Reaction of 1,3-Oxathiin-6-ones with Bases: Synthesis of 4-Mercapto-2-pyrone
摘要:
The reaction of 4-aryl-1,3-oxathiin-6-one 3,3-dioxide 3c with secondary amine gave cinnamamides 6 and ammonium sulfinates 7. On the other hand, the reaction of 4-methyl-1,3-oxathiin-6-one 1b with LDA, followed by the addition of benzoyl chloride, gave corresponding phenacyldioxenone 8a and 5-benzoyl-4-methyl-1,3-thiodioxenone 9 in nearly 1:1 ratio, whereas the reaction with 1-benzoyl-1,2,3-benzotriazole gave only 8a in 78% yield. Thermolysis of 8a gave the corresponding 4-mercapto-2-pyrone 4a in 62% yield.
The reaction of adamantane-2-thione with propiolicacid afforded a novel type of cycloadduct, spiro[adamantane-2,2'-6'H-[1,3]-oxathiin]-6'-one (3a), in quantitative yield. The reaction of thiobenzophenone with propiolicacid gave 2,2-diphenyl-6'H-[1,3]-oxathiin]-6'-one and 4-phenyl-3-thia-3,4-dihydronaphthoic acid in 34% and 35% yields, respectively. The reaction might proceed through a concerted process
Treatment of adamantane-2-thione (1a) with propiolicacid (2a) afforded a novel type of cycloadduct, spiro[adamantane-2,2′-[1,3]oxathiin]-6-one (3a), in quantitative yield. The reaction proceeds through a concerted process, as was confirmed by kinetic analysis. Treatment of 1a with butynoic acid or phenylpropiolic acid gave the corresponding adducts regioselectively. Interestingly, only one isomer