Differences between the Reaction of 2-Benzylidenecyclopentanone with
Malononitrile and the Reaction of Cyclopentylidenemalononitrile with
Aromatic Aldehydes; Synthesis of Strong Fluorescent o-Aminonitriles
Julian Mirek* and Piotr Milart
D epartm ent of Organic Chem istry, Jagiellonian University, Karasia 3, 30060 Krakow, Poland
Z. Naturforsch. 41b, 1471 —1478 (1986); received June 5, 1986
2-Benzylidenecyclopentanone, C yclopentylidenem alononitrile, o-A m inonitriles,
Luminescent Spectra
It was found that instead of the Knoevenagel condensation of cyclopentylidenemalononitrile
with arom atic aldehydes, a complex reaction takes place leading to 5,7-dicyano-l-arylidene-4arylindanes. The same com pounds were form ed in the reaction of the cyclopentylidenem alono­
nitrile dimer with aldehydes. It is suggested that the cyclopentylidenem alononitrile dimers un­
dergo an electrocyclic ring opening leading to conjugated triene systems. These species are very
reactive interm ediates and may react with aldehydes in the next step. Bulky substituents in
2,5-dibenzylidenecyclopentanone hindered its Knoevenagel condensation with malononitrile
but did not hinder its Michael addition leading to a 4H -pyrane derivative. Solutions of the
obtained o-aminonitriles exhibit strong fluorescence in a variety of solvents.
T he reaction course of the a,/3-unsaturated
ketones with malononitrile depends on the catalyst
used and the structure of the ketone. A Michael a d ­
duct was form ed in the reaction of benzylideneacetop hen one with malononitrile catalyzed by basic
aluminium oxide [1]. This adduct undergoes the
D im roth rearrangem ent in the presence of sodium
ethoxide leading to 3-cyano-2-ethoxypyridine [2].
Similar rearrangem ent can be p erform ed w ithout iso­
lation of the adduct; as an example may serve the
reaction of 2 -benzylidene-l-tetralone with m a lo n o ­
nitrile in the presence of sodium alcoxides giving a p ­
propriate derivatives of 3-cyano-2-alcoxypyridine
[3]. W hen the reaction of a,/3-unsaturated ketones
with malononitrile is conducted in ethanol or b e n ­
zene in the presence of am m onium acetate, the
Michael adducts formed in the beginning cyclize su b ­
sequently to 2-amino-3-cyanopyridines [4], Similar
reaction of chalcones with an excess of m alononitrile
in the presence of piperidine gave usually a mixture
of com pounds [5]. H ow ever, a,/?-unsaturated
ketones hea te d to reflux with malononitrile and a m ­
m onium acetate-acetic acid catalyst un d er a D eanStark trap give Knoevenagel condensation products
exclusively. This m ethod was used to obtain ylidenem alononitriles from 2 -cyclohexylidenecyclohexanone [6 ], 2-cyclopentylidenecyclopentanone [7] and
* Reprint requests to Prof. Dr. J. Mirek.
Verlag der Zeitschrift für Naturforschung, D -7400 Tübingen
03 4 0 -5 0 8 7 /8 6 /1 1 0 0 -1 4 7 1 /$ 01.00/0
mesityl oxide [8 ]. A pSim on et al. [9] investigating
intensively the reaction of malononitrile with a varie­
ty of a,/3-unsaturated ketones perform ed in D M F in
the presence of dry potassium fluoride have found
that the steric factors have a strong influence on the
ratio of the Michael to Knoevenagel products. W hen
the steric hindrance is located near the carbonyl
group, the Michael addition of malononitrile p r e ­
vails; in o th e r instances, the Knoevenagel condensa­
tion is preferred.
Results and Discussion
H eating u n d er reflux for several hours of 2-benzylide necyclopentanone ( 1 ) [ 1 0 ] with malononitrile and
a catalytical am o u n t of am m onium acetate-acetic
acid in b enzene with use of a D ean-S tark trap gave
( 2 -benzylidene)-cyclopentylidenemalononitrile
(2 )
(K n oevenagel condensation product) with a m o d e r ­
ate yield (Scheme 1).
