Reaction of 10,10-dimethyl-9-trimethylsiloxy-9,10-dihydrophenanthrene-9- carbonitrile with acids

Article abstract of DOI:10.1134/S1070428011070141

The behavior of 10,10-dimethyl-9-trimethylsiloxy-9,10-dihydrophenanthrene- 9-carbonitrile in trifluoromethanesulfonic acid and acid systems CF ₃SO₃H-CD₂Cl₂, HSO ₃F-SO₂ClF-CD₂Cl₂, and CF ₃COOH-CD₂Cl₂ were studied by NMR spectroscopy. Principal reaction schemes were determined; the first step in these schemes is protonation of the initial compound at the oxygen or nitrogen atom.

Full text of DOI:10.1134/S1070428011070141

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 7, pp. 1057–1061. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.A. Bushmelev, A.M. Genaev, G.E. Sal’nikov, V.G. Shubin, 2011, published in Zhurnal Organicheskoi Khimii, 2011, Vol. 47,
No. 7, pp. 1040–1044.
Reaction of 10,10-Dimethyl-9-trimethylsiloxy-9,10-dihydro-
phenanthrene-9-carbonitrile with Acids
V. A. Bushmelev, A. M. Genaev, G. E. Sal’nikov, and V. G. Shubin
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: genaev@nioch.nsc.ru
Received November 17, 2010
Abstract—The behavior of 10,10-dimethyl-9-trimethylsiloxy-9,10-dihydrophenanthrene-9-carbonitrile in tri-
fluoromethanesulfonic acid and acid systems CF3SO3H–CD2Cl2, HSO3F–SO2ClF–CD2Cl2, and CF3COOH–
CD2Cl2 were studied by NMR spectroscopy. Principal reaction schemes were determined; the first step in these
schemes is protonation of the initial compound at the oxygen or nitrogen atom.
DOI: 10.1134/S1070428011070141
We found [1] that 10,10-dimethyl-9-trimethyl-
silyloxy-9,10-dihydrophenanthrene-9-carbonitrile (I)
in superacid media undergoes ionization with forma-
tion of long-lived 9-cyano-9,10-dimethylphenanthrenyl
cation (II) (Scheme 1). Apart from signals belonging
to cation II, the NMR spectra contained a number of
additional signals indicating other schemes of reactions
of nitrile I with superacids. The goal of the present
work was to elucidate these schemes.
located in the region δ 7.6–8.9 ppm. In the 13C NMR
spectrum we observed only signals from conformer
IIIa, δC, ppm: 27.1 (9-CH3), 46.1 (C9), 215.7 (C10);
aromatic carbon atoms resonated in the range δC 120–
160 ppm. According to the NMR data, the ratio of
cations II and III was about 1:1.
Scheme 2.
H
Me
Me
Me
Me
O
H
O
Scheme 1.
NC
Me3SiO
Me
Me
Me
Me
NC
H+
–Me3SiOH
IIIa
IIIb
Raising the temperature to –55°C led to coales-
cence of signals of conformers IIIa and IIIb. At
–15°C, the OH signal of cation III became broadened,
presumably as a result of exchange with acid. Analo-
I
NC
Me
Me
9
10
~Me
8
8a
10a
1
1
gous signal was also observed in the H NMR spec-
4a
7
2
trum of a solution of 10,10-dimethyl-9,10-dihydro-
phenanthren-9-one (IV) in CF3SO3H–CD2Cl2 at 10°C
(δ 12.24 ppm).
4b
6
5
4
3
II
1
1
The H NMR spectrum of a solution of nitrile I in
HSO3F–SO2ClF–CD2Cl2 at –105°C displayed signals
obviously belonging to two conformers of 10-hydroxy-
9,9-dimethylphenanthrenyl cation, IIIa and IIIb at
a ratio of 5 : 1 (Scheme 2), δ, ppm: IIIa: 1.90 s
(9-CH3), 12.11 s (OH); IIIb: 1.93 s (9-CH3), 12.62 s
(OH) (cf. [2]). Signals from aromatic protons were
The H and 13C NMR spectra of a solution of I in
HSO3F–SO2ClF–CD2Cl2 also indicated the presence of
an equimolar amount (with respect to cation III) of
hydrogen cyanide and its protonated form which were
rapidly converted into each other (Scheme 3). The
chemical shifts, δ 5.00 and δC 104.5 ppm at –105°C,
were intermediate between those of HCN (δ 3.78,
1057

