Reactions of 2-methyleneadamantane and 2-benzylideneadamantane with acetyl nitrate

Article abstract of DOI:10.1134/S1070363216020092

The reactions of 2-methylene- and 2-benzylideneadamantane with acetyl nitrate have been studied. In the case of 2-methyleneadamantane, the reaction proceeds via addition of nitronium cation at the double bond followed by stabilization of 2-nitromethyl-2-adamantyl carbocation. In the case of 2-benzylidenadamantane, ortho-substitution at the benzene ring occurred predominantly.

Full text of DOI:10.1134/S1070363216020092

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 2, pp. 262–266. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © P.E. Krasnikov, V.A. Osyanin, D.V. Osipov, Yu.N. Klimochkin, 2016, published in Zhurnal Obshchei Khimii, 2016, Vol. 86, No. 2,
pp. 234–238.
Reactions of 2-Methyleneadamantane
and 2-Benzylideneadamantane with Acetyl Nitrate
P. E. Krasnikov, V. A. Osyanin, D. V. Osipov, and Yu. N. Klimochkin
Samara State Technical University, ul. Molodogvardeiskaya 244, Samara, 443100 Russia
e-mail: VOsyanin@mail.ru
Received October 5, 2015
Abstract—The reactions of 2-methylene- and 2-benzylideneadamantane with acetyl nitrate have been studied.
In the case of 2-methyleneadamantane, the reaction proceeds via addition of nitronium cation at the double
bond followed by stabilization of 2-nitromethyl-2-adamantyl carbocation. In the case of 2-benzylidenada-
mantane, ortho-substitution at the benzene ring occurred predominantly.
Keywords: acetyl nitrate, alkylideneadamantane, nitration, electrophilic addition, electrophilic substitution
DOI: 10.1134/S1070363216020092
Development of novel methods for the synthesis of
substituted adamantanes containing functional groups
at the bridging carbon atom and the study of their
biological activity have been the topics of a number of
reports in the field of cage compounds chemistry
[1–4]. Reactions of alkylideneadamantanes with nitro-
sating agents can serve for preparation of such
compounds. A few examples of reactions of alkenes
with acetyl nitrate to form usually a mixture of nitro-
acetylated and nitroxynitrated products have been
reported in the literature [5–11].
2-(Nitromethylene)adamantane was 3 was isolated
in 26% yield (Scheme 1). Apparently, the reaction of
2-methyleneadamantane
1
with acetyl nitrate
proceeded through a four-mem-bered transition state to
form carbocation A, its stabilization occurring either
via proton elimination or by attaching acetate anion to
form 2-(nitromethyl)-adamant-2-yl acetate 4 as the
major product.
2-(Nitromethyl)adamantan-2-ol 5 can be formed
during the decomposition of 2-(nitromethyl)adamant-
2-yl acetate 4 on silica in the presence of adsorbed
water. The subsequent retro-Henry reaction led to the
formation of 2-adamanone 6. In addition, adamanta-
none formation could be due to the direct oxidation of
2-methyleneadamantane (Scheme 2).
Extending our earlier studies [12–16] on the
chemistry of alkylideneadamantanes and their interac-
tions with electrophilic reagents, herein we report on
the reactions of 2-methyleneadamantane 1 and 2-
benzylideneadamantane 2 with acetyl nitrate (10%
molar excess) generated in situ from fuming HNO3 and
acetic anhydride in methylene chloride solution at 0°C.
In the case of 2-methyleneadamantane, a number of
the reaction products 3–7 were isolated by column
chromatography.
Finally, the formation of 2-methyl-2-adamantyl
nitrate 7 could be explained by the electrophilic addi-
tion of nitric acid at the double bond. It should be
noted that the addition of nitric acid to alkenes to form
Scheme 1.
OAc
NO2
+
ONO2
CH3
OH
CH2
O
AcONO2
+
+
+
NO2
NO2
4 (44%)
1
6 (4%)
7 (4%)
3 (26%)
5 (7%)
262

