Hydrochloric Acid → diethyl (Z)-4-(t-butyldimethylsilyloxy)but-1-enylphosphonate

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To a solution of n-butyllithium in hexane (38.9 ml, 2.7M, 105 mmol) stirred at -20° C. under dry nitrogen was added a solution of diisopropylamine (11.5 g, 114 mmol) in dry THF (70 ml). The solution was cooled to -70° C. before a solution of diethyl methylphosphonate (7.6 g, 50 mmol) in dry THF (10 ml) was added dropwise. A solution of chlorotrimethylsilane (5.8 g, 53 mmol) in dry THF (15 ml) was then added dropwise, maintaining the internal temperature below -60° C. The resulting solution was stirred at -70° C. for 15 min. then warmed to -20° C. before a solution of 3-(t-butyldimethylsilyloxy)propanal (approx. 46 mmol) in dry THF (10 ml) was added dropwise. The solution was then stirred at room temperature for 1.5 hr. The reaction mixture was neutralized by addition of 2M hydrochloric acid and extracted with ether (250 ml). The organic phase was dried (magnesium sulphate), filtered and the solvent removed. The residual oil was purified by column chromatography on silica gel eluting with hexane-acetone (5:1, 3:1) to afford diethyl (Z)-4-(t-butyldimethylsilyloxy)but-1-enylphosphonate as a colourless liquid (1.5 g, 9%); νmax (film) 2940, 1625, 1390, 1245, 1095, 1055, 1030 and 950 cm-1 ; δH (CDCl3) 0.05 (6H, s, SiCH3), 0.87 (9H, s, C(CH3)3), 1.30 (6H, t, J 7 Hz, CH3), 2.83 (2H, m, CH2), 3.73 (2H, t, J 7 Hz, CH2OSi), 4.10 (4H, qu, J 7 Hz, CH2O ), 5.70 (1H, dd, J 14 Hz and 20 Hz, PCH=CH), 6.70 (1H, ddt, J 7 Hz, 14 Hz and 54 Hz, PCH=CH) (Found: MH+ 323.1808. C14

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