Reactions of tetracyanoethylene with N′-arylbenzamidines: A route to 2-phenyl-3 H -imidazo[4,5- b ]quinoline-9-carbonitriles

Article abstract of DOI:10.1021/jo4013699

Eight 2-phenyl-3H-imidazo[4,5-b]quinoline-9-carbonitriles 15 are prepared in four steps from N′-arylbenzamidines 11 and tetracyanoethylene (TCNE) in ～70-90% yields. The transformation involves the initial formation of N-aryl-N′-(1,2,2-tricyanovinyl)benzamidines 12 in 87-99% yields, which in MeCN undergo a 5-exodig cyclization to give the 2-[1-aryl-5-imino-2-phenyl-1H- imidazol-4(5H)-ylidene]malononitriles 13 in 84-92% yields, while in MeOH the (Z)-2-[2-phenyl-4-(arylimino)-1H-imidazol-5(4H)-ylidene]malononitriles 14 are formed in 85-94% yields. The imidazoles 14 can also be prepared directly from imidazoles 13 via a Dimroth rearrangement in either neat MeOH or in DCM with DBU. Subsequent thermolysis of imidazoles 14 in diphenyl ether affords 2-phenyl-3H-imidazo[4,5-b]quinoline-9-carbonitriles 15 in near quantitative yields. Mechanistic rationale is provided for all transformations.

Full text of DOI:10.1021/jo4013699

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Article
Reactions of tetracyanoethylene with N'-arylbenzamidines: A
route to 2 phenyl-3H-imidazo[4,5-b]quinoline-9-carbonitriles
Styliana I Mirallai, Maria Manoli, and Panayiotis A. Koutentis
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo4013699 • Publication Date (Web): 29 Jul 2013
Downloaded from http://pubs.acs.org on August 2, 2013
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Reactions of tetracyanoethylene with N'-arylbenzamidines: A route to 2-phenyl-
3
H-imidazo[4,5-b]quinoline-9-carbonitriles
Styliana I. Mirallai, Maria Manoli and Panayiotis A. Koutentis*
Department of Chemistry, University of Cyprus, P. O. Box 20537, 1678 Nicosia,
Cyprus, koutenti@ucy.ac.cy
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Eight 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitriles 15 are prepared in four
steps from N'ꢀarylbenzamidines 11 and tetracyanoethylene (TCNE) in ~70ꢀ90% yields.
The transformation involves the initial formation of NꢀarylꢀN'ꢀ(1,2,2ꢀtricyanovinyl)ꢀ
benzamidines 12 in 87ꢀ99% yields, which in MeCN undergo a 5ꢀexoꢀdig cyclization
to give the 2ꢀ[1ꢀarylꢀ5ꢀiminoꢀ2ꢀphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]malononitriles 13
in 84ꢀ92% yields, while in MeOH the (Z)ꢀ2ꢀ[2ꢀphenylꢀ4ꢀ(arylimino)ꢀ1Hꢀimidazolꢀ
5
(4H)ꢀylidene]malononitriles 14 are formed in 85ꢀ94% yields. The imidazoles 14 can
also be prepared directly from imidazoles 13 via a Dimroth rearrangement in either
neat MeOH or in DCM with DBU. Subsequent thermolysis of imidazoles 14 in
diphenyl ether affords 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitriles 15 in
near quantitative yields. Mechanistic rationale is provided for all transformations.
1
.
Introduction
1
,2
3
Tetracyanoethylene (TCNE) a cyanocarbon, is the simplest of the percyano
alkenes. It is highly electronꢀdeficient and strongly electrophilic. Not surprisingly,
TCNE can act as a powerful electron acceptor forming charge transfer complexes
4
,5
with various donors, or it can participate in pericyclic chemistry as an electron
4
6,7
deficient dienophile in DielsꢀAlder reactions or enophile in 2+2 cycloadditions.
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8
ꢀ10
Furthermore, it can act as an umpolung source of dicyanomethylene.
Its most
common reaction is that of addition to its double bond and subsequent loss of the
cyanide (tricyanovinylation). Direct addition to the nitrile can also occur but is less
11,12
7,13ꢀ19
common.
The chemistry of TCNE has been extensively reviewed.
0
1
2
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With primary or secondary aliphatic amines and with most primary and secondary
aromatic amines, the reaction with TCNE gives Nꢀtricyanovinylamines 1, although
13,20,21
with an excess of amine 1,1ꢀdiaminoꢀ2,2ꢀdicyanoethylenes 2
or 1,2ꢀdiaminoꢀ
22
1
,2ꢀdicyanoethylenes 3 are formed. TCNE does not react with tertiary aliphatic
amines, but it readily reacts with both tertiary and secondary aromatic amines,
attacking the arene to give 4ꢀtricyanovinylꢀarylamines 4 via the initial formation of a
21
1:1 π complex.
NC
NC
CN
CN
NC
NC
CN
NC
CN
NR2
R N
2
NR2
TCNE
1
4
2
R N
CN
NC
NC
CN
2
NC
NR2
NAr2
3
TCNE also reacts with a variety of bisꢀamino nucleophiles to give, after the initial
addition to the double bond, intramolecular cyclizations typically on the vicinal nitrile
that lead to various heterocyclic systems. For example, TCNE reacts with substituted
11,12,23
hydrazines to give pyrazoles 5 and/or 6,
or with 2ꢀamidines to give 2ꢀsubstituted
6ꢀaminopyrimidineꢀ4,5ꢀdicarbonitriles 7. The latter 6ꢀexoꢀdig cyclization is somewhat
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surprising since a 5ꢀexoꢀdig cyclization could in theory occur on the geminal nitrile to
yield five membered imidazoles of type 8 (Scheme 1).
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Scheme 1. Typical reaction products of TCNE with hydrazines and amidines.
To the best of our knowledge, only one report on the preparation of imidazolines from
TCNE has appeared whereby Nꢀmethylamino functionalization of the intermediate
tricyanovinylamine 9 led to a geminal (5ꢀexoꢀdig) heterocyclization to give 2ꢀ[5ꢀ
24
aminoꢀ2,3ꢀdihydroꢀ4Hꢀimidazolꢀ4ꢀylidene]malononitriles 10 (Scheme 2).
Scheme 2. Formation of imidazoles 10 from TCNE.
1
0,25ꢀ29
In light of this and our interest in preparing cyano substituted heteroarenes,
we
report below our complementary study on the reaction of TCNE with readily available
3
0
N'ꢀarylbenzamidines 11, which affords (Z)ꢀNꢀarylꢀN'ꢀ(1,2,2ꢀtricyanovinyl)benzaꢀ
midines 12 that readily undergo a 5ꢀexoꢀdig cyclization to the (imidazolylidene)ꢀ
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malononitriles 13, that in two steps, via the Dimroth rearrangement product 14, can be
converted into 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitriles 15 (Scheme 3).
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8
9
0
Scheme 3. Four step conversion of TCNE and benzamidines 11 into imidazo[4,5ꢀb]ꢀ
quinolines 15.
Previous syntheses of imidazo[4,5ꢀb]quinolines include the oneꢀpot Beckmann
31
rearrangement of 3ꢀacylꢀ2ꢀ(alkylamino)quinolinꢀ4ꢀ(1H)ꢀones,
the reductive
3
2,33
cyclization of 5ꢀ(2ꢀnitrobenzylidene)ꢀ3,5ꢀdihydroꢀimidazolꢀ4ꢀones,
from lithiated
34
35
3
ꢀaminoquinolines with nitriles,
and from 2,3ꢀdiaminoquinolines.
Several
35
imidazo[4,5ꢀb]quinolines behave as NO synthase inhibitors or as analogues of
36
antiviral polyhalogenated benzimidazole ribonucleosides, furthermore, fused 3Hꢀ
3
7
imidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitriles have been investigated as fluorescent dyes.
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2.
Results and Discussion
2.1.
Preparation of NꢀarylꢀN'ꢀ(1,2,2ꢀtricyanovinyl)benzamidines 12
The reaction of N'ꢀphenylbenzamidine 11a with TCNE was investigated in a variety
of solvents and temperatures and in almost all cases three products were observed in
varying ratios by TLC: a colorless, a yellow and an orange product 12a, 13a and 14a,
respectively. The order of formation was determined (by TLC) to be first the colorless,
then the yellow and finally the orange colored compound. It was noted that the
colorless product 12a converted rapidly into the yellow product 13a during a 2D TLC
study, furthermore, polar protic solvents such as MeOH or EtOH strongly promoted
the formation of the orange product 14a. Both mass spectrometry and elemental
analysis of these three products showed they were isomers with a molecular formula
10
11
12
13
14
15
16
17
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of C18
H
11
N
5
indicating that an addition between TCNE and N'ꢀphenylbenzamidine
1
1a followed by loss of HCN had occurred.
