O-Phenylenediamine → 3,3-Dimethyl-1,2,3,4-tetrahydroquinoxalin-2-one

Participants

Reaction Steps

A mixture of 1,2-phenylenediamine (II, 7.55 g), ethyl 2-bromoisobutyrate (III, 12.8 ml), diisopropylamine (15.5 ml) and DMF (30 ml) is heated at 110° for 5 hr, after which an additional ethyl bromoisobutyrate (III, 0.5 ml) and diiopropylethylamine (0.8 ml) is added. After heating for 2 more hours, the reaction is cooled and the DMF is removed in under reduced pressure. The residue is stored overnight in the freezer and then partitioned between ethyl acetate, water, and saline. The phases are separated and the organic phase is dried over magnesium sulfate, the organic phase is removed under reduced pressure. The residue is chromatographed eluting with ethyl acetate/dichloromethane (20/80). The product crystallizes out in the column. The product is recrystallized from dichloromethane/hexane to give the title compound, mp 173°-174°; NMR (CDCl3) 1.41, 3.72, 6.67, 6.76, 6.87 and 8.50 δ.

Provenance & Evidence