DBU: a highly efficient catalyst for one-pot synthesis of substituted 3,4-dihydropyrano[3,2-c]chromenes, dihydropyrano[4,3-b]pyranes, 2-amino-4H-benzo[h]chromenes and 2-amino-4H benzo[g]chromenes in aqueous medium

Multicomponent reaction of benzyl halides: Synthesis of [1,2,4]triazolo/benzimidazolo quinazolinones

“…The reaction underwent smooth cyclization to give respective quinazolinone derivatives in virtually good yields (Table 2, entries 10-14). Thereafter, a series of different substituted quinazolinone analogs were synthesized from different benzyl halides containing electron-withdrawing and electron-donating groups using trimethyl amine N-oxide in ethanol at 70 °C in good yields [45] ( Table 2). In general, the overall yield ranged from 96% for 3,3-dimethyl-12(4-nitro-phenyl)-1,2,3,4,5,12-hexahydrobenzo [4,5]imidazo[2,1-b]quinazolin-1-one (4h) (entry 8) to 85% for 6,6-dimethyl-9-(4-hydroxy-phenyl)-5,6,7,9-tetrahydro-4H-1,2,4-triazolo[5,1-b] quinazolin-8-one (4m) (entry 13).…”

Sonochemical synthesis of chromenes catalyzed by L-phenyl alanine-attached nano-Fe3O4@SiO2

“…Therefore, the development of facile, efficient, flexible and useful methods for the synthesis of chromenes is still favorable (10). Indeed, the synthesis of chromenes through multicomponent reactions (MCRs) has attracted much attention due to excellent synthetic efficiency, experimental simplicity, inherent atom economy and their ability to create molecular complexity starting from simple substrates (11,12). The core/shell Fe 3 O 4 nanoparticles are easily prepared and have been widely studied due to their unique physical properties.…”

Novel ionic liquid supported on Fe3O4 nanoparticles as an efficient catalyst for the synthesis of new chromenes

“…Therefore, the improvement of simple methods for the development of chromenes is still necessary and in demand. The preparation of chromenes has been reported in the presence of diverse catalysts such as 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), [6] tetrabutylammonium bromide, [7] diammonium hydrogen phosphate, [8] H 6 P 2 W 18 O 62 ⋅18H 2 O, [9] Zn(L-proline) 2 , [10] nanomagnetically modified thioglycolic acid, [11] Fe 3 O 4 /poly(ethylene glycol) core/shell, [12] nano-MgO, [13] 1-butyl-3-methylimidazolium hydroxide, [14] 1-butyl-3-methylimidazolium tetrafluoroborate, [15,16] 1,3-dimethyl-2-oxo-1,3-bis(4-sulfobu tyl)imidazolidine-1,3-diium hydrogen sulfate, [17] 3-hydroxypropanaminium acetate [18] and N,N-dimethylaminoethylbenzyldimethylammonium chloride. [19] However, some of the reported methods have disadvantages including long reaction times, harsh reaction conditions and use of toxic and non-reusable catalysts.…”