Since silica promoted the conversion of the colorless compound into the isomeric
yellow we pursued a non chromatographic work up to isolate a clean sample of the
colorless compound 12a: Treating N'ꢀphenylbenzamidine 11a with TCNE (1 equiv) in
o
dry THF at ca. 20 C led to the exclusive formation of the colorless compound 12a
(by TLC). By carefully evaporating the THF, redissolving the residue in a small
quantity of Et O and diluting with nꢀpentane we were able to precipitate a
2
microanalytically pure sample of the colorless product 12a in 97% yield. The
spectroscopic and analytical data (see Structure Elucidation Discussion for 12a in
Supporting Information) tentatively suggested the product to be NꢀphenylꢀN'ꢀ(1,2,2ꢀ
tricyanovinyl)benzamidine (12a), which could originate from simple substitution of
one nitrile by the least sterically hindered N'ꢀarylbenzamidine amino group. The
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5
5
6
reaction was general and in total nine analogues were prepared (Table 1).
Interestingly, where the benzamidines contained N'ꢀaryl substituents with either
chloro, bromo, iodo or nitro substituents (entries 5ꢀ9) the reactions required a slight
excess (1.2 equiv) of TCNE to come to completion.
0
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9
0
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2
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8
9
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9
0
Table 1 Reaction of TCNE with N'-arylbenzamidines 11.
NC
NC
CN
N
THF
r.t., 2 h
NC
NC
CN
CN
NH2
Ph
+
Ar
N
HN
Ar
Ph
TCNE
11
12
entries
TCNE
Ar
yields 12
(mmol)
(%)
1
2
3
4
5
6
7
8
9
1.0
1.0
1.0
1.0
1.2
1.2
1.2
1.2
1.2
Ph
12a (97)
12b (98)
12c (99)
12d (95)
12e (93)
12f (91)
12g (92)
12h (87)
12i (88)
6
4-MeOC H4
4-MeC H4
4-FC H4
4-ClC H4
3,4-Cl C H
4-BrC H4
4-IC H4
4-O NC H
6
6
6
2
6 3
6
6
2
6 4
2
.2.
Conversion of tricyanovinylbenzamidines 12 into imidazoles 13 and 14
o
Solutions of the tricyanovinylbenzamidine 12a in DMF or DMSO at ca. 20 C or
heated to reflux in a range of solvents such as DCM, PhMe or THF led to mixtures of
both yellow and orange products 13a and 14a, respectively. Furthermore, treatment
with either base (Hünig’s base or DBU) or acid catalysis (TsOH.H
2 2 4
O, H SO or
Lewis acids like AlCl , FeCl , ZnCl ) gave more complex mixtures. Fortunately,
3
3
2
simply heating a solution of the tricyanovinylbenzamidine 12a in dry acetonitrile led
to the formation of the yellow isomer 13a in 88% yield while in MeOH the orange
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isomer 14a was formed in 92% yield. These conversions were generally high yielding
for all nine analogues (Table 2).
Table 2 Conversion of tricyanovinylbenzamidines 12 into imidazoles 13 and
1
4.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
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NC
NC
CN
N
CN
Ar
N
MeCN
, 3 h
MeOH
, 1 h
N
N
N
NC
HN
Ph
Ph
NC
N
H
HN
Ar
Ph
Ar
CN
1
3
12
14
entries
Ar
yields 13
%)
yields 14
(
(%)
1
2
3
4
5
6
7
8
9
Ph
13a (88)
13b (89)
13c (89)
13d (89)
13e (87)
13f (87)
13g (85)
13h (84)
13i (92)
14a (92)
14b (91)
14c (94)
14d (88)
14e (86)
14f (90)
14g (87)
14h (85)
14i (93)
4-MeOC H4
6
4-MeC H4
6
4-FC H4
6
4-ClC H4
6
3,4-Cl C H
2
6 3
4-BrC H4
6
4-IC H4
6
4-O NC H
2
6 4
1
3
The C NMR spectroscopic data for both the yellow and orange isomers 13a and 14a,
respectively suggested one less nitrile group which indicated a cyclization had
occurred. As mentioned above, cyclizations to give either six membered pyrimidines
(
via a 6ꢀexoꢀdig cyclization) or five membered imidazoles (via a 5ꢀexoꢀdig) were
possible (Scheme 1), however, a study of the available spectroscopic data was
inconclusive (see Structure Elucidation Discussion for 13a and 14a in Supporting
Information). To identify these isomers we collected single crystal Xꢀray data, which
supported the yellow isomer to be 2ꢀ[5ꢀiminoꢀ1,2ꢀdiphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀ
ylidene]malononitrile (13a) (see Supporting Information, Figure S1) and the orange
isomer to be (Z)ꢀ2ꢀ[2ꢀphenylꢀ4ꢀ(phenylimino)ꢀ1Hꢀimidazolꢀ5(4H)ꢀylidene]malonoꢀ
nitrile (14a) (see Supporting Information, Figure S2).
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2
2
2
2
2
2
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4
4
4
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4
5
5
5
5
5
5
5
5
5
5
6
To study the chemistry of the imidazole 14a further, it was Nꢀmethylated using
methyl sulfate in dry THF. The products obtained were (Z)ꢀ2ꢀ[1ꢀmethylꢀ2ꢀphenylꢀ4ꢀ
(phenylimino)ꢀ1Hꢀimidazolꢀ5(4H)ꢀylidene]malononitrile (16) and (Z)ꢀ2ꢀ[1ꢀmethylꢀ2ꢀ
phenylꢀ5ꢀ(phenylimino)ꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]malononitrile (17) in 88 and 2%
0
1
2
3
4
5
6
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8
9
0
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3
4
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6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
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2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
yields, respectively (Scheme 4).
Scheme 4. N-Methylation of imidazole 14a.
1
13
Unlike the nonꢀmethylated imidazole 14a the H and C NMR spectra of both
methylated isomers were well resolved, showing the expected eight quaternary, six
3
CH and one CH carbon signals. The assigned regioselectivity for the methylation of
the major isomer 16 was determined by single crystal Xꢀray spectroscopy (see
1
Supporting Information, Figure S4), while 2DꢀNOESY H NMR spectroscopy was
used to support the assignment for the imidazole 17 (see Supporting Information).
The UV/vis spectra for the Nꢀmethylated imidazoles 16 and 17, which cannot suffer
from prototautomerism, showed only minor solvatochromic effects (see Supporting
Information, Figures S5 and S6).
Both the above imidazoles are examples of ortho quinone methide imines (QMI’s)
38
which typically are reactive species and not readily isolated. Not surprisingly, very
few examples of this ring system have been reported: 4ꢀMethyleneꢀ1Hꢀimidazolꢀ
5
(4H)ꢀimines 18 have been proposed as possible intermediates in the conversion of
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(Z)ꢀN ꢀ{1,2ꢀdicyanoꢀ2ꢀ[(N,Nꢀdimethylamino)methylamino]vinyl}formamidines
19
39
9
into purines or iminoꢀpyrroles, and as intermediates in the preparation of purineꢀN ꢀ
40
acetic acids from HCN and glycine. More recently, a series of prototautomerically
closely related 4ꢀiminoꢀ5ꢀmethyleneimidazolidinꢀ2ꢀones 20 have been isolated and
10
11
12
13
14
15
16
17
18
19
20
21
22
23
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60
4
1,42
1
characterized.
Interestingly, the H NMR in DMSOꢀd indicated the imine NH
6
was present as two broad singlets (δ
H
9.1ꢀ8.8 ppm) in a 1:1 ratio, which was attributed
1
to E/Z isomers of the exocyclic methylene (cf. the H NMR of imidazole 13a). To the
best of our knowledge, only one related Xꢀray structure has been reported, that of
(
E)ꢀ4ꢀ[5ꢀiminoꢀ1ꢀphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]ꢀ2,2ꢀdimethylꢀoxazolidinꢀ5ꢀ
43
imine (21).
