Reaction Steps
A solution of isopropyl (3-hydroxycyclopentenyl)methylphosphinate (3) (3.5 g, 17.2 mmol) in anhydrous DMF (60 cm3) was treated with t-butyldimethylsilyl chloride (2.85 g, 18.9 mmol), triethylamine (3.6 g, 34.3 mmol) and DMAP (250 mg). The reaction mixture was stirred at room temperature for 16 h, after which time the solvent was removed in vacuo. The residue was partitioned between DCM (50 cm3) and water (30 cm3) and the aqueous layer was further extracted with DCM (3×20 cm3). The combined organic layers were washed with water (2×30 cm3) and brine (40 cm3), dried over anhydrous Na2SO4, filtered and the solvent removed under reduced pressure. The crude product was purified by short column vacuum chromatography on silica gel (5% ethanol/ethyl acetate) to yield the title compound (4) as a colourless oil (4.62 g, 85%): 1H NMR (300 MHz, CDCl3) δ 0.065 and 0.067 (6H, 2×s), 0.870 and 0.874 (9H, 2×s), 1.22 and 1.24 (3H, 2×d, J=6.3 and 6.3 Hz, OCHCH3), 1.31 and 1.33 (3H, 2×d, J=6.0 and 6.0 Hz, OCHCH3), 1.45 and 1.49 (3H, 2×d, J=14.4 and 14.4 Hz, PCH3), 1.69-1.83 (1H, m, C(5)—H), 2.24-2.46 (2H, m, C(5)—H′ and C(4)—H), 2.54-2.68 (1H, m, C(4)—H′), 4.55 (1H, m, OCHCH3), 4.95 (1H, m, C(3)—H), 6.46 (1H, m, C(2)—H), 13 C NMR (75.46 MHz, CDCl3) δ −4.81 and −4.75 (Si(CH3)2, 2×s), 14.0 and 14.19 (PCH3, d, JPC=101.3 and 101.8 Hz), 18.07 and 18.10 (SiC(CH3)3, 2×s), 23.90 and 23.96 (POCCH3, 2×d, 3JPOCC=4.8 Hz), 24.43 (POCCH3, overlapping d, 3JPOCC=3.3 Hz), 25.76 (SiC(CH3)3, br. s), 31.34 (C(4), d, 3JPC=11.5 Hz), 34.42 and 34.55 (C(5), 2×d, 2JPC=9.5 Hz), 68.95 and 68.99 (POCHCH3, d, 2JPOC=6.5 and 5.9 Hz), 77.98 and 78.24 (C(3), d, 3JPC=6.9 and 6.7 Hz), 137.78 and 138.08 (C(2), d, JPC=125.0 and 125.6 Hz), 147.2 (C(1), d, J=10.7 Hz), 31P NMR (121 MHz, CDCl3) δ 38.1, 38.5, (ESI) 319.1869 (MH+-C15H32O3PSi requires 319.1858).
