Synthesis of trifluoromethyl formazans by reaction of trifluoromethyl N-acylhydrazones/N-Aryl hydrazones and aryldiazonium tetrafluoroborates

An efficient direct azo-coupling reaction of trifluoromethyl N-acylhydrazones/N-aryl hydrazones with aryldiazonium tetrafluoroborates was developed for the synthesis of various trifluoromethyl formazans. This protocol has the advantages of mild reaction condition, broad substrate scope and easy operation, which extends the application of trifluoromethyl N-acylhydrazones/N-aryl hydrazones as versatile trifluoromethyl building blocks in organic synthesis.