Synthesis of Quinoxalines

Recent Developments Towards Synthesis of (Het)arylbenzimidazoles

“…In all the cases discussed it is this green-colored hydrogen atom that is responsible for the rearrangement. 126,127 For example, there arises an important point. Is the presence of mobile hydrogen atom in the spiro-fragment necessary?…”

“…128c Acid-catalyzed multicomponent rearrangements of in situ generated 2-((quinoxalin-3(4H)-on-2-yl)(aryl)methylene)malononitriles F via intermediates G (Nu = NR 2 R 3 and OAlk) (Scheme 64) in the synthesis of 5-(benzimidazol-2on-1-yl)-4-arylpyrrole-3-carbonitriles 191 (G, Nu = NR 2 R 3 ) and 192 (G, Nu = OAlk) with various substituents in the second position of the intermediates G once again confirm our hypothesis that 'any of the spiro-derivatives of 1,2,3,4-tetrahydroquinoxalin-3-one without any mobile hydrogen atom in their spiro-forming component are on their way to the benzimidazolone derivative with the spiro-forming component at position 1'. 127,129 Thus, we have discovered two fundamentally new rearrangements in the quinoxalinone series. The first is the acid-catalyzed rearrangement of quinoxalin-2-ones Q into 2-hetarylbenzimidazoles BI, which proceeds with nucleophilic reagents through the ortho-aminoanilides An of the corresponding hetarenecarboxylic acids, formed as a result of N1-C2 bond opening in spiro derivatives of quinoxalin-2-ones type sQ1 with at least one mobile hydrogen atom in the spiro-forming fragment (Scheme 60) (Mamedov heterocycle rearrangement or Type I Mamedov rearrangement).…”

“…The first is the acid-catalyzed rearrangement of quinoxalin-2-ones Q into 2-hetarylbenzimidazoles BI, which proceeds with nucleophilic reagents through the ortho-aminoanilides An of the corresponding hetarenecarboxylic acids, formed as a result of N1-C2 bond opening in spiro derivatives of quinoxalin-2-ones type sQ1 with at least one mobile hydrogen atom in the spiro-forming fragment (Scheme 60) (Mamedov heterocycle rearrangement or Type I Mamedov rearrangement). 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.…”

New opportunities for the synthesis of quinoxaline derivatives

“…Among derivatives of quinoxaline, compounds possessing various types of biological activities were found [1][2][3][4]. Thus, the Quinoxidine and the Dioxidine are used as antimicrobial agents [5].…”

Syntheses of Pyrazine-, Quinoxaline-, and Imidazole-Fused Pyrroline Nitroxides

“…It was obvious that the condensation of 1,2-diamines with paramagnetic 1,2-diketones suggests a synthetic route to novel paramagnetic 1,4-diazines and quinoxalines. 14,15 Inspired by the work of Sandris and Ourisson, 16 we attempted the synthesis of 1-oxyl-2,2,5,5-tetramethylpyrrolidine-3,4-dione by SeO 2 oxidation of 1-oxyl-2,2,5,5-tetramethylpyrrolidine-3-one (1) 17 (Scheme 1); however, no reaction occurred, and only starting material was recovered.…”