Electrooxidative coupling of salts of nitro compounds with halide, nitrite, cyanide, and phenylsulfinate anions

Article abstract of DOI:10.1007/s11172-006-0007-7

Electrolysis of salts of primary and secondary nitro compounds (nitroethane, 1- and 2-nitropropanes, nitrocyclohexane, and nitrocycloheptane) in the presence of excess halide, nitrite, cyanide, and phenylsulfinate anions under undivided and divided amperostatic electrolysis conditions in a two-phase medium (CH₂Cl₂/H₂O) produces geminal nitrohalides (35-85% yields), dinitro compounds (15-51%), nitronitriles (6-27%), and nitrosulfones (50-70%). The salts of secondary nitro compounds form the products of oxidative coupling with halide and phenylsulfinate anions under the undivided electrolysis conditions. In all other cases, divided electrolysis is required.

Full text of DOI:10.1007/s11172-006-0007-7

Russian Chemical Bulletin, International Edition, Vol. 54, No. 7, pp. 1585—1592, July, 2005
1585
Electrooxidative coupling of salts of nitro compounds with halide, nitrite,
cyanide, and phenylsulfinate anions
A. I. Ilovaisky,ꢀ V. M. Merkulova, Yu. N. Ogibin, and G. I. Nikishin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5328. Еꢀmail: ilov@ioc.ac.ru
Electrolysis of salts of primary and secondary nitro compounds (nitroethane, 1ꢀ and
2ꢀnitropropanes, nitrocyclohexane, and nitrocycloheptane) in the presence of excess halide,
nitrite, cyanide, and phenylsulfinate anions under undivided and divided amperostatic elecꢀ
trolysis conditions in a twoꢀphase medium (CH2Cl2/H2O) produces geminal nitrohalides
(35—85% yields), dinitro compounds (15—51%), nitronitriles (6—27%), and nitrosulfones
(50—70%). The salts of secondary nitro compounds form the products of oxidative coupling
with halide and phenylsulfinate anions under the undivided electrolysis conditions. In all other
cases, divided electrolysis is required.
Key words: nitroethane, 1ꢀ and 2ꢀnitropropanes, nitrocyclohexane, nitrocycloheptane,
halides, nitrites, cyanides, phenylsulfinates, electrolysis, electrooxidative coupling, gemꢀ
nitrohalides, gemꢀdinitro compounds, gemꢀnitronitriles, gemꢀnitrosulfones.
Oxidative coupling of salts of nitro compounds with
inorganic and organic anions is one of the main methods
for introducing different functional groups into the
αꢀposition of aliphatic and alicyclic nitro compounds.1,2
This method using predominantly chemical oxidants
(Cl2, Br2, I2, AgNO3, K3Fe(CN)6, Nꢀhalosuccinimides,
(NH4)2S2O8, and others) gave geminal nitrohalides,3—10
nitroazides,11—14 dinitro compounds,15—18 nitroꢀ
nitriles,17,18 nitrosulfones,7,17,19 and nitroimidazoles.20
Only dinitro compounds and nitroazides were syntheꢀ
sized by electrochemical oxidation,21—25 although, as
shown by our work on the electrosynthesis of geminal
azidonitro compounds,25 this variant of preparation of
αꢀsubstituted nitro compounds have substantial advanꢀ
tages over traditional chemical methods because excess
oxidant can be replaced by ecologically pure electric curꢀ
rent. Therefore, it is undoubtedly interesting and urgent
to study the electrooxidative coupling of salts of nitro
compounds with inorganic and organic anions for the
development of methods of electrosynthesis of nitro comꢀ
pounds substituted in the αꢀposition by different funcꢀ
tional groups.
dia, viz., CH2Cl2—aqueous solutions of NaCl, NaBr, NaI,
NaNO2, NaCN, and PhSO2Na in a volume ratio of 2 : 1,
under both undivided (UDE) and divided electrolysis
(DE) conditions using 0.1 M aqueous solutions of NaOH
or H2SO4 as catholytes. An advantage of the twoꢀphase
system is a possibility to extract the coupling products
into the organic phase during electrolysis. This decreases
the probability of their hydrolysis to carbonyl compounds
and (in the case of primary nitro compounds) deprotoꢀ
nation and subsequent side reactions.
Electrooxidative coupling of salts of nitro comꢀ
pounds 1а—е with halide anions was carried out using
tenfold excess of sodium halide. The reaction mainly afꢀ
fords αꢀnitrohalides 2—4 and αꢀnitrodihalides 5 and 6
(Scheme 1, Table 1).
