Synthesis of 1′-substituted 4′,4′-dimethyl-6′- methoxy-4′H-spiro[cyclohexane-1,3′-isoquinolines]

Article abstract of DOI:10.1134/S1070428014040125

The reaction of 1-(4-methoxyphenyl)-1-(1-methylcyclohexyl)ethanol with nitriles in concentrated sulfuric acid afforded 1′-substituted 6′-methoxy-4′,4′-dimethyl-4′H-spiro[cyclohexane-1, 3′-isoquinolines] as a result of consecutive Wagner-Meerwein rearrangement and Ritter reaction.

Full text of DOI:10.1134/S1070428014040125

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 4, pp. 513–517. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © A.N. Perevoshchikova, A.A. Gorbunov, Yu.S. Rozhkova, P.A. Slepukhin, Yu.V. Shklyaev, 2014, published in Zhurnal Organicheskoi
Khimii, 2014, Vol. 50, No. 4, pp. 525–528.
Synthesis of 1′-Substituted 4′,4′-Dimethyl-6′-methoxy-
4′H-spiro[cyclohexane-1,3′-isoquinolines]
A. N. Perevoshchikovaa, A. A. Gorbunova, Yu. S. Rozhkovaa,
P. A. Slepukhinb, and Yu. V. Shklyaeva
a Institute of Technical Chemistry, Ural Branch, Russian Academy of Sciences,
ul. Akad. Koroleva 3, Perm, 614013 Russia
e-mail: AnnPer87@gmail.com
b Postovskii Institute of Organic Synthesis, Ural Branch, Russian Academy of Sciences,
ul. S. Kovalevskoi/Akademicheskaya 22/20, Yekaterinburg, 620990 Russia
Received February 3, 2014
Abstract—The reaction of 1-(4-methoxyphenyl)-1-(1-methylcyclohexyl)ethanol with nitriles in concentrated
sulfuric acid afforded 1′-substituted 6′-methoxy-4′,4′-dimethyl-4′H-spiro[cyclohexane-1,3′-isoquinolines] as
a result of consecutive Wagner–Meerwein rearrangement and Ritter reaction.
DOI: 10.1134/S1070428014040125
Wagner–Meerwein rearrangement is a cationic re-
arrangement typical of systems possessing several
geminal alkyl substituents. It is used in the synthesis
and transformations of carbocyclic compounds [1–4].
Wagner–Meerwein rearrangement can be accompanied
by Ritter reaction since intermediate carbocation is
capable of reacting with nitriles. For example, we
previously showed that 3,3-dimethyl-2-phenylbutan-2-
ol in the presence of nitriles under acidic conditions
can be converted into 1-substituted 3,3,4,4-tetra-
methyl-3,4-dihydroisoquinoline derivatives as a result
of successive Wagner–Meerwein rearrangement and
Ritter reaction [5].
If a tertiary alcohol contains a carbocyclic frag-
ment, its Wagner–Meerwein rearrangement may be
accompanied by expansion of the aliphatic ring [6, 7].
With a view to explore the behavior of carbinols of the
1-(1-methylcycloalkyl)-1-phenylethanol series under
the Ritter reaction conditions, 1-(4-methoxyphenyl)-1-
(1-methylcyclohexyl)ethanol (I) was brought into reac-
tion with nitriles IIa–IIe in concentrated sulfuric acid.
It was expected that compound I will undergo rear-
rangement involving both migration of methyl group
with formation of a spiro isoquinoline system and
expansion of the six-membered ring to produce
previously unknown homophenanthridine derivatives.
Scheme 1.
Me
N
Me
Me
Me
MeO
MeO
NH
CHCOOEt
Me
OH
RCN (IIa–IIe)
R
H2SO4
IIIa–IIId
IIIe
Me
MeO
I
Me
MeO
Me
N
R
R = Me (a), MeS (b), Ph (c), 4-O2NC6H4 (d), EtOC(O)CH2 (e).
