342 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 342±343$
Organic Synthesis with Anion-exchange Resins:
Reaction of Imines with Active Methylene
Compounds$
Dilip Konwar,* Dilip Kumar Dutta and Birendra Nath Goswami
Regional Research Laboratory, Jorhat-785 006, Assam, India
Imines undergo addition±elimination reaction with active methylene compounds in the presence of Amberlite IRA-400
(OH ) as catalyst to yield arylidenemalononitrile derivatives.
Polymer-supported methods ®rst developed by Merri®eld1
in polypeptide synthesis have been utilised in many trans-
formations in organic chemistry.2 In recent years the
combinatorial chemistry has received much attention in
organic synthesis.3
Table 1 Synthesis of arylidenemalononitriles 3a±ja
Entry
R
R0
t/h
Yield (%)
1
2
3
Ph
p-ClC6H4
p-O2NC6H4
CN
CN
CN
5
4.5
4
82
80
75
Anion-exchange resins, particularly Amberlite IRA-400,
have been shown to be excellent catalysts in various organic
reactions, for example aldol condensation,4 Knovenagel
and Michael condensation,5 cyanohydrin formation,6 etc.
Recently, they have been in phenyl sul®de formation7 and
selective reduction of alkyl halides to alkanes.8 We report
here an addition±elimination reaction between imines and
active methylene compounds in the presence of Amberlite
IRA-400 (OH ) as catalyst to give synthetically useful
arylidenemalononitrile derivatives9 (Scheme 1).
4
CN
4.5
70
5
CN
5
65
6
7
Ph
Ph
CONH2
CN
4
5
79
82
8
CONH2
5
65
9
10
Ph-CH1CH
Ph
CO2Et
CO2Et
6
6
65
70
aAll the compounds gave satisfactory spectroscopic analyses and
were comparable with authentic samples.
vacuum desiccator for 24 h. before use. The imines were prepared
by the literature method10 or a slight modi®cation thereof.
Preparation of Arylidene Malononitrile 3a.ÐIn a typical exper-
iment, malononitrile (1.32 g, 0.02 mol) in ethanol (25 ml) was
mixed with Amberlite IRA-400 (OH ) (7.3 g, 0.02 mol) having a
capacity of 2.8 milliequvalent per dry g and benzylideneaniline 1a
(3.62 g, 0.02 mol) was stirred for 4 h at the re¯ux temperature
of ethanol. The reaction mixture was ®ltered through a pad of
Celite and the solvent evaporated under reduced pressure to give a
residue which on crystallation from light petroleum (bp 40±60 8C)
yielded arylidenemalononitrile 3a as white needles, mp 87 8C
(lit.,11 87 8C). Yield: 2.5 g (82%). The other nitriles were prepared
similarly.
Scheme 1
The reaction was carried out by stirring the imines 1a±j
and the active methylene compounds 2a±c in the presence of
a molar equivalent of Amberlite IRA-400 (OH ) in ethanol
under re¯ux. The product was obtained by simple ®ltration
evaporation of the solvent under reduced pressure and
crystallisation from appropriate solvents. The results are
summarized in Table 1.
In conclusion, we have observed that the anion-
exchange resin Amberlite IRA-400 (OH ) can rapidly
exchange its labile hydroxide ion with the enolate of the
active methylene compounds in ethanol solution producing
Amberlite IRA 400 (HCR0CN ) which reacts with the
azomethine carbon of the imines and eliminates amines in
solution. Work is in progress to understand the mechanism
of the reaction.
We wish to express our sincere thanks to Dr N.
Borthakur and Dr J. C. S. Kataky, scientists, and Dr J. S.
Sandhu, Acting Director, Regional Research Laboratory,
Jorhat for their keen interest and help in carrying out this
work.
Experimental
Received, 3rd February 1998; Accepted, 2nd March 1998
Paper E/8/00951A
The mps were measured in a Buchi apparatus and are un-
corrected. IR spectra were recorded on a Perkin-Elmer 237B spec-
trophotometer, 1H NMR spectra on a Varian T-60 spectrometer
with TMS as internal standard and mass spectra on an AEIMS-30
spectrometer The anion-exchange resin Amberlite IRA-400 was
usually purchased from Aldrich as the chloride salt (16±60 mesh).
This conversion into the hydroxide form was accomplished by
washing with 1 M sodium hydroxide until the eluent gave a negative
silver nitrate test for chloride ion. The resin was thoroughly washed
with distilled water, dried for several hours at 40 8C and kept in a
References
1 R. B. Merri®ed, J. Am. Chem. Soc., 1963, 85, 2194.
2 Organic Synthesis, Today and Tomorrow, ed. B. M. Trost and
C. R. Hutchison, Pergamon Press, Oxford, 1981, pp. 19±28 and
references therein.
3 J. S. Fruch and G. Jung, Angew. Chem, Int. Ed. Engl., 1936, 35,
2194.
4 G. V. Austerwell and R. Palloud, Bull. Soc. Chim. Fr., 1963, 678;
P. Mastagi, Z. Za®riadis, G. Durr, A. Floch and G. Lagrange,
Bull Soc. Chim. Fr. 1953, 693; M. H. Astle and J. A. Zaslowsky,
Bull Soc. Chim. Fr. 1952, 2867.
*To receive any correspondence.
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
5 B. W. Howk and C. M. Langkaminerer, U.S. Pat., 2 579 580,
25th December, 1951; E. D. Bergmann and R. Corret, J. Org.
Chem., 1956, 21, 107; 1958, 23, 1507.
Konwar, Dilip
