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DOI: 10.1055/s-2006-951483
An Easy and Straightforward Oxidative Rearrangement of 1,2-Dialkoxy-Substituted Olefins
Publication History
Publication Date:
22 September 2006 (online)
Abstract
1,2-Dialkoxy-substituted olefins, easily available from dihydropyranylcarbene complexes, evolve under mild oxidative conditions to form new functionalized compounds through an oxidative rearrangement process. Depending on the substitution of the starting material, different rearranged final products including cyclopentanone, cyclopentenone, spiroketal and polycyclic derivatives are easily available.
Key words
alkenes - bicyclic compounds - oxidation - oxygen - rearrangements
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References and Notes
Crystal structure data for 6a: C14H20O5, M r = 268.30, colourless prisms, crystal dimensions 0.42 × 0.18 × 0.15 mm, orthorhombic, space group P212121, a = 8.7070 (2), b = 11.3890 (2), c = 13.5920 (3) Å, V = 1347.84 (5) Å3, λ = 1.5418 Å, Z = 4, ρ calcd = 1.322 mg m-3, F(000) = 576, µ(Cu Kα) = 0.828 mm-1. The crystal was held at 200(2) K with an Oxford Cryosystems Cryostream Cooler. Data collection was performed on a Nonius Kappa CCD single-crystal diffractometer. A total of 13256 reflections were measured (θ max = 69.39°; -10 £ h £ 10, 0 £ k £ 13, 0 £ l £ 16). Multiple observations were averaged (R int = 0.0234) resulting in 1470 unique reflections, of which 1382 were observed with I > 2£ (I). The final cycle of full-matrix least-squares refinement based on 1470 reflections and 177 parameters converged to a final value of R1 (observed) = 0.0500, R1 (all data) = 0.0553, wR2 (all data) = 0.1476, S = 1.147. Final difference Fourier maps showed no peaks higher than 0.309 e Å-3 nor deeper than -0.285 e Å-3.
4The crystal structure has been deposited at the Cambridge Crystallographic Data Center and allocated the deposition number CCDC 609926. The data can be obtained free of charge via www.ccdc.cam.ac.uk/products/csd/request/
5O 2 Oxidation: A solution of compound 3 or diast-3 (0.4 mmol) in toluene (10 mL) was saturated by a stream of O2 for 15 min. After stirring for 1 h at r.t., solvents were removed and the resulting residue was purified by silica gel flash column chromatography (hexanes-EtOAc, 20:1 → 5:1) to give pure compounds 6 or 8.
6MCPBA Oxidation: NaHCO3 (0.4 mmol) was added to a solution of compound 3, diast-3, 4, or 5 (0.4 mmol) in CH2Cl2 (10 mL). A solution of MCPBA (0.4 mmol) in CH2Cl2 (10 mL) was then added dropwise to the reaction mixture. After 5 min, silica gel (2 g) was added, the solvents were removed and the residue was purified by flash silica gel column chromatography (hexanes-EtOAc, 20:1 → 5:1) to give pure compounds 6, 8, 11, or 14, respectively.
7(4a S * ,5 S * ,7a S * )-5-(5,6-Dihydro-4 H -pyran-2-yl)-5-hydroxy-7a-methoxy-hexahydrocyclopenta[b]pyran-7- (7a H )-one (6a): White crystals, mp = 146-148 °C; R f = 0.32 (hexane-EtOAc, 2:1); 1H NMR (300 MHz, C6D6): δ = 5.06 (t, J = 3.8 Hz, 1 H, CH=C), 3.72 (s, 3 H, OMe), 3.64-3.59 (m, 4 H, 2 × CH2O), 3.03 (dd, J = 18.1, 1.6 Hz, 1 H, CHHCOH), 2.57 (dd, J = 7.7, 1.5 Hz, 1 H, CH), 2.28 (d, J = 18.1 Hz, 1 H, CHHCOH), 2.10-1.10 (m, 9 H, 2 × CH 2CH 2CH2O and OH); 13C NMR (75.5 MHz, C6D6): δ = 208.6, 152.9, 96.6, 96.2, 76.9, 66.1, 60.5, 49.9, 49.5, 43.7, 22.2, 21.1, 19.9, 17.1; HRMS: m/z [M]+ calcd for C14H20O5: 268.1311; found: 268.1320; Anal. Calcd for C14H20O5: C, 62.67; H, 7.51. Found: C 62.78; H 7.59.