513

PEREVOSHCHIKOVA et al.
and IIIe or at δ 7.07–7.18 ppm (3J = 8.4 Hz) in the
514
C2
spectra of isoquinolines IIIc and IIId having an aro-
matic substituent on C1. In the latter case, the upfield
position of the 8′-H signal is determined by shielding
effect of the aromatic substituent.
C14
C4
O3
C17
O2
Isoquinoline IIIe has enamine structure, as follows
from the presence in its 1H NMR spectrum of a singlet
at δ 5.03 ppm from the vinylic proton and a broadened
singlet at δ 9.34 ppm from the NH proton. In the IR
spectrum of IIIe we observed an absorption band at
3269 cm–1, typical of NH stretching vibrations. During
GC/MS analysis compound IIIe underwent thermal
decomposition, and only the peak corresponding to
1′-methyl derivative IIIa was detected [8]. The struc-
ture of isoquinoline IIIe was unambiguously deter-
mined by X-ray analysis (see figure).
C21
C7
C3
N1
C20
C11
C5
C18
C8
C15
C13
C10
C12
C16
C9
C19
O1
C6
C1
According to the X-diffraction data, compound IIIe
crystallizes in a non-centrosymmetric space group. The
bond lengths and bond angles in molecule IIIe do not
differ from the expected values. In particular, conjuga-
tion with the ester group leads to leveling of bonds at
the C7 and C3 atoms. The difference between the
formally double and formally single bonds in that frag-
ment does not exceed 0.05 Å. The spiro-fused cyclo-
hexane fragment adopts a chair conformation, and
the dihydropyridine ring has sofa structure. No any
specific intermolecular interactions were detected in
the crystal packing of compound IIIe.
Structure of the molecule of ethyl 2-[6′-methoxy-4′,4′-di-
methyl-2′H-spiro[cyclohexane-1,3′-isoquinolin]-1′(4′H)-yli-
dene}acetate (IIIe) according to the X-ray diffraction data.
In fact, we isolated for the first time 1-substituted
6′-methoxy-4′,4′-dimethyl-4′H-spiro[cyclohexane-1,3′-
isoquinolines] IIIa–IIIe in 66–84% yield (Scheme 1).
The structure of compounds IIIa–IIIe was proved
by their IR, H and 13C NMR, and mass spectra and
1
1
elemental analyses. The H NMR spectra of IIIa–IIIe
contained a three-proton singlet in the region δ 3.82–
3.86 ppm due to the 6′-methoxy group. The 5′-H signal
appeared as a doublet at δ 6.85–6.95 ppm (4J = 2.4–
2.7 Hz). A doublet of doublets at δ 6.66–6.73 ppm
A probable mechanism of the described reaction in-
cludes Wagner–Meerwein rearrangement with forma-
tion of carbocation B which takes up nitrile molecule
to give nitrilium ion C. Intramolecular cyclization of
the latter at the ipso position yields spiro σ-complex D,
and 1,2-migration of the C4–C5 bond in intermediate D
leads to the final product (Scheme 2).
4
(3J = 8.4–8.7, J = 2.4–2.7 Hz) was assigned to 7′-H.
The 8′-H proton resonated as a doublet at δ 7.39–
7.59 ppm (3J = 8.4–8.7 Hz) in the spectra of IIIa, IIIb,
Scheme 2.
Me
Me
Me
Me
Me
N
H+
I
–H2O
Me
··
RCN
MeO
MeO
MeO
R
A
B
C
Me
H
Me
Me
MeO
4
Me
3
III
N2
–H+
6
7
N
5
1
10
8
R
R
MeO
9
D
E
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

SYNTHESIS OF 1′-SUBSTITUTED 4′,4′-DIMETHYL-6′-METHOXY-4′H-SPIRO...
515
EXPERIMENTAL
the Cambridge Crystallographic Data Centre (entry
no. CCDC 983915).
