
stratosphere. Thus, while BrCCl3 is also expected to have a
rather long half-life (44 years)9 in the atmosphere, it is not listed
as an ozone depletor (class 1 or 2). It has been noted that were
BrCCl3 to reach the stratosphere, photolysis would occur but
not at an environmentally important rate as compared to CCl4.10
Over the years, BrCCl3 has been looked at in Appel-type
reactions, but not in a methodical fashion. Initial experiments
of Clement and Soulen had shown that reaction of acyl cyanides
with the combination BrCCl3–PPh3 leads to the corresponding
3,3-dichloroacrylonitriles at lower temperatures and in higher
yields than with the reaction system CCl4–PPh3.11 These results
have been taken up recently by the group of Lautens,12 who
could show that benzaldehydes and acetophenones could be
converted into the dichloromethylenated products with ease.
They also showed that benzyl alcohols and cinnamyl alcohol
can be chlorinated with BrCCl3–PPh3.12 Barstow and Hruby
observed amidation when reacting acetic acid with amines
in the presence of BrCCl3–PPh3.13 Also, the current group
have communicated the use of BrCCl3–PPh3 in dehydration
reactions such as in the transformation of cinnamic acids to
cinnamic anhydrides and also in the esterification of cinnamic
acids.14 In the following, we now report on a formal dehydration
of benzamides and of benzaldoximes to benzonitriles using the
reagent system BrCCl3–PPh3–Et3N or BrCCl3–(2 equiv.)PPh3
(see Fig. 1).
There are a number of methods to prepare benzonitriles
from benzamides by formal dehydration. Early methods used
phosphorus pentoxide (P2O5) or phosphoroxychloride (POCl3),
which have been reinvestigated recently under microwave
O
CN
CBrCl3 / PPh3
NH2
R
(Et3N)
CH2Cl2
R
l 3
h
C
r
2
B
3
1
C
P
H
P
)
N
t 3
C
l 2
CHO
E
C
(
H 2
NH2OH.HCl
NOH
R
R
EtOH, H2O
4
3
i. conc. H2SO4; ii. aq. Na2CO3
Fig. 1
* Correspondent. E-mail: thiesthiemann@yahoo.de
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JOURNAL OF CHEMICAL RESEARCH 2014 81
irradiation.15 More contemporary methods include the use of
silanes under Fe2(CO)9 catalysis16 or ethyl dichlorophosphate/
DBU.17 In 1971, Appel et al.18 published the reaction of
benzamidestobenzonitrileswithPPh3–CCl4, withtriethylamine
as base. Independently, Yamato and Sugasawa19 communicated
similar results. We now report that CCl4 can be replaced with
the more environmentally friendly BrCCl3. The addition of
BrCCl3 to triphenylphosphine (PPh3) in dichloromethane leads
within minutes to a yellow–brown coloured solution, to which
the amide is added, which leads to partial decolourisation of
the solution. After keeping the solution at reflux temperature
for 30 min., triethylamine is added. The addition leads to
a noticeably exothermic reaction, with the solution turning
reddish.Aqueouswork-upandstraightforwardchromatographic
separation led to the respective benzonitriles in good yield
(Table 1). Yamato and Sugasawa19 reported on diminished
yields when using triethylamine as base as opposed to using
triphenylphosphine. Therefore, we also investigated the reagent
system BrCCl3–(2 equiv.)PPh3 (Table 2). We have found a small
increase in the yield of 4-nitrobenzonitrile (2j) when using the
latter. However, the 2-alkoxybenzamides, which reacted nicely
with BrCCl3–PPh3–Et3N, did not react well with BrCCl3–
(2 equiv.)PPh3. While Yamato and Sugasawa19 used THF as
the solvent, after investigation of various solvents, we opted
for CH2Cl2 for simplicity of the subsequent chromatographic
work-up.
