反应详情

Methylammonium N-methylthio-carbamate (13.1 g, 0.105 mol; prepared from methylamine and carbonyl sulfide as described, Y. Gelernt et al. 1974, J. Chem. Soc. Perkin Trans. 1, 2610) was partially dissolved in MeOH (150 mL). 3-Chloro-pentane-2,4-dione (14.9 mL, 0.125 mol) was added drop-wise at room temperature, producing a gradual exotherm to 40° C. After stirring at room temperature for 1 h, the solvent was removed in vacuo. The residue was treated with H2O (50 mL) and was extracted with CH2Cl2 (3×50 mL). The combined organic fractions were washed (brine), dried (Na2SO4), filtered, and evaporated in vacuo to an amber-coloured oil. This was purified by chromatography (300 g SiO2, eluting with 1:1 heptane/Et2O to obtain non-cyclized adduct, then Et2O to obtain 5-acetyl-3,4-dimethyl-3H-thiazol-2-one, which was recrystallized from EtOH as colourless needles (14.2 g). 1H-NMR (CDCl3): δ 2.34 (s, 3H), 2.59 (s, 3H), 3.33 (s, 3H). IR (ATR): 1655 and 1621 cm−1 (CO str).

1. customproducing a gradual exotherm to 40° C
2. customthe solvent was removed in vacuo
3. additionThe residue was treated with H2O (50 mL)
4. extractionwas extracted with CH2Cl2 (3×50 mL)
5. washThe combined organic fractions were washed (brine)
6. dry with materialdried (Na2SO4)
7. filtrationfiltered
8. customevaporated in vacuo to an amber-coloured oil
9. customThis was purified by chromatography (300 g SiO2
10. washeluting with 1:1 heptane/Et2O
11. customto obtain non-cyclized adduct