2-Ethyl-1-phenylindazolium hexafluorophosphate. N-heterocyclic carbene formation, rearrangement, ring-cleavage reactions, and rhodium complex formation

Abstract

Abstract 2-Ethyl-1-phenylindazolium hexafluorophosphate was deprotonated by potassium 2-methyl-butan-2-olate to give the N-heterocyclic carbene of indazole, i.e., indazol-3-ylidene. This N-heterocyclic carbene undergoes a ring transformation to 9-ethylaminoacridine. Trapping of the carbene with sulfur, silver(I) oxide, and carbonylbis(triphenylphosphane)rhodium(I) chloride resulted in the formation of indazolethione, indazolone (X-ray structure analysis), and carbonylbis(triphenylphosphane)(2-ethyl-1-phenyl-1H-indazol-3-ylidene)rhodium(I) hexafluorophosphate (X-ray structure analysis), respectively. Reaction of the indazolium salt with phenolate and thiophenolate gave an N-ethyl-2-(phenylamino)benzimidate and benzimidothioate, respectively.