Ring Opening of Pyrrolinium Ions Enabled Regioselective Synthesis of 4-Alkyl N-Arylpyrazoles

An unprecedented method for the regioselective synthesis of 1,3-diaryl 4-alkyl pyrazoles has been reported. A wide variety of 1,3-diaryl 4-alkyl pyrazoles were synthesized as a single regioisomer via a ring-opening cyclization reaction of unsaturated pyrrolinium ions in the presence of arylhydrazines. This method avoids using additional alkylation steps and hazardous oxidants that generally are essential for the synthesis of 4-alkyl N-arylpyrazoles.

Automated summary

An unprecedented method for the synthesis of 1,3-diaryl 4-alkyl pyrazoles as a single regioisomer has been reported, which avoids the use of additional steps and hazardous oxidants.