Synthesis of Antimicrobial Benzo[1,2,4]triazoloazepinium Salts and Tetrahydronaphtho[1,2-e][1,2,4]triazines by Polar
Jie Zheng1, Shu-Yu Meng1, Quan-Rui Wang1
1Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200438, PR China.
Abstract:
Novel annulated azaheterocycles of benzo[1,2,4]triazoloazepine and tetrahydronaphtho[1,2-e][1,2,4]triazine derivatives have been synthesized. Treatment of 2-diazenyl-1,2,3,4-tetrahydronaphthalen-2-yl acetates with BF3·Et2O generates 1-aza-2-azoniaallenium cation intermediates (or azocarbenium ions), which are intercepted by nitriles via cascade polar [3+ + 2]-cycloaddition/rearrangement reactions to afford benzo[1,2,4]triazoloazepinium salts. These literature unprecedented fused tricycle compounds have been shown to exhibit antimicrobial activity against Gram-positive Staphylococcus aureus with in silico docking studies, suggesting that they may exhibit their antibiotic activity through inhibition of DNA gyrase. Additionally, when ethyl 2-(1-acetoxy-1,2,3,4-tetrahydronaphthalen-2-yl)diazene-1-carboxylate is employed, the reaction with BF3·Et2O produces 1,2-diaza-1,3-diene, which reacts with nitriles via a diaza-Diels-Alder reaction with inverse electron demand, leading to ethyl tetrahydronaphtho[1,2-e][1,2,4]triazine carboxylates. The DFT calculation has been performed to further prove the D-A reaction speculation.
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