Alkylation of 2,4-dimethylphenol with (+)-α- and (-)-β-pinenes in the presence of aluminum xylenolate

Article abstract of DOI:10.1134/S1070428014040241

Alkylation of 2,4-dimethylphenol with (+)-α- and (-)-β-pinenes in the presence of aluminum 2,4-dimethylphenoxide generated in situ led to the formation of mixtures of products, from which optically active compounds were isolated. The structure of 2-bornyl

Full text of DOI:10.1134/S1070428014040241

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 4, pp. 589–595. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © I.Yu. Chukicheva, M.V. Krylova, E.V. Buravlev, K.Yu. Suponitskii, A.V. Kutchin, 2014, published in Zhurnal Organicheskoi Khimii,
2014, Vol. 50, No. 4, pp. 600–606.
Alkylation of 2,4-Dimethylphenol with (+)-α- and (–)-β-Pinenes
in the Presence of Aluminum Xylenolate
I. Yu. Chukichevaa, M. V. Krylovaa, E. V. Buravleva, K. Yu. Suponitskiib, and A. V. Kutchina
a Institute of Chemistry, Komi Research Center, Ural Branch, Russian Academy of Sciences,
ul. Pervomaiskaya 48, Syktyvkar, 167982 Russia
e-mail: chukicheva-iy@chemi.komisc.ru
b Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
Received January 27, 2014
Abstract—Alkylation of 2,4-dimethylphenol with (+)-α- and (–)-β-pinenes in the presence of aluminum
2,4-dimethylphenoxide generated in situ led to the formation of mixtures of products, from which optically
active compounds were isolated. The structure of 2-bornyl-4,6-dimethylphenol was determined by X-ray
analysis; its (+)- and (–)-enantiomers were assigned (1R,2R,4S) and (1S,2S,4R) configurations, respectively.
DOI: 10.1134/S1070428014040241
Phenols and cresols with an isobornyl substituents
exhibit biological activity, in particular antioxidant,
hemorheological, membrane-protecting, and anti-in-
flammatory [1–4]. In some Western Europe countries
the liquid spray formulation Bornilene (Abiogen
Pharma) containing 2-isobornyl-4,5-dimethylphenol
(Xibornol) as active component is used for the treat-
ment of throat diseases [5]. The problem of obtaining
enantiomerically enriched and enantiomerically pure
compounds remains topical since different enantiomers
may show different biological effects [6].
We previously reported on the alkylation of phenol
with excess α- or β-pinene, which led to the formation
of optically active C- and O-bornyl derivatives [7, 8].
Scheme 1.
R
11
16
(+)-α-Pinene or (–)-β-pinene
(2,4-Me2C6H3O)3Al
OH
OR
Me
OH
Me
11
12
15
14
+
13
15
Me
Me
Me
Me
13
I
IIa–IIc
IIIa, IIIb
Me
O
Me
14 Me
Me
CH2
8
1
4
O
CH2
9
5
7
3
+
+
+
Me
Me
10
Me
6
15
+
17
Me
Me
Me
16
11
13 Me
12
Me
Me
Me
IV
V
VI
VII
Me
Me
Me
Me
7
4
10
Me
Me
Me
H
Me
2
6
R =
(a),
(b),
(c).
1
H
H
Me
5
3
589

CHUKICHEVA et al.
590
Alkylation of 2,4-dimethylphenol with (+)-α-pinene and (–)-β-pinene
Product composition, %
Terpene
IIa
IIb, IIc
IIIa
IIIb
IV
V
VI
VII
(+)-α-Pinene
(–)-β-Pinene
28
26
3
2
23
22
6
6
03
17
2
7
22
11
13
09
In the present work we extended this reaction to other
phenolic compounds and studied the alkylation of
2,4-dimethylphenol (I) with (+)-α-pinene and (–)-β-pi-
nene (Scheme 1).
an overall yield 35%. Compounds VI and VII are
likely to be formed via rearrangement and opening of
the four-membered pinene ring at fairly high tempera-
ture in the presence of Lewis acid [7, 9, 10]. The al-
kylation of xylenol I with (–)-β-pinene gave an analo-
gous set of products, but the yield of chroman deriva-
tives IV and V was higher, and of terpenes VI and VII,
lower (see table); furthermore, unlike the reaction with
(+)-α-pinene, 2,4-dimethylphenyl bornyl ether (–)-IIa
and 2-bornyl-4,6-dimethylphenol (+)-IIIa had the op-
posite configuration.
