# 3,4,5-Trimethoxybenzaldehyde
**3,4,5-Trimethoxybenzaldehyde** is an aromatic aldehyde in which a benzaldehyde ring carries methoxy groups at the 3, 4, and 5 positions, giving the formula C₁₀H₁₂O₄ and the CAS registry number 86-81-7.[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde)
| Key fact | Detail |
|---|---|
| Identifiers | CAS 86-81-7; PubChem CID 6858; EC number 201-701-6; UNII WL86YD76N6; InChIKey OPHQOIGEOHXOGX-UHFFFAOYSA-N[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) |
| Formula and mass | C₁₀H₁₂O₄; molecular weight 196.20 g/mol; exact mass 196.07355886 Da[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) |
| Physical form | Cream-to-white solid; melting point 73.0–76.0 °C; boiling point 163.0–165.0 °C at 10 mmHg[2](https://www.fishersci.com/shop/products/3-4-5-trimethoxybenzaldehyde-99-thermo-scientific/p-3758936) |
| Principal use | Key intermediate in the synthesis of trimethoprim, the sulfonamide-potentiating dihydrofolate reductase inhibitor[3](https://patents.justia.com/patent/4239702) |
| Main synthetic routes | Modified Rosenmund reduction of the acid chloride (64–83% yield); bromination, hydrolysis, and methylation of vanillin[4](https://www.orgsyn.org/demo.aspx?prep=CV6P1007) • [5](https://patents.google.com/patent/US3855306A/en) |
| Hazard classification | GHS H302 (harmful if swallowed), H315 (skin irritation), H319 (serious eye irritation), H335 (may cause respiratory irritation)[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) |
## Physical and chemical properties
The compound is a trisubstituted aromatic aldehyde: three methoxy groups occupy the positions meta and para to the formyl group on the benzene ring.[6](https://www.sciencedirect.com/science/article/abs/pii/S0030399218319078) Its computed properties reflect a small, moderately lipophilic molecule: XLogP3 of 0.9, four hydrogen bond acceptors, no hydrogen bond donors, four rotatable bonds, and a topological polar surface area of 44.8 Ų.[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) It is slightly soluble in water and soluble in alcohol, toluene, and acetone.[2](https://www.fishersci.com/shop/products/3-4-5-trimethoxybenzaldehyde-99-thermo-scientific/p-3758936) A safety data sheet lists a literature melting range of 72–74 °C, close to the supplier specification of 73.0–76.0 °C.[7](https://www.chemicalbook.com/msds/3-4-5-trimethoxybenzaldehyde.htm)
## Role in pharmaceutical synthesis
**Trimethoprim.** The dominant use of 3,4,5-trimethoxybenzaldehyde is in the production of trimethoprim, 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine, an antimicrobial agent and sulfonamide synergist.[3](https://patents.justia.com/patent/4239702) In one patented process, two moles of the aldehyde are condensed with one mole of 3,3'-(phenylenedi-imino)dipropanenitrile in a polar solvent such as dimethyl sulfoxide or tert-butanol at 10–30 °C in the presence of an alkaline condensing agent such as sodium methoxide, forming a benzylacrylonitrile intermediate; this then reacts with guanidine to give trimethoprim.[8](https://patents.google.com/patent/EP0067593A1/en) Reported yields for the condensation step reach 94% of theory for the ortho-phenylene intermediate, and the guanidine cyclization gives trimethoprim in 60–83% yield depending on the isomer used.[8](https://patents.google.com/patent/EP0067593A1/en)
**Controlled-substance context.** The United States Drug Enforcement Administration lists it as a DEA NFLIS substance in the class "Other Substances," added in October 1998.[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde)
## Synthesis
Several routes to the aldehyde have been used industrially, and a review of synthetic routes describes it as a key intermediate whose production cost matters for drug manufacture.[9](https://www.thevespiary.org/rhodium/Rhodium/Vespiary/talk/files/3851-Synthetic-Routes-to-345-trimethoxybenzaldehyde-Review6d99.pdf)
