Pyromellitic acid grafted to cross-linked LDH by dendritic units: An efficient and recyclable heterogeneous catalyst for green synthesis of 2,3-dihydro quinazoline and dihydropyrimidinones derivatives

Abstract

In this work, using layered double hydroxide (LDH) inorganic substrate, melamine as binding agent and dendrimer G1 and also pyromellitic acid (PMA) organic catalytic agent a heterogeneous acid catalyst was designed and prepared. After that, the prepared organic-inorganic catalyst was evaluated by various identification techniques such as FTIR, EDX, XRD, TGA, FESEM, and BET, and the results showed that the desired structure was successfully prepared. Also, in order to investigate the efficiency of the LDH@Me-PMA nanocatalyst as an efficient and heterogeneous catalyst, it was used for green and one-pot synthesis of 2,3-dihydro quinazoline and 3,4-dihydropyrimidinone-2-(1H)-ones derivatives. The use of LDH@Me-PMA catalyst led to the synthesis of the desired derivatives with higher efficiency and shorter reaction time than previously reported works. In addition, the prepared LDH@Me-PMA acid catalyst has the ability to be recycled and reused for 5 consecutive periods and has high stability, which is well consistent with the principles of green chemistry.

Keywords: 2,3-Dihydro quinazoline derivatives; 3,4-Dihydropyrimidinone-2-(1H)-Ones derivatives; Layered double hydroxide (LDH); Organic-inorganic catalyst; Pyromellitic acid (PMA).

Scheme 1

LDH@Me-PMA (1) as catalyst for green synthesis of 2,3-dihydro quinazoline and 3,4-dihydropyrimidinone-2-(1H)-ones derivatives in EtOH solvent under reflux conditions.

Scheme 2

Schematic preparation of LDH@Me-PMA nanocomposite (1).

Fig. 1

FTIR spectra of Mg–Al LDH (a), Me-PMA (b), and LDH@Me-PMA (1, c).

Fig. 2

XRD patterns of LDH@Me-PMA nanocomposite (1).

Fig. 3

EDX spectra of LDH@Me-PMA nanocomposite (1).

Fig. 4

FESEM images of MgAl-LDH (a and b) and LDH@Me-PMA nanocomposites (1, c-f).

Fig. 5

TGA curve of the LDH@Me-PMA nanocomposite (1).

Fig. 6

N₂ adsorption–desorption isotherms of LDH@Me-PMA nanocomposite (1).

Scheme 3

The proposed mechanism for the synthesis of 2,3-dihydroquinazoline derivatives.

Scheme 4

Proposed mechanism for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones.

Fig. 7

Reusability of the LDH@Me-PMA nanocomposite (1) in the model reactions.

Fig. 8

FTIR spectra of recycled LDH@Me-PMA nanocomposite (1).

Fig. 9

EDX spectra of recycled LDH@Me-PMA nanocomposite (1).