T he m o d e ra te yield of 2 p rom pte d us to look for
an o th e r p ro ce d u re for its synthesis. We tried to apply
the C arrie [11] m e th o d which gave good result in the
condensation of benzaldehyde with 1 -phenylethylidenem alononitrile in the presence of piperidine.
H o w ev er, the use of cyclopentylidenemalononitrile
(3) [12] changed completely the reaction course. The
o bta in ed yellow product 4 a possesses properties dif­
ferent from those of 2. A lthough both com pounds, 2
and 4 a , show ed a CN ban d in their I R spectra, the
b an d of 2 ap p e a re d at 2200 c m - 1 and that of 4 a at
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1472
J. M irek—P. Milart ■Synthesis o f Strong Fluorescent o-A m inonitriles
NCV
‘Ph
Schem e
ch 2 (cn )2
TN
CH3 COONH4 -CH3 COOH, c 6 h 6
-H 20
1
1.
*
X
^
J - CH0 . CH2 (CN)2
h_ hzz 0
Schem e 2.
■
a:
x=h
b :x=ch3
2220 c m -1. Beside that, the I R spectrum of 4a
show ed additional three bands at 3 2 8 0 -3 5 0 0 c m - 1
which may be attributed to an am ino group. The
observed b an d system of 4a is typical for o-aminonitriles [13 —16]. Similar products were ob ta in ed
when oth e r aromatic aldehydes were used: 4b from
p-m ethylbenzaldehyde and 4 c from p-chlorobenzaldehyde. Mass spectra of 4 showed th at the
molecules contain the moieties of two molecules of
the aldehyde and possess three nitrogen atom s (ni­
trogen rule) w hat is in an accord with the e lem e nta ry
analytical data and the pro posed structure.
T he given structure suggests the complexity of the
reaction pathway of cyclopentylidenemalononitrile
with aldehydes. M ore detailed discussion of the
p roblem will be given later.
Synthesis of the “mixed dim ers” of cyclohexylidenem alononitrile and benzylidenemalononitrile
from the m ixture of k eton e, aldehyde and malononitrile carried in eth anol with the catalytical am ount
of piperidine is well known [13, 15]. By adoption of
this p ro ce d u re to the mixture containing cyclopenta n o n e instead of cyclohexanone we obtained the u n ­
know n “mixed dim ers” 5 (Scheme 2).
H o w ev er, the c o m poun d 5a yielded 4a when it
was h e a te d with benzaldehyde in D M F or aceto­
nitrile in the presence of a catalytical am ount of
piperidine. Similarly behaved 5b giving 4b in the
reaction with p-m ethylbenzaldehyde. This observa­
tion suggests that 5 a or oth e r “mixed d im e r” 5
should give a mixture of products 4 in the reaction
with o th e r aldehydes. Ind eed , presence of four
different co m pound s in the reaction mixture was
confirm ed by MS spectroscopy. F orm ation of the
mixture of com pounds 4 ( I —IV) may result from the
recyclization of 5 u n d er the conditions used.
It is well know n that cyclopentylidenemalono­
nitrile (3) [12, 17] undergo dimerization in the pres-
1473
J. M irek—P. Milart • Synthesis o f Strong Fluorescent o-Am inonitriles
ence of bases (Scheme 3). W e have found that dim er
react with aldehydes to give 4, so the dimerization
of cyclopentylidenem alononitrile may be considered
as the first step of the investigated reaction sequence.
6
NCX /CN
C
CN
CN
c&
base
3
Schem e 3.
T he ability of the m e n tio n e d “dim ers” to undergo
the electrocyclic ring opening to the reactive c o n ju ­
gated triene derivatives is described in the literature
[18]. It supports the discussed reaction mechanism
(Scheme 4). C o m p o u n d s 7 and 8 may be practically
tre a te d as the K noevenagel condensation products of
ylidenecyclopentanones with the malononitrile di­
m er (2-amino- 1,1,3-tricyanopropene) [19].
same is also very probable in our case. F u rth e rm o re ,
com poun ds 7 and 8 possess an active m ethylene
group which may u ndergo condensation with alde­
hydes rath e r easily. T h e aldehyde released from 7 in
the first reaction step can com pete with the aldehyde
added in the next step w hat leads to a mixture of 9.
