In recent literature, photoredox catalysis has served as a foundation for novel approaches in organic chemistry (Mohamadpour, 2021a; Mohamadpour, 2023a). The field of photoredox catalysis, which combines metal-promoted reactions with photoredox cycles, is gaining significant attention from both academia and industry (Pinosa et al., 2022). The main focus of research is the use of inexpensive, readily manufactured, and efficient organic dyes to help create novel, powerful, and selective metal-promoted reactions (Gualandi et al., 2021). In this sector, organic dyes must take the place of the commonly employed inorganic complexes that are dependent on Ir(III) and Ru(II). When compared to organic molecules, these compounds are known for their long excited state lifetimes, which may tend toward dynamic quenching. Organic dyes often have shorter lifetimes in the excited state, which is a major obstacle to the development of effective photoredox methods. The scientific community has shown a great deal of interest in a specific class of organic chromophores because of their unique characteristics and effectiveness (Bryden and Zysman-Colman, 2021). One characteristic of the molecules under study is thermally activated delayed fluorescence (TADF), which is only observed in molecules with a tiny energy gap (often less than 0.2 eV) between their lowest two excited states, i.e., S₁ and T₁. Under ambient conditions, the molecules under study undergo reverse intersystem crossing (RISC), aided by a thermally activated pathway from the triplet excited state (T₁) to the singlet excited state (S₁). This results in a delayed fluorescence phenomenon that is commonly observed in systems similar to this one. The present goal is to combine reduced instruction set computing’s (RISC) exceptional efficiency with fluorescence’s great quantum yield. 2012 saw a significant advancement in the field of organic light-emitting diodes (OLEDs) with the release of a basic work by Adachi (Uoyama et al., 2012). This approach covers the efficient usage of dicyanobenzene molecules with suitable photophysical properties as well as their demonstrated application in OLEDs. Similar TADF chromophores have been used in other domains, such as photocatalysis, since these initial discoveries (Yang et al., 2017; Bryden and Zysman-Colman, 2021). The extended singlet excited states arising from TADF and the simplicity with which their redox potentials may be altered make the isophthalonitrile family of chromophores a viable option for organic photocatalyst applications (Speckmeier et al., 2018). 2,4,6-tris(diphenylamino)-5-fluoroisophthalonitrile (3DPAFIPN) is a chemical that is widely used in a number of visible light-triggered synthetic procedures. Intramolecular cyclizations (Flynn et al., 2020; Wu et al., 2020) and the formation of C–C (Cardinale et al., 2020; Donabauer et al., 2020), N–C (Zhou et al., 2020), and P–C (Rothfelder et al., 2021) bonds (Pinosa et al., 2022) are a few examples of these processes.

Because visible light irradiation has a large energy reserve, is inexpensive, and can be used to access sustainable energy sources, it is considered a reliable method for creating organic compounds (Mohamadpour, 2021b; Mohamadpour, 2021c; Mohamadpour, 2022a).

It is expected that dihydropyrimidine structures have potent biological and pharmacological effects (Figure 1). Calcium channel blockers, antihypertensive effects (Sujatha et al., 2006), anticancer (Wisen et al., 2008), anti HIV agent (Heys et al., 2000), antibacterial and antifungal (Ashok et al., 2007), antiviral (Hurst and Hull, 1961), antioxidative (Magerramow et al., 2006), and anti-inflammatory (Bahekar and Shinde, 2004).

To produce 3,4-dihydropyrimidin-2-(1H)-one/thione derivatives, a number of catalysts are employed, including Na₂ eosin Y (Mohamadpour, 2022b), copper (II)sulfamate (Liu et al., 2012), bakers, yeast (Kumar and Maurya, 2007), hydrotalcite (Lal et al., 2012), hexaaquaaluminium (III) tetrafluoroborate (Litvic et al., 2010), TBAB (Ahmed et al., 2009), copper (II) tetrafluoroborate (Kamal et al., 2007), [Btto][p-TSA] (Zhang et al., 2015), triethylammonium acetate (Attri et al., 2017), saccharin (Mohamadpour et al., 2016), caffeine (Mohamadpour and Lashkari, 2018), zirconium (IV)-salophen perfluorooctanesulfonate (Li et al., 2020), H₃ [PW₁₂O₄₀] (Chopda and Dave, 2020), Dioxane-HCl (Choudhare et al., 2021), WSi/A15 (Bosica et al., 2021), H₄ [W₁₂SiO₄₀] (V Chopda and Dave, 2020), Zr(H₂PO₄)₂ (KÜÇÜKİSLAMOĞLU et al., 2010), and GO-chitosan (Maleki and Paydar, 2016). Complex procedures, lengthy reaction times, the use of costly chemicals, and lower yields are just a few of the variables that significantly impact the management and disposal of waste. Moreover, it might be challenging to extract homogeneous catalysts from reaction mixtures. Due to our interest in the development of photocatalytic reactions (Mohamadpour, 2022c; Mohamadpour, 2022d; Mohamadpour, 2023b; Mohamadpour, 2023c; Mohamadpour, 2023d), the current work discusses the use of photocatalysts in the synthesis of heterocyclic compounds, emphasizing the use of environmentally acceptable practices. The investigation indicates that using photo-redox catalysts for halogenated organic dyes is also financially feasible. A potent donor-acceptor (D-A) cyanoarene is employed as an efficient organo-photocatalyst by employing the previously outlined technique.