Electrolysis of the nitroethane salt (1а) in a twoꢀphase
system CH2Cl2—aqueous solution of NaBr affords
1ꢀbromoꢀ1ꢀnitroethane (3а) in a yield of only 5% in UDE
and 15% in DE using a 0.1 M solution of NaOH as the
catholyte. Geminal nitrobromide 3а was obtained in a
satisfactory yield (64%) only by the electrolysis of the
nitroethane salt in the presence of bromide anions using
DE and 0.1 M H2SO4 as the catholyte (see Table 1, enꢀ
tries 8—10). We have earlier found a similar effect for
electrochemical azidation,25 which is related, most likely,
to the unstable final products in an alkaline medium. For
instance, the pH of the aqueous phase for UDE electrolyꢀ
sis increases from 9 to 11 due to cathodic alkalization.
When DE is used, the pH of the anolyte decreases from 9
to 7—8 during electrolysis (catholyte 0.1 M H2SO4) and
To solve this problem, we used Na salts of primary and
secondary nitroalkanes (nitroethane, 1ꢀ and 2ꢀnitroꢀ
propanes) and nitrocycloalkanes (nitrocyclohexane and
nitrocycloheptane), which were subjected to electroꢀ
oxidation in the presence of excess halide, nitrite, cyaꢀ
nide, and phenylsulfinate anions. As in the previously
described case25 of coupling of nitro compound salts with
azide anions, the study was carried out in twoꢀphase meꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1539—1546, July, 2005.
1066ꢀ5285/05/5407ꢀ1585 © 2005 Springer Science+Business Media, Inc.

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Ilovaisky et al.
Scheme 1
Compound
R1
H
H
R2
Me
Et
Compound
R1R2
(CH2)5
(CH2)6
a
b
c
d
e
Me
Me
Reagents and conditions: i, DE, CH2Cl2—H2O (2 : 1), catholyte 0.1 M H2SO4, NaHal (10 equiv.), 2—5 F mol–1, 8—10 °C; ii, UDE,
CH2Cl2—H2O (2 : 1), NaHal (10 equiv.), 2.5—8 F mol–1, 8—10 °C.
Scheme 2
remains almost unchanged in the case of an alkaline or
neutral catholyte. Halonitro compounds that formed are
sensitive, most likely, to a change in the pH of the aqueꢀ
ous phase, because they have a more acidic αꢀproton than
the starting nitro compounds. Under the optimum condiꢀ
tions, the conversion of salts 1а,b is 68—95% when 2 F
electricity is passed per mole of the salt, and the yield of
monohalogenation products 2a,b—4a,b is 55—68%. The
electrolysis of salt 1b in the presence of NaCl and NaBr
affords dihalonitropropanes 5 and 6 along with monoꢀ
halogenation products 2b and 3b. When the amount of
passed electricity increases to 5 F mol–1, compounds 5
and 6 become the main electrolysis products (Table 1,
entries 3 and 12). The corresponding diiodonitro comꢀ
pounds are not formed under these conditions.
Scheme 3
Salts of secondary nitro compounds (1с—е), unlike
their primary analogs, can be coupled with halide anions
under the undivided electrolysis conditions as well. The
yield of the corresponding coupling products changes
from 35 to 43% for 2с—е and from 60 to 85% for 3с—е
and 4с—е at the 75—100% conversion of salts 1с—е (see
Table 1). It should be mentioned that the conversion of
salt 1е is lower, as a rule, than that of 1d, and an increase
in the amount of electricity passed during their electrolyꢀ
sis gives no effect on the yield of the target products.
Products 2—4 can be formed by both the reactions of
salts 1 with electrogenerated molecular chlorine, bromine,
or iodine (Hal2) (Scheme 2) and oxidative addiꢀ
tion11,12,17,18 (Scheme 3).
X = Hal, NO2, CN, PhSO2
salt 1, which is an active acceptor of radicals26, and/or the
Х– anions undergo coupling with nitroalkyl radicals A.
Stable radical anions B that formed are transformed into
final products 2—4 due to subsequent oxidation (see
Scheme 3). Most likely, the mechanism presented in
Scheme 3 is correct also for the electrooxidative coupling
of nitro compound salts with nitrite, cyanide, and phenylꢀ
sulfinate anions.