Thereafter, we turned to investigating the reagent system
BrCCl3–PPh3–Et3N for the dehydration of benzaldoximes to
benzonitriles. Dehydration reactions of benzaldoximes to
benzonitriles have been carried out, among others, over doped
zeolites,20 mesoporous molecular sieves (Al-MCM-41),21 and
a tungsten-tin mixed hydroxide.22 In the case of acidic sites
on the heterogeneous catalysts, however, often the donor-
substituted benzaldoximes undergo Beckmann rearrangement
as a side reaction.20,21 In 1971, Appel et al.23 communicated the
reaction of aldoximes to nitriles with PPh3–CCl4. Recently,
this reaction methodology has been augmented with the
Table 1 Conversion of benzamides to benzonitriles with CBrCl3–PPh3–Et3N
O
CN
NH2 CBrCl3 / PPh3
R
R
Et3N
CH2Cl2
2
1
O
O
CN
CN
OR
NH2
NH2
OR
1h
2h (71%)
R = CH3 (1a)
C2H5 (1b)
C3H7 (1c)
C4H9 (1d)
C5H11 (1e)
C8H17 (1f)
O
R = CH3 (2a) (92%)
C2H5 (2b) (90%)
C3H7 (2c) (87%)
C4H9 (2d) (87%)
C5H11 (2e) (85%)
C8H17 (2f) (78%)
O
CN
1i
Cl 2i (65%)
CN
Cl
O
CN
NH2
NH2
O2N
O
O
O2N
2j (73%)
1j
2g (82%)
1g
use of the 3-butyl-1,2-dimethyl-1H-imidazozoliundiphenyl
phosphinebenzenesulfonate-CBr4 reagent.24
We found that the reagent system BrCCl3–PPh3–Et3N works
well for the dehydration of benzaldoximes to benzonitriles
(Table 3). While Appel et al.23 had used 1,2-dichloroethane
and Kim et al.25 had reported on the use of acetonitrile for the
system CCl4–PPh3, we again used CH2Cl2 as solvent in the
reactions, mostly because of the simplicity of the subsequent
reaction work-up. The preparation of the benzaldoximes
themselves was carried out by reaction of the corresponding
benzaldehydes with hydroxylamine hydrochloride. In the case
of 2-nitro-, 4-nitro, 3-chloro- and 3-bromobenzaldoximes, the
product could be crystallised in water and could be used in the
transformation to the respective benzonitrile after air-drying
the filtered product. All other benzaldoximes were purified by
column chromatography on silica gel.
Table 2 Conversion of benzamides and benzaldoximes to benzonitriles with BrCCl3– (2 equiv.) PPh3
O
CN
CBrCl3
CBrCl3
NH2
NOH
R
R
R
PPh3 (2 eq.)
PPh3 (2 eq.)
CH2Cl2
CH2Cl2
1
4
2
CN
O
NOH
CN
EtO
EtO
NH2
O2N
4n
4e
2v (90%)
O2N
CN
2j (87%)
1j
NOH
O2N
MeO
O
O2N
CN
2j (92%)
NH2
CN
MeO
MeO
NOH
OC3H7
OC3H7
2c (23%)
1c
MeO
4i
2q (92%)
OMe
OMe
OMe
CN
O
O
O
NOH
CN
NOH
O
4m
2u (91%)
4h
2p (39%)
OMe
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82 JOURNAL OF CHEMICAL RESEARCH 2014
Table 3 Conversion of benzaldoximes to benzonitriles with BrCCl3–PPh3–Et3N
H
C
CN
CBrCl3 / PPh3
NOH
R
Et3N
CH2Cl2
R
4
2
NOH
H
H
NC
H3CO
H
CN
NOH
OCH3
H3CO
OCH3
H3C
X
H3C
X
2k (86%)
4a
2p (60%)
4h
NOH
CN
NC
H
NOH
OCH3
OCH3
X = Br (2L, 83%), Cl (2i, 81%)
F (2m, 80%)
X = Br (4b), Cl (4c), F (4d)
2q (96%)
4i
H
OCH3
OCH3
H
CN
CN
NOH
NOH
(H3C)2N
O2N
O2N
4e
2j (87%)
4j
(H3C)2N
2r (69%)
H
H
NOH
CN
CN
NOH
4f
2n (96%)
H3CO
H3CO
H
CN
2s (75%)
4k
4L
NOH
4g
NO2
CN
2o (92%)
NOH
NO2
2t (87%)
9-Anthranylaldehyde (Sigma-Aldrich), benzaldehyde (Merck),
3-chlorobenzaldehyde (Riedel de Haen), p-tolualdehyde (Koch Light
Laboratories), 4-nitrobenzaldehyde (Merck), 3-nitrobenzaldehyde
(Merck), 4-methoxybenzaldehyde (Fluka), piperonal (Fluka)
and salicylamide (Fluka) were acquired commercially and
used without further purification. 4–Ethoxybenzaldehyde26
and the 2-alkoxysalicylamides27,28 were obtained by reacting
4-hydroxybenzaldehyde and salicylamide, respectively, with the
appropriate alkyl halide (i, NaOH, DMSO; ii, alkylbromide or iodide).