The primary focus of the investigation was 2,4,6-tris(diphenylamino)-5-fluoroisophthalonitrile (3DPAFIPN) because of its exceptional photophysical and photochemical properties. Organic chemists now have access to a wider range of photocatalysts thanks to the development of dicyanobenzene-based photosensitizers, which demonstrate exceptional photoelectric activity and thermally activated delayed fluorescence (TADF).

The current study has investigated 3DPAFIPN, a new halogenated cyanoarene-based donor-acceptor (D-A) photocatalyst that works by a sequence of visible-light-induced electron transfers. The three-condensation domino Biginelli reaction arylaldehydes with urea/thiourea and β-ketoesters are used in this procedure. In addition, this process employs blue LED, a sustainable and environmentally friendly energy source, in a room-temperature, ethanol medium as a green solvent. Regardless of the timely and effective completion of all obligations and adherence to the agreed-upon budget.

The reaction was optimized in the current study using a 3 mL ethanol medium containing 1.0 mmol of benzaldehyde, 1.5 mmol of urea, and 1.0 mmol of ethyl acetoacetate. Without the aid of a photocatalyst, a trace quantity of 4j was produced for 20 min at room temperature in the presence of 3 mL of EtOH. The pace of reaction was enhanced by the inclusion of photocatalysts. The compounds include 3DPAFIPN, 3DPA2FBN, DCB, DCA, DCN, and diphenylamine, as indicated by the data in Figure 2

The present technique can create 4j with varying yields. The aforementioned data showed that 3DPAFIPN’s operational efficacy has increased. A reaction with 0.2 mol% 3DPAFIPN yielded a 97% yield, based on the data in Table 1, entry 2. Results for solvent-free conditions, EtOAc, DMSO, toluene, H₂O, EtOH, MeOH, CHCl₃, CH₃CN, THF, and are displayed in Table 2. In the presence of EtOH, the reaction was demonstrated to have a notably enhanced rate and subsequent yield. Based on the data in Table 2, especially entry 5, a 97% yield was achieved. Table 2 lists the light sources that have been used in studies to assess the impact of blue light on production. In the assessment that was conducted without the use of an illumination tool, the 4j was discovered in extremely little amounts. The results of this investigation demonstrate that 3DPAFIPN and visible light are essential for the effective synthesis of product 4j. The top designs were determined using blue light-emitting diode (LED) intensities of 3 W, 5 W, and 7 W. The results of the investigation showed that the greatest results were obtained when blue light-emitting diodes (LEDs) with a 5 W power output were used. The outcomes of studies conducted on a range of substrates under optimal conditions are displayed in Table 3; Scheme 1 (and also Supplementary Table S1). The benzaldehyde substituent has no effect on the reaction’s result (Table 3). Both polar and halide substitutions were permitted in this reaction. In the current state of the reaction, reactions involving both electron-donating and electron-withdrawing functional groups are acceptable. Aromatic aldehydes that are ortho, meta, and para-substituted have a very high yield potential. The reactions of methyl and ethyl acetoacetate are comparable. Urea and thiourea have comparable reactivities.

Table 4 presents the turnover number (TON) and turnover frequency (TOF) as objective value measures. Yield/Amount of Catalyst (mol) and Yield/Time/Amount of Catalyst (mol) are two distinct forms of yield that are commonly expressed as TON and TOF, respectively, in academic literature. The catalyst performance may be enhanced by higher turnover number (TON) and turnover frequency (TOF) values as they need less catalyst to provide the required yields. A TOF of 97 and a TON of 485 are considered high values for 4j. In relation to 4s, a TON of 480 is likewise regarded as high, although a TOF of 96 is deemed excessive. The aim of the inquiry was to reduce reaction times, increase production, and utilize the fewest amount of catalysts.

We have green photosynthesized 3,4-dihydropyrimidin-2-(1H)-one/thione derivatives from arylaldehydes, β-ketoesters, and urea/thiourea by means of the radical-induced Biginelli reaction. In the current work, a new halogenated dicyanobenzene-based photosensitizer; 3DPAFIPN was employed as a donor-acceptor (D-A) photocatalyst. It works by causing a sequence of electron transfers that are triggered by visible light. Blue light-emitting diode (LED) technology has been demonstrated to generate a sustained energy-generating mechanism at room temperature and in an air environment when used in an ethanol medium. The suggested method has significant advantages for the field of chemical synthesis. Fast reaction times, the removal of hazardous solvents, higher product yields, streamlined reaction mechanisms, and the utilization of a sustainable energy source are some of these benefits. The separation method does not need chromatography. By preserving the result, it is possible to accelerate a multigram-scale reaction of model substrates. As a result, the method may be used in an environment that promotes long-term ecological and financial sustainability.