H
N
N
N
CN
CN
R
N
H
HN
Me2N
N
18
19
NH
O
H
CN
Me
Me
H
N
R2
N
HN
N
H
N
N
O
N
R1
HN
Ph
20
21
2
.3. Dimroth rearrangement of imidazole 13 into imidazole 14
A close analysis of the two imidazoles 13a and 14a indicated that the latter was
probably the product of a Dimroth rearrangement of the former. Dimroth
44
rearrangements are typically thermally induced or initiated by acids or bases.
Nevertheless, a pure sample of the imidazole 13a dissolved in MeOH and left to stir at
o
ca. 20 C for 38 h was converted into the imidazole 14a in high yield. The reaction
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2
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5
5
6
time could be considerably shortened to 1 h by heating the reaction mixture to ca.
o
6
7 C. Furthermore, in a nonꢀprotic nonꢀnucleophilic solvent such as DCM heated to
o
ca. 40 C the conversion of imidazole 13a into imidazole 14a required the addition of
base with DBU (1 equiv) giving the best results (Table 3). When DBU was replaced
by pyridine, DMAP or lutidine or DABCO (1 equiv) the Dimroth rearrangement
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
could not be driven to completion, while the use of trialkylamines, such as Et
3
N (2ꢀ4
equiv) or Hünig’s base (iꢀPr NEt) led to no reaction. The reaction with DBU could
2
o
also be carried out at ca. 20 C but the reaction time increased to 22 h while the yield
decreased to 84ꢀ86%. Finally, reducing the equivalents of DBU led to incomplete
reactions (entry 1) while no significant advantage was observed in using more than
one equivalent (entry 3). Interestingly, the use of sterically hindered Barton’s base
also gave the imidazole 14a in 91% (entry 4).
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Table 3 Dimroth rearrangement of 2-(1-aryl-5-imino-2-phenyl-1H-
imidazol-4(5H)-ylidene)malononitriles 13 into (Z)-2-[4-(arylimino)-2-
phenyl-4-1H-imidazol-5(4H)-ylidene]malononitriles 14.
CN
Ar
N
A: MeOH, , 1 h
N
N
B: R N, DCM, , x h
N
NC
HN
3
Ph
Ph
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
NC
N
H
Ar
CN
13
entries Ar
14
cond. B
base (equiv), time (h)
yields 14 (%)
cond. A cond. B
1
2
3
Ph
Ph
Ph
Ph
DBU (0.5), 48
DBU (1), 4
DBU (2), 3
-
-
-
ira
14a (97)
14a (96)
b
4
Barton's base (1), 10 14a (99.6) 14a (91)
5
6
7
8
4-MeOC H4 DBU (1), 4
14b (99)
14c (94)
14d (98)
14e (98)
14f (96)
14g (94)
14h (95)
14i (95)
14b (90)
14c (91)
14d (92)
14e (92)
14f (93)
14g (88)
14h (91)
14i (95)
6
4-MeC H4
DBU (1), 4
DBU (1), 6
DBU (1), 6
DBU (1), 6
DBU (1), 6
DBU (1), 6
DBU (1), 6
6
4-FC H4
6
4-ClC H4
6
9
3,4-Cl C H
2
6 3
10
11
12
4-BrC H4
6
4-IC H4
6
4-O NC H
2
6 4
a
ir = incomplete reaction; b 2-tert-butyl-1,1,3,3-tetramethylguanidine.
The rearrangement was irreversible since treating (Z)ꢀ2ꢀ[2ꢀphenylꢀ4ꢀ(phenylimino)ꢀ
Hꢀimidazolꢀ5(4H)ꢀylidene]malononitrile (14a) with either NaOH (0.5 mol%) in
1
o
o
MeOH at ca. 67 C or with DBU (1 equiv) in dry DCM at ca. 40 C for 24 h led to no
reaction. The reaction presumably is initiated by nucleophilic attack by either
45
methanol/methoxide or even DBU, which can act as a nucleophile, at the imidazole
Cꢀ2 position which is strongly electrophilic, activated by both the exocyclic
ylidenemalononitrile and the imidazole imine which have constructively aligned
dipoles. Subsequent ring opening via cleavage of the imidazole N(1)–C(2) bond
affords a ring opened species that can rotate and undergo ring closure to afford the
new imidazole 14 (Scheme 5).
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1
1
1
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2
2
2
2
2
2
3
3
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3
3
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3
3
3
3
4
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4
4
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4
4
4
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4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Scheme 5. Mechanistic rational for the Dimroth rearrangement of imidazoles 13.
.4. Thermal behavior studies of imidazoles 13 and 14
2
The thermal behavior of both imdiazoles 13a and 14a was also investigated:
Differential scanning calorimetry (DSC) studies under an argon atmosphere showed
that the imidazole 13a immediately decomposed after melting. On heating a bulk
o
sample under argon atmosphere at ca. 220 C for 20 min a reaction mixture was
obtained from which the imidazole 14a was isolated in low yield (33%) together with
two new products 2ꢀphenylꢀ6ꢀ(phenylamino)pyrimidineꢀ4,5ꢀdicarbonitrile (22) (11%)
and traces of 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (15a) (see
Structural Elucidation Discussion of 15a and 22 in Supporting Information).
Tentatively, pyrimidine 22 can form from imidazole 13a in three steps: Firstly
imidazole 13a ring opens to give the tricyanovinylamidine intermediate 12a which
subsequently undergoes a 6ꢀexoꢀdig heterocyclization on the vicinal nitrile to give
6ꢀiminoꢀ1,2ꢀdiphenylꢀ1,6ꢀdihydropyrimidineꢀ4,5ꢀdicarbonitrile (23), that under the
reaction conditions Dimroth rearranges to the observed pyrimidine 22 (Scheme 6).
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9
Unfortunately, no trace of the pyrimidine 23 could be identified and isolated from the
reaction mixture.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 6. Proposed route for the formation of pyrimidine 22.
Surprisingly, complex reaction mixtures were also obtained when the reaction was
carried out using inert solvents such as toluene, xylene, chlorobenzene or diphenyl
ether at reflux, while in benzene heated to reflux the yellow imidazole 13a was stable.
As for 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (15a), based on the
carbonꢀnitrogen connectivity, we tentatively suggest that the product could have
formed from imidazole 14a via an electrocyclic ring closure and subsequent loss of
HCN (Scheme 7).
Scheme 7. Proposed mechanism for the formation of imidazo[4,5ꢀb]quinoline 15a.
In light of this, we carried out a DSC study of a pure sample of the imidazole 14a that
o
o
showed only an exothermic transition (onset 255.8 C peak 256.7 C). On cooling to
o
ca. 20 C, a TLC analysis of the contents of this DSC pan revealed only one product,
compound 15a. Subsequent thermolysis of the imidazole 14a in diphenyl ether at ca.
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2
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2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
o
280 C, for 4 h protected from moisture with CaCl
2
drying tube, gave compound 15a
o
quantitatively. The reaction temperature could be lowered to 215 C without affecting
the product yield, although this led to longer reaction times (26 h). In boiling benzene
or toluene no 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (15a) was
obtained, while chlorobenzene led to an incomplete reaction even after 2 d. The
reaction was general and nearly all of the imidazoles 14 could be converted into the
their corresponding 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitriles 15 (Table
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4
).
Table 4 Thermolysis of (Z)-2-[4-(arylimino)-2-phenyl-4-1H-imidazol-
5(4H)-ylidene]malononitriles 14 to give 2-phenyl-3H-imidazo[4,5-b]-
quinoline-9-carbonitriles 15.
CN
CN
H
N
R1
R2
N
NC
Ph O,
2
Ph
Ph
N
N
H
N
N
15a-i
R2
R1
14a-i
entries
R1
R2
temp.
time
(h)
yields
(%)
o
(
C)
1
2
3
4
5
6
7
8
9
H
H
H
H
MeO
Me
F
Cl
Cl
Br
I
H
H
H
H
H
H
H
H
Cl
H
H
H
280
260
240
215
280
280
280
280
280
280
280
280
4
6
18
26
2
2
6
6
6
15a (98)
15a (99)
15a (99.5)
15a (99)
15b (99)
15c (99)
15d (99)
15e (98)
15f (84)a
15h (98)
10
11
4
4
6
15i (98)
b
12
O N
2
a
7,8-Dichloro-2-phenyl-1H-imidazo[4,5-b]quinoline-9-carbonitrile (15g)
was also isolated as a side product (12%).
b
A complex and unresolvable reaction mixture was observed.
