p-Toluenesulfonic acid monohydrate → HCID 10065017, compound

Participants

Reaction Steps

A solution of (S)-5-[[oxo-1-(phenylmethyl)-2-pyrrolidinyl]methyl]-1,3-cyclohexanedione (60 g, 0.20 mol) and p-toluenesulfonic acid monohydrate (3.8 g, 0.02 mol) in 600 mL of ethanol and 1200 mL of toluene was stirred and refluxed for 1.5 h. The solvent was removed on a rotary evaporator and the residue dissolved in methylene chloride. The methylene chloride solution was washed with saturated sodium bicarbonate solution, brine, and dried over Na2SO4. The solvent was removed on a rotary evaporator to give 57.6 g of a crude oil. The crude product was chromatographed on silica gel (800 g) eluting with 2-4% methanol in ethyl acetate to give a 1:1 mixture of diastereomeric products: (5S,1R)-5-[(3-ethoxy-5-oxo-3-cyclohexen-1-yl)methyl]-1-(phenylmethyl)-2-pyrrolidinone and (5s,1S)-5-[(3-ethoxy-5-oxo-3-cyclohexen-1-yl)methyl]-1-(phenylmethyl)-2-pyrrolidinone (37.5 g, 57% yield). A total of 25.5 g of mixture (from this and a similar preparation) was chromatographed using a Waters Prep 500 high pressure liquid chromatograph, eluting with 1:24:25 methanol:ethyl acetate:hexane, and recovering and rechromatographing the mixed fractions. A total of 24.3 g (25.0% yield) of the more polar diastereomer, (5S,1R)-5-[(3-ethoxy-5-oxo-3-cyclohexen-1-yl)methyl]-1-(phenylmethyl)-2-pyrrolidinone, and a total of 23.9 g (24.6% yield) of the less polar diastereomer, (5S,1S)-5-[(3-ethoxy-5-oxo-3-cyclohexen-1-yl)methyl]-1-(phenylmethyl)-2-pyrrolidinone was obtained.

Provenance & Evidence