2-Acetyl-3-methylthiophene

1. Basic information

Chinese name: 2-acetyl-3-methylthiophene

English name: 2-Acetyl-3-methylthiophene

Chemical formula: C₇H₈OS

Molecular weight: 140.20 g/mol

CAS number: 13679-72-0

Structural characteristics: The 2-position of the thiophene ring is replaced by an acetyl group (-COCH₃), and the 3-position is replaced by a methyl group (-CH₃), forming a sulfur-containing heterocyclic ketone compound with both aromaticity and carbonyl reactivity.

2. Physical and chemical properties

Appearance and state:

It is a colorless to light yellow transparent liquid at room temperature. It may gradually turn dark yellow due to oxidation or light exposure after long storage. It has a special smell similar to nuts or thioether.

Melting point: -25℃, boiling point: 210-212℃ (760 mmHg), flash point: 87℃ (closed cup), density: 1.12 g/cm³ (25℃).

Solubility: Slightly soluble in water, easily soluble in organic solvents such as ethanol, ether, dichloromethane, toluene, and well miscible with acetone and ethyl acetate.

Chemical properties:

Carbonyl reactivity: The acetyl group can undergo typical reactions of ketones, such as condensation with hydroxylamine to form oxime, addition with Grignard reagents, and reduction to alcohols (such as NaBH₄ reduction to 2-(1-hydroxyethyl)-3-methylthiophene);

Thiophene ring reactivity: The aromatic ring can undergo electrophilic substitution (such as bromination, nitration), and the substitution site is preferentially at a position with a higher electron cloud density (such as the 5th position);

Stability: Stable at room temperature, avoid contact with strong oxidants, strong acids or strong bases, and high temperatures may cause the thiophene ring to open.

3. Synthesis method

Friedel-Crafts acylation method:

Using 3-methylthiophene as raw material, under the catalysis of Lewis acid such as aluminum chloride, it undergoes Friedel-Crafts acylation reaction with acetyl chloride or acetic anhydride to generate 2-acetyl-3-methylthiophene. The reaction is carried out in an inert solvent (such as dichloroethane) at low temperature, and the post-treatment is purified by water washing, liquid separation, and distillation.

Thiophene derivative synthesis method:

Thiophene derivatives are prepared by nucleophilic substitution of 2-bromo-3-methylthiophene with acetyl lithium reagent, or by acylation-methylation of thiophene ring step-by-step reaction.

4. Application field

Medicine and pesticide intermediates:

As a heterocyclic skeleton, it is used to synthesize antibacterial and anti-inflammatory drugs. For example, some derivatives containing thiophene structure have the effect of inhibiting bacterial enzyme activity;

In pesticides, it is used to design insecticides and fungicides. The introduction of methyl and acetyl groups can adjust the lipid solubility and biological activity of the compound.

Flavors and flavors:

Their special smell can be used to prepare edible flavors (such as nuts, meat flavors) or daily chemical flavors, which must comply with food additive safety standards (such as FEMA number confirmation).

Material Science:

As a monomer for synthesizing conductive polymers (such as polythiophene derivatives), acetyl groups can be introduced into functional groups through decarbonylation reactions or further modifications for use in organic solar cells or sensor materials.

Organic Synthesis:

As a thioketone intermediate, it is used to construct complex molecules (such as preparing α,β-unsaturated ketones through aldol condensation, or extending conjugated systems through thiophene ring coupling reactions).