## 4 Synthesis of Amidoalkyl Naphthols via Multicomponent Mannich Condensation
### Heterogeneous Catalysis  
#### 4.2.1 Nanomaterials as Catalysts  
Nanocatalysts are a rapidly emerging field of research. They find numerous applications in catalytic reactions due to their large surface area, easy separation, and reusability [72]. A large number of nanocatalysts have been reported to efficiently catalyze the \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Refs.** & **Type of Catalyst (mol\%)** & **Resability (Cycles)** & **Substituents (Number of Products)** & **Reaction** & **T, \({}^{\circ}\)C** & **Reaction Time** & **Yield, \%** \\ \hline
[66] & [EthNII][HSO\({}_{4}\)] (20) & Yes (3) & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\\ \text{R}^{2}=\text{Methyl, NH}_{2}\end{array}\) & Solvent-free & 70 & 2–25 min & 65–85 \\  & Tetramethylethylene & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\\ \text{R}^{2}=\text{Methyl}\end{array}\) & Solvent-free & 70 & 15–25 min & 92–95 \\
[54] & diaminium disulfide acid & No & \(\begin{array}{c}\text{R}^{2}=\text{Alkyl, Alkyl, Aryl}\\ \text{(13)}\end{array}\) & Solvent-free & 70 & 15–25 min & 92–95 \\  & chloride (7-5) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\\ \text{R}^{2}=\text{Methyl, Phenyl}\end{array}\) & Solvent-free & 45 & 5–30 min & 75–94 \\
[67] & [Co\({}_{x}\)BIM] (SO\({}_{x}\)B\({}_{2}\)FeBr\({}_{3}\)Cl\({}_{2}\) (0.1 g/1 mmol) & Yes (4) & \(\begin{array}{c}\text{R}^{2}=\text{Methyl, Phenyl}\end{array}\) & Solvent-free & 100 & 10–20 min & 84–90 \\  & Tetrakis(N\({}_{x}\) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\\ \text{T}^{2}=\text{Methyl}\end{array}\) & Solvent-free & 90 & 3–15 min & 90–96 \\
[69] & methylimidammonium & No & \(\begin{array}{c}\text{R}^{2}=\text{Methyl}\end{array}\) & Solvent-free & 90 & 40–85 min & 76–91 \\  & Tetrakis(N\({}_{x}\) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\end{array}\) & & & & \\
[69] &ylmethylmethane & No & \(\begin{array}{c}\text{R}^{2}=\text{Methyl}\end{array}\) & & & & & \\
[70] & Tetrakis(N\({}_{x}\) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\end{array}\) & & & & & \\
[69] &ylmethylmethane & No & \(\begin{array}{c}\text{R}^{2}=\text{Methyl}\end{array}\) & Solvent-free & 90 & 3–15 min & 90–96 \\  & Tetrakis(hydrogen sulfate) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\end{array}\), Heteroary1 & & & & \\
[70] & Tetethanolammonium & Yes (4) & \(\begin{array}{c}\text{R}^{2}=\text{Methyl, NH}_{2}\end{array}\) & Solvent-free & 90 & 40–85 min & 76–91 \\  & acetate ionic liquid (20) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl}\end{array}\) & & & & & \\
[71] & Optimum dihydrogen & No & \(\begin{array}{c}\text{R}^{2}=\text{Methyl, Phenyl}\end{array}\) & Solvent-free & 100 & 1–25 h & 81–96 \\  & Phosphate (10) & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl, Fluoryl, Propyl}\end{array}\) & & & & & \\
[72] & & & \(\begin{array}{c}\text{Cydhesyl}\end{array}\) & & & & & \\
[73] & & & \(\begin{array}{c}\text{R}^{2}=\text{Phenyl,}\end{array}\) & Solvent-free & 60 & 40–80 min & 45–95 \\  & Chloromethyl & & & & & & \\
[74] & & & \(\begin{array}{c}\text{R}^{1}=\text{Aryl, Heteroary1}\\ \text{(24)}\end{array}\) & Water & 100 & 1–25 h & 81–96 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summarized data on the recent synthesis of amidoalkyl naphthols via multicomponent Mannin reaction, catalyzed by homogeneous ionic liquids and deep eutectic solvents (Scheme 3). formation of amidoalkyl naphthols via multicomponent Mannich reaction. The recent literature precedents are summarized in Table 3, Refs. [73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91; 92]. A nanostructured cobalt-containing complex was successfully employed as a catalyst under solvent-free conditions. Excellent yields of 85-95% were achieved in the presence of 5 mol% of the catalyst. However, the recyclability of this catalyst was not revealed [73]. Two magnetic-nanoparticle-supported 2-(((4-(1-aminoethyl)phenyl)imino)methyl) phenols, namely Cu(II) and Zn(II) complexes, represented another class of reusable catalysts for the multicomponent synthesis of amidoalkyl naphthols.