Rearrangement Cascade Initiated by Nucleophilic Benzyne Attack on 3,6-Di(2-pyridyl)-1,2-diazines

Aryne intermediates in synthetic organic chemistry offer versatile routes to complex heterocyclic structures that are valuable in pharmaceuticals and materials science. We present a one-step aryne-mediated reaction to synthesize pyrido[1,2-a]indoles interconnected through vinylene or 1,2-phenylene linkers to pyridotriazoles using 2-pyridyl-substituted pyridazines and phthalazines as confirmed via single-crystal X-ray crystallography and NMR spectroscopy. This unexpected rearrangement proceeds under mild conditions. Considering that five bonds are broken and three new bonds are formed in the reaction between 3,6-di-2-pyridyl-1,2,4,5-tetrazine and benzyne, the yield of 16% is fair. Electron-rich substituents on aryne precursors destabilized the products, while electron-deficient substituents offered some stability improvements. DFT studies could reveal the mechanism of this rearrangement.