One-pot synthesis of pyrrolo[3,2-d]pyridazines and pyrrole-2,3-diones via zirconocene-mediated four-component coupling of Si-tethered diyne, nitriles, and azide.

A one-pot synthesis of pyrrolo[3,2-d]pyridazine derivatives via zirconocene-mediated four-component coupling of one Si-tethered diyne, two nitriles, and one azide is reported. When TMSN(3) was used, pyrrole-2,3-diones were formed in good yields. Further condensation of these highly functionalized pyrrole-2,3-diones with hydrazine and hydroxylamine afforded useful pyrrole-fused heterocycles.