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K. Crawford et al.
LETTER
was separated. Repeated washing of the organic phase with
H2O was followed by concentration in vacuo to afford crude 3
(purity 93% (GC), 7.75 g, 94%). Spectral data of 3: 1H NMR
(ppm, CDCl3, 360 MHz) 0.90 (br t, J = 6.7 Hz, 3H); 1.02-
1.17 (m, 1H), 1.20-1.56 (overlapping m, 7H); 1.78-2.68 (m,
7H); 2.11 (s, 3H); 13C NMR (ppm, CDCl3, 90 MHz): 13.9
(CH3), 21.0 (MeCO2), 22.4, 24.5, 26.3, 27.2, 28.2, 31.9, 34.4
(CH2), 36.0 (CH), 51.7 (MeO), 71.2, 91.8 (C), 169.5, 172.9
(CO2); MS (electrospray ionisation): (M+H)+ = 285.
93%9 (GC), 74%), bp 98-109 °C/0.05 Torr, spectra identical
with those reported previously.1
(9) Preparative GC allowed the isolation of (±)-cis-1-pentyl-2-
oxabicyclo[3.3.0]octane-3,8-dione (5, 3%), and 3-methyl-2-
pentylcyclopent-2-en-1-one (dihydrojasmone, 6, 4%), whose
spectra were identical with an authentic sample.11
Spectroscopic data of 5: 1H NMR (360 MHz, CDCl3) 0.88
(br. t, J = 6.7 Hz, 3H); 1.15-1.45 (m, 6H); 1.67-1.87 (m, 3H);
2.14-2.63 (m, 4H); 2.84-2.97 (m, 2H); 13C NMR (90 MHz,
CDCl3) 13.9 (CH3), 22.4, 22.6, 25.0, 31.9, 33.0, 35.7; 35.8
(CH2), 38.6 (CH), 89.0 (C), 175.0 (CO2), 210.9 (CO); MS 210
(M+), 154, 139, 112, 111, 99, 98, 83, 71, 55, 43. Compounds
5 and 6 were also found as by-products during the screening
experiments where their yields were dependent on the nature
of both the acid and solvent used.
Attempted purification of 3 either by distillation or
chromatography led to extensive decomposition. Crude 3 was
therefore employed for transformation to 4.
(6) Fehr C., Angew. Chem. Int. Ed. Engl. 1998, 37, 2407.
(7) Shine, H.J.; Hunt, G.E., J. Am. Chem. Soc. 1954, 80, 2434.
Draper, A.L.; Heilman, W.J.; Schaeffer, W.E.; Shine, H.J.;
Shoolery, J.N., J. Org. Chem. 1962, 27, 2727. Williamson,
K.L.; Coburn, J.I.; Herr, M.F., J. Org Chem. 1967, 32, 3934.
House, H.O. Modern Synthetic Reactions, 2nd ed., W. A.
Benjamin: Menlo Park, 1972, pp 315-317. Jones, A.B. In
Comprehensive Organic Synthesis, Trost, B.M., Ed.
Pergamon: New York, 1999; vol. 7, pp 167-168. Zhu, Y.;
Manske, K.J.; Shi, Y., J. Am. Chem. Soc. 1999, 121, 4080.
Feng, X.; Shu, L.; Shi, Y., J. Am. Chem. Soc. 1999, 121,
11003.
(8) Preparation of methyl 3-oxo-2-pentyl-1-cyclopentene-1-
acetate (4): A solution of crude 3 (ref. 5, 4.10 g, 13.4 mmol) in
MeOH (5 mL) was added dropwise during 1 h to a stirred
solution of MsOH (70 mg) in MeOH (10 mL) at reflux under
N2. After a further 2 h at reflux the mixture was cooled to r.t.
and concentrated in vacuo. The residual oil was dissolved in
cyclohexane (10 mL) and washed with 10% aq NaOAc.
Work-up and fractional distillation afforded 1 (2.40 g, purity
(10) (±)-Methyl t-2-acetoxy-3-oxo-2-pentyl-r-1-cyclopentane-
acetate (7a) was detected at the initial stages of the reaction
and disappeared during the course of the reaction. Isolation of
(±)-trans-7a was effected by work-up at low conversion and
preparative GC. Spectroscopic data of 7a: 1H NMR (360
MHz, CDCl3) 0.88 (br. t, J = 6.7 Hz, CH3); 1.17-1.56 (m,
8H); 1.59-1.74 (m, 1H); 2.04 (s, MeCO2), 2.14-2.69 (m, 5H);
3.29-3.42 (1H, m); 3.70 (s, MeO); 13C NMR (90 MHz, CDCl3)
14.0 (CH3), 20.9 (MeCO2), 21.7, 22.4, 29.9, 32.3, 34.3, 34.6
(CH2), 38.7 (CH), 51.7 (MeO), 85.2 (C), 169.7, 172.2 (CO2),
211.9 (CO); MS 209, 151, 130, 111, 99, 98, 71, 55, 43.
(11) Bellina, F.; Ciuci, D.; Rossi, R.; Vergamini, P., Tetrahedron
1999, 55, 2103.
Article Identifier:
1437-2096,E;2001,0,07,1127,1128,ftx,en;G07001ST.pdf
Synlett 2001, No. 7, 1127–1128 ISSN 0936-5214 © Thieme Stuttgart · New York