Studies on the rearrangement of ortho-nitro-benzylidenemalonates and their analogues to 2-aminobenzoate derivatives

Article abstract of DOI:10.1139/v02-010

Reaction of the diethyl 2-nitro-4-(trifluoromethyl)benzylidenemalonate with diethylamine in alcohols resulted in the reduction of the nitro group and the oxidation of the vinylic carbon attached to the phenyl ring. Simultaneous migration of the malonic fr

Full text of DOI:10.1139/v02-010

192
Studies on the rearrangement of ortho-nitro-
benzylidenemalonates and their analogues to
2-aminobenzoate derivatives
Elzbieta Lewandowska, Stefan Kinastowski, and Stanislaw F. Wnuk
Abstract: Reaction of the diethyl 2-nitro-4-(trifluoromethyl)benzylidenemalonate with diethylamine in alcohols resulted
in the reduction of the nitro group and the oxidation of the vinylic carbon attached to the phenyl ring. Simultaneous
migration of the malonic fragment gave the appropriate 2-amino-4-(trifluoromethyl)benzoate esters. The presence of at
least two nitro groups, or one nitro group and trifluoromethyl group on the phenyl ring, attached to the α-carbon and
strongly electron withdrawing substituents at the β-carbon (CO2Et, CN) in ortho-nitrobenzylidene systems is necessary
for this reductive–oxidative rearrangement to proceed. Reaction of nitrocinnamates with thiols in the presence of
triethylamine in tetrahydrofuran gave Michael addition products with different regioselectivity of addition. Ethyl 2-
nitrocinnamate undergoes standard β-addition of thiols to a carbon–carbon double bond. However, 2,4-dinitro- and
2,4,6-trinitrocinnamates undergo α-addition of thiols, indicating that the presence of two nitro groups on the phenyl
ring can reverse polarity of the carbon–carbon double bond in cinnamate acceptors.
Key words: abnormal Michael reactions, aromatic nitro compounds, benzylidene compounds, rearrangements.
Résumé : La réaction du 2-nitro-4-(trifluorométhyl)benzylidènemalonate d’éthyle avec la diéthylamine dans des alcools
conduit à la réduction du groupe nitro et à l’oxydation du carbone vinylique attaché au noyau phényle. La migration
simultanée du fragment malonique fournit les esters 2-amino-4-(trifluorométhyl)benzoates appropriés. Pour que ce réar-
rangement d’oxydoréduction se produise, il est requis d’être en présence d’un système ortho-nitrobenzylidène compor-
tant au moins deux groupes nitro ou d’un groupe nitro et d’un groupe trifluorométhyle sur le noyau phényle attaché sur
le carbone-α et des substituants fortement électroattracteurs sur le carbone-β (CO2Et, CN). La réaction des nitrocinna-
mates avec les thiols en présence de triéthylamine, dans le tétrahydrofurane, conduit à la formation des produits
d’addition de Michael avec une régiosélectivité d’addition différente. L’addition de thiols au 2-nitrocinnamate d’éthyle
conduit à l’addition β normale sur la double liaison. Toutefois, l’addition de thiols sur les 2,4-dinitro- ou 2,4,6-
trinitrocinnamates conduisent à des additions α, ce qui indique que la présence de deux groupes nitro sur le noyau phé-
nyle peut inverser la polarité de doubles liaisons carbone–carbone des accepteurs cinnamates.
Mots clés : réactions de Michael anormales, composés nitro aromatiques, composés benzylidènes, réarrangements.
[Traduit par la Rédaction] Lewandowska et al. 199
Introduction
and a new ether, thioether, or amine bond is formed at the
C-malonate carbon.
In previous work, we found that treatment of diethyl 2,4-
dinitrobenzylidenemalonate (1a) with diethylamine (DEA)
in MeOH did not lead to the expected Michael addition of
DEA to the carbon–carbon double bond. Instead it gave the
2-amino-4-nitrobenzoic acid derivative 2a (1) (Scheme 1).
Such an unusual reductive–oxidative rearrangement selec-
tively yields a variety of 2-aminobenzoic acid derivatives of
type 2 when different primary or secondary alcohols (1, 2),
thiols (3), or amines (1, 2) were used in place of MeOH. The
new ester, thioester, or amide bond is formed at position 1,
Such a skeletal rearrangement was also effective for heter-
ocyclic π-deficient analogues in which the electron-
withdrawing role of the second nitro group on the phenyl
ring was replaced by a sp2-hybridized nitrogen atom in the
ring. Thus, nitropyridylidenemalonate 1-oxides bearing nitro
and alkenyl substituents in the ortho position to each other
(e.g., 3; Scheme 2) underwent rearrangement to the amino-
substituted pyridinecarboxylate derivatives (e.g., 4) (4).
Synthetic methods involving neighboring group interac-
tion in ortho-substituted nitrobenzene derivatives have been
reviewed (5, 6), and new examples continue to attract inter-
est (7). Such redox processes, which usually involve an
intramolecular aldol condensation of the ortho substituent
with the nitro group acting as the electrophilic center, have
been used to synthesize a variety of heterocyclic compounds.
These reactions typically occur under basic conditions with
or without external reductive reagents and frequently involve
thermal transformations (5).
Received 13 August 2001. Published on the NRC Research
Press Web site at http://canjchem.nrc.ca on 22 February 2002.
E. Lewandowska and S. Kinastowski. Department of
Chemistry, University of Agriculture, ul. Wojska Polskiego
75, 60-625 Poznan, Poland.
S.F. Wnuk.1 Department of Chemistry, Florida International
University, Miami, FL 33199, U.S.A.
Photochemically induced transfer of oxygen from a nitro
group to an ortho substituent of nitrobenzene derivatives is
1Corresponding author (e-mail: wnuk@fiu.edu).
Can. J. Chem. 80: 192–199 (2002)
DOI: 10.1139/V02-010
© 2002 NRC Canada

Lewandowska et al.
193
Scheme 1.
Scheme 2.
CO2Et
OEt
O
R'
R'
CO2Et
C
DEA
MeOH
OMe
CO2Et
NO2
HN
N
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
NO2
DEA
OMe
N
R
O2N
CO2Et
EtOH
H
N
O
3
1a R = NO2, R' = H
1b R = R' = NO2
1c R = R' = H
2a R' = H
2b R' = NO2
O
4
also well known and generates uncyclized nitroso products
(5). The latter transformations have been elaborated to em-
ploy the ortho-nitrophenyl group as a photoremovable pro-
tective group for aldehydes and ketones (8) as well as
phosphate esters of adenine nucleotides (9). The recent theo-
retical analysis for the isomerization of 2-nitrotoluene to 2-
nitrosobenzyl alcohol is in good qualitative agreement with
the available experimental results for the thermal and photo-
induced rearrangement of ortho-nitrobenzyl compounds
(9c).
