Efficient and Inexpensive Synthesis of Benzimidazoles and Quinoxalines

Abstract

o-Phenylenediamines were reacted with carbonyl compounds, β-ketoesters, and 1,2-diketones in presence of ammonium salts to give benzimidazoles and quinoxalines in very good yields. Ammonium salts are commercial and environmentally benign catalysts.

Keywords:

• Ammonium salts
• benzimidazoles
• 1,2-diketones
• β-ketoesters
• OPDA
• quinoxalines

Notes

Reaction carried out with 4 mol of NH₄X.

^a

Isolated and unoptimized yields.

^b

Isolated and unoptimized yields.

^a

Note. All the compounds (3a–i) were characterized by their spectral data (¹H NMR, IR, and MS) and compared with authentic samples.

^a Isolated and unoptimized yields.

^a All the reactions were carried out with 1 mol of NH₄Br; isolated yields and unoptimized yields.

^a Isolated and unoptimized yields.