Reaction Steps
To a solution of DABCO (11.8 g, 105 mmol) and 3-iodo-cyclopent-2-enol (5.5 g, 26.3 mmol) in anhydrous toluene (300 cm3) was added trimethylsilyl chloride (3 g, 27.6 mmol). The reaction mixture was stirred at room temperature for 15 min, after which time isopropyl methylphosphinate (4.8 g, 39.4 mmol) and tetrakis(triphenylphosphine)palladium(0) (760 mg, 2.5 mol %) were added. The reaction mixture was heated at 70° C. for 24 h after which time a second portion of tetrakis(triphenylphosphine)palladium(0) (760 mg, 2.5 mol %) was added and heating continued for a further 24 h. The reaction mixture was filtered while still hot and aqueous ethanol (50 cm3) added to the filtrate, which was then concentrated in vacuo. The product was isolated by short column vacuum chromatography on silica gel (15% ethanol/ethyl acetate) to yield the title compound (3) as a slightly coloured oil (3.5 g, 65%): 1H NMR (300 MHz, CDCl3) δ 1.25 (3H, t, J=6.4, OCHCH3), 1.327 and 1.333 (3H, 2×d, J=6.2 and 6.2 Hz, OCHCH3), 1.49 and 1.51 (3H, 2×d, J=14.4 and 14.4 Hz, PCH3), 1.76-1.92 (1H, m, C(5)—H), 2.33-2.52 (2H, m, C(5)—H′ and C(4)—H), 2.60-2.78 (1H, m, C(4)—H′), 4.55 (1H, m, OCHCH3), 4.95 (1H, m, C(3)—H), 6.57 (1H, m, C(2)—H); 13C NMR (75.46 MHz, CDCl3) δ 13.8 and 14.0 (PCH3, d, JPC=101 and 101 Hz), 23.88 and 23.91 (POCCH3, d, 3JPOCC=4.9 and 4.6 Hz), 24.31 (POCCH3, overlapping d, 3JPOCC=3.4 Hz) 26.89 and 26.91 (C(4), d, 3JPC=12.8 and 12.5 Hz), 29.27 and 29.35 (C(5), d, 2JPC=8.8 and 8.6 Hz), 76.94 and 73.65 (POCHCH3, d, 2JPOC=6.0 and 6.3 Hz), 76.94 and 77.18 (C(3), d, 3JPC=5.0 and 7.5 Hz), 138.11 and 138.22 (C(1), d, JPC=126 and 126 Hz), 147.54 (C(2), d, J=10.6 Hz), −P NMR (121 MHz, CDCl3) δ 38.9, 39.0, (ESI) 207.1154 (MH+-C9H20O3 requires 207.1150).
