This study is the first report of the application of sulfonated multi-walled carbon nanotubes (MWCNTs-SO3H) in the synthesis of tetrahydrobenzo[a]xanthene and tetrahydrobenzo[a]acridine derivatives. The catalyst was prepared via a chemical approach and the sulfonated groups were attached to the side-wall of MWCNTs with total density of 2.58 mmol.g-1. In order to prove functionalization of the MWCNTs-SO3H, the catalyst was characterized using FE-SEM, TEM, FT-IR, and Raman spectroscopy techniques. A three-component reaction including 2-naphthol, dimedone, and aromatic aldehydes were applied in the synthesis of tetrahydrobenzo[a]xanthene in the presence of 15.5 mol% of MWCNTs-SO3H under solvent-free conditions. Also, a four-component reaction including 2-naphthol, dimedone, aromatic aldehydes, and ammonium chloride was used in the synthesis of tetrahydrobenzo[a]acridine in the presence of 12.9 mol% of MWCNTs-SO3H under solvent-free conditions. All the derivatives of tetrahydrobenzo[a]xanthene and tetrahydrobenzo[a]acridine were obtained in good to excellent yields. The MWCNTs-SO3H was reused in seven consequent catalytic cycles without loss of their catalytic activity. Manuscript profile

Pyrimido[4,5-b]quinolones play a significant role in medicinal chemistry owing to their various biological properties, including antihistaminic, antimalarial, antifungal, anticancer, antioxidant, antiviral, anti-microbial, and anti-inflammatory activities. A dual acidic ionic liquid anchored on graphene oxide nanosheets (GO-Si-Pr-Lysin-SO3H) was provided and characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR). The six-step process was utilized to create this catalyst, beginning with graphite powder. This catalyst was capable to develop the one-pot and three components (6-amino-1,3-dimethyluracil, dimedone, and different aromatic aldehydes) synthesis of pyrimido[4,5-b]quinolone derivatives at moderate temperature in water as a green medium (12 derivatives). The results obtained indicated that this method could be an effective approach for synthesizing pyrimido[4,5-b]quinolones with high yields ranging from 86% to 98% in a short reaction time of 15 to 40 minutes. In addition, the pointed catalyst shows reusability and recoverability without remarkable loss of catalytic activity. Manuscript profile