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9
Worthy of note was that the imidazoles 14 supporting electron donating substituents
on the arylimino group (entries 5 & 6) reacted faster than analogs supporting electron
withdrawing groups (entries 7 & 8). Furthermore, the thermolysis of the
unsymmetrically substituted dichlorophenylimidazole 14f (entry 9) gave as expected
the two possible isomeric products: 6,7ꢀdichloroꢀ2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀ
b]quinolineꢀ9ꢀcarbonitrile (15f) and 7,8ꢀdichloroꢀ2ꢀphenylꢀ1Hꢀimidazo[4,5ꢀb]quinoꢀ
lineꢀ9ꢀcarbonitrile (15g) in 84 and 12% yields, respectively where the product ratio
presumably reflects the steric demands for the respective cyclizations.
Disappointingly, thermolysis of the nitrophenyl analogue (entry 12) led to a very
complex reaction mixture (by TLC) which could not be resolved.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
While there are many examples of the preparation of quinolines via electrocyclic ring
4
6ꢀ52
closures followed by elimination of a leaving group to regain aromaticity,
there
53,54
are very few examples which afford quinolines fused to five
and six membered
55,56
rings,
and only one example involving an ylidenemalononitrile; cyclization of
2,2'ꢀ(2ꢀ{[4ꢀ(dialkylamino)phenyl]ꢀimino}ꢀ1Hꢀindeneꢀ1,3(2H)ꢀdiylidene)dimalonoꢀ
nitriles 24 affords 2ꢀ[2ꢀ(dialkylamino)ꢀ11ꢀcyanoꢀ6Hꢀindeno[2,1ꢀb]quinolinꢀ6ꢀylidꢀ
57
ene)malononitriles 25 in low yields (Scheme 8).
Scheme 8. Example of a quinoline synthesis via electrocylic ring closure.
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9
1
1
1
1
1
1
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1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
2.5. Preparation of Nꢀmethylated 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀ
carbonitriles
The regioselectivity of 2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (15a)
towards Nꢀmethylation was investigated. As such, methylation of 2ꢀphenylꢀ3Hꢀ
imidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (15a) using NaH (2 equiv) and dimethyl
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
o
sulfate (2 equiv) in dry THF at ca. 66 C gave two products: 3ꢀmethylꢀ2ꢀphenylꢀ3Hꢀ
imidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (27) and 4ꢀmethylꢀ2ꢀphenylꢀ4Hꢀimidazo[4,5ꢀ
b]quinolineꢀ9ꢀcarbonitrile (28) in 95 and 1% yields, respectively (Scheme 9). No trace
of 1ꢀmethylꢀ2ꢀphenylꢀ1Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile (26) was observed.
1
The regioselectivity of the methylations was supported by 2DꢀNOESY H NMR
experiments (see Supporting Information).
Scheme 9. NꢀMethylation of imidazo[4,5ꢀb]quinolineꢀ9ꢀcarbonitrile 15a.
Since both the methylated imidazoles (Z)ꢀ2ꢀ[1ꢀmethylꢀ2ꢀphenylꢀ4ꢀ(phenylimino)ꢀ1Hꢀ
imidazolꢀ5(4H)ꢀylidene]malononitrile (16) and (Z)ꢀ2ꢀ[1ꢀmethylꢀ2ꢀphenylꢀ5ꢀ(phenylꢀ
imino)ꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]malononitrile (17) were in our possession these
were also independently thermolyzed to give 1ꢀmethylꢀ2ꢀphenylꢀ1Hꢀimidazo[4,5ꢀ
b]quinolineꢀ9ꢀcarbonitrile (26) and 3ꢀmethylꢀ2ꢀphenylꢀ3Hꢀimidazo[4,5ꢀb]quinolineꢀ9ꢀ
carbonitrile (27) in high yields, respectively (Scheme 10).
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5
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7
8
9
CN
Me
N
Ph O
250 C, 4 h
2
N
N
N
o
Ph
Ph
91%
NC
N
N
Me
CN
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
6
26
CN
N
CN
Ph O
250 C, 4 h
2
N
N
o
N
N
NC
Ph
Ph
93%
N
Me
Me
17
27
Scheme 10. Thermolysis of Nꢀmethylated imidazoles 16 and 17.
3
Conclusions
The reaction of TCNE and N'ꢀarylbenzamidines affords a densely functionalized
adduct which on standing or gentle heating undergoes a 5ꢀexoꢀdig cyclization to give
the novel imidazoles 13. These in turn in neat refluxing MeOH or in DCM with DBU
suffer Dimroth rearrangements to give imidazoles 14. The latter compounds readily
undergo thermal mediated electrocyclic ring closures to give 3Hꢀimidazo[4,5ꢀb]ꢀ
quinolines 15 in almost quantitatively yields. As such, the synthetic route outlined
above affords a new 4ꢀstep but high yielding route to this useful ring system via
readily available TCNE and N'ꢀarylbenzamidines.
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9
1
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1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
4
4
Experimental
General methods and materials
.1
2
Reactions were protected from atmospheric moisture by CaCl drying tubes. All
reaction mixtures and column eluents were monitored by TLC using commercial glass
backed thin layer chromatography (TLC) plates (Kieselgel 60 F ). The plates were
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
254
observed under UV light at 254 and 365 nm. The technique of dry flash
58
chromatography was used throughout for all nonꢀTLC scale chromatographic
separations using silica gel 60 (less than 0.063 mm). Melting points were determined
using a KoeflerꢀHotstage microscope apparatus. Decomposition points (decomp.)
were determined using a DSC with samples hermetically sealed in aluminium pans
under an argon atmosphere, using heating rates of 5 ºC/min. Solvents used for
recrystallization are indicated after the melting point. Inflections in the UV spectra are
identified by the abbreviation “inf”. IR spectra were recorded using a Ge ATR
accessory and strong, medium and weak peaks are represented by s, m and w
1
13
respectively. H and C NMR spectra were recorded at 500 and 125 MHz,
respectively. Deuterated solvents were used for homonuclear lock and the signals are
referenced to the deuterated solvent peaks. DEPT135 or APT NMR studies identified
quaternary and tertiary carbons, which are indicated by (s) and (d) notations,
respectively. Deuterated solvents were used for homonuclear lock and the signals are
referenced to the deuterated solvent peaks. Low resolution (EI) mass spectra were
59
recorded on a GCMS with direct inlet probe. Tetracyanoethylene (TCNE) and the
3
0
N'ꢀarylbenzamidines 11a-i, were prepared according to literature procedures.
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4.2
.2.1
Reaction of N'-arylbenzamidines with tetracyanoethylene (TCNE)
N'ꢀPhenylꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12a) (Typical Procedure, see
Table 1).
4
To a stirred solution of tetracyanoethylene (128 mg, 1 mmol) in dry THF (5 mL), at
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
o
ca. 20 C and protected with CaCl drying tube was added a solution of N'ꢀphenylꢀ
2
benzamidine (11a) (196 mg, 1 mmol) in dry THF (5 mL). The mixture was then left
o
to stir at ca. 20 C for 2 h, after which time the reaction was complete (by TLC), and
o
the solvent was evaporated under reduced pressure (at < 25 C). The residue was then
o
dissolved in Et O (2 mL) and after cooling to 0 C, nꢀpentane (40 mL) was added and
2
triturated to form the precipitated title compound 12a (288.7 mg, 97%) as colorless
o
o
o
plates, mp (DSC) onset 135.7 C, peak max. 139.1 C, decomp. onset 140.8 C peak
o
max. 141.0 C (from nꢀpentane/THF); (found: C, 72.61; H, 3.66; N, 23.45. C18
H
11
N
5
requires C, 72.72; H, 3.73; N, 23.56%); R
f
0.51 (DCM/Et
2
O, 95:05); λmax(DCM)/nm
ꢀ1
241 (log ε 4.29), 280 inf (3.74); νmax/cm 3258m (NH), 3064w (Ar CH), 2826w,
2
1
1
8
201w (C≡N), 1692s, 1670w, 1651w, 1603m, 1593m, 1562s, 1557s, 1493m, 1454w,
445m, 1375m, 1323m, 1315m, 1310m, 1285m, 1263m, 1184w, 1159w, 1126s,
071m, 1039w, 1030m, 1007m, 1001w, 941w, 935w, 918m, 910m, 881m, 847w,
H 3
14w, 783s, 729m; δ (500 MHz; CDCl ) 8.04 (1H, br s, NH), 7.54ꢀ7.50 (3H, m, Ar
H), 7.49ꢀ7.46 (3H, m, Ar H), 7.32 (2H, dd, J 8.0, 8.0, Ar H), 7.17 (2H, br s, Ar H);
δ (125 MHz; CDCl ) 168.5 (s), 161.8 (s), 132.84 (s), 132.81 (d), 130.8 (d), 130.4 (d),
C
3
1
29.3 (d), 128.6 (d), 127.8 (d), 126.4 (s), 112.5 (s, C≡N), 108.4 (s, C≡N), 108.0 (s,
+
+
2
C≡N), 66.9 [s, C(CN) ]; m/z (MALDIꢀTOF) 299 (MH +1, 1%), 298 (MH , 8), 295,
(3), 282 (100), 261 (3), 260 (7), 259 (8), 180 (18).