1
13
The H and C (DEPT) NMR spectra were record-
ed from solutions in CDCl3 on a Varian Mercury Plus
300 spectrometer at 300.06 and 75.46 MHz, respec-
tively, using hexamethyldisiloxane as internal refer-
ence. The IR spectra were measured on a Bruker IFS-
66/S spectrometer from thin films. The mass spectra
were obtained on an Agilent Technologies 6890N–
5975B GC/MS system (HP-5ms column, 30 m×
0.25 mm, film thickness 0.25 μm; carrier gas helium,
flow rate 1 mL/min; electron impact, 70 eV). The
elemental compositions were determined on a Leco
CHNS-932 analyzer. The progress of the reactions and
the purity of products were monitored by TLC on
Sorbfil plates; spots were developed by treatment with
a 0.5% solution of chloranil in toluene or under UV
light. Silica gel (70–230 mesh, Lancaster) was used for
column chromatography. The melting points were
measured on a PTP melting point apparatus.
(4-Methoxyphenyl)(1-methylcyclohexyl)metha-
none was synthesized according to the procedure de-
scribed in [10] from 8.03 g (50 mmol) of 1-methyl-
cyclohexane-1-carbonyl chloride and 15.36 g
(142 mmol) of anisole in the presence of 6.67 g
(50 mmol) of AlCl3. Yield 7.93 g (68%), colorless
liquid, bp 175–178°C (6.5 mm); published data [10]:
mp 172–172.5°C (5 mm). IR spectrum, ν, cm–1: 1665,
1
1609. H NMR spectrum, δ, ppm: 1.10–1.70 m (13H,
Me, CH2), 3.83 s (3H, OMe), 6.87 d.d (2H, 3-H, 5-H,
3J = 6.9, 4J = 1.8 Hz), 7.77 d.d (2H, 2-H, 6-H, 3J = 6.9,
4J = 2.4 Hz). Mass spectrum, m/z (Irel, %): 232 [M]+
(6.3), 136 [M – C7H13 + H]+ (12.3), 135 [M – C7H13]+
(100), 77 [C6H5]+ (11.5), 55 [C4H7]+ (12.4). Found, %:
C 77.72; H 8.45. C15H20O2. Calculated, %: C 77.55;
H 8.68. M 232.32.
1-(4-Methoxyphenyl)(1-methylcyclohexyl)etha-
nol (I). A solution of 7.93 g (34 mmol) of (4-me-
thoxyphenyl)(1-methylcyclohexyl)methanone in
10 mL of diethyl ether was added dropwise under
stirring to a freshly prepared solution of methylmagne-
sium iodide {from 1.03 g (42 mmol) of magnesium
turnings and 6.03 g (42 mmol) of methyl iodide in
20 mL of diethyl ether [11]} so that to maintain the
mixture slightly boiling. The mixture was then heated
for 2 h under reflux and hydrolyzed by slowly adding
a mixture of 35 mL of a saturated solution of ammo-
nium chloride and 15 mL of crushed ice. The organic
phase was separated, the aqueous phase was extracted
with diethyl ether (3×15 mL), the extracts were com-
bined with the organic phase, dried over MgSO4, and
evaporated, and the residue was crystallized from hex-
ane. Yield 6.91 g (82%), colorless crystals, mp 70°C.
IR spectrum, ν, cm–1: 3452, 2929, 2858, 1607, 1509.
1H NMR spectrum (DMSO-d6), δ, ppm: 0.82 s (3H,
CH3COH), 0.88–1.70 m (13H, 1-Me, CH2), 3.76 s
Commercially available reagents and solvents (Alfa
Aesar, Sigma–Aldrich, Reakhim) were used.
