The synthesis of chromenonitriles remains largely underexplored, primarily due to the limited availability of suitable substrates and the generally unsatisfactory yields of existing methods. Herein, we report a new method...

A dehalogenative sulfonylation of 4,5-dihalo-pyridazin-3(2H)-ones with arylsulfonyl hydrazides under mild conditions for the synthesis of 4-arylsulfonyl pyridazin-3(2H)-ones is developed for the first time. The transformation also avoids the use of transition-metal catalysts, oxidants, and reductants. Notably, due to the relatively low activity of the C-4 site of pyridazin-3(2H)-ones, there are few reports on functionalization reactions at this position before, especially on sulfonylation. Thus, this strategy is of great significance to expand both the synthetic range of potential functional pyridazin-3(2H)-one compounds and the application scope of arylsulfonyl hydrazines as a kind of multifunctional reagents.

Carbon quantum dots (CQDs), as an emerging class of inorganic fluorescent nanomaterials, have demonstrated significant potential in the field of chemical sensing. This study reports the successful synthesis of nitrogen-doped CQDs via a one-step hydrothermal method using green and economical lactic acid (LA) and urea as precursors, with systematic optimization of the synthetic process. The results indicate that the as-prepared CQDs possess a nearly spherical morphology with an average particle size of approximately 3.09 nm, along with excellent water solubility and stable fluorescence properties. When applied as a fluorescent probe for Fe3+ detection, the CQDs can exhibit high selectivity and sensitivity, achieving a detection limit as low as 2.9 & times; 10-7M. In addition, the recovery rate of the probe applied in actual water sample analysis is satisfactory, ranging from 94.70% to 106.90%. Through investigation into the detection mechanism, it is confirmed that the fluorescence quenching is a synergistic process dominated by both the inner filter effect (IFE) and static quenching. For comparative purposes, three additional types of CQDs were synthesized by using glycolic acid (GA), glycine (Gly), and citric acid (CA) as carbon sources. In the combination of experimental characterization with density functional theory (DFT) calculations, the potential structures of surface fluorophores formed from different precursors were thoroughly investigated also. Therefore, this work not only provides an experimental basis for the preparation and application of high-performance lactic acid-based CQDs fluorescent sensors, but also deepens the understanding of CQDs structures through multi-precursor comparison and theoretical modeling.

Three Schiff base fluorescent probes 3a–3c with N-heterocyclic structure were designed and synthesized by using the reaction of 4-diethylaminosalicylaldehyde with different N-heterocyclic amines, such as 2-aminobenzimidazole, 2-aminobenzothiazole, and 2-amino-6-methylpyridine. Compound 3a exhibited excellent selectivity towards Hg2+, with a detection limit of 3.21 × 10−7 M and a response time of only 30 s. It could be used as a fluorescent probe for detecting Hg2+. Meanwhile, compounds 3b and 3c exhibited excellent selectivity towards Zn2+, with detection limits of 1.61 × 10−7 M and 2.03 × 10−7 M, respectively, and response times of only 30 s. They could serve as fluorescent probes for detecting Zn2+. Using probe 3a for Hg2+ as an example, the detecting mechanism was further elucidated through 1H NMR, ESI-MS testing, and DFT calculation analysis. For compound 3a, the coordination stoichiometry between compound 3a and Hg2+ was verified to be 1:1 through a Job’s plot. After coordination with Hg2+, the molecular rigidity of compound 3a was enhanced, which inhibited the non-radiative decay process and led to the closure of the excited-state intramolecular proton transfer (ESIPT) effect. At the same time, the fluorescence intensity was significantly increased through the chelation-enhanced fluorescence (CHEF) mechanism, which was confirmed by density functional theory (DFT) calculations. In addition, compounds 3a–3c were successfully applied in practical water samples and test strips for the detection of Hg2+/Zn2+.