Benzamide, 3-chlorobenzamide and 4-nitrobenzamide were made by
hydrolysis of benzonitrile, 3-chlorobenzonitrile and 4-nitrobenzonitrile,
respectively (i, conc. H2SO4; ii, neutralisation with Na2CO3). The
aldoximes were prepared from the corresponding aldehydes by reaction
with hydroxylamine hydrochloride (NH2OH·HCl) in a mixture of
ethanol and water. Solely in the preparation of 9-anthranylcarboxime
was sodium carbonate (Na2CO3, 2 mol equiv.) added to the reaction
mixture, as the unbuffered reaction of 9-anthranylaldehyde with
NH2OH·HCL produced 9-cyanoanthracene (13% yield) in addition to
9-anthranylcarboxime.
Once more, we investigated whether in this transformation
triphenylphosphine can take the place of triethylamine as
Brønsted base and formal acceptor of the hydrogen halide
formed. This replacement leads to slightly higher yields in the
benzonitriles. Also, the work-up is simplified by obviating the
aqueous extraction of the reaction mixture. After evaporation
of the dichloromethane, the reaction mixture is subjected
directly to an easy column chromatographic separation.
However, again 2-alkoxy-substituted substrates such as
2,5-dimethoxybenzaldoxime (4h) do not give satisfactory
yields, under these conditions.
In summary, it was found that the environmentally more
acceptable BrCCl3 can replace CCl4 in the Appel-type
dehydration of benzamides and of benzaldoximes, to provide
benzonitriles. Both transformations can be carried out with
BrCCl3–PPh3–Et3N and with BrCCl3–(2 equiv.)PPh3. The
yields of the dehydration of benzaldoximes to benzonitriles
are higher with BrCCl3–(2 equiv.)PPh3 for those molecules
examined, except for the 2-alkoxy derivatives, where both
2-alkoxybenzamides and 2-alkoxybenzaldoximes give better
yields with BrCCl3–PPh3–Et3N.
3-Chlorobenzonitrile (2i); typical procedure
A
to prepare
benzonitriles from benzamides: BrCCl3 (900 mg, 4.6 mmol) was added
to PPh3 (1.22 g, 4.6 mmol) in dry CH2Cl2 (12 mL) and the resulting
mixture was stirred at room temperature for 20 min, during which
time the solution turned from yellow to red-brownish in colour.
Thereafter, 3-chlorobenzamide (1i, 500 mg, 3.2 mmol) was added. The
reaction mixture was heated under reflux for 25 min. Then, dry Et3N
(465 mg, 4.6 mmol) was added dropwise with a syringe over 1 min.
The reaction mixture was heated under reflux for 12 h. Thereafter,
it was cooled to room temperature and added to cold water (50 mL).
The mixture was extracted with dichloromethane (2×30 mL) and
chloroform (30 mL). The combined organic phases were dried over
anhydrous MgSO4, concentrated under reduced pressure and subjected
to column chromatography on silica gel (CH2Cl2/hexane 4:1) to give
3-chlorobenzonitrile (2i, 320 mg, 72%) as a colourless solid; m.p. 40°C
(lit.29 38–40 °C); νmax (KBr/cm–1) 3025, 3018, 2234 (CN), 1560, 1470,
1416, 1271, 1196, 1086, 878, 845, 793, 674, 579, 450; δH (400 MHz,
Experimental
Melting points were measured on a Stuart SMP 10 melting point
apparatus and are uncorrected. IR spectra were measured with a
Thermo/Nicolet Nexus 470 FT-IR ESP Spectrometer. 1H and 13C NMR
spectra were recorded with a Varian 400 NMR (1H at 395.7 MHz,
13C at 100.5 MHz) and a Varian 200 MHz NMR spectrometer (1H at
200.0 MHz, 13C at 50.3 MHz). The chemical shifts are relative to TMS
(solvent CDCl3, unless otherwise noted). Mass spectra were measured
with a JMS-01-SG-2 spectrometer. CHN-analysis was performed
on a LECO TruSpec Micro instrument. Column chromatography
was carried out on silica gel (60 A, 230–400 mesh, Sigma-Aldrich).
Triethylamine was dried over solid KOH and distilled.
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JOURNAL OF CHEMICAL RESEARCH 2014 83
CDCl3) 7.42 (1H, dd, 3J=8.0 Hz, 3J=8.0 Hz), 7.54–7.59 (2H, m), 7.63 (dd,
4J=2.0 Hz, 4J= 1.6 H z); δC (100.5 MHz, CDCl3) 113.9 (Cquat), 117.4 (Cquat),
130.3 (CH), 130.5 (CH), 131.9 (CH), 133.2 (CH), 135.2 (Cquat); MS (EI,
70 eV) m/z (%) 139 (37ClM+, 32), 137 (35ClM+, 100).