The X-ray diffraction data were obtained at
295(2) K from a 0.25×0.20×0.15-mm fragment of
a colorless prismatic single crystal of IIIe on
an Xcalibur-3 automatic diffractometer with a CCD
detector (Oxford Diffraction). The data were acquired
according to standard procedure [ω-scanning through
a step of 1°, λ = 0.71073 Å (MoKα)]. Rhombic crystal
system, space group Pca21; unit cell parameters: a =
12.5844(13), b = 9.2785(8), c = 16.3834(10) Å; V =
1913.0(3) Å3; Z = 4; dcalc = 1.189 g/cm3. Total of
5746 reflection intensities were collected, 1995 of
which were independent (Rint = 0.0291), and 1131 re-
flections were characterized by I > 2σ(I); completeness
98% in the range 2.73 < Θ < 26.38. The structure was
solved by the direct method and was refined against F2
in anisotropic approximation for non-hydrogen atoms
using SHELXTL software package [9]. The positions
of hydrogen atoms were refined according to the riding
model in isotropic approximation with dependent
thermal parameters. No correction for absorption was
applied because of its insignificance (μ = 0.079 mm–1);
the absolute structural parameter was not estimated.
The final divergence factors were R1 = 0.0305, wR2 =
0.0562 for reflections with I > 2σ(I) and R1 = 0.0624,
wR2 = 0.0591 for all reflections; goodness of fit S =
1.003; maximum and minimum residual electron
density peaks 0.095 and –0.123 ē/Å3. The crystallo-
graphic data for compound IIIe were deposited to
3
(3H, OMe), 4.60 s (1H, OH), 6.85 d (2H, m-H, J =
9.0 Hz), 7.33 d (2H, o-H, 3J = 8.7 Hz). 13C NMR spec-
trum, δC, ppm: 17.49 (1-Me); 22.02, 22.12, 26.00,
31.07, 31.12 (CH2); 24.70 (CH3COH), 40.28 (C1),
55.10 (OMe), 78.93 (COH), 112.17 (Cm), 128.47 (Co),
138.20 (Ci), 157.91 (Cp). Mass spectrum, m/z (Irel, %):
248 (0.01) [M]+, 230 (2.9) [M – H2O]+, 215 (3.9)
[M – H2O – CH3]+, 151 (100) [M – C7H13]+, 43 (31.3).
Found, %: C 77.10; H 9.69. C16H24O2. Calculated, %:
C 77.38; H 9.74. M 248.36.
Compounds IIIa–IIIe (general procedure). A mix-
ture of 1 mmol of alcohol I and 1 mmol of nitrile IIa–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

PEREVOSHCHIKOVA et al.
516
13
IIe was added dropwise under vigorous stirring to
1 mL of 92% H2SO4 on cooling with ice water. The
mixture was then stirred for 30 min at room tempera-
ture, poured into a mixture of crushed ice and 4 mL of
aqueous ammonia, and extracted with methylene chlo-
ride (3×5 mL). The combined extracts were washed
with water, dried over MgSO4, and evaporated, and the
product was isolated by column chromatography (IIIc)
or recrystallization (IIIa, IIIb, IIId, IIIe).
C6H5). C NMR spectrum, δC, ppm: 22.61 and 22.65
(4′-Me); 26.46, 29.66, 30.42 (CH2); 39.10 (C4′), 55.19
(MeO), 60.32 (C3′), 109.09 and 110.97 (C5′, C7′),
121.02 (C8a′); 128.03, 128.13, 128.98, 129.10, 129.62,
131.09 (C8′, Co, Cm, Cp); 140.07 and 150.26 (C1′, Ci),
161.68 and 163.36 (C4a′, C6′). Mass spectrum, m/z
(Irel, %): 333 [M]+ (100), 318 [M – CH3]+ (66.4), 290
(12.1), 262 (10.0), 251 (18.6), 250 (25.7), 237 (88.8),
236 (68.8), 222 (15.4), 221 (29.2), 178 (19.3). Found,
%: C 82.94; H 8.08; N 4.35. C23H27NO. Calculated, %:
C 82.84; H 8.16; N 4.20. M 333.47.
