A new series of stable carbenes - 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidenes including fluorosubstituted in a N4-aryl ring was synthesized by deprotonation of the respective salts with potassium tert-butoxide. The first tandem autotransformation of stable carbenes was found upon heating of 1-tert-butyl-3,4-diaryl-1,2,4-triazol-5-ylidenes to afford 5-amidino-1,2,4-triazoles. The reaction pathways of 1,2,4-triazol-5-ylidenes with carbodiimides were established: 5-amidino-1,2,4-triazoles are formed with alkylarylcarbodiimides, 1,2,4-triazolospiroimidazolidine is formed with diphenylcarbodiimide. It was found for the first time that the stable carbenes 1,2,4-triazol-5-ylidenes react with a malonic ester to afford heterocyclic zwitterionic compounds 1-alkyl-3,4-diaryl-1,2,4-triazolium-5-(2-carbethoxyvinyl)-1-oxides. This transformation can be considered as a new carbene version of Claisen reaction. New biscarbene complexes of transition metal salts were synthesized from 1,2,4-triazol-5-ylidenes and copper(I), nickel and palladium salts. Carbenoid transformations of mesoionic 1,4-diphenyl-1,2,4-triazolium-3-phenilimide were found and studied for the first time. The oxidation of the intermediate imidocarbene takes place upon deprotonation with potassium tert-butoxide in the presence of oxygen to form 1,3-diphenyl-2-phenylazoamidine. The mesoion reacts with sulphur to give the triazolthione, with 1-phenyl-2,2-dicyanoethylene it gives the adduct 3-phenilamino-1,4-diphenyl-1,2,4-triazolium-5-(1,1-dicyano-2-phenylethanide). Mono- and biscarbene complexes are formed under the action of copper(I) salts. The in vitro pharmaceutical exploration showed that 1-tert-butyl-3-o-4-p-fluorophenyl-1,2,4-triazolium-5-(2-carboethoxyvinyl-1-oxide) decreases the growth of S. aureus and M. luteum. Bis-(1-tert-butyl-3-phenyl-4-p-bromophenyl-1,2,4-triazol-5-ylidene) palladium iodide was found to exhibit the catalytic activity in dehalogenation of halogen substituted arenes.