To the best of our knowledge, the transformation of α-
phenyl-2-nitrocinnamonitrile to N-benzoylanthranilic acid in
aqueous–ethanolic alkali (10) is the only analogous example
to our rearrangement that exists in the literature. Loudon and
Tennant (11) suggested that the possible intermediates in
this transformation involved addition of hydroxide ions to
the carbon–carbon double bond, followed by an intra-
molecular aldol-type condensation in which the nitro group
provides electrophilic center. We now report selected experi-
ments on the one-step rearrangement of ortho-nitro-
benzylidenemalonates and their analogues to various 2-
aminobenzoic acid derivatives. The scope, limitation, and
tentative mechanism of the rearrangement are also pre-
sented.
nitrotoluene is of the order of 2.3 × 104. The corresponding
thermodynamic acidities expressed as pKa values were found
to depend strongly on DMSO concentration and are 12.1,
16.6, and 25.7 for 2,4,6-trinitro-, 2,4-dinitro-, and 4-nitro-
toluene, respectively (12).
The number of nitro groups also effects the oxidative-
reductive properties of these compounds. Bock and Lechner-
Knoblauch (13) showed that 1,3,5-trinitrobenzene has the
smallest potential for the reduction of the first nitro group
(–0.51 V) whereas the reduction potentials of 1,3-dinitro-
benzene and nitrobenzene are –0.82 and –1.10 V, respec-
tively. Thus, increasing the number of the nitro groups on
the phenyl ring facilitates both formation of the carbanion at
the α-carbon (and its subsequent oxidation) and the reduc-
tion of first nitro group.
To further study effect of phenyl ring substituents on the
rearrangement, 2,6-dinitro- (6a), 2-nitro-4-(trifluoromethyl)-
(6b), and 2-chloro-6-nitrobenzylidenemalonates (6c) were
prepared in a Knoevenagel condensation (TiCl4–pyridine)
(14) between the corresponding aldehydes (5) and diethyl
malonate (Scheme 3). Reduction of commercially available
2-nitro-4-(trifluoromethyl)benzonitrile with diisobutylalum-
inum hydride (DIBALH) afforded aldehyde 5b in 56% yield.
This is a substantial improvement on a previously reported
synthesis of 5b when different synthetic approach was used
(15). Compound 6a rearranged under the influence of DEA
in ethanol to give 7a (86%) after 5 days (the rearrangement
of 1a took only a few hours to afford 2a in 84% yield (1)). It
seems that a second nitro group in the ortho position in 6a
has some steric influence on the rate of rearrangement.
Results and discussion
Effect of the substituted aromatic ring
For the series of nitrobenzylidenemalonates 1a–c reactivity
toward rearrangement increased with increasing number of ni-
tro groups on the aromatic ring. Thus, diethyl 2,4-dinitro-
benzylidenemalonate (1a) undergoes the rearrangement in
most cases (1), whereas the 2,4,6-trinitro analogue 1b rear-
ranges in all cases under the mildest conditions (2, 3). In
contrast, diethyl 2-nitrobenzylidenemalonate (1c) does not
rearrange and forms the stable β-carbonyl Michael adducts
of type 9 (R, R′ = H) with amines (1), alkoxides (1), or
thiolates (3).
The electron-withdrawing groups influence the rearrange-
ment by (i) increasing the acidicity of an α-carbon attached
to the aromatic ring, and (ii) controlling the oxidative poten-
tial of the ortho-nitro group. The relative acidities, rates of
proton abstraction, and carbanion protonation of 4-nitro-,
2,4-dinitro-, and 2,4,6-trinitrotoluenes in methanolic DMSO
have been examined (12). The kinetic ratio for proton ab-
straction from 2,4-dinitro- and 4-nitrotoluene is 230:1 in
DMSO–MeOH (98:2), whereas the ratio for 2,4,6-trinitro-
and 2,4-dinitrotoluene is about 100:1 in DMSO–MeOH
(60:40). Thus, an increase in kinetic acidity resulting from
the introduction of two ortho-nitro groups into 4-
The 2-nitro-4-trifluoromethyl analog (6b) produced under
the typical conditions (DEA–EtOH, 24 h at ambient temper-
ature) a stable adduct via ethanol addition to a double bond
(9b, 51%), plus other by-products including unchanged 6b
and rearranged 7b. However, prolonged reaction time and el-
evated temperature (~60°C) led to the expected rearranged
product 7b in 39% yield. Analogous treatment of 6b with
DEA in MeOH gave the rearranged product 8b (58%) with
concomitant transesterification of the malonic moiety. Re-
placement of the one nitro group by a chloro substituent pre-
vent the rearrangement. Thus, reaction of 2-chloro-6-
nitrobenzylidene (6c) with DEA–EtOH or amines (DEA,
piperidine, or pyrrolidine) under typical conditions resulted
in the recovery of 6c. These results indicate that two
strongly electron-withdrawing groups (EWG) must be pres-
ent in the benzene ring. The data are supported by examina-
tion of the Hammett σ values (16) (σNO > σCF > σCl),
2
3
© 2002 NRC Canada

194
Can. J. Chem. Vol. 80, 2002
Scheme 3. Reagents and conditions: (a) TiCl4/pyridine/THF;
(b) DEA/EtOH/-25°C; (c) DEA/EtOH or MeOH/-55°C.
Scheme 4.
O
R
R
R'
R'
O
CN
DEA
OR"
CN
CO2Et
a
H
R"OH
R'
NO2
OR"
CO2Et
NO2
N
H
O2N
O2N
NO2
R
R
R'
6
5
12 R = NO2, R' = CO2Et, R" = Et
13a R = H, R' = CN, R" = Et
13b R = H, R' = CN, R" = Me
10 R = NO2, R' = CO2Et
11 R = H, R' = CN
b or c
b
O
R'
R"
R'
OR"
CO2R"
c
CO2Et
β-addition to the carbonyl activated double bond (Michael
addition) (18) including cinnamates (19) (Scheme 5). Reac-
tion of 15a with propanethiol also gave α-addition product
17c whose structure was confirmed with 2D-NMR experi-
ments. Thus, the heteronuclear multiple bond coherence
(HMBC) spectrum showed that aromatic carbons (C6
(135.4) and C1 (140.5)) had a strong coupling to the dia-
stereotopic CH2 protons at 3.58 and 3.41, whereas no corre-
lation to CH proton at 3.63 was observed. Conversely, the
carbonyl carbon at 171.9 shows correlation to the CH proton
at 3.63 and only to the one diastereotopic proton at 3.41.
