Reaction of nitroalkanes with polyfluoroaromatic compounds

Article abstract of DOI:10.1016/j.jfluchem.2012.09.004

Nitromethane and nitroethane in the presence of DBU attack preferentially the para position of pentafluorobenzonitrile and methyl pentafluorobenzoate to give the addition products in good yield. The resulting nitro compounds can be converted to tetrafluorotoluene or ethyl benzene derivatives by tri-n-butyltin hydride. TiCl₃ solution neatly transforms the nitroethyl compounds into corresponding ketones. With a base, the nitro compounds can be used to extend chain length using Michael acceptors like ethyl acrylate and acrylonitrile.

Full text of DOI:10.1016/j.jfluchem.2012.09.004

Journal of Fluorine Chemistry 144 (2012) 33–37
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Reaction of nitroalkanes with polyfluoroaromatic compounds
1
*
R. Vaidyanathaswamy , K. Radha, M. Dharani , T.S. Raguraman, Rajdeep Anand
Projects and R&D, SRF Ltd., Manali Industrial Area, Manali, Chennai 600068, India
A R T I C L E I N F O
A B S T R A C T
Article history:
Nitromethane and nitroethane in the presence of DBU attack preferentially the para position of
pentafluorobenzonitrile and methyl pentafluorobenzoate to give the addition products in good yield. The
resulting nitro compounds can be converted to tetrafluorotoluene or ethyl benzene derivatives by tri-n-
butyltin hydride. TiCl3 solution neatly transforms the nitroethyl compounds into corresponding ketones.
With a base, the nitro compounds can be used to extend chain length using Michael acceptors like ethyl
acrylate and acrylonitrile.
Received 6 June 2012
Received in revised form 24 August 2012
Accepted 8 September 2012
Available online 25 September 2012
Keywords:
ß 2012 Elsevier B.V. All rights reserved.
Nucleophilic aromatic substitution
Pentafluorobenzonitrile
Methyl pentafluorobenzoate
Reduction with tri-n-butyltin hydride
Nef reaction with TiCl3
Michael reaction
1. Introduction
Nitroalkanes are versatile reagents in that, by forming the
carbanion
a- to the nitro group, strong nucleophiles are produced
Polyfluoroaromatic compounds by virtue of the presence of
large number of fluorine atoms undergo nucleophilic aromatic
substitution (SNAr) [1] in contrast to normal aromatic compounds
which give rise to substitution products arising out of electrophilic
substitution. This unique property of polyfluoroaromatic systems
has been studied thoroughly with variety of nucleophiles having
oxygen [2], nitrogen [3] or sulfur [4] atoms and many such
reactions have been exploited as a part of synthetic strategy to
make substitution products with the above nucleophiles. However,
the number of such reactions with carbon nucleophiles [5] is very
few though the formation of carbon–carbon bond by this
procedure should be synthetically more rewarding.
which can initiate SNAr reactions. Moreover, the products formed
from these reactions can be transformed into other useful
compounds on one hand and on the other the nitrogroup can be
utilized as a handle for effecting new nucleophilic reactions [8].
This paper describes in brief the reaction of nitromethane and
nitroethane with pentafluorobenzonitrile (PFBN) and methyl
pentafluorobenzoate (MPFB) to determine the regiospecificity of
such reactions. To the best our knowledge such reactions are
reported for the first time (see below). Some typical further
transformations are also described.
2. Results and discussion
SNAr reactions follow addition–elimination mechanism by the
intermediacy of Meisenheimer complex which has been proposed
in quite a few systems [6]. To form such a complex, a negative
charge stabilizing group like cyano, carbomethoxy or nitro is
required. Except for special reasons attributed to stabilization of
intermediates by any of these groups by incoming nucleophiles in
the ortho position, most of the reactions follow a pathway wherein
the predominant product is para directed. Many theories have
been put forward to explain this para selectivity [6,7].