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4.2.2
N'ꢀ(4ꢀMethoxyphenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12b)
Similar treatment of TCNE (128 mg, 1 mmol) with N'ꢀ(4ꢀmethoxyphenyl)benzamidꢀ
ine (11b) (226 mg, 1 mmol) gave the title compound 12b (319.3 mg, 98%) as
o
colorless plates, mp 68.8–69.5 C (from nꢀpentane/THF); (found: C, 69.62; H, 4.18;
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
N, 21.40. C H N O requires C, 69.71; H, 4.00; N, 21.39%); R 0.56 (DCM/Et O,
19
13
5
f
2
ꢀ1
95:05); λmax(DCM)/nm 237 (log ε 4.51), 275 inf (3.96); νmax/cm 3269m (NH),
3063w (Ar CH), 2899w, 2843w, 2226w (C≡N), 1695w, 1684w, 1653w, 1636w,
1607w, 1593w, 1568w, 1539w, 1512s, 1466w, 1447w, 1420w, 1387w, 1321m,
1312m, 1302m, 1254s, 1180w, 1171w, 1125m, 1065w, 1028w, 910w, 841m, 812w,
799w, 775w, 746w; δ (500 MHz; CDCl ) NH resonance missing, 7.50ꢀ7.48 (3H, m,
H
3
Ar H), 7.33 (2H, dd, J 8.0, 8.0, Ar H), 7.08 (2H, br s, Ar H), 6.99 (2H, d, J 8.0, Ar H),
3
.85 (3H, s, OCH
3 C 3
); δ (125 MHz; CDCl ) 168.7 (s), 162.4 (s), 160.7 (s), 132.7 (d),
1
29.3 (d), 129.2 (d), 128.6 (d), 126.5 (s), 125.0 (s), 116.0 (d), 112.5 (s, C≡N), 108.5
(s, C≡N), 108.0 (s, C≡N), 66.7 [s, C(CN) ], 55.6 (q, OCH ); m/z (MALDIꢀTOF) 331
2
3
+
+
+
(
MH +2, 17%), 331 (MH +1, 3), 328 (MH , 2), 312 (8), 227 (29), 211 (12), 210
(100), 181 (13), 71 (8).
4
.2.3
Similar treatment of TCNE (128 mg, 1 mmol) with N'ꢀ(pꢀtolyl)benzamidine (11c)
210 mg, 1 mmol) gave the title compound 12c (309.3 mg, 99%) as colorless plates,
N'ꢀ(pꢀTolyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12c)
(
o
o
o
mp (DSC) onset 149.4 C, peak max. 151.0 C, decomp. onset 152.2 C peak max.
o
1
53.6 C (from nꢀpentane/THF); (found: C, 73.33; H, 4.25; N, 22.58. C19
H
13
N
5
requires C, 73.30; H, 4.21; N, 22.49%); R
f
0.59 (DCM/Et
2
O, 95:05); λmax(DCM)/nm
ꢀ1
2
39 (log ε 4.31), 277 inf (3.80); νmax/cm 3252m (NH), 2808w, 2517w, 2199w
(C≡N), 1694m, 1682m, 1601m, 1591m, 1560s, 1510m, 1497w, 1470w, 1447m,
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1385m, 1379m, 1323s, 1315m, 1296s, 1265m, 1213w, 1179w, 1128s, 1072m, 1065m,
1
8
7
040w, 1030m, 1022w, 1007m, 980w, 966w, 945w, 933w, 912m, 880m, 845w,
30m, 810m, 806w, 798w, 781m, 746m; δ (500 MHz; CDCl ) 8.00 (1H, s, NH),
.50ꢀ7.46 (3H, m, Ar H), 7.34ꢀ7.29 (4H, m, Ar H), 7.03 (2H, br s, Ar H), 2.42 (3H, s,
H
3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
CH ); δ (125 MHz; CDCl ) 168.5 (s), 162.1 (s), 140.8 (s), 132.8 (d), 131.4 (d), 130.1
3
C
3
(
(
(
s), 129.3 (d), 128.6 (d), 127.5 (d), 126.5 (s), 112.5 (s, C≡N), 108.4 (s, C≡N), 108.0
+
s, C≡N), 66.8 [s, C(CN)
2
], 21.3 (q, CH
3
); m/z (MALDIꢀTOF) 312 (MH , 4%), 296
7), 275 (3), 247 (4), 194 (100), 105 (3), 91 (9).
4.2.4
Similar treatment of TCNE (128 mg, 1 mmol) with N'ꢀ(4ꢀfluorophenyl)benzamidine
11d) (214 mg, 1 mmol) gave the title compound 12d (299.6 mg, 95%) as colorless
N'ꢀ(4ꢀFluorophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12d)
(
o
o
o
plates, mp (DSC) onset 146.0 C, peak max. 148.2 C, decomp. onset 149.1 C peak
o
max. 150.4 C (from nꢀpentane/THF); (found: C, 68.36; H, 3.33; N, 22.19. C H FN
18
10
5
requires C, 68.57; H, 3.20; N, 22.21%); R 0.49 (DCM/Et O, 95:05); λmax(DCM)/nm
f
2
ꢀ1
2
44 (log ε 4.23), 276 inf (3.76); νmax/cm 3258m (NH), 2814w, 2521w, 2203w
C≡N), 1697m, 1686m, 1605m, 1593m, 1562m, 1508s, 1447m, 1418w, 1379m,
323m, 1314m, 1292m, 1287m, 1265w, 1238m, 1223m, 1184w, 1155m, 1126s,
1096w, 1071m, 1042w, 1030m, 1008m, 982w, 943w, 933w, 916m, 883m, 849m,
41m, 822w, 802w, 783m, 750m; δ (500 MHz; CDCl ) 8.02 (1H, br s, NH), 7.51
(
1
8
H
3
(1H, dd, J 7.5, 7.5, Ar H), 7.46 (2H, d, J 8.5, Ar H), 7.35 (2H, dd, J 8.0, 8.0, Ar H),
1
7
.21ꢀ7.19 (4H, m, Ar H); δ
C
(125 MHz; CDCl
3
) 168.5 (s), 163.1 (s, JCF 251.5, CF),
3
161.8 (s), 133.0 (d), 129.9 (d, JCF 8.9, CHCHCF), 129.2 (d), 128.8 (d), 126.2 (s),
2
1
18.1 (d, J 22.4, CHCF), 112.3 (s, C≡N), 108.3 (s, C≡N), 108.0 (s, C≡N), 68.0 [s,
CF
+
C(CN) ]; m/z (MALDIꢀTOF) 316 (MH , 3%), 300 (5), 198 (100), 105 (4).
2
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4.2.5
N'ꢀ(4ꢀChlorophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12e)
Similar treatment of TCNE (154 mg, 1.2 mmol) with N'ꢀ(4ꢀchlorophenyl)benzamidine
11e) (231 mg, 1 mmol) gave the title compound 12e (314.6 mg, 95%) as colorless
(
o
o
o
plates, mp (DSC) onset 146.8 C, peak max. 148.4 C, decomp. onset 150.3 C peak
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
o
max. 151.9 C (from nꢀpentane/THF); (found: C, 64.97; H, 2.93; N, 21.17.
