反应详情

A solution of 101.3 g (0.57 mole) of methyl 2-(3-methylacetonylmercapto)acetate in 2.3 liter of dry tetrahydrofuran is added dropwise over a period of 3 hours to a stirred suspension of 0.57 mole of sodium hydride (27.4 g of 50% mineral oil suspension) in 1.1 liter of dry tetrahydrofuran at room temperature under nitrogen. Stirring is continued for an additional 3 hours. The resulting yellow reaction mixture is concentrated to a small volume at temperature below 40° C under reduced pressure, poured into ice-cold water and then extracted with ether. The aqueous layer is acidified at pH 2 - 3 with dilute hydrochloric acid and extracted several times with chloroform. The extracts are washed with a small portion of an aqueous sodium chloride solution and dried over anhydrous sodium sulfate. The solvent is removed in vacuo and the residue is crystallized from methylene chloride - ether to give 62.7 g (75.6% yield) of 4-methyltetrahydrothiopyran-3,5-dione, mp. 131° - 133° C. Recrystallization from acetone - ether gives an analytical specimen, mp. 132.5 - 133° C. IR: νmaxCHCl3 cm-1 : 1735, 1705, 1631; νmaxNujol cm-1 : 1635, 1553. UV: λmax95 %EtOH mμ (ε): 275 (9500), 315 (2400); λmaxN--HCl mμ (ε): 272 (9900); μmaxN--NaOH mμ (ε): 289 (11600), 316 (12900). NMR: ppm (CDCl3): 1.28 (doublet, 3H, J = 7, Me), 3.44 (singlet, 4H, 2-H2 and 6-H2), 3.73 (quartet, 1H, J = 7, 4-H); ppm (CD3OD): 1.69 (broad singlet, 3H, vinyl-Me), 3.34 (broad singlet, 4H, 2-H2 and 6-H2). Anal. Calcd. for C6H8O2S (%): C, 49.98; H, 5.59; S, 22.24. Found (%): C, 50.17; H, 5.50; S, 22.14.

1. concentrationThe resulting yellow reaction mixture is concentrated to a small volume at temperature below 40° C under reduced pressure
2. additionpoured into ice-cold water
3. extractionextracted with ether
4. extractionextracted several times with chloroform
5. washThe extracts are washed with a small portion of an aqueous sodium chloride solution
6. dry with materialdried over anhydrous sodium sulfate
7. customThe solvent is removed in vacuo
8. customthe residue is crystallized from methylene chloride - ether