BUSHMELEV et al.
1058
Scheme 3.
Me
Me
HO
HSO3F
I
II
+
+
HCN
+
Me3SiOSO2F
Me3SiF
III
HCNH+
δC 109.1 ppm in SO2) and its protonated form
[δ 7.50 ppm (CH), δC 97.1 ppm (CH) in HSO3F–SbF5–
SO2] [3]. Sato et al. [4] reported the values δ 4.5 ppm
and δC 106.3 ppm for protonated hydrogen cyanide in
CF3SO3H; the proton signal (δ 5.00 ppm) was dis-
placed upfield by 0.33 ppm upon raising the tempera-
technique (1H–15N HMBC, long-range couplings).
Cross section of the HMBC spectrum at the F2 axis
1
formally corresponds to the H NMR spectrum of V
containing 15N instead of 14N. Multiplet signals of each
NH2+ proton were well resolved in the cross section. In
particular, we clearly observed couplings of nonequiv-
alent protons in the 15NH2+ group with the 15N nucleus
and with each other, and the corresponding coupling
constants were reliably determined by iteration using
NUMMRIT program [7] (Fig. 1). The presence of
a trifluoromethyl group in cation V follows from the
19F NMR spectrum, where the fluorine signal was
displaced by 6.5 ppm downfield relative to the fluorine
signal of trifluoromethanesulfonic acid.
1
ture to –15°C. The H and 13C NMR spectra also
contained signals at δ 0.58 ppm and δC –1.9 ppm, obvi-
ously due to the presence of trimethylsilyl fluorosul-
fonate Me3SiOSO2F, which was converted into Me3SiF
(δ 0.39 ppm, δC –1.5 ppm) at –35°C (cf. [5]).
In the NMR spectra of a solution of nitrile I in tri-
fluoromethanesulfonic acid at 0°C we observed signals
of cation II, while at 25°C those assignable to cation
III, (trifluoromethylsulfonyloxy)methylideneammoni-
um (V) (Fig. 1),* and Me3SiX** (Scheme 4), as well
as poorly resolved signals of unidentified impurities,
were present (cf. [6]). The ratio II–III–V–Me3SiX was
0.48:0.35:0.27:1.*** The intensity of signals belong-
ing to cation II decreased with time, whereas signals
from unidentified impurities proportionally increased
in intensity, and the intensity of signals from cations
III and V did not change. These findings indicate that
cations III and V are not transformation products of
cation II. Cation III was identified by comparing the
Scheme 4.
HA
CF3SO3H
HC
I
II
+
III
+
+ Me3SiX
N
OSO2CF3
HB
V
Unexpectedly, the concentration of cation II in
CF3SO3H depended on the mode of its generation (cf.
[8]). Addition of a solution of I in CD2Cl2 to CF3SO3H
gave a solution containing less than 10% of II (relative
to initial nitrile I), whereas 50% concentration of II
was achieved by addition of solid nitrile I to the acid.
In this case, the presence or absence of CD2Cl2 in the
already prepared solution did not affect the stability of
cation II.
1
above H and 13C NMR spectra with the spectra of
ketone IV in CF3SO3H (cf. [2]), and the structure of V
1
was determined on the basis of H, 13C, 19F, and 15N
NMR data. Signals from the NH2+ group in V in the
1H NMR spectrum are very strongly broadened due to
coupling with quadrupole 14N nucleus, so that their
assignment was difficult. We succeeded in identifying
Our experimental data on transformations of nitrile
I in superacids may be rationalized assuming two con-
current processes where the initial step is protonation
of nitrile I at the oxygen or nitrogen atom (Scheme 5).
The possibility for the formation of cation V from
hydrogen cyanide according to Scheme 5 was con-
firmed by special experiment: cation V was formed
upon dissolution of potassium cyanide in trifluoro-
methanesulfonic acid (Scheme 6). At room tempera-
ture cation V was slowly converted into a species
which was identified as hydroxymethylideneammo-
1
these signals by two-dimensional H–15N correlation
*** According to Sato et al. [4], this compound was slowly
formed by reaction of protonated hydrogen cyanide in
CF3SO3H at 20°C; however, no spectral data were given.
*** Presumably, X = OSO2CF3, for compound I in other acids
(HSO3F and CF3COOH) gives rise to the corresponding tri-
methylsilyl esters.
*** According to Scheme 4, the ratio III/V should be equal to
1:1. Presumably, the concentration of cation V is underesti-
mated due to volatility of its precursor, hydrogen cyanide
(Scheme 5). Analogous pattern was observed for a solution in
CF3COOH.
1
nium (VI) on the basis of the H NMR data. Its struc-
ture was also confirmed by generation from formamide
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