Ethyl 2-nitrocinnamate does not react with propanethiol
under similar conditions (TEA–THF). However, treatment of
ethyl 2-nitrocinnamate with sodium propanethiolate in EtOH
gave the standard β-addition product 18 (Scheme 6). These
results indicate that two nitro groups on the phenyl ring re-
verse polarity of the carbon–carbon double bond in
cinnamate acceptors and redirect the regioselectivity of
nucleophile addition from the classical β-addition to an ab-
normal α-addition. Such regioselectivity is controlled by the
resonance effect of the nitro groups on the phenyl ring, as
opposed to the carboxylate function. Recently, Trost and
Dake (20a) reported that phosphine-catalyzed reaction of ni-
trogen nucleophiles with 2-alkynoates also gave α-addition
product. Other examples (18a) include α-addition of
dimethylamine or methanol to methyl 3,3-di(trifluoro-
methyl)acrylate (20b).
Spectral support for the assumption that Michael addition
may occur at either the α or β carbon depending on the car-
bon–carbon double bond polarization was found by compar-
ing the absorption band of the stretching vibration of the
double bond in IR spectra of 1a–c (3) and nitrocinnamates.
Thus, 2-nitro derivative 1c displays a medium absorption
band at 1641 cm–1 (and shows β-addition), whereas the 2,4-
dinitro analogue 1a has only a very weak band at 1642 cm–1.
On the other hand, the latter compound shows an active
band at 1637 cm–1 in Raman spectrum, which points to a
symmetrical distribution of π-electron charge density in the
carbon–carbon double bond (21). The introduction of the
third nitro group resulted in the appearance of a weak ab-
sorption band at 1635 cm–1 in IR spectrum of 1b. Analo-
gously, in the cinnamate series 2,4,6-trinitro 14 [1630 cm–1
(weak)] and 2,4-dinitro 15a [1628 cm–1 (very weak)] show
α-addition, whereas ethyl 2-nitrocinnamate [1634 cm–1
(weak to medium)] and ethyl cinnamate [1634 cm–1 (me-
dium to strong)] show the β-addition.
OR"
N
H
CO2Et
NO2
R
CO2R"
R
7 R" = Et
8 R" = Me
9 R" = OEt
Series: a R = H, R' = NO2
b R = CF3, R' = H
c R = H, R' = Cl
which reflect the interaction of the substituents with the re-
action site by a combination of resonance and field effects.
Effect of the substituents on the vinylic carbons
Substituents with strong electron-acceptor properties
(CO2Et, CN) at the β-carbon in ortho-nitrobenzylidene sub-
strates also facilitate this rearrangement. Thus, reaction of
ethyl α-cyano-2,4,6-trinitrocinnamate (10) (17) with DEA–
EtOH gave the rearranged product 12 in 66% yield
(Scheme 4). 2,4-Dinitrobenzylidenemalononitrile (11) rear-
ranges in DEA–EtOH to yield ethyl 2-[N-(dicyano)(ethoxy)-
methyl]amino-4-nitrobenzoate (13a) (56%) in addition to
ethyl 2-amino-4-nitrobenzoate (21%). Treatment of 11 with
DEA–MeOH gave the methyl ester 13b.
Ethyl 2,4-dinitrocinnamate (15a), which bears only one
EWG at the β-carbon, does not undergo this rearrangement
(1). The rearrangement also failed with ethyl 2,4,6-trinitro-
cinnamate (14), despite the fact that the aromatic fragment is
identical to the most reactive analogue 1b. This indicated
that the number of nitro groups on the phenyl ring, although
a significant factor, is not the only force driving this rear-
rangement.
Interestingly, nitrocinnamates 14 and 15a,b react with
ethanethiol in THF in the presence of a catalytic amount of
triethylamine (TEA) to give products 16 and 17a,b. Mass
spectra of 16 and 17a,b, in addition to the molecular ions,
showed peaks for the ions at m/z (%) 147 (45), 147 (61), and
133 (100) for 16, 17a, and 17b, respectively. Their elemental
compositions C6H11O2S [(C2H5SCHCO2C2H5)+] for 16 and
17a and C5H9O2S [(C2H5SCHCO2CH3)+] for 17b were de-
termined by HR-MS. These compounds are formed by the α-
addition of the thiol to the α,β-unsaturated carbonyl com-
pounds, a process that is in contrast to the usually observed
The free rotation of the substituents at β-carbon and steric
factors seems also to be a factor in rearrangement. Thus,
© 2002 NRC Canada

Lewandowska et al.
195
Scheme 5.
Scheme 6.
SPr
O
R
O
R
CO2R'
CO2R'
R"SH/TEA
THF
O
OEt
O
O
SR"
NO2
O2N
NO2
O2N
NO2
NO2
O2N
14 R = NO2, R' = Et
15a R = H, R' = Et
15b R' = H, R' = Me
16 R = NO2, R' = Et, R" = Et
17a R = H, R' = Et, R" = Et
17b R = H, R' = Me, R" = Et
17c R = H, R' = Et, R" = Pr
19
18
Scheme 7.
B
OMe
OMe
H
CO2Et
CO2Et
OMe
MeOH
HNEt2
H
1a
B
CO2Et
CO2Et
CO2Et
N
O
O2N
NO2
O2N
CO2Et
N
O
O2N
O
HO
22
BH
20
21
-
H2O
MeO
O
N
B
OY
MeO
O
Y
MeOH
CO2Et
OMe
2a
CO2Et
CO2Et
-
H2O
CO2Et
CO2Et
N
O2N
N
O
O2N
O2N
OMe
BH
25
CO2Et
OH
HB
23
24
OY = OH or OMe
B = MeO or Et2NH
2,4-dinitrobenzylidene derivative of Meldrum’s acid 19 did
not yield the rearranged product under standard condition
(DEA–EtOH).
C-malonate carbon in addition to the regular polarization of
carbon–nitrogen double bond. A similar mechanism for the
conversion of α-phenyl-2-nitrocinnamonitrile to N-benzoy-
lanthranilic acid has been suggested (11) (vide supra). In our
previous mechanism direct transfer of oxygen from a nitro
group to an ortho-benzylic position was proposed (1). How-
ever, such direct transfers are normally induced photochemi-
cally rather than thermally (e.g. in the 2-nitrobenzaldehyde
into 2-nitrosobenzoic acid and related rearrangements) (5b).