These reactions start from radical generation due to
the oneꢀelectron oxidation of a substrate with the lowest
oxidation potential. Then, the generated radicals add to

Electrooxidative coupling of nitro salts
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 7, July, 2005
1587
Table 1. Electrooxidative coupling of Na salts of nitroethane (1а),
1ꢀ and 2ꢀnitropropanes (1b,с), nitrocyclohexane (1d), and
nitrocycloheptane (1е) with halide anions using divided and
undivided electrolysis conditionsа
in the case of chloride anions (see Scheme 3). A relative
amount of 2,3ꢀdimethylꢀ2,3ꢀdinitrobutane (7), which is
the dimerization product of radicals А21,29 formed by couꢀ
pling of salt 1с with halide anions allows one to estimate
the participation of αꢀnitroalkyl radicals А in the formaꢀ
tion of radical anions В (see Scheme 3):
Entry Salt Electroꢀ
lyzer
Q
Converꢀ
sion
Yield
of products
(%) 2—6, 8 (%)b
/F mol–1
Coupling of salts 1а—е with NaCl
1
2
1a
1b
DE
DE
2
2
68
70
2a (62)
2b (68),
5 (2)с
3
1b
DE
5
100
2b (8)с,
5 (53)
For instance, in the presence of NaI, product 7 is not
formed; in the case of NaBr, its amount is not higher
than 5%, for tenfold excess NaCl 12%, and for threefold
excess NaCl increases up to 45%; the same increase in the
yield of dimer 7 is provided by a decrease in the current
density from 100 to 20 mA cm–2. Thus, an increase in the
sodium chloride concentration and current density favors
the predominant oxidation of chloride anions rather than
salts of nitro compounds. A similar effect has been obꢀ
served previously for the electrochemical chlorination of
the dinitroethane anion.30
Electrooxidative coupling of salts 1d,e with halide anꢀ
ions is usually accompanied by the competitive electroꢀ
oxidative hydrolysis of the starting salts28,29,31 with the
formation of ketones 8d,e, and the amount of ketone
increases substantially on going from salt 1d to salt 1е.
This fact can be explained by a facilitated change in the
hybridization of the reaction center from sp2 to sp3 upon
the conversion of 1d,e into products 2—4 (Scheme 4) in
the case of the sixꢀmembered ring (n = 1), because it is
related to a decrease in the internal strain in the ring. In
the case of the sevenꢀmembered ring (n = 2), by contrast,
keeping the planar geometry for the formation of ketone 8
is energetically favorable.32,33 This rule is also correct for
the coupling of salts of nitro compounds with nitrite,
cyanide, and phenylsulfinate anions.
4
5
1c
1d
UDE
UDE
4
2.5
80
90
2c (43)d
2d (37),
8d (7)
6
7
1e
1e
UDE
UDE
4
8
52
95
2e (35),
8e (10)
2e (15),
8e (12)
Coupling of salts 1а—е with NaBr
8
9
10
11
1a
1а
1a
1b
UDE
2
2
2
2
90
95
95
93
3а (5)с
3а (15)
3а (64)
3b (67),
6 (9)с
3b (5)с,
6 (53)
3c (80) f
3d (85),
8d (2)с
3e (60),
8e (22)
e
DE
DE
DE
12
1b
DE
5
100
13
14
1c
1d
UDE
UDE
3
2
100
100
15
1e
UDE
4
87
Coupling of salts 1а—е with NaI
16
17
18
19
1a
1b
1с
1d
DE
DE
UDE
UDE
2
2
4
4
82
88
93
77
4a (55)
4b (63)
4c (75)
4d (80),
8d (3)с
4e (62),
8e (25)
20
1e
UDE
4
75
а
Conditions: 2—5 mmoles of salt 1, 10 equiv. of NaHal,
20—30 mL of CH2Cl2, 10—15 mL of water, vigorous stirring,
8—10 °C, catholyte for DE 0.1 M H2SO4, current density
100 mA cm–2 for UDE and 50 mA cm–2 for DE.
b Preparative yield calculated to converted salt 1.
c According to the GLC data.
Scheme 4
d 2,3ꢀDimethylꢀ2,3ꢀdinitrobutane (7) is also formed in 12% yield.
е Catholyte is 0.1 M NaOH.
f Compound 7 is also formed in 5% yield.
Based on the oxidation potentials of the anions (2I–/I2
Е0 = 0.536 V, 2Br–/Br2 E0 = 1.087 V, 2Cl–/Cl2 E0 =
–
1.395 V,27 RCH=NO2 E1/2 = 0.82—0.9 V (SCE)),28 we
n = 1 (d), 2 (e)
can conclude that the reaction proceeds mainly via
Scheme 2 during electrooxidative bromination and iodiꢀ
nation of salts 1, while anions of salts 1 are also oxidized
Unlike the reactions with halide anions, the electroꢀ
oxidative coupling of salts 1а—е with nitrite, cyanide, and

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Ilovaisky et al.
