A series of 19 structurally diverse C(3)substituted derivatives of benzo [e][1,2,4]triazine were synthesized from 3-chloro-(1c) and 3-iodobenzo[e][1,2,4]triazine (1d) obtained in three steps from 2-nitroaniline in 37−55% yields. Nucleophilic aromatic substitution and metal-catalyzed (Pd, Cu) reactions led to functional derivatives that include alkyl (C 5 H 11 ), (het)aryl (Ph, 2-thienyl, ferrocenyl), ArCC, amine (NHPh and morpholine), PO(OEt) 2 , sulfanyl (SBu-t), alkoxide (OEt, OMe), and CN. The synthesis of C(3)−CF 3 derivative 1g via the Ruppert reaction with 1d and its 1-oxide analogue 2d led to the substitution followed by formal addition of HCF 3 to the CN bond. Pd-catalyzed carbonylation reactions of 1d and 2d did not give the corresponding C(3)-carboxylic acids. Therefore, acid 1f was obtained through hydrolysis of the CN. The substituent effect on the electronic structure of the benzo[e][1,2,4]triazine ring was investigated by spectroscopic methods (UV−vis and NMR) augmented with density functional theory calculations. Results show significant effect of the C(3) substituent on the π−π*(1) transition energy and good correlation of the 1 H NMR chemical shift with the substituent constant σ p . Molecular and crystal structures of six derivatives were established with the single-crystal X-ray diffraction method, and the substituent impact on the molecular geometry was investigated.

A series of 3-substituted 1-phenyl-1,4-dihydrobenzo­[e]­[1,2,4]­triazin-4-yls 1 was prepared by addition of PhLi to 3-substituted benzo­[e]­[1,2,4]­triazines 2 followed by aerial oxidation. The scope of the C(3) substituents in the reaction was investigated, and 10 structurally diverse radicals 1 were isolated, their stability was assessed and properties were investigated with spectroscopic and electrochemical methods. Two radicals were analyzed with single-crystal XRD methods. Experimental data are compared to DFT results and correlated with Hammett substituent parameters.

A series of 3-amino-and 3-alkyl-substituted 1-phenyl-1,4dihydrobenzo [e][1,2,4]triazin-4-yls was prepared in four steps involving Narylation, cyclization of N-arylguanidines and N-arylamidines, reduction of the resulting N-oxides to benzo[e][1,2,4]triazines, and subsequent addition of PhLi followed by aerial oxidation. The resulting seven C(3)-substituted benzo [e][1,2,4]triazin-4-yls were analyzed by spectroscopic and electrochemical methods augmented with density functional theory (DFT) methods. Electrochemical data were compared to DFT results and correlated with substituent parameters.