Oxidation of bicyclic monoterpene ketones with Caro's acid

Article abstract of DOI:10.1134/S1070428012090102

Previously unknown seven-membered lactones, (1R,1'R,5S,5'S)-5,5'-oxybis(1, 8,8-trimethyl-2-oxabicyclo[ 3.2.1]octan-3-one), 2,2-dimethyl-1,6-dioxaspiro[2.6] nonan-7-one, 4-(1-hydroxy-1-methylethyl)-7- methyloxepan-2-one, and (4R,4'R,7S,7'S)-4,4'-[oxybis(propane-2,2-diyl)]bis(7-methyloxepan-2-one), were synthesized by the Baeyer-Villiger reaction using Caro's acid as a result of oxidative and skeletal transformations of bicyclic monoterpene ketones, (+)-camphor, (+)-nopinone, and (-)-isocaranone.

Full text of DOI:10.1134/S1070428012090102

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 9, pp. 1210–1215. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © G.Yu. Ishmuratov, V.A. Vydrina, M.P. Yakovleva, Yu.A. Galkina, I.F. Lobko, R.R. Muslukhov, E.M. Vyrypaev, A.G. Tolstikov, 2012,
published in Zhurnal Organicheskoi Khimii, 2012, Vol. 48, No. 9, pp. 1211–1216.
Oxidation of Bicyclic Monoterpene Ketones with Caro’s Acid
G. Yu. Ishmuratov, V. A. Vydrina, M. P. Yakovleva, Yu. A. Galkina, I. F. Lobko,
R. R. Muslukhov, E. M. Vyrypaev, and A. G. Tolstikov
Institute of Organic Chemistry, Ufa Research Center, Russian Academy of Sciences,
pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
e-mail: insect@anrb.ru
Received March 28, 2012
Abstract—Previously unknown seven-membered lactones, (1R,1′R,5S,5′S)-5,5′-oxybis(1,8,8-trimethyl-2-oxa-
bicyclo[3.2.1]octan-3-one), 2,2-dimethyl-1,6-dioxaspiro[2.6]nonan-7-one, 4-(1-hydroxy-1-methylethyl)-7-
methyloxepan-2-one, and (4R,4′R,7S,7′S)-4,4′-[oxybis(propane-2,2-diyl)]bis(7-methyloxepan-2-one), were syn-
thesized by the Baeyer–Villiger reaction using Caro’s acid as a result of oxidative and skeletal transformations
of bicyclic monoterpene ketones, (+)-camphor, (+)-nopinone, and (–)-isocaranone.
DOI: 10.1134/S1070428012090102
The chemistry of sterically hindered seven-mem-
bered monoterpene lactones has been poorly studied so
far; only a few examples of synthesis and transforma-
tions of such compounds have been reported [1].
A convenient and frequently used procedure for the
synthesis of monoterpene lactones is based on Baeyer–
Villiger oxidation of the corresponding ketones with
m-chloroperoxybenzoic [2–5], monoperoxyphthalic
[6, 7], peroxyacetic [4, 7, 8], perfluoroperoxybenzoic
[9], decaneperoxysulfonic [10], and other organic
peroxy acids [11, 12]. However, the results of these
reactions were not always satisfactory (low conversion
and yield); furthermore, the oxidants are expensive or
difficultly accessible (preparation of some oxidants
requires special equipment).
oxidation of camphor (I) with Caro’s acid at room
temperature over a period of 24 h afforded a mixture of
lactones, α-campholide (II) and pentanolide III (yield
22 and 15%, respectively) [14]. It was found [9] that
compound III is the product of consecutive acid-cata-
lyzed rearrangement and oxidation of β-campholide
(IV) (Scheme 1).
The poor yield of target lactones II and III may be
attributed to the low conversion of (+)-camphor (I). In
order to enhance the conversion the reaction was
prolonged to 7 days [13], and α-campholide (II) was
obtained in 30% yield. No rearrangement product of
β-campholide (pentanolide III) was detected, but 30%
of bis-lactone V was isolated. Presumably, the latter
was formed as a result of oxidation of β-campholide to
tertiary alcohol A [8] which underwent dehydration to
ether V under acidic conditions (Scheme 2).