To investigate the influence of benzimidazole units on the properties and application of soluble polyimides (PIs), three cyano-containing triphenylmethane- (TPM-) and benzimidazole-based co-polyimides (co-PIs, namely BPADA-CN-NH, ODPA-CN-NH and 6FDA-CN-NH) and three cyano-containing TPM-based homo-polyimides (homo-PIs, namely BPADA-CN, ODPA-CN and 6FDA-CN) were prepared and compared. Results show that the three co-PI films possess better physical properties, such as higher glass transition temperature (Tg) and mechanical properties, than those of their corresponding homo-PI films without benzimidazole units due to the rigidity of benzimidazole units and the formation of intermolecular H-bonding. Another unique feature is that after BPADA-CN-NH reacts with the fluoride ion (F-), the resulting BPADA-CN-NH plus F- system (BPADA-CN-NHF) can be developed into a ratiometric sensor suitable for the detection of trace water in various organic solvents such as DMSO, THF and DMF by means of UV-vis absorption spectra and color change. The low water content of three solvents can be quantitatively detected by utilizing the good linear relationship between the ratio of the intensities of the two UV-vis absorption bands and the low water content range. The detection limits (DLs) of BPADA-CN-NHF for water are calculated to be as low as 0.00183 vol% in DMSO, 0.00267 vol% in THF, and 0.00433 vol% in DMF. The sensing mechanism based on F--induced deprotonation of BPADA-CN-NH to BPADA-CN-NHF, followed by re-protonation with water, was confirmed by 1H NMR studies. Finally, the BPADA-CN-NH film was also used for visual detection of water in CH3CN.

A dehalogenative sulfonylation of 4,5‐dihalo‐pyridazin‐3(2 H )‐ones with arylsulfonyl hydrazides under mild conditions for the synthesis of 4‐arylsulfonyl pyridazin‐3(2 H )‐ones is developed for the first time. The transformation also avoids the use of transition‐metal catalysts, oxidants, and reductants. Notably, due to the relatively low activity of the C‐4 site of pyridazin‐3(2 H )‐ones, there are few reports on functionalization reactions at this position before, especially on sulfonylation. Thus, this strategy is of great significance to expand both the synthetic range of potential functional pyridazin‐3(2 H )‐one compounds and the application scope of arylsulfonyl hydrazines as a kind of multifunctional reagents.

Dual-state emission (DSE) fluorophores offer unique advantages in fluorescence applications by maintaining well emission intensity in both solution and solid state, overcoming the limitation of aggregation-caused quenching for conventional dyes. Herein, a novel and efficient strategy to design good-performance DSE fluorophores is to construct cyanopyridine core by using simple malononitrile sulfone compounds. As a common heterocycle, cyanopyridine is relatively less commonly used for the design of DSE molecules. Thus, integrating the DSE molecular design principles, we developed a desulfonylative cyclization protocol to access trisubstituted cyanopyridine (TCP) scaffolds. The TCP 3a-3d synthesized by this method have good DSE properties and can exhibit strong blue-violet fluorescence in solution and in the solid state, which may be attributed to the synergistic intramolecular charge transfer (ICT) and the restricted rotation. Based on the extended design of cyanopyridine structural molecules for DSEphores, the TCP 3a is functioned as a multi-analyte sensor for nitroaromatic compounds (NACs) with a synergistic mechanism of photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET) and hydrogen bonding, achieving a detection limit of 10-7 M and enabling portable teststrip visualization. The feasibility of testing actual water samples demonstrates the potential of the TCP 3a to be a practical sensing device.

In this work, a series of diaminodicyanoquinodimethanes (DADQ) were designed and synthesized by using tetracyanoquinodimethane (TCNQ) and secondary amines as reactants. They are found to be novel D-pi-A-type molecules with dual-state emission (DSE) and can be applied to pH detection. For probe T4, when the pH value is greater than 2.6, T4 is a yellow solution in THF and shows green fluorescence under ultraviolet light. As the pH value decreases, the fluorescence intensity gradually weakens and the yellow solution slowly becomes lighter. When the pH value is lower than 0.8, the fluorescence intensity approaches the quenched state, and the yellow solution is nearly colorless. No significant interference with pH detection has been observed in the presence of various metals and anions. In addition, T4 can be used for real-time and reversible pH sensing. Finally, the T4 probe has not only been used for the detection of pH value in solutions, but also has been successfully made into portable test strips for visual detection.

In this work, by using the 5,6-difluorobenzothiadiazole structural unit as an electron acceptor (A), and introducing different electron donor (D) groups at the 4,7-positions of the thiadiazole through the Sonogashira coupling reaction between 4,7-dibromo-5,6-difluoro-benzo[c][1,2,5]thiadiazole and aryl acetylenes, a series of D-pi-A-pi-D type fluorescent molecules 4a-4 f with dual-state emission (DSE) effect were synthesized. Notably, compound 4c exhibits aggregation-induced emission (AIE) due to its dimethylamino rotor. At the same time, the presence of nitrogen atoms in these benzothiadiazole molecules may make compounds 4a-4 f coordinate with Fe3+ or Fe2+, leading to a decrease in fluorescence intensity. Among them, probe 4b has the limit of detection (LOD) of 3.20 x 10(-7) M for Fe2+ and 3.20 x 10(-7) M for Fe3+; probe 4e has the LOD of 2.50 x 10(-7) M for Fe2+ and 2.65 x 10(-7) M for Fe3+. Furthermore, these probes can be applied to portable test strips for detecting Fe3+ or Fe2+ in actual water samples.

