What Is 2,3-Dihydro-5-methylfuran?

2,3-Dihydro-5-methylfuran (CAS 1487-15-6, molecular formula C₅H₈O, MW 84.12 g/mol) is a five-membered oxygen-containing heterocycle featuring a vinyl ether (enol ether) double bond between C-4 and C-5, with a methyl substituent at C-5 and a saturated C-2/C-3 bridge. This combination of an electron-rich alkene within a cyclic ether framework makes it a highly reactive yet structurally defined building block.

Structurally, it belongs to the dihydrofuran family, which occupies an intermediate position between the fully aromatic furan and the fully saturated tetrahydrofuran. The endocyclic double bond confers characteristic enol-ether reactivity: susceptibility to acid-catalyzed hydrolysis, electrophilic addition, and participation in cycloaddition reactions.

Key Chemical Properties and Reactivity

The defining chemical feature of 2,3-Dihydro-5-methylfuran is its enol ether double bond, which is activated by the adjacent ring oxygen through lone-pair donation. This renders C-4 nucleophilic and makes the compound highly reactive toward electrophiles, Brønsted acids, and Lewis acids.

• Acid-catalyzed hydrolysis: Under aqueous acidic conditions, the enol ether is rapidly hydrolyzed to give 4-oxopentanal (levulinaldehyde equivalent) or related carbonyl products, depending on conditions.
• Electrophilic addition: Halogens, halohydrins, and other electrophiles add across the double bond, providing 2-substituted or 3-substituted tetrahydrofuran derivatives.
• Cycloaddition chemistry: As an electron-rich dienophile or heterodiene, it can participate in Diels-Alder and hetero-Diels-Alder reactions, enabling rapid construction of fused bicyclic or polycyclic ring systems.
• Protecting group chemistry: The dihydrofuran moiety can be used to mask carbonyl functionality under mild conditions, analogous to the use of dihydropyran in alcohol protection.

The methyl group at C-5 introduces steric and electronic bias relative to unsubstituted 2,3-dihydrofuran, which can influence regioselectivity in addition reactions and the diastereoselectivity of cycloadditions.

Handling, Storage, and Safety Guidelines

Because 2,3-Dihydro-5-methylfuran is a low-boiling, flammable liquid with a reactive enol ether functionality, appropriate laboratory precautions are essential.

Flammability: The compound is a flammable liquid. Keep away from open flames, hot surfaces, and ignition sources. Use in a well-ventilated fume hood.

Reactivity hazards: The enol ether bond is sensitive to acids (including atmospheric moisture in the presence of acid traces) and oxidizers. Prolonged exposure to air may lead to peroxide formation — a hazard common to many ethers. Containers should be tested for peroxides before distillation or concentration.

Personal protective equipment: Wear appropriate chemical-resistant gloves, safety goggles, and a lab coat. Avoid inhalation of vapors.

Storage: Store in a tightly sealed container under an inert atmosphere (nitrogen or argon) in a cool, dry location away from acids, oxidizers, and ignition sources. Long-term storage with a suitable inhibitor (e.g., BHT) is recommended to suppress peroxide accumulation and polymerization.

Disposal: Dispose of according to local regulations for flammable organic solvents and reactive chemicals.

Note: Always consult the current Safety Data Sheet (SDS) for the most up-to-date hazard and handling information before use.

Synthetic Applications in Organic Chemistry

2,3-Dihydro-5-methylfuran finds application across several areas of synthetic organic chemistry owing to its dual character as both a reactive enol ether and a cyclic ether scaffold.

Heterocyclic synthesis: It serves as a starting material or intermediate in the preparation of substituted tetrahydrofurans, fused furan derivatives, and oxygen-containing polycyclic natural product analogues.

Cycloaddition reactions: Its electron-rich double bond makes it a useful partner in [4+2] cycloadditions with electron-poor dienes or dienophiles, enabling efficient assembly of bicyclic ring systems bearing oxygen heteroatoms. Hetero-Diels-Alder strategies using dihydrofurans are well-documented in the literature as routes to pyranose and furanose mimics.

Annulation and ring-expansion strategies: The compound can participate in transition-metal-catalyzed C–H functionalization and ring-opening/ring-closing sequences that deliver complex carbocyclic or heterocyclic architectures.

Protecting group and masking strategies: Analogous to dihydropyran, the dihydrofuran unit can serve to protect aldehydes or ketones as mixed acetals under acid catalysis, with subsequent deprotection under mild aqueous acidic conditions.

Researchers are encouraged to review recent primary literature for specific reaction conditions, as yields and selectivities depend heavily on substrate structure, catalyst choice, and solvent system.

Ordering and Product Information at Aladdin Scientific

Aladdin Scientific supplies 2,3-Dihydro-5-methylfuran under SKU D191034. When placing an order or evaluating the product for your research needs, consider the following:

• Purity and specification: Please refer to the product page and Certificate of Analysis (CoA) for the current lot purity, appearance, and analytical data. Contact our technical support team if you require a custom purity grade or larger pack sizes.
• Packaging: Available in standard research quantities. Packaging is designed to maintain an inert atmosphere and minimize moisture and air exposure during transit and storage.
• Shipping: As a flammable liquid, the compound is classified as a hazardous material for shipping purposes. Shipment complies with applicable IATA, IMDG, and local carrier regulations. Delivery timelines may vary by destination and shipping class — consult the product page or contact customer service for details.
• Returns and quality issues: If you receive a product that does not meet specification, contact Aladdin Scientific customer service promptly with your order number and CoA reference. Our standard returns and refund policy applies.
• Pricing and promotions: Pricing is available on the product listing page. Registered users may access volume discounts, coupon codes, and reward-point benefits through their account portal.