Yield:215649-84-6 86%

Reaction Conditions:

Stage #1: tert-butyl 4-(3-nitrophenyl)-3-oxopiperazine-1-carboxylatewith trifluoroacetic acid in dichloromethane; for 2 h;
Stage #2: with sodium hydroxide in dichloromethane;water;Product distribution / selectivity;

Steps:

d

d. Preparation of 1-(3-Nitrophenyl)piperazin-2-one; tert-Butyl 4-(3-nitrophenyl)-3-oxopiperazine-1-carboxylate (60 g, 0.19 mol) was added to a solution of trifluoroacetic acid (120 mL, 1.6 mol) in dichloromethane (480 mL) and the resultant reaction mixture was stirred for 2 h. The dichloromethane and trifluoroacetic acid were then removed under reduced pressure and the reaction mixture was triturated with toluene (100 mL). Dichloromethane (750 mL) was added to the residue and the mixture was made basific with sodium hydroxide solution. The organic fraction was separated and concentrated under reduced pressure to a slurry, to which was added hexane. The resultant precipitate was filtered off, washed with hexane, and dried overnight under reduced pressure to gave 36 g (86%) of 1-(3- nitrophenyl)piperazin-2-one: solid; mp 137-139⁰C; R_f 0.33 (10% MeOH/DCM).

References:

WO2007/18941,2007,A2 Location in patent:Page/Page column 53; 68