Reaction cascades initiated by nucleophilic attack of heteropentalene mesomeric betaine and nitrogen-rich mesoionic tetrazolium-5-amides on electron-deficient unsaturated compounds. Synthesis of novel heterocyclic systems.
The reactions of heteropentalene mesomeric betaine 1 and nitrogen-rich mesoionic tetrazolium-5-amides 4, 11 and 16-18 with electron-deficient unsaturated compounds have been studied. Novel heterocyclic systems, tetrazolo[4,5-a][1,7]benzodiazonine inner salt 2 and 3-oxo-3,7-dihydro-2H-pyrazolo[3,4-b]pyridine 5, have been synthesized by the reactions of dimethyl acetylenedicarboxylate with 1 and tetrazolium-5-anilide 4, respectively, and fully characterized by X-ray crystallography. It has been found that the reactions of other tetrazolium-5-amides are also initiated by the nucleophilic addition of the electron-rich amide nitrogen to the electron-deficient unsaturated compounds.
Mesoionic oxides: facile access from triazolium salts or triazolylidene copper precursors, and catalytic relevance.
Reaction of CsOH with triazolium salts affords mesoionic compounds containing an exocyclic oxygen; the same product is obtained by reaction of the corresponding Cu(I) triazolylidenes with CsOH and represents an unusual reactivity pattern of N-heterocyclic carbene precursors that has implications for carbene copper-catalyzed reactions.
Cyclic meso-ionic compounds. Part 17. Synthesis, spectroscopic properties, and chemistry of 1,2,3,4-oxatriazolium-5-aminides and 1,2,3,4-tetrazolium-5-olates
Derivatives of the isomeric meso-ionic 1,2,3,4-oxatriazolium-5-aminides (3) and 1,2,3,4-tetrazolium-5-olates (4) have been prepared and characterised and their interconversion (3 → 4) has been examined. 3-Phenyl-1,2,3,4-oxatriazolium-5-anilide (3a) undergoes a 1,3-dipolar cycloaddition with p-chlorophenyl isocyanate. The 1,2,3,4-tetrazolium-5-olates (4) form tetrafluoroborate salts when treated with triethyloxonium tetrafluoroborate.