Scheme 5
Reagents and conditions: i, divided cell, CH2Cl2—H2O (2 : 1), catholyte 0.1 M NaOH or H2SO4, 2 equiv. NaNO2, NaCN, and
PhSO2Na, 2—3 F mol–1, 8—10 °C; ii, undivided cell, CH2Cl2—H2O (2 : 1), 2 equiv. PhSO2Na, 2 F mol–1, 8—10 °C.
phenylsulfinate anions (Scheme 5, Table 2) was carried
out at a salt—anion ratio of 1 : 2. The further increase in
this ratio is unreasonable because of a decrease in the
current efficiency for the target products, and the yield
also decreased for the geminal dinitro compounds and
αꢀnitronitriles. Most likely, the competitive oxidation of
the X– anions produces undesirable byꢀproducts when
the oxidation potentials of salts 1 and anions Х– are
close (for example, E1/2(RCH=NO2) = 0.82—0.9 V,
E1/2(NO2–) = 0.87—1.05 V 28 (SCE)); the yield of couꢀ
pling products is higher for the reactions with phenylꢀ
sulfinate anions (E1/2 ~0.63 V).34 In turn, a decrease in
the concentration of Х– anions increases the degree of
competitive electrooxidative hydrolysis of the nitro comꢀ
pound salts.
Coupling of salts 1a—е with nitrite anions was carried
out under the DE conditions using 0.1 M NaOH as the
catholyte. In this case, gemꢀdinitro compound 9d is formed
in approximately 50% yield (see Scheme 5, Table 2, enꢀ
tries 1—5), while the yields of the gemꢀdinitro compounds
are substantially lower for other substrates. When UDE is
used, the yield of 9d does not exceed 5%. The electroꢀ
chemical coupling of salt 1а with nitrite anions was earlier
carried out with a high yield of 1,1ꢀdinitroethane (>80%)
under the divided electrolysis conditions using powdered
silver as an anode.22 The Ag+ cations that formed act as a
mediator (oneꢀelectron oxidant).16,35 The yield of the
coupling products on the Pt anode under comparable
conditions did not exceed 30%,22 which agrees with our
data. A low yield of the target products is caused, most
likely, by the destruction of the gemꢀdinitro compounds
and their anions due to side reactions initiated by decomꢀ
position products of polynitroalkyl radicals.36
the UDE and DE conditions. However, the yield of
αꢀnitronitriles does not exceed 20% even for DE (see
Table 2, entries 6—11). An attempt to obtain coupling
products with salts of primary nitro compounds 1a,b failed,
which is probably related to unstable products formed
under the electrolysis conditions. In addition, the process
is complicated by the hydrolysis of the nitrile group in the
product to the amide group, which occurs (although to a
less extent) even when an acidic catholyte is used and is
accompanied by the formation of considerable amounts
of ketones 8. Electrolysis in methanol affords a mixture of
αꢀnitronitrile and the corresponding imino ester 14, and
the ketone amount in the reaction mixture decreases subꢀ
stantially (see Table 2, entry 10).
The electrooxidative coupling of salts of primary
nitroalkanes 1а,b with phenylsulfinate anions occurs effiꢀ
ciently under DE using an alkaline catholyte (0.1 M
NaOH). In this case, nitrosulfones 11а,b are formed in
55—58% yield at the 82—85% conversion of salts 1а,b (see
Scheme 5, Table 2). Unlike the primary salts, the salts of
secondary nitro compounds 1c—е form the corresponding
sulfones under the undivided electrolysis conditions. The
yield of nitrosulfones 11с—d is 54—70%. The low yield of
nitrosulfone 11е (27%) is caused by the competitive
electrooxidative hydrolysis of salt 1е and the formation of
1,1ꢀbis(phenylsulfonyl)cycloheptane (15) (yield 23%).
Thus, the study of electrooxidative coupling of salts of
primary and secondary nitro compounds with halide, niꢀ
trite, cyanide, and phenylsulfinate anions under the undiꢀ
vided and divided amperostatic electrolysis conditions in
a twoꢀphase methylene dichloride—water system showed
that salts of secondary nitroalkanes form coupling prodꢀ
ucts with halide and phenylsulfinate anions under the
undivided electrolysis conditions, while divided electrolyꢀ
sis is required in all other cases.
