Thionation reactions of 2-pyrrole carboxylates

Reaction of 2- pyrrolecarboxylates with Lawesson's reagentat elevated temperatures results in the corresponding thionoesters, concurrent with the production of a new class of pyrrole annulatedwith the (1,3,2)-thiazaphospholidine unit. X-ray crystallographywas used to identify the pyrrolicthiazaphospholidine, which was found to have unique structural features compared to literature analogues. Addition of BF3·OEt2 to the thionation procedure was found to produce the corresponding F- BODIPY, constituting a four-step reaction in one-pot. The scope and limitations of these reactions involving the promiscuous Lawesson's reagentare discussed herein.