Reactions of carbanions with 2,4-dinitrofluorobenzene leading to stable heptatrienide moieties

Article abstract of DOI:10.1002/hc.20267

Reactions of NCCH₂COOMe 1a and CH₂(CN)₂ 1b with 2,4-dinitrofluorobenzene 2 at the presence of Et₃ N result in deeply colored crystalline stable salts 4a,4b with anions that contain a system of conjugated bonds.

Full text of DOI:10.1002/hc.20267

Heteroatom Chemistry
Volume 18, Number 1, 2007
Reactions of Carbanions
with 2,4-Dinitrofluorobenzene Leading
to Stable Heptatrienide Moieties
Yuri G. Gololobov, Olesya A. Linchenko, Pavel V. Petrovskii,
Zoija A. Starikova, and Irina A. Garbuzova
A.N.Nesmeyanov Institute of Organo-Element Compounds, Russian Academy of Science,
119991 M-334, Vavilov Str. 28, Moscow, Russia
Received 21 December 2005; revised 13 February 2006
troscopy data for the reaction of malonic ester with
ABSTRACT: Reactions of NCCH2COOMe 1a and
2 at the presence of triethylamine [1].
CH2(CN)2 1b with 2,4-dinitrofluorobenzene 2 at the
The development of new methods to synthe-
presence of Et3 N result in deeply colored crystalline
size highly conjugated, deeply colored stable organic
stable salts 4a,4b with anions that contain a sys-
salts and phosphonio heptatrienide zwitterion may
tem of conjugated bonds. Similar reaction of 2 with
be of interest to build electron conductive materials
phosphorus-containing zwitterion 6 bearing ethoxy-
and new reagents for analytical chemistry.
and cyano-groups at the carbanion center is the first
In this work, we report new reactions of carban-
example of the reaction leading to the formation of
ions with 2,4-dinitrofluorobenzene that lead to new
P-zwitterion 9 with a negatively charged heptatriene
stable salts with the system of conjugated bonds and
moiety. This reaction proceeds via a new route
the first synthesis of phosphorus-containing zwitte-
of decomposition of the intermediate σ-complex
rion with heptatriene moiety.
7 occurring with formation of ethylfluoroformate.
ꢀ
C
2007 Wiley Periodicals, Inc. Heteroatom Chem 18:108–
RESULTS AND DISCUSSION
115, 2007; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20267
Interaction of methylcyanoacetate and malononi-
trile with 2 at the presence of triethylamine in CH3CN
proceeded very smoothly with the formation of al-
most black powder. Crystallization of the latter in
appropriate solvent resulted in compounds 4a,b. Ap-
parently, at the first stage of the reaction (Scheme 1),
ꢀ-complex 3 was formed. At the second stage, the
triethylamine molecule promoted decomposition of
ꢀ-complex 3 resulting in the formation of the stable
ion pairs 4a,b.
INTRODUCTION
Stable salts or zwitterion conjugates, i.e., negatively
charged moieties, for example, 4a,b and 9, have not
been described. Formation of the intermediate pos-
sessing the structure similar to that of the anion in
salts 4a,b was suggested solely from the IR spec-
The composition and the structure of com-
pounds 4a,b was established by the C, H, N analysis,
IR, NMR spectra. For 4a, X-ray diffraction study and
chemical transformations were performed. Com-
pound 4a was found to be a salt consisting of
[NHEt3]+ cations and organic anions.
Correspondence to: Yuri G. Gololobov; e-mail: Yugol@ineos.ac.
ru.
Contract grant sponsor: Russian Foundation for Basic
Research.
Contract grant sponsor: 04-03-32489.
2007 Wiley Periodicals, Inc.
c
ꢀ
108

Reactions of Carbanions with 2,4-Dinitrofluorobenzene Leading to Stable Heptatrienide Moieties 109
SCHEME 1
FIGURE 1 Structure and atom labeling of the anion of com-
pound 4a.
FIGURE 2 The dimeric crystal packing of the anions in com-
pound 4a.