The reactions were carried out by heating the reac-
tants for 7 h at 200°C using 2 equiv of the terpene
component and aluminum 2,4-dimethylphenoxide gen-
erated in situ as catalyst. The reaction of 2,4-dimethyl-
phenol (I) with (+)-α-pinene afforded mainly O-alkyla-
tion products, 28% of 2,4-dimethylphenyl bornyl ether
(+)-IIa and a small amount of an inseparable mixture
of isobornyl and fenchyl ethers IIb and IIc, and
C-alkylation products (–)-IIIa and IIIb with bornyl
and isobornyl substituents (see table). In addition,
a small amount of chroman derivatives IV and V,
camphene (VI), and limonene (VII) were isolated in
The structure of the isolated compounds was deter-
mined by NMR spectroscopy. Because of similar chro-
matographic mobilities it was difficult to isolate pure
compounds IIb, IIc, IIIb, IV, and V, and they were
identified and quantitated in the product mixtures by
1H NMR spectroscopy. The spectrum of a mixture of
ethers IIb and IIc displayed signals typical of iso-
bornyl ether IIb: three singlets at δ 0.95, 1.06, and
1.14 ppm from methyl protons on C8, C9, and C10,
a multiplet at δ ~4.1 ppm from 2-H, and two multiplets
at δ ~6.6 and ~6.9 ppm from aromatic protons; fenchyl
ether IIc was identified by the presence in the spec-
trum of a characteristic multiplet signal of 2-H at
δ 3.86 ppm. Compound IIIb was identified in a mix-
ture with IIIa by comparing with the spectral param-
eters of isobornyl phenols described previously [11].
Cyclic ether V was identified in a mixture with com-
C9
C5
C4
C7
C6
C8
C3
C1
C10
C2
C16
1
pound IV. The H NMR spectrum of that mixture
C11
C18
contained a multiplet signal at δ ~2.7 ppm, which is
typical of V. The identification of IV and V was based
on comparison with the spectra of structurally related
compounds obtained from 3,5-dimethylphenol and
C15
C12
O1
1
C13
β-pinene [12]. The H NMR spectra of camphene (VI)
C14
and limonene (VII) coincided with those of authentic
samples.
C17
According to the chiral HPLC data, the ee values of
ethers (+)- and (–)-IIa were 80 and 93%, respectively,
and of phenols (+)- and (–)-IIIa, more than 99 and
75%, respectively.
Fig. 1. Structure of the molecule of 2,4-dimethyl-6-
{(1R,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl}phenol
(+)-(IIIa) according to the X-ray diffraction data. Non-hy-
drogen atoms are shown as thermal vibration ellipsoids with
a probability of 50%.
The structure of compound (+)-IIIa isolated as
a crystalline substance with high enantiomeric purity
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

ALKYLATION OF 2,4-DIMETHYLPHENOL WITH (+)-α- AND (–)-β-PINENES
591
C9
C7
was determined by X-ray analysis. The symmetry-in-
dependent part of its unit cell contained one molecule
of (+)-IIIa (Fig. 1). Orientation of the bornyl fragment
with respect to the aromatic ring can be described by
the torsion angle C16C11C2C3 equal to 37.0(2)°. Mole-
cules (+)-IIIa in crystal form dimers through weak
intermolecular hydrogen bond O–H···O [H···O 2.20,
O···O 2.996(2) Å, ∠OHO 155°], which leads to disor-
dering of the hydroxy proton. The absolute configura-
tion of molecule (+)-IIIa was estimated as (1R,2R,4S)
using Cu radiation, though the error in the determina-
tion of the Flack parameter was fairly large [0.1(3)]
since the molecule contains only one oxygen atom.
