1-(5-Methyl-2-thienyl)ethan-1-one

Chemical Properties

white to light yellow crystal powder

Uses

2-Acetyl-5-methylthiophene may be used in the preparation of:

• 2-ethyl-5-methylthiophene
• (5-methylthiophen-2-yl)glyoxal
• (2E)-1-(5-methylthiophen-2-yl)-3-(pyridin-3-yl)prop-2-en-1-one
• ethyl 3-(5-methylthiophen-2-yl)-3-oxopropanoate

Definition

ChEBI: 2-acetyl-5-methylthiophene is a thiophene that is substituted by acetyl and methyl groups at positions 2 and 5, respectively. It has a role as a flavouring agent. It is an aromatic ketone, a member of thiophenes and a methyl ketone.

General Description

2-Acetyl-5-methylthiophene is a volatile organic compound formed during the reaction between L-cysteine and dihydroxyacetone in glycerine or triglyceride solvent system. It can be prepared by reacting 2-methylthiophene with acetic anhydride. 2-Acetyl-5-methylthiophene undergoes palladium-catalyzed cross-coupling reaction with aryl bromides to form C-4 arylated product. It reacts with 1,2-bis(5-formyl-2-methylthiophen-3-yl)cyclopentene via Aldol condensation to form a chalcone with photochromic property. The standard molar enthalpies of combustion, formation and vaporization of 2-acetyl-5-methylthiophene are 4341.9 ± 1.8kJ/mol, 158.0 ± 2.1kJ/mol and 62.0 ± 2.6kJ/mol, respectively.

Safety Profile

A poison by intraperitoneal route. A flammable liquid. When heated to decomposition it emits toxic vapors of SOx.

Synthesis

554-14-3

75-36-5

13679-74-8

General procedure: 2-methylthiophene and acetyl chloride were used as raw materials for the synthesis of 2-acetyl-5-methylthiophene by Friedel-Crafts acylation reaction. The procedure was as follows: a double-necked round-bottomed flask equipped with a magnetic stirrer was charged with a pre-prepared MoO4 (AlCl22 (5 wt%, 10 mg)) catalyst, which was to be activated at 150 °C for 2 hours. Subsequently, 2-methylthiophene (1 g, 9.26 mmol) and acetyl chloride (5 equiv) were added to the reaction flask. The reaction mixture was stirred at room temperature until the reaction was completed and the reaction progress was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture was filtered to isolate the solid catalyst, which could be recycled for the next Friedel-Crafts acylation reaction. The reaction mixture was washed sequentially with dichloromethane (DCM) and water and the process was repeated three times. The organic layer was collected, dried with anhydrous sodium sulfate and subsequently concentrated on a rotary evaporator to give the crude product. Finally, the crude product was purified by column chromatography to afford the target compound 2-acetyl-5-methylthiophene.

References

[1] European Journal of Organic Chemistry, 2010, # 31, p. 6033 - 6037
[2] European Journal of Organic Chemistry, 2016, vol. 2016, # 18, p. 3126 - 3129
[3] Journal of Nanoscience and Nanotechnology, 2015, vol. 15, # 10, p. 8243 - 8250
[4] Journal of Heterocyclic Chemistry, 1982, vol. 19, p. 701 - 702
[5] Chemische Berichte, 1886, vol. 19, p. 1858