C
18
H
10ClN
5
requires C, 65.17; H, 3.04; N, 21.11%); R
f
2
0.41 (DCM/Et O, 95:05);
ꢀ1
λ
max(DCM)/nm 242 (log ε 4.33), 277 inf (3.81); νmax/cm 3254w (NH), 2525w,
2
1
201w (C≡N), 1692m, 1603m, 1593m, 1562m, 1493s, 1447m, 1408w, 1383w,
323m, 1304m, 1294m, 1277w, 1265w, 1188w, 1128m, 1094m, 1071w, 1030w,
1016m, 945w, 939w, 930w, 912m, 880w, 837m, 822w, 806w, 781m, 760w, 739w;
(500 MHz; CDCl ) 8.05 (1H, s, NH), 7.54ꢀ7.49 (3H, m, Ar H), 7.46 (2H, d, J 8.5,
Ar H), 7.36 (2H, dd, J 7.8, 7.8, Ar H), 7.11 (2H, br s, Ar H); δ (125 MHz; CDCl
68.3 (s), 161.5 (s), 136.6 (s), 133.0 (d), 131.3 (s), 131.1 (d), 129.2 (d), 129.1 (d),
128.8 (d), 126.1 (s), 112.3 (s, C≡N), 108.3 (s, C≡N), 107.9 (s, C≡N), 66.9 [s,
δ
H
3
C
3
)
1
+
+
C(CN) ]; m/z (MALDIꢀTOF) 334 (MH +2, 3%), 332 (MH , 1), 318 (12), 316 (55),
2
2
94 (34), 231 (30), 216 (29), 214 (100).
4
.2.6
N'ꢀ(3,4ꢀDichlorophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12f)
Similar treatment of TCNE (154 mg, 1.2 mmol) with N'ꢀ(3,4ꢀdichlorophenyl)benzꢀ
amidine (11f) (265 mg, 1 mmol) gave the title compound 12f (335.1 mg, 92%) as
o
o
colorless plates, mp (DSC) onset 151.5 C, peak max. 155.5 C, decomp. onset
o
o
1
57.0 C peak max. 158.1 C (from nꢀpentane/THF); (found: C, 58.83; H, 2.59; N,
19.21. C18 Cl requires C, 59.04; H, 2.48; N, 19.12%); R 0.46 (DCM/Et O,
5:05); λmax(DCM)/nm 244 (log ε 4.67), 278 inf (4.13); νmax/cm 3254m (NH),
H
9
2
N
5
f
2
ꢀ1
9
2
795w, 2533w, 2259w and 2197w (C≡N), 1703w, 1688s, 1605m, 1593m, 1564m,
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1497w, 1474s, 1447w, 1406w, 1393w, 1370w, 1327m, 1304s, 1277m, 1242w, 1128s,
1
8
7
086w, 1076w, 1065m, 1036m, 1011w, 982w, 957w, 932w, 912m, 887w, 874m,
47w, 829m, 818w, 797m, 781s, 745m; δ (500 MHz; CDCl ) 8.12 (1H, br s, NH),
.58 (1H, d, J 8.5 Ar H), 7.55 (1H, dd, J 7.5, 7.5, Ar H), 7.47 (2H, d, J 7.5, Ar H),
H
3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7.38 (2H, dd, J 7.8, 7.8, Ar H), 7.33 (1H, br s, Ar H), 6.99 (1H, br s, Ar H); δ (125
C
MHz; CDCl
3
) 167.8 (s), 160.8 (s), 135.4 (s), 135.2 (s), 133.2 (d), 132.6 (d), 132.0 (s),
1
1
2
29.5 (d), 129.2 (d), 129.0 (d), 127.1 (d), 125.8 (s), 112.1 (s, C≡N), 108.2 (s, C≡N),
+
+
07.9 (s, C≡N), 67.2 [s, C(CN)
2
]; m/z (MALDIꢀTOF) 368 (MH +2, 3%), 366 (MH ,
), 350 (8), 329 (4), 303 (2), 250 (65), 248 (100), 207 (8), 199 (9), 181 (7), 127 (8),
111 (22), 109 (4), 105 (15), 97 (5), 88 (13), 77 (2).
4
.2.7
N'ꢀ(4ꢀBromophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12g)
Similar treatment of TCNE (154 mg, 1.2 mmol) with N'ꢀ(4ꢀbromophenyl)benzamidꢀ
ine (11g) (275 mg, 1 mmol) gave the title compound 12g (346.0 mg, 92%) as
o
colorless plates, mp 85.2–86.6 C (from nꢀpentane/THF); (found: C, 57.39; H, 2.72;
N, 18.62. C18
5 f 2
H10BrN requires C, 57.47; H, 2.68; N, 18.62%); R 0.54 (DCM/Et O,
ꢀ1
9
5:05); λmax(DCM)/nm 242 (log ε 4.48), 279 inf (3.87); νmax/cm 3277w (NH), 3099w
and 3063w (Ar CH), 2974w, 2899w, 2255w and 2201w (C≡N), 1692m, 1653w,
1609m, 1595m, 1568m, 1489s, 1449m, 1402w, 1379m, 1311s, 1296m, 1273w,
1
7
249w, 1202w, 1182w, 1125s, 1072s, 1030w, 1013s, 937w, 910m, 837s, 808w,
94w, 777s, 750m; δ (500 MHz; CDCl ) 8.05 (1H, br s, NH), 7.64 (2H, d, J 8.0 Ar
H
3
H), 7.52 (1H, dd, J 7.3, 7.3, Ar H), 7.46 (2H, d, J 8.5, Ar H), 7.36 (2H, dd, J 7.8, 7.8,
Ar H), 7.04 (2H, d, J 5.5, Ar H); δ (125 MHz; CDCl ) 168.3 (s), 161.4 (s), 134.1 (d),
33.0 (d), 131.8 (s), 129.3 (d), 129.2 (d), 128.8 (d), 126.1 (s), 124.6 (s), 112.3 (s,
C
3
1
C≡N), 108.3 (s, C≡N), 107.9 (s, C≡N), 66.9 [s, C(CN) ]; m/z (MALDIꢀTOF) 378
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5
5
5
5
5
6
+
+
(MH +2, 2%), 376 (MH , 1), 362 (4), 360 (5), 312 (2), 260 (90), 258 (100), 181 (26),
1
11 (3), 71 (27).
4
.2.8
N'ꢀ(4ꢀIodophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12h)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
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3
4
5
6
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9
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1
2
3
4
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8
9
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1
2
3
4
5
6
7
8
9
0
Similar treatment of TCNE (154 mg, 1.2 mmol) with N'ꢀ(4ꢀiodophenyl)benzamidine
(
11h) (322 mg, 1 mmol) gave the title compound 12h (366.0 mg, 87%) as colorless
o
plates, mp 89.5–91.2 C (from nꢀpentane/THF); (found: C, 51.22; H, 2.31; N, 16.68.
18 5 f 2
C H10IN requires C, 51.08; H, 2.38; N, 16.55%); R 0.59 (DCM/Et O, 95:05);
ꢀ1
λmax(DCM)/nm 246 (log ε 4.51), 278 inf (3.94); νmax/cm 3273w (NH), 3067w (Ar
CH), 2964w, 2903w, 2255w and 2201w (C≡N), 1692m, 1609m, 1593m, 1566m,
1
1
493m, 1487s, 1449m, 1398w, 1375m, 1319s, 1312s, 1250w, 1182w, 1125s, 1067m,
028w, 1009s, 937w, 910m, 849m, 835m, 777m, 748m; δ (500 MHz; CDCl ) 8.06
H
3
(
1H, br s, NH), 7.84 (2H, d, J 8.0, Ar H), 7.52 (1H, dd, J 7.5, 7.5, Ar H), 7.46 (2H, d,
J 8.5, Ar H), 7.36 (2H, dd, J 7.8, 7.8, Ar H), 6.90 (2H, d, J 5.5, Ar H); δ (125 MHz;
C
CDCl ) 168.3 (s), 161.4 (s), 140.1 (d), 133.0 (d), 132.6 (s), 129.4 (d), 129.2 (d), 128.8
3
(
d), 126.1 (s), 112.3 (s, C≡N), 108.3 (s, C≡N), 107.9 (s, C≡N), 96.3 (s), 66.9 [s,
+
+
2
C(CN) ]; m/z (MALDIꢀTOF) 426 (MH +2, 1%), 424 (MH , 2), 408 (2), 387 (2), 386
(
2), 323 (55), 307 (10), 306 (100), 180 (30), 179 (11), 105 (9).
4
.2.9
N'ꢀ(4ꢀNitrophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12i)
Similar treatment of TCNE (154 mg, 1.2 mmol) with N'ꢀ(4ꢀnitrophenyl)benzamidine
11i) (241 mg, 1 mmol) gave the title compound 12i (301.0 mg, 88%) as colorless
(
o
o
o
plates, mp (DSC) onset 149.9 C, peak max. 152.9 C, decomp. onset 155.1 C peak
o
max. 156.1 C (from nꢀpentane/THF); (found: C, 62.97; H, 2.84; N, 24.55.
