Pivaloyl chloride → HCID 59318452, compound

Participants

Reaction Conditions

Reaction Steps

146 mg (3S,5S)-5-biphenyl-4-ylmethyl-3-methylpyrrolidin-2-one (2-b, R1=H) [9:1 diastereoisomer mixture [(2S,4S): (2R,4S)]] is added to 10 ml THF. The mixture is cooled to −78° C. and 381 μl butyllithium (1.59 M in hexane) are added. 81 μl Pivaloyl chloride is then added. After 4 h, the mixture is warmed to room temperature. The mixture is then quenched by the addition of saturated ammonium chloride solution and isopropyl acetate. The phases are separated and the organic phase dried (MgSO4) and then concentrated in vacuo. The residue is purified by column chromatography, by eluting with isopropyl acetate/hexane 3:1 to 1:0 to afford (3S,5S)-5-biphenyl-4-ylmethyl-1-(2,2-dimethylpropionyl)-3-methylpyrrolidin-2-one (2-b, R1=pivaloyl) and (3R,5S)-5-biphenyl-4-ylmethyl-1-(2,2-dimethylpropionyl)-3-methylpyrrolidin-2-one (2-a, R1=pivaloyl). Ratio of diastereoisomers determined by 1H NMR to be 4:1 [(3S,5S):(3R,5S)]. 1H NMR (CDCl3) for (2-b, R1=Piv): 1.09, 1.14 (3H), 1.30 (9H), 1.34 (1H), 2.01-2.66 (3H), 3.03, 3.27 (1H), 4.31, 4.50 (1H), 7.21-7.53 (9H). Diastereomeric ratio is determined by integration of the pairs of signals at [3.03 ppm (2-a, R1=Piv) and 3.27 ppm (2-b, R1=Piv)] or those at [4.31 ppm (2-b, R1=Piv) and 4.50 ppm (2-a, R1=Piv)] from the 1H NMR spectrum. Spectroscopic data for (2-a, R1=Piv) as in Example 5.

Provenance & Evidence