C4
C1
C5
C8
C6
C10
C3
C2
C12
C13
C6′
C5′
C11
C16
O4
C3′
O1
C11′ C1′
O2
O3
C15
C10′
C4′
C7′
C8′
C9′
C18
C14
5'
10'
C17
Me
9'
Me
6'
4'
7'
1'
3'
8'
Me
O
Fig. 2. Structure of the molecule of 2,4-dimethyl-6-
{(1R,2R,4S)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl}phenyl
(1S,4R)-4,7,7-trimethyl-3-oxo-2-oxabicyclo[2.2.1]heptane-1-
carboxylate (+)-(VIII) according to the X-ray diffraction
data. Non-hydrogen atoms are shown as thermal vibration
ellipsoids with a probability of 50%.
11'
O
O
O
Me
H
Me
Me
Me
aromatic ring [torsion angle C11′O1C12C11 83.0(3)°],
presumably for steric reasons. Analogous structure was
found previously for 2,6-diisobornyl-4-formylphenyl
camphanate [13]. The torsion angle C16C11C2C3 which
characterize orientation of the bornyl fragment with
respect to the benzene ring is 39.1(4)°; this value is
close to those found by us previously in (+)-2-bornyl-
phenol and its aminomethyl derivatives [14]. By
analogy with isobornylphenols studied in [2, 15–17],
we can presume that the observed orientation is largely
determined by intramolecular factors. The chiral cen-
ters in the bornyl fragment of (+)-VIII were assigned
(1R,2R,4S) absolute configuration on the basis of the
known configuration of the chiral centers in the cam-
phane moiety.
Me
(+)-VIII
The configuration of chiral centers in compound
(+)-IIIa was confirmed by the X-ray diffraction data
for ester (+)-VIII which was synthesized by acylation
of (+)-IIIa with (1S)-camphanoyl chloride. The sym-
metry-independent part of a unit cell of (+)-VIII in
crystal also comprises one molecule (Fig. 2). The
C1′–C10′ fragment is oriented with respect to the
O1C11′O2 group in such a way that the C4′C7′C1′ plane is
almost orthogonal to the O1C11′O2 plane [the dihedral
angle is 86.8(2)°] and the torsion angles O1C11′C1′C6′
and O2C11′C1′O3 are 36.0(4) and –26.2(4)°, respec-
tively. The O1C11′O2 group is also orthogonal to the
Scheme 2.
Me
*
Me
*
Me
*
Me
*
Me
3
Me
Me
Me
6
4
H+
(5S)
2
(1S)
10
CH2
7
Me
Me
Me
(–)-β-Pinene
A
Me
7
10
Me
Me
Me
7
Me
ArH
H
2
6
3
*
(1R)
(2R)
4
1
*
10
Me
6
(4S)
Ar
5
5
3
Ar
(+)-IIIa (>95%)
Ar = 2-HO-3,5-Me2C6H2.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

CHUKICHEVA et al.
592
Scheme 3.
Me
Me
*
Me
3
Me
6
4
H+
*
(5R)
2
10
Me
(1R)
7
Me
(+)-α-Pinene
Me
10
Me
Me
*
Me
*
Me
Me
Me
Me
7
5
Me
7
H
ArH
6
6
*
4
(2S)
(1S)
1
10
Me
*
2
3
(4R)
Ar
5
3
Me
Me
Ar
B
(–)-IIIa (>85%)
~3,1-H
Me
Me
Me
Me
*
Me
*
Me
10
Me
Me
7
Ar
7
Me
H
(2R)
2
ArH
*
2
3
6
4
(1R)
1
*
6
10
Me
5
(4S)
Ar
5
3
Me
Me
C
(+)-IIIa (<15%)
Ar = 2-HO-3,5-Me2C6H2.
