A new method for the synthesis of cinnamonitriles by catalytic olefination

Article abstract of DOI:10.1007/s11172-005-0245-0

Catalytic olefination of hydrazones of aromatic aldehydes with dibromoacetonitrile affords cinnamonitriles.

Full text of DOI:10.1007/s11172-005-0245-0

252
Russian Chemical Bulletin, International Edition, Vol. 54, No. 1, pp. 252—254, January, 2005
Brief Communications
A new method for the synthesis of cinnamonitriles
by catalytic olefination
V. G. Nenajdenko,aꢀ I. V. Golubinskii,a O. N. Lenkova,a A. V. Shastin,b and E. S. Balenkovaa
aDepartment of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (095) 932 8846. Eꢀmail: nen@acylium.chem.msu.ru
bInstitute of Problems of Chemical Physics, Russian Academy of Sciences,
142432 Chernogolovka, Moscow Region, Russian Federation.
Eꢀmail: shastin@icp.ac.ru
Catalytic olefination of hydrazones of aromatic aldehydes with dibromoacetonitrile affords
cinnamonitriles.
Key words: cinnamonitriles, dibromoacetonitrile, catalytic olefination, catalysis, copper
salts.
Earlier,1 we proposed a new copperꢀcatalyzed
ethylenediamine, 4ꢀchlorocinnamonitrile (1a) was obꢀ
tained in the highest yield (85%). According to GCꢀMS
data, the reaction mixture contained bromoacetonitrile
(reduction product of Br2CHCN) and the corresponding
symmetrical azine (1,4ꢀbis(4ꢀchlorophenyl)ꢀ2,3ꢀdiazaꢀ
butaꢀ1,3ꢀdiene); this suggests that the reaction follows
the previously proposed mechanism.2
Syntheses of hydrazones of aromatic aldehydes and
their subsequent reactions with Br2CHCN can be effected
as a "oneꢀpot" process. Nitriles 1a—g thus obtained were
mixtures of Eꢀ and Zꢀisomers (see Scheme 1).
olefination of hydrazones of carbonyl compounds with
polyhaloalkanes for the preparation of alkenes. Recently,2
we have found that trichloroacetonitrile reacts with
hydrazones to give αꢀchlorocinnamonitriles. The goal of
the present work was to further study the potential of
catalytic olefination of hydrazones of aromatic aldehydes.
Dibromoacetonitrile was used as an olefinating reagent.
The known syntheses of cinnamonitriles involve the
Wittig3 and Wittig—Horner4 reactions and condensation
reactions of aldehydes with cyanoacetic acid followed by
decarboxylation of the condensation products.5
The reaction of 4ꢀchloroacetophenone hydrazone with
Br2CHCN gave the symmetrical azine of 4ꢀchloroꢀ
acetophenone as the major product and 3ꢀ(4ꢀchloroꢀ
phenyl)ꢀ3ꢀmethylacrylonitrile in trace amounts. The use
We studied the effects of the solvent and the base in
the reaction of 4ꢀchlorobenzaldehyde hydrazone with
Br2CHCN (Scheme 1). In ethanol in the presence of
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 247—249, January, 2005.
1066ꢀ5285/05/5401ꢀ0252 © 2005 Springer Science+Business Media, Inc.