Molecular structure of these anions is presented
in Fig. 1. The anions possess a nonplanar structure
with the dihedral angle between the ring and the
C(1) C(2) C(4) plane of 25.1◦. The torsion angles
C(4) C(2) C(1) O(5) and C(9) C(4) C(2) C(3) are
equal to 9.9(6)◦ and 15.0(4)◦, respectively. Although
one of the NO2 groups [N(3)O2] is coplanar with
the ring, other group [N(2)O2] is rotated around the
C(5) N(2) bond. The dihedral angles between the
NO2 and the ring planes are equal to 1.9◦ and 40.5◦,
respectively. In the anion, the negative charge on
atom C(4) as is evidenced from that fact that the
length of all C(4) bonds was found to exceed the
standard bond length including the olefin C(4) C(2)
bond. In the ring, the lengths of the other four
C C bonds [C(5) C(6), C(6) C(7), C(7) C(8), and
C(8) C(9)] are nearly identical (av. 1.371 A). The
C N and N O bond lengths are also standard
(Table 2).
The mode of the packing of anions and cations in
the crystals of salt 4a is of certain interest. We found
that the cation–anion pairs in salt 4a were assem-
bled in the discrete fashion. This can be explained by
the hydrogen bond between the cation Et3N+ H and
the carbonyl O(5) atom of the anion (the interatomic
likely due to weak attractive π–π stacking interac-
tions between them. The shortest distance between
˚
parallel rings was found to be of 3.51 A.
We found that salt 4a was a stable compound
(cf. [1]). The most reasonable explanation of this
fact is the relatively high acidity of the conjugated
CH-acid 5 that was formed upon acidification of the
triethylammonium salt 4a (Scheme 2).
In addition to 1a, b, other methyleneactive com-
pounds with sufficient CH-acidity (e.g., 3-methyl-1-
phenyl-2-pyrazoline-5-on, etc.) may form polyconju-
gated compounds similar to compounds 4a, 4b upon
their reaction with 2 at the presence of triethylamine.
A detailed discussion of this topic will be presented
in our upcoming publications.
Transformation of ꢀ-complex 3 into 4 discussed
above occurs due to relatively high mobility of
the H-atom attached to the α-C atom in 3. It
would be interesting to know what might happen to
˚
˚
˚
distances: N· · ·O 2.822(4) A, H· · ·O 1.88 A; the an-
gle: N H· · ·O 158◦). Moreover, the rings were found
to form the centrosymmetrical dimers (Fig. 2); most
SCHEME 2
Heteroatom Chemistry DOI 10.1002/hc

110 Gololobov et al.
ꢀ-complex like 3, if instead of labile C H bond, the
α-C atom bore loosely bound C(O)OEt group (cf. [2]).
To construct such ꢀ-complex, we reacted 2 with zwit-
terion 6. We assumed that 6 would react with 2 in
dual way: according to the traditional scheme with
the formation of the new aromatic system 8 (direc-
tion “a”); and with the rupture of the weak C C
bond between the α-C atom and the C(O)OEt moi-
ety (the CN group weakens the C C(O)OEt bond in
σ-complex 7) (direction “b”). The latter should yield
ethylfluoroformate and zwitterion of a new type 9.
Our experiments showed that at 10–20◦ and a 20% so-
lution of the starting materials in CH3CN or CH2Cl2,
direction “b” became dominant, resulting in almost
black crystals of zwitterion 9 (preliminary informa-
tion [3]) (Scheme 3). Formation of phosphonio hep-
tatrienide zwitterion 9 seems to include intramolec-
ular or intermolecular attack of the C(O)OEt group
by the fluorine atom. Structure of ethylfluorofor-
mate was established by IR and NMR (1H, 19F) spec-
troscopy. The lengthening of the conjugation chain
due to the attachment of the CN-group to the car-
bon atom bearing the double bond is, most likely,
the driving force of the process.
10 (Scheme 4). Low melting 8 was transformed into
crystalline compound 11 by substitution of the fluo-
ride ion to the iodide ion.
