Formaldehyde → HCID 53312154, compound

Participants

Reaction Conditions

Reaction Steps

Under N2, LHMDS (12.5 mL, 1.0 M in tetrahydrofuran, 12.5 mmol) is added to the mixture of (S)-2-Biphenyl-4-ylmethyl-5-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (3a, R1=t-butoxycarbonyl) (1.76 g, 5 mmol) in 15 mL dry tetrahydrofuran is added to the reaction mixture at −10° C., the resulting mixture is then stirred for 30 min at −10° C. acetyl chloride (0.47 g, 6 mmol) is added to the reaction mixture at −10° C., after about 1 hour at −10° C., the reaction mixture is diluted with 10 mL saturated aqueous ammonium chloride solution and stirred for 15 min, stop stirring, and remove the lower aqueous layer. Formaldehyde (37% in water, 1.2 g, 15 mmol), K2CO3 aqueous solution (1.4 g in 5 mL water, 0.01 mol) and tetrabutyl-ammonium-hydroxide solution (40% in water, 0.06 g, 0.25 mmol) are added to the remaining organic phase, and heated to 50° C., and stirred for 2 hours. Then the reaction mixture is diluted with 10 mL brine and stirred for 15 min, stop stirring, and remove the lower aqueous layer. the organic phase is then concentrated in vacuo. ethyl acetate 20 mL is added, filtered and the filtrate concentrated to give (R)-5-Biphenyl-4-ylmethyl-3-methylene-2-oxo-pyrrolidine-1-carboxylic acid tert-butylester (1a, R1=t-butoxycarbonyl). Crude (R)-5-biphenyl-4-ylmethyl-3-methylene-2-oxo-pyrrolidine-1-carboxylic acid tert-butylester (1a, R1=t-butoxycarbonyl) can be purified by column chromatography eluting with 3:1 heptane/ethyl acetate. The ratio of intermediate (3S,5S-4, R1=t-butoxycarbonyl, R4=methyl) to (3R,5S-4, R1=t-butoxycarbonyl, R4=methyl) is 70:30 as determined by HPLC. Spectroscopic data as Example 28, Method 1.

Provenance & Evidence