Caro’s acid (peroxymonosulfuric acid) [13] seems
to be a reactive, low-expensive, and accessible reagent
for Baeyer–Villiger oxidation; it has been rarely used
in transformations of cyclic monoterpene ketones and
is capable of promoting skeletal rearrangements. Obvi-
ously, cage-like structure of bicyclic ketones should
hinder their oxidation with Caro’s acid. In fact, the
The structure of compounds II and V was deter-
1
mined by H and 13C NMR spectroscopy. The chem-
ical shifts of geminal protons (δ 4.44 ppm, d.d.d, and
δ 4.07 ppm, d.d) and carbon atom in the OC4H2 group
(δC 73.56 ppm, t) and downfield position of signal
Scheme 1.
Me
Me
Me
O
Me
Me
Me
Me
Me
Me
HO
O
H2SO5
(1) H2SO4; (2) H2SO5
+
III
O
O
Me
Me
Me
O
OH
O
O
I
II, 22%
III, 15%
IV
1210

OXIDATION OF BICYCLIC MONOTERPENE KETONES WITH CARO’S ACID
1211
Scheme 2.
O
Me
Me
Me
O
Me
OH
O
Me
Me
Me
Me
H2SO5, 7 days
H2SO4
–H2O
Me
+
Me
2
V
O
Me
O
O
Me
Me
Me
O
O
O
Me
A
O
I
II, 30%
V, 30%
from the bridgehead C1 atom (δC 53.14 ppm, s) in the
NMR spectra of α-campholide (II) indicated the posi-
tion of lactone moiety in molecule II. Unlike α-cam-
pholide (II), the 13C NMR spectrum of V contained
two downfield singlets at δC 84.50 (C5) and 99.53 ppm
(C1), while protons in the C4H2 group resonated in
a considerably stronger field (δ 2.87 ppm, d.d.d, and
δ 2.73 ppm, d).
singlets (δC 83.07 and 94.13 ppm), two quartets
(δC 20.89 and 24.32 ppm) from the cis- and trans-
methyl groups, and a singlet (δC 175.64) from the ester
1
carbonyl carbon atom. The H NMR spectrum of VII
contained two singlets at δ 1.09 and 1.17 ppm from
methyl protons and signals from two isolated ethylene
fragments C4H2–C5H2 and C8H2–C9H2 which were
assigned using two-dimensional correlation techniques
(COSY C–H and COSY H–H). The NMR data for
compound VII indicated that the oxidation of VI in-
volved cleavage of the C1–C7 bond in the cyclobutane
The mass spectrum (atmospheric pressure chemical
ionization, positive ion detection; MeOH–H2O, 1:1) of
lactone II contained a strong peak from the protonated
molecular ion [M + H]+, m/z 169.00 and an appreciable
peak from the exciton ion [M + H+·M] ≡ [2M + H]+
which is typically formed under chemical ionization
conditions, especially under atmospheric pressure.
Also, peak of [M + H2O]+ ion (m/z 186.05), which is
likely to be formed via charge exchange, peak of MH+
associate with MeOH molecule (m/z 201.00), and
weak fragment ion peaks typical of camphene deriva-
tives (m/z 123.00, 95.00, 81.00) were present. The
following ions were fairly abundant in the APCI mass
spectrum of V (MeOH): [M2 + H]+ (m/z 185.00,
18.2%), [M3 + H]+ (m/z 167.00, 100%), [M + H]+
(m/z 369.15, 56.05%). Exciton peak with m/z 367.05
(100%, [MH]–) was observed in the APCI spectrum
with negative ion detection.
1
fragment and formation of oxirane ring. The H NMR
spectrum of VII lacked signals assignable to hydroxy
protons that might have been formed as a result of
oxidation.
The APCI mass spectrum of VII with negative ion
detection was weakly informative. The positive ion
spectrum revealed abundant ions with m/z 171.05,
153.05, 125.00, and 188.05. The latter is likely to arise
from charge exchange; the peak with m/z 171.05 corre-
sponds to the protonated molecular ion of VII, and
those with m/z 153.05 and 125.05 are obviously frag-
ment ion peaks.
A probable mechanism of formation of epoxy
lactone VII is shown in Scheme 4. The carbonyl group
in the α-position with respect to the C1 bridgehead
atom in molecule VI aligns the OH group in the
peroxide fragment of Caro’s acid toward the C1–C7
bond via hydrogen bond. Optically active epoxy
ketone C is then formed through “butterfly” transition
state B [15]. Baeyer–Villiger oxidation of symmetric
intermediate C is equally probable at both positions,
resulting in the formation of equal amounts of regio-
isomers (S)-VII and (R)-VII that are simultaneously
epimers. Therefore, the product is racemic (i.e., op-
tically inactive) epoxy lactone VII.