Physicochemical methods confirmed the compo-
sition of compound 9. The structure of zwitterion 9
was established by X-ray diffraction. UV/Vis spec-
troscopy in acetone showed ꢁmax = 478 nm and
ε = 34, 000. The IR spectrum showed the intensive
band at 2158 cm−1. This suggests a high degree of
interactions between the CN group and the negative
charge. The IR spectrum also contained the inten-
sive band at 1589 cm−1, which can be the result of
the formations of a system of the conjugated bonds.
In the proton-NMR spectra, the ring protons of zwit-
terion 9 were shifted upfield in comparison with aro-
matic protons of compound 11 due to the negatively
charged heptatriene fragment.
X-ray studies of compound 9 confirmed the
zwitterionic nature of this compound (Fig. 3). The
molecule was found to contain a planar moiety
that consisted of the ring and the C(2) C(4) bond.
The angle between this moiety and the CN-group
is 10.9◦. The dihedral angle between the ortho-NO2
group [N(2) O(1) O(2)] and C(4) C(9) planes is
equal to 52.4◦. In contrast to the ortho-NO2 group,
the para-NO2 group [N(3) O(4) O(5)] and the ring
were found to be at the same plane. The C(5) C(6)
and C(8) C(9) bonds are shorter than the other four
At a reduced temperature (−15 to −20◦C) and
concentration of the reagents of 3–5%, ꢀ-complex 7
formed in the reaction was transformed mostly ac-
cording to the traditional scheme of aromatic substi-
tution, i.e., according to direction “a”. This resulted
in the formation of the phosphonium fluoride 8 that
was in equilibrium with isomeric fluorophosphorane
˚
(av. 1.370 and 1.418 A, respectively). In other words,
the C C bond length distribution in the ring (Table
2) showed a considerable contribution of the quinoid
SCHEME 3
SCHEME 4
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Carbanions with 2,4-Dinitrofluorobenzene Leading to Stable Heptatrienide Moieties 111
˚
form. The C(7) N(3) (1.421(2) A) bond is shorter
˚
than the C(5) N(2) (1.456(2) A) bond. On the con-
trary, the N(3) O bond is shorter than the N(2) O
˚
bond (av. 1.229 and 1.240 A, respectively). Accord-
ing to the literature data [4], in 1,3-dinitrobenzene
both the nitro groups are coplanar with the phenyl
ring and there is no contribution of the quinoid form
to the geometry of the phenyl ring. The length of all
˚
the C N bonds in 1,3-dinitrobenzene is 1.475 A. In
˚
9, the P C bond lengths (av. 1.827(2) A) are close to
the bond lengths [5] in cation Pri4P+.
Thus, the data obtained unequivocally point out
to a bipolar character of the molecule 9: negative
charge is delocalized over the C(6) C(7)(NO2)C(8)
fragment. The role of the para-NO2 group in such
a delocalization was confirmed by the formation of
the intermolecular hydrogen bonds O(3)· · ·H C(1)
(the O(3)· · ·H and O(3)· · ·C(1) interatomic distances
˚
are equal to 2.17 and 3.055(2) A, respectively, the
O(3)· · ·H C(1) angle is 150◦) (Fig. 4).
NMR spectra showed that in DMSO-d6, acetone-
d6, or the CDCl3/DMSO-d6 mixture, zwitterion 9 ex-
isted as a mixture of geometrical isomers (Scheme 6);
the isomer ratio depended on the nature of the sol-
vent (Table 3).
In view of the fact that, according to our
RCA data, in the crystalline state phosphonio
FIGURE 3 X-ray structure and atom labeling of the anion of
compound 9.
FIGURE 4 The intermolecular hydrogen bonds in crystals of compound 9.
Heteroatom Chemistry DOI 10.1002/hc

112 Gololobov et al.
At this moment, it is difficult to say what contri-
bution of forms A and B exists in real electron states
of compounds 4 and 9. The IR and UV spectra sug-
gest that 4 and 11 possess similar delocalization of
negative charges (for 4a: νCN = 2178 cm−1, λmax = 487
nm, ε = 34,300; for 9: ꢄCN = 2160 cm−1, λmax = 478,
ε = 34,000). However, RCA data suggest much more
pronounced contribution of the heptatriene form in
compound 9 (see lengths of the bonds in Table 2).