75.48 MHz, respectively, using the residual proton and
carbon signals of the solvent as reference (CHCl3,
δ 7.26 ppm; CDCl3, δC 77.00 ppm). Signals were
assigned with the aid of J-modulation technique
(13C NMR) (for atom numbering, see Scheme 1). The
melting points were determined on a Kofler hot stage
and were not corrected. The optical rotations were
measured on a PolAAr 3001 automated digital polar-
imeter (λ 589 nm).
The steric structure of (+)-VIII confirms our
assumption [14] that C-alkylation of phenols with
(−)-β-pinene involves Wagner–Meierwein rearrange-
ment through carbocation A (Scheme 2), where the
original configuration of C5 is retained. Presumably,
C-alkylation of 2,4-dimethylphenol (I) with (+)-α-pi-
nene with formation of compound (–)-IIIa having
(1S,2S,4R) configuration is mediated by carbocation B.
Some amount (≤15%) of the opposite enantiomer
(+)-IIIa may be formed through carbocation C
(Scheme 3) (In Schemes 2 and 3 the initial terpene and
alkylation products have their own atom numbering;
the C5 atom of pinenes is marked with an asterisk).
The progress of reactions was monitored by TLC
on Sorbfil plates. Compounds I–VII were detected by
treatment with a solution of vanillin in alcohol, fol-
lowed by heating to 100–150°C; spots of VIII were
developed with a solution of Bromocresol Purple,
followed by heating to 100−120°C. HPLC analyses
were carried out on an Agilent 1100 chromatograph
(UV detector, λ 219 nm; 20°C); the ee values of
(+)-IIa, (–)-IIa, (+)-IIIa, and (–)-IIIa were determined
using a Chiralcel OD-H column [Daicel, 25 cm×
4.6 mm, grain size 5 μm; eluent hexane (IIa) or hex-
ane–propan-2-ol, 99:1 (IIIa), flow rate 1.0 mL/min].
Product mixtures were separated by column chroma-
tography on silica gel (70–230 mesh, Alfa Aesar; wet
packing) using petroleum ether–diethyl ether as eluent.
Taking into account that the reactions of phenol
[14] and 2,4-xylenol with (–)-β-pinene yields C-alkyla-
tion products containing a (1R,2R,4S)-bornyl fragment,
analogous mechanism may be proposed for the reac-
tions with other phenols (cresols, xylenols, naphthols).
(1S,2S,4R)-Bornylphenols are obtained from (+)-α-pi-
nene, and enantiomeric (1R,2R,4S)-bornylphenols,
from (–)-β-pinene.
EXPERIMENTAL
The IR spectra were recorded in KBr on a Shimadzu
Petroleum ether with bp 65–70°C and diethyl ether
of analytical grade were used. 2,4-Dimethylphenol,
(+)-α-pinene, (–)-β-pinene, (1S)-camphanoyl chloride,
triethylamine (Sigma–Aldrich), and 4-dimethylamino-
1
IR Prestige 21 spectrometer. The H and 13C NMR
spectra were measured from solutions in CDCl3 on
a Bruker Avance II 300 spectrometer at 300.17 and
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

ALKYLATION OF 2,4-DIMETHYLPHENOL WITH (+)-α- AND (–)-β-PINENES
593
pyridine (Acros Organics) were used without addi-
tional purification. Aluminum 2,4-dimethylphenoxide
was generated in situ.
(14-Me), 19.00 (C9), 19.74 (C8), 20.41 (12-Me), 27.00
(C5), 27.99 (C6), 37.07 (C3), 45.29 (C4), 47.48 (C1),
49.71 (C7), 82.65 (C2), 111.89 (C16), 126.76 (C15),
126.95 (C14), 128.80 (C12), 131.38 (C13), 154.95 (C11).
Found, %: C 83.49; H 10.48. C18H26O. Calculated, %:
C 83.67; H 10.14.