The reaction of (+)-nopinone (VI) with Caro’s acid
gave racemic epoxy lactone VII as a result of oxida-
tion and subsequent opening of the cyclobutane ring at
the C1–C7 bond (Scheme 3). The product was isolated
by chromatography in 65% yield. Compound VII
displayed in the 13C NMR spectrum two downfield
Scheme 3.
O
1
H2SO5, 7 days
O
O
We have found that the oxidation of (+)-isocara-
none (VIII) with Caro’s acid follows analogous pattern
involving cleavage of the cyclopropane ring at the
C1–C7 bond with formation of hydroxy lactone IX and
Me
Me
Me
7
O
5
Me
VI
VII
[α]D20 = 0° (c = 3.24, CHCl3)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 9 2012

ISHMURATOV et al.
1212
Scheme 4.
O
O
O
Me
Me
H2SO5
H
O
H
O
O
O
H
–H2SO4
Me
Me
OH
O
S
O
O
S
O
O
OH
Me
Me
Me
Me
O
VI
B
C
O
O
O
O
H2SO5
+
Me
O
Me
O
Me
Me
(S)-VII
(R)-VII
ether X (Scheme 5). The presence of a CH3C7H–C6H2–
C5H2 fragment in molecules IX and X was identified
by NMR spectroscopy using two-dimensional correla-
tion techniques (COSY H–H and COSY C–H). The
endocyclic lactone oxygen atom is linked to C7 (δ, δC,
ppm: IX, 67.18 d, 3.75 m; X, 71.37 d, 4.07 m).
Lactones IX and X displayed in the 13C NMR spectra
signals from carbonyl carbon atoms (δC 175.88,
178.68 ppm) and three upfield signals from endocyclic
methylene groups (δC, ppm: IX, 25.61 t, 34.77 t,
37.40 t; X, 25.41 t, 33.38 t, 38.32 t).
The assumed structure of IX and X was also con-
firmed by their mass spectra. The APCI spectrum of
IX (MeOH–H2O, 1 :1; positive ion detection) was
informative. It contained a strong peak from the pro-
tonated molecular ion [M + H]+, m/z 187.00 and an ap-
preciable peak from the exciton ion [M + H+ ·M] ≡
[2M + H]+, m/z 355.05, which is typical of chemical
ionization processes, especially under atmospheric
pressure. In addition, peaks from [M + H2O]+·,
m/z 204.05 (presumably, as a result of charge ex-
change) and [M + H]+ associate with MeOH molecule,
m/z 219.00, were observed.
The coupling constants for the 7-H proton (J =
11.6, 4.1 Hz) indicated equatorial orientation of the
7-Me group in IX and X, and vicinal coupling con-
stants for the 4-H proton (J4,3-ax = 6.9, J4,3-eq = 6.0 Hz)
were consistent with its equatorial orientation and
hence axial orientation of the 4-isopropyl group.
Taking into account the presence of a doublet signal
from the 7-Me group (δ 1.1 ppm) and a singlet from
two methyl groups in the isopropyl fragment, com-
pounds IX and X were assumed to be formed as
a single diastereoisomer. Downfield singlets from C8 in
IX (δC 86.91 ppm) and X (δC 82.49 ppm), as well as
singlets from protons in the methyl groups attached to
C8 (δ 1.03 and 1.28 ppm), indicated functionalization
at the tertiary carbon atom of the isopropyl group.
The APCI mass spectrum of X contained the mo-
lecular ion peak with m/z 355.15 (Irel 11.2%). The MS
analysis is likely to involve decomposition (hydrol-
ysis), and the most abundant ions are [M2 + H]+,
m/z 187.05 (100%) and [M3 + H]+, m/z 169.00
(51.4%). In the negative ion mass spectrum of X, only
[M2 – H]–, m/z 185.05 (93.6%), [2M – H]–, m/z 371.10
(100%), and [M2H + 36]– ion peaks, m/z 221.05
(12.1%), were detected. A probable scheme of forma-
tion of lactones IX and X includes two concurrent
processes, Baeyer–Villiger oxidation and opening of
the cyclopropane ring (Scheme 6).
The oxidation of (+)-isopinocamphone (XI) with
Caro’s acid over a period of 7 days led to the formation
Scheme 5.
