## 4 Synthesis of Amidoalkyl Naphthols via Multicomponent Mannich Condensation
### Homogeneous Catalysis
#### 4.1.2 Ionic Liquids and Deep Eutectic Solvents as Catalysts  
Ionic liquids are often proposed as alternative green reaction media due to their distinctive physical and chemical characteristics, but they have since surpassed this threshold and demonstrated their significance in reaction control [64]. The same is valid for the deep eutectic solvents, with their non-toxicity, biodegradability, and easy and low-cost preparation, which gives them additional benefits as catalysts for many organic reactions [65]. The application of these catalysts to the synthesis of amidoalkyl naphthols is summarized in Table 2.  
[PERSON] and [PERSON] successfully performed a one-pot synthesis of amidoalkyl naphthols using triethylammonium hydrogen sulfate ([Et\({}_{3}\)NH][HSO\({}_{4}\)]) as a green and reusable catalyst. The reported yields, using 20 mol% of catalyst at 70 \({}^{\circ}\)C, varied from 65 to 85% when the reaction times were in the range of 2-25 min [66]. N,N,N\({}^{\prime}\),N\({}^{\prime}\)-tetramethylthe-diaminium-N,N\({}^{\prime}\)-disulfonic acid chloride ([TMEDSA][Cl]\({}_{2}\)) has been found to be another efficient catalyst under solvent-free conditions. High yields (92-95%) of amidoalkyl naphthols were achieved within minutes using only 7.5 mol% of the catalyst at 70 \({}^{\circ}\)C. Notably, this method was applicable to the preparation of 1-carbamatoalkyl-2-naphth derivatives in excellent yields [54].  
[PERSON] et al., prepared the magnetic phosphonium ionic liquid (SO\({}_{3}\)H)(\(n\)-Bu)\({}_{3}\)P\({}^{+}\) FeCl\({}_{4}\)\({}^{-}\) that proved efficient as a catalyst in the synthesis of one-pot amidoalkyl naphthols. High to excellent yields of a number of amidoalkyl naphthols were obtained under solvent-free conditions at 45 \({}^{\circ}\)C in short reaction times using only 1 mol% of the catalyst [67].  
[PERSON] et al., synthesized a novel acidic magnetic dicationic  
[PERSON] et al., utilized triethanolammonium acetate ionic liquid as a green and reusable catalyst for solvent-free synthesis of a series of compounds, using 2-naphthol, (hetero)aromatic aldehydes, and urea/acetamide at 90 \({}^{\circ}\)C. Although relatively high catalyst loading of 20 mol% was required, the authors successfully prepared the targeted derivatives in moderate to high yields of 76 to 91% in up to 85 min reaction times. Furthermore, the synthesized products were tested for in vitro anti-_Helicobacter pylori_ activity and it was found that they exhibited promising potency [20].  
Numerous amidoalkyl naphthol derivatives have been synthesized by [PERSON] et al., using 10 mol% polinium dihydrogen phosphate as a green catalyst under solvent-free conditions at 120 \({}^{\circ}\)C. The synthesis of the remarkable number of 23 derivatives has been achieved in 79-92% yield. However, the recyclability of this catalytic system was not revealed. All of the obtained compounds were screened for their anti-leishman activity against _L. donovoni_. Four of the prepared molecules showed good bioactivity and were further subjected to a molecular docking study. Furthermore, the in silico study of the ADME (absorption, distribution, metabolism, and excretion) properties of the synthesized compounds showed good drug-like characteristics [22].  
A green method for the synthesis of amidoalkyl naphthols that utilizes 20 mol% [Cholinec][ZnCl\({}_{2}\)] deep eutectic solvent as a recyclable catalyst was reported. Moderate to high yields of 45-95% were achieved [70].  
[PERSON] and colleagues successfully prepared a series of amidoalkyl naphthols in water as a green solvent. In this work, 81 to 96% yields in 1-2.5 h were achieved using 10 mol% quaternary ammonium compound certrinonium bromide as a catalyst at 100 \({}^{\circ}\)C [71].