REACTION OF 10,10-DIMETHYL-9-TRIMETHYLSILOXY-9,10-DIHYDRO...
1059
Scheme 5.
Me3Si
NC
Me
Me
Me
Me
NC
O
~Me
H
II
–Me3SiOH
H+
I-OH
I
HN
Me3SiO
Me
Me
Me
Me
Me3SiO
V
+
C
NH
H+
OSO2CF3
H
CF3SO3H
I-NH
HC≡N
HN
III
as a result of protonation in CF3SO3H–CD2Cl2
(Scheme 7, Fig. 2).
based analysis (e.g., like NUMMRIT program). We did
not observe coupling with 14N in the spectra recorded
in the present work, presumably due to the presence of
water in formamide.
Scheme 6.
H+
CF3SO3H
OSO2CF3
The reaction of nitrile I with trifluoroacetic acid at
room temperature gave rise to a mixture containing
ketone IV and cation III (protonation product of IV),
as well as HCN and Me3SiOCOCF3, at a ratio of
1.0:0.6:1 (Scheme 8). The components were identified
by comparing the NMR spectrum of the mixture with
those of ketone IV and Me3SiCN in CF3COOH (by
special experiment we showed that trimethylsilyl cya-
nide in trifluoroacetic acid is completely converted
into HCN and Me3SiOCOCF3; cf. [4])
KCN
HCN
HN
OH
H
H+
HB
V
N
HA
HC
VI
Scheme 7.
O
O
H+
VI
H2N
H
H2N
H
EXPERIMENTAL
1
The H and 13C NMR spectra were recorded on
Gillespie and Birchal [9] reported an invalid value
for the vicinal trans-H–N=C–H coupling constant in
VI (8.5 Hz); in fact, it is considerably larger (14.4 Hz).
Obviously, the reason is that coupling with 14N was
Bruker AV-300 (300.13 and 75.47 MHz, respectively),
AV-400 (400.13 and 100.61 MHz), and AV-600 instru-
ments (600.30 and 150.95 MHz). The H and 13C
1
1
observed by the authors [9] in the H NMR spectrum
chemical shifts were measured relative to the solvent
signals (CD2Cl2 for cations, δ 5.33, δC 53.3 ppm;
CDCl3 for neutral compounds, δ 7.24, δC 76.9 ppm).
The 19F chemical shifts were measured relative to
CF3SO3H or CF3COOH as internal reference and were
recalculated to CFCl3 (external reference). The
15N NMR spectra were recorded using NH3 as external
reference. The temperature in the NMR probes was
calibrated against melting point of pentane (–130°C)
and using standard methanol sample (above –90°C);
linear interpolation was applied for intermediate tem-
peratures. Signals in the NMR spectra were assigned
using two-dimensional 1H–1H correlations with double
of VI recorded at 60 MHz, i.e., the spectrum was of
second order, and it was impossible to reliably deter-
mine JHH values without resorting to special computer-
Scheme 8.
CF3COOH
I
HCN
+
Me3SiOCOCF3
Me
Me
O
III
+
IV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

