2-Mercaptoethanol → 1,4-Oxathiin, 2,3-dihydro-5,6-diphenyl-

反応式

[C:1]1([C:7]([CH:9]([C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)O)=[O:8])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[SH:17][CH2:18][CH2:19]O.C1(C)C=CC(S(O)(=O)=O)=CC=1>C(O)CCC>[C:11]1([C:9]2[S:17][CH2:18][CH2:19][O:8][C:7]=2[C:1]2[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=2)[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1

参加物

実験手順

Benzoin (106 g, 0.5 mole), 2-mercaptoethanol (43 g, 0.55 mole), and p-toluenesulfonic acid (pTSA) (5 g) are charged into a 2-liter 3-neck flask. n-Butanol (1200 mL) is added and the mixture stirred with a mechanical stirrer. The reaction is heated to reflux and the distillate passed through a vacuum-jacketed column (18 in by 3/4 in) packed with porcelain saddles. A Dean-Stark trap is placed at the top of the column to assist in the separation of the aqueous layer from the butanol/water azeotrope. After water ceases to separate, distillate is slowly removed until the vapor temperature at the top of the column reaches 117°-118°, the boiling point of dry n-butanol. The reaction mixture is cooled and seeded, and the crystalline product separated by filtration. The filtrate is returned to the reactor along with further amounts of benzoin, 2-mercaptoethanol, and pTSA as specified above. Sufficient n-butanol is added to make up for that removed in the prior reaction. When the procedure is repeated five times, the overall isolated yield of 2,3 -dihydro-5,6-diphenyl-1,4-oxathiin is 76% of theoretical.