Tetrahydropyran Diene (preparation recently submitted)

Grubbs’ 2^nd generation catalyst (Sigma Aldrich)

dichloromethane (ultra low water, J.T. Baker)

Into a 100 mL round bottom flask under nitrogen atmosphere was added the diene (0.049 g, 0.15 mmol) in dry DCM (30 mL). Grubbs’ 2^nd generation catalyst (0.010 g, 0.01 mmol) was added as a solid to the solution. The flask was fitted with a reflux condenser (still under nitrogen) and then put on an oil bath; the solution stirred 12 h at reflux. After, the mixture was allowed to cool to room temperature and the solvent was removed under reduced pressure. The residue was purified by silica gel flash chromatography using 7:3 hexanes:ethyl acetate as eluent to yield 0.027 g (60%) of the spirocyclic product as a clear, colorless oil.

R_f 0.59 (7:3 Hex:EtOAc); [α]_D -50.3184 (c 1.06, CH₂Cl₂); ¹H NMR (400 MHz, CDCl₃) δ 7.61 (d, J = 7.5 Hz, 2H), 7.30 (t, J = 7.5 Hz, 2H), 7.16 (t, J = 7.3 Hz, 1H), 6.24 (d, J = 6.2 Hz, 1H), 5.87 (ddd, J = 2.4, 6.1 Hz, 1H), 5.60 (s, 1H), 4.85 (t, J = 1.7 Hz, 2H), 4.58 (ddd, J = 6.6 Hz, 1H), 4.43 – 4.34 (m, 2H), 4.28 (d, J = 7.9 Hz, 1H), 1.54 (s, 3H), 1.41 (s, 3H); ¹³C NMR (100 MHz, CDCl₃) δ 151.8, 135.8, 131.0, 128.7, 128.3, 127.4, 126.1, 110.9, 105.0, 89.9, 77.1, 76.4, 71.7, 66.6, 26.7, 25.4; TOF HRMS (DART) m/z (M+H)⁺ calcd for C₁₈O₄H₂₁ 301.1440, found 301.1448.