Efficient synthesis of ethyl–piperazinyl quinolinyl-(E)-chalcone derivatives via Claisen–Schmidt reaction by using TiO₂-BPTETSA catalyst

A new titanium nanomaterial based sulfonic acid catalyst was prepared and exhibited efficient catalytic activity for the synthesis of (E)-3-(2-(4-ethylpiperazin-1-yl)quinolin-3-yl)-1phenylprop-2-en-1-one derivatives under solvent free conditions. Briefly the catalyst was synthesized by refluxing a mixture of nitric acid activated titanium dioxide, 3-mercaptochloropropyl and triethylene tetramine followed by filtration. This is a facile and environmentally benign method for preparation of the catalyst. The morphological properties of the catalyst was characterized by FT-IR, XRD, TEM, SEM, BET and Raman spectroscopy. The starting substrate 2-(4-ethylpiperazin-1-yl) quinoline-3-carbaldehyde (1) was synthesised from 2-chloro-3-formyl quinoline and an excess of 1-ethylpiperazine. The X-ray structure showed that the ethyl–piperazinyl N atom is attached to the aromatic ring and the dihedral angle between the mean planes of ethyl–piperazinyl ring atoms N (3)-C-(3)-N (2) has a geometric parameter of 117.9 (4) Å thereby confirming the identity of the crystal structure. The one-pot Claisen–Schmidt reaction containing 1 and acetophenone derivatives were refluxed to produce chalcone derivative 3a-3n of yield 85–97%. They were characterised by IR, ¹H NMR, ¹³C NMR and MS-TOF whilst 3 m included 90° DEPT, 135° DEPT, COSY, NOSEY, HSQCE and HMBC. High yield, simple methodology and short reaction time were some of the advantages of this methodology whilst a decrease of a mere 10% in catalytic activity, in five cycles, makes it cost effective for any possible large scale production. Furthermore (E)-1-(1-hydroxynaphthalen-2-yl)-3-(2-(4-ethylpiperazin-1-yl)quinolin-3-yl) prop-2-en-1-one was used in molecular docking studies with bovine serum albumin protein binding was located in subdomain II A of BSA containing the amino acid residues ARG-209, LYS-212, ALA-213, VAL-216, PHE-226, ALA-229, SER-232, LYS-233 and THR239.