REACTIONS OF 2-METHYLENEADAMANTANE
263
Scheme 2.
O
N+
NO2
NO2
.
. .
.
.
.
AcONO2
O
.
.
.
.
.
.
.
CH2
.
.
+
− H+
1
A
3
AcO−
OAc
NO2
4
OH
O
H3O+
4
NO2
−AcOH
−CH3NO2
5
6
Scheme 3.
NO2
NO2
NO2
Ph
Ph
Ph
Ph
AcONO2
+
+
ONO2
9 (19%)
OH
10 (5%)
2
8 (9%)
NO2
O
+
+
11 (48%)
6 (12%)
tertiary alkyl nitrates has been earlier described
in [17].
B via proton elimination. IR spectrum of nitroalkene 8
contained strong absorption bands corresponding to
vibrations of C–H bonds of adamantane fragment
(2851, 2920 cm–1), exocyclic double bond C=C
(1655 cm–1), and nitro group (1516, 1366 cm–1). Mass
spectrum of compound 8 contained a weak molecular
ion peak and a peak of [M – NO2]+ ion with m/z = 223
(Irel = 100%). The H NMR spectrum revealed certain
deshielding of the protons in the positions 1 and 3 of
the adamantane core (δ = 2.97 and 2.48 ppm).
The reaction of 2-benzylideneadamantane 2 with
acetyl nitrate also afforded a mixture of compounds 6,
8–11 isolated by column chromatography (Scheme 3).
Note that in the case of 2-benzylideneadamantane
2, both the bridging and benzylidene carbon atoms
could be involved in the electrophilic attack to generate
two different carbocations B and C (Scheme 4).
1
Formation of 2-[nitro(phenyl)methyl]adamantane 8
could be explained by the stabilization of carbocation
Nitronitrate 9 couls be regarded as a product
of interaction of nitroacetate 12, initially formed
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 2 2016

264
KRASNIKOV et al.
Scheme 4.
NO2
O2N
+
+
Ph
Ph
Ph
Ph
NO+2
NO+2
B
2
C
Scheme 5.
NO2
Ph
NO2
Ph
AcONO2
AcONO2
OAc
ONO2
−Ac2O
12
9
2
Scheme 6.
OAc
OH
O
Ph
Ph
NO2
Ph
AcONO2
H2O
NO2
−AcOH
−PhCH2NO2
13
2
14
6
1
from unstable carbocation B, with acetyl nitrate
(Scheme 5).
(phenyl)methanol 10. Its H NMR spectrum contained
the signal of strongly deshielded benzylic proton at
6.39 ppm and a broad singlet signal of hydroxyl group
at 2.83 ppm. As in the case of nitronitrate 9, the 13C
NMR spectrum of compound 10 contained 10 signals
of the adamantane moiety. The carbon atom adjacent
to the hydroxyl group resonated at 91.0 ppm. The
signal at 95.9 ppm was assigned to the carbon atom at
position 2 of the adamantane moiety.
IR spectrum of compound 9 contained the
absorption bands assigned to stretching of NO2 (νas
1531, νs 1358 cm–1) and ONO2 groups (1647, 1277,
837 cm–1). The signal of deshielded benzylic proton
was observed at 6.61 ppm in the 1H NMR spectrum. In
addition, the deshielding of the C1H and C3H protons
of the adamantane core was observed, that could be
explained by the influence of the electron-withdrawing
moieties. Generally, 13C NMR spectra 2,2-disubsti-
tuted adamantane core contain 7 signals. Since in most
cases conformational interconversion barrier of the
enantiomers is low, the dynamic symmetry plane
appears whereby three pairs of carbon atoms at the
positions 1 and 3, 4 and 9, 8 and 10 of adamantane
moiety become equivalent. However, the enhanced
steric hindrance hampers the rotation, and these pairs
of carbon atoms become magnetically nonequivalent.
As a result, the carbon atoms of adamantane moiety
will resonate as 10 signals instead of 7 in the 13C NMR
spectrum; that observed in the case of nitronitrate 9.
The value for the chemical shift of the carbon atom
associated with nitro group was of 97.8 ppm.
Formation of adamantanone 6 in the reaction of
alkene 2 with acetyl nitrate could be explained by
hydrolysis of unstable nitroacetate 13 (the latter
formed through the intermediate carbocation B) when
treating the reaction mixture to form unstable 2-
(nitrobenzyl)adamantan-2-ol 14, followed by the retro-
Henry reaction (Scheme 6).
In the case of 2-benzylidenadamantane 2, the
benzene ring might also be a site of the electrophilic
attack, and electrophilic aromatic substitution was the
major direction. The preferential formation of 2-(2-
nitrobenzylidene)adamantane 11 and the presence of a
minor amount (about 1%, according to GC–MS) of the
para-nitrated product could be explained by the fact
that electrophilic nitration at the ortho-position of the
benzene ring could occur probably via pre-
coordination of nitrating reagent with the double C=C
When eluting the reaction mixture on silica gel,
nitronitrate 9 transformed into (2-nitro-2-adamantyl)-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 2 2016