OCH2), 6.95–6.99 (2H, m), 7.50–7.55 (3H, m); δC (100.5 MHz, CDCl3)
14.7 (CH3), 64.5 (OCH2), 101.8 (Cquat), 112.3 (CH), 116.5 (Cquat), 120.7
(CH), 133.7 (CH), 134.4 (CH), 160.7 (Cquat); MS (EI, 70 eV) m/z (%) 147
(M+, 100).
3,4-Dimethoxybenzonitrile (2q); typical procedure B to prepare
benzonitriles from benzaldoximes: BrCCl3 (940 mg, 4.8 mmol) was
added to PPh3 (1.26 g, 4.8 mmol) in dry CH2Cl2 (14 mL). The resulting
mixture was stirred at room temperature for 20 min, during which time
the solution turned from yellow to red–brownish in colour. Thereafter,
3,4-dimethoxybenzaldoxime (4i, 800 mg, 4.4 mmol) was added. The
reaction mixture was heated under reflux for 25 min. Then, dry Et3N
(485 mg, 4.8 mmol) was added dropwise with a syringe over 1 min.
The reaction mixture was heated under reflux for 8 h. Thereafter, it
was cooled to room temperature and added to cold water (50 mL).
The mixture was extracted with dichloromethane (2×30 mL) and
chloroform (30 mL). The combined organic phases were dried over
anhydrous MgSO4, concentrated under reduced pressure and subjected
to column chromatography on silica gel (CH2Cl2/hexane 4:1) to give
3,4-dimethoxybenzonitrile (2q, 665 mg, 92%) as a colourless solid; m.p.
69–70 °C (lit.29 68–70 °C); vmax (KBr/cm–1) 3085, 3001, 2838, 2224 (CN),
1598, 1583, 1413, 1335, 1271, 1246, 1138, 1018, 929, 877, 812, 766, 617; δH
(400 MHz, CDCl3) 3.89 (3H, s, OCH3), 3.92 (3H, s, OCH3), 6.90 (1H, d,
3J=8.4 Hz), 7.11 (1H, s), 7.29 (1H, d, 3J= 8.4 H z); δC (100.5 MHz, CDCl3)
56.0 (OCH3), 56.1 (OCH3), 103.9 (CN), 111.2 (CH), 113.9 (CH), 119.2
(Cquat), 126.5 (CH), 149.1 (Cquat), 152.8 (Cquat); MS (EI, 70 eV) m/z (%) 163
(M+, 100), 120 (21), 77 (21).
2-Propoxybenzonitrile (2c, procedure A): Colourless oil; vmax (KBr/cm–1)
3079, 2968, 2880, 2227 (CN), 1597, 1489, 1393, 1261, 1166, 1113, 1062,
974, 838, 754, 499; δH (400 MHz, CDCl3) 1.06 (3H, t, 3J=7.6 Hz, CH3),
3
3
3
1.87 (2H, dt, J=7.6 Hz, J=6.4 Hz), 4.02 (2H, t, J=6.4 Hz, OCH2),
6.94–6.96 (3H, m), 7.47–7.54 (2H, m); δC (100.5 MHz, CDCl3) 10.4 (CH3),
22.3 (CH2), 70.4 (OCH2), 101.9 (CN, Cquat), 112.2 (CH), 116.6 (Cquat), 120.5
(CH), 133.7 (CH), 134.3 (CH), 160.8 (Cquat). Anal. calcd for C10H11NO
(161.20): C, 74.51; H, 6.88; N, 8.69; found: C, 74.32; H, 6.95; N, 8.26%.
2-Butoxybenzonitrile (2d, procedure A): Colourless oil; vmax (KBr/cm–1)
2872, 2226 (CN), 1601, 1581, 1497, 1250, 1166, 1109, 1064, 969, 747; δH
(400 MHz, CDCl3) 0.97 (3H, t, 3J=7.0 Hz, CH3), 1.48–1.57 (2H, m), 1.79–
1.86 (2H, m), 4.06 (2H, t, 3J=6.4 Hz, OCH2), 6.93–6.99 (3H, m), 7.47–
7.54 (2H, m); δC (100.5 MHz, CDCl3) 13.8 (CH3), 19.1 (CH2), 30.9 (CH2),
68.7 (OCH2), 101.9 (CN, Cquat), 112.1 (CH), 116.6 (Cquat), 120.5 (CH), 133.8
(CH), 134.3 (CH), 160.8 (Cquat). Anal. calcd for C11H13NO (175.22): C,
75.40; H, 7.48; N 7.99; found: C, 75.25; H, 7.52; N, 7.27%.