Nitromethane in the presence of a strong organic base such as
DBU reacts with PFBN to provide a product mixture, the analysis of
which showed >97% para selectivity in ether (Scheme 1). Upon
isolation and recrystallization, the product could be purified
further. That the product obtained is para substituted is
ascertained by all spectral data, the most important being two
symmetrical signals of equal intensity in the 19F NMR spectrum.
Similar results were obtained for nitromethane addition to MPFB
and nitroethane to both substrates (Scheme 1). These results are in
stark contrast to the results reported recently by Sandford group,
wherein monoaryl addition product could not be isolated [9].
Perhaps in the pyridine derivative benzyl proton being more acidic
deprotonation occurs readily forcing into react with another
pyridine nucleus.
* Corresponding author. Tel.: +91 44 25941745; fax: +91 44 25943017.
E-mail address: rvaidyanatha@srf.com (R. Vaidyanathaswamy).
1
A part of this work was submitted as M.Sc. thesis of M. Dharani, Stella Maris
College, University of Madras, Chennai, India (2009).
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jfluchem.2012.09.004

34
R. Vaidyanathaswamy et al. / Journal of Fluorine Chemistry 144 (2012) 33–37
X
R
X
(nBu)3SnH
V
CN
H
F4
VI CN
CH3
H
VII CO2Me
VIII CO2Me CH3
X
F
X
CH2R
X
F
F
F
F
DBU
F4
XI
CN CH3
R-CH2-NO2
TiCl3
XIII CO2Me CH3
F4
R
NO2
COR
OH OH
I(X=CN,R=H)
II(X=CN,R=CH3)
TiCl3
X
C
H
C
H
X
III(X=CO2Me,R=H)
IV(X=CO2Me,R=CH3)
F4
F4
XII
X=CO2Me
X
F4
CH2=CH-EWG
X=CN
NO2
CH2CH2-EWG
EWG=CO2Me(XIV),CN(XV)
Scheme 1.
Since, many nucleophilic reactions are affected by the solvent
intermediate as other methods of preparation of this compound
involve several steps [10].
polarity, we investigated the selectivity and extent of reaction in
three solvents namely acetonitrile, THF and benzene. The results
with PFBN and nitromethane showed that the selectivity to para
position is not influenced by the polarity of the solvent (range 2.5–
4.5% ortho).
Next we attempted Nef reaction [8]. In basic medium, KMnO4/
MnSO4/KOH did convert I to the corresponding aldehyde (IX) albeit
in low yield (<11%). Other reagents in basic medium did not
improve the results [11,12]. Most likely, the arylnitro compounds
are susceptible to further addition of hydroxyl group in the ortho
position in the basic medium resulting in low yield.
Nef reactions can be done in acid medium also using TiCl3 as a
reagent. This gave some surprising results with primary nitro
compound III. Instead of the expected aldehyde, III underwent
further reduction to provide a mixture of products including a
pinacol. We envisage that the mechanism of formation of pinacol is
through the intermediate aldehyde. Being adjacent to a highly
electronegative group this aldehyde accepts one more electron to
a
-Aryl nitroalkanes are versatile intermediates [8a]. Reduction
with tri-n-butyltin hydride afforded the corresponding methyl or
ethyl aryl compounds (V–VIII) in very good yield. In general, this
free radical mediated reaction is facile only with secondary and
tertiary nitro compounds. In this case, the presence of highly
electronegative aryl ring perhaps facilitates the removal of even
primary nitrogroup easily. It is worth noting that V is an important
intermediate for the synthesis of tefluthrin, an insecticide. This
procedure is a clean laboratory preparative method for this
COOCH
3
COOCH
3
COOCH
3
F
F
F
F
F
F
F
F
F
F
TiCl
TiCl
e transfer
+
3
3
H
-
XII
F
F
.
-
CH-O
CH NO
2
2
CHO
Scheme 2.

R. Vaidyanathaswamy et al. / Journal of Fluorine Chemistry 144 (2012) 33–37
35
give a radical anion, which upon dimerization and subsequent
protonation provides the pinacol [13] (Scheme 2). In the case of
secondary nitro compounds, the ketones were obtained in
excellent yield.