In conclusion, an unusual rearrangement of ortho-
nitrobenzylidenemalonates (e.g., 1a,b or 6) and their ana-
logues (e.g., 10 or 11) in the presence of diethylamine in al-
Tentative mechanism
The intramolecular nature of this rearrangement was pre-
viously proven in experiments using isotopically labelled
dimethyl-d6 malonate and dimethyl-d6 2,4-dinitrobenzy-
lidenemalonate (1). The possible mechanism might involve
the following sequence of steps: (i) a classical Michael addi-
tion of the alcohol molecule to a π-electron deficient car-
bon–carbon double bond in 1a to give 20; (ii) an aldol
condensation between carbanion 21 and nitro group to yield
the cyclic intermediate 22; (iii) redox processes involving
the quinonoid intermediate 23 followed by addition of a sec-
ond alcohol (or water) molecule that results in regeneration
of aromaticity; (iv) nucleophilic ring opening of 24 and si-
multaneous migration of the malonic fragment, which leads
directly to the formation of the highly conjugated ester at
position 1 and Schiff base at position 2; and (v) addition of
alcohol to the resulting electron-deficient ketimin of
mesoxalic ester 25 at position 2 gives the rearranged product
2a (Scheme 7). Ketimin 25 would be expected to undergo
addition quite readily owing the presence of two EWG at the
cohols produces
a variety of 2-aminobenzoate ester
derivatives (e.g., 2, 7, 8, 12, or 13). The presence of at least
two nitro groups, or one nitro group and trifluoromethyl
group, on the phenyl ring together with strongly electron-
withdrawing substituents at the β-carbon (CO2Et, CN) in
ortho-nitrobenzylidene systems, appears to be necessary for
this reductive–oxidative rearrangement to proceed. Reaction
of nitrocinnamates with thiols in the presence of TEA in
THF gave Michael addition products with different regio-
selectivity of addition. Ethyl 2-nitrocinnamate undergoes the
standard β-addition of thiols to the carbon–carbon double
bond. However 2,4-dinitro- (15) and 2,4,6-trinitrocinnamates
© 2002 NRC Canada

196
Can. J. Chem. Vol. 80, 2002
(14) undergo abnormal Michael-type α-addition of thiols in-
dicating that the presence of two nitro groups on the phenyl
ring can reverse polarity of the carbon–carbon double bond
in cinnamate acceptors.
Diethyl 2-nitro-4-(trifluoromethyl)benzylidenemalonate
(6b)
Treatment of 2-nitro-4-(trifluoromethyl)benzaldehyde (5b;
0.9 g, 4.1 mmol) with diethyl malonate by procedure A gave
6b (1.2 g, 81%); mp 72°C (EtOH). IR (CHCl3) (cm–1): 1733
1
(C=O), 1628 (C=C). H NMR δ: 1.08 (t, J = 7.1 Hz, 3H,
CH3), 1.38 (t, J = 7.1 Hz, 3H, CH3), 4.12 (q, J = 7.1 Hz, 2H,
CH2), 4.37 (q, J = 7.1 Hz, 2H, CH2), 7.61 (d, J = 8.0 Hz,
1H, HAr), 7.92 (d, J = 7.1 Hz, 1H, HAr), 8.19 (s, 1H, HAr),
8.50 (s, 1H, CH). 13C NMR δ: 14.1, 14.5, 62.2, 62.7, 122.7
Experimental
Uncorrected melting points were determined with a capil-
lary apparatus. UV spectra were measured with solutions in
3
1
3
(q, J = 3.7 Hz), 122.9 (q, J = 273.1 Hz), 130.6 (q, J =
2
MeOH. 1H (200 or 400 MHz), 13C (50 or 100 MHz), and 19
F
3.3 Hz), 130.8, 131.6, 133.0 (q, J = 34.6 Hz), 134.5, 163.4,
164.6. 19F NMR δ: –63.49 (s). APCI-MS m/z: 362 (100,
[M + H]+). Anal. calcd. for C15H14F3NO6: C 49.87, H 3.91,
N 3.88; found: C 49.84, H 3.95, N 3.78.
(376.5 MHz (CFCl3)) NMR spectra were determined with
solutions in CDCl3 unless otherwise specified. Mass spectra
(MS and HR-MS) were obtained with electron impact (EI,
20 eV) or atmospheric pressure chemical ionization (APCI)
techniques. Merck kieselgel 60-F254 sheets were used for
TLC and products were detected with 254 nm light. Merck
kieselgel 60 (230–400 mesh) was used for column chroma-
tography. Elemental analyses were determined at micro-
analytical laboratories at Adam Mickiewicz University,
Poznan, Poland or Galbraith Laboratories, Knoxville, TN.
Reagent grade chemicals were used, and solvents were dried
by reflux over and distillation from CaH2 (except THF–po-
tassium) under argon.
Diethyl 2-chloro-6-nitrobenzylidenemalonate (6c)
The 2-chloro-6-nitrobenzaldehyde (0.93 g, 5 mmol) was
treated with diethyl malonate by procedure A to give 6c
(1.3 g, 79%); mp 53°C (EtOH). IR (CHCl3) (cm–1): 1720
(C=O). 1H NMR δ: 1.01 and 1.37 (2t, J = 7.2 Hz, 6H,
2CH3), 4.02 and 4.35 (2q, J = 7.2 Hz, 4H, 2CH2), 7.43–8.15
(m, 4H, HAr, CH). EI-MS m/z: 329 (1, M+(37Cl)), 327 (3,
M+(35Cl)), 292 (100, [M
–
Cl]+). Anal. calcd. for
C14H14ClNO6: C 51.31, H 4.31, N 4.27; found: C 51.30,
H 4.28, N 4.27.