Dark-cherry solution of zwitterion 9 in acetone
was instantaneously decolorized by hydrogen chlo-
ride in ether. Under basic conditions, CH-acid 12
again turned into colored zwitterion 9 (Scheme 6).
In this paper, we report the first examples of nu-
cleophilic aromatic substitution reactions of fluorine
atom in a highly electron deficient arenes, giving
stable organic salts or zwitterions with conjugated
SCHEME 5 Geometrical isomers of zwitterion 9.
heptatrienide zwitterion 9 existed in the cis-form,
we may assume that in the solution the cis-form of
9 also prevails. Most likely, isomer 9b is less sta-
ble due to steric effects of a bulky i-Pr3P+ group
(Scheme 5).
The structure of the anion in 9 resembles
the structure of a similar fragment in compound
4 (Table 1), but the heptatriene structure is not
observed in 4. The term “heptatriene form” is
rather subjective. Negatively charged moieties of
compounds 4 and 9 can be presented as su-
perposition of two extreme mesomeric forms A
and B.
TABLE 1 Crystal Data and Structure Refinement Parameters for 4 and 9
4
9
Formula
C16H22N4O6
366.38
Red plate
C18H26N3O4P
379.39
Black prism
0.35 × 0.40 × 0.50
Monoclinic
Molecular weight
Crystal color, habit
Crystal size (mm)
Crystal system
Space group
0.30 × 0.25 × 0.20
Triclinic
P-1
7.915(2)
10.344(3)
12.135(4)
96.21(3)
102.87(2)
106.47(2)
1413.2(9)
2
1.331
54
1.03
P21/c
8.511(2)
16.185(3)
13.806(3)
90
99.268(4)
90
1876.9(6)
4
1.343
58
1.75
15475
˚
a (A)
˚
b (A)
˚
c (A)
α (◦)
β (◦)
γ (◦)
3
˚
V (A )
Z
Dcalcd (g cm−3
2ꢂmax (◦)
)
Absorption coefficient ꢃ (Mo Kα) (cm−1
No. of reflections collect
)
4282
3876 (Rint = 0.0622)
1619
No. of independent reflections
No. of observed reflections (I > 2ꢀ(I ))
No. of parameters
4838 (Rint = 0.0470)
3065
254
235
R1 (on F for observed reflections)
0.0569
0.1332
0.0519
0.0995
WR2 (on F2 for all reflections)
Weighting scheme
a
b
w−1 = ꢀ 2(Fo2) + (aP)2 + bP, P = (1/3)(Fo2 + 2Fc2)
0.0025
1.3250
388
0.0117
1.5015
808
F (0 0 0)
Goodness-of-fit
Largest differential peak and hole (e A
0.986
0.248 and −0.256
0.996
0.386 and −0.224
−3
˚
)
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Carbanions with 2,4-Dinitrofluorobenzene Leading to Stable Heptatrienide Moieties 113
˚
EXPERIMENTAL
TABLE 2 Selected Bond Lengths (A), Bond Angles, and
Dihedral Angles α (◦) of Anion 4 and Molecule 9
The NMR spectra were obtained on a Bruker spec-
trometers Avance AMX-400 (400.1 MHz (1H), 162.0
MHz (31P)) and Avance AMX-300 (282.4 MHz (19F)
relative to CFCl3, 121.5 MHz (31P)), δ (ppm), mul-
tiplicity, number of protons, reference of protons,
J (Hz). The IR spectra were recorded on a Nico-
let IR-Fourier spectrometer Magna-IR-750 (ν/cm−1).
UV/Vis spectra were recorded on a Carl Zeiss spec-
trometer Specord M-40 (nm). The reactions were car-
ried out under dry N2.