With DBU as a base, I adds on to both acrylonitrile and ethyl
acrylate smoothly to provide the corresponding Michael addition
products as shown in Scheme 1.
9.9 Hz, 3 and 5). EI-MS (70 eV) 202 [(MꢀNO2)+ (100)]. CI-MS 249
[(M+H)+ (100)], 202 [(MꢀNO2)+ (68)].
Satisfactory HRMS could not be obtained for this compound as
it degrades under the ESI condition but on reduction with TBTH
and reaction with TiCl3 it provides VI and XI, respectively, both of
which have satisfactory HRMS data.
All the new products obtained were confirmed by spectral data.
4.3. Reaction of methyl pentafluorobenzoate (MPFB) with
nitromethane (III)
3. Conclusions
To a solution of ether (50 ml) and DBU (7.61 g, 0.05 ml) at
ꢀ10 8C was added dropwise nitromethane (3.05 g, 0.05 mol) in
25 ml ether. After half an hour stirring, MPFB (5.90 g, 0.025 mol)
dissolved in 25 ml of ether was added dropwise. Stirring was
continued for 1 h more at the same temperature. After this period,
dil. HCl was added, ether layer was separated, aqueous layer was
extracted with ether and combined ether solution was washed
with sodium bicarbonate solution till neutral, dried and solvent
evaporated. Applying vacuum to the residue, provided a viscous
liquid which upon refrigeration solidified. This was crystallized
from cold methanol at 4 8C, m.p. 30–31 8C. Yield: 5 g (75%). IR
Nitromethane and nitroethane under basic condition add to
pentafluorobenzonitrile and methyl pentafluorobenzoate predom-
inantly to the para position. The nitrocompounds so formed can be
transformed into variety of products by conversion of the
nitrogroup. They also serve as versatile intermediates for extension
of chain length through Michael reaction.
4. Experimental details
1H, 19F and 13C NMR were recorded in Bruker A VIII 500 MHz
spectrometer. For 1H and 13C NMR TMS and 19F CFCl3 were used as
internal standards. Analysis in GC–MS and GC were performed in
Agilent instruments 5973 and 6890, respectively. IR was recorded
in Perkin Elmer spectrum one FTIR spectrometer.
All solvents and chemicals were purified by standard proce-
dures. PFBN is a commercial product of SRF with 99.7% purity (GC).
MPFB was prepared from pentafluorobenzoic acid and methanol
and distilled prior to use (purity 99.5%).
(Neat) 1744, 1570, 1491, 1373 cmꢀ1
4.01 (3H, s, –OCH3), 5.66 (2H, t, JHF = 1.5 Hz, –CH2–). 19F NMR
(470.4 MHz, CDCl3)
. d
1H NMR (500 MHz, CDCl3)
d
ꢀ138.3 (dd, JF–F = 24.9 and 15.5 Hz, 2 and 6),
ꢀ139.9 (dd, 25.0 and 16.0 Hz, 3 and 5). EI-MS (70 eV) 236
[(MꢀOCH3)+ (14)], 221 [(MꢀNO2)+ (100)]. CI-MS 268 [(M+H)+
(42)], 221 [(MꢀNO2)+ (100)]. HR-MS 290.0053 [calculated for
C9H5NO4F4Na = 290.0052].
4.4. Reaction MPFB with nitroethane (IV)
4.1. Reaction of pentafluorobenzonitrile (PFBN) with nitromethane (I)
Use of nitroethane in the place of nitromethane in the above
procedure provided a solid which was recrystallized from cold
methanol, m.p. 59–60 8C. Yield: 5.69 g (81%). IR (KBr): 1737, 1563,
In a three-necked flask having a mechanical stirrer, inlet for
nitrogen and an addition funnel was taken DBU (7.61 g, 0.05 mol)
and 50 ml of dry ether. This solution was cooled to 0 8C and
nitromethane (3.05 g, 0.05 mol) in 25 ml of ether was added
dropwise. Yellow color developed. After stirring for ten more
minutes, PFBN (4.83 g, 0.025 mol) in 25 ml of ether was added
dropwise (30 min). About the middle of the reaction, precipitate
appeared but the mixture could be stirred continuously. After
maintaining at 0 8C for half an hour more, dil. HCl was added till the
mixture became acidic. The ether layer was separated. The aqueous
layer was extracted twice with ether and combined with the ether
layer. The solution was washed with NaHCO3, dried over Na2SO4,
filtered and the solvent evaporated on a water bath kept at 45 8C,
then vacuum was applied to the residue to remove excess of
nitromethane. The semisolid mass obtained was recrystallized
from ethanol, m.p. 65–65.5 8C. Yield: 4.56 g (78%). IR (KBr) 2250,
1489, 1366 cmꢀ1
.