2-Nitro-4-(trifluoromethyl)benzaldehyde (5b)
Ethyl 2-(N-(ethoxy)(diethoxycarbonyl)methyl)amino-6-
DIBALH (0.9 mL, 0.71 g, 5 mmol) was added dropwise
via syringe to a stirred solution of 2-nitro-4-(trifluoro-
methyl)benzonitrile (1.08 g, 5 mmol) in dried benzene
(20 mL) under N2 at ambient temperature. After 2 h, reac-
tion mixture was cooled down (ice bath) and 1 M H2SO4
(~5 mL) was slowly added. The organic layer was washed
(NaHCO3–H2O, brine), dried (MgSO4) and volatiles were
evaporated. Column chromatography (5 → 15% EtOAc–hex-
ane) gave 5b (0.61 g, 56%); mp 42°C (lit. (15) mp 35°C)
with data as reported (15).
nitrobenzoate (7a)
Procedure B
DEA (0.2mL, 2.0 mmol) was added to a solution of di-
ethyl 2,6-dinitrobenzylidenemalonate (6a; 338 mg, 1 mmol)
in EtOH (8 mL) and stirring was continued at ambient tem-
perature for 5 days. The resulting mixture was evaporated
and the residue was partitioned (EtOAc, diluted with HCl–
H2O). The organic layer was washed (NaHCO3–H2O, brine),
dried (MgSO4), and evaporated to dryness. Column chroma-
tography (CH3Cl–CCl4–EtOAc, 10:5:1) gave 7a (354 mg,
86%); mp 85°C (EtOH). IR (CHCl3) (cm–1): 3300 (NH),
1
Diethyl 2,6-dinitrobenzylidenemalonate (6a)
1720 (C=O). H NMR δ: 1.18–1.27 (m, 9H, 3CH3), 1.34
(t, J = 7.1 Hz, 3H, CH3), 3.48 (q, J = 7.1 Hz, 2H, CH2),
4.22–4.44 (m, 6H, 3CH2), 7.14 (dd, J = 7.0, 1.8 Hz, 1H,
HAr), 7.30–7.42 (m, 2H, HAr), 8.27 (br s, 1H, NH). EI-MS
m/z: 412 (3, M+), 265 (100). Anal. calcd. for C18H24N2O9:
C 52.42, H 5.87, N 6.86; found: C 52.38, H 5.82, N 6.86.
Procedure A
Titanium(IV) chloride (1.1 mL, 10 mmol) in carbon tetra-
chloride (2.5 mL) was added dropwise to THF (40 mL) and
the mixture was cooled to ~5°C. After 15 min 2,6-dinitro-
benzaldehyde (0.98 g, 5 mmol) in THF (5 mL) and diethyl
malonate (0.76 mL, 0.80 g, 5 mmol) were added dropwise
with stirring. Pyridine (1.6 mL, 20 mmol) in THF (5 mL)
was then added dropwise over 20 min. After 24 h, water
(8 mL) and diethyl ether (8 mL) were added, the organic
layer was separated, and the aqueous layer extracted with
ether. The combined ether solution was washed with brine,
NaHCO3–H2O and brine, dried (MgSO4), and concentrated.
The precipitate formed on cooling was filtered and
recrystallized (EtOH) to give 6a (1.2 g, 71%); mp 56–57°C.
Ethyl 2-(N-(ethoxy)(diethoxycarbonyl)methyl)amino-4-
(trifluoromethyl)benzoate (7b)
Treatment of 6b (180 mg, 0.5 mmol) by procedure B
(~60°C, 24 h) and column chromatography (4 → 15%
EtOAc–hexane) gave crude 7b (~115 mg; purity ~75% (1H
NMR) contaminated by 6b and 9b). This material was col-
umn chromatographed again to give 7b (85mg, 39%) as a
solidified oil. IR (CHCl3) (cm–1): 3300 (NH), 1752, 1739,
1
1697 (C=O). H NMR δ: 1.23 (t, J = 7.2 Hz, 3H, CH3), 1.25
IR (CHCl3) (cm–1): 1720 (C=O). H NMR δ: 1.02 and 1.37
(t, J = 7.1 Hz, 6H, 2CH3), 1.44 (t, J = 7.1 Hz, 3H, CH3),
3.50 (q, J = 7.1 Hz, 2H, CH2), 4.27–4.35 (m, 4H, 2CH2),
4.43 (q, J = 7.1 Hz, 2H, CH2), 7.01 (d, J = 8.3 Hz, 1H, HAr),
7.49 (s, 1H, HAr), 8.09 (d, J = 8.3 Hz, 1H, HAr), 9.68 (s, 1H,
NH). 13C NMR δ: 14.3 (2C), 14.7, 15.3, 59.7, 61.8, 63.5
1
(2t, J = 7.4 Hz, 6H, 2CH3), 3.98 and 4.34 (2q, J = 7.4 Hz,
4H, 2CH2), 7.75 (t, J = 8.3 Hz, 1H, HAr), 8.10–8.37 (m, 3H,
HAr, CH). EI-MS m/z: 338 (5, M+). Anal. calcd. for
C14H14N2O8: C 49.71, H 4.17, N 8.28; found: C 49.74,
H 3.83, N 8.29.
1
(2C), 87.9, 111.9, 114.3, 115.8, 123.9 (q, J = 273.0 Hz),
© 2002 NRC Canada

Lewandowska et al.
197
2
132.8, 135.9 (q, J = 32.3 Hz), 146.8, 167.6 (2C), 167.6. 19F
was allowed to stand for 6 h and then evaporated to dryness
under vacum. The residue was chromatographed (CCl4–
CHCl3–Me2CO, 10:5:1) and crystallized (EtOH) to give 12
(0.135 g, 66%) as a yellow crystals; mp 120–121°C. UV–vis
(MeOH) λ (nm) (ε (M–1 cm–1)): 367 (3500). IR (KBr) (cm–1):
3100 (NH), 2240 (CN), 1730, 1690 (C=O). 1H NMR δ:
1.20–1.65 (m, 9H, 3CH3), 4.00–4.60 (m, 6H, 3CH2), 8.45
(d, J = 2.1 Hz, 1H, HAr), 9.61 (d, J = 2.1 Hz, 1H, HAr),
10.20 (s, 1H, NH). 13C NMR δ: 13.4, 13.9, 62.9, 64.5, 83.2,
113.4, 114.5, 119.5, 124.5, 138.5, 154.7, 159.6, 163.2. EI-
MS m/z: 410 (1, M+), 383 (5), 236 (100). Anal. calcd. for
C16H18N4O9: C 46.83, H 4.42, N 13.65; found: C 46.76,
H 4.40, N 13.71.
NMR δ: –64.25 (s). APCI-MS m/z: 390 (100, [M + H –
EtOH]+). Anal. calcd. for C19H24F3NO7: C 52.41, H 5.56,
N 3.22; found: C 52.62, H 5.41, N 3.33.
