TiO<sub>2</sub> Nanoparticles Immobilized on Carbon Nanotubes: An Efficient Heterogeneous Catalyst in Cyclocondensation Reaction of Isatins with Malononitrile and 4‐Hydroxycoumarin or 3,4‐Methylenedioxyphenol under Mild Reaction Conditions
Shahrzad Abdolmohammadi, Seyed Reza Rasouli Nasrabadi, Mohammad Reza Dabiri, Sayed Mustafa Banihashemi Jozdani
Abstract
TiO 2 nanoparticles supported on carbon nanotubes (TiO 2 ‐CNTs) as an efficient heterogeneous catalyst was used for the synthesis of spiro[3,4′]1,3‐dihydro‐2 H ‐indol‐2‐one‐2′‐amino‐5′‐oxo‐4' H ,5' H ‐pyrano[3′,2′‐ c ]chromen‐3′‐yl cyanides and spiro[3,8′]1,3‐dihydro‐2 H ‐indol‐2‐one‐6′‐amino‐8' H ‐[1′,3′]dioxolo[4′,5′‐ g ]chromen‐7′‐yl cyanides via the cyclocondensation reaction of isatins with malononitrile and 4‐hydroxycoumarin or 3,4‐methylenedioxyphenol in aqueous media at room temperature. This reaction offers several sustainable and economic benefits such as high yields of products, convenient operation, and use of non‐toxic catalyst in water media.