4
11
C(2) C(4)
C(4) C(5)
C(5) C(6)
C(6) C(7)
C(7) C(8)
C(8) C(9)
C(9) C(4)
C(5) N(2)
C(7) N(3)
C(2) C(3)
C(3) N(1)
N(2) O(1)
N(2) O(2)
N(3) O(3)
N(3) O(4)
C(1) C(2)
C(1) P(1)
1.429(4)
1.410(4)
1.377(4)
1.364(5)
1.373(5)
1.369(5)
1.428(4)
1.470(4)
1.460(4)
1.410(5)
1.149(5)
1.219(4)
1.231(3)
1.227(4)
1.229(4)
1.430(4)
–
1.398(3)
1.447(3)
1.370(3)
1.387(3)
1.402(3)
1.371(3)
1.436(3)
1.456(2)
1.421(2)
1.417(3)
1.145(2)
1.226(2)
1.232(2)
1.237(2)
1.244(2)
1.516(2)
1.824(2)
Triethylammonium (Cyano-methoxycarbonyl-
methylidine)-2, 4-dinitrocyclo-hexadienide 4a
Triethylamine (0.69 mL, 5.0 mmol) was added drop-
wise, with stirring, to the mixture of methylcyanoac-
etate (0.5 g, 5.0 mmol), 2 (0.93 g, 5.0 mmol), and
CH3CN (1 mL). After 3 days, ether was added and
the crystalline powder was filtered off. Yield 1.10 g
(60%), m.p. 103–105◦C (ether–acetone 1:1). Calcd.
for C16H22N4O6: C, 52.46; H, 6.01; N, 15.30. Found:
C, 52.21; H, 6.00; N, 15.17. 1H NMR (CDCl3): 1.12 (t,
9H, CH3CH2N, 3 JHH = 7.3 Hz), 3.00 (q, 6H, CH3CH2N,
3 JHH = 7.3 Hz), 3.47 (s, 3H, CH3O), 7.59 (d, 1H,
P(1) C(Et)
C(4) C(2) C(3)
C(5) C(4) C(9)
C(6) C(7) C(8)
α1(N(2)O2)
α2(N(3)O2)
–
1.821(2), 1.822(2), 1.836(2)
122.1(2)
118.5(3)
113.7(3)
121.3(3)
40.5
113.2(2)
120.5(2)
54.5
2.4
1.9
3
3
Hꢅ, JHαHꢆ = 9.3 Hz), 7.97 (dd, 1H, Hꢆ, JHꢆHꢅ = 9.3
Hz,4 JHꢆHꢆ = 2.5 Hz), 8.27 (d, 1H, Hꢆ , JHꢆ Hꢆ = 2.5
Hz), 9.10–11.10 (s broad, 1H, +NH). IR (CDCl3): 1305
(NO2), 1658 (C(O)OMe), 2178 (CN), 2702 (+NH). UV
(acetone): 487 (ε = 34, 300). 13C NMR (CDCl3): 8.53
(CH3CH2N), 46.52 (CH3CH2N), 50.34 (MeO), 60.94
(C1Ar), 121.78, 125.02, 126.72 (CHAr), 125.39 (CN),
138.15, 138.18 (C NO2), 141.86 (C C1Ar), 169.01
(CO).
4
ꢁ
ꢁ
ꢁ
SCHEME 6
anions. This extends our knowledge of the proper-
ties of σ-complexes, and enables us to synthesize new
perspective synthones. Formation of ethylfluorofor-
mate (Scheme 3) allows us to suggest that this reac-
tion is a special case of a new class of transforma-
tions, i.e., such transformations in which the devel-
opment of the heptatriene systems is the result of the
formation of a new olefin bond because of ethylfluo-
roformate elimination. Most likely, the fluorine atom
can be combined not only with the C(O)OEt group
during ꢀ-complex decomposition (e.g., complex 7),
but also with other electrophilic moieties having con-
siderable affinity to the fluorine atoms, for exam-
ple, Me3Si , Ph2P(O) , etc. This suggests that the
formation of highly conjugated systems in 4 and 9
are special cases of novel general reactions involving,
on the one hand, various electrophilic fluoroaro-
matic compounds and, on the other hand, methyle-
neactive compounds and phosphorus-containing
zwitterions. Our preliminary experiments have con-
firmed this key conclusion. In details, we will discuss
them in the follow-up publications.