Methyl 2-(N-(methoxy)(dimethoxycarbonyl)methyl)-
amino-4-(trifluoromethyl)benzoate (8b)
Treatment of 6b (180 mg, 0.5 mmol) by procedure B
(~50°C, 24 h; MeOH was used instead of EtOH) and column
chromatography (4 → 20% EtOAc–hexane) gave 8b (110 mg,
58%); mp 128–130°C (MeOH). IR (CHCl3) (cm–1): 3300
1
(NH), 1740, 1698 (C=O). H NMR δ: 3.29 (s, 3H, CH3),
3.86 (s, 6H, 2CH3), 3.98 (s, 3H, CH3), 7.04 (d, J = 8.1 Hz,
1H, HAr), 7.34 (s, 1H, HAr), 8.10 (d, J = 8.2 Hz, 1H, HAr),
9.68 (s, 1H, NH). 13C NMR δ: 51.5, 52.9, 54.3 (2C), 88.5,
111.4, 114.8, 115.7, 123.8 (q, 1J = 273.2 Hz), 132.8,
136.3 (q, 2J = 32.5 Hz), 146.6, 167.2 (2C), 168.1. 19F
NMR δ: –64.17 (s). APCI-MS m/z: 348 (100, [M + H –
MeOH]+). Anal. calcd. for C15H16F3NO7: C 47.50, H 4.25,
N 3.69; found: C 47.63, H 4.32, N 3.62.
Ethyl 2-(N-(dicyano)(ethoxy)methyl))amino-4-nitro-
benzoate (13a)
Treatment (18 h) of 2,4-dinitrobenzylidenemalononitrile
(17) (11; 0.122 g, 0.5 mmol) by procedure C (column chro-
matography: CCl4–CHCl3–Me2CO, 60:10:1) gave ethyl 2-
amino-4-nitrobenzoate (22 mg, 21%; mp 90–91°C (lit. (22)
mp 89–91°C)) and 13a (89 mg, 56%) as a second eluting
compound; mp 63°C (EtOH). UV–vis (MeOH) λ (nm)
(ε (M–1 cm–1)): 327 nm (2750). IR (CHCl3) (cm–1): 3270
Diethyl 2-ethoxy-2-(2-nitro-4-(trifluoromethyl)phenyl)-
ethane-1,1-dicarboxylate (9b)
DEA (0.06 mL, 0.6 mmol) was added to a solution 6b
(108 mg, 0.3 mmol) in EtOH (3 mL) and stirring was con-
tinued for 24 h at ambient temperature and then at ~35°C for
6 h. Evaporation, work-up (as described in procedure B),
and column chromatography (5 → 15% EtOAc–hexane)
gave 9b (62 mg, 51%) as a first eluting product followed by
recovered 6b and 7b. Compound 9b: IR (CHCl3) (cm–1):
1
(NH), 2270 (CN), 1720 (C=O). H NMR δ: 1.31–1.56 (m,
6H, 2CH3), 4.25–4.54 (m, 4H, 2CH2), 7.75–8.15 (m, 3H,
HAr), 9.33 (s, 1H, NH). EI-MS m/z: 291 (16, [M – HCN]+),
263 (21), 218 (100). Anal. calcd. for C14H14N4O5: C 52.83,
H 4.40, N 17.65; found: C 52.78, H 4.43, N 17.60.
1
Methyl 2-(N-(dicyano)(methoxy)methyl)amino-4-nitro-
benzoate (13b)
1751, 1733 (C=O). H NMR δ: 1.15, 1.16, 1.30 (3t, J =
7.1 Hz, 9H, 3CH3), 3.38–3.59 (m, 2H, CH2), 3.81 (d, J =
8.3 Hz, 1H, CH), 4.08 (q, J = 7.2 Hz, 2H, CH2), 4.23–4.31
(m, 2H, CH2), 5.68 (d, J = 8.3 Hz, 1H, CH), 7.90 (d, J =
8.2 Hz, 1H, HAr), 7.97 (d, J = 8.2 Hz, 1H, HAr), 8.17 (s, 1H,
HAr). 13C NMR δ: 14.2, 14.5, 15.4, 59.7, 62.1, 62.3, 66.4,
Treatment of 11 (17) (0.122 mg, 0.5 mmol) by procedure
C (18 h, MeOH was used instead of EtOH) and purification
(as described for 13a) gave methyl 2-amino-4-nitrobenzoate
(22 mg, 23%; mp 158°C (lit. (23) 154–156°C)) and 13b
(86 mg, 59%; mp 82°C (MeOH)). IR (CHCl3) (cm–1): 3270
3
1
74.3, 122.0 (q, J = 3.6 Hz), 123.0 (q, J = 272.8 Hz), 129.9
3
2
1
(q, J = 3.2 Hz), 131.1, 131.9 (q, J = 34.3 Hz), 139.7,
149.8, 166.7, 166.8. 19F NMR δ: –63.41 (s). APCI-MS m/z:
408 (100, [M + H]+). Anal. calcd. for C17H20F3NO7:
C 50.13, H 4.95, N 3.44; found: C 50.19, H 5.18, N 3.46.
Analogous treatment (8 h, ambient temperature) of 6b
(108 mg, 0.3 mmol) with piperidine (0.06 mL, 0.6 mmol) in
EtOH (3 mL) also gave 9b (83 mg, 68%).
Similar treatment (18 h, ambient temperature) of 6b
(0.25 mmol) with DEA (0.5 mmol) or TEA (0.5 mmol) in
MeOH (3 mL) gave analogous adduct of MeOH addition to
(NH), 2270 (CN), 1720 (C=O). H NMR δ: 3.92 (s, 3H,
CH3), 4.08 (s, 3H, CH3), 7.76–8.25 (m, 3H, HAr), 9.35 (s,
1H, NH). EI-MS m/z: 263 (12, [M – HCN]+), 232 (100).
Anal. calcd. for C12H10N4O5: C 49.66, H 3.47, N 19.31;
found: C 49.58, H 3.42, N 19.35.
Ethyl (E)-2,4,6-trinitrocinnamate (14)
Procedure D
1
To a stirred solution of 2,4,6-trinitrobenzaldehyde (24)
(0.24g, 1 mmol) in anhydrous acetonitrile (15 mL) (carbeth-
oxymethylene)triphenylphosphorane (0.37g, 1.1 mmol) was
added in one portion. The resulting cherry reaction mixture
was stirred overnight at ambient temperature and then evap-
orated. The oily residue was chromatographed on silica gel
(MeOH–CHCl3, 1:99) and crystallized from MeOH to give
14 (0.202 g, 65%, two crops); mp 52–53°C. UV–vis (MeOH)
λ (nm) (ε (M–1 cm–1)): 234 (21 800). IR (KBr) (cm–1): 1710
a carbon–carbon double bond (e.g. 9b, R′′ = OMe, 52%; H
NMR δ: 3.33 (s, 3H, OCH3), 3.82 (d, J = 7.8 Hz, 1H, CH),
5.59 (d, J = 7.8 Hz, 1H, CH)) in addition to unchanged 6b
and transmethylation by-products.
