Methylglyoxal → 5,8-Dibromo-2-methyl-quinoxaline

Participants

Reaction Steps

A 40% aqueous solution of methylglyoxal (6.7 M, 6.3 mL, 112 mmol, 1.48 equiv) was added to a suspension of 3,6-dibromo-benzene-1,2-diamine (Step 1.6) (20 g, 75.5 mmol) in EtOH (400 mL). The reaction mixture was stirred for 2 h at rt and for 0.5 h at reflux, allowed to cool and filtered to afford 7.66 g of the title compound. The filtrate was concentrated and the residue triturated in EtOAc and filtered. The filtrate was concentrated and the residue was purified by silica gel column chromatography (Hex/EtOAc, 1:0→9:1) to provide additional 2.15 g of the title compound. The title compound: ESI-MS: 300.9/302.9/304.9 [M+H]+; tR=4.81 min (System 1); TLC: Rf=0.90 (Hex/EtOAc, 1:1).

Provenance & Evidence