4-Methylbenzaldehyde → Lithium Hexamethyldisilazide

Participants

Reaction Conditions

Reaction Steps

A solution of lithium bis(trimethylsilyl)amide was prepared by adding 2.5M n-butyl lithium (208 mL) to a solution of 1,1,1,3,3,3-hexamethyldisilazane (110 mL, 0.52 mol) in tetrahydrofuran (THF) (140 mL) at 0° C. After stirring for 15 min, this solution was added via a cannula to a solution of p-tolualdehyde (59 mL, 0.5 mol) in THF (100 mL), while keeping the temperature between -40° and -50° C. The reaction mixture was then allowed to warm to 10° C. over 30 min. A 2M solution of allyl magnesium chloride (260 mL) in THF was added, keeping the temperature between 10° and 15° C. After stirring for 30 min the reaction was poured into a solution of ammonium chloride (150 gm) in water (1 L). The layers were separated and the aqueous layer was extracted with ether/hexane. The organic layers were washed with brine, combined, dried over sodium sulfate and evaporated. The residue was added to a solution of (1R)-(-)-10-camphorsulfonic acid (62.5 gm) in ethyl acetate (1 L) with cooling. On standing overnight at rt, crystals formed which were filtered and washed with ethyl acetate. The crystals were then stirred with refluxing ethyl acetate (300 mL), filtered and washed with ethyl acetate. The pure title compound weighed 60.7 gm. [α]D =-27.16 (c=0.5, 100% EtOH).

Provenance & Evidence