5-Chlorosalicylaldehyde CAS 635-93-8

(1) Synthesis of antibacterial drugs
This substance is a key intermediate in the synthesis of antibacterial agents. For example, through its condensation reaction with amine compounds, Schiff base compounds with broad-spectrum antibacterial activity can be generated. Research has shown that the introduction of chlorine atoms enhances molecular lipophilicity, making it easier for them to penetrate bacterial cell membranes and disrupt bacterial metabolic pathways. Patent WO2019/054328 reports a quinolone derivative containing a 5-chlorosalicylaldehyde structure, with an inhibitory concentration as low as 0.5 μ g/mL against Staphylococcus aureus.

(2) Research and development of anti-inflammatory drugs
This compound can serve as a precursor for the synthesis of nonsteroidal anti-inflammatory drugs (NSAIDs). Its aldehyde group can react with active groups such as aminoacetic acid to form a molecular skeleton with cyclooxygenase-2 (COX-2) inhibitory activity. Preclinical studies have shown that such derivatives can significantly reduce the expression levels of inflammatory factors TNF - α and IL-6.

(3) Anti tumor drug design
The metal complexes involved in the construction exhibit potential anti-tumor activity. The complex formed with copper (II) can exert its effects by inducing tumor cell apoptosis and inhibiting angiogenesis. In vitro experiments showed that the IC50 value of the complex for HeLa cells was 8.2 μ M, and its toxicity to normal cells was low.
Antiviral Research
(4)Recent research (J. Med. Chem., 2022, 65 (8)): 5632-5640) found that 5-chlorosalicylaldehyde derivatives can inhibit the activity of SARS CoV-2 main protease (Mpro), providing a new direction for the development of anti COVID-19 drugs.

(1) Development of fungicides
As a key intermediate of benzoyl fungicides, 5-chlorosalicylaldehyde can be synthesized into a highly efficient new fungicide against gray mold and powdery mildew by introducing different substituents. For example, Fluxapyroxad, developed by Bayer AG in Germany, contains similar structural units and has an EC50 value between 0.1-1.0 mg/L.
(3) Insecticide synergist
As a synergist for pyrethroid insecticides, the aldehyde group of 5-chlorosalicylaldehyde can form intermolecular hydrogen bonds with insecticide molecules, delaying their photolysis rate. Field experiments have shown that the addition of this enhancer can extend the effectiveness period of insecticides to over 28 days.

(1) Synthesis of Functional Dyes
The azo dye generated by the condensation of this substance with aniline compounds has excellent light and wash fastness. For example, CI Reactive Red 195 contains this structural unit, and its dyed fabric still has a color fastness of 4-5 levels after 200 hours of sun exposure.

(2) Construction of fluorescent probes
The synergistic effect of its hydroxyl and chlorine atoms causes the related derivatives to exhibit strong green fluorescence under ultraviolet light (λ em=525 nm). By modifying the recognition groups, fluorescent sensors with high selectivity for metal ions such as Fe ³ ⁺ and Cu ² ⁺ can be prepared, with a detection limit of up to nM.
(3) Thermal sensitive color changing material
By combining with electron donors such as crystal violet lactone, reversible thermochromic materials can be prepared. Temperature changes induce intermolecular charge transfer, achieving reversible color transition between colorless and blue purple, and applied in the field of intelligent packaging.

(2) Food seasoning
As a food grade spice, its chlorinated derivatives can simulate the natural nutty aroma and are used for flavoring baked goods and dairy products. The European Food Safety Authority (EFSA) has approved its use limit in specific foods (≤ 5 mg/kg).
(3) Development of antioxidants
Its phenolic hydroxyl structure endows it with antioxidant activity, and when combined with vitamin E, it can significantly enhance the oxidative stability of edible oil. Research has shown that adding 0.02% of this antioxidant can extend the shelf life of soybean oil by 60%.

(1) Spectral analysis reagents
As a chromogenic reagent for UV visible spectrophotometry, its aldehyde group reacts with primary amines such as amino acids to form Schiff base, which has characteristic absorption at λ max=430 nm and a detection sensitivity of 0.1 μ g/mL.
(2) Chromatographic stationary phase
By using chemical bonding technology to fix it on the surface of silica gel, a gas chromatography stationary phase with high selectivity for chlorinated organic compounds can be prepared. When separating chlorinated benzene compounds, the theoretical number of trays exceeds 5000/m.

(3) Electrochemical sensor
Modified on the surface of glassy carbon electrode, an electrochemical sensor with high sensitivity to dopamine can be constructed. At pH 7.0, the detection linear range is 1.0 × 10 ⁻⁷~1.0 × 10 ⁻⁴ M, with strong anti-interference ability.

(2) Photocatalytic degradation
As a modifier for semiconductor photocatalysts, it can enhance the absorption of materials such as TiO ₂ in the visible light region. Research has shown that TiO ₂ modified with it increases the degradation rate constant of methylene blue by 3.8 times.
(3) Air pollutant detection
The fluorescent products generated by the reaction with ozone can be used for real-time monitoring of O3 concentration in the atmosphere. The prototype portable detector has achieved detection accuracy at the ppb level.

(1) Energy storage materials
As an electrolyte additive for lithium-ion batteries, its chlorinated structure can improve the stability of SEI film and extend the battery cycle life to over 1500 times (capacity retention rate>80%).
(2) 3D printing materials
By blending with photosensitive resin, 3D printing materials with self-healing function can be prepared. Its dynamic aldehyde crosslinking network enables the material to recover 85% of its mechanical properties within 24 hours after damage.

(3) Biological imaging probe
By labeling fluorescent groups, biological imaging probes targeting mitochondria can be constructed. Cell experiments showed that the response time of the probe to changes in mitochondrial membrane potential in live cells was 2-5 seconds.

In the photochromic compounds of lactone type, the electronic effect of chlorine atoms can regulate the rate and quantum yield of photoisomerization reactions. For example, the photoresponse speed of 5-chlorinated derivatives is 20% faster than the unsubstituted system, which is due to the regulation of molecular orbital energy levels by the chlorine atom.

In the design of antibacterial drugs, the electron-withdrawing effect of chlorine atoms can enhance the interaction between the molecule and the active center of bacterial enzymes. For instance, the inhibitory activity of the 5-chloro salicylaldehyde amidinourea complex against Staphylococcus aureus (MIC = 8 μg/mL) is twice that of the unsubstituted system (MIC = 16 μg/mL).