Diisopropylamine → Lithium diisopropylamide

Participants

Reaction Steps

A solution of lithium diisopropylamide was prepared using n-butyllithium (20 ml of a 2.5M solution in hexane) and diisopropylamine (5.06 g) in dry tetrahydrofuran (100 ml) under an atmosphere of dry nitrogen as described in Example 1(i). To this solution at -70° was added 2-methylpyrazine (4.70 g) and the purple solution resulting was stirred at -70° for 0.5 hour. A solution of methyl 2,4-difluorobenzoate (8.60 g) in dry tetrahydrofuran (75 ml) was added over 0.5 hour and stirring was continued at -70° for a further 0.5 hour. Acetic acid (10 ml) was added and the temperature was allowed to rise to room temperature. The solution was diluted with water and the pH was adjusted to 7 with sodium bicarbonate. The mixture was extracted three times with ethyl acetate and the combined organic extracts were washed with water and dried (Na2SO4). The solvent was evaporated and the residue was chromatographed on silica gel. Elution with ethyl acetate/hexane (3:7) gave, after combination and evaporation of appropriate fractions, a solid which was crystallised from hexane to give the title compound, (5.90 g), m.p. 107°-108°.

Provenance & Evidence