3,4-Dimethoxybenzyl Chloride: Properties, Uses & Safety FAQ

3,4-Dimethoxybenzyl chloride is a reactive benzylic halide reagent widely used in organic synthesis as an alkylating agent and in the introduction of the veratryl protecting group onto nucleophilic substrates.

Chemical Name

3,4-Dimethoxybenzyl chloride (veratryl chloride)

Molecular Formula

C₉H₁₁ClO₂

Molecular Weight

186.63 g/mol

CAS Number

1184-66-3

Functional Class

Benzylic alkylating agent; protecting-group precursor

Key Application

N-, O-, and S-alkylation; veratryl group introduction in natural product synthesis

Storage Condition

Store sealed under inert atmosphere, cool and dry, away from light

What Is 3,4-Dimethoxybenzyl Chloride and What Are Its Key Properties?

3,4-Dimethoxybenzyl chloride, also known as veratryl chloride, is an aromatic benzyl chloride derivative bearing two methoxy substituents at the 3- and 4-positions of the phenyl ring. It has the molecular formula C₉H₁₁ClO₂ and a molecular weight of approximately 186.63 g/mol (CAS 1184-66-3).

The compound is typically a colourless to pale yellow liquid or low-melting solid with a characteristic aromatic odour. The two electron-donating methoxy groups stabilise the developing benzylic carbocation through resonance, significantly enhancing the electrophilic reactivity of the chloromethyl group compared with unsubstituted benzyl chloride. This electronic activation makes it an efficient alkylating agent under mild reaction conditions.

The compound is moisture-sensitive and prone to hydrolysis; it should be handled under anhydrous conditions and stored sealed under an inert atmosphere in a cool, dry, and dark environment to prevent decomposition.

What Are the Main Synthetic Applications of 3,4-Dimethoxybenzyl Chloride?

3,4-Dimethoxybenzyl chloride serves several important roles in preparative organic chemistry:

• N-Alkylation: It reacts with amines (primary and secondary) in the presence of a base to furnish N-(3,4-dimethoxybenzyl) amines, building blocks encountered in pharmaceutical and natural-product synthesis.
• O-Alkylation: Alcohols and phenols can be alkylated under standard Williamson-type conditions to give the corresponding benzyl ethers, which are useful protecting groups cleavable by hydrogenolysis or Lewis-acid-mediated deprotection.
• S-Alkylation: Thiols react with veratryl chloride to form thioethers under mild basic conditions.
• Veratryl protecting group introduction: The 3,4-dimethoxybenzyl (DMB) group is selectively removable under oxidative conditions (e.g., DDQ/CH₂Cl₂/H₂O) or with Lewis acids such as TFA or BCl₃, providing orthogonal selectivity relative to simple benzyl or PMB groups in complex molecule synthesis.
• Isoquinoline alkaloid synthesis: The veratryl motif is a core structural feature in many isoquinoline alkaloids; the chloride serves as a direct precursor to veratraldehyde-derived intermediates and in Pictet–Spengler-type condensations.

Its mild reactivity profile and the electronic richness of the aromatic ring make it compatible with a wide range of functional groups present in complex substrates.

How Should 3,4-Dimethoxybenzyl Chloride Be Handled and Stored Safely?

Hazard overview: Like other benzyl chlorides, 3,4-dimethoxybenzyl chloride is a lachrymator and potential irritant to skin, eyes, and the respiratory tract. It is classified as an alkylating agent and should be handled accordingly. Consult the Safety Data Sheet (SDS) provided with the product for current GHS classifications and specific hazard statements before use.

Personal Protective Equipment (PPE): Use chemical-resistant gloves (e.g., nitrile or neoprene), safety goggles with side shields, and a laboratory coat. All manipulations should be performed in a well-ventilated fume cupboard.

Waste disposal: Dispose of waste containing benzyl chlorides according to local regulations for halogenated organic waste. Do not pour down the drain.

Storage: Store the sealed container under an inert gas (nitrogen or argon) in a cool (2–8 °C recommended), dry location away from light and incompatible materials such as strong oxidisers, strong bases, and water. Inspect stored material periodically for discolouration or turbidity, which may indicate decomposition.

How Does 3,4-Dimethoxybenzyl Chloride Compare with Related Benzyl Chloride Reagents?

