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11
General Experimental Procedure
A mixture of Baylis-Hillman adduct (1 mmol), DMP (1.2 mmol), and pyridine (1.5 mmol) in anhyd CH2Cl2 (10 mL) was stirred at r.t. until complete oxidation took place. To this, trimethylsilyl enol ether (1.5 mmol) was added and stirred until complete addition (as indicated by TLC) took place. The reaction mixture was diluted with H2O (50 mL) and extracted with Et2O (3 × 15 mL). The combined ether layer was washed with sat. aq NaHCO3 soln (1 × 15 mL), brine (1 × 10 mL), dried over Na2SO4, and evaporated. The crude product was purified by silica gel column chromatography using a gradient mixture of hexane-EtOAc (9:1) as eluent to afford pure substituted dihydropyran derivatives.
Spectral Data of Selected Compounds
Compound 3a (Table
[1]
): colorless liquid. IR (KBr): νmax = 2954, 2838, 1738, 1454, 1234, 1207, 1153, 1017, 781 cm-1. 1H NMR (200 MHz, CDCl3): δ = 0.0 (s, 9 H), 1.20-1.58 (m, 8 H), 1.61-1.76 (m, 1 H), 2.06 (dd, 1 H, J = 1.4, 16.4 Hz), 2.56 (dd, 1 H, J = 5.8, 16.8 Hz), 3.32 (s, 3 H), 7.14-7.18 (m, 5 H). ESI-MS: m/z = 361 [M + 1], 383 [M + Na]. HRMS:
m/z calcd for C20H28O4NaSi: 383.1654; found: 383.1641.
Compound 3b (Table
[1]
): 1H NMR (600 MHz, CDCl3): δ = 7.33 (m, 5 H, Ph), 3.92 (q, 2 H, J = 7.2 Hz, OCH2), 2.72 (dd, 1 H, J = 16.7, 6.2 Hz, H6), 2.23 (dd, 1 H, J = 16.7, 2.0 Hz, H6′), 2.12 (dt, 1 H, J = 13.0, ca. 3.6 Hz, H1e), 1.85 (dddd, 1 H, J = 10.5, 6.2, 4.2, 2.0 Hz, H5a), 1.65 (m, 1 H, H3e), 1.62 (m, 1 H, H2e), 1.57 (m, 1 H, H4e), 1.55 (dt, 1 H, J = 3.8, ca. 12.8 Hz, H1a), 1.44 (tq, 1 H, J = ca. 3.5, ca. 12.6 Hz, H2a), 1.34 (dq, 1 H, J = 3.2, ca. 12.3 Hz, H4a), 1.28 (m, 1 H, H3a). 0.91 (t, J = 7.2 Hz, 1 H, CH3), 0.15 (s, 9 H, 3 × CH3).
Compound 3f (Table
[1]
): colorless liquid. IR (KBr): νmax = 3029, 2948, 2865, 1718, 1495, 1265, 1217, 1137, 1037, 854 cm-1. 1H NMR (300 MHz, CDCl3): δ = 0.0 (s, 9 H), 1.80 (ddd, 1 H, J = 1.8, 5.6, 13.4 Hz), 2.21 (ddd, 1 H, J = 3.5, 5.4, 13.4 Hz), 2.52 (ddd, 1 H, J = 3.5, 5.6, 16.9 Hz), 2.66 (ddd, 1 H, J = 5.4, 11.3, 16.8 Hz), 3.59 (s, 3 H), 7.07-7.13 (m, 5 H), 7.22 (td, 1 H, J = 1.1, 7.9 Hz), 7.3-7.43 (m, 6 H), 7.50 (dd, 2 H, J = 1.5, 7.7 Hz). HRMS: m/z calcd for C28H31O5Si: 475.1940; found: 475.1954.
Compound 3h (Table
[1]
): colorless liquid. IR (KBr): νmax = 2928, 2857, 1715, 1504, 1433, 1151, 1039, 754 cm-1. 1H NMR (300 MHz, CDCl3): δ = 0.0 (s, 9 H), 0.78 (t, 3 H, J = 6.8 Hz), 1.10-1.27 (m, 6 H), 1.33-1.72 (m, 6 H), 1.86-2.02 (m, 1 H), 2.07 (dd, 1 H, J = 6.0, 12.0 Hz), 2.16 (dd, 1 H, J = 6.0, 12.0 Hz), 3.55 (s, 3 H).
Compound 4 (Scheme
[2]
): colorless liquid. IR (KBr): νmax = 2920, 2851, 1739, 1683, 1506, 1443, 1226, 1157, 1019, 755 cm-1. 1H NMR (300 MHz, CDCl3): δ = 2.20-2.39 (m, 2 H), 2.94-3.19 (m, 2 H), 3.61 (s, 3 H), 4.67 (dd, 1 H, J = 6.0, 7.5 Hz), 7.33-7.52 (m, 5 H), 7.87 (d, 2 H, J = 7.5 Hz), 7.99 (d, 2 H, J = 9.0 Hz). ESI-MS: m/z = 345 [M + 1], 367 [M + Na]. HRMS: m/z calcd for C19H17O4NaCl: 367.0713; found: 367.0715.
12
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