Microwave-assisted Domino Cyclization for the Synthesis of Novel Spiro-benzo[a]phenazine Annulated Heterocycles Catalyzed by a Basic Ionic Liquid

Abstract

An efficient and green strategy for the improved synthesis of a biologically and pharmaceutically interesting multi‐functionalized diverse novel spiro‐benzo[a]phenazine annulated heterocycles was developed with the assistance of microwave irradiation. A sequential one‐pot, two‐step domino reaction starting from 2‐hydroxynaphthalene‐1,4‐dione, benzene‐1,2‐diamines, a cyclic carbonyl compound, and 1,3‐indandione in the presence of a basic ionic liquid (1‐butyl‐3‐methylimidazolium hydroxide) as an expedient, ecofriendly and reusable catalyst afforded the corresponding novel spiro[benzo[a]indeno[2′,1′:5,6]pyrano[2,3‐c]phenazine] derivatives with high yield under solvent‐free conditions. This domino Knoevenagel–Michael annulation reaction provided five new bonds (two C–C, two CN, and one C–O) and two new rings through multiple operations in a single flask.

Lipase‐catalyzed Synthesis of Sugar Ester in Mixed Biphasic System of Ionic Liquids and Supercritical Carbon Dioxide

“…Figure shows that the glucose conversion keeps increasing to a maximum of 84.16% with the increase in the amount of ILs from 0.5 mL/g celite to 1.0 mL/g celite, but higher IL loadings above 1.0 mL/g celite are no longer effective on the glucose conversion. With the increase in the amount of ILs, overstabilization of the enzyme enhances; meanwhile, more glucose dissolves in the ILs to facilitate higher reaction conversion. The optimal IL loading was thus selected as 1.0 g/g celite.…”

Recent advances in microwave-assisted multicomponent synthesis of spiro heterocycles

“…Microwave-assisted methods were employed to achieve high yields and short reaction times when 2-hydroxynaphthalene-1,4-dione ( 21 ), benzene-1,2-diamines ( 73 ), cyclic carbonyl compounds ( 60 ), and 1,3-indandione ( 80 ) were condensed, resulting in the formation of spiro[benzo[ a ]indeno[2′,1′:5,6]pyrano[2,3- c ]phenazine] derivatives ( 81 ) in high yields under solvent-free conditions. 201…”

A review on lawsone-based benzo[a]phenazin-5-ol: synthetic approaches and reactions

“…The 1,3-indandione attacks the Knoevenagel adduct 158 in a Michael-type addition to produce the intermediate 159, which then makes the inner molecular ring to be formed aer a tautomeric proton shi to generate 156. 79 Aer that, for synthesis of 3-amino- increased the electrophilicity of reactants, which simplies the reaction. Moreover, in the presence of monosubstituted benzene-1,2-diamine, major and minor isomers of the corresponding products are generated.…”

“…The 1,3-indandione attacks the Knoevenagel adduct 158 in a Michael-type addition to produce the intermediate 159 , which then makes the inner molecular ring to be formed after a tautomeric proton shift to generate 156 . 79…”