2-Propylbenzo[d]thiazole: Properties, Synthesis & Applications

2-Propylbenzo[d]thiazole is a sulfur- and nitrogen-containing bicyclic heterocycle belonging to the benzothiazole family, valued in synthetic chemistry as a versatile intermediate for the preparation of biologically active compounds, dyes, and functional materials.

Chemical Name

2-Propylbenzo[d]thiazole

Molecular Formula

C10H11NS

Molecular Weight

177.26 g/mol

Core Scaffold

Benzo[d]thiazole (fused benzene and thiazole ring)

Key Substituent

n-Propyl group at C-2 position

Primary Use

Synthetic intermediate for pharmaceuticals and agrochemicals

Appearance

Typically a pale yellow to colorless liquid or low-melting solid

Chemical Structure and Physical Properties

2-Propylbenzo[d]thiazole consists of a benzothiazole bicyclic core—formed by fusion of a benzene ring with a 1,3-thiazole ring—bearing an n-propyl substituent at the C-2 position. The thiazole ring contains both a sulfur atom at position 1 and a nitrogen atom at position 3, conferring significant electron-withdrawing character to the heterocyclic system and influencing the compound's reactivity profile.

The compound has the molecular formula C₁₀H₁₁NS and a molecular weight of approximately 177.26 g/mol. The presence of the propyl chain at C-2 increases lipophilicity relative to the parent 2-unsubstituted benzothiazole, which is relevant for membrane permeability in biological applications. The compound is expected to be sparingly soluble in water but readily soluble in common organic solvents such as dichloromethane, ethanol, and ethyl acetate.

The aromatic benzothiazole core imparts UV absorbance, and the compound may exhibit characteristic fluorescence under UV light, a property common to many benzothiazole derivatives. Infrared spectroscopy of 2-alkylbenzothiazoles typically shows C=N stretching near 1590–1610 cm⁻¹ and C–S stretching bands in the 600–700 cm⁻¹ region.

Synthesis and Preparation Methods

The benzothiazole scaffold is classically assembled via the Jacobson–Hugershoff cyclization, in which an aniline derivative is condensed with a carboxylic acid (or its equivalent) in the presence of a sulfur source and an oxidant. For 2-propylbenzo[d]thiazole specifically, butyric acid (or butyraldehyde) serves as the C-2 carbon source, reacting with 2-aminothiophenol under oxidative conditions to furnish the target heterocycle.

Alternative modern approaches include:

• Transition-metal catalysis: Copper- or iron-catalyzed oxidative cyclization of 2-aminothiophenol with aldehydes or ketones provides efficient access to 2-substituted benzothiazoles under mild conditions.
• Electrochemical synthesis: Anodic oxidative cyclization offers a greener route, avoiding stoichiometric oxidants.
• Multicomponent reactions: One-pot condensation strategies incorporating 2-aminothiophenol, an aldehyde, and an oxidant allow rapid library synthesis of 2-alkylbenzothiazoles.

Purification is typically accomplished by column chromatography or vacuum distillation, with purity verification by ¹H NMR, ¹³C NMR, and GC-MS or HPLC analysis.

Biological Activity and Pharmacological Relevance

The benzothiazole heterocycle is a privileged scaffold in medicinal chemistry, appearing in numerous FDA-approved drugs and clinical candidates. 2-Alkylbenzothiazoles, including the propyl-substituted variant, have attracted attention as:

• Antimicrobial agents: Several 2-alkylbenzothiazole derivatives exhibit antibacterial and antifungal activity, attributed in part to the lipophilicity conferred by the alkyl substituent facilitating membrane penetration.
• Anticancer leads: Benzothiazole-based compounds have been explored as kinase inhibitors and tubulin-binding agents in oncology research.
• Enzyme inhibitors: The thiazole nitrogen can coordinate to metal centers in enzyme active sites, making this scaffold relevant for metalloenzyme inhibitor design.

The propyl group at C-2 modulates pharmacokinetic parameters such as logP, aqueous solubility, and metabolic stability compared to shorter- or longer-chain analogs, making 2-propylbenzo[d]thiazole a useful reference compound and starting material for structure–activity relationship (SAR) studies.

