Studies on the base-catalyzed skeletal isomerization of (4) to (5) and (6) and the base-catalyzed epimerization of the hydroxy group in (5) and (6) are reported.The most plausible mechanism for the skeletal isomerization of (4) and the epimerization in (5) and (6) involves retro-aldol cleavages of (4), (5) and (6) to give an enolate (7) as the common intermediate.When 6-endo-acetoxy-9-thiabicyclo[3.3.1]nona-3,7-dien-2-one (1)1 was irradiated in methanol,2 formal 1,3-acyl3 and carbon shifts take place to give the isomeric compounds, 6-exo-acetoxy-2-thiabicyclo[3.3.1]nona-3,7-dien-9-one (2) (27%)5 and 9-endo-acetoxy-2-thiabicyclo[3.3.1]nona-3,7-dien-6-one (3) (9%)6 , respectively.In connection with the photochemical isomerization of (1) to (2), we found that a similar, but non-photochemical, skeletal isomerization takes place during hydrolysis of (1) by potassium carbonate in aqueous methanol solution. We wish to report here the remarkably smooth basecatalyzed isomerization of (1) with the epimerization of the hydroxy group to give a mixture of 6-exo-and 6-endo-hydroxy-2-thiabicyclo[3.3.1]nona-3,7-dien-9-ones (5 and 6).The keto acetate (1) was synthesized from 2,6-dihydroxy-9-thiabicyclo[3.3.1]nona-3,7-diene7 by acetylation followed by oxidation with active MnO2. The structural determination and the stereochemical assignment to (1) were derived unequivocally by the nmr spectrum.1
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.