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(C1), 108.86 (=CH2), 123.59 (C3), 135.84 (C2), 148.69
(=C=).
(2S,5R)-5-Acetyl-2-iodomethyl-2-methyl-
dihydrofuran-3-ylidenehydroxyacetaldehyde (VII).
Through a solution of 0.75 g (2.6 mmol) of ketone IV in
20 ml of MeOH was passed O3 at –78OC. When the
solution turned blue it was flushed with argon, 1 ml of
Me2S was added, the mixture was warmed to room
temperature and stirred for 3 h. Then the solvent was
distilled off, the residue was dissolved in 20 ml of EtOAc,
3 g of SiO2 was added, and the mixture was stirred for 6
h. Afterwards the solution was filtered, evaporated, and
the residue was subjected to column chromatography on
SiO2 (EtOAc–petroleum ether, 2:1). Yield 0.82 g (98%),
viscous light-yellow fluid, [α]D20 +57.3° (C 2.0, CHCl3).
IR spectrum, ν, cm–1: 3412 (OH), 1716, 1658 (2C=O).
1H NMR spectrum, δ, ppm: 1.64 s (3H, CH3), 2.43 s
(3H, CH3), 2.99–3.08 m (1H, H4), 3.27–3.35 m (1H, H4),
3.56 d (1H, CH2I, J 9 Hz), 3.93 d (1H, CH2I, J 9 Hz),
4.45–4.51 m (1H, H5), 6.04 br.s (1H, OH), 9.60 s (1H,
CHO). 13C NMR spectrum, δ, ppm: 13.40 (CH2I), 21.49
(CH3), 26.58 (CH3), 30.96 (C4), 81.71 (C5), 85.46 (C2),
136.44 (C3), 140.84 (=C=), 185.20 (CHO), 208.39 (C=O).
Mass spectrum (ACPI), m/z (Irel, %): 197 ([M –HI +
H]+, 127I) (100), 325 ([M + H]+, 127I) (1.25).
To a solution of 0.5 g (3.3 mmol) of (–)-carveol in
20 ml of acetonitrile at 0°C while stirring was added in
one portion 0.55 g (6.6 mmol) of NaHCO3. The mixture
was stirred for 15 min, then 0.84 g (3.3 mmol) of crystalline
I2 was added. The reaction mixture was stirred for 2 h at
room temperature till the disappearance of the initial
compound (TLC monitoring), the solution was evaporated,
and 15 ml of saturated solution of Na2S2O3 was added,
the reaction products were extracted with EtOAc (3 ×
10 ml). The combined organic solutions were dried with
MgSO4 and evaporated, the residue was subjected to
column chromatography on SiO2 (EtOAc–petroleum
ether, 1:10). Yield of compound II 0.66 g (73%). Light
yellow fluid, [α]D20 –17.5° (C 5.0, EtOH). IR spectrum,
ν, cm–1: 1088 (C–O–C). 1H NMR spectrum, δ, ppm:
1.45 s (3H, CH3), 1.70–1.72 m (3H, CH3), 1.91–1.95 m
(1H, H8), 2.23–2.38 m (3H, H4,5,8), 2.49–2.50 m (1H,
H4), 3.30 d (1H, CH2I, J 9 Hz), 3.37 d (1H, CH2I,
J 9 Hz), 4.13–4.15 m (1H, H1), 5.25–5.27 m (1H, H3).
13C NMR spectrum, δ, ppm: 14.22 (CH2I), 21.41 (CH3),
27.94 (CH3), 29.76 (C4), 35.10 (C8), 40.77 (C5), 77.53
(C1), 84.03 (C6), 120.72 (C3), 139.80 (C2).
(2S,5R)-5-Acetyl-2-iodomethyl-2-methyl-
dihydrofuran-3-one (VIII). Through a solution of 0.6 g
(1.86 mmol) of enol VII in 20 ml of MeOH was passed
O3 at –40°C to the ratio 3 mmol of O3 per 1 mmol of the
substrate. Then the reaction mixture was flushed with
argon, Me2S was added, the mixture was warmed to room
temperature, acidified with 10N water solution of HCl,
and stirred for 6 h.The solvent was distilled off, and the
residue was subjected to column chromatography on SiO2
(EtOAc–petroleum ether, 2:1). Yield 0.31 g (60%), light-
yellow fluid, [α]D20 +105.5° (C 2.35, CH2Cl2). IR
(1R,5R,6S)-6-Iodomethyl-2,6-dimethyl-7-
oxabicyclo[3.2.1]oct-2-ene-4-one (IV). To a solution
of 5.4 g (54.0 mmol) of CrO3 in 40 ml CH2Cl2 at –20°C
was added in one portion at stirring 5.2 g (54.0 mmol) of
1,5-dimethylpyrazole. The mixture was stirred for 15 min,
then 1 g (3.6 mmol) of compound II was added. The
reaction mixture was stirred for 4 h at –15°C, 20 ml of
20% aqueous NaOH was added, and the stirring was
continued for 1 h at 0°C. The organic layer was separated,
washed with 50% HCl solution for removing 1,5-di-
methylpyrazole, then with brine, dried with MgSO4, and
evaporated. The residue was subjected to column
chromatography on SiO2 (CHCl3–MeOH, 40:1). Yield
0.68 g (65%), light-yellow fluid. [α]D20 +350.3° (C 4.0,
1
spectrum, ν, cm–1: 1761, 1716 (2C=O). H NMR
spectrum, δ, ppm: 1.39 s (3H, CH3), 2.45 s (3H, CH3),
2.72–2.75 m (2H, H4), 3.26 d (1H, CH2I, J 9 Hz), 3.35 d
(1H, CH2I, J 9 Hz), 4.60–4.65 m (1H, H5). 13C NMR
spectrum, δ, ppm: 9.35 (CH2I), 20.86 (CH3), 26.47 (CH3),
37.49 (C4), 77.65 (C5), 82.39 (C2), 208.60 (2C=O).
1
CHCl3). IR spectrum, ν, cm–1: 1676 (C=O). H NMR
spectrum, δ, ppm: 1.55 s (3H, CH3), 2.08 s (3H, CH3),
2.36 d (1H, H8, J 12 Hz), 2.46–2.50 m (1H, H8), 3.10 m
(1H, H5), 3.12 d (1H, CH2I, J 9 Hz), 3.22 d (1H, CH2I,
J 9 Hz), 4.47–4.49 m (1H, H1), 5.78–5.79 m (1H, H3).
13C NMR spectrum, δ, ppm: 13.71 (CH2I), 22.16 (CH3),
28.23 (CH3), 39.96 (C8), 58.44 (C5), 78.27 (C1), 81.39
(C6), 125.70 (C3), 165.39 (C2), 199.02 (C=O). Mass
spectrum (ACPI), m/z (Irel, %): 293 ([M + H]+, 127I) (100),
165 ([M – HI + H]+, 127I) (42.4).
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3. Wang, J. and Herdewijn, P., J. Org. Chem., 1999, vol. 64,
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4. Srikrishna, A. and Vijaykumar, D., J. Chem. Soc., Perkin
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 5 2010