Structure of Silyl-Substituted Allenyl/Propargyl- lithium Reagents in Solution**

To a solution of (S)-( -)-l.l'-bi-2-naphthoI (57 mg. 0.20 mmol) in MeCN (0.5 mL) was added TiF, (0.20 mL, 0.10 mmol; 0.5 M solution in MeCN) to give a deep red solution that was stirred for 5 min prior to removing the solvent under reduced pressure. The residue was kept under reduced pressure (1 mm Hg) for 0.5 h and subsequently suspended in CH,CI, (0.5 mL). cooled to O'C. and treated dropwise with allyltrimethylsilane (0.24 mL, 1.5 mmol). After the mixture had been stirred at 0 'C for I .5 h. the resulting red orange solution was treated with 2.2-dimethyI-4-pentenal (0.14 mL. 1 0 mmol). The reaction mixture was stirred at 0 for 4 hand then diluted with Et,O:pentane (1 :2; 10 mL). The mixture was filtered through a plug of silica and the filter cake washed with Et,O/pentane (1 :2; 50 mL). The filtrate was concentrated in V~CUO to an oil. which was diluted with THF (2.0 mL). The resulting solution was treated with Bu,NF (1.0 mL of a 1.0~ solution in THF), and stirred at 23 C for 0.5 h. The reaction was quenched with Et,O (50 mL) and washed with H20 (20 mL). The ether extract was washed with saturated aqueous sodium chloride solution, dried over anhydrous Na,SO,, and concentrated in vacuo to give a colorless oil. Purification by chromatography on silica gel with Et,O/pentane (l/lO) afforded 138 mg (90%) of the product.