Me
Me
O
1
O
Me
O
O
7
O
Me
Me
H2SO5, 7 days
Me
+
1
3
Me
4
O
O
7
8
Me
Me
OH
Me
Me
VIII
O
Me
(4R,7S)-IX, 54%
(4R,4'R,7S,7'S)-X, 28%
[α]D20 = +25.7° (c = 3.24, CHCl3) [α]D20 = –8.3° (c = 0.80, CHCl3)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 9 2012

OXIDATION OF BICYCLIC MONOTERPENE KETONES WITH CARO’S ACID
1213
Scheme 6.
O
O
H2SO5 (Baeyer–Villiger)
Me
VIII
IX + X
H2SO4
H2O
–H+
H2SO4
–H2O
Me
Me
Me
Me
OH
Me
Me
Me
O
Me
of a mixture of products which could not be identified.
After 5 h, hydroxy ketone XII was detected as oxida-
tion product at the tertiary carbon atom, which is con-
sistent with published data for the oxidation with
m-chloroperoxybenzoic acid [5] (Scheme 7).
formed on a Shimadzu GC-2014 instrument (DB-
35MS capillary column, 0.20 mm i.d.; oven tempera-
ture 50–360°C; carrier gas helium). The atmospheric
ionization mass spectra were recorded on an HP 5972A
mass-selective detector coupled with an HP 5890 gas
chromatograph [HP 5MS capillary column, 25 m×
0.25 mm; oven temperature programming from 40°C
(5 min) to 250°C at a rate of 8 deg/min; injector tem-
perature 260°C; a.m.u. range 28–300]. The elemental
compositions of all newly synthesized compounds
were consistent with the calculated values. Silica gel
60–200 μm (Lancaster) was used for column chro-
matography. TLC analyses were run on Sorbfil UV-
254 plates (Krasnodar, Russia). The optical rotations
were measured on a Perkin Elmer 241-MC
polarimeter.
Scheme 7.
Me
Me
OH
O
O
H2SO5, 7 days
Me
Me
Me
Me
XI
XII
Thus, our results and published data demonstrate
that Caro’s acid is an efficient oxidant toward bicyclic
monoterpene ketones, which is capable of promoting
skeletal rearrangements. The use of Caro’s acid in
Baeyer–Villiger oxidation enabled us to synthesize
a number of seven-membered lactones, including four
previously unknown compounds: (1R,1′R,5S,5′S)-5,5-
oxybis(1,8,8-trimethyl-2-oxabicyclo[3.2.1]octan-3-
one) (V), 2,2-dimethyl-1,6-dioxaspiro[2.6]nonan-7-one
(VII), 4-(1-hydroxy-1-methylethyl)-7-methyloxepan-
2-one (IX), and (4R,4′R,7S,7′S)-4,4′-[oxybis(propane-
2,2-diyl)]bis(7-methyloxepan-2-one) (X).
General procedure for the oxidation of ketones
with Caro’s acid. A mixture of 4.8 ml of concentrated
sulfuric acid and 1.6 ml of water was cooled to 0°C,
3.26 g (12.0 mmol) of K2S2O8 was added under
stirring, 5.2 ml of water was added dropwise, and
6.5 mmol of monoterpene ketone I, VI, VIII, or XI
was then added dropwise. The mixture was stirred for
0.5 h at 0°C and for 7 days at 20°C, carefully poured
into 4.0 ml of cold water, and extracted with methylene
chloride (3×50 ml). The extract was washed in succes-
sion with saturated solutions of NaHCO3, Na2S2O3,
and NaCl, dried over MgSO4, and evaporated.
EXPERIMENTAL
The IR spectra were recorded from films on
a Shimadzu IR Prestige-21 spectrometer with Fourier
The oxidation of R-(+)-camphor (I) gave 0.68 g of
a mixture of compounds II and V at a ratio of 1:1
(GLC). By column chromatography (silica gel, gradi-
ent elution with hexane to hexane–tert-butyl methyl
ether, 1:1) we isolated 0.18 g (17%) of II and 0.3 g
(17%) of V.