Dual-state emission (DSE) fluorescent molecules have become the preferred type in designing sensing fluorescent molecules due to the virtue of their bright emission in both solid and liquid states. In this study, five D-A molecules were successfully designed and synthesized according to the design concept that structural modification of D-A molecules can lead to DSE molecules. Among them, the balance between the electron donor with a strong electron donation capacity and the twisted conformation in the whole molecule makes the compounds 3c-3e DSE molecules with excellent optical performances, showing significant solvatochromic effects and large Stoke shifts. In addition, the feasibility of the sulfone unit as an electron acceptor in the D-A structure is also verified, extending the application of sulfone group in the field of fluorescence. Interestingly, the fluorescence of 3c can exhibit sensitive and selective quenching of nitro aromatic compounds (NACs) under the synergistic mechanism of fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET), with LOD as low as 10-8 M and KSV as high as 104 M-1. Furthermore, the selective, efficient, and sensitive detection of NACs by DSE fluorescent molecule 3c in real aqueous samples and loaded on test strips has demonstrated the potential of its practical applications.

A series of 2-substituted 4H-chromen-4-ones 3a-3h containing triphenylamine or N-phenylcarbazole on the benzene ring were synthesized for the first time via the Suzuki coupling reaction. The photophysical properties of the compounds and their relationship to the structure of the compounds were investigated by methods such as spectroscopic analysis, single-crystal analysis, and theoretical calculations. The systematic results indicate that compounds 3a-3h have intramolecular charge transfer (ICT), aggregation-induced emission (AIE), and dual-state emission (DSE) effects with a wide range of fluorescence emission wavelengths (421-618 nm), showing the potential to be developed into a full-color fluorophore.

A novel one-pot two-step three-component reaction synthesis strategy for the efficient assembly of tetrasubstituted furan-based Schiff base compounds, creating a bioactive compound library, is reported. Under mild reaction conditions, a total of 39 target products, including 35 novel compounds, can be concisely obtained in moderate to excellent yields, demonstrating broad functional-group tolerance. Notably, this approach obviates the need for expensive metal catalysts and eliminates the purification process for intermediate compounds, thereby streamlining the synthetic process and aligning with green chemistry principles. What's more, antimicrobial activity assays of the synthesized compounds also provide a preliminary insight into their structure-activity relationships, laying a foundation for potential pharmaceutical applications and subsequent structural optimization.

A novel method for the efficient and straightforward synthesis of tetrasubstituted furans is presented, employing a base-catalyzed reaction of α-hydroxy ketones and cyano compounds. The reaction proceeds under relatively mild conditions, utilizes readily available starting materials, and exhibits good functional group tolerance and high yields. Notably, this reaction obviates the need for expensive metal catalysts and introduces crucial functional groups such as amino and cyano moieties. Furthermore, it avoids the prerequisite functionalization of substrates, thereby enhancing atomic economy.

An unprecedented nickel-catalyzed [2 + 2 + 2] cycloaddition that enables efficient construction of fused pyridine frameworks with allyl boronate was reported. This transformation is proposed to occur through a mechanism involving aza-nickelacyclopentadiene intermediates, wherein the boryl group of the allyl boronate plays a critical role in enabling the following cyclization via the control experiments. This work not only expands the structural diversity accessible via transition-metal-catalyzed [2 + 2 + 2] cycloadditions but also showcases the untapped potential of unsaturated substrates in cycloaddition reactions.

Mercury is a highly toxic and non-degradable heavy metal pollutant that poses great harm to human health and the ecological environment. Two novel carbazole based thioacetal fluorescent probes 4a and 4b for highly sensitive and selective detection of Hg2+ have been designed and synthesized. Though both probes 4a and 4b can detect Hg2+ through thioacetal deprotection reaction, due to the difference in structural stability and the AIE effect of probe 4a, probe 4a has higher selectivity and sensitivity, with a detection limit as low as 5.1 × 10-8 M and a response time of approximately 25 s. In addition, probe 4a can detect Hg2+ under the solvent systems with high water content, thus we have successfully applied probe 4a to the detection of Hg2+ in actual water and soil samples, and used it as test strips.