Treatment (24h, 50°C) of 9b (41 mg, 0.1 mmol) with
DEA (0.02 mL, 0.2 mmol) in EtOH (2 mL) produced 7b
(17 mg, 40%).
Ethyl 2-(N-(cyano)(ethoxy)(ethoxycarbonyl)methyl)-
amino-4,6-dinitrobenzoate (12)
1
(C=O), 1630w (C=C). H NMR δ: 1.35 (t, J = 7.0 Hz, 3H,
CH3), 4.29 (q, J = 7.0 Hz, 2H, CH2), 6.01 (d, J = 16.5 Hz,
1H, CH), 7.99 (d, J = 16.5 Hz, 1H, CH), 9.00 (s, 2H, HAr).
EI-MS m/z: 266 (100, [M – OEt]+). Anal. calcd. for
C11H9N3O8: C 42.45, H 2.91, N 13.50; found: C 42.51,
H 2.88, N 13.42.
Procedure C
Ethyl α-cyano-2,4,6-trinitrocinnamate (17) (10; 0.168 g,
0.5 mmol) was dissolved in EtOH (4 mL) and DEA (0.1 mL,
1 mmol) was added at ambient temperature. The mixture
© 2002 NRC Canada

198
Can. J. Chem. Vol. 80, 2002
Reaction of 14 with DEA in ethanol by procedure C did
not afford rearranged product and only unchanged 14 was
recovered (~81%).
Ethyl 2-propylthio-3-(2,4-dinitrophenyl)propionate (17c)
Treatment of 15a (133 mg, 0.5 mmol) with propanethiol
(2.0 mmol) by procedure E (column chromatography:
CHCl3) gave 17c (150 g, 88%) as a slightly yellow oil. IR
1
(neat) (cm–1): 1734 (C=O). H NMR δ: 0.97 (t, J = 7.3 Hz,
Ethyl (E)-2,4-dinitrocinnamate (15a)
3H, CH3), 1.26 (t, J = 7.1 Hz, 3H, CH3), 1.59 (septet, J =
7.3 Hz, 2H, CH2), 2.58–2.70 (m, 2H, SCH2), 3.41 (dd, J =
13.3, 6.8 Hz, 1HA, from 3-CH2), 3.58 (dd, J = 13.3, 8.1 Hz,
1HA′, from 3-CH2), 3.63 (t, J = 7.3 Hz, 1H, CH), 4.11–4.25
(m, 2H, CH2), 7.70 (d, J = 8.5 Hz, 1H, HAr), 8.40 (dd, J =
8.4, 2.3 Hz, 1H, HAr), 8.85 (d, J = 2.3 Hz, 1H, HAr). 13C
NMR δ: 13.7 (CH3), 14.5 (CH3), 22.9 (CH2), 34.4 (SCH2),
35.5 (3CH2), 46.6 (CH), 62.1 (CH2), 121.0 (C6), 127.3 (C5),
135.4 (C6), 140.5 (C1), 147.4 and 149.6 (C2/4), 171.9
(C=O) (assignments based on DEPT and HETCOR experi-
ments). APCI-MS m/z: 343 (100, [M + H]+). Anal. calcd. for
C14H18N2O6S: C 49.11, H 5.30, N 8.18; found: C 49.25,
H 5.39, N 8.18.
Treatment of 2,4-dinitrobenzaldehyde (0.196 g, 1 mmol)
with Ph3P=CHCO2Et by procedure D gave 15a (181 mg,
68%); mp 91–92°C (lit. (25) mp 94°C). IR (CHCl3) (cm–1):
1
1705 (C=O), 1628w (C=C). H NMR δ: 1.27 (t, J = 7.0 Hz,
3H, CH3), 4.31 (q, J = 7.0 Hz, 1H, CH2), 6.46 (d, J =
16.8 Hz, 1H, CH), 7.84 (d, J = 8.5 Hz, 1H, HAr), 8.11 (d, J =
16.8 Hz, 1H, CH), 8.48 (dd, J = 8.5, 2.3 Hz, 1H, HAr), 8.89
(d, J = 2.3 Hz, 1H, HAr).
As a less polar product Z-isomer of 15a (40 mg, 15%)
was eluted from the column (1H NMR δ: 6.24 (dd, J = 11.9,
1.8 Hz, 1H, CH), 7.43 (d, J = 11.9 Hz, 1H, CH)).
Ethyl 2-ethylthio-3-(2,4,6-trinitrophenyl)propionate (16)
Procedure E
Ethyl 3-propylthio-3-(2-nitrophenyl)propionate (18)
Propanethiol (0.21 mL, 179 mg, 2.35 mmol) was added to
a stirred solution of EtONa in EtOH (prepared from Na
(50 mg, 2.1 mmol) and EtOH (2.0 mL)) at ambient tempera-
ture. After 15 min, ethyl (E)-2-nitrocinnamate (27) (130 mg,
0.59 mmol; prepared from 2-nitrobenzaldehyde by proce-
dure D (93%)) dissolved in ethanol (4.0 mL) was added
dropwise and the stirring was continued for 2 h. The result-
ing mixture was evaporated and the residue was partitioned
(CHCl3–H2O). The organic layer was dried (MgSO4), evapo-
rated, and column chromatographed (CHCl3) to give 18
Ethanethiol (0.15 mL, 0.124 g, 2 mmol) and then
triethylamine (0.03 mL, 0.022 g, 0.22 mmol) were added to
a stirred solution of 14 (0.155 g, 0.5 mmol) in anhydrous
THF (5 mL) at ambient temperature. TLC (CCl4–CHCl3–
Me2CO, 15:5:1) taken after 18 h indicated complete con-
sumption of 14 (Rf = 0.52) with formation of less polar
product (Rf = 0.58). After evaporation, the yellowish oily
residue was chromatographed (CHCl3) to give 16 (0.159 g,
85%) as a slightly yellow spectroscopically pure oil. IR
(CHCl3) (cm–1): 1720 (C=O). 1H NMR δ: 1.17 (t, J =
7.5 Hz, 3H, CH3), 1.26 (t, J = 7.0 Hz, 3H, CH3), 2.56 (q, J =
7.5 Hz, 2H, SCH2), 3.41–3.85 (m, 3H, CH2-CH), 4.19 (q,
J = 7.0 Hz, 2H, CH2), 8.80 (s, 2H, HAr). EI-HRMS m/z:
373.0586 (20, M+ (C13H15N3O8S) = 373.0579), 147.0474
(45, (C6H11O2S) = 147.0479, CH(SEt)CO2Et).