1H NMR (500 MHz, CDCl3)
d
5.87 (1H, q, JH–
H = 7.5 Hz, –CH–NO2), 4.02 (3H, s, –OCH3), 2.04 (3H, d, JH–
H = 7.5 Hz, CH3–CH55). 19F NMR (470.4 MHz, CDCl3)
d
ꢀ137.9
(dd, JF–F = 21 and 13 Hz, 2 and 6), ꢀ140.3 (dd, JF–F = 21 and 13 Hz, 3
and 5). EI-MS (70 eV) 250 [(MꢀOCH3)+ (6)], 235 [(MꢀNO2)+ (100)].
CI-MS 282 [(M+H)+ (47)], 235 [(MꢀNO2)+ (100)]. HR-MS 304.0205
[calculated for C10H7NO4F4Na = 304.0209].
4.5. Reaction of nitro compounds with tri-n-butyltin hydride
In a two necked flask having a magnetic stirrer, condenser and a
guard tube was taken I–IV (1 mmol). Tri-n-butyltin hydride
(340 mg, 1.17 mmol), catalytic amount of azobisisobutyronitrile
(32 mg) and benzene (5 ml) were charged and the mixture was
heated to reflux for two hrs. The contents were concentrated on a
rotary evaporator and the residue chromatographed on silica gel to
provide the corresponding alkyl compounds in good yield. GC
purity ranged from 98% to 99%.
1563, 1500, 1371 cmꢀ1
.
1H NMR (500 MHz, CDCl3)
d
5.70 (t,
J = 1.5 Hz, –CH2–). 19F NMR (470.4 MHz, CDCl3)
d
ꢀ130.5 (m, 2 and
6), ꢀ137.1 (m, 3 and 5) [refer to the numbering in Scheme 1]. EI-MS
(70 eV) 188 [(MꢀNO2)+ (100)]. CI-MS 235 [(M+H)+ (100)]. HR-MS
235.0132 [calculated for C8H3N2O2F4 = 235.0131].
V colorless liquid, b.p. 100–5 8C/20 mmHg. Yield: 113 mg (60%).
IR (Neat) 2249, 1496, 1302 cmꢀ1. 1H NMR (500 MHz, CDCl3)
d
2.40
ꢀ134.5 (m, 2
146.94
(t, JH–F = 2.0 Hz, CH3). 19F NMR (470.4 MHz, CDCl3)
d
4.2. Reaction of PFBN with nitroethane (II)
and 6), ꢀ140.2 (m, 3 and 5). 13C NMR (125 MHz, CDCl3)
d
(ddt, J = 241, 16.5, 3.5 Hz, C-2 and C-6), 144.97 (m, C-3 and C-5),
123.906 (t, J = 18.8 Hz, C-4), 107.64 (t, J = 3.5 Hz, CN), 91.69 (t,
J = 17 Hz, C-1), 8.43 (s, CH3). EI-MS (70 eV) 189 [M+ (100)], 188
[(MꢀH)+ (91)]. HR-MS 190.0274 [calculated for C8H4NF4
= 190.0280].
Use of nitroethane instead of nitromethane in the above
procedure gave a liquid product which was purified by chroma-
tography as it was contaminated with small amount of corre-
sponding ketone (silica gel, 50% benzene–hexane). The product
obtained was distilled in a bulb to bulb distillation assembly, b.p.
