The effect of substitution at the 'central methane' on the photoreactivity of 3-benzylfuran-2(5H)ones 5a-g was investigated. Despite its di-pi-methane structure, photochemical arylation was effected to give substituted indenofuranones 6 in good yields. Only the substitution by phenyl caused the di-pi-methane rearrangement to give a cyclopropanofuranone 18g in moderate yield.
A Breakthrough for the Photochemical Arylation in the 3-(Phenylmethyl)-2(5H)-furanone system Leading to the Tetrahydroindenofuranone System
The photochemistry of the 'central methane'-substituted 3-benzyl-2(5H)-furanone system (1) is described. Despite its di-pi-methane structure, photochemical arylation was found to predominate in place of the di-pi-methane rearrangement, and gave substituted tetrahydroindenofuranones (2) in good yields.
Heterocyclic prostaglandins. III. Synthesis of 10-oxa-11-deoxyprostaglandin E2.
作者:AKIHIKO ISHIDA、SHIGEYOSHI SAIJO、JUNICHI HIMIZU
DOI:10.1248/cpb.28.783
日期:——
The decarboxylation of various 1-substituted-3, 7-dioxabicyclo[3.3.0]octane-2, 8-diones (2b-j) was in vestigated. On treatment with potassium acetate in aqueous pyridine under reflux, all the compounds (2b-j) examined were decarboxylated in high yields to give the corresponding trans-3-hydroxymethyl-4-butanolides (3b-j). The synthesis of 10-oxa-11-deoxyprostaglandin E2 (1a) from the compounds 3i and 3j is also described. The Moffatt oxidation of 3i and the Wittig reaction of the resulting aldehyde (6a) with dimethyl 2-oxoheptylphosphonate gave an enone (7a), which was converted into 10-oxa-11-deoxyprostaglandin E2 methyl ester (8a) and the C15-epimer (9a) by NaBH