2-Pentoxybenzonitrile (2e, procedure A): Colourless oil; vmax (KBr/
cm–1) 2957, 2873, 2227 (CN), 1598, 1493, 1451, 1290, 1260, 1165, 1110,
756; δH (400 MHz, CDCl3) 0.92 (3H, t, 3J=7.2 Hz, CH3), 1.33–1.44 (2H,
m), 1.44–1.50 (2H, m), 1.80–1.87 (2H, m), 4.05 (2H, t, 3J=6.4 Hz, OCH2),
6.92–6.97 (2H, m), 7.47–7.54 (2H, m); δC (100.5 MHz, CDCl3) 14.0 (CH3),
22.4 (CH2), 28.0 (CH2), 28.6 (CH2), 69.0 (OCH2), 101.9 (Cquat), 112.1 (CH),
116.6 (Cquat), 120.5 (CH), 133.8 (CH), 134.3 (CH), 160.8 (Cquat). Anal.
calcd for C12H15NO (189.25): C, 76.16; H, 7.99; N, 7.40; found: C, 76.29;
H, 8.09; N, 6.86%.
2-Octoxybenzonitrile (2f, procedure A): Colourless oil; vmax (KBr/cm–1)
3079, 2928, 2856, 2228 (CN), 1598, 1494, 1451, 1289, 1261, 1165, 1110,
1043, 756; δH (400 MHz, CDCl3) 0.87 (3H, t, 3J=6.4 Hz, CH3), 1.27–1.31
(8H, m), 1.46–1.48 (2H, m), 1.82–1.85 (2H, m), 4.05 (2H, t, 3J=6.4 Hz,
OCH2), 6.92–6.96 (2H, m), 7.49–7.54 (2H, m); δC (100.5 MHz, CDCl3)
14.1 (CH3), 22.7 (CH2), 25.9 (CH2), 28.9 (CH2), 29.2 (CH2), 29.3 (CH2),
31.8 (CH2), 69.0 (OCH2), 101.9 (Cquat), 112.1 (CH), 116.6 (Cquat), 120.5
(CH), 133.8 (CH), 134.3 (CH), 160.8 (Cquat). Anal. calcd for C15H21NO
(231.33): C, 77.88; H, 9.15; N, 6.05; found: C, 77.92; H, 9.18; N, 5.53%.
2-Allyloxybenzonitrile (2g, procedure A): Colourless oil; vmax (KBr/cm–1)
3082, 3023, 2990, 2927, 2873, 2227 (CN), 1599, 1580, 1492, 1450, 1425,
1290, 1270, 1235, 1166, 1111, 1044, 995, 934, 839, 755, 497; δH (400 MHz,
CDCl3) 4.64–4.66 (2H, m, OCH2). 5.30–5.34 (1H, m), 5.44–5.49 (1H, m),
5.98–6.08 (1H, m), 6.93–7.01 (2H, m), 7.47–7.56 (2H, m); δC (100.5 MHz,
CDCl3) 69.4 (OCH2), 102.1 (Cquat), 112.6 (CH), 116.5 (Cquat), 118.3 (CH2),
120.9 (CH), 131.8 (CH), 133.8 (CH), 134.2 (CH), 160.2 (Cquat); Anal. calcd
for C10H9NO (159.18): C, 75.45%; H, 5.70; N, 8.80; found: 75.42%; H,
5.85%; N, 8.67%.
Benzonitrile30 (2h, procedure A): Colourless oil; vmax (neat/cm–1) 2232
(CN), 1598, 1495, 1450, 772, 691, 650; δH (400 MHz, CDCl3) 7.46 (2H, dd,
3J=7.6 Hz, 3J=7.6 Hz), 7.60 (1H, dd, 3J=7.6 Hz, 3J=7.6 Hz), 7.64 (2H, d,
3J=7.6 Hz); δC (100.5 MHz, CDCl3) 112.4 (Cquat), 118.9 (Cquat), 129.1 (2C,
CH), 132.2 (2C, CH), 132.8 (CH); MS (EI, 70 eV) m/z (%) 103 (M+, 100),
76 (34).