Researchers frequently choose between several methoxybenzyl chloride variants depending on the required reactivity and deprotection strategy:

• Benzyl chloride (BnCl): Least activated; the benzyl group is removed by catalytic hydrogenolysis (H₂/Pd-C) or dissolving-metal conditions.
• 4-Methoxybenzyl chloride (PMBCl, p-anisyl chloride): One methoxy group provides moderate activation; the PMB ether is cleaved by DDQ oxidation or Lewis acids (e.g., CAN, TFA), and is among the most widely used acid-labile protecting groups.
• 3,4-Dimethoxybenzyl chloride (veratryl chloride, DMBCl): Two methoxy groups confer greater electron density, making it more reactive toward nucleophiles than PMBCl. The DMB group is cleaved under similar oxidative or Lewis-acid conditions, but its slightly different electronic profile can offer selectivity advantages in multi-step syntheses where PMB and DMB groups must be differentiated.
• 2,4-Dimethoxybenzyl chloride: Used for acid-labile amine protection (Dmb group in peptide chemistry); the 2,4-pattern differs from the 3,4-pattern in stability and deprotection conditions.

The choice among these reagents depends on the functional-group tolerance of the substrate, the deprotection conditions compatible with other protecting groups in the molecule, and the target natural product or pharmaceutical scaffold.

Ordering and Availability of 3,4-Dimethoxybenzyl Chloride from Aladdin Scientific

Aladdin Scientific supplies 3,4-dimethoxybenzyl chloride under SKU D186293. When placing an order, please verify the required quantity, purity grade, and packaging format on the product page before checkout. For bulk quantities or custom specifications, contact Aladdin Scientific's sales team directly.

The reagent is shipped in accordance with applicable regulations for halogenated organic compounds. Standard lead times and shipping conditions apply; please consult the shipping and delivery policy or contact customer service for time-sensitive requirements. For questions about invoicing, pricing, promotions, or reward points, refer to the relevant help sections of the Aladdin Scientific website or contact the support team.

Researchers requiring a Certificate of Analysis (CoA), Safety Data Sheet (SDS), or NMR/HPLC purity data for the specific lot should request these documents at the time of ordering or through the online document portal.

Frequently asked questions

What nucleophiles react well with 3,4-dimethoxybenzyl chloride?

3,4-Dimethoxybenzyl chloride reacts efficiently with a broad range of nucleophiles including amines (primary and secondary), alcohols, phenols, and thiols. Reactions are typically conducted in polar aprotic solvents such as DMF, acetonitrile, or acetone in the presence of an inorganic base (K₂CO₃, Cs₂CO₃) or tertiary amine base. The electron-rich aromatic ring activates the benzylic position, facilitating S_N2 displacement under mild conditions.

How is the 3,4-dimethoxybenzyl (DMB) protecting group removed?

The DMB group can be removed by oxidative deprotection using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in a mixture of dichloromethane and water, analogous to the removal of the PMB group. Lewis-acid-mediated cleavage with reagents such as trifluoroacetic acid (TFA) or boron trichloride (BCl₃) is also reported. The choice of method depends on the stability of other functional groups in the molecule.

Is 3,4-dimethoxybenzyl chloride the same as veratryl chloride?

Yes. Veratryl chloride is the common name for 3,4-dimethoxybenzyl chloride (CAS 1184-66-3). Both names refer to the same compound bearing a chloromethyl group on the benzylic position of a 3,4-dimethoxybenzene (veratrole) ring system. Researchers may encounter both names in the literature.

What solvents and bases are recommended for O-alkylation reactions using this reagent?

For O-alkylation of alcohols and phenols, DMF or acetone are commonly used solvents, with potassium carbonate (K₂CO₃) or cesium carbonate (Cs₂CO₃) as the base. Reactions are typically run at room temperature to 60 °C depending on the substrate reactivity. Phase-transfer catalysis (e.g., tetrabutylammonium bromide) can improve yields with less reactive substrates.

What should I do if 3,4-dimethoxybenzyl chloride becomes discoloured in storage?

Discolouration (darkening or browning) of the reagent typically indicates partial hydrolysis or oxidative decomposition, which may reduce its effective purity and reactivity. It is advisable to check the lot-specific Certificate of Analysis (CoA) for purity data, and if in doubt, to obtain a fresh batch. Proper storage under inert atmosphere, low temperature, and exclusion of moisture will maximise shelf life.

References

1. March, J.; Smith, M. B. March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 7th ed.; Wiley: Hoboken, NJ, 2013. (General reference for S_N2 alkylation chemistry and protecting-group principles.)
2. Wuts, P. G. M.; Greene, T. W. Greene's Protective Groups in Organic Synthesis, 4th ed.; Wiley-Interscience: Hoboken, NJ, 2006. (Reference for DMB and related benzyl protecting groups, deprotection conditions.)
3. Oikawa, Y.; Yoshioka, T.; Yonemitsu, O. Specific removal of O-methoxybenzyl protection by DDQ oxidation. Tetrahedron Letters 1982, 23 (8), 885–888. (Seminal reference for DDQ-mediated PMB/DMB ether deprotection.) doi:10.1016/S0040-4039(00)87022-5

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