1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone
[CAS# 7226-23-5]

Identification

• Classification: Chemical reagent >> Organic reagent >> Thiourea
• Name: 1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone
• Synonyms: DMPU; N,N'-Dimethyl-N,N'-trimethyleneurea; N,N'-Dimethylpropyleneurea
• Molecular Formula: C₆H₁₂N₂O
• Molecular Weight: 128.17
• CAS Registry Number: 7226-23-5
• EC Number: 230-625-6
• SMILES: CN1CCCN(C1=O)C

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 1.062 g/mL (Expl.)
• Melting point: -23 °C (Expl.)
• Boiling point: 240.2 °C 760 mmHg (Calc.)^*, 257.9 °C (Expl.)
• Flash point: 85.3±11.1 °C (Calc.)^*, 120 °C (Expl.)
• Index of refraction: 1.474 (Calc.)^*, 1.488 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS05;GHS07;GHS08 Danger
• Risk Statements: H302-H317-H318-H361-H361f
• Safety Statements: P203-P261-P264-P264+P265-P270-P272-P280-P301+P317-P302+P352-P305+P354+P338-P317-P318-P321-P330-P333+P317-P362+P364-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Reproductive toxicity	Repr.	2	H361
Skin sensitization	Skin Sens.	1	H317
Reproductive toxicity	Repr.	2	H361f
Eye irritation	Eye Irrit.	2	H319
Reproductive toxicity	Repr.	2	H361f

Discovery and Applications

1,3-Dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, also known as dimethylbarbituric acid or dimethylbarbiturate, is a derivative of barbituric acid in which both nitrogen atoms of the heterocyclic ring are methylated. This compound has historical significance in medicinal chemistry as a parent structure for various barbiturate drugs, although the compound itself is not typically used therapeutically.

The discovery of barbituric acid derivatives dates back to the 19th century, with barbituric acid first synthesized in 1864 by Adolf von Baeyer. The modification of this core structure through alkylation and other substitutions led to the development of a large number of pharmacologically active barbiturates used as sedatives, hypnotics, and anticonvulsants. Among these, the introduction of methyl groups on the nitrogen atoms, as seen in 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, was one of the early structural modifications studied to assess how alkylation influenced biological activity and chemical stability.

This compound is structurally characterized by a saturated six-membered pyrimidine ring with a ketone group at the 2-position and methyl groups on both nitrogen atoms. The presence of these methyl groups imparts increased lipophilicity relative to unsubstituted barbituric acid, which can influence solubility and membrane permeability. However, the lack of additional substituents on the 5-position of the ring means that 1,3-dimethylbarbituric acid itself does not exhibit significant central nervous system depressant activity, unlike its more heavily substituted analogs.

In chemical synthesis, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone has found application as a reagent or intermediate in organic chemistry. It has been used as a precursor in the synthesis of various barbiturate derivatives and also serves as a building block in the preparation of heterocyclic compounds. Its relatively stable structure and well-defined reactivity make it a useful compound in studies of barbiturate reactivity and in the development of analogs with desired pharmacological properties.

In analytical chemistry, this compound can serve as a reference standard or model for spectroscopic and chromatographic analyses involving barbiturates. Its structural simplicity compared to therapeutic barbiturates makes it useful for method development and validation in forensic or pharmaceutical contexts.

The synthesis of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone is typically achieved through the condensation of N,N-dimethylurea with malonic acid or its derivatives, under acidic or basic conditions that promote cyclization and dehydration to yield the desired heterocycle. The process is well-established and amenable to scale-up, making the compound readily available for laboratory use.

Although not directly employed as a pharmaceutical agent, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone remains of interest in medicinal chemistry as a scaffold and synthetic precursor. Its role in the historical development of barbiturates illustrates the importance of systematic structural modification in drug discovery and optimization. Through its contributions to both theoretical and applied aspects of organic and pharmaceutical chemistry, it continues to serve as a model compound in the study of pyrimidinone derivatives.

References

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DOI: 10.1038/s41929-024-01253-x

2024. Eco-friendly Fabrication of Perovskite Solar Cells: From Material Engineering to Recycling. Korean Journal of Chemical Engineering.
DOI: 10.1007/s11814-024-00331-x

1976. An electrolytic conductivity study of tetraalkylammonium perchlorates in 1,3-dimethylethyleneurea and 1,3-dimethylpropyleneurea at 25°C. Journal of Solution Chemistry.
DOI: 10.1007/bf00647200