Cerium oxide nanoparticle-catalyzed three-component protocol for the synthesis of highly substituted novel quinoxalin-2-amine derivatives and 3,4-dihydroquinoxalin-2-amines in water

Interrupted Ugi and Passerini Reactions: An Underexplored Treasure Island

“…16 Other reports have described the same reaction changing the activating group (Scheme 6). 15,17 The same reaction has also been reported with ketones working in the presence of a catalytic amount of PTSA. Due to the lack of hydrogen abstraction, 2-amino-3,4-dihydroquinoxalines 22 were obtained (Scheme 7).…”

“…Nevertheless, it has been reported that in the presence of other catalytic systems (e.g., cerium oxide nanoparticles) the reaction was also successful with aliphatic aldehydes leading to the formation of pyrazine-2,3-dicarbonitriles. 15 Krasavin and Parchinsky were the first to demonstrate that o-phenylenediamines 18 react in a three-component interrupted Ugi reaction with aldehydes 19 and isocyanides 2 to form 1,4-dihydroquinoxalines 20. Due to the air instability of these products, treatment of the crude material with DDQ afforded stable quinoxalines 21.…”

Catalyst-free synthesis of novel 1,5-benzodiazepines and 3,4-dihydroquinoxalines using isocyanide-based one-pot, three- and four-component reactions

“…[4][5][6][7][8] One of the benets of the isocyanide functional group in MCRs is its unique reactivity; thus isocyanide-based MCRs (IMCRs) are considered amongst the most versatile MCRs to generate diversity and structural complexity. [9][10][11] The use of isocyanides for the synthesis of nitrogen-containing heterocyclic compounds such as benzodiazepines [12][13][14] and quinoxalines [15][16][17][18] is well exploited. For example, the reaction of o-phenylenediamine 1 and isocyanide 2 in the presence of two equivalents of acetone 3a using ammonium chloride as a catalyst was reported to give benzodiazepine-2-carboxamides 4 as shown in Scheme 1a.…”

Recent developments on nano-ZnO catalyzed synthesis of bioactive heterocycles

“…Abdolmohammadi [80] synthesized a series of hexahydropyrido [2,3-d]pyrimidine derivatives (29) via the cyclocondensation reaction between arylmethylidenepyruvic acids (27) and 6-aminouracils (28,28a) in the presence of catalytic amount of ZnO nanoparticles under solvent-free condition at 70 °C. After completion of the reaction, ZnO nanoparticles were recovered and recycled three times without any apparent loss in catalytic activity ( Table 7).…”

“…in nano form, have drawn considerable attention as efficient, environmentally sustainable, heterogeneous catalysts and have found immense applications in various organic transformations that include C-H funtionalizaion [20], synthesis of 2-aminobenzimidazoles, Fig. 1 Some of the marketed drugs containing heterocycles 2-aminobenzothiazoles, benzoxazoles [21], tetrahydrobenzofurans [22], α-aminophosphonate [23], bis-2,3-dihydroquinazolin-4(1H)-ones [24], 1,4-substituted 1,2,3-triazoles [25], xanthenes [26], pyrano [2,3-d]pyrimidines, 4H-chromenes, and dihydropyrano [3,2-c]chromenes [27], substituted pyridines [28], quinoxalin-2-amine [29] and many more [30,31].…”