Electrooxidative coupling of salts of secondary nitro
compounds 1с—е with cyanide anions occurs under both

Electrooxidative coupling of nitro salts
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 7, July, 2005
1589
Table 2. Electrooxidative coupling of Na salts of nitroethane (1а), 1ꢀ and 2ꢀnitropropanes (1b,с),
nitrocyclohexane (1d), and nitrocycloheptane (1е) with nitrite, cyanide, and phenylsulfinate anions
using divided and undivided electrolysis conditionsа
Entry
Salt
Electrolysis
(catholyte)
Q
Conversion
(%)
Yield (%)b
of products 8—14
/F mol–1
c
Coupling of salts 1a—e with NaNO2
1
2
3
4
5
1a
1b
1c
1d
1e
DE (NaOH)
DE (NaOH)
DE (NaOH)
DE (NaOH)
DE (NaOH)
2
2
2
3
3
80
75
90
90
95
9a (35)
9b (30)
9c (40)
8d (17), 9d (51)
8e (48), 9e (15)
Coupling of salts 1c—e with NaCN
6
7
1c
1d
DE (H2SO4)
UDE
2
2
100
98
10с (12)
12 (4)
8d (15), 10d (7)
13 (5)
8
9
10
1d
1d
1d
DE (NaOH)
DE (H2SO4)
DE (H2SO4)d
2
2
2
98
90
93
8d (20), 10d (15), 13 (10)
8d (18), 10d (27), 13 (8)
8d (5), 10d (20)
14 (15)
11
1e
DE (H2SO4)
2
95
8e (75), 10e (6)
Coupling of salts 1a—e with PhSO2Na
12
13
14
15
16
1a
1b
1c
1d
1e
DE (NaOH)
DE (NaOH)
UDE
2
2
2
2
2
85
82
100
95
11a (55)
11b (58)
11c (70)
8d (7), 11d (54)
8e (25), 11e (27)e
UDE
UDE
95
а Conditions: 2—5 mmoles of salt 1; 2 equiv. of NaNO2, NaCN, or PhSO2Na; 20—30 mL of
CH2Cl2; 10—15 mL of water; vigorous stirring; 8—10 °С, catholyte using DE: 0.1 M NaOH or 0.1 M
H2SO4; current density 100 mA cm–2 for UDE and 50 mA cm–2 for DE.
b Preparative yield calculated to converted salt 1.
с For syntheses of salts 1, 1.5ꢀfold excess NaOH was used.
d Solvent MеОH, catholyte 0.1 M H2SO4 in MеОH.
e 1,1ꢀBis(phenylsulfonyl)cycloheptane (15) is also formed in 23% yield.
mꢀchloroperoxybenzoic acid in acetonitrile in the presence of
Na2HPO4.
Experimental
Electrooxidative coupling of Na salts of nitro compounds with
halide anions in a divided cell in a twoꢀphase system (general
procedure). Nitro compound (2—5 mmol) was added to a 3 M
aqueous solution of NaOH (1 equiv.), and the mixture was
stirred until the substrate transformed completely into its salt
(1—2 h). The resulting solution was diluted with water, sodium
halide (10 equiv.) and CH2Cl2 (20—30 mL) were added to preꢀ
pare the anolyte. Electrolysis was carried out using a ceramic
diaphragm, Pt anode (4 cm2), and stainless steel cathode (4 cm2)
with vigorous stirring of the anolyte under the conditions given
in Table 1 and cooling in an ice bath. Catholytes were 0.1 M
solutions of NaOH or H2SO4. To monitor the course of the
reaction, an aliquot from the aqueous phase of the anolyte was
acidified with AcOH and extracted with CH2Cl2, and the exꢀ
tract was analyzed by GLC. After the end of electrolysis, the
anolyte was acidified with AcOH (1 mL), the organic layer
was separated, and the aqueous solution was extracted with
CH2Cl2 (2×20 mL). The combined organic layers were
washed with water (2×20 mL), dried with MgSO4, analyzed
by GLC, and evaporated on a rotary evaporator in vacuo without
heating. Electrolysis products were isolated by vacuum distillaꢀ
1
H and 13C NMR spectra were recorded on Bruker ACꢀ200,
Bruker WMꢀ250, and Bruker AMꢀ300 spectrometers using
CDCl3 as a solvent. IR spectra were measured on a Specord
Mꢀ82 spectrometer as KBr pellets. Laboratory power sources
(B5ꢀ44 and B5ꢀ50) with output current stabilization were used
as dc generators. The amount of passed electricity was measured
using an electron coulometer with digital indication and a curꢀ
rent measurement limit of 20 A (Design Bureau of the Institute
of Organic Chemistry, Russian Academy of Sciences). Elecꢀ
trode materials were Pt (anode) and stainless steel (cathode).
GLC analysis was carried out using a Varianꢀ3700 chromatoꢀ
graph (flameꢀionization detector, glass columns 2×0.003 m, staꢀ
tionary phase 5% SEꢀ30 and 5% XEꢀ60 on Chromaton NꢀAW).
TLC analysis was carried out using chromatographic plates
Silufol UVꢀ254. Silica gel L 40/100 µm was used for flash
chromatography. Petroleum ether (b.p. 40—60 °C), CH2Cl2,
ethyl acetate, and MeOH were purified by standard methods.
Nitroethane, 1ꢀ and 2ꢀnitropropanes, and nitrocyclohexane
were commercial reagents (Aldrich). Nitrocycloheptane37 was
obtained by the oxidation of cycloheptanone oxime with

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Ilovaisky et al.
tion or flash chromatography on silica gel (eluent 0.5% AcOEt
1ꢀBromoꢀ1ꢀnitrocycloheptane (3d).41 1H NMR, δ: 1.28—1.86
(m, 6 H); 2.45 (br.t, 4 H, J = 5.9 Hz). 13C NMR, δ: 23.52
(C(3)); 23.77 (C(4)): 39.23 (C(2)); 94.74 (C(1)).