Single crystals of (+)-IIIa and (+)-VIII suitable for
X-ray analysis were obtained by slow evaporation of
their solutions in hexane–diethyl ether. The X-ray dif-
fraction data were acquired on a Bruker Smart Apex2
CCD diffractometer [graphite monochromator, ω-scan-
ning, CuKα radiation (λ = 1.54178 Å) for (+)-IIIa;
MoKα radiation (λ = 0.71073 Å) for (+)-VIII]. The
initial arrays of reflection intensities were processed
using SAINT and SADABS programs built in APEX2
software package [18]. The structures were solved by
the direct method and were refined against F2hkl by the
full-matrix least-squares procedure in anisotropic ap-
proximation for non-hydrogen atoms using SHELXTL
[19]. The coordinates of atoms and their temperature
factors for structures (+)-IIIa and (+)-VIII were de-
posited to the Cambridge Crystallographic Data Centre
(entry nos. CCDC 982664 and 982665).
2,4-Dimethyl-6-{(1R,2R,4S)-1,7,7-trimethylbicy-
clo[2.2.1]hept-2-yl}phenol (+)-(IIIa) and 2,4-di-
methyl-6-{(1S,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]-
hept-2-yl}phenol (–)-(IIIa). Colorless or light yellow
crystals, mp 119–121°C. Enantiomer (+)-IIIa [from
(–)-β-pinene]: [α]D24 = +35.2° (c = 0.46, CHCl3),
ee >99%, retention time 6.35 min; enantiomer (−)-IIIa
[from (+)-α-pinene]: [α]D24 = –26.9 (c = 1.5, CHCl3),
ee 75%, retention time 7.28 min. IR spectrum, ν, cm–1:
3603, 3587 (OH); 1196 (C–O); 2953, 2879, 1479
(C–H). 1H NMR spectrum, δ, ppm: 0.84 s (3H, C10H3),
0.99 s (3H, C9H3), 1.14 s (3H, C8H3), 1.16–1.25 m
(1H, 6-H), 1.41–1.63 m (3H, 3-H, 5-H, 6-H), 1.78–
1.87 m (2H, 4-H, 5-H), 2.19–2.28 m (1H, 3-H), 2.28 s
(3H, 15-Me), 2.31 s (3H, 13-Me), 3.47–3.54 m (1H,
2-H), 4.53 s (1H, OH), 6.84 s (1H, 16-H), 6.95 s (1H,
14-H). 13C NMR spectrum, δC, ppm: 15.02 (C10), 16.32
(13-Me), 18.74 (C9), 19.88 (C8), 20.96 (15-Me), 28.38
(C5), 28.86 (C6), 34.90 (C3), 41.68 (C2), 45.59 (C4),
50.36 (C1), 50.48 (C7), 123.01 (C13), 127.55 (C15),
127.87 (C16), 128.54 (C11), 128.97 (C14), 150.51 (C12).
Found, %: C 84.01; H 9.92. C18H26O. Calculated, %:
C 83.67; H 10.14.
Alkylation of 2,4-dimethylphenol with α- and
β-pinenes. 2,4-Dimethylphenol (I), 2.0 g (16.4 mmol),
was heated to 180°C, 13.5 mg (0.5 mmol) of alumi-
num turnings was added in portions, the mixture was
stirred until it became homogeneous and cooled to
40°C, 4.35 g (31.9 mmol) of (+)-α-pinene or (–)-β-pi-
nene was added, and the mixture was heated for 7 h at
200°C. When the reaction was complete, the mixture
was cooled and diluted with diethyl ether, dilute
aqueous HCl was added to decompose the catalyst,
a 5% solution of sodium hydroxide was then added to
convert unreacted 2,4-dimethylphenol into phenoxide,
and the mixture was washed with water until neutral
reaction. The organic extract was dried over anhydrous
sodium sulfate, the solvent was distilled off, and the
residue was separated by column chromatography
using petroleum ether–diethyl ether as eluent.
