Pyrimidine compounds continue to attract great interest in the field of organic synthesis due to
their various chemical and biological applications observed, especially in recent times. As a
result, this review covering some periods from 1957 to 2021 has been prepared to discuss some
of the structural pathways of these compounds as well as some of their interactions and
applications.

Thiazolopyrimidnes are considered one of the most interesting classes in heterocyclic chemistry
due to their pharmaceutical importance. Herein, we report the synthesis of some new heterocyclic
compounds containing thiazolopyrimidine starting from compound (1) which was previously
prepared in literature. The starting compound was allowed to react with different alkylating
agents such as chloroacetone, chloroacetyl chloride, and phenacyl bromide to afford derivatives
(2-4). Compound (5), benzylidene derivative, was obtained by the reaction of compound (2) with
benzaldehyde while amino-dicarbonitrile compound (6) can be obtained by the reaction of
compound (5) and malononitrile. Acetylation of amino group in compound (6) with chloroacetyl
chloride led to formation of compound (7). Nucleophilic substitution of chlorine in compound
(7) by aniline gave compound (8) which further subjected the Munich reaction to form compound
(9). All new synthesized compounds were characterized using different elemental and spectral
analysis.

Starting from 3-cyano-4,6-distyrylpyridin-2(1H)-thione (1), the compound N-(4-
chlorophenyl)-2-((3-cyano-4,6-distyrylpyridin-2-yl)thio)acetamide (2) was prepared.
Compound (2) underwent cyclization upon heating in ethanolic sodium ethoxide solution to
give the corresponding cyclized form 3-amino-N-(4-chlorophenyl)-4,6-distyrylthieno[2,3-
b]pyridine-2-carboxamide (3). The elemental analyses and spectroscopic data of compounds
(2) and (3) are in agreement with their proposed structures. Their insecticidal activity against
cowpea aphid, Aphis craccivora Koch, was studied. The results of insecticidal activity for
compounds (2) and (3) against the nymphs and the adults of the tested insects exhibited that
compounds (2) and (3) have a higher insecticidal activity than that of acetamiprid, a reference
insecticide, after 24 h of treatment.

Heterocyclic compounds with effective solid-state luminescence
offer a wide range of uses. It has been observed that combining
pyrimidine and indole moieties in a single molecule can enhance material
behavior dramatically. Here, different heterocyclic compounds with
indole and pyrimidine moieties have been synthesized effectively, and
their structures have been validated using NMR, IR, and mass
spectroscopy. The photoluminescence behavior of two substances was
investigated in powder form and solutions of varying concentrations.
After aggregation, one molecule displayed a redshifted luminescence
spectrum, whereas another homolog showed a blueshift. Thus, density
functional theory calculations were carried out to establish that
introducing a terminal group allows modifying of the luminescence
behavior by altering the molecular packing. Because of the non-planarity,
intermolecular interactions, and tiny intermolecular distances within the
dimers, the materials demonstrated a good emission quantum yield (Φem) in the solid state (ex. 25.6%). At high temperatures, the
compounds also demonstrated a stable emission characteristic.

Schiff bases represent an essential class in organic
chemistry with antitumor, antiviral, antifungal, and antibacterial
activities. The synthesis of Schiff bases requires the presence of an
organic base as a catalyst such as piperidine. Base-free synthesis of
organic compounds using a heterogeneous catalyst has recently
attracted more interest due to the facile procedure, high yield, and
reusability of the used catalyst. Herein, we present a comparative study
to synthesize new Schiff bases containing indole moieties using
piperidine as an organic base catalyst and Au@TiO2 as a heterogeneous
catalyst. In both methods, the products were isolated in high yields and
fully characterized using different spectral analysis techniques. The
catalyst was reusable four times, and the activity was slightly decreased.
The presence of Au increases the number of acidic sites of TiO2,
resulting in CO polarization. Yields of the prepared Schiff bases in the presence of Au@TiO2 and piperidine were comparable.
However, Au@TiO2 is an easily separable and recyclable catalyst, which would facilitate the synthesis of organic compounds without
applying any hazardous materials. Furthermore, the luminescence behavior of the synthesized Schiff bases exhibited spectral shape
dependence on the substituent group. Interestingly, the compounds also displayed deep-blue fluorescence with Commission
Internationale de l’Éclairage (CIE) coordinates of y < 0.1. Thus, these materials may contribute to decreasing the energy
consumption of the emitting devices.