A n electrocyclic reaction of 9 gave cyclic dienes 10
(Scheme 5).
Im m ediately after the cyclization, molecules of 10
undergo arom atization to indane derivatives (4). The
reaction is catalyzed by the present base and acceler­
ated by the high te m p e ra tu re used.
The “mixed d im e r” 5 a boiled with a few drops of
piperidine in D M F or acetonitrile gave yellowish
crystals of 11, 6-amino-5,7-dicyano-4-phenylindane,
which is very stable and do not change w hen boiled
with benzaldehyde u n d e r the sam e conditions
(Scheme 6 ).
5a
Q ,C H 3CNorDMF
- HCN
Schem e 6.
Schem e 4.
G ew ald [13] and S haranin [15] have pointed out
that an exchange of the carbonyl com ponents occur­
red in some instances of the T h o rp e cyclization. The
7
or
q
8
Schem e 5.
Q
♦ A r CHO
------------------—---------ArCHO or r \ = o
-
h2 o
H
Ar'
IArl
U nexpected results w ere obtained from the a ro ­
m atization of 5 b. Instead of the expected in dane d e ­
rivative of 11, co m p o u n d 4 b was o bta ined with a
poor yield. H e re , the elimination of H C N can p r o ­
ceed by an electrocyclic ring opening of the type
( 5 ^ 7 ) and an exchange of the benzylidene moiety at
the m ethylene fragm ent of the o p e n e d molecule. In
this reaction one molecule of 5 b is a source of the
benzylidene group for a n o th er molecule. C o m p o u n d
9 form ed in this reaction is transform ed then to 4b
according to the Schem e 5.
The a ttem p ted reaction of 1-indanone with ben z­
aldehyde and malononitrile carried in ethanol in the
presence of piperidine at room te m p e ra tu re was un-
J. M ir e k -P . Milart • Synthesis of Strong Fluorescent o-A m inonitriles
1474
NC\ r CN
'c - H
• V
A
.
C
nA
'2
f)
X
n
. W
H
- hcn
13
Scheme 7.
successful. A complex mixture of unidentified p ro d ­
ucts was o bta ined very quickly. H ow ever, the
T h o rp e cyclization of 1-indanylidenemalononitrile
(12) [20] with benzylidenem alononitrile (13) [21]
gave an yellowish crystalline product having the high
melting point. Its spectroscopical d ata and elemental
analysis correspon d very well with 3-amino-2,4-dicyano -l-phenylfluoren e (14) (Scheme 7).
T he reaction course is changed here a bit. The
p resent arom atic ring increased the tendency of the
molecule to adopt a p la n ar structure and facilitated
its arom atization at ro o m te m peratu re .
It a p p e ared that com po und 11 can be obtained
very easily from 2 -benzylidenecyclopentanone ( 1 )
and malononitrile w hen the reaction is carried in
eth anol in the presence of piperidine at room te m ­
perature. In this case, the raction course must be
different from that of 2-benzylidene-l-tetralone [3]
which gave a heterocyclic com pound. T he less h in­
dered molecule of 2 -benzylidenecyclopentanone
may react with two molecules of malononitrile
(K noevenagel condensation and Michael addition)
as was illustrated in Scheme 8 .
In o rd er to check this suggestion, a reaction of the
much m ore h inde re d molecule, 2,5-dibenzylidenecyclopentanone (15) [22], with malononitrile was
carried u n d e r the same reaction conditions. 4H -Pyrane derivative (16) was o b ta ined in good yield
(Scheme 9), although com p o u n d 4 a might be ex­
pected as the product in analogy to 11. H e re , the
Knoevenagel condensation was reta rd e d and the
Michael addition was facilitated.
A similar com pound was o b ta ined by H .-H . O tto
[23] from 2,6-dibenzylidenecyclohexanone.
For com parison, we have checked if the “mixed
dim er” derived from cyclohexanone, benzaldehyde
and malononitrile [13, 15] can react with benz ald e­
hyde. D espite of a variety of solvents and basic c a ta ­
lysts tried, only one well known p ro duct, 2 -am in o-l ,3dicyano-5,6,7,8-tetrahydronaphthalene [14, 15], was
always separated. H ow ever, a MS spectrum of the
crude prod uct showed its con tam ination (less than
5.0% ) by a derivative form ed in the condensation
with benzaldehyde but this was not se parate d in a
pure form. It seems to be interesting that such a small
difference in the structure of the starting materials
(five- or six-membered ring) can cause such dram atic
differences in their reactivities.
