1810
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 10, October, 2002
Ogibin et al.
МCPBA (Aldrich) were used. A solution of 90% Н2О2 was
prepared by concentrating a 37% aqueous solution of Н2О2 in a
vacuum desiccator above Р2О5 at 20 °С for 5 days. The concenꢀ
tration of Н2О2 was determined by iodometric titration.
We have previously10,13 described the synthesis of initial
2ꢀ(3ꢀacetoxypropyl)cycloalkanones 1а—d, oxabicycloalkenes
2a—d, and 1ꢀhydroperoxyꢀ2ꢀoxabicyclo[4.4.0]decane (3b).
Synthesis of nꢀacyloxyalkanoꢀnꢀlactones 4а—d and 5a—d
from oxacycloalkenes 2a—d (general procedures) (molar ratios
of reactants, particular conditions of experiments, and yields of
lactones are presented in Table 1). А. An aqueous solution of
Н2О2 containing a catalytic amount of H2SO4 was added
dropwise for 5—10 min to a vigorously stirred and cooled to
0—5 °С solution of oxabicycloalkene 2 (5—10 mmol) in a lowest
alkanoic acid (5—10 mL). The reaction mixture was stirred at
this temperature until 2 completely converted (30—120 min)
(TLC monitoring) and then heated at 40—60 °С for 20—45 min.
Then the mixture was diluted with water (15 mL) and extracted
with Et2O (2×30 mL). The organic layer was neutralized with
solid Na2CO3 (3 g), filtered, and concentrated by evaporation.
The residue was distilled in vacuo (10—30 Torr) using a
Hickmann flask (this distillation results in the thermal depolyꢀ
merization of lactone oligomers, which can be formed under the
reaction conditions), and the distillate was purified by flash
chromatography if necessary.
Thus, unlike the Baeyer—Villiger reaction, the new
method proposed for the synthesis of nꢀsubstituted lacꢀ
tones allows their regiospecific formation from 2ꢀacetoxyꢀ
propylꢀsubstituted cycloalkanones through the successive
transformation of these substrates into 2ꢀoxabicycloꢀ
alkenes and 1ꢀhydroperoxyꢀ2ꢀoxabicycloalkenes. The disꢀ
tinction between the results of these two processes is
caused by the different structures of the key intermediates
that formed, which are conventionally called the "Criegee
intermediates." 5 We have shown10 that, in the case of the
synthesis of lactones through oxabicycloalkenes and hyꢀ
droperoxides, bicyclic peroxy ethers В are such intermeꢀ
diates (Scheme 9), whereas for the Baeyer—Villiger oxiꢀ
dation of ketones, these are monocyclic peroxy ethers А 5
(Scheme 8), whose rearrangement is less selective. The
latter is due, most likely, to a less rigid structure А with
respect to that of bicyclic peroxy ethers В and the subꢀ
stantial influence of the electronic, conformational, and
steric factors on the regioselectivity in the Baeyer—Villiger
reaction.11,12
Scheme 9
В. A solution of oxabicycloalkene 2 (5—10 mmol) in a lowꢀ
est alkanoic acid (5—10 mL) was added dropwise (for 5—10 min)
to an aqueous solution of Н2О2, which was vigorously stirred
and cooled to 0—5 °С and contained a catalytic amount of
H2SO4. The reaction mixture was stirred for this temperature
until compound 2 converted completely (40—60 min) (TLC
monitoring) and then heated at 40—50 °С for 40—45 min. For
the further treatment of the mixture, see procedure А.
С. An aqueous solution of Н2О2 containing a catalytic
amount of H2SO4 was added dropwise (10 min) at ∼20 °C to a
vigorously stirred solution of oxabicycloalkene 2 (5 mmol) in a
lowest alkanoic acid (5 mL). The reaction mixture was stirred to
the complete conversion of 2 (40 min) (TLC monitoring) and
heated at 40 °С for 30 min. Then the mixture was treated simiꢀ
larly to the treatment described in procedure А.
The physical properties and spectra of synthesized nꢀ(3ꢀforꢀ
myloxypropyl)alkanoꢀnꢀlactones (4а—d) and nꢀ(3ꢀacetoxyꢀ
propyl)alkanoꢀnꢀlactones (5а—d) were identical to those of lacꢀ
tones synthesized from hydroperoxides 3а—d.10 6ꢀOxononanoꢀ
9ꢀlactone (6) was similar in physical and spectroscopic properꢀ
ties to the ketolactone synthesized by the reaction of 2ꢀoxaꢀ
bicyclo[4.4.0]decꢀ1(6)ꢀene (2b) with MCPBA.7,8
Experimental
NMR spectra were recorded on Bruker WMꢀ250
(250.13 MHz for Н) and Bruker AМꢀ300 (75.4 MHz for 13С)
1
spectrometers in solutions of СDCl3. IR spectra were recorded
on a URꢀ20 spectrometer (Carl Zeiss, Jena). Mass spectra were
obtained on a Varian MATꢀ311A instrument (EI, 70 eV). GLC
analysis was carried out on Varianꢀ3700 (a flameꢀionization
detector, a glass column 2000×3 mm, 5% Carbowax 20M on
Inerton) and LKhMꢀ80 chromatographs (a flameꢀionization
detector, a steel column 1000×4 mm, 5% XEꢀ60 on Chromaton
NꢀAW). TLC analysis was performed using Silufol UVꢀ254 chroꢀ
matographic plates. Neutral Al2O3 and a diethyl ether—petroꢀ
leum ether mixture (30—70% Et2O) was used as the eluent in
flash chromatography.
2ꢀ(3ꢀPropionyloxypropyl)cyclohexanone (8) was isolated by
distillation of the residue obtained in entry 25. B.p. 170—173 °С
(30 Torr). IR (KBr), ν/cm–1: 1707 (C=O), 1736 (O—C=O).
1Н NMR, δ: 1.10—1.64 (m, 11 H, СН2, СН3); 1.88—2.12 (m,
5 Н, СН2, СН); 2.63 (q, 2 Н, СН2С=О, J = 2.3 Hz); 3.93 (t,
2 Н, CH2О, J = 4.0 Hz). Found (%): С, 67.71; Н, 9.72.
С12Н20O3. Calculated (%): С, 67.89; Н, 9.50.
Di(1ꢀoxadecahydronaphthalenꢀ8aꢀyl) peroxide (9) was isoꢀ
lated by flash chromatography of the residue obtained in entry
22. Rf 0.2 (Et2O—petroleum ether, 1 : 1), oil manifesting a posiꢀ
tive for peroxide reaction with an acidifed solution of KI.
IR (NaCl), ν/cm–1: 864 (O—O). 1Н NMR, δ: 1.10—1.80 (m,
26 Н, СН2, CH); 3.55—4.31 (m, 4 Н, СН2О). 13С NMR, δ: 22.5,
24.6, 25.6, 26.0, 29.2 (CH2); 32.0 (CH); 43.5 (CH2—C—O);
A commercial 50% aqueous solution of Н2О2 (Acros Organꢀ
ics); acetic, formic, and propionic acids; 96% Н2SO4 (Reakhim);
trifluoroacetic acid (Lancaster); propionic anhydride and
Ogibin