Enantiomer (+)-IIIa. C18H26O. Monoclinic crystal
system. Unit cell parameters (120 K): a = 19.7564(3),
b = 7.38690(10), c = 13.3708(4) Å; β = 130.399(1)°;
V = 1486.02(5) Å3; Z = 4; space group C2; dcalc
=
1.155 g/cm3; µ = 0.522 mm–1. Total of 10353 reflec-
tions intensities were measured (θmax = 67°) from
a 0.22×0.18×0.18-mm single crystal; the structure
was refined using 2522 independent reflections (Rint
=
0.0176). Final divergence factors: wR2 = 0.0809 (all
reflections), R1 = 0.0306 [2520 reflections with I > 2σ
(I)]; goodness of fit 1.059; Flack parameter 0.1(3).
1,7,7-Trimethyl-2-endo-(2,4-dimethylphenoxy)-
bicyclo[2.2.1]heptane (IIa). Colorless oily liquid.
Enantiomer (+)-IIa [from (+)-α-pinene]: [α]D25 = +61.1°
(c = 3.4, CHCl3), ee 80%, retention time 5.36 min;
enantiomer (−)-IIa [from (–)-β-pinene], [α]D24 = –86.4°
(c = 0.41, CHCl3), ee 93%, retention time 6.25 min. IR
spectrum, ν, cm–1: 2951, 2876, 1502 (C–H), 1254
2,4-Dimethyl-6-(1,7,7-trimethylbicyclo[2.2.1]-
hept-2-exo-yl)phenol (IIIb) was isolated in a mixture
with compound IIIa as a semicrystalline material.
1H NMR spectrum, δ, ppm: 0.80 s (3H, C10H3), 0.86 s
and 0.91 s (3H each, C8H3, C9H3); 1.29–1.52 m, 1.53–
1.74 m, and 1.77–1.94 m (2H each, 3-H, 4-H, 5-H,
6-H), 2.12–2.33 m (1H, 3-H), 2.22 s (3H, 13-Me),
2.26 s (3H, 15-Me), 3.06 t (1H, 2-H, J = 8.8 Hz),
4.51 s (1H, OH), 6.79 s and 6.97 s (1H each, 14-H,
16-H). 13C NMR spectrum, δC, ppm: 12.39 (C10), 16.13
(13-Me), 20.31 (C9), 20.90 (15-Me), 21.42 (C8), 27.55
1
(=C–O), 1136 (C−O). H NMR spectrum, δ, ppm:
0.99–1.02 m (9H, C8H3, C9H3, C10H3), 1.15–1.20 m
(1H, 3-H), 1.33–1.38 m (2H, 5-H, 6-H), 1.78–1.82 m
(2H, 4-H, 6-H), 2.30–2.44 m (2H, 3-H, 5-H), 2.26 s
(3H, 14-Me), 2.29 s (3H, 12-Me), 4.30–4.33 m (1H,
2-H), 6.60–6.63 m (1H, 13-H), 6.94–6.99 m (2H, 15-H,
16-H). 13C NMR spectrum, δC, ppm: 13.82 (C10), 16.44
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

CHUKICHEVA et al.
594
(C5), 34.17 (C6), 40.08 (C3), 45.55 (C2), 45.80 (C4),
48.08 (C1), 49.64 (C7), 122.34 and 128.39 (C11, C13,
C15), 126.43 and 128.61 (C14, C16), 150.74 (C12).
19.75 (C8, C9), 21.23 (15-Me), 28.35 (C5), 28.85 (C3),
29.01 and 31.67 (C5′, C6′), 35.08 (C6), 41.91 (C4),
45.44 (C2), 50.36 and 50.42 (C1, C7), 54.10 and 54.84
(C4′, C7′), 90.85 (C1′), 128.35 and 129.47 (C14, C16),
134.89 (C11), 146.09 (C12), 166.02 and 177.83 (C3′,
C11′). Found, %: C 76.39; H 8.88. C28H38O4. Calculat-
ed, %: C 76.68; H 8.73.