Solutions of com pounds 4 in a variety of organic
solvents show ed a very strong luminescence evoked
by daylight. The yellow solutions em ited blue-green
light. The absorption and emission spectra [24] of 4a
NCn ^CN
C
CN
H'^CN
-Ph
Ph
Schem e
8
.
11
J. M irek—P. Milart • Synthesis o f Strong Fluorescent o-A m inonitriles
Hs
I
1475
,H
>,ct y > h
15
Scheme 9.
4a
w ere ob ta in ed and are shown in Fig. 1, to give more
precise picture of that phenom enon.
A ccording to the molecular spectroscopy theory,
the absorption spectrum is, in the first ap pro xim a­
tion, a m irro r reflexion of the emission one and this
can be seen in Fig. 1. C om p o u n d 11 has strong blue
fluorescence evoked by the 365 nm wave length.
Experim ental
M elting points were determ ined in open capillary
tubes and are uncorrected. E lem ental analyses were
p erfo rm ed by the Regional L aboratory of PhysicoChemical A nalyses, Krakow. The IR spectra were
ob ta in ed on a IR-75 (Carl Zeiss Jena) spectrom eter in
nujol. T h e 'H N M R spectra were recorded on Tesla
BS-487 (80 M H z) and Tesla BS-567 A (100 M H z)
sp e ctrom e ters using C D C l, as solvent and TM S as
internal standard . The MS spectra were taken on
L K B -9000s and LKB-2091 instruments at 70 eV.
The absorption electronic spectra were recorded on a
U V /V IS (Carl Zeiss Jena) spectro p h o to m e te r in
0 . 1 cm silica transmission cells using spectrally pure
ethano l (c = 5 x l 0 - 4 mol/1). T he emission spectra
were ta k en on a sp ectro m eter constructed in the D e ­
p a rtm e n t of Physical Chemistry and E lectrochem is­
try, Jagiellonian University ( c = 1 0 ~ - mol/1, ethanol,
room te m p e ra tu re ). The used known ylidenecyclop en tanone s, ylidenem alononitriles and ylidenemalononitrile dimers were synthesized according to
the cited literature.
(2-B enzylidene)-cyclopentylidenem alononitriIe (2)
2-B enzylidenecyclopentanone (1) (3.4 g,
0.02 mol), m alononitrile (1.3 g, 0.02 mol), a m ­
m o nium acetate (0.3 g) and acetic acid (1.2 g) were
refluxed for 5 h in benzene (20 ml) under a D eanStark w ater separator. T h en , benzene was rem oved
un d er reduced pressure and the oily residue was di­
luted with ethanol ( 1 0 ml) and left for the next day in
1.0
0.5
0.0
28
26
IK
22
<10 ^ [ c m -1]
20
18
Fig. 1. A bsorption spectrum (-)
and fluorescent spectrum (.......... ) of
4a. Both spectra were norm alized ac­
cording to the maximum absorption or
emission.
1476
J. M irek—P. Milart • Synthesis o f Strong Fluorescent o-A m inonitriles
a refrigerator. The separated prod uct was recrystal­
lized from ethanol.
Yield 1.0 g (23% ); m.p. 1 1 9 - 1 2 0 °C.
1 .2 2 -1 .8 5 (m, 4 H , 2 x C H ,). - MS [m/z]: M + = 300
(34% ), 195 (12% ), 105 (100%).
C15H I2N 2 (220.29)
Caicd
Found
C 81.78
C 81.63
H 5.50
H 5.46
N 12.72,
N 12.59.
IR [ c m ' 1]: 2205 ( C = N ) , 1605, 1520 ( C = C ) . 'H N M R c3 [ppm]: 8.07 (t, 1 H , J = 4 H z, benzylidene proton), 7.45 (m, 5 H , aromatic protons),
2.95 (m, 4 H , 2 x C H 2), 1.92 (quintette, 2 H , J =
12 Hz, C H ,). - MS [m/z]: M + = 220 (100% ), 192
(64% ), 155 (25% ), 117 (23% ), 91 (25%).