Triethylammonium (Dicyanomethylidine)-2,4-
dinitrocyclohexadienide 4b
Triethylamine (0.60 mL, 4.3 mmol) in ether (10
mL) was added dropwise, with stirring, to the mix-
ture of malononitrile (0.3 g, 4.5 mmol), 2 (0.84 g,
4.5 mmol), and ether (20 mL). After 10 min, ether was
removed in vacuo and the crystalline powder was
crystallized from toluene. Yield 0.35 g (23%), m.p.
84–86◦C. Calcd for C15H19N5O4: C, 54.05; H, 5.70; N,
1
21.02. Found: C, 54.03; H, 5.75; N, 20.90. H NMR
3
(CDCl3): 1.39 (t, 9H, CH3CH2N, JHH = 7.3 Hz), 3.18
(dq, 6H, CH3CH2N, 3 JHH = 7.3 Hz, 4 JHH = 2.4 Hz), 7.34
(d, 1H, Hꢅ, 3 JHꢅHꢆ = 8.5 Hz), 7.94 (d, 1H, Hꢆ, 3 JHH = 8.5
+
ꢁ
Hz), 8.49 (s, 1H, Hꢆ ), 8.92 (s, 1H, NH). IR (CDCl3):
1321 (NO2), 2160, 2194 (CN), 2736 (+NH). UV (ace-
tone): 464 (ε = 33, 400).
Heteroatom Chemistry DOI 10.1002/hc

114 Gololobov et al.
TABLE 3 NMR Spectra of the Geometrical Isomers of Zwitterion 9 in DMSO-d6a
Isomers
cis-isomer 9a, 83.5%
trans-isomer 9b, 16.5%
31P
(CH3)2CH
44.52
44.68
3
1.38 (dd, 18H, 3 JPH = 15.6 Hz, 3 JHH = 7.2 Hz)
1.45 (dd, 18H, JPH = 17.6 Hz,
3 JHH = 7.2 Hz)
(CH3)2CH
CH2P+
Hꢅ
2.88 (dsept, 3H, 2 JPH = 12.4 Hz, 3 JHH = 7.2 Hz)
3.38 (m, 3H)
3.74 (d, 2H, 2 JPH = 12.1 Hz)
3.20 (d, 2H, 2 JPH = 12.8 Hz)
7.12 (d, 1H, 3 JH H = 7.5 Hz)
7.72 (d, 1H, 3 JH H = 6.9 Hz)
α
β
α
β
3
Hꢆ
7.54 (dd, 1H, 3 JH H = 7.5 Hz, 4 JH H = 2.1 Hz)
7.97 (dd, 1H, JH H = 6.9 Hz,
ꢁ
β
α
β
β
α
β
4 JH H = 1.8 Hz)
ꢁ
β
β
Hꢆ
8.32 (d, 1H, 4 JH
= 2.1 Hz)
8.59 (d, 1H, 4 JH
= 1.8 Hz)
ꢁ
ꢁ Hβ
ꢁ Hβ
β
β
aRatio of 9a:9b in acetone-d6 7:4, in the 1:1 mixture of CDCl3–DMSO-d6 1.5:1.
of 6 (1.0 g, 3.5 mmol) in CH2Cl2 (75 mL) at −15◦C.
After 2 days, the solvent was removed in vacuo.
The residue (oil) represented a mixture of 8, 90%
(31P NMR (CDCl3): 46.16; 19F NMR (CDCl3): −106.07)
and 10, 5% (31P NMR (CDCl3): −15.66 (d, JPF = 646
Hz); 19F NMR (CDCl3): −62.13 (d, JPF = 646 Hz)) and
uncertain compounds (5%).
Methyl [Cyano-(2,4-dinitrophenyl)]ethanoate 5
The solution of hydrogen chloride in dry ether was
added dropwise, with stirring, to the suspension
of salt 4 (0.05 g, 0.14 mmol) in ether. Light crude
product formed upon stirring was reprecipitated
twice with petroleum ether from acetone solution.
