Whitby group

To a stirred solution of zirconocene dichloride (0.29 g, 1.00 mmol, 1 equiv.) in THF (5 mL) was added slowly dropwise n-butyl lithium (2.5 M in hexanes, 0.80 mL, 2.00 mmol, 2 equiv.) at -78 °C.  After 15 minutes, a solution of ((3-(hept-6-en-1-yn-1-yl)benzyl)oxy)triisopropylsilane (0.36 g, 1.00 mmol, 1 equiv.) in THF (3 mL) was added slowly dropwise still at -78 °C.  After 20 minutes at this temperature the reaction was allowed to warm to room temperature and stirred for 2 hours.

A solution of 1,1-dibromoheptane (0.28 g, 1.10 mmol, 1.1 equiv.) was added at -78 °C, followed by addition of LDA (1.8 M solution, 0.64 mL, 1.15 mmol, 1.15 equiv.).  The reaction was stirred for 15 minutes before dropwise addition of the lithium alkyne [prepared from phenyl acetylene (0.31 mL, 3.00 mmol, 3 equiv.) in THF (3 mL) and n-butyl lithium (2.5 M in hexanes, 1.20 mL, 3.00 mmol, 3 equiv.) at -78 °C] still at -78 °C.  The reaction was stirred for 30 minutes before being quenched with methanol (10 mL) and sodium bicarbonate solution (sat. aq., 10 mL).  The reaction was allowed to warm to room temperature and stirred for 16 hours.

The reaction was poured onto water (100 mL) and the product was extracted with diethyl ether (3 x 75 mL).  The diethyl ether layers were combined and washed with water (3 x 75 mL) and brine (75 mL) before being dried over magnesium sulphate, filtered and concentrated under reduced pressure.

The product was purified by column chromatography (silica gel, hexane) to yield the product as a yellow oil (0.48 g, 0.85 mmol, 85%).  The product was used immediately in the next step of the reaction.