This Special Issue, entitled “Advances in Organic Synthesis in Pharmaceuticals, Agrochemicals and Materials”, offers a comprehensive overview of the latest progress and multifaceted applications in organic synthesis [...]

Employing a tandem reaction with 100% atom economy, a series of novel 3-cyanopyridine derivatives were synthesized from benzopyranonitriles and pyrrolidines under mild and metal-free conditions, promoted by sodium hydroxide, achieving yields up to 97%. The mechanism of this novel tandem reaction was confirmed by DFT calculations. These products exhibit aggregation-induced emission (AIE) and dual-state emission (DSE) effects due to restricted intramolecular motion (RIM) and a distorted structure resulting from the existence of a dihedral angle in the molecular structure. Notably, different 3-cyanopyridine compounds can be applicable for the "turn-off" detection of Fe3+/Cu2+ and various nitroaromatic compounds (NACs). Furthermore, these molecules have good antibacterial activity against Escherichia coli and Staphylococcus aureus, providing a novel strategy for the synthesis of new antimicrobial agents.

Using 5-methyl salicylaldehyde (2) as a reactant to react with different amines, 2-aminobenzimidazole (1a), 2-aminobenzothiazole (1b), and 2-aminopyridine (1c), respectively, three types of Schiff base fluorescent probes 3a–3c were designed and synthesized for selective detection of Al3+ in aqueous media. The structure of the compounds was acquired by 1H NMR, 13C NMR, and X-ray single-crystal diffraction. Furthermore, their photochromic and fluorescent behaviors have been investigated systematically by fluorescence spectra. Compounds 3a–3c can exhibit high selectivity, sensitivity, and anti-interference properties towards Al3+ in aqueous media. Among them, the limit of detection (LOD) of probe 3b for Al3+ is 2.81 × 10−7 M. Notably, the response times of probes 3a–3c for Al3+ are 90 s, 80 s, and 80 s, respectively, which are much faster than most previously reported probes. The coordination stoichiometry between compounds 3a–3c and Al3+ has been verified to be 1:1 through the Job’s plot. After coordination with Al3+, the C=N isomerization of compounds 3a–3c is inhibited, leading to the closure of the excited state intramolecular proton transfer (ESIPT) effect. At the same time, the fluorescence intensity is significantly increased through chelation-enhanced fluorescence mechanism (CHEF), which is confirmed by density functional theory (DFT) calculations. In addition, probes 3a–3c can be potentially applied in the selective and high-precision detection of Al3+ in environmental systems.

Recently, the construction of the trisubstituted olefin-type probe molecules has elicited the attention of many researchers. However, the synthesis of the trisubstituted olefin-type probes containing two N-heterocycles simultaneously has been rarely reported. In this study, starting from the inexpensive mucobromic acid 1 and N-heterocyclic compound 2, we first utilized a simple one-step reaction to synthesize a series of trisubstituted olefin-type compounds 3 simultaneously bearing with the structure of two N-heterocyclic rings in the absence of transition metal catalysts with a yield of 62–86%. The optimal reaction conditions were systematically explored, and the structure of the obtained compounds 3 were well characterized with 1H NMR, 13C NMR, X-ray single-crystal and HR-MS. The preliminary observation showed that, in the presence of base, mucobromic acid 1 reacts as its ring-opening structure, and the successive nucleophilic substitution reaction and Michael addition reaction can generate the target product 3. Considering that the aldehyde group in the molecular structure of the trisubstituted olefin-type compounds 3 may react with malononitrile, we carried out some relevant investigations so as to realize the visual detection of malononitrile. Interestingly, among the products, compounds 3a–3c can be prepared in portable test strips through a simple process and used to achieve the naked-eye detection of malononitrile in environmental systems as designed.

An efficient and operationally simple method for the synthesis of α-acyloxy ketones through the readily available 2-methylimidazole-promoted reaction of α-hydroxy ketones and anhydrides is developed. In the reaction, the anhydrides act as both a substrate and a solvent. The new method features good substrate tolerance, mild reaction conditions, readily accessible starting materials, and excellent yields, providing facile and green access to the targets. Importantly, the reaction also avoids the use of reagents with pungent odors, such as pyridine, in traditional esterification, which may promote the development of organocatalysis using nitrogen-containing heterocyclic compounds as catalysts.