Applications in Materials Science and Industrial Chemistry

Beyond pharmaceutical research, 2-alkylbenzothiazoles serve important roles in materials and industrial contexts:

• Fluorescent probes and dyes: The extended π-system of the benzothiazole core supports efficient light absorption and emission. Alkyl-substituted benzothiazoles are incorporated into cyanine dyes, OLED emitters, and fluorescent chemosensors for metal ion detection.
• Corrosion inhibitors: Benzothiazole derivatives are well-documented as corrosion inhibitors for copper, steel, and other metals in industrial cooling and processing systems, functioning via adsorption onto metal surfaces through the sulfur and nitrogen heteroatoms.
• Rubber vulcanization accelerators: Certain benzothiazole-based compounds (e.g., mercaptobenzothiazole derivatives) are used industrially as accelerators in rubber processing; 2-alkyl variants serve as synthetic intermediates in this context.
• Agrochemicals: The scaffold appears in fungicide and herbicide research programs, where the lipophilic alkyl group assists in formulation and bioavailability.

Handling, Storage, and Safety Considerations

As with most organic heterocyclic compounds, standard laboratory safety precautions apply when working with 2-propylbenzo[d]thiazole:

• Personal protective equipment (PPE): Wear appropriate gloves (nitrile recommended), safety goggles, and a laboratory coat. Work in a well-ventilated fume hood to minimize inhalation exposure.
• Storage: Store in a tightly sealed container under cool, dry, and dark conditions, away from strong oxidizing agents and open flames. Refrigerated storage (2–8 °C) is advisable for long-term stability.
• Disposal: Dispose of waste material in accordance with local regulatory requirements for organic solvent and heterocyclic compound waste streams.
• Spill management: Absorb spills with inert material (e.g., vermiculite or dry sand), collect in appropriate waste containers, and avoid releasing into drains or the environment.

Researchers should consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific for the most accurate and up-to-date hazard classifications, first-aid measures, and regulatory information specific to this compound (SKU: P726785).

Frequently asked questions

What is 2-Propylbenzo[d]thiazole used for in research?

2-Propylbenzo[d]thiazole is primarily used as a synthetic intermediate and building block in medicinal chemistry, agrochemical research, and materials science. It serves as a starting material for the preparation of biologically active benzothiazole derivatives explored for antimicrobial, anticancer, and enzyme-inhibitory properties, and is also relevant in the development of fluorescent dyes and corrosion inhibitors.

How should 2-Propylbenzo[d]thiazole be stored to ensure stability?

The compound should be stored in a tightly sealed container under cool (ideally 2–8 °C), dry, and dark conditions, away from strong oxidizing agents and ignition sources. Proper sealing prevents moisture uptake and oxidative degradation. Always refer to the current SDS from Aladdin Scientific for specific storage guidance.

What is the molecular formula and molecular weight of 2-Propylbenzo[d]thiazole?

2-Propylbenzo[d]thiazole has the molecular formula C10H11NS and a molecular weight of approximately 177.26 g/mol. It consists of a benzo[d]thiazole bicyclic core with an n-propyl group substituted at the C-2 position of the thiazole ring.

How does the propyl substituent at C-2 affect the compound's properties compared to other 2-alkylbenzothiazoles?

The n-propyl group at C-2 increases the lipophilicity (logP) of the benzothiazole scaffold compared to methyl or ethyl analogs, which can enhance membrane permeability in biological systems. Compared to longer-chain analogs, the propyl group offers a balance between aqueous solubility and lipophilicity, making it a useful candidate for structure–activity relationship studies in drug discovery.

Where can I purchase research-grade 2-Propylbenzo[d]thiazole?

Research-grade 2-Propylbenzo[d]thiazole is available from Aladdin Scientific under SKU P726785. Aladdin Scientific provides reagent-grade organic compounds with quality documentation to support academic and industrial research workflows.

References

1. Kaur, R. et al. Benzothiazoles: synthetic methods and pharmaceutical applications – a review. Mini-Reviews in Medicinal Chemistry. (General review on benzothiazole chemistry; specific volume and page require verification.)
2. Bondock, S. et al. Synthesis and antimicrobial activity of some new 2-substituted benzothiazole derivatives. European Journal of Medicinal Chemistry. (Specific volume, year, and page require verification.)
3. Metzler-Nolte, N.; Salmain, M. Benzothiazole scaffold in drug design. In: Bioorganometallic Chemistry. (Reference to benzothiazole as privileged scaffold; specific chapter and publisher require verification.)
4. Finšgar, M.; Jackson, J. Application of corrosion inhibitors for steels in acidic media for the oil and gas industry: A review. Corrosion Science. (Benzothiazole corrosion inhibitor context; specific volume and page require verification.)

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