Mechanistic Insights for Acid‐catalyzed Rearrangement of Quinoxalin‐2‐one with Diamine and Enamine

Abstract

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Recent Developments Towards Synthesis of (Het)arylbenzimidazoles

“…This mechanism was confirmed by the isolation and characterization of spiro derivatives similar to structure A 116 and N-(2-aminophenyl)-3-phenylquinoxaline-2-carboxamide analogues similar to structure B 112c, d,117 in the reactions of quinoxalin-2-ones with other binucleophiles and DFT computed free energy paths 118 for the acetic acid catalyzed rearrangement of 3-benzoylquinoxalin-2(1H)-one (140a) with 1,2-DAB 1a.…”

“…126,127 The second type of Mamedov rearrangement is an acidcatalyzed rearrangement of quinoxalin-2-ones Q into 1hetarylbenzimidazolones BIon, which proceeds with nucleophilic reagents through the N-(2-isocyanatophenyl)hetarene-2-amines Is, formed as a result of C3-C2 bond opening in spiro derivatives of quinoxalin-2-ones of the sQ2 type, which do not contain a mobile hydrogen atom in the spiro-forming fragment (Scheme 65) (Type II Mamedov rearrangement). 118,127,129 Scheme 65 Schematically presentation of the rearrangement via the spiro-quinoxalinones without any mobile hydrogen atom in the spiroforming fragment Thus, the key stage in both types of Mamedov rearrangement is the formation of spiro-quinoxalinones, which can be synthesized not only using quinoxalinone derivatives and binucleophilic reagents (Schemes 60, 65), but also using other heterocyclic systems, as shown in Scheme 58. In the formation of spiro compounds from quinoxalinone derivatives, the functional group can provide one, two, and several atoms in the formation of a spiro fragment or not provide any at all, but at the same time taking part in its formation, as shown in Scheme 57 using the example of 3cyanoquinoxalin-2(1H)-ones.…”