There has been evidence of non-typical fluorescence activities in thiadiazole and oxadiazole derivatives. Also,
some coumarin compounds with tunable luminescence properties via controlling the molecular structure and its
aggregation have been recently reported. As a result, our effort concentrated on integrating these moieties in
order to improve the applicability of the target compounds through easy synthetic schemes. All the synthesized
derivatives underwent extensive spectrum analysis, including NMR, FT-IR, and mass spectroscopy. DFT calculations,
UV–visible, and luminescence spectroscopy were used to study the photophysical characteristics of three
compounds having coumarin luminescent core integrated with the thiadiazole, oxadiazole, or hydrazinecarbothioamide.
We found that manipulating the packing of a compound under specific conditions (e.g., the solid state
or moderate solution concentration of compounds containing the heterocyclic substituent “thiadiazole or oxadiazole”)
can trigger processes related to the way the molecules interact, resulting in the appearance of dual or
multiple fluorescence bands that cover the full visible range. Additionally, we deduced that the intriguing white
emission from a single component might be generated by modifying the degree of molecular aggregation to
balance the relative band intensities at short and long wavelengths. Long-wavelength emission arises from
aggregated molecules whereas short-wavelength emission results from single molecules. It is evident that this
balance is feasible in both the solid form of the thiadiazole derivative and 1 × 10–5 mol L–1 solution of the
oxadiazole derivative. Hence, this research proposes an easy method for creating the intriguing white-light
emission from a single component.

The powder form of the new indole derivative 4-(((3-chloro-1H-indol-2-yl) methylene) amino) phenol [Indol-
4Ap] was synthesized and subsequently converted to a thin film [Indol-4Ap]TF using the Sol-Gel spin coating
technique. Numerous characterization techniques, including Fourier transform infrared (FTIR), nuclear magnetic
resonance (NMR), X-ray diffraction (XRD), and ultraviolet–visible (UV–Vis) optical spectroscopy were used to
characterize [Indol-4Ap]TF. Additionally, using density functional theory (DFT), optimization tvia TD-DFTD/
Mol3 and Cambridge Serial Total Energy Bundle (TD-FDT/CASTEP) was developed. The DFT calculations
accurately matched the observed NMR and FTIR spectra and validated the molecular structure of the examined
materials. The average crystallite size of [Indol-4Ap]TF, as determined by XRD calculations, is 12.02 nm. The
optical properties of the films were determined using optical absorbance spectrophotometric measurements in
the 200–800 nm wavelength range. The optical energy bandgaps computed using Tauc’s equation for the [Indol-
4Ap]TF are 3.152 and 2.751 eV, respectively. Whereas the [Indol-4Ap]iso has a bandgap of 3.074 eV as determined
by TD-DFT/DMol3. The optical characteristics predicted by CASTEP in TD-DFT are in excellent agreement
with the experimental values. The investigated

In the recent years, interest in the synthesis of diclofenac derivatives has increased due to their excep- tional biological activity. We present here the synthesis of some novel diclofenac derivatives through simple synthetic procedures, where the acylation of carbohydrazide compound 1 with chloroacetyl chlo- ride in dioxane produced the compound 2 . Chloroacetohydrazide compound 2 was further subjected to nucleophilic substitution reactions using different nucleophiles such as: hydrazine hydrate, thiosemicar- bazide and p -aminobenzenesulfonamide to give the corresponding derivatives 3-5 , respectively. More- over, the reaction of the hydrazinyl compound 3 with active hydrogen species such as: ethyl acetoacetate and acetyl acetone in refluxed ethanol provided the corresponding pyrazolone derivatives 6 and 7 , re- spectively. Furthermore, the reaction of previously reported diclofenac ester 8 with 1,2-diaminoethane gave the amino derivative 9 . Finally, condensation reaction of the latter compound with benzaldehyde in dioxan furnished the corresponding Schiff’s base compound 10 , while its acylation with chloroacetyl chloride in dioxan produced 11 . Different spectral (IR, NMR and Mass) and elemental analysis techniques were utilized to explore the structure of the synthesized compounds. All the synthesized compounds were tested for their in-vitro antibacterial activity against different strains of bacteria showing satisfac- tory results, and molecular docking study was performed to investigate the mode of action.