1
in petroleum ether) and identified by their H and 13C NMR
spectra.
1ꢀChloroꢀ1ꢀnitroethane (2а),5 b.p. 61 °C (50 Torr),
nD16 1.4245. 1H NMR, δ: 2.02 (d, 3 H, J = 6.6 Hz); 5.93 (q, 1 H,
J = 6.6 Hz). 13C NMR, δ: 23.56 (C(2)); 87.65 (C(1)).
1ꢀChloroꢀ1ꢀnitropropane (2b),6 b.p. 36 °C (15 Torr),
nD 1.4250. H NMR, δ: 1.07 (t, 3 H, J = 7.2 Hz); 2.15—2.44
(m, 2 H); 5.80 (t, 1 H, J = 6.6 Hz). 13C NMR, δ: 8.86 (C(3));
30.50 (C(2)); 92.85 (C(1)).
1ꢀBromoꢀ1ꢀnitrocycloheptane (3е).41 1H NMR, δ: 1.66 (br.s,
8 H); 2.60, 2.84 (both dd, 2 H each, J = 15.5 Hz, J = 7.5 Hz).
13C NMR, δ: 23.33, 28.09 (C(3), C(4)); 43.36 (C(2));
99.67 (C(1)).
2ꢀIodoꢀ2ꢀnitropropane (4c),7 b.p. 73—75 °C (15 Torr),
20
1
16
1
nD 1.5320. H NMR, δ: 2.38 (s, 6 H). 13C NMR, δ: 35.69
(C(1)); 63.14 (C(2)).
1ꢀBromoꢀ1ꢀnitroethane (3a),6 b.p. 50—52 °C (15 Torr),
nD16 1.4780. 1H NMR, δ: 2.17 (d, 3 H, J = 6.6 Hz); 6.04 (q, 1 H,
J = 6.6 Hz). 13C NMR, δ: 24.08 (C(2)); 74.60 (C(1)).
1ꢀBromoꢀ1ꢀnitropropane (3b),6 b.p. 61 °C (15 Torr),
nD 1.4710. H NMR, δ: 1.08 (t, 3 H, J = 7.2 Hz); 2.20—2.52
(m, 2 H); 5.88 (t, 1 H, J = 6.6 Hz). 13C NMR, δ: 10.14 (C(C(3));
30.90 (C(2)); 81.21 (C(1)).
1ꢀIodoꢀ1ꢀnitrocyclohexane (4d).42 1H NMR, δ: 1.38—1.70
(m, 6 H); 2.33 (m, 2 H); 2.53 (dt, 2 H, J = 14.4 Hz, J = 5.9 Hz).
13C NMR, δ: 24.04 (C(4)); 24.64 (C(3)); 42.32 (C(2));
74.10 (C(1)).
1ꢀIodoꢀ1ꢀnitrocycloheptane (4e).7 1H NMR, δ: 1.56, 1.63
(both m, 4 H each); 2.72, 2.87 (both dt, 2 H each, J = 15.5 Hz,
J = 5.3 Hz). 13C NMR, δ: 24.05, 27.77 (C(3), C(4)); 45.88
(C(2)); 77.81 (C1)).
2,3ꢀDimethylꢀ2,3ꢀdinitrobutane (8),43 m.p. 202 °C. 1H NMR,
δ: 1.73 (s, 12 H). 13C NMR, δ: 23.06 (C(1), C(4)); 91.51
(C(2), C(3)).
20
1
1ꢀIodoꢀ1ꢀnitroethane (4a),9 b.p. 75—78 °C (20 Torr),
nD16 1.5360. 1H NMR, δ: 2.33 (d, 3 H, J = 6.6 Hz); 6.37 (q, 1 H,
J = 6.6 Hz). 13C NMR, δ: 26.29 (C(2)); 45.98 (C(1)).
1ꢀIodoꢀ1ꢀnitropropane (4b), b.p. 76—80 °C (15 Torr),
20
nD 1.5274. 1H NMR, δ: 1.01 (t, 3 H, J = 7.9); 2.18—2.51
Electrooxidative coupling of Na salts of nitro compounds with
cyanide and phenylsulfinate anions in a divided cell in a twoꢀphase
system. The reaction was carried out according to the above
procedure. Products were isolated by flash chromatography on
silica gel (eluent 0.5—2% AcOEt in petroleum ether) and idenꢀ
(m, 2 H); 6.13 (pseudoꢀt, 1 H, J = 6.6 Hz). 13C NMR, δ: 12.05
(C(3)); 32.58 (C(2)); 55.29 (C(1)). Found (%): C, 16.33; H, 2.72;
N, 6.22. C3H6INO2. Calculated (%): C, 16.76; H, 2.81; N, 6.52.