3-A m in o -2 ,4 ,4-tricyano-5-arylbicy clo [4.3.0Jnona2,9-dienes (5) (or the m ixture o f tautom ers);
general procedure
T o a stirred mixture of cyclopentanone (8.4 g,
0.1 mol), malononitrile (13.2 g, 0.2 mol) and the
appropriate aldehyde (0.1 mol) in ethanol (400 ml)
was added piperidine ( 1 . 0 ml) at room te m p eratu re .
A fter 1—2 h, the white precipitate began to separate.
The precipitate was recrystallized from ethanol.
3-A m in o -2 ,4 ,4-tricyano-5 -phenylbicy clo [4.3.0Jnona2,9-diene (5 a)
Yield 16.8 g (59%); m.p. 1 9 5 - 1 9 6 °C.
CI8H ,4N 4 (286.36)
Caicd
C 75.49
Found C 75.28
H 4.94
H 4.86
N 19.57,
N 19.86.
IR [cm-1]: 3380, 3320, 3200 ( N H ,), 2190 ( C = N ) ,
1650 ( N H 2), 1580 ( C = C ) . - *H N M R (3 [ppm]: 7.40
(m, 5 H , aromatic protons), 5.80 (t, 1 H , J — 4 Hz,
= C —H ), 5.05 (s, 2 H , N H 2), 3.35 (m, 1 H , C H ), 3.08
(d, 1 H , J = 12 Hz, C H ), 1 .2 0 - 1 .8 0 (m, 4 H , 2 x
C H 2). - MS [m/z]: M + = 286 (36% ), 195 (45% ), 91
( 100%).
3 -A m ino-2,4,4-tricyano-5-(4'-m ethyl)phenylbicyclo[4.3.0]nona-2,9-diene (5 b)
Yield 18.6 g (62%); m.p. 2 2 4 - 2 2 5 °C.
C19H I6N 4 (300.39)
Caicd
C 75.96
Found C 75.72
H 5.38
H 5.27
N 18.66.
N 18.79.
IR [cm-1]: 3400, 3310, 3220 ( N H 2), 2200 ( C = N ) ,
1640 ( N H 2), 1580 ( C = C ) . - *H N M R (3 [ppm]: 7.30
(m, 4 H , aromatic protons), 5.80 (t, 1 H , J = 4 Hz,
= C —H ), 5.05 (s, 2 H , N H 2), 3.35 (m, 1H , C H ) , 3.08
(d, 1H , J = 11 H z, C H ), 2.35 (s, 3 H , C H 3),
6-A m in o -5 ,7 -dicyano-1 -arvlidene-4-arylindanes (4)
M eth o d A ; general procedure
T o a solution of cyclopentylidenemalononitrile (3)
( 2 . 6 g, 0 . 0 2 mol) or its dim er ( 2 . 6 g, 0 . 0 1 mol) and
the appropriate benzaldehyde (0.04 mol) in D M F
(10 ml) was ad d e d piperidine (0.5 ml) and the o b ­
tained mixture was refluxed for 1 h. Dilution of the
slightly cooled mixture with ethanol ( 1 0 ml) caused a
precipitation. T he obtained precipitate was recrystal­
lized from nitrom ethane.
6-A m in o -5 ,7-dicyano-1 -benzylidene4-phenylindane (4 a)
Yield 2.0 g (58% ) from cyclopentylidenem alono­
nitrile or 2 . 1 g (61%) from its dimer; m .p.
2 4 7 - 2 4 8 °C.
C24H I7N 3 (347.44)
Caicd
C 82.96
F ound C 82.78
H 4.94
H 4.90
N 12.10,
N 11.94.
IR [cm-1]: 3500, 3400, 3280 (N H ,), 2220 ( C = N ) ,
1650 ( N H 2), 1570 ( C = C ) . - 'H N M R d [ppm]: 7.85
(t, 1 H , J = 4 Hz, benzylidene proton), 7.35 (m,
1 0 H , arom atic protons), 5.20 (s, 2 H , N H 2), 3.05 (m,
2 H , C H 2), 2.75 (m, 2 H , C H ,). - MS [m/z]: M + =
347 (100% ), 256 (26% ), 91 (69% ). - U V /V IS Amax
[nm] absorption spectrum: 408 (f = 16400), em is­
sion spectrum: 465.