1
transform. The H and 13C NMR spectra were meas-
ured on a Bruker AM-300 spectrometer at 300 and
75.47 MHz, respectively; signals were assigned, and
coupling constants were determined, using two-dimen-
sional correlation (COSY C–H, COSY H–H) and
double resonance techniques. The 13C NMR spectra
were run with broad-band decoupling from protons
and using JMOD experiments. The chemical shifts
were determined relative to tetramethylsilane as inter-
nal reference. Chromatographic analysis was per-
1,8,8-Trimethyl-3-oxabicyclo[3.2.1]octan-2-one
(II). Rf 0.63 (petroleum ether– tert-butyl methyl ether,
1:1), [α]D21 = –20.0° (c = 2.04, CHCl3). H NMR spec-
1
trum, δ, ppm: 0.95, 1.08 s (6H, 8-CH3), 1.14 s (3H,
1-CH3), 1.64–1.85 m (2H, endo-6-H, endo-7-H),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 9 2012

ISHMURATOV et al.
1214
1.88 d.d (1H, 5-H, J = 6.8, 2.9 Hz), 1.98–2.17 m (2H,
exo-6-H, exo-7-H), 4.07 d.d (1H, 4-Hax, J = 13.6,
1.2 Hz), 4.44 d.d.d (1H, 4-Heq, J = 13.6, 3.1 Hz) [9].
13C NMR spectrum, δC, ppm: 14.1 q (1-CH3), 19.83 q
and 22.21 q (8-CH3), 26.69 t (C7), 35.41 t (C6), 41.68 s
(C8), 43.99 d (C5), 53.14 s (C1), 73.56 t (C4), 176.56 s
(C2). Mass spectrum, m/z (Irel, %): 338.05 (16.42),
337.05 (69.56) [2M + H]+, 228.05 (3.27), 212.00
(2.12), 210.0 (6.78), 201.00 (55.98) [M + H +
CH3OH]+, 199.05 (3.27), 186.05 (8.22) [M + H2O]+,
170.00 (30.32), 169.00 (100.00) [M + H]+, 123.00
(19.11), 95.00 (1.09), 81.00 (1.71).
(Irel, %): 188.05 (20.3) [M + H2O]+, 172.05 (19.6),
171.05 (100) [M + H]+, 153.05 (3.6) [M + H – H2O]+,
125 (3.5) [M + H – H2CO2]+.
The oxidation of (–)-isocaranone (VIII, ee 99%)
obtained from (+)-Δ3-carene according to [17] gave
1.0 g of a mixture of compounds IX and X at a ratio of
2:1 (GLC). By column chromatography on silica gel
(gradient elution with petroleum ether to petroleum
ether–tert-butyl methyl ether, 1:1) we isolated 0.6 g
(54%) of IX and 0.3 g (28%) of X.
(4R,7S)-4-(1-Hydroxy-1-methylethyl)-7-methyl-
oxepan-2-one (IX). Rf 0.22 (petroleum ether–tert-
butyl methyl ether, 1:2), [α]D21 = +25.7° (c = 3.24,
(1R,1′R,5S,5′S)-5,5′-Oxybis(1,8,8-trimethyl-2-
oxabicyclo[3.2.1]octan-3-one) (V). Rf 0.34 (petroleum
ether–tert-butyl methyl ether, 1:1), [α]D21 = +0.5° (c =
1.71, CHCl3). IR spectrum (KBr), ν, cm–1: 1730
1
CHCl3). H NMR spectrum, δ, ppm: 1.12 d (3H,
7-CH3, J = 6.2 Hz), 1.20 s and 1.38 s (3H each,
8-CH3), 1.33–1.37 m (1H, 5-Hax), 1.55–1.76 m (2H,
5-Heq, 6-Hax), 1.62–1.68 m (1H, 4-H), 2.08–2.17 m
(1H, 6-Heq), 2.54 d.d (1H, 3-Hax, J = 7.5, 3.0 Hz),
2.60 d.d (1H, 3-Heq, J = 7.5, 3.4 Hz), 3.70–3.81 m (1H,
7-H). 13C NMR spectrum, δC, ppm: 21.62 q and
27.26 q (8-CH3), 23.36 q (7-CH3), 25.61 t (C5), 34.77 t
(C6), 37.40 t (C3), 45.49 d (C4), 67.18 d (C7), 86.91 s
(C8), 175.88 s (C2). Mass spectrum, m/z (Irel, %):
356.05 (17.62), 355.05 (67.06) [2M + H]+, 246.05
(5.48), 230.00 (2.18), 228.0 (5.66), 219.00 (49.74)
[M + H + CH3OH]+, 217.05 (5.58), 204.05 (7.68)
[M + H2O]+, 188.00 (38.02), 187.00 (100) [M + H]+.