1,1ꢀDichloroꢀ1ꢀnitropropane (5).38 1H NMR, δ: 1.18 (t, 3 H,
J = 7.2 Hz); 2.73 (q, 2 H, J = 7.2 Hz). 13C NMR, δ: 10.57
(C(3)); 40.26 (C(2)); 114.90 (C(1)).
1
tified by their IR and H, 13C NMR spectra (see Table 2).
1,1ꢀDinitroethane (9a).16 1H NMR, δ: 2.14 (d, 3 H, J =
6.6 Hz); 6.30 (q, 1 H, J = 6.6 Hz). 13C NMR, δ: 16.97 (C(2));
108.18 (C(1)).
1,1ꢀDibromoꢀ1ꢀnitropropane (6).39 1H NMR, δ: 1.21 (t, 3 H,
J = 7.2 Hz); 2.89 (q, 2 H, J = 7.2 Hz). 13C NMR, δ: 11.73
(C(3)); 42.96 (C(2)); 89.43 (C(1)).
1,1ꢀDinitropropane (9b).43 1H NMR, δ: 1.15 (t, 3 H, J =
7.0 Hz); 2.55 (quint, 3 H, J = 6.8 Hz); 6.11 (t, 1 H, J = 6.6 Hz).
13C NMR, δ: 8.54 (C(3)); 24.81 (C(2)); 112.95 (C(1)).
2,2ꢀDinitropropane (9c).17 1H NMR, δ: 2.16 (s, 6 H).
13C NMR, δ: 23.93 (C(1)); 117.67 (C(2)).
Electrooxidative coupling of Na salts of nitro compounds with
halide anions in an undivided cell (general procedure). Nitro comꢀ
pound (2 mmol) was mixed with CH2Cl2 (20 mL) and a 0.2 M
aqueous solution of NaOH (1 equiv., 10 mL). The mixture was
stirred for 1—3 h until complete transformation of the substrate
into the corresponding salt (the presence of the nitro compound
in an organic phase was monitored by GLC), and sodium halide
(10 equiv.) was added. The resulting mixture was placed in an
electrolyzer with a Pt anode (4 cm2) and a stainless steel cathode
(4 cm2). The distance between the electrodes was 10 mm. Direct
current was passed under the conditions given in Table 1. The
course of the reaction was monitored and the products were
isolated and identified according to the above described proꢀ
cedures.
1,1ꢀDinitrocyclohexane (9d).17,18 1H NMR, δ: 1.59 (m, 2 H);
1.70, 2.59 (both m, 4 H each). 13C NMR, δ: 22.34 (C(3)); 23.43
(C(4)); 32.87 (C(2)); 120.17 (C(1)).
1
1,1ꢀDinitrocycloheptane (9e). H NMR, δ: 1.65—1.89 (m,
4 H); 1.69 (s, 4 H); 2.71 (m, 4 H). 13C NMR, δ: 22.92, 29.11
(C(3), C(4)); 36.53 (C(2)); 123.95 (C(1)). Found (%): C, 44.38;
H, 6.22; N, 14.70. C7H12N2O4. Calculated (%): C, 44.68;
H, 6.43; N, 14.88.
2ꢀMethylꢀ2ꢀnitropropionitrile (10c).17,18 1H NMR, δ: 2.00
(s, 6 H). 13C NMR, δ: 26.13 (C(1)); 80.27 (C(2)); 115.86 (CN).
1ꢀNitrocyclohexylcarbonitrile (10d).17,18 1H NMR, δ:
1.21—1.44 (m, 1 H); 1.59—1.87 (m, 3 H); 1.90—2.05 (m, 2 H);
2.20 (td, 2 H, J = 12.5 Hz, J = 3.9 Hz); 2.45 (d, 2 H, J =
13.1 Hz). 13C NMR, δ: 22.78 (C(3)); 23.78 (C(4)); 35.06 (C(2));
86.17 (C(1)); 114.84 (CN).
1ꢀNitrocycloheptylcarbonitrile (10e). 1H NMR, δ: 1.56—1.82
(m, 6 H); 1.82—2.02 (m, 2 H); 2.45 (m, 4 H). 13C NMR, δ:
22.75, 27.49 (C(3), C(4)); 38.28 (C(2)); 89.29 (C(1)); 115.89
(CN). Found (%): C, 57.02; H, 7.08; N, 16.35. C8H12N2O2.
Calculated (%): C, 57.13; H, 7.19; N, 16.65.
2ꢀMethylꢀ2ꢀnitropropanamide (12),44 m.p. 117—119 °C. IR,
ν/cm–1: 3432, 3188 (NH2); 1692 (CО); 1548, 1356 (NO2).
1H NMR, δ: 1.87 (s, 6 H); 5.89 and 6.13 (both br.s, 2 H).
