The mechanism of amide catalysis of the reaction of the formation of polyimides

Synthesis of benzo[b]xanthene‐triones and tetrahydrochromeno[2,3‐b]xanthene tetraones via three‐ or pseudo–five‐component reactions using Fe3O4@SiO2/PEtOx as a novel, magnetically recyclable, and eco‐friendly nanocatalyst

“…The proposed mechanism for the reaction using basic Fe 3 O 4 @SiO 2 /PEtOx as catalyst is described for the preparation of tetrahydrochromeno[2,3‐ b ]xanthene tetraones and benzo[ b ]xanthene‐triones derivatives using benzaldehyde, dimedone, and 2‐hydroxy‐1,4‐naphthoquinone or 2,5‐dihydroxy‐1,4‐benzoquinone in Scheme . According to literature report, 2‐benzylidene‐5,5‐dimethylcyclohexane‐1,3‐dione ( I ), containing the electron‐poor C–C double bond, is formed quantitatively by Knoevenagel addition of dimedone to the benzaldehyde in the presence of Fe 3 O 4 @SiO 2 /PEtOx as catalyst. As shown in Scheme , the catalyst with basic sites (from one of the mesomeric forms) absorbed the acidic proton of 1,3‐dicarbonyl compound as well as activated the carbonyl group of aldehyde for fast and easier condensation reactions.…”

“…The proposed mechanism for the reaction using basic Fe 3 O 4 @SiO 2 /PEtOx as catalyst is described for the preparation of tetrahydrochromeno [2,3-b]xanthene tetraones and benzo[b]xanthene-triones derivatives using benzaldehyde, dimedone, and 2-hydroxy-1,-4-naphthoquinone or 2,5-dihydroxy-1,4-benzoquinone in Scheme 2. According to literature report, [44][45][46][47][48][49] 2-benzylidene-5,5-dimethylcyclohexane-1,3-dione (I), Melting Point ( C) Founded Reported [43] 4a…”