6-A m in o -5 ,7-dicyano-1 -(4 '-m ethyl)benzylidene4-(4"-m ethyl)phenylindane (4b)
Yield 2.4 g (64% ) from cyclopentylidenem alono­
nitrile or 2.6 g (70%) from its dimer; m.p.
2 3 9 - 2 4 0 °C.
C26H 2lN 3 (375.50)
Caicd
C 83.16
F ound C 83.02
H 5.65
H 5.51
N 11.19,
N 11.28.
IR [cm-1]: 3500, 3390, 3280 ( N H 2), 2220 ( C = N ) ,
1650 ( N H 2), 1570, 1510 ( C = C ) . - ‘H N M R (3 [ppm]:
7.80 (t, 1 H , J = 2 Hz, benzylidene proton), 7.25 (m,
8 H , aromatic protons), 5.22 (s, 2 H , N H ,), 3.05 (m,
2 H . C H ,), 2.80 (m, 2 H , C H ,), 2.43 (s, 3 H , C H ,),
2.38 (s, 3 H , C H ,). - MS [m/z]: M + = 375 (100% ),
105 (89% ). - U V /V IS Amax [nm] absorption spec­
trum: 411 (e = 18600). emission spectrum: 480.
1477
J. M ir e k -P . Milart • Synthesis o f Strong Fluorescent o-A m inonitriles
6 -A m in o -5 ,7 -d ic ya n o -l-(4 '-chloro) benzylidene4-(4"-chloro)phenylindane (4)
Yield 2.5 g (62% ) from cyclopentylidenemalononitrile or 2.7 g (67% ) from its dimer; m.p.
2 5 2 - 2 5 3 °C.
C24H I5N ,C l2 (416.32)
Calcd
C 69.23
F o u n d C 69.11
H 3.64
H 3.56
N 10.09,
N 9.90.
solution of malononitrile (2.6 g, 0.04 mol) in ethanol
(20 ml) and piperidine (1.0 ml). T he mixture was
stirred for 24 h. The obtained precipitate was sepa­
rated and recrystallized from nitro m ethane. All
physical properties of the obtained com pou nd were
identical with that obtained from M e th o d A.
Yield 1.5 g (29%).
3 -A m in o -2 ,4 -d icya n o -l-p h en ylflu o ren e (14)
IR [cm“ 1]: 3500, 3390, 3280 ( N H 2), 2220 ( C = N ) ,
1650 ( N H 2), 1600, 1580, 1560, 1500 ( C = C ) . 'H N M R <5 [ppm]: 7.85 (t, 1H , J = 4 Hz, benzylidene p ro to n ), 7.40 (m, 8 H , aromatic protons), 5.30
(s, 2 H , N H 2), 3.05 (m, 2 H , C H 2), 2.80 (m, 2 H ,
C H 2). - MS [m/z]: M + = 417 ( 6 8 % ), 416 (32%),
415 (100% ), 290 (22% ), 127 (28% ), 125 (83%). U V /V IS 2 max [nm] absorption spectrum: 408
(f = 15100), emission spectrum: 467.
A solution of 1-indanylidenemalononitrile (12)
(3.6 g, 0.02 mol), benzylidenem alononitrile (13)
(3.1 g, 0.02 mol) and piperidine (2.0 ml) in ethanol
(400 ml) was stirred for 48 h at room te m perature.
D uring this tim e, evolution of hydrogen cyanide was
observed and the solution turned blue-green. T hen,
half of the ethano l volume was rem oved by distilla­
tion and the obtain ed yellow precipitate was recrys­
tallized twice from nitro m ethane.
Yield 1.3 g (21% ); m.p. 3 0 3 - 3 0 5 °C.
M eth o d B; general procedure
C2IH 13N 3 (307.37)
Calcd
C 82.05
F ound C 82.16
T o a solution of the “mixed d im e r” 5 (0.01 mol) in
D M F (10 ml) was added the appropriate aldehyde
(0.01 mol) and piperidine (0.5 ml). F urther work up
as in the M e th o d A.