REACTIONS OF 2-METHYLENEADAMANTANE
265
bond. IR spectrum of nitro compound 11 contained the
absorption bands assigned to stretching of C–H bonds
of the adamantane fragment (2847, 2920 cm–1), double
СAd=С bond (1651 cm–1), aromatic ring (1605 cm–1),
isolated: 2-(nitromethylene)adamantane 3 (2.03 g,
26%), 2-(nitromethyl)adamant-2-yl acetate 4 (4.51 g,
44%), 2-(nitromethyl)adamantan-2-ol 5 (0.60 g, 7%),
2-adamantanone 6 (0.24 g, 4%), 2-methyl-2-adamantyl
nitrate 7 (0.34 g, 4%). Physico-chemical and spectral
parameters of compounds 3–7 coincided with those
reported in [11, 18].
1
and nitro group (1520, 1358 cm–1). The H NMR
spectral data clearly indicated the formation of the
ortho-substituted product; the 1H NMR spectrum
contained a signal of strongly deshielded proton at the
double bond, at 6.40 ppm.
Reaction of benzylideneadamantane 2 with 2-
acetyl nitrate was performed similarly, using a
solution of 4.48 g (0.02 mol) of 2-benzylidene-
adamantane 2 in 30 mL of methylene chloride and a
solution of acetyl nitrate prepared from 12 mL of
Ac2O, 1.3 mL of fuming HNO3 and 10 mL of methyl-
ene chloride. After silica gel column chromatography
(eluent – hexane–dichloromethane, 100 : 1), compound
8–11 and 2-adamantanone 6 (0.36 g, 12%) were isolated.
Noteworthily, reactions of methyleneadamantane 1
and benzylideneadamantane 2 with acetyl nitrate did
not affect the tertiary C–H bonds of adamantane moiety.
In summary, the reaction of 2-methylene-
adamantane with acetyl nitrate afforded a wide range
of the products due to generation of 2-nitromethyl-2-
adamantyl carbocation. In the case of 2-benzylidene-
adamantane 2, nitration of the benzene ring competed
with nitronium cation attack at the bridging carbon
atom of the adamantane scaffold.
2-[Nitro(phenyl)methylene]adamantane (8). Yield
0.48 g (9%), mp 108–110°С (hexane) (mp 108.5–
109.5°С [19]). IR spectrum (KBr), ν, cm–1: 2920, 2851
(CHAd), 1655 (СAd=C), 1516 (NO2), 1447, 1366 (NO2),
1
EXPERIMENTAL
1261, 1099, 953, 756, 733, 702. Н NMR spectrum
(CD3CN), δ, ppm: 1.81–2.03 m (12H, HAd), 2.48 br. s
1,3
Mass spectra were recorded using a Thermo
Finnigan Trace DSQ instrument by direct injection of
the material into the ion source at the ionizing
and 2.97 br. s (2H, H ), 7.34–7.37 m (2Н, Ph), 7.41–
Ad
7.44 m (3H, Ph). 13C NMR spectrum (CD3CN), δС,
ppm: 27.5 (2CH), 34.1 (2CH), 35.9 (CH2), 38.5
(2CH2), 38.6 (2CH2), 129.0 (2CHPh), 129.4 (2CHPh),
129.5 (CH4Ph), 132.0 (C1Ph), 142.4 (C–NO2), 149.5
(C2Ad). Mass spectrum, m/z (Irel, %): 269 (7) [М]+, 239
(7) [М – NO]+ 223 (100) [M – NO2]+, 211 (14) [M –
CNO2]+, 181 (6), 178 (5), 167 (13), 165 (12), 143 (9),
141 (10), 129 (13), 128 (17), 115 (22), 105 (36), 91
(28), 79 (11), 77 (14) [Ph]+. Found, %: C 75.90; H
7.01; N 5.11. C17H19NO2. Calculated, %: C 75.81; H
7.11; N 5.20.
1
electrons energy of 70 eV. H and 13C NMR spectra
(400 and 100 MHz, respectively) of the solutions in
CDCl3 or CD3CN were obtained using a JEOL JNM-
ECX400 spectrometer with internal TMS reference. IR
spectra were registered using a Shimadzu FTIR-8400S
spectrometer (KBr pellets). Elemental analysis was
performed using a EuroVector EA-3000 automated
CHNS analyzer. Melting points were determined by
capillary method using a PTP-M instrument.
Reaction of 2-methyleneadamantane 1 with acetyl
nitrate. Acetyl nitrate was obtained by adding 2.6 mL
of fuming (~96%) nitric acid to a mixture of 22.5 mL
of Ac2O and 20 mL of dichloromethane with stirring at
0–5°C. The nitrating mixture was added dropwise to a
solution of 6 g (0.04 mol) of 2-methyleneadamantane 1
in 60 mL of dichloromethane upon vigorous stirring at
0–5°C. The mixture was incubated during 12 h at 3–4°C
and then poured into 150 g of ice. The organic layer
was separated, and the aqueous layer was extracted
with dichloromethane. The extract was washed with
NaHCO3, dried with Na2SO4, and evaporated in vacuum.
The residue was purified by silica gel column chro-
matography eluting with a hexane–dichloromethane
mixture (100 : 1). The following compounds were
(2-Nitro-2-adamantyl)(phenyl)methyl nitrate (9).
Yield 1.26 g (19%), mp 149–151°С. IR spectrum, ν,
cm–1: 2916–2854 (CHAd), 1647 (ONO2), 1531 (NO2),
1
1516, 1358 (NO2), 1277 (ONO2), 837 (ONO2). Н
NMR spectrum (CD3CN), δ, ppm: 1.77–2.06 m (12H,
HAd), 2.48 s (1H, HAd), 3.03 s (1H, HAd), 6.61 s (1H,
CH), 7.22–7.44 m (5Н, Ph). 13С NMR spectrum
(CD3CN), δC, ppm: 25.9 and 26.2 (2СH5,7), 31.6 and
31.8 (2СH1,3), 33.3 (СH2), 33.6 (CH2), 33.7 (CH2),
38.5 (CH2), 38.6 (CH2), 81.1 (C–O), 97.8 (C2), 126.1
2,6
3,5
(C ), 129.0 (C ), 129.9 (C4Ph), 149.5 (C1Ph). Mass
Ph
Ph
spectrum, m/z (Irel, %): 239 (5) [C17H19O]+, 223 (12)
[C17H19]+, 211 (60) [C16H19]+, 150 (23), 105 (100), 91
(85). Found, %: С 61.39; H 5.97; N 8.33. C17H20N2O5.
Calculated, %: C 61.44; H 6.07; N 8.43.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 2 2016