120–125 8C/1 mm. Yield: 4.21g (68%). IR (Neat) 2249, 1563, 1497,
VI colorless liquid, b.p. 100–5 8C/10 mmHg. Yield: 132 mg
(65%). IR (Neat) 2242, 1493, 1249, 1172 cmꢀ1. 1H NMR (500 MHz,
1360 cmꢀ1. 1H NMR (500 MHz, CDCl3)
1.82 (3H, d, JH–H = 7.2 Hz). 19F NMR (470.4 MHz, CDCl3)
(dd, JF–F = 17.9 and 10.3 Hz, 2 and 6), ꢀ138.0 (dd, JF–F = 17.9 and
d
5.64 (1H, q, JH–H = 7.2 Hz),
ꢀ130.7
CDCl3)
(470.4 MHz, CDCl3)
d
2.86 (2H, m, CH2), 1.29 (3H, t, J = 7.5 Hz, CH3). 19F NMR
d
d
ꢀ133.38 (dd, JF–F = 17.4 and 9.4 Hz, 2 and 6),
ꢀ141.83 (dd, JF–F = 17.4 and 9.4 Hz, 3 and 5). EI-MS (70 eV) 203 [M+

36
R. Vaidyanathaswamy et al. / Journal of Fluorine Chemistry 144 (2012) 33–37
(43)], 188 [(MꢀCH3)+ (100)]. HR-MS 204.0439 [calculated for
C9H6NF4 = 204.0436].
CDCl3) d d 190.3
2.66 (t, JH–F = 1.5 Hz). 13C NMR (125 MHz, CDCl3)
(s, CO), 147.3 (dddd, JC–F = 264, 16.6, 4.4, 1.9 Hz, C-2 and C-6), 143.4
(m, the major coupling constant is 250 Hz, C-3 and C-5), 125.1 (t,
J = 18.3 Hz, C-4), 106.8 (t, J = 3.6 Hz, CN), 96.3 (t, J = 17 Hz, C-1),
32.33 (d, J = 11.75 Hz, CH3). 19F NMR (470.0 MHz, CDCl3) ꢀ130.21
(dd, JF–F = 19.2 and 11.7 Hz, 2 and 6), ꢀ138.73 (dd, JF–F = 19.2 and
11.7 Hz, 3 and 5). EI-MS (70 eV) 217 [M+ (48)], 202 [(MꢀCH3)+
(100)], 174 [MꢀCOCH3 (36)]. CI-MS 218 [(M+H)+ (100)]. HR-MS
240.0040 [calculated for C9H3NOF4Na = 240.0048].
VII colorless liquid, b.p. 105–107/1 mmHg. Yield: 137 mg (62%).
IR (Neat) 1744, 1489, 1313 cmꢀ1. 1H NMR (500 MHz, CDCl3)
d
3.98
(3H, s, –OCH3), 2.33 (3H, t, JH–F = 2 Hz). 19F NMR (470.4 MHz,
CDCl3)
ꢀ140.8 (dd, JF–F = 20.2 and 11.8 Hz, 2 and 6), ꢀ142.35 (dd,
d
JF–F = 20.2 and 11.8 Hz, 3 and 5). EI-MS (70 eV) 222 [M+ (36)], 191
[(MꢀOCH3)+
(100)].
C9H7O2F4 = 223.0382].
HR-MS
223.0375
[calculated
for
VIII colorless liquid, b.p. 128–130 8C/1 mmHg. Yield: 160 mg
XIII A colorless liquid, b.p. 128–130 8C/1 mmHg. Yield: 175 mg
(68%). IR (Neat) 1745, 1487, 1306 cmꢀ1. 1H NMR (500 MHz, CDCl3)
(70%). IR (Neat) 2962, 1747, 1715, 1479, 1319 cmꢀ1 1H NMR
.
d
3.99 (3H, s, OCH3), 2.81 (2H, m, –CH2CH3), 1.26 (3H, t, J = 7.5 Hz, –
(500 MHz, CDCl3)
d 4.03 (3H, s, –OCH3), 2.66 (3H, t, J = 2 Hz, COCH3).
