Chemical Identity and Structure

3-(Methylthio)phenylboronic acid pinacol ester (SKU: M186176) is an arylboronic ester in which a pinacol ester group (Bpin) is attached to a phenyl ring bearing a methylthio (–SCH₃) substituent at the meta (3-) position. The pinacol ester form offers significantly enhanced air and moisture stability compared with the corresponding free boronic acid, making it a practical choice for bench-top synthetic operations.

The methylthio group introduces a soft-donor sulfur atom that can participate in downstream transformations, serve as a directing group, or contribute to the biological activity profile of target molecules. This combination of a reactive boronate handle and a functionally rich arene makes M186176 a valuable synthetic building block across multiple chemical disciplines.

Synthetic Applications and Reactivity

Suzuki–Miyaura Cross-Coupling: The primary application of 3-(Methylthio)phenylboronic acid pinacol ester is as a coupling partner in palladium-catalyzed Suzuki–Miyaura reactions. The compound reacts with aryl, heteroaryl, vinyl, or alkyl halides (or triflates) in the presence of a Pd catalyst and a base to form new C–C bonds, incorporating the 3-(methylthio)phenyl motif into complex molecular architectures. Common catalyst systems include Pd(PPh₃)₄, Pd(dppf)Cl₂, and Pd(OAc)₂ with phosphine ligands.

Other Coupling Reactions: Arylboronic esters such as M186176 can also participate in Chan–Lam coupling (C–N, C–O, C–S bond formation under copper catalysis), Miyaura borylation exchange, and rhodium-catalyzed 1,4-addition reactions to enones, extending the utility of the reagent beyond classical Suzuki chemistry.

Downstream Functionalization of the Methylthio Group: The –SCH₃ substituent can be oxidized to the sulfoxide or sulfone, engaged in electrophilic aromatic substitution directing effects, or converted to other sulfur-containing functional groups, providing additional handles for molecular elaboration after the initial coupling step.

Handling, Safety, and Storage Guidelines

Personal Protective Equipment (PPE): When handling 3-(Methylthio)phenylboronic acid pinacol ester, wear appropriate PPE including chemical-resistant gloves, a laboratory coat, and eye protection. Work in a well-ventilated fume hood, particularly when weighing or dissolving the compound, as fine powders can pose an inhalation risk.

Storage: Store the reagent in a tightly sealed container in a cool, dry, and well-ventilated location, protected from moisture, light, and incompatible materials such as strong oxidizing agents. Moisture ingress can lead to hydrolysis of the pinacol ester to the boronic acid and subsequent protodeboronation. Desiccants such as molecular sieves or silica gel sachets are recommended inside storage containers.

Stability Considerations: Arylboronic acid pinacol esters are generally more shelf-stable than free boronic acids; however, prolonged exposure to air and humidity should be avoided. Check product-specific certificates of analysis (CoA) for purity specifications and recommended re-analysis intervals. Discard if significant discoloration or solidification is observed.

Waste Disposal: Dispose of residues and solutions containing this compound in accordance with local, regional, and national chemical waste regulations. Consult the Safety Data Sheet (SDS) provided by Aladdin Scientific for detailed disposal and first-aid information.

Recommended Reaction Conditions and Protocol Tips

Solvent Selection: Polar aprotic solvents such as DMF, DMSO, or 1,4-dioxane, often in combination with water, are commonly used for Suzuki–Miyaura reactions with boronic esters. Tetrahydrofuran (THF)/water mixtures are also widely employed. The choice of solvent can significantly influence reaction rate and yield.

Base: Inorganic bases such as K₂CO₃, Cs₂CO₃, K₃PO₄, or Na₂CO₃ are typical choices. These bases facilitate transmetalation of the boronate species onto the palladium center. The base strength and concentration should be optimized for each substrate pair.

Catalyst Loading and Temperature: Typical Pd catalyst loadings range from 1–5 mol%. Reactions are commonly run at 80–100 °C under an inert atmosphere (nitrogen or argon) to prevent catalyst oxidation and minimize side reactions. Microwave-assisted conditions can accelerate reaction times.

Reaction Monitoring: Progress can be monitored by thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC). Product isolation typically involves aqueous workup followed by column chromatography on silica gel.

Moisture Precautions: Although the pinacol ester is more moisture-resistant than the free boronic acid, reactions should be set up under inert atmosphere using dry solvents when optimal yields are required, especially at small scale.

Quality Specifications and Procurement

Purity and Analysis: Aladdin Scientific supplies 3-(Methylthio)phenylboronic acid pinacol ester (M186176) with a certificate of analysis (CoA) detailing purity as determined by NMR, GC, or HPLC. Researchers are advised to consult the CoA shipped with each lot and to perform independent quality checks if the reagent is to be used in sensitive or quantitative assays.

Available Pack Sizes: Contact Aladdin Scientific or visit the product page for current available quantities and pricing. Bulk quantities may be available upon request for larger research programs.

Ordering: M186176 can be ordered directly through the Aladdin Scientific website or via authorized distributors. For institutional procurement, purchase orders and quotation requests can be submitted through the standard ordering portal. Rewards points and promotional pricing may apply; consult the Aladdin Scientific promotions page for current offers.

Returns and Quality Complaints: In the event of a quality concern, contact Aladdin Scientific customer service with the lot number and CoA. Returns and replacements are handled in accordance with Aladdin Scientific's returns and refund policy.