Chemical Properties
2-Acetylthiazole is a colorless to pale yellow liquid with green onion, herbal, grassy, hazelnuts, roasted meat, caramel, corn, and butter odor. Natural products are found in beef broth. Slightly soluble with water, soluble in most organic solvents. It is used in foods as antioxidant, as appearance control agent, and as flavoring ingredient.
Occurrence
2-Acetylthiazole is naturally found in raw asparagus, cooked asparagus, kohlrabi, cooked or boiled potatoes, turkey (roasted), raw chicken, boiled and cooked beef, grilled and roasted beef, pork liver, beer, Finnish whiskey, heated beans, other varieties of mushroom, rice bran, maize, and other natural sources.
Uses
2-Acetylthiazole can be used as a flavoring agent in food industries. It may be used as a food additive in the preparation of ′fragrant′ rice. It also was used in the preparation of triazolothiazoles, chiral alcohols and in aldol condensation reactions.
Definition
ChEBI: 2-Acetylthiazole is an aromatic ketone.
Preparation
2-Acetylthiazole is formed by oxidation of the corresponding carbinol using dichromate.
Aroma threshold values
Detection at 4 ppb
Taste threshold values
Taste characteristics at 30 ppm: corn chip with slightly musty background
Synthesis Reference(s)
The Journal of Organic Chemistry, 53, p. 1748, 1988
DOI: 10.1021/jo00243a029
General Description
2-Acetylthiazole is a volatile flavoring substance generally formed by the Maillard reaction between an amino acid and carbonyl compounds. It is reported to occur in canned sweet corn products, cooked pine mushroom, cooked asparagus and roasted beef.
Synthesis
GENERAL STEPS: n-Butyllithium (13.2 mL, 2.5 M hexane solution) was slowly added to anhydrous ether (30 mL) cooled to -78°C under argon protection. Subsequently, an anhydrous ether solution of 2-bromothiazole (2.7 mL) was added dropwise over 20 min. The reaction mixture was continued to be stirred at -78 °C for 30 min. Under rapid stirring, ethyl acetate (5 mL) was added over 2-3 minutes. After addition, the mixture was stirred at -78°C for 30 minutes and then slowly warmed to room temperature. The reaction was quenched with saturated sodium bicarbonate solution (50 mL) and extracted by adding diethyl ether (50 mL) and water (50 mL). The organic phase was separated, washed sequentially with water and saturated brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by fast column chromatography (20% ethyl acetate/petroleum ether) to afford 2-acetylthiazole as a yellow oil (3.3 g, 87% yield).1H NMR (400 MHz, CDCl3) δ: 2.7 (3H, s), 7.65 (1H, s), 8.0 (1H, s); MS (ES+): m/z 128.1 [M+H]+ .
Purification Methods
Check NMR spectrum; if it is not too bad, distil it through an efficient column in a vacuum. The oxime sublimes at 140-145o, m 159o, and when crystallised from H2O has m 163-165.5o. [Erlenmeyer et al. Helv Chim Acta 31 1142 1948, Waisvisz et al. J Am Chem Soc 79 4524 1957, Menasseé et al. Helv Chim Acta 40 554 1957, Beilstein 27 IV 2617.]
References
[1] Patent: WO2004/87699, 2004, A2. Location in patent: Page 82