6′-Methoxy-1′,4′,4′-trimethyl-4′H-spiro[cyclo-
hexane-1,3′-isoquinoline] (IIIa). Yield 0.23 g (84%),
mp 73–74°C (from acetone). IR spectrum, ν, cm–1:
6′-Methoxy-4′,4′-dimethyl-1′-(4-nitrophenyl)-
4′H-spiro[cyclohexane-1,3′-isoquinoline] (IIId).
Yield 0.30 g (79%), mp 135–136°C (from acetone).
IR spectrum, ν, cm–1: 2935, 2854, 1603, 1569, 1520.
1H NMR spectrum, δ, ppm: 0.80–1.80 m (16H, CH2,
4′-Me), 3.86 s (3H, OMe), 6.68 d.d (1H, 7′-H, 3J = 8.4,
1
2958, 2915, 2854, 1614, 1576. H NMR spectrum, δ,
ppm: 0.60–2.10 m (16H, CH2, 4′-Me), 2.37 s (3H,
1′-Me), 3.83 s (3H, OMe), 6.71 d.d (1H, 7′-H, 3J = 8.7,
4
4J = 2.4 Hz), 6.85 d (1H, 5′-H, J = 2.4 Hz), 7.39 d
3
13
(1H, 8′-H, J = 8.4 Hz). C NMR spectrum, δC, ppm:
22.13 (1′-Me, 4′-Me), 26.18 and 30.35 (CH2), 39.85
(C4′), 55.15 (MeO), 61.58 (C3′), 109.49 and 110.73
(C5′, C7′), 121.15 (C8a′), 126.18 (C8′), 148.74 (C4a′),
160.64 and 161.76 (C1′, C6′). Mass spectrum, m/z
(Irel, %): 271 (88.3) [M]+, 256 (100) [M – CH3]+, 228
(34.4) [M – C3H7]+, 189 (88.8) [M – CH3CN – C3H5]+,
174 (77.4) [M – CH3CN – C4H8]+. Found, %: C 79.54;
H 9.08; N 5.35. C18H25NO. Calculated, %: C 79.66;
H 9.28; N 5.16. M 271.40.
4J = 2.4 Hz), 6.95 d (1H, 5′-H, J = 2.7 Hz), 7.07 d
4
(1H, 8′-H, 3J = 8.4 Hz), 7.80 d (2H, o-H, 3J = 8.7 Hz),
8.27 d (2H, m-H, 3J = 8.7 Hz). 13C NMR spectrum, δC,
ppm: 22.51 and 22.54 (4′-Me), 26.32 and 30.32 (CH2),
39.20 (C4′), 55.33 (MeO), 61.13 (C3′), 109.45 and
111.43 (C5′, C7′), 120.18 (C8′a), 123.42 (Co), 129.03 and
130.01 (C8′, Cm); 146.23, 148.25, 150.29 (C1′, Ci, Cp);
161.89 and 162.20 (C4′a, C6′). Mass spectrum, m/z
(Irel, %): 378 [M]+ (84.2), 377 [M – H]+ (40.6), 363
[M – CH3]+ (48.4), 296 [M – C6H10]+ (16.9), 295 [M –
C6H11]+ (18.4), 282 (100), 281 (81.6), 266 (20.9), 236
(9.7), 235 (9.3), 220 (8.6), 219 (9.6), 191 (12.4), 189
(11.5), 178 (10.9), 165 (9.2), 98 (23.0), 41 (18.4).
Found, %: C 72.85; H 6.89; N 7.31. C23H26N2O3. Cal-
culated, %: C 72.99; H 6.92; N 7.40. M 378.46.
6′-Methoxy-4′,4′-dimethyl-1′-methylsulfanyl-
4′H-spiro[cyclohexane-1,3′-isoquinoline] (IIIb).
Yield 0.20 g (66%), mp 131–132°C (from hexane).