Removal of the solvent under vacuo produced an
oil product. Yield 0.03 g (81%). IR (CDCl3): 1354,
1
1541 (NO2), 1758 (C(O)OMe), 2253 (CN). H NMR
[2-Cyano-2-ethoxycarbonyl-2-(2,4-dinitrophe-
nyl)ethyl]triisopropylphosphonium Iodide 11
(CDCl3): 3.84 (s, 3H, CH3O), 5.76 (s, 1H, CH), 8.02–
8.96 (m, 3H, HAr).
The solution of NaI (0.52 g, 3.5 mmol) in acetone
was added to the solution of 8 in acetone (1.65 g,
3.5 mmol). After filtration, the solvent was removed
in vacuo. The residue was crystallized from ace-
tone. Yield 0.45 g (22%), m.p. 132–133◦C. Calcd. for
C21H31N3PO6I: C, 43.52; H, 5.35; N, 7.25; P, 5.35.
Found: C, 43.68; H, 5.35; N, 7.27; P, 5.22. 31P NMR
(1-Cyano-2-triisopropylphosphonioethylidene)-2,
4-dinitrocyclohexadienide 9
Compound 2 (3.26 g, 17.5 mmol) in CH2Cl2 (25 mL)
was added dropwise, with stirring, to the solution of
zwitterion 6 (5.0 g, 17.5 mmol) in CH2Cl2 (75 mL) at
3◦C. The reaction mixture was left for 2 days and then
petroleum ether (100 mL) was added. The residue
was filtered off and washed with CCl4. Dark crystals
(2.27 g) were rinsed with cold acetone several times.
Yield 36%, m.p. 158–159◦C. Calcd. for C18H26N3O4P:
C, 56.99; H, 6.86; N, 11.08. Found: C, 56.97; H, 6.98;
N, 11.07. IR (Nujol mull): 1320 (NO−2 ), 1592 (conju-
gated heptatriene system), 2160 (CN). UV (acetone):
478 (ε = 34, 000). For the NMR spectra of compound
9 see Table 3.
1
(CDCl3): 46.89 ppm. H NMR (CDCl3): 1.20 (t, 3H,
3
CH3CH2, JHH = 7.2 Hz), 1.59 (dd, 18H, (CH3)2CH,
3 JHH = 7.2 Hz), 3.51 (m, 4H, (CH3)2CH, CHAHB),
3
4.26 (q, 2H, CH3CH2O, JHH = 7.2 Hz), 4.81 (dd, 1H,
CHAHB, 2 JHP = 11.8 Hz, 2 JHH = 4.1 Hz), 8.73 (dd, 1H,
Hβ, 3 JH = 7.2 Hz,4 JH
= 2.8 Hz), 8.91 (d, 1H, Hβ ,
ꢁ
H
α
H
ꢁ
β
β
β
4 JH
= 2.8 Hz), 9.01 (d, 1H, Hα, 3 JH = 7.2 Hz). IR
H
H
β
ꢁ
α
β
β
(CDCl3, ν/cm−1): 1348, 1542 (NO2), 1752 (COOEt),
2206 (CN).
The filtrate was distilled off. The presence
of ethylfluoroformate in the filtrate was proven
by the NMR and IR spectra. 19F NMR (CDCl3):
[2-Cyano-2-(2,4-dinitrophenyl) ethyl]-
triisopropylphosphonium Chloride 12
1
−17.02, s (broad). H NMR (CDCl3): 1.33 (dt, 3H,
CH3CH2O, 3 JHH = 9.2 Hz, 5 JHF = 1.2 Hz), 4.29 (dq, 2H,
CH2O,3 JHH = 9.2 Hz, 4 JHF = 0.8 Hz). IR (CH2Cl2): 1824
(COOEt).
The solution of hydrogen chloride in dry ether was
added to a dark-cherry solution of zwitterion 9 (0.05
g, 0.13 mmol) in CH2Cl2 (30 mL) until acid reaction
of the reaction mixture. Immediate discoloration of
the reaction solution was observed. The solvent was
distilled off and the obtained crude product was
crystallized from petroleum ether–acetone (2:1) mix-
ture. Product 12 was obtained as a powder (0.04 g).
