Catalysis by FeF3 in water: a green synthesis of 2-substituted 1,3-benzazoles and 1,2-disubstituted benzimidazoles

FeF3 in water facilitated the reaction of 1,2-phenylenediamine and 2-aminothiophenol with 1 equivalent of an alkyl- or aryl-aldehyde leading to 1,3-benzazoles in open air. The process afforded 1,2-disubstituted benzimidazoles when 1,2-phenylenediamine was reacted with 2 equivalents of aryl aldehyde. The methodology is operationally simple, free from the use of hazardous organic solvents and chemoselective. The products were isolated by simple filtration and the catalyst can be recovered and recycled.