1370588-43-4Relevant articles and documents
Synthesis of bis-heterocyclic 1H-imidazole 3-oxides from 3-oxido-1H-imidazole-4-carbohydrazides
Pieczonka, Adam Marek,Mloston, Grzegorz,Heimgartner, Heinz
, p. 404 - 414 (2012/05/04)
The reaction of 1H-imidazole-4-carbohydrazides 1, which are conveniently accessible by treatment of the corresponding esters with NH2NH 2·H2O, with isothiocyanates in refluxing EtOH led to thiosemicarbazides (=hydrazinecarbothioamides) 4 in high yields (Scheme 2). Whereas 4 in boiling aqueous NaOH yielded 2,4-dihydro-3H-1,2,4-triazole-3- thiones 5, the reaction in concentrated H2SO4 at room temperature gave 1,3,4-thiadiazol-2-amines 6. Similarly, the reaction of 1 with butyl isocyanate led to semicarbazides 7, which, under basic conditions, undergo cyclization to give 2,4-dihydro-3H-1,2,4-triazol-3-ones 8 (Scheme 3). Treatment of 1 with Ac2O yielded the diacylhydrazine derivatives 9 exclusively, and the alternative isomerization of 1 to imidazol-2-ones was not observed (Scheme 4). It is important to note that, in all these transformations, the imidazole N-oxide residue is retained. Furthermore, it was shown that imidazole N-oxides bearing a 1,2,4-triazole-3-thione or 1,3,4-thiadiazol-2-amine moiety undergo the S-transfer reaction to give bis-heterocyclic 1H-imidazole-2-thiones 11 by treatment with 2,2,4,4-tetramethylcyclobutane-1,3- dithione (Scheme 5). Copyright