Synthesis of 9,9-dimethyl-12-(aryl)-8,9,10,12-tetrahydrobenzo[a]xanthene-11-ones by modified kaolinite nanoclay as an efficient and reusable heterogeneous catalyst via a green protocol

Abstract

9,9-Dimethyl-12-(aryl)-8,9,10,12-tetrahydrobenzo[a]xanthene-11-one derivatives have been prepared via three component reaction of various aromatic aldehydes, dimedone and 2-naphthol. This green methodology has been effectively catalyzed by sulfonyl- functionalized kaolinite nanoclay (nano-kaolin-SO₃H) as a recoverable solid catalyst. This type of solid acid which contains the properties of a Lewis acid (Al³⁺cation) and a Brønsted acid (SO₃H group), has been characterized by ATR, TEM, FESEM, EDS, EDS mapping, XRD, TGA, BET and XRF techniques. Compared with conventional methods, this protocol has promising features for the reaction response such as simplicity in the experimental procedure, easier work-up, shorter reaction times and ease of separation of pure products with high yields.