No abstract

No abstract

The endocyclic C᎐ ᎐ C bond of 3-allyltetronic acid 1 can be selectively oxidised with dimethyldioxirane to give 3-allyl-3hydroxydihydrofuran-2,4-dione 2 while 3-exo-alkylidenedihydrofuran-2,4-diones 9 are rapidly autooxidised to furnish the spirotricyclic hemiketal endoperoxide lactones 10. Scheme 2 Normal side-chain epoxidation of 3-allyltetronate 5: a) DMD, Ϫ78 ЊC → rt, 12 h; b) MCPBA, CHCl 3 , NaHCO 3 , rt, 12 h. Scheme 3 Formation and reductive ring opening of endoperoxides 10.

No abstract

Allyl tetronates 3 can be selectively converted either (in acetonitrile) into Claisen‐rearranged 3‐allyltetronic acids 5 or (in toluene) into novel Claisen−Conia‐rearranged 3‐(spirocyclopropyl)dihydrofuran‐2,4‐diones 6, featuring up to three new stereogenic centres. The mechanism and the stereochemistry of this process is discussed and an X‐ray crystal structure of one of the two diastereoisomers of (±)−6c is presented.