8Formation of a peroxy hemiacetal or a dioxetane derivative could also be considered.
115-Hydroxy-5-isobutyl-3,4,5,6-tetrahydrocyclo-penta[b]pyran-7-(2 H )-one (8a): Syrup, R f = 0.34 (hexanes-EtOAc, 5:1); 1H NMR (300 MHz, C6D6): δ = 4.16 (dt, J = 11.4, 5.4 Hz, 1 H, CHHO), 4.05 (ddd, J = 11.4, 5.7, 5.4 Hz, 1 H, CHHO), 3.12 (br s, 1 H, OH), 2.69 and 2.43 (2 × d, J = 18.6 Hz, 2 H, CH 2COH), 2.44 and 2.31 (2 × dt, J = 18.8, 6.6 Hz, 2 H, CH 2CH2CH2O), 2.00-1.92 (m, 2 H, CH2CH 2CH2O), 1.82 (dd, J = 13.7, 5.4 Hz, 1 H, CHHCH), 1.67 (app nonet, J = 6.6 Hz, 1 H, CH), 1.53 (dd, J = 13.7, 6.3 Hz, 1 H, CHHCH), 0.99 (d, J = 6.6 Hz, 6 H, Me), 0.93 (d, J = 6.6 Hz, 6 H, Me); 13C NMR (75.5 MHz, C6D6): δ = 197.7, 150.6, 146.5, 75.6, 66.9, 48.0, 46.8, 25.0, 24.4, 24.0, 21.1, 18.6; HRMS: m/z [M - H2O]+ calcd for C12H16O2: 192.1145; found: 192.1148.
132-Isobutyl-1,6-dioxaspiro[4.5]-2-decen-4-one (11a): Syrup, R f = 0.41 (hexanes-EtOAc, 5:1); 1H NMR (300 MHz, CDCl3): δ = 5.39 (s, 1 H, C=CH), 3.98-3.93 (m, 2 H, CH2O), 2.39 (d, J = 7.0 Hz, 2 H, CH 2CH), 2.04 (app nonet, J = 6.8 Hz, 1 H, CH), 1.87-1.52 (m, 6 H, CH 2CH 2CH 2CH2O), 1.00 (d, J = 6.6 Hz, 3 H, Me), 0.98 (d, J = 6.8 Hz, 3 H, Me); 13C NMR (75.5 MHz, CDCl3): δ = 200.3, 192.0, 104.4, 101.7, 64.7, 39.9, 28.8, 26.5, 23.9, 22.2, 18.4; HRMS: m/z [M - CO]+ calcd for C11H18O2: 182.1307; found: 182.1302.
147,9-Diphenyl-2,8,12-trioxatricyclo[7.2.1.0 ¹,6 ]-11-dodecanone (14a): White crystals, mp 128-130 °C; R f = 0.32 (hexane-ethyl acetate, 5:1); 1H NMR (300 MHz, CDCl3) δ = 7.77-7.26 (m, 10 H, ArH), 5.32 (d, J = 4.3 Hz, 1 H, CHO), 4.08-4.00 (m, 2 H, CH2O), 3.06 and 2.96 (2 × d, J = 18.9 Hz, 2 H, CH2CO), 2.09 (qt, J = 12.5, 4.3 Hz, 1 H, CHCHO), 1.87 (qd, J = 12.5, 4.2 Hz, 1 H, CHHCH), 1.71-0.85 (m, 3 H, CH 2CHHCH); 13C NMR (75.5 MHz, CDCl3) δ = 207.9, 160.1, 137.5, 128.4, 128.3, 127.7, 126.6, 125.7, 113.8, 102.1, 101.5, 74.2, 64.7, 46.5, 41.8, 24.3, 17.9; HRMS: m/z [M]+ calcd for C21H20O4: 336.1362; found: 336.1360.