BUSHMELEV et al.
1060
(c)
product (from Aldrich); trifluoroacetic acid of pure
grade was distilled (bp 72–73°C).
The structure of cationic species was optimized at
the DFT level of theory using PBE functional [12]
{PRIRODA program [13], L1 basis set (Λ01 [14],
an analog of cc-pVDZ)}. Visualizations and Cartesian
coordinates are available at http://limor1.nioch.nsc.ru/
quant/phen-CN/. xsim software package [ftp://
nmr.nioch.nsc.ru/pub/nmr/] was used as interface for
NUMMRIT. The coupling constants for cation VI
were calculated using second-order polarization propa-
gator approximation (SOPPA) (DALTON program
[15], cc-pCsVDZ basis set for C and N atoms, aug-cc-
PVTZ-J for HA–HC, and cc-pVDZ for OH).
Preparation of acid solutions. Nitrile I or ketone
IV, 30–40 mg (either as solid substance or as a solu-
tion in 0.1 ml of CD2Cl2), was added to the correspond-
ing superacid system or pure acid placed into an NMR
ampule or a reaction flask. The mixture was stirred
with a glass rod cooled with liquid nitrogen (in low-
temperature experiments) or on a magnetic stirrer (in
a flask at 0°C or room temperature when CF3COOH
was used as acid) until it became homogeneous. Solu-
tions prepared in a flask were transferred into an NMR
ampule at room temperature.
(b)
(a)
10.5
10.0
9.5
δ, ppm
1
Fig. 1. H NMR spectra (600 MHz) of cation V: (a) routine
spectrum, (b) cross section at the F2 axis of the two-dimen-
sional H–15N HMBC spectrum, and (c) calculated spectrum
1
(NUMMRIT).
1H
1H {14N}
8.7
8.6
8.5
δ, ppm
9-Hydroxy-10,10-dimethyl-9,10-dihydrophenan-
thren-9-ylium (III). H NMR spectrum (600.3 MHz,
13C
1
CF3SO3H–CD2Cl2, 4:1, 25°C), δ, ppm: 2.00 (CH3),
7.73 (6-H), 7.83 (7-H), 7.856 (8-H), 7.858 (2-H), 8.44
(3-H), 8.48 (5-H), 8.63 (4-H), 8.64 (1-H); cf. [2].
13C NMR spectrum (150.95 MHz), δC, ppm: 28.8
(CH3), 47.8 (C9), 121.8 (C10a), 126.3 (C4), 126.4
(C4b, C5), 127.3 (C8), 129.8 (C6), 131.0 (C2), 132.5
(C1), 133.8 (C7), 142.6 (C8a), 148.2 (C3), 149.0 (C4a),
216.9 (C10).
171
170
δC, ppm
15N
133
132
131
δN, ppm
1
1
Fig. 2. H and H{14N} (600 MHz), 13C (100.6 MHz), and
9,9-Dimethyl-9,10-dihydrophenanthren-9-one
15N (60.8 MHz, INEPT) NMR spectra of cation VI.
1
(IV) in CF3COOH–CD2Cl2 (4:1). H NMR spectrum
(300 MHz, 25°C), δ, ppm: 1.68 s (6H), 7.44–7.58 m
(3H), 7.65 d (1H, J = 8 Hz), 7.85 t (1H, J = 8 Hz),
8.11–8.22 m (3H). 13C NMR spectrum (75 MHz), δC,
ppm: 27.6 q, 48.9 s, 124.2 d, 125.0 d, 127.1 d, 128.3 d,
128.8 s, 129.0 d, 129.2 d, 129.4 s, 130.6 d, 137.1 d,
139.7 s, 143.9 s, 211.9 s.
quantum filtering (COSYDQF) and 13C–1H and 15N–
1H correlations for direct (HSQC) and long-range cou-
plings (HMBC).
The synthesis of 10,10-dimethyl-9-trimethylsiloxy-
9,10-dihydrophenanthrene-9-carbonitrile (I) was de-
scribed in [1]. Ketone IV was prepared as reported in
[10]. Commercial trimethylsilyl cyanide (purity 97%,
from Fluka, or 98%, from Acros Organics) and form-
amide of pure grade were used; fluorosulfonic acid
was distilled twice (bp 158–161°C); SO2ClF [11] was
dried by passing its vapor through concentrated sul-
furic acid; CD2Cl2 was dried over 4-Å molecular
sieves; trifluoromethanesulfonic acid was commercial
1
Nitrile I in CF3COOH–CD2Cl2 (4:1). The H and
13C NMR spectra were identical to the corresponding
spectra of a solution of ketone IV in CF3COOH–
CD2Cl2 (4 :1) with the difference that signals from
HCN {δ 4.32, δC 108.0 ppm (1JCH = 273 Hz); cf.
[3, 16, 4]} and Me3SiOCOCF3 {[δ 0.53, cf. [17];
δC –1.4 (SiMe3), 115.5 (CF3, 1JCF = 285 Hz), 160.2 ppm
2
(C=O, JCF = 43 Hz), cf. [4]} were present. 19F NMR
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

REACTION OF 10,10-DIMETHYL-9-TRIMETHYLSILOXY-9,10-DIHYDRO...
1061
spectrum (282.4 MHz, CF3COOH as reference,
δF –76.0 ppm): δF –76.5 ppm.
no. 09-03-00116-a) and by the Chemistry and Mate-
rials Science Department of the Russian Academy of
Sciences (proiect no. 5.1.4).
[(Trifluoromethylsulfonyloxy)methylidene]am-
1
monium (V). H NMR spectrum (600 MHz,
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(HB), 10.37 (HC); JAB = 14.2, JAC = 5.4, JA,N = 4.5,
JBC = 2.7, JB,N = 94.0, JC,N = 97.0 Hz (absolute values
of coupling constants are given). 13C NMR spectrum
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1
227.4, JCH ≈ 6, JCF = 322.7 Hz. 19F NMR spectrum
(564.8 MHz, CF3SO3H, δF –77.5 ppm): δF –71.0 ppm.
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1
solution were recorded at 32°C. H NMR spectrum
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JAB = 14.4, JAC = 4.6, JBC ≈ 0 Hz. 13C NMR spectrum
1
(151 MHz), δC, ppm: 170.3 (C=N); JCH = 213.5,
2
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This study was performed under financial support
by the Russian Foundation for Basic Research (project
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011