5-Isopropyl-2,6-methano-2,8,10-trimethyl-
3,4,5,6-tetrahydro-2H-1-benzoxocine (IV). Light
brown oily liquid. IR spectrum, ν, cm–1: 1217 (=C−O);
1
1155 (C–O); 2945, 2870, 1479 (C–H). H NMR spec-
trum, δ, ppm: 1.00 d (3H, C17H3, J = 6.6 Hz), 1.12 d
(3H, C16H3, J = 6.6 Hz), 1.39 s (3H, C14H3), 1.52–
1.94 m (8H, 6-H, 7-H, 8-H, 9-H, 15-H), 2.20 s (3H,
10-Me), 2.29 s (3H, 12-Me), 3.03 m (1H, 5-H), 6.68 s
(1H, 13-H), 6.83 s (1H, 11-H). 13C NMR spectrum, δC,
ppm: 15.97 (10-Me), 20.10 (C7), 20.41 (12-Me), 21.31
(C17), 22.07 (C16), 26.33 (C15), 29.50 (C14), 30.76 (C9),
34.76 (C5), 35.48 (C8), 47.45 (C6), 74.13 (C1), 123.66
(C10), 126.02 (C13), 126.73 (C12), 127.17 (C4), 129.11
(C11), 152.59 (C3). Found, %: C 83.49; H 10.48.
C18H26O. Calculated, %: C 83.77; H 10.10.
Rhombic crystals; unit cell parameters (120 K): a =
7.8057(7), b = 7.9220(7), c = 39.851(4) Å; V =
2464.3(4) Å3; Z = 4; space group P212121; dcalc
=
1.182 g/cm3; µ = 0.077 mm–1. Total of 35501 reflec-
tion intensities were measured (θmax = 28.3°) from
a 0.18×0.12×0.02-mm single crystal; the structure
was refined using 3517 independent reflections (Rint
=
0.1056); final divergence factors wR2 = 0.1206 (all
reflections), R1 = 0.0509 [2292 reflections with I >
2σ(I)]; goodness of fit 1.102.
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tetrahydro-2H-1-benzoxocine (V) was isolated in
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1
a mixture with compound IV. H NMR spectrum, δ,
ppm: 0.85 d (3H, C17H3, J = 5.0 Hz), 1.00 d (3H,
C16H3, J = 5.0 Hz), 1.18 d (3H, C14H3, J = 7.0 Hz),
1.61–2.02 m (8H, 6-H, 7-H, 8-H, 9-H, 15-H), 2.23 s
(3H, 10-Me), 2.31 s (3H, 12-Me), 2.71 m (1H, 5-H),
6.79 s (1H, 13-H), 6.95 s (1H, 11-H).
2,4-Dimethyl-6-{(1R,2R,4S)-1,7,7-trimethylbicy-
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methylaminopyridine were added, and the mixture
was heated for 2 h under reflux with stirring in
a stream of argon. The mixture was evaporated and
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[α]D23 = +30.7° (c = 0.39, CHCl3). IR spectrum, ν, cm–1:
2953, 2878, 1474 (C–H); 1796, 1761 (C=O); 1261
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0.92 s and 1.00 s (3H each, C8H3, C9H3); 1.13 s, 1.16 s,
and 1.18 s (3H each, C8′H3, C9′H3, C10′H3); 1.28–
1.64 m (3H) and 1.69–2.05 m (5H) (4-H, 5-H, 5′-H,
6-H, 6′-H), 2.07–2.32 m (2H, 3-H, 6-H), 2.12 s (3H,
13-Me), 2.34 s (3H, 15-Me), 2.45–2.63 m (1H, 3-H),
3.15 br.m (1H, 2-H), 6.92 s and 7.02 s (1H each, 14-H,
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13
16-H). C NMR spectrum, δC, ppm: 9.62 (C10′), 14.58
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014

ALKYLATION OF 2,4-DIMETHYLPHENOL WITH (+)-α- AND (–)-β-PINENES
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 4 2014