CH3). 19F NMR (470.4 MHz, CDCl3)
d
ꢀ140.5 (dd, JF–F = 20 and
19F NMR (470.4 MHz, CDCl3)
d
ꢀ137.72 (dd, J = 21.6, 13.5 Hz, 2 and
11.7 Hz, 2 and 6), ꢀ144.44 (dd, JF–F = 20 and 11.7 Hz, 3 and 5). EI-
MS (70 eV) 236 [M+ (30)], 205 [(MꢀOCH3)+ (100)]. HR-MS
237.0541 [calculated for C10H9O2F4 = 237.0539].
6), ꢀ140.5 (dd, J = 21.6 and 13.5 Hz, 3 and 5). EI-MS (70 eV) 250 [M+
(42)], 235 [(MꢀCH3)+ (100)]. CI-MS 251 [(M+H)+ (100)].
Satisfactory HRMS data for the intact compound could not be
obtained. Therefore 2,4-dinitrophenyl hyrazone of compound XIII
was prepared by standard procedure; recrystallized from metha-
nol, m.p. 120–121 8C. IR (KBr) 3302, 1748, 1620, 1596, 1506, 1474,
4.6. Nef reaction of I with KMnO4/MnSO4/KOH (IX)
To the nitro compound I (12 g, 0.05 mol) in methanol (200 ml)
kept between 0 and 5 8C under nitrogen atmosphere, was added
dropwise freshly made KOH solution (3.14 g, 0.056 mol). After a
few minutes stirring at 0 8C, a freshly made aq. KMnO4 (5.90 g,
0.037 mol) and MgSO4ꢁ7H2O (9.28 g, 0.038 mol) were added with
vigorous stirring. After stirring for an additional hour at 0 8C, the
mixture was filtered through a layer of celite and the filtrate
extracted with benzene (3ꢂ 50 ml). It was treated with brine and
the organic layer was separated and dried and distilled under
vacuum to remove the solvent. The residue slowly crystallized but
had a very low shelf stability and could not be characterized fully.
1338, 1314 cmꢀ1
.
1H NMR (500 MHz, CDCl3)
d
11.39 (1H, s, NH),
0
0
9.18 (1H, d, J = 2.5 Hz, H3 ), 8.38 (1H, dd, J = 9.5 and 2.5 Hz, H5 ),
7.99 (1H, d, J = 9.5 Hz, H6 ), 4.02 (3H, s, –OCH3), 2.47 (3H, s, –CCH3).
HR-MS 453.0434 [calculated for C16H10N4O6F4Na = 453.0434].
0
4.9. Reaction of I with ethylacrylate (XIV)
To a solution of I (234 mg, 1 mmol) in acetonitrile (5 ml) was
added ethylacrylate (110 mg, 1.1 mmol) and DBU (167 mg,
1.1 mmol) and stirred for 3 h at room temperature under N2
atmosphere. GC showed absence of starting material after this
period. This brown solution was diluted with ether, washed with
dil. HCl to remove the base and dried and purified by column
chromatography.
Yield: 1.14 g (11%). 1H NMR (500 MHz, CDCl3)
(70 eV) 203 [M+ (98)], 202 [(MꢀH)+ (100)].
d 10.34 (s). EI-MS
4.7. Nef reaction of III with TiCl3 (XII)
XIV slight amber colored viscous liquid, homogenous on HPLC.
Yield: 304 mg (91%). IR (Neat) 2987, 2250, 1732, 1566, 1497,
To a solution of 12% TiCl3 (12 ml) and ammonium acetate (3.0 g)
was added III (267 mg, 1 mmol) in THF (5 ml). The solution was
stirred for 3 h under nitrogen atmosphere. A violet colored slurry
was obtained. This was extracted with ether (5ꢂ 10 ml) and
washed with sodium bicarbonate solution till neutral. The solution
was dried, solvent evaporated and the residue was analyzed by
GC–MS. It showed a number of products. On keeping at RT, a solid
separated, which was recrystallized from methanol–benzene, m.p.
