Isomerization in the Oxidative Cyclocondensation of 2‐Aroylmethyl‐1H‐benzimidazoles with o‐Aminothiophenol.

Abstract

Thiazine derivatives R 0610Isomerization in the Oxidative Cyclocondensation of 2-Aroylmethyl-1H-benzimidazoles with o-Aminothiophenol. -Oxidative cyclocondensation of the title aroylmethylbenzimidazoles (I) with o-aminothiophenol affords previously unknown benzimidazolyl-2H-benzothiazines (III) or isomeric -4H-benzothiazines (IV) depending on the reaction conditions. Cyclocondensation of p-nitrophenacyl derivative (VII) is complicated by a hydrolytic fission leading to compound (IX). -(DZVINCHUK, I. B.; VYPIRAILENKO, A. V.; LOZINSKII, M. O.; Chem. Heterocycl.

Isomerization of 2-Phenacyl-1H-benzimidazole Arylhydrazones to 1-Aryl-5-(o-aminoanilino)-3-phenylpyrazoles by Trifluoroacetylation and Hydrazinolysis

“…We were unable to find conditions for such direct isomerization. On heating and with acid catalysis phenylhydrazones of type 1 are transformed in a different direction and undergo Fischer indolization [6]. As we found earlier [7], the recyclization of 2-phenacyl-1H-benzimidazole phenylhydrazone (1a) can be initiated during acylation with benzoyl chloride, leading to the production of the N-benzoylsubstituted compound 3, which is not however transformed into the required product when heated with hydrazine hydrate for 12 h.…”

Recyclization on interaction of arylhydrazones of 2-aroylmethyl-1H-benzimidazoles with ethyl isothiocyanate

“…For example, phenylhydrazones of 2-aroylmethyl-1H-benzimidazoles 1a-f are not inclined to remake the heterocyclic ring on acid catalysis, but undergo Fischer indolization [7]. However compounds of type 1 (and of the related type 2) are readily recyclized under the conditions of an acylation reaction, by the action of aroyl chlorides or anhydrides of carboxylic acids they give 5-(2-acylaminoanilino)-1,3-diarylpyrazoles [8-10].…”