Nitrogen-Rich Mesoionic Compounds from 1,3-Diaryl-5-chlorotetrazolium Salts and Nitrogen Nucleophiles − Synthesis and Properties of 1,3-Diaryl-5-azidotetrazolium Salts

Synthesis of 3-(phenylazo)-1,2,4-triazoles by a nucleophilic reaction of primary amines with 5-chloro-2,3-diphenyltetrazolium salt via mesoionic 2,3-diphenyltetrazolium-5-aminides

“…The 5-chloro-2,3-diphenyltetrazolium salt 2 was prepared in an analogous manner to the corresponding 1,3-diphenyl isomer 1 [ 6 – 7 ]. Thus, the treatment of 2,3-diphenyltetrazolium-5-olate with phosphorus oxychloride gave 2 in high yield as stable crystals, after an anion exchange to tetrafluoroborate.…”

“…When triethylamine is employed as a base in the reaction with primary amines, deprotonation from 4 proceeds readily to give tetrazolium-5-aminides A . Contrary to the stable type A mesoionic tetrazolium-5-aminides [ 6 – 7 ], type B mesoionic aminide A undergoes further transformations from its acyclic tautomer B to furnish 1,2,4-triazoles 3 .…”

“…Type B mesoionic compounds are less common compared with type A mesoions. The 5-chloro-1,3-diphenyltetrazolium salt ( 1 ) has been proved to be a versatile precursor to several type A 1,3-diphenyltetrazolium mesoionic compounds, because the chlorine atom is a good leaving group and easily replaced by a variety of nucleophiles [ 6 – 7 ]. Although the corresponding 5-chloro-2,3-diphenyltetrazolium salt 2 is not yet known, it is expected that 2 is also useful for the synthesis of type B tetrazolium mesoions.…”

Copper(I)- and Mesoionic-Hydroxyamide-Catalyzed Chemoselective Aerobic Oxidation of Primary Benzylic Alcohols

“…We have recently focused on mesoionic 1,3-diphenyltetrazolium-5-hydroxyamide 1, 9 and have developed an efficient and chemoselective aerobic oxidation method using 5-nitroso-1,3-diphenyltetrazolium tetrafluoroborate 10a involving a reversible redox couple with 1 as a catalyst similar to TEMPO (Equation 2). 10b…”

Mesoionic tetrazolium-5-aminides: Synthesis, Molecular and Crystal Structures, UV-Vis Spectra, and DFT Calculations

“…The most interesting and less examined 5-aminotetrazole derivatives are tetrazolium-5-aminides, which can be depicted as 4 by analogy with other mesoionic tetrazoles [11,12]. The first representatives of tetrazole-5-aminides were reported in the 1950s [13,14], whereas next publications were appeared only five decades later, being devoted to synthesis and photochemistry of 1,3-diaryltetrazolium-5-aminides [15][16][17][18][19][20][21]. NMR studies of few tetrazole-5-aminides were carried out as a part of studies of mesoionic compounds [22][23][24].…”