1ꢀNitrocyclohexylcarboxamide (13),44 m.p. 118—120 °C.
1H NMR, δ: 1.40 (m, 3 H); 1.63 (m, 1 H); 1.72 (m, 2 H); 2.12
2ꢀChloroꢀ2ꢀnitropropane (2c),7 b.p. 38 °C (20 Torr),
20
1
nD 1.4264. H NMR, δ: 2.16 (s, 6 H). 13C NMR, δ: 30.62
(C(1)); 100.05 (C(2)).
1ꢀChloroꢀ1ꢀnitrocyclohexane (2d).10 1H NMR, δ: 1.28—1.46
(m, 1 H); 1.53—1.85 (m, 5 H); 2.31 (dt, 2 H, J = 13.8 Hz, J =
5.3 Hz); 2.42 (ddd, 2 H, J = 13.8 Hz, J = 8.5 Hz, J = 5.3 Hz).
13C NMR, δ: 23.02 (C(3)); 24.02 (C(4)); 38.37 (C(2));
103.82 (C(1)).
1ꢀChloroꢀ1ꢀnitrocycloheptane (2e).40 1H NMR, δ: 1.69
(m, 8 H); 2.43 (dt, 2 H, J = 15.9 Hz, J = 5.3 Hz); 2.73 (dt, 2 H,
J = 15.9 Hz, J = 5.3 Hz). 13C NMR, δ: 22.93, 28.32 (C(3),
C(4)); 42.56 (C(2)); 110.71 (C(1)).
2ꢀBromoꢀ2ꢀnitropropane (3c),7 b.p. 60 °C (20 Torr),
nD 1.4720. H NMR, δ: 2.25 (s, 6 H). 13C NMR, δ: 32.32
16
1
(C(1)); 88.99 (C(2)).

Electrooxidative coupling of nitro salts
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 7, July, 2005
1591
(td, 2 H, J = 12.5 Hz, J = 4 Hz); 2.58 (d, 2 H, J = 13 Hz); 5.90
and 6.05 (both br.s, 2 H).
flash chromatography on silica gel (eluent 0.5—2% AcOEt in
petroleum ether) and identified by their 1H and 13C NMR specꢀ
tra. The results of analysis are presented in Table 2, entry 10.
Methyl (1ꢀnitrocyclohexyl)carboxyimidate (14).47 1H NMR,
δ: 1.50 (m, 6 H); 2.02, 2.45 (both m, 2 H each); 3.68 (s, 3 H);
7.65 (s, 1 H, NH). 13C NMR, δ: 22.18 (C(3)); 24.24 (C(4));
32.73 (C(2)); 54.28 (ОMе); 92.35 (C(1)); 167.28 (C=N).
1ꢀ(1ꢀNitroethyl)phenylsulfone (11a),45 m.p. 47—48 °C.
1H NMR, δ: 1.90 (d, 3 H, J = 6.6 Hz); 5.63 (q, 1 H, J = 6.6 Hz);
7.62 (t, 2 H, J = 7.2 Hz); 7.77 (t, 1 H, J = 7.2 Hz); 7.89 (d, 2 H,
J = 7.6 Hz). 13C NMR, δ: 13.32 (C(2)); 97.47 (C(1)); 129.58,
129.94 (C(2´), C(3´)); 133.93 (C(1´)); 135.53 (C(4´)).
1ꢀ(1ꢀNitropropyl)phenylsulfone (11b),18 m.p. 55—56 °C.
1H NMR, δ: 1.04 (t, 3 H, J = 7.2 Hz); 2.12—2.42 (m, 2 H); 5.45
(dd, 1 H, J = 10.5 Hz, J = 3.9 Hz); 7.61 (t, 2 H, J = 7.8 Hz); 7.77
(t, 1 H, J = 7.2 Hz); 7.89 (dd, 2 H, J = 7.8 Hz, J = 1.3 Hz).
13C NMR, δ: 9.93 (C(3)); 21.96 (C(2)); 103.65 (C(1)); 129.53,
130.02 (C(2´), C(3´)); 134.10 (C(1´)); 135.50 (C(4´)).
Electrooxidative coupling of Na salts of nitro compounds with
phenylsulfinate anions in an undivided cell. The reaction was carꢀ
ried out according to the above procedure. Products were isoꢀ
lated by crystallization from petroleum ether or using flash chroꢀ
matography on silica gel (eluent 0.5—10% AcOEt in petroleum
ether) and identified by the 1H and 13C NMR spectra (see
Table 2).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 03ꢀ03ꢀ32488)
and the Council on Grants of the President of the Russian
Federation (Program of State Support for Leading Scienꢀ
tific Schools of Russia, Grant NSh No. 2121ꢀ2003ꢀ3).
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1
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(11e),7
m.p.
1
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Received March 22, 2005;
in revised form April 29, 2005