Glycine, N-(5-fluoro-2-nitrophenyl)-, ethyl ester → 6-fluoro-1,2,3,4-tetrahydroquinoxalin-2-one

Participants

Reaction Steps

A mixture of N-(5-fluoro-2-nitrophenyl)glycine ethyl ester (XI, EXAMPLE 5, 28.60 g), palladium on carbon (10%, 1.01 g) and methanol (500 ml) is shaken under 45 psi of hydrogen on a Parr shaker. After 2 hr an additional 0.54 g of 10% palladium on carbon catalyst is added. The mixture is shaken for an hour at 42 psi and then the catalyst is removed by filtration. p-Toluenesulfonic acid (0.314 g) is added to the filtrate. The solution is concentrated under reduced pressure to a volume of about 250 ml and then stirred at 20°-25°. The reaction is then further concentrated and dichloromethane is added. The solid that formed is collected and chromatographed on 800 ml of silica gel (column) eluting with dichloromethane/methanol (98/2). The appropriate fractions are pooled and concentrated and triturated with a small amount of dichloromethane. The solid is collected, dried, and triturated a second time with dichloromethane and redried to give the title compound, mp 176.0°-177.5°; NMR (CDCl3) 3.95, 3.99, 6.42, 6.63 and 8.33 δ.

Provenance & Evidence