A Carbodiimide-Mediated Synthesis of Pyrimidothienopyridazine Derivatives via a Tandem Nucleophilic Addition-Intramolecular Hetero Conjugate Addition Annulation Strategy

Over the past decade, great progress has been made in the field of heterocyclic synthesis by the aza-Wittig methodology. The key intermediate iminophosphoranes can be prepared either by the Staudinger reaction from organic azides or by Kirsanov reaction from primary amines. Previously, we described an efficient synthesis for pyrimidothienopyridazines derivatives via intramolecular aza-Wittig reaction heterocyclization strategy.1 In this communication, we report the synthesis for pyridothienopyridazine and pyrimidothienopyridazine derivatives via aza-Wittig/electrocyclization and aza-Wittig/nucleophilic intramolecular hetero conjugate addition, respectively.