217–218 8C. Yield: 65 mg (27%). IR (Neat) 3507 (doublet), 1724,
1370 cmꢀ1. 1H NMR (500 MHz, CDCl3)
d 6.02 (1H, t, J = 7.0 Hz, –CH–
NO2), 4.17(2H, q,J = 7 Hz, –O–CH2–),3.04(1H, m,>CH–CHH*–), 2.60
(1H, m, >CH–CHH*), 2.47 (2H, m, –CH2–COO), 1.28 (3H, t, J = 7.0 Hz,
–CH2CH3). EI-MS (70 eV) 288 [(MꢀNO2)+ (30)], 260 [(MꢀCOOEt)+
(100)]. CI-MS 335 [(M+H)+ (100)], 288 [(MꢀNO2)+ (68)]. HR-MS
357.0470 [calculated for C13H10N2O4F4Na = 357.0474].
4.10. Reaction of I with acrylonitrile (XV)
1485, 1334, 1315 cmꢀ1
CH–OH), 4.00 (3H, s, –OCH3). 1H NMR (500 MHz, CD3CN)
(1H, dd, J = 4.0 and 2.0 Hz, CH–OH), 4.21 (1H, bt, OH), 4.00 (3H, s, –
OCH3) CD3CN (D2O shake), 5.41 (1H, s, –CH–), 3.95 (3H, s, –OCH3).
13C NMR (125 MHz, CD3OD)
160 (s, COOCH3), 145.4 (m, C-2 and
.
1H NMR (500 MHz, CD3OD)
d
5.52 (1H, s,
5.44
To a solution of I (234 mg, 1 mmol) in acetonitrile (5 ml) was
added acrylonitrile (79 mg, 1.5 mmol) and DBU (167 mg,
1.1 mmol) and reaction performed as above. The product was
isolated as an amber colored liquid after silica gel chromatography.
XV amber colored viscous liquid, homogenous on HPLC. Yield:
d
d
d
6), 144.4 (m, C-3 and 5), 124.1 (t, J = 15 Hz, C-4), 111.9 (t, J = 16.5, C-
1), 67.0 (s, –CHOH), 52.3 (s, OCH3). 19F NMR (470.4 MHz, CDCl3)
ꢀ142.86 (dd, J = 20 and 12 Hz (2,20 and 6,60)), ꢀ143.8 (bs, 3,30 and
5,50). ESI-MS 475 [(M+H)+ (100)]. HR-MS 497.0247 [calculated for
210 mg (73%). IR (Neat) 2962, 2251, 1566, 1498, 1362, 1302 cmꢀ1
1H NMR (500 MHz, CDCl3)
5.91 (1H, t, J = 7 Hz, –CH–NO2), 3.09
.
d
(1H, m, >CH–CHH*–), 2.68 (1H, m, >CH–CHH*), 2.62 (1H, m, –
CHH*–CN), 2.50 (1H, m, –CHH*–CN). EI-MS (70 eV) 241 [(MꢀNO2)+
(21)], 188 [(100)]. CI-MS 288 [(M+H)+ (100)], 241 [(MꢀNO2)+ (53)].
HR-MS 288.0407 [calculated for C11H6N3O2F4 = 288.0396].
C
18H10O6F8Na = 497.0247].
4.8. Nef reaction of II and IV with TiCl3 (XI and XIII)
Acknowledgments
To a solution of 12% TiCl3 (12 ml) and ammonium acetate (3.0 g)
was added II or IV (1 mmol) in THF (5 ml) under nitrogen
atmosphere and the solution was stirred for 5 h at room tempera-
ture. A violet colored slurry appeared. This was extracted with ether
(5ꢂ 10 ml) and washed with sodium bicarbonate solution till
neutral. The solution was dried, solvent evaporated and the residue
distilled through a bulb to bulb distillation assembly.
The Authors thank Department of Science and Technology, New
Delhi, IIT Madras Sophisticated Analytical Instrument Facility and
DRDE Gwalior for recording NMR spectra.
References
XI A colorless liquid, b.p. 105–110 8C/1 mmHg. Yield: 177 mg
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