Synthesis of cinnamonitriles
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 1, January, 2005
253
Scheme 1
tion mixture was stirred until the starting aromatic aldehyde
was completely consumed (TLC). Then ethylenediamine
(1 mL, 15 mmol) and freshly purified CuCl (50 mg, 0.5 mmol)
were added to the resulting solution of hydrazone. Dibromoꢀ
acetonitrile (1.26 mL, 15 mmol) was added dropwise for 2 min,
the temperature being maintained at ~20 °C. The reaction
mixture was stirred for 6 h and neutralized with 0.1 M HCl
(200 mL). The reaction products were extracted with CH2Cl2
(3×50 mL), the combined extracts dried with Na2SO4, and
the reaction products isolated by column chromatography
in CH2Cl2.
4ꢀChlorocinnamonitrile (1a), yellow crystals, m.p. 85—86 °C
(cf. Ref. 6: m.p. 84—86 °C). Rf 0.62. 1H NMR (CDCl3), δ,
Eꢀisomer: 7.46—7.37 (m, 4 H, Harom); 7.36 (d, 1 H, ArCH=,
J = 16.4 Hz); 5.87 (d, 1 H, =CHCN, J = 16.4 Hz); Zꢀisomer:
7.75 (d, 2 H, Harom, J = 8.0 Hz); 7.45 (d, 2 H, Harom, J =
8.0 Hz); 7.08 (d, 1 H, J = 11.8 Hz); 5.48 (d, 1 H).
4ꢀMethoxycinnamonitrile (1b), yellow crystals, m.p.
61—64 °C (cf. Ref. 7: m.p. 62—63 °C). Rf 0.58. 1H NMR
(CDCl3), δ, Eꢀisomer: 7.37 (d, 2 H, Harom, J = 8.7 Hz); 7.30 (d,
1 H, J = 16.7 Hz); 6.89 (d, 2 H, Harom, J = 8.7 Hz); 5.69 (d,
1 H, J = 16.7 Hz); 3.83 (s, 3 H, Me); Zꢀisomer: 7.01 (d, 1 H, J =
12.0 Hz); 5.27 (d, 1 H, J = 12.0 Hz); 3.84 (s, 3 H, Me); the other
signals are masked by the signals of the major isomer.
Comꢀ
pound
Ar
Yield
(%)
E : Z
1a
1b
1c
1d
1e
1f
4ꢀClC6H4
4ꢀMeOC6H4
4ꢀMe2NC6H4
4ꢀNO2C6H4
2,4ꢀMe2C6H3
2ꢀNaphthyl
4ꢀBrC6H4
85
64
27
46
71
40
77
5 : 1
6 : 1
4 : 1
2.5 : 1
4.8 : 1
2 : 1
1g
5 : 1
of aqueous NH3, Et3N, or TMEDA instead of ethyleneꢀ
diamine did not increase the yield of the target product.
The results of these studies demonstrate that Br2CHCN
ensures generally higher yields of the products than does
CCl3CN2 and the reaction is significantly more stereoꢀ
selective. Apparently, this difference is due to steric facꢀ
tors. The reactions with Br2CHCN predominantly give
Eꢀnitriles, while unsaturated nitriles with cisꢀarrangement
of the cyano and aryl fragments are obtained by the reacꢀ
tions with CCl3CN.
It is worth noting that the described reactions of aroꢀ
matic aldehydes with Br2CHCN are the first example of
catalytic olefination yielding olefins containing no haloꢀ
gen at the double bond.
Thus, catalytic olefination affords cinnamonitriles
from aromatic aldehydes and dibromoacetonitrile. Mild
reaction conditions, accessible starting reagents, and the
possibility of varying substituents are its essential advanꢀ
tages over the known methods.
4ꢀ(N,NꢀDimethylamino)cinnamonitrile (1c), yellow crystals,
m.p. 154—156 °C (cf. Ref. 7: m.p. 158—160 °C). Rf 0.58.
1H NMR (CDCl3), δ, Eꢀisomer: 7.34 (d, 2 H, Harom, J = 9.1 Hz);
7.30 (d, 1 H, J = 17.6 Hz); 6.68 (d, 2 H, Harom, J = 9.1 Hz); 5.60
(d, 1 H, J = 17.6 Hz); 3.05 (s, 6 H, Me); Zꢀisomer: 7.78 (d, 2 H,
Harom, J = 9.1 Hz); 6.96 (d, 1 H, J = 12.1 Hz); 6.70 (d, 2 H,
Harom, J = 9.1 Hz); 5.11 (d, 1 H, J = 12.1 Hz); 3.06 (s, 6 H, Me).
4ꢀNitrocinnamonitrile (1d), yellow crystals, m.p. 200—201 °C
(cf. Ref. 6: m.p. 200—202 °C). Rf 0.54. 1H NMR (CDCl3), δ,
Eꢀisomer: 8.26 (d, 2 H, Harom, J = 8.8 Hz); 7.62 (d, 2 H, Harom
,
J = 8.8 Hz); 7.46 (d, 1 H, J = 16.7 Hz); 6.04 (d, 1 H); Zꢀisomer:
8.32 (d, 2 H, Harom, J = 8.5 Hz); 7.95 (d, 2 H, Harom, J =
8.5 Hz); 7.22 (d, 1 H, J = 12.0 Hz); 5.69 (d, 1 H, J = 12.0 Hz).
2,4ꢀDimethylcinnamonitrile (1e), a colorless oil. Rf 0.6.
1H NMR (CDCl3), δ, Eꢀisomer: 7.95 (d, 2 H, Harom, J = 8.2 Hz);
7.65 (d, 1 H, J = 16.7 Hz); 7.10—7.05 (m, 2 H, Harom); 5.74 (d,
2 H, J = 16.7 Hz); 2.51 (s, 3 H, Me); 2.35 (s, 3 H, Me);
Zꢀisomer: 5.44 (d, 1 H, J = 12.0 Hz); the other signals are
masked by the signals of the major isomer.
3ꢀ(2ꢀNaphthyl)acrylonitrile (1f), yellow crystals, m.p.
124—126 °C (cf. Ref. 8: m.p. 123—126 °C). Rf 0.6. 1H NMR
(CDCl3), δ, Eꢀisomer: 7.31—7.67 (m, 8 H, Harom and CH); 5.63
(d, 1 H, J = 16.0 Hz); Zꢀisomer: 5.39 (d, 1 H, J = 12.1 Hz); the
other signals are masked by the signals of the major isomer.
4ꢀBromocinnamonitrile (1g), yellow crystals, m.p.
104—105 °C (cf. Ref. 9: m.p. 106—107 °C). Rf 0.62. 1H NMR
(CDCl3), δ, Eꢀisomer: 7.53 (d, 2 H, Harom, J = 8.5 Hz); 7.32 (d,
1 H, J = 16.7 Hz); 7.30 (d, 2 H, Harom, J = 8.5 Hz); 5.87 (d, 1 H,
J = 16.7 Hz); Zꢀisomer: 7.06 (d, 1 H, J = 12.3 Hz); 5.48 (d, 1 H,
J = 12.3 Hz); the other signals are masked by the signals of the
major isomer.
Experimental
IR spectra were recorded on a URꢀ20 spectrophotometer
(thin film for liquids and Nujol for solids). 1H and 13C NMR
spectra were recorded on a Varian VXRꢀ400 spectrometer
(400 and 100 MHz, respectively) in CDCl3 with Me4Si as the
internal standard. TLC analysis was carried out on Merck 60
F
254 plates; Merck silica gel (63—200 mesh) was used for column
chromatography.
Synthesis of cinnamonitriles 1a—g (general procedure).
A solution of an aldehyde (5 mmol) in ethanol (10 mL)
was added dropwise to a stirred solution of hydrazine hyꢀ
drate (0.25 g, 0.24 mL, 5 mmol) in ethanol (5 mL). The reacꢀ
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 03ꢀ03ꢀ
32052a).

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Russ.Chem.Bull., Int.Ed., Vol. 54, No. 1, January, 2005
Nenajdenko et al.
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Received July 16, 2004;
in revised form October 7, 2004