C H N O requires C, 63.16; H, 2.94; N, 24.55%); R 0.64 (DCM/Et O, 95:05);
18
10
6
2
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1
λ
max(DCM)/nm 248 (log ε 4.29), 282 inf (4.03); νmax/cm 3296w (NH), 3119w and
3
1
1
082w (Ar CH), 2808w, 2627w, 2260w and 2201w (C≡N), 1757w, 1692m, 1612m,
593m, 1574m, 1524s, 1497m, 1474w, 1449w, 1420w, 1387m, 1348s, 1321m,
312m, 1292w, 1234w, 1184w, 1176w, 1144m, 1132m, 1109w, 1074w, 1028w,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
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40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1011w, 1001w, 939w, 926w, 912m, 856m, 837m, 822w, 771m, 754m, 741w; δ (500
H
MHz; CDCl
.3 Ar H), 7.43 (2H, d, J 8.5, Ar H), 7.39ꢀ7.35 (4H, m, Ar H); δ
one C (s) peak missing 149.0 (s), 148.1 (s), 138.5 (s), 133.3 (d), 129.1 (d), 129.0 (d),
28.7 (d), 125.9 (d), 125.8 (s), 112.0 (s, C≡N), 108.1 (s, C≡N), 107.8 (s, C≡N), 68.0
3
) NH resonance missing, 8.35 (2H, d, J 8.5, Ar H), 7.55 (1H, dd, J 7.3,
7
C
(125 MHz; CDCl )
3
1
+
+
[s, C(CN) ]; m/z (MALDIꢀTOF) 344 (MH +1, 1%), 343 (MH , 2), 340 (5), 327 (100),
2
3
04 (41), 242 (11), 225 (99), 179 (48).
4
.3
Conversion of N-Aryl-N-(1,2,2-tricyanovinyl)benzamidines into 2-[5-
imino-1-aryl-2-phenyl-1H-imidazol-4(5H)-ylidene]malononitriles
.3.1 2ꢀ[5ꢀIminoꢀ1,2ꢀdiphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]malononitrile
Typical Procedure, see Table 2).
4
(13a)
(
A stirred solution of N'ꢀphenylꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12a) (29.7 mg,
o
0
.1 mmol) in dry acetonitrile (1 mL) was heated at ca. 82 C for 3 h and
chromatography (DCM) of the residue gave the title compound 13a (26.2 mg, 88%)
o
o
as yellow prisms, mp (DSC) onset 195.6 C, peak max. 201.3 C, decomp. onset 205.2
o
o
C peak max. 207.9 C (from nꢀpentane/THF, 90:10); (found: C, 72.61; H, 3.66; N,
3.45. C18 requires C, 72.72; H, 3.73; N, 23.56%); R 0.48 (DCM);
max(DCM)/nm 235 (log ε 3.62), 265 (3.36), 331 (4.24), 440 (4.31); νmax/cm 3237w
NH), 3063w and 3051w (Ar CH), 2234w and 2214w (C≡N), 1655w, 1609w, 1597w,
2
H
11
N
5
f
ꢀ1
λ
(
1
578w, 1503m, 1493m, 1466s, 1441m, 1416s, 1331s, 1317m, 1275m, 1221m, 1196w,
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1182w, 1163w, 1121m, 1072w, 1032w, 1000w, 980w, 941w, 872m, 843w, 781m;
δ
H
(500 MHz; CDCl
.67 (2H, d, J 7.5, Ar H), 7.64ꢀ7.62 (3H, m, Ar H), 7.60ꢀ7.56 (2H, m, Ar H), 7.54ꢀ
.52 (3H, m, Ar H), 7.38ꢀ7.34 (4H, m, Ar H), 7.25ꢀ7.23 (2H, m, Ar H), 7.20ꢀ7.18
3
) 10.39 (1H, s, NH), 9.26 (1H, s, NH), 7.71 (2H, d, J 7.5, Ar H),
7
7
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(2H, m, Ar H); δ [500 MHz; CDCl /HCl (g)] NH resonance missing, 7.69 (2H, d, J
H
3
8
.5, Ar H), 7.59ꢀ7.56 (4H, m, Ar H), 7.36 (2H, dd, J 8.0, 8.0, Ar H), 7.23ꢀ7.21 (2H,
m, Ar H); δ (500 MHz; DMSOꢀd ) 10.47 (1H, s, NH), 7.63ꢀ7.54 (6H, m, Ar H), 7.45ꢀ
.42 (4H, m, Ar H); δ (125 MHz; CDCl ) 171.4 (s), 168.7 (s), 165.0 (s), 160.8 (s),
58.4 (s), 157.3 (s), 134.8 (d), 134.6 (d), 133.9 (s), 132.5 (s), 131.23 (d), 131.20 (d),
H
6
7
1
C
3
131.0 (d), 130.9 (d), 130.1 (d), 130.0 (d), 128.89 (d), 128.85 (d), 128.1 (d), 128.0 (d),
1
7
1
25.8 (s), 125.6 (s), 113.0 (s, C≡N), 112.5 (s, C≡N), 112.3 (s, C≡N), 111.7 (s, C≡N),
2.1 [s, C(CN) ], 70.5 [s, C(CN) ]; δ (125 MHz; DMSOꢀd ) 170.0 (s), 167.0 (s),
55.6 (s), 134.1 (d), 132.5 (s), 130.4 (d), 130.3 (d), 130.2 (d), 128.72 (d), 128.69 (d),
2
2
C
6
126.1 (s), 113.6 (s, C≡N), 112.9 (s, C≡N), 67.1 [s, C(CN) ]; m/z (MALDIꢀTOF) 299
2
+
+
+
(
MH +1, 25%), 298 (MH , 100), 242 (2), 180 (4), 153 (70); m/z (EI) 297 (M , 58%),
2
96 (100), 271 (7), 244 (3), 194 (22), 180 (12), 167 (6), 153 (3), 118 (12), 104 (17),
1 (5), 77 (73), 65 (3), 51 (32).
9
4.3.2 2ꢀ[5ꢀIminoꢀ1ꢀ(4ꢀmethoxyphenyl)ꢀ2ꢀphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]ꢀ
malononitrile (13b)
Similar treatment of N'ꢀ(4ꢀmethoxyphenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12b)
(32.7 mg, 0.1 mmol) gave the title compound 13b (29.1 mg, 89%) as orange prisms,
o
o
o
mp (DSC) onset 187.1 C, peak max. 191.1 C, decomp. onset 195.4 C, peak max.
o
2
03.0 C (from cyclohexane/DCE, 50:50); (found: C, 69.62; H, 3.90; N, 21.27.
C H N O requires C, 69.71; H, 4.00; N, 21.39%); R 0.38 (DCM); λmax(DCM)/nm
19
13
5
f
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233 (log ε 4.30), 267 (3.85), 276 inf (3.84), 283 inf (3.87), 319 (4.16), 378 inf (3.98),
ꢀ
1
4
47 (4.22); νmax/cm 3265w and 3232w (NH), 3069w (Ar CH), 2976 (CH
and 2208w (C≡N), 1653w, 1605w, 1595w, 1578w, 1514m, 1504w, 1468s, 1445m,
423m, 1410m, 1337m, 1304w, 1273m, 1256m, 1217m, 1182w, 1171w, 1123m,
1076w, 1020w, 1001w, 982w, 912w, 854w, 845m, 810w, 781w, 766w; δ [500 MHz;
3
), 2224w
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
H
CDCl
J 7.5, 7.5, Ar H), 7.37 (2H, dd, J 8.0, 8.0, Ar H), 7.13 (2H, d, J 9.0, Ar H), 7.05 (2H,
d, J 9.0, Ar H), 3.89 (3H, s, OCH ); δ (500 MHz; DMSOꢀd ) 10.41 (1H, s, NH),
.64ꢀ7.59 (3H, m, Ar H), 7.45 (2H, dd, J 8.0, 8.0, Ar H), 7.36 (2H, d, J 9.0, Ar H),
7.12 (2H, d, J 8.5, Ar H), 3.82 (3H, s, OCH ); δ (125 MHz; DMSOꢀd ) 170.2 (s),
3
/HCl (g)] NH resonance missing, 7.73 (2H, dd, J 8.5, 1.0, Ar H), 7.58 (1H, dd,
3
H
6
7
3
C
6
1
67.1 (s), 160.2 (s), 156.3 (s), 134.1 (d), 130.5 (d), 130.2 (d), 128.8 (d), 126.3 (s),
24.8 (s), 115.6 (d), 113.7 (s, C≡N), 113.1 (s, C≡N), 66.4 [s, C(CN) ], 55.5 (q,
); m/z (MALDIꢀTOF) 329 (MH +1, 24%), 328 (MH , 100), 252 (17), 210 (8),
1
2
+
+
OCH
3
153 (2).