4-Tolunitrile30 (2k, procedure B): Colourless oil; vmax (neat/cm–1) 2925,
2228 (CN), 1608, 1508, 817, 546; δH (400 MHz, CDCl3) 2.40 (3H, s, CH3),
7.25 (2H, d, 3J=7.6 Hz), 7.52 (2H, d, 3J= 7.6 H z); δC (100.5 MHz, CDCl3)
21.8 (CH3), 109.2 (Cquat), 119.2 (Cquat), 129.8 (2C, CH), 132.0 (2C, CH),
143.7 (Cquat); MS (EI, 70 eV) m/z (%) 117 (M+, 100), 90 (25).
4–Ethoxybenzonitrile (2v); typical procedure
C to prepare
benzonitriles from benzaldoximes with CBrCl3 and 2 equiv. PPh3:
BrCCl3 (650 mg, 3.3 mmol) was added to PPh3 (870 mg, 3.3 mmol) in dry
CH2Cl2 (10 mL). The resulting mixture was stirred at room temperature
for 20 min, during which time the solution turned from yellow to red–
brownish in colour. Thereafter, 4-ethoxybenzaldoxime (4n, 500 mg,
3.05 mmol) was added. The reaction mixture was heated under reflux
for 25 min. Then, triphenylphosphine (870 mg, 3.3 mmol) was added,
and the mixture was stirred for 8 h at reflux. The cooled reaction mixture
was concentrated under reduced pressure and subjected directly to
column chromatography on silica gel (CH2Cl2–hexane 5:1) to give 2v
as a colourless solid (404 mg, 90%); m.p. 64 °C (lit.29 62–64 °C); vmax
(KBr/cm–1) 2218 (CN), 1611, 1511, 1398, 1303, 1172, 1039, 844, 808,
706, 547; δH (400 MHz, CDCl3) 1.41 (3H, t, 3J=7.2 Hz, CH3), 4.05 (2H,
q, 3J=7.2 Hz, OCH2), 6.90 (2H, d, 3J=7.6 Hz), 7.54 (2H, d, 3J=7.6 Hz);
δC (100.5 MHz, CDCl3) 14.5 (CH3), 63.9 (OCH2), 103.6 (Cquat), 115.1 (2C,
CH), 119.3 (Cquat), 133.9 (2C, CH), 162.2 (Cquat); MS (EI, 70 eV) m/z (%)
147 (M+, 27), 119 (100).
4-Nitrobenzonitrile (2j); typical procedure D to prepare benzonitriles
from benzamides with CBrCl3 and 2 equiv. PPh3: BrCCl3 (230 mg,
1.15 mmol) was added to PPh3 (290 mg, 1.1 mmol) in dry CH2Cl2 (8 mL).
The resulting mixture was stirred at room temperature for 20 min,
during which time the solution turned from yellow to red–brownish
in colour. Thereafter, 4-nitrobenzamide (4n, 143 mg, 0.95 mmol) was
added. The reaction mixture was heated under reflux for 25 min. Then,
PPh3 (290 mg, 1.1 mmol) was added, and the mixture was stirred for 7 h
at reflux. The cooled reaction mixture was concentrated under reduced
pressure and subjected directly to column chromatography on silica
gel (CH2Cl2) to give 2j (130 mg, 92%) as a colourless solid, m.p. 149–
150 °C (lit.29 144–147 °C); vmax (KBr/cm–1) 2233 (CN), 1603, 1526, 1488,
1349, 1295, 1015, 860, 748, 683, 540; δH (400 MHz, CDCl3) 7.83 (2H, d,
3J=8.8 Hz), 8.30 (2H, d, 3J= 8.8 H z); δC (100.5 MHz, CDCl3) 115.8 (Cquat),
117.3 (Cquat), 123.3 (2C, CH), 132.5 (2C, CH), 149.0 (Cquat); MS (EI, 70 eV)
m/z (%) 148 (M+, 34), 102 (100).
3-Bromobenzonitrile (2L, procedure B): Pale yellow solid; m.p. 39–
40 °C (lit.29 38–40 °C); vmax (KBr/cm–1) 2231 (CN), 1560, 1478, 1408,
1189, 1076, 997, 913, 893, 783, 675, 439; δH (400 MHz, CDCl3) 7.35 (1H,
2-Methoxybenzonitrile30 (2a, procedure A): Colourless oil: vmax (KBr/cm–1)
3020, 2950, 2840, 2230 (CN), 1600, 1495, 1465, 1440, 1290, 1260, 1115,
1020, 760; δH (400 MHz, CDCl3) 3.92 (3H, s, OCH3), 6.98–7.02 (2H, m),
7.55–7.58 (3H, m); δC (100.5 MHz, CDCl3) 56.1 (OCH3), 101.6 (Cquat),
111.7 (CH), 116.6 (Cquat), 121.0 (CH), 133.8 (CH), 134.9 (CH), 162.3 (Cquat);
MS (EI, 70 eV) m/z (%) 133 (M+, 100), 104 (65), 90 (43).