266
(2-Nitro-2-adamantyl)(phenyl)methanol
KRASNIKOV et al.
4. Kolocouris, N., Zoidis, G., Foscolos, G.B., Fytas, G.,
(10).
Yield 0.29 g (5%), mp 102–104°С. 1H NMR spectrum
(СDCl3), δ, ppm: 1.69–2.20 m (13Н, Ad), 2.38 d (1H,
Ad, J 13.3 Hz), 2.83 br. s (1Н, ОН), 6.39 s (1Н,
СНОН), 7.36–7.48 m (5Н, Ph). 13С NMR spectrum
(СDCl3), δC, ppm: 25.7 and 26.0 (2СН5,7), 32.8 and
33.1 (2СН1,3), 34.1 (CH2), 34.2 (CH2), 34.3 (CH2),
34.5 (CH2), 37.7 (CH2), 91.0 (CHOH), 95.9 (C2),
128.5 (C1Ph), 128.7 (2CHPh), 129.2 (2CHPh), 130.8
(CH4Ph). Found, %: C 70.96; H 7.30; N 4.79.
C17H21NO3. Calculated, %: C 71.06; H 7.37; N 4.87.
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2-(2-Nitrobenzylidene)adamantane (11). Yield
2.58 g (48%), mp 69–70°С. IR spectrum, ν, cm–1: 3067
(СHPh), 2910, 2847 (CHAd), 1651 (CAd=C), 1605
(C=CAr), 1566, 1520 (NO2), 1443, 1358 (NO2), 1323,
1296, 1277, 1099, 1076, 953, 891, 845, 783, 756, 725.
1Н NMR spectrum (CDCl3), δ, ppm: 1.73–2.05 m
(12H, HAd), 2.58 s (1H, HAd), 2.68 s (1H, HAd), 6.40 s
(1H, C=CH), 7.27–7.37 m (2H, H4,6), 7.52 t (1H, Н5,
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11. Klimochkin, Yu.N., Leonova, M.V., and Moiseev, I.K.,
J
= 7.6 Hz), 7.93 d (1Н, Н3, J = 7.6 Hz). Mass
spectrum, m/z (Irel, %): 269 (3) [М]+, 252 (16) [M –
OH]+, 240 (23), 224 (7), 165 (11), 150 (9), 120 (45),
119 (100), 115 (17), 92 (67), 91 (47), 79 (40), 77 (25)
[Ph]+. Found, %: C 75.76; H 7.67; N 5.16. C17H19NO2.
Calculated, %: C 75.81; H 7.11; N 5.20.
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12. Golovin, E.V., Golovina, O.V., Guseva, G.A., Mal’-
kova, N.N., and Klimochkin, Yu.N., Izv. Vuzov, Ser.
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ACKNOWLEDGMENTS
This work was financially supported by the
Ministry of Education and Science of the Russian
Federation in the frame of project part the
governmental task (4.1597.2014/K).
16. Krasnikov, P.E., Osyanin, V.A., and Klimochkin, Yu.N.,
Russ. J. Org. Chem., 2015, vol. 51, no. 5, p. 619. DOI:
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