Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

Present status of quinoxaline motifs: Excellent pathfinders in therapeutic medicine

“…<<<<Scheme 9>>>> (d) Chen and coworkers reported solution-phase synthetic protocol as a convenient route for the preparation of a small library of unsymmetrically annulated benzimidazole-linked indolo quinoxalines 33 [56] (Scheme 10). A reagent-based diversification approach coupled with the Pictet-Spengler type condensation used, was also reported to afford of 4,5-dihydroimidazo-and imidazo [1,5-a]quinoxalines in another study [57]. <<<<Scheme 10>>>> (e) Although, the solution-phase parallel synthesis of a series of diamino-2-quinoxalinol derivatives was previously reported [58,59].…”

The Chemistry and Biological Applications of 3H‐Pyrrolo[2,3‐c]quinolines and Marinoquinolines

“…In that same year of 2019, Guillon and co‐workers reported the synthesis, crystal structure and anti‐leukemic activity of a new, and more structurally complex, marinoquinoline analogue: the 4‐{4‐[(4‐(2‐oxo‐2,3‐dihydro‐1 H ‐benzimidazol‐1‐yl)piperidin‐1‐yl)benzyl]}‐3‐phenyl‐3 H ‐pyrrolo[2,3‐ c ]quinolone 147 (Scheme 28). [47] The synthesis was performed by a multi‐step route beginning with the synthesis of the pyrrole moiety using the ( E )‐1‐(2‐nitrophenyl)‐2‐nitropropene 141 and ethyl isocyanide under basic medium to give the ethyl 4‐methyl‐3‐(2‐nitrophenyl)pyrrole‐2‐carboxylate 142 . The intermediate N ‐aryl pyrrole 143 was obtained by a nucleophilic substitution of the ethyl pyrrole‐2‐carboxylate 142 with bromobenzene having CuI as a catalyst.…”

“…The marinoquinoline core was built using a key Pictet‐Spengler reaction under two different conditions. The method A used 0.5 equivalents of TFA and was adapted from Schwalm and Correia, [26] while the method B used catalytic amounts of TsOH and one equivalent of benzotriazole, as reported by Verma et al [47] . (Scheme 23a).…”

“…[33] The marinoquinoline core was built using a key Pictet-Spengler reaction under two different conditions. The method A used 0.5 equivalents of TFA and was adapted from Schwalm and Correia, [26] while the method B used catalytic amounts of TsOH and one equivalent of benzotriazole, as reported by Verma et al [47] (Scheme 23a). These strategies allowed the synthesis of the natural MQ A-C and MQ E, the unnatural derivatives 39 a-I, and several novel unnatural MQs, exemplified by 114 a-b and 115 a-e (Scheme 23b).…”

Synthesis of New Pyrimido[5′,4′:5,6][1,4]thiazino[2,3‐b]quinoxaline Derivatives in One Step

“…Furthermore, quinoxaline containing heterocycles have also significant applications in the field of industrial and agricultural and have been applied as dyes, electroluminescent materials, and insecticides . Recently, improved methods have also been reported for the synthesis of heterocycles containing the quinoxaline .…”