3
3
3
dd, J=8.0 Hz, J=8.0 Hz), 7.59 (1H, dm, J=8.0 Hz), 7.73 (1H, dm,
3J=8.0 Hz), 7.78 (1H, bs); δC (100.5 MHz, CDCl3) 114.2 (Cquat), 117.3
(Cquat), 122.9 (Cquat), 130.6 (CH), 130.7 (CH), 134.8 (CH), 136.1 (CH); MS
(EI, 70 eV) m/z (%) 183 (81BrM+, 85), 181 (79BrM+, 87), 102 (100).
3-Fluorobenzonitrile30 (2m, procedure B): A colourless oil; vmax
(neat/cm–1) 3078, 2235 (CN), 1585, 1483, 1434, 1252, 1127, 929, 875,
793, 676; δH (400 MHz, CDCl3) 7.24–7.31 (2H, m), 7.40–7.42 (2H, m); δC
2–Ethoxybenzonitrile30 (2b, procedure A): Colourless oil; δH
(400 MHz, CDCl3) 1.47 (3H, t, 3J=7.0 Hz, CH3), 4.15 (2H, q, 3J=7.0 Hz,
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84 JOURNAL OF CHEMICAL RESEARCH 2014
(100.5 MHz, CDCl3) 113.9 (Cquat, 3JCF =9.0 Hz), 117.6 (Cquat, 4JCF =3.0 Hz),
119.2 (CH, JCF =24.7 Hz), 120.5 (CH, JCF =21.0 Hz), 128.2 (CH,
4JCF =3.7 Hz), 131.1 (CH, 3JCF =8.2 Hz), 162.2 (Cquat, 1JCF =249.8 Hz); MS
(EI, 70 eV) m/z (%) 121 (M+, 100), 94 (19).
This work was supported by SURE project fund 31S097. Ashraf
El-Khwass is a visiting student at UAEU.
2
2
Received 15 September 2013; accepted 6 December 2013
Paper 1302181 doi: 10.3184/174751914X13891131118347
Published online: 5 February 2014
4-Methoxybenzonitrile (2n, procedure B): Pale yellow solid, m.p. 55 °C
(lit.29 57–59 °C); vmax (KBr/cm–1) 2977, 2843, 2218 (CN), 1605, 1509,
1306, 1258, 1176, 1023, 829, 682, 546; δH (400 MHz, CDCl3) 3.85 (3H, s,
OCH3), 6.94 (2H, d, 3J=8.8 Hz), 7.57 (2H, d, 3J= 8.8 H z); δC (100.5 MHz,
CDCl3) 55.5 (OCH3), 103.9 (Cquat), 114.7 (2C, CH), 119.2 (Cquat), 134.0 (2C,
CH), 162.8 (Cquat); MS (EI, 70 eV) m/z (%) 133 (M+, 100), 103 (37), 90 (43).
2-Nitrobenzonitrile (2o, procedure B): Colourless solid; m.p. 114–
115 °C (lit.29 107–109°C); vmax (KBr/cm–1) 3112, 2232 (CN), 1613, 1533,
1201, 1150, 968, 859, 792, 743, 684, 662, 550; δH (400 MHz, CDCl3)
7.83–7.85 (2H, m), 7.92–7.93 (1H, m), 8.33–8.35 (1H, m); δC (100.5 MHz,
CDCl3) 108.1 (Cquat), 114.9 (Cquat), 125.6 (CH), 133.7 (CH), 134.3 (CH),
135.6 (CH), 148.5 (Cquat); MS (EI, 70 eV) m/z (%) 148 (M+, 55), 102 (100).
Anal. calcd for C7H4N2O2 (148.19): C, 56.76; H, 2.72; N, 18.91; found: C,
56.55; H, 2.89; N, 18.80%.