IR spectrum, ν, cm–1: 2956, 2937, 2857, 1605, 1557.
1H NMR spectrum, δ, ppm: 1.00–2.00 m (16H, CH2,
4′-Me), 2.45 s (3H, SMe), 3.82 s (3H, OMe), 6.70 d.d
(1H, 7′-H, 3J = 8.4, 4J = 2.4 Hz), 6.85 d (1H, 5′-H, 4J =
Ethyl 2-[6′-methoxy-4′,4′-dimethyl-2′H-spiro-
[cyclohexane-1,3′-isoquinolin]-1′(4′H)-ylidene}-
acetate (IIIe). Yield 0.29 g (77%), mp 97–98°C (from
acetone). IR spectrum, ν, cm–1: 3269, 2982, 2848,
1701, 1637, 1591. H NMR spectrum, δ, ppm: 0.70–
2.00 m [19H, OCH2Me, (CH2)5, 4′-Me], 3.83 s (3H,
3
2.7 Hz), 7.57 d (1H, 8′-H, J = 8.4 Hz). 13C NMR
spectrum, δC, ppm: 12.40 (SMe), 22.10 (4′-Me), 26.38
and 30.99 (CH2), 39.51 (C4′), 55.25 (MeO), 61.88 (C3′),
109.52 and 110.93 (C5′, C7′), 121.31 (C8′a), 126.21
(C8′), 148.47 (C4′a), 157.60 and 161.86 (C1′, C6′). Mass
spectrum, m/z (Irel, %): 303 [M]+ (6.1), 288 [M – CH3]+
(100), 191 (3.9), 159 (4.0), 115 (3.3), 41 (3.4). Found,
%: C 71.54; H 8.08; N 4.85; S 10.36. C18H25NOS.
Calculated, %: C 71.24; H 8.30; N 4.62; S 10.57.
M 303.46.
1
3
OMe), 4.17 q (2H, OCH2, J = 7.2 Hz), 5.03 s (1H,
C1′=CH), 6.73 d.d (1H, 7′-H, J = 8.7, J = 2.4 Hz),
3
4
4
3
6.87 d (1H, 5′-H, J = 2.7 Hz), 7.59 d (1H, 8′-H, J =
8.7 Hz), 9.34 br.s (1H, NH). 13C NMR spectrum, δC,
ppm: 14.73 (OCH2Me), 21.65 and 25.48 [(CH2)5],
29.53 (4′-Me), 40.95 (C4′), 55.20 (MeO), 55.99 (C3′),
58.30 (OCH2), 75.64 (C1′=CH), 110.43 and 111.10
(C5′, C7′), 120.80 (C8a′), 126.87 (C8′), 147.57 (C4a′),
154.96 and 161.88 (C1′, C6′), 171.41 (C=O). Found, %:
C 73.62; H 8.48; N 4.23. C21H29NO3. Calculated, %:
C 73.44; H 8.51; N 4.08. M 343.46.
6′-Methoxy-4′,4′-dimethyl-1′-phenyl-4′H-spiro-
[cyclohexane-1,3′-isoquinoline] (IIIc). Yield 0.26 g
(78%), yellow oily substance (eluent hexane–ethyl
acetate, 15:1). IR spectrum, ν, cm–1: 2943, 2854, 1607,
1
1566. H NMR spectrum, δ, ppm: 0.70–2.50 m (16H,
CH2, 4′-Me), 3.84 s (3H, OMe), 6.66 d.d (1H, 7′-H,
4
3J = 8.4, 4J = 2.7 Hz), 6.93 d (1H, 5′-H, J = 2.7 Hz),
This study was performed under financial support
by the Presidium of the Russian Academy of Sciences
3
7.18 d (1H, 8′-H, J = 8.4 Hz), 7.30–7.70 m (5H,
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SYNTHESIS OF 1′-SUBSTITUTED 4′,4′-DIMETHYL-6′-METHOXY-4′H-SPIRO...
517
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