**Modified Rosenmund reduction.** The classical Rosenmund reduction of 3,4,5-trimethoxybenzoyl chloride works on small scale but has disadvantages for large preparations, including long reaction cycles, inefficient hydrogen use, and the need to monitor evolved hydrogen chloride.[4](https://www.orgsyn.org/demo.aspx?prep=CV6P1007) An Organic Syntheses procedure carries out the reduction in a closed pressure vessel with sodium acetate as a hydrogen chloride acceptor, 10% palladium-on-carbon, and quinoline sulfur as catalyst poison, at 50 psi of hydrogen; it gives 12.5–16.2 g (64–83%) of product boiling at 158–161 °C at 7–8 mmHg and melting at 74–75 °C, and the submitters report 78–84% yield on a fivefold scale.[4](https://www.orgsyn.org/demo.aspx?prep=CV6P1007) A related industrial variant forms the mixed anhydride of 3,4,5-trimethoxybenzoic acid with ethyl or isobutyl chlorocarbonate and then reduces it catalytically directly to the aldehyde.[10](https://patents.google.com/patent/US4240984A/en)
**Vanillin route.** A Hoffmann-La Roche patent (US 3,855,306, filed 1972) describes a three-step synthesis from inexpensive vanillin: bromination to 5-bromovanillin, hydrolysis to 5-hydroxyvanillin, and methylation to the trimethoxy aldehyde.[5](https://patents.google.com/patent/US3855306A/en) The methylation step contacts 5-hydroxyvanillin with a 15 to 25% excess of dimethyl sulfate and a powdered alkali metal carbonate in acetone or a similar organic medium.[5](https://patents.google.com/patent/US3855306A/en) A later patent analysis judged both widely used industrial processes, the Rosenmund reduction and the vanillin route, unsatisfactory because of high product cost and poor or inconsistent yields; the Rosenmund route gave 50–80% of theory in earlier studies, and the bromovanillin substitution step was described as not economically acceptable.[3](https://patents.justia.com/patent/4239702)
**Gallic acid route.** [Methylation](https://www.edgepedia.org/methylation) of gallic acid (3,4,5-trihydroxybenzoic acid) gives 3,4,5-trimethoxybenzoic acid, which can then be reduced to the aldehyde; this is the basis of a biotechnological approach to trimethoprim production.[11](https://www.researchgate.net/publication/270449835_Production_of_an_antibacterial_drug_trimethoprim_using_novel_biotechnological_approach) A Chinese patent application describes a route in which gallic acid is methylated and esterified with dimethyl sulfate, reacted with hydrazine hydrate, and then oxidized with potassium ferricyanide.[12](https://patents.google.com/patent/AU2018101124A4/en)
**Other preparations.** [Organic Syntheses](https://www.edgepedia.org/organic-syntheses) also records preparation by methylation of 5-hydroxyvanillin and by oxidation of 3,4,5-trimethoxybenzyl alcohol.[4](https://www.orgsyn.org/demo.aspx?prep=CV6P1007)
## Natural occurrence
The compound has been reported as a natural product in *Zanthoxylum ailanthoides* and *Acorus calamus*, among other organisms, according to the LOTUS natural products occurrence database.[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) Its biosynthesis in plants is believed to follow the phenylpropanoid pathway, with gallic acid (3,4,5-trihydroxybenzoic acid) proposed as a key intermediate, although the specific enzymatic steps have not been fully elucidated for the plant species in which it occurs.[13](https://www.benchchem.com/pdf/The_Natural_Occurrence_and_Sources_of_3_4_5_Trimethoxybenzaldehyde_A_Technical_Guide.pdf)
