The reaction of adamantane-2-thione with propiolic acid 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 propiolic acid 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, as confirmed by kinetics. The reaction of adamantane-2-thione with 2-butynoic acid or phenylpropiolic acid gave the corresponding adducts regioselectively. Interestingly, only one isomer was obtained by the reaction of thiofenchone with propiolic acid, suggesting that the reaction proceeded diastereospecifically. Oxidation of adducts by dimethyldioxirane or m-chloroperoxybenzoic acid gave the corresponding sulfoxides and sulfones. The sulfoxides were thermally decomposed to give disulfide or another type of 1,3-oxathiin-6-one.
The reaction of di-t-butyl selenoketone with propiolic acid gave 2H,6H-1,3-oxaselenin-6-one in 78% yield, whereas the reaction of di-t-butyl thioketone with propiolic acid recovered the starting thioketone almost quantitatively.
Organo-selenium compounds S 0130Reaction of Sterically Crowded Selenoketones with Propiolic Acid. -Title reaction leads to the new 2H,6H-1,3-oxaselenin-6-ones (III) and (V) respectively. The reaction is studied in comparison to thioketones. The formation of the thiodioxenone (VII) from thiobenzophenone (VI) is reported for the first time. -(OKUMA*, K.; MAEKAWA, S.; NITO, Y.; SHIOJI, K.; Bull. Chem.
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