4
.3.3
2ꢀ[5ꢀIminoꢀ2ꢀphenylꢀ1ꢀpꢀtolylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]malononitrile
13c)
(
Similar treatment of N'ꢀ(pꢀtolyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12c) (31.1 mg,
0.1 mmol) gave the title compound 13c (27.7 mg, 89%) as yellow needles, mp (DSC)
o
o
o
o
onset 173.9 C, peak max. 179.9 C, decomp. onset 192.5 C peak max. 202.7 C
from nꢀpentane/THF, 90:10); (found: C, 73.16; H, 4.15; N, 22.33. C19 requires
C, 73.30; H, 4.21; N, 22.49%); R 0.57 (DCM); λmax(DCM)/nm 237 (log ε 4.07), 267
(3.89), 327 (4.22), 445 (4.29); νmax/cm 3227m (NH), 3065w and 3042w (Ar CH),
(
13 5
H N
f
ꢀ1
2
1
230w and 2214w (C≡N), 1651w, 1607w, 1591w, 1578w, 1518m, 1503w, 1466s,
439m, 1418s, 1331s, 1318w, 1300w, 1277m, 1221m, 1194w, 1182w, 1159w,
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1121m, 1082w, 1070w, 1034w, 979w, 947w, 905w, 885m, 820m, 785m, 760w;
H 3
δ [500 MHz; CDCl /HCl (g)] NH resonance missing, 7.72 (2H, d, J 7.5, Ar H), 7.58
(
1H, dd, J 7.5, 7.5, Ar H), 7.38ꢀ7.35 (4H, m, Ar H), 7.09 (2H, d, J 8.0, Ar H), 2.46
3H, s, CH ); δ (500 MHz; DMSOꢀd ) 10.41 (1H, s, NH), 7.62 (1H, dd, J 7.5, 7.5, Ar
(
3
H
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
H), 7.58 (2H, d, J 8.0, Ar H), 7.44 (2H, dd, J 8.0, 7.5, Ar H), 7.39 (2H, d, J 8.0, Ar
H), 7.30 (2H, d, J 8.0, Ar H), 2.40 (3H, s, CH ); δ (125 MHz; DMSOꢀd ) 170.1 (s),
67.0 (s), 155.9 (s), 139.9 (s), 134.1 (d), 130.9 (d), 130.4 (d), 129.8 (s), 128.7 (d),
28.5 (d), 126.2 (s), 113.7 (s, C≡N), 113.0 (s, C≡N), 66.7 [s, C(CN) ], 20.8 (q, CH );
3
C
6
1
1
2
3
+
+
m/z (MALDIꢀTOF) 313 (MH +1, 11%), 312 (MH , 100).
4
.3.4
2ꢀ[1ꢀ(4ꢀFluorophenyl)ꢀ5ꢀiminoꢀ2ꢀphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]ꢀ
malononitrile (13d)
Similar treatment of N'ꢀ(4ꢀfluorophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12d)
(31.5 mg, 0.1 mmol) gave the title compound 13d (28.0 mg, 89%) as yellow needles,
o
o
o
mp (DSC) onset 192.7 C, peak max. 197.6 C, decomp. onset 201.1 C peak max.
o
2
10.1 C (from nꢀpentane/THF, 90:10); (found: C, 68.46; H, 3.33; N, 22.16.
C
18
H
10FN
5
requires C, 68.57; H, 3.20; N, 22.21%); R
38 (log ε 3.73), 265 (2.70), 331 (4.18), 440 (4.25); νmax/cm 3235m (NH), 3073w
(Ar CH), 2232w and 2216w (C≡N), 1653w, 1609w, 1580w, 1512s, 1466s, 1445s,
f
0.50 (DCM); λmax(DCM)/nm
ꢀ1
2
1
1
8
418s, 1331s, 1315w, 1300w, 1277m, 1236m, 1221s, 1194w, 1184w, 1167w, 1155w,
121m, 1099w, 1080w, 1074w, 1032w, 1001w, 984m, 964w, 945w, 874m, 841m,
H 3
20w, 814w, 779m, 756w; δ [500 MHz; CDCl /HCl (g)] NH resonance missing, 7.69
(2H, d, J 8.0, Ar H), 7.60 (1H, dd, J 7.5, 7.5, Ar H), 7.39 (2H, dd, J 8.0, 8.0, Ar H),
7
.27ꢀ7.21 (4H, m, Ar H); δ (500 MHz; DMSOꢀd ) 11.02 (1H, s, NH), 8.05 (1H, dd, J
H 6
7
.5, 7.5, Ar H), 7.98 (2H, d, J 8.0, Ar H), 7.94ꢀ97 (2H, m, Ar H), 7.89ꢀ7.84 (4H, m,
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Ar H); δ
C
6
(125 MHz; DMSOꢀd ) 170.0 (s), 167.0 (s), 162.6 (s, JCF 245.0, CF), 155.6
3
(
s), 134.1 (d), 131.4 (d, JCF 8.8, CHCHCF), 130.4 (d), 128.84 (s), 128.77 (d), 126.1
2
(
s), 117.3 (d, JCF 23.8, CHCF), 113.6 (s, C≡N), 112.9 (s, C≡N), 66.7 [s, C(CN)
2
];
+
+
m/z (MALDIꢀTOF) 317 (MH +1, 13%), 316 (MH , 100), 252 (2), 198 (3), 105 (2).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4
.3.5
2ꢀ[1ꢀ(4ꢀChlorophenyl)ꢀ5ꢀiminoꢀ2ꢀphenylꢀ1Hꢀimidazolꢀ4(5H)ꢀylidene]ꢀ
malononitrile (13e)
Similar treatment of N'ꢀ(4ꢀchlorophenyl)ꢀNꢀ(1,2,2ꢀtricyanovinyl)benzamidine (12e)
33.2 mg, 0.1 mmol) gave the title compound 13e (28.9 mg, 87%) as yellow needles,
(
o
o
o
mp (DSC) onset 188.6 C, peak max. 193.5 C, decomp. onset 198.2 C peak max.
o
2
01.5 C (from nꢀpentane/THF, 50:50); (found: C, 65.16; H, 2.99; N, 20.94.
C
18
H
10ClN
5
requires C, 65.17; H, 3.04; N, 21.11%); R
30 (log ε 4.11), 267 (3.69), 332 (4.12), 440 (4.23); νmax/cm 3231m (NH), 3061w
(Ar CH), 2230w and 2218w (C≡N), 1651w, 1609w, 1591w, 1578w, 1503m, 1495s,
f
0.55 (DCM); λmax(DCM)/nm
ꢀ1
2
1
1
7
466s, 1443s, 1414s, 1329s, 1315w, 1302w, 1277m, 1223s, 1194w, 1182w, 1123m,
094m, 1082w, 1074w, 1032w, 1020w, 980w, 947w, 878m, 835m, 822w, 781m,
H 3
54w; δ [500 MHz; CDCl /HCl (g)] NH resonance missing, 7.69 (2H, d, J 7.5, Ar
H), 7.61 (1H, dd, J 7.5, 7.5, Ar H), 7.53 (2H, d, J 7.5, Ar H), 7.40 (2H, dd, J 8.0, 8.0,
Ar H), 7.17 (2H, d, J 8.5, Ar H); δ (500 MHz; DMSOꢀd ) 10.67 (1H, s, NH), 7.67ꢀ
H
6
7
.62 (3H, m, Ar H), 7.56 (2H, d, J 8.0, Ar H), 7.48ꢀ7.46 (4H, m, Ar H); δ (125 MHz;
C
DMSOꢀd
6
) 169.9 (s), 167.0 (s), 155.2 (s), 134.8 (s), 134.1 (d), 131.5 (s), 130.8 (d),
1
30.4 (d), 130.3 (d), 128.8 (d), 126.0 (s), 113.5 (s, C≡N), 112.9 (s, C≡N), 66.8 [s,
+
+
+
2
C(CN) ]; m/z (MALDIꢀTOF) 334 (MH +2, 25%), 333 (MH +1, 9), 332 (MH , 100),
2
14 (3), 153 (2).
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