Reaction of ketone alkylhydrazones with phosphorus trichloride: a general mild route to substituted pyrroles

Abstract

A new convenient and mild procedure for the synthesis of symmetrically and unsymmetrically substituted pyrroles is described. This one-pot synthesis consists of two different stages. The first stage, addition of PCl₃ to an alkylhydrazone, is always carried out at room temperature. The second stage, addition of an enolizable ketone to the previous reaction mixture, is performed at room temperature, or at 80 °C under reduced pressure. The results provide clear evidence that diazaphosphole derivatives being formed in the first stage are intermediates in this pyrrole synthesis.