## Regulation and safety
Under the US Toxic Substances Control Act, benzaldehyde, 3,4,5-trimethoxy- has the commercial activity status ACTIVE, and it is listed on the Australian Inventory of Industrial Chemicals; in New Zealand it does not have an individual approval but may be used under an appropriate group standard.[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) Aggregated European notifications (8 reports from 5 notifiers) classify it mainly as an irritant: H302 harmful if swallowed (75% of reports), H315 causes skin irritation (87.5%), H319 causes serious eye irritation (87.5%), and H335 may cause respiratory irritation (25%); one report found it did not meet GHS hazard criteria.[1](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde) Supplier safety guidance calls for protective gloves, clothing, and eye and face protection, and for rinsing the eyes cautiously with water for several minutes on contact.[2](https://www.fishersci.com/shop/products/3-4-5-trimethoxybenzaldehyde-99-thermo-scientific/p-3758936)
## References
1. [3,4,5-Trimethoxybenzaldehyde, CID 6858, PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/3_4_5-trimethoxybenzaldehyde)
2. [3,4,5-Trimethoxybenzaldehyde, 99%, Thermo Scientific Chemicals, Fisher Scientific](https://www.fishersci.com/shop/products/3-4-5-trimethoxybenzaldehyde-99-thermo-scientific/p-3758936)
3. [US Patent 4,239,702, Process for preparing aromatic aldehydes and alcohols, Justia Patents](https://patents.justia.com/patent/4239702)
4. [Aldehydes from Acid Chlorides by Modified Rosenmund Reduction: 3,4,5-Trimethoxybenzaldehyde, Organic Syntheses, Coll. Vol. 6, p.1007 (1988)](https://www.orgsyn.org/demo.aspx?prep=CV6P1007)
5. [US Patent 3,855,306, Process for the preparation of 3,4,5-trimethoxybenzaldehyde, Google Patents](https://patents.google.com/patent/US3855306A/en)
6. [Growth and characterization of organic material 3,4,5-trimethoxybenzaldehyde single crystal for optical applications, ScienceDirect](https://www.sciencedirect.com/science/article/abs/pii/S0030399218319078)
7. [3,4,5-Trimethoxybenzaldehyde Safety Data Sheet, ChemicalBook](https://www.chemicalbook.com/msds/3-4-5-trimethoxybenzaldehyde.htm)
8. [EP0067593A1, Process for the preparation of trimethoprim and novel intermediates for use therein, Google Patents](https://patents.google.com/patent/EP0067593A1/en)
9. [Synthetic Routes to 3,4,5-Trimethoxybenzaldehyde (Review)](https://www.thevespiary.org/rhodium/Rhodium/Vespiary/talk/files/3851-Synthetic-Routes-to-345-trimethoxybenzaldehyde-Review6d99.pdf)
10. [US Patent 4,240,984, Process for producing aromatic aldehydes, Google Patents](https://patents.google.com/patent/US4240984A/en)
11. [Production of an antibacterial drug trimethoprim using novel biotechnological approach, ResearchGate](https://www.researchgate.net/publication/270449835_Production_of_an_antibacterial_drug_trimethoprim_using_novel_biotechnological_approach)
12. [AU2018101124A4, Drug intermediates 3,4,5-trimethoxybenzaldehyde synthesis method, Google Patents](https://patents.google.com/patent/AU2018101124A4/en)
13. [The Natural Occurrence and Sources of 3,4,5-Trimethoxybenzaldehyde: A Technical Guide, BenchChem](https://www.benchchem.com/pdf/The_Natural_Occurrence_and_Sources_of_3_4_5_Trimethoxybenzaldehyde_A_Technical_Guide.pdf)
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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Alcohols, ethers, and organooxygen groups › Phenols and phenolic compounds › Phenolic ethers (aryl alkyl and diaryl ethers) › Polymethoxybenzenes and trimethoxy systems*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 11, 2026; Oct 15, 2026; Oct 25, 2026 · Last review: Oct 15, 2026*
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