1
(C=O), 1097, 1080, 1051 (C–O–C). H NMR spec-
trum, δ, ppm: 0.85 s and 1.17 s (3H each, 8-CH3),
1.31 s (3H, 1-CH3), 1.48–1.69 m (2H, endo-6-H, endo-
7-H), 2.04–2.12 m (2H, exo-6-H, exo-7-H), 2.73 d (1H,
endo-4-H, J = 17.7 Hz), 2.86 d.d.d (1H, exo-4-H, J =
17.7, 2.4, 1.2 Hz). 13C NMR spectrum, δC, ppm:
14.75 q (1-CH3), 22.64 q and 23.39 q (8-CH3), 37.31 t
(C6), 39.65 t (C7), 44.30 s (C8), 44.33 t (C4), 84.50 s
(C5), 99.53 s (C1), 176.6 s (C3). Mass spectrum, m/z
(Irel, %), Scan C+: 370.10 (12.47), 369.15 (56.05)
[2M3 + H + 36]+, 355.05 (1.60) [M + H]+, 256.95
(4.66), 238.95 (25.67), 206.95 (11.83), 202.05 (27.88),
201.05 (8.67), 195 (3.09), 185.00 (18.19) [M2 + H]+,
181.00 (9.78), 168.00 (5.37), 167.00 (100) [M3 + H]+,
149.00 (5.59), 147.07 (17.29), 139.00 (3.62), 121.05
(14.50), 111.05 (3.05), 107.05 (4.16), 105.00 (4.41);
Scan C–: 368.00 (25.71), 367.05 (100) [2M1 – H + 36]–
, 230.00 (25.41), 229.00 (11.72), 226.00 (8.96), 220.00
(14.63), 219.00 (56.57).
(4R,4′R,7S,7′S)-4,4′-[Oxybis(propane-2,2-diyl)]-
bis(7-methyloxepan-2-one) (X). Rf 0.37 (petroleum
ether–tert-butyl methyl ether, 1:2). [α]D21 = –8.3° (c =
1
0.80, CHCl3). H NMR spectrum, δ, ppm: 1.03 s and
1.28 s (3H each, 8-CH3), 1.19 d (3H, 7-CH3, J =
6.1 Hz), 1.34–1.47 m (1H, 5-Hax), 1.63–1.72 m (2H,
4-H, 6-Hax), 1.71–1.83 m (2H, 5-Heq, 6-Heq), 2.28 d.d
(1H, 3-Hax, J = 9.8, 6.9 Hz), 2.33 d.d (1H, 3-Heq, J =
9.8, 6.0 Hz), 4.02–4.13 m (1H, 7-H). 13C NMR spec-
trum, δC, ppm: 21.34 q and 27.98 q (8-CH3), 23.04 q
(7-CH3), 25.41 t (C5), 33.38 t (C6), 38.32 t (C3),
47.22 d (C4), 71.37 d (C7), 82.49 s (C8), 178.68 s (C2).
Mass spectrum, m/z (Irel, %): Scan C+: 391 (4.95),
357.10 (2.77), 356.10 (2.35), 355.15 (11.24) [M1 +
H]+, 337.10 (2.31), 325.20 (3.99), 297.0 (3.13), 280.05
(9.00), 279 (49.47), 276.95 (5.60), 275.90 (30.51),
251.0 (4.00), 244.0 (5.71), 229.15 (5.60), 228.0
(21.25), 215.0 (4.29), 212.10 (9.12), 211.10 (7.67),
210.05 (51.48), 201.05 (5.22), 199.15 (5.33), 198.05
(10.99), 189.95 (7.64), 188 (11.45), 187.05 (100)
[M2 + H]+, 185.0 (42.46), 184.05 (22.65), 176.0 (5.42),
171.05 (5.87), 170.1 (6.07), 169.00 (51.44) [M3 + H]+,
167.0 (5.80), 162.05 (13.73), 157.05 (12.83), 151.05
2,2-Dimethyl-1,6-dioxaspiro[2.6]nonan-7-one
(VII) was isolated by flash chromatography in the
oxidation of (+)-nopinone (VI) prepared from α-pinene
according to [16]. Yield 0.83 g (65%), Rf 0.90 (petro-
leum ether–tert-butyl methyl ether, 1:1), [α]D21 = 0.0°
(c = 3.24, CHCl3). IR spectrum (KBr), ν, cm–1: 1776
1
(C=O); 2922, 2953 (C–H, oxirane). H NMR spec-
trum, δ, ppm: 1.09 s and 1.17 s (3H each, CH3),