2,5-Dimethoxybenzonitrile31 (2p, procedure B): Colourless needles;
m.p. 87–88 °C (lit.29 81–85 °C); vmax (KBr/cm–1) 2224 (CN), 1582, 1508,
1420, 1287, 1237, 1120, 1039, 879, 815, 753, 704, 488; δH (400 MHz,
CDCl3) 3.77 (3H, s, OCH3), 6.89 (1H, d, 3J=8.8 Hz), 7.04 (1H, d,
4J=2.8 Hz), 7.07 (1H, dd, 3J=8.8 Hz, 4J= 2.8 H z); δC (100.5 MHz, CDCl3)
55.9 (OCH3), 56.4 (OCH3), 101.7 (Cquat), 112.6 (CH), 116.4 (Cquat), 117.5
(CH), 120.8 (CH), 153.1 (Cquat), 153.7 (Cquat); MS (EI, 70 eV) m/z (%) 163
(M+, 100).
References
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4-N,N-Dimethylaminobenzonitrile (2r, procedure B): Pale yellow
solid; m.p. 76 °C (lit.29 72–75 °C); vmax (KBr/cm–1) 2212 (CN), 1608, 1526,
1447, 1372, 1226, 1180, 1023, 1066, 942, 818, 546; δH (400 MHz, CDCl3)
3.02 (6H, s, 2 CH3), 6.62 (2H, d, 3J=9.2 Hz), 7.45 (2H, d, 3J= 9.2 H z); δC
(100.5 MHz, CDCl3) 39.9 (2C, 2 CH3), 97.3 (Cquat), 111.4 (2C, CH), 120.8
(Cquat), 133.4 (2C, CH), 152.4 (Cquat); MS (EI) m/z (%) 146 (MH+, 21), 145
(M+, 100).
17 S. Zhou, D. Addis, S. Das, K. Junge and M. Beller, Chem. Commun., 2009,
4883.
Anthranyl-9-carbonitrile (2s, procedure B): Yellow solid; m.p. 174–
175 °C; (lit.29 173–177 °C); vmax (KBr/cm–1) 2213 (CN), 1445, 1263, 898,
846, 780, 730, 613, 551, 442; δH (400 MHz, CDCl3) 7.49–7.53 (2H, m),
7.62–7.66 (2H, m), 7.98–8.00 (2H, m), 8.32–8.35 (2H, m), 8.59 (1H, s); δC
(100.5 MHz, CDCl3) 105.4, 117.3, 125.3, 126.4, 129.0, 130.7, 132.8, 133.3;
MS (EI, 70 eV) m/z (%) 203 (M+, 100).
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22 K. Yamaguchi, H. Fujiwara, Y. Ogasawara and M. Kotani, Angew. Chem.
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27 Y. Al Jasem, B. al Hindawi, T. Thiemann and F. White, Acta Cryst., Sect.
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28 B. Bugenhagen, Y. Al Jasem, F. Barkhad, B. al Hindawi and T. Thiemann,
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29 Aldrich Advancing Science Catalog 2005–2006.
30 T. Yamaji, T. Saito, K. Hayamizu, M. Yanagisawa, O. Yamamoto, N.
Wasada, K. Someno, S. Kinugasa, K. Tanabe, T. Tamura and J. Hiraishi,
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Cinnamonitrile30 (2t, procedure B): Pale yellow oil; vmax (neat/cm–1)
3062, 2217 (CN), 1621, 1577, 1494, 1448, 1271, 1208, 967, 749, 689, 624,
534; δH (400 MHz, CDCl3) 5.87 (1H, d, 3J=16.0 Hz), 7.37–7.45 (5H, m),
7.42 (1H, d, 3J=16.0 Hz); δC (100.5 MHz, CDCl3) 96.3 (CH), 118.2 (Cquat
,
CN), 127.4 (2C, CH), 129.1 (2C, CH), 131.2 (CH), 133.5 (Cquat), 150.6
(CH); MS (EI, 70 eV) m/z (%) 129 (M+, 100), 102 (18).
3,4-Dioxomethylenebenzonitrile (2u, procedure C): Colourless solid;
m.p. 93–94 °C (lit.29 91–93 °C); vmax (KBr/cm–1) 2223 (CN), 1619, 1604,
1444, 1259, 1033, 863, 813, 612, 485; δH (200 MHz, CDCl3) 6.07 (2H, s),
6.86 (1H, d, 3J=8.2 Hz), 7.03 (1H, d, 4J=1.6 Hz), 7.21 (1H, dd, 3J=8.2 Hz,
4J=1.6 Hz); (100.5 MHz, CDCl3) 102.2 (OCH2O), 104.9 (Cquat), 109.1
(CH), 111.4 (CH), 118.9 (Cquat), 128.2 (CH), 148.0 (Cquat), 151.5 (Cquat); MS
(EI, 70 eV) m/z (%) 147 (M+, 75).
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