Benzothiazole-5-carboxylic acid

Benzothiazole-5-carboxylic acid is a privileged heterocyclic scaffold found in numerous bioactive molecules, including drugs, agrochemicals, and materials. The presence of the carboxylic acid handle in Benzothiazole-5-carboxylic acid allows straightforward derivatization to amides, esters, acyl chlorides, or conjugates, making this compound a versatile building block for medicinal chemistry and chemical biology. Benzothiazole-5-carboxylic acid features a sulfur atom in the thiazole ring that contributes to unique electronic properties and metal‑binding capabilities, which are exploited in enzyme inhibition studies and coordination chemistry. For these reasons, Benzothiazole-5-carboxylic acid is a preferred intermediate for constructing diverse bioactive molecules and functional materials.

Product Parameters

Typical Preparation Route

Benzothiazole-5-carboxylic acid is conveniently prepared by hydrolysis of the corresponding ethyl ester:

● Starting material: Ethyl benzothiazole‑5‑carboxylate (CAS 103261‑70‑7) – 5.30 g, 25.6 mmol.

● Procedure: Dissolve the ester in a mixture of methanol (150 mL), THF (40 mL), and water (5 mL). Add 50% aqueous NaOH (10 mL). Stir at room temperature for 18 hours.

● Work‑up: Concentrate the reaction mixture. Disperse the residue in water (300 mL) and diethyl ether (200 mL). Discard the organic layer. Adjust the aqueous layer to pH 4 with concentrated HCl, then extract with ethyl acetate (3 × 300 mL). Combine organic extracts, wash with brine (200 mL), dry over Na₂SO₄, and concentrate.

● Yield: 4.30 g (94%) of benzothiazole‑5‑carboxylic acid as a white solid.

This method is mild, scalable, and avoids harsh conditions, preserving product purity.

Storage & Handling Recommendations

● Storage: Store in a sealed, dry container at room temperature (ambient). Protect from moisture and strong oxidants. The compound is a combustible solid (Storage Class 11); keep away from ignition sources.

● Stability: Stable for at least 24 months under recommended storage conditions.

● Handling: Use in a well‑ventilated area (fume hood) with standard PPE (lab coat, gloves, safety goggles). Avoid dust formation.

Frequently Asked Questions (FAQ)

Q1: What is the difference between Benzothiazole-5-carboxylic acid and other isomers (e.g., 2‑ or 6‑)?

A: The position of the carboxylic acid group dramatically affects the compound’s reactivity, solubility, and biological activity. The 5‑carboxy isomer offers a linear molecular shape and allows conjugation through the 2‑position (if unsubstituted) or via the carboxyl group. It is often preferred for constructing amide‑linked libraries. The 2‑carboxy isomer is also common but behaves differently in metal coordination due to proximity to the thiazole nitrogen.

Q2: How should I store benzothiazole‑5‑carboxylic acid?

A: Store at room temperature in a tightly sealed, dry container. It is stable for at least two years. No special inert atmosphere is required, but protection from moisture is recommended.

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