2.08 d.d (1H, 9-H, J = 8.1, 3.2 Hz), 2.11 d.d (1H, 9-H,
J = 8.1, 5.4 Hz), 2.17 d.d (1H, 4-H, J = 9.3, 8.7 Hz),
2.21 d.d.d (1H, 4-H, J = 9.3, 6.7, 1.2 Hz), 2.45–2.67 m
(2H, 8-H), 3.85 d.d (1H, 5-H, J = 8.6, 8.0, 6.7 Hz),
3.89 d.d.d (1H, 5-H, J = 8.6, 8.0, 2.3 Hz). 13C NMR
spectrum, δC, ppm: 20.89 q and 24.32 q (CH3), 27.41 t
(C9), 29.16 t (C8), 37.41 t (C4), 63.46 t (C5), 83.07 s
(C2), 94.13 s (C3), 175.64 s (C7). Mass spectrum, m/z
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 9 2012

OXIDATION OF BICYCLIC MONOTERPENE KETONES WITH CARO’S ACID
1215
5. Thomas, A.F. and Rey, F., Tetrahedron, 1992, vol. 48,
(13.82), 143.05 (23.85), 135.05 (10.30), 133.0 (7.98),
127.0 (4.10), 121.05 (14.55), 109.05 (13.18), 107.0
(5.84), 83.05 (10.47); Scan C–: 372.10 (22.76), 371.10
(100) [2M2 – H]–, 355.10 (3.48), 329.15 (5.00), 223.0
(3.68), 226.05 (3.90), 221.05 (12.06) [M2 – H + 36]–,
186.05 (10.41), 185.05 (93.6) [M2 – H]–, 173.10 (0.97).
p. 1927.
6. Masao, H., Shigetaka, Y., Akiko, S., James, H.C., and
Takashi, M., Synth. Commun., 1996, vol. 26, p. 4591.
7. Brougham, P., Cooper, M.S., Cummerson, D.A.,
Heaney, H., and Thompson, N., Synthesis, 1987,
p. 1015.
(1R,2R)-2-Hydroxy-2,6,6-trimethylbicyclo[3.1.1]-
heptan-3-one (XII) was isolated by flash chromatog-
raphy (petroleum ether) in the oxidation of (+)-iso-
pinocamphone (XI, ee 90%) obtained from (+)-α-
8. Sauers, R.R., J. Org. Chem., 1959, vol. 24, p. 925.
9. Dzhemilev, U.M., Vostrikov, N.S., Moiseenkov, A.M.,
and Tolstikov, G.A., Izv. Akad. Nauk SSSR, Ser. Khim.,
1981, p. 1320.
10. Safiullin, R.L., Volgarev, A.N., Ishmuratov, G.Yu.,
Yakovleva, M.P., Odinokov, V.N., Komissarov, V.D.,
and Tolstikov, G.A., Dokl. Akad. Nauk SSSR, 1991,
vol. 316, p. 640.
11. Lapalme, R., Borschberg, H.-J., Soucy, P., and Deslong-
champs, P., Can. J. Chem., 1979, vol. 57, p. 3272.
12. Dhillon, S.R., Gautam, K.V., Singh, S., and Singh, J.,
pinene according to [18]. Yield 0.25 g (23%), [α]D20
=
1
+27.4° (c = 3.00, CHCl3). H NMR spectrum, δ, ppm:
0.90 s, 1.38 s, and 1.40 s (3H each, CH3); 1.96–2.02 m
(1H, 5-H), 2.11–2.15 m (2H, 1-H, 6-H), 2.45–2.47 m
(1H, 6-H), 2.55–2.70 m (2H, 4-H). 13C NMR spec-
trum, δC, ppm: 22.8 q and 25.3 q (6-CH3), 27.3 q
(2-CH3), 28.5 t (C7), 38.4 d (C5), 39.3 s (C6), 43.0 t
(C4), 49.8 d (C1), 77.2 s (C2), 214.0 s (C3).
Indian J. Chem., Sect. B, 1991, vol. 30, p. 574.
13. Hassall, C.H., Organic Reactions, Cope, A.C., Ed., New
York: Wiley, 1957, vol. 9, p. 73.
14. Connolly, J.D. and Overton, K.H., J. Chem. Soc., 1961,
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