Reaction of 2 with Zwitterion 6
Compound 2 (0.65 g, 3.5 mmol) in CH2Cl2 (25 mL)
was added dropwise, with stirring, to the solution
Heteroatom Chemistry DOI 10.1002/hc

Reactions of Carbanions with 2,4-Dinitrofluorobenzene Leading to Stable Heptatrienide Moieties 115
Yield 83%, m.p. 167–169◦C. 1H NMR (CDCl3):
were performed on using the SHELXTL software [6].
Atomic coordinates, bond lengths, bond angles, and
thermal parameters have been deposited at the Cam-
bridge Crystallographic Data Centre (CCDC), depo-
sition numbers CCDC 297193 (4a), CCDC 270207
(9). These data can be obtained free of charge via
3
3
1.57 (dd, 18H, (CH3)2CH, JPH = 23.9 Hz, JHH = 7.0
2
Hz), 3.44 (dsept, 3H, (CH3)2CH, JPH = 13.4 Hz,
3 JHH = 7.0 Hz), 3.60 (m, 1H, CHAHBP+), 3.87 (dd,
3
1H, CHAHBP+,2 JPH = 25.3 Hz, JHH = 11.4 Hz), 5.67
3
(d, 1H, CHCH2P+, JHH = 11.4 Hz), 8.57 (d, 1H, Hꢅ,
3 JH = 7.2 Hz), 8.85 (d, 1H, Hꢆ , 4 JH
= 1.7 Hz),
ꢁ
http://www.ccdc.cam.uk/conts/retrieving.html
(or
H
ꢆ
H
ꢆ
ꢁ
ꢅ
ꢆ
9.20 (d, 1H, Hꢆ, JH = 7.2 Hz). 31P NMR (CDCl3):
3
from the CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44-1223-335-033; or e-mail:
deposit@ccdc.cam.ac.uk). Any request to the CCDC
for data should quote the full literature citation and
CCDC reference numbers.
H
ꢅ
ꢆ
43.74.
Single-Crystal X-ray Structure Determination
of 4a, 9
Single-crystal X-ray diffraction experiments were
carried out with a CAD4 Enraf-Nonius diffractome-
ter at 293 K for 4a and a Bruker SMART 1000
CCD area detector at 120 K for 9 using graphite
ACKNOWLEDGMENT
We thank Dr. Mikhail Gololobov for his advice and
helpful discussions.
˚
monochromated Mo Kα radiation (ꢁ = 0.71073 A).
REFERENCES
The structures were solved by direct method
and refined by the full-matrix least-squares against
F2 in anisotropic (for non-hydrogen atoms) and
isotropic (for H atoms) approximation. The H(C)
atom positions were calculated, the H(N) hydro-
gen atom in 4a was located from the difference
Fourier synthesis. All hydrogen atoms were refined
in isotropic approximation in riding model with the
Uiso(H) parameters equal to 1.2Ueq(X), for methyl
groups equal to 1.5Ueq(Ci), where U(X) and U(Ci)
are the equivalent thermal parameters of the atoms
to which corresponding H atoms are bonded.
[1] Leffek, K. T.; Tremaine, P. H. Can J Chem 1971, 49,
1979.
[2] Gololobov, Yu. G.; Galkina, M. A.; Kuzmintseva, I.
Yu.; Petrovskii, P. V. Russ Chem Bull 1998, 47(9),
1878.
[3] Gololobov, Yu.; Linchenko, O. A.; Petrovskii, P. V.;
Starikova, Z. A.; Garbuzova, I. A. Russ Chem Bull
2005, 54(10), 2471–2472.
[4] Wojcik, G.; Mossakowska, I.; Holband, J.;
Bartkowiak, W. Acta Crystallogr, Sect B: Struct
Sci 2002, 58, 998.
[5] Schmidbaur, H.; Schier, A.; Frazao, C. M. F.; Muller,
G. J Am Chem Soc 1986, 108, 976.
[6] Sheldrick, G. M. SHELXTL-97, Version 5.10; Bruker
AXS Inc.: Madison, WI, USA.
Crystal data and structure refinement parame-
ters for 4a and 9 are given in Table 1. All calculations
Heteroatom Chemistry DOI 10.1002/hc