C o m p o u n d 4 a , yield 2.3 g ( 6 6 % ), com pound 4b ,
yield 2.6 g (70% ).
H 4.27
H 4.19
N 13.67,
N 13.84.
IR [cm“ 1]: 3500, 3400, 3280 ( N H 2), 2220 ( C = N ) ,
1640 ( N H 2), 1570 ( C = C ) . - ‘H N M R Ö [ppm]: 7.52
(m, 8 H , aromatic p rotons), 7,27 (s, 1H, aromatic
p ro to n ), 5.30 (s, 2 H , N H 2), 3.72 (s, 2 H , C H 2). - MS
[m/z]: M + = 307 (100% ), 306 (44% ), 230 (25%).
6-A m in o -5 ,7-dicyano-4-phenylindane (11)
2-A m ino-3-cyano-7-benzylidene-4-phenyl4 ,5 ,6 ,7-tetrahydro-4H -cyclopenta[b]pyrane (16)
M eth o d A
T o a solution of the com pound 5a (2.7 g,
0.01 mol) in D M F or acetonitrile (10 ml) was added
piperidine (0.5 ml) and the obtained mixture was re­
fluxed for 1 h. E thanol (10 ml) was added and the
mixture was left aside for crystallization. Recrystalli­
zation of the crude product from nitrom ethane gave
yellowish crystals.
Yield 1.8 g (74% ); m.p. 2 2 6 - 2 2 8 °C.
C17H 13N 3 (259.33)
Calcd
C 78.33
F o u n d C 78.33
H 5.06
H 5.12
N 16.21,
N 16.09.
IR [cm“ 1]: 3380, 3330, 3240 ( N H 2), 2205 ( C = N ) ,
1650 ( N H 2), 1560 ( C = C ) . - ‘H N M R Ö [ppm]: 7.40
(m, 5 H , arom atic protons), 5.10 (s, 2 H , N H 2), 3.10
(t, 2 H , 7 = 7 Hz, C H 2), 2.72 (t, 2 H , J = 7 Hz,
CH?), 2.15 (q uintette, 2 H , / = 7 Hz, CH?). — MS
[m/z]: M + = 259 (100% ), 258 ( 6 8 % ), 182 (19%). U V /V IS Amax [nm] absorption spectrum: 363
(e = 7700), emission spectrum: 417.
M eth o d B
T o a solution of 2-benzylidenecyclopentanone (1)
(3.4 g, 0.02 mol) in ethanol (30 ml) was added a
A suspension of 2,5-dibenzylidenecyclopentanone
(15) (2.6 g, 0.01 mol) in ethanol was stirred with
malononitrile (1.0 g, 0.015 mol) and piperidine
(1.0 ml), and refluxed for 3 h. D uring this time, the
colour and structure of the suspension was changed.
T he o b ta ined precipitate was recrystallized twice
from n itrom ethan e.
Yield 2.8 g ( 8 6 % ); m.p. 2 2 7 - 2 2 8 °C.
C22H 18N 20 (326.42)
Calcd
C 80.94
F ound C 80.88
H 5.57
H 5.50
N 8.58.
N 8.44.
IR [cm“ 1]: 3490, 3370, 3290, 3220 ( N H 2), 2200
( C = N ) , 1690 ( C = C ) , 1650 ( N H 2), 1590 ( C = C ) . ‘H N M R d [ppm]: 7.32 (m, 10 H , arom atic protons),
6.45 (t, 1 H , J = 4 Hz, benzylidene proton), 4.62 (s,
2 H , N H ,) , 4.25 (s, 1H , C H ) , 2.87 (m, 2 H , C H 2),
2.30 (m, 2 H , C H 2). - MS [m/z]: M + = 326 (79% ),
325 (11% ), 282 (29% ), 260 (50% ), 259 (79%),''249
(100% ), 235 ( 6 8 % ), 115 (7 9% ), 91 (60%).
T he auth ors w ould like to tha n k Doc. Dr. J. Najbar and Mr. M. Mac for their help in the m e asu re­
m ents and discussion of the emission spectra.
1478
J. M irek—P. Milart • Synthesis of Strong Fluorescent o-A m inonitriles
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