1
(97 mg, 56%) as an oil. IR (neat) (cm–1): 1740 (C=O). H
NMR δ: 0.92 (t, J = 7.3 Hz, 3H, CH3), 1.17 (t, J = 7.1 Hz,
3H, CH3), 1.50–1.57 (m, 2H, CH2), 2.39 (dt, J = 12.6,
7.3 Hz, 1HA, SCH2), 2.50 (ddd, J = 12.6, 7.8, 6.6 Hz, 1HA′,
SCH2), 2.88 (dd, J = 15.4, 8.2 Hz, 1HA, CH2), 2.94 (dd, J =
15.4, 7.2 Hz, 1HA′, CH2), 4.07 (q, J = 7.1 Hz, 2H, CH2),
4.99 (t, J = 7.8 Hz, 1H, CH), 7.38 (t, J = 7.7 Hz, 1H, HAr),
7.60 (t, J = 7.6 Hz, 1H, HAr), 7.78 (dd, J = 8.0, 1.0 Hz, 2H,
HAr). 13C NMR δ: 13.7 (CH3), 13.8 (CH3), 23.0 (CH2), 34.3
(SCH2), 39.4 (CH), 42.3 (2CH2), 61.4 (CH2), 124.5 (C3),
128.4 (C4), 130.1 (C6), 133.4 (C5), 137.4 (C1), 150.1 (C2),
170.3 (C=O) (assignments based on DEPT and HETCOR
experiments). APCI-MS m/z: 298 (100, [M + H]+). Anal.
calcd. for C14H19NO4S: C 56.55, H 6.44, N 4.71; found:
C 56.46, H, 6.66, N 4.79.
Compound 16 (as well as 17a,b) was stable when kept at
~5°C for a week. However, significant decomposition
1
(~20%, H NMR) was observed after 3 months.
Ethyl 2-ethylthio-3-(2,4-dinitrophenyl)propionate (17a)
Treatment of 15a (0.133 g, 0.5 mmol) by procedure E
gave 17a (0.15 g, 91%) as a slightly yellow oil. IR (CHCl3)
(cm–1): 1720 (C=O). H NMR δ: 1.22 (t, J = 7.4 Hz, 3H,
1
CH3), 1.29 (t, J = 7.0 Hz, 3H, CH3), 2.68 (q, J = 7.4 Hz, 2H,
SCH2), 3.39–3.77 (m, 3H, CH2-CH), 4.26 (q, J = 7.0 Hz,
2H, CH2), 7.69 (d, J = 8.6 Hz, 1H, HAr), 8.37 (dd, J = 8.6,
2.3 Hz, 1H, HAr), 8.83 (d, J = 2.3 Hz, 1H, HAr). EI-HRMS
Treatment of ethyl 2-nitrocinnamate (27) (0.5 mmol) with
propanethiol (2.0 mmol) by procedure E gave unchanged
ethyl 2-nitrocinnamte (91%).
m/z: 328.0731 (18, M+ (C13H16N2O6S)
= 328.0728),
147.0476 (61, (C6H11O2S) = 147.0479, CH(SEt)CO2Et).
2,2-Dimethyl-5-(2,4-dinitrobenzylidene)-1,3-dioxan-4,6-
dione (19)
Methyl 2-ethylthio-3-(2,4-dinitrophenyl)propionate (17b)
Treatment of methyl 2,4-dinitrocinnamate (26) (15b;
0.129 g, 0.5 mmol) by procedure E gave 17b (0.15 g, 93%)
2,4-Dinitrobenzaldehyde (0.98 g, 5 mmol) was treated
with 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid)
(0.72 g, 5 mmol) by procedure A to give 19 (0.69 g, 43%);
1
as a slightly yellow oil. IR (CHCl3) (cm–1): 1705 (C=O). H
1
NMR δ: 1.23 (t, J = 7.4 Hz, 3H, CH3), 2.75 (q, J = 7.4 Hz,
2H, SCH2), 3.41–3.78 (m, 3H, CH2-CH), 3.72 (s, 3H, CH3),
7.68 (d, J = 8.4 Hz, 1H, HAr), 8.39 (dd, J = 8.4, 2.3 Hz, 1H,
HAr), 8.82 (d, J = 2.3 Hz, 1H, HAr). EI-HRMS m/z:
314.0566 (14, M+ (C12H14N2O6S) = 314.0572), 133.0328
(100, (C5H9O2S) = 133.0323, CH(SEt)CO2Me).
mp 138–139°C (EtOH). IR (CHCl3) (cm–1): 1720 (C=O). H
NMR δ: 1.82 (s, 6H, 2CH3), 7.68 (dd, J = 8.4, 0.6 Hz, 1H,
HAr), 8.58 (dd, J = 8.4, 2.1 Hz, 1H, HAr), 8.76 (d, J =
0.6 Hz, 1H, CH), 9.12 (d, J = 2.1 Hz, 1H, HAr). EI-MS m/z:
322 (3, M+). Anal. calcd. for C13H10N2O8: C 48.46, H 3.13,
N 8.69; found: C 48.38, H 2.86, N 8.56.
© 2002 NRC Canada

Lewandowska et al.
199
10. R. Pschorr and O. Wolfes. Ber. Dtsch. Chem. Ges. 32, 3399
(1899).
11. J.D. Loudon and G. Tennant. J. Chem. Soc. 3466 (1960).
12. J.P. Lelievre, P.G. Farrell, and F. Terrier. J. Chem. Soc. Perkin
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13. H. Bock and U.Z. Lechner-Knoblauch. Naturforsch. Teil B,
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14. W. Lehnert. Tetrahedron, 29, 635 (1973).
15. M.C. Wani, A.W. Nicholas, G. Manikumar, and M.E. Wall. J.
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16. L.P. Hammett. Physical organic chemistry. Reaction rates,
equilibria, and mechanism. 2nd ed. McGraw–Hill, New York.
1970. pp. 347–390.
Reaction of 19 with DEA in ethanol by procedure C did
not afford rearranged product and only unchanged 19 was
recovered (~92%).
Acknowledgments
We thank Alberto J. Sabucedo at Advanced Mass Spec-
troscopy Facility at FIU for his contribution and the Florida
International University Foundation for support. We also
thank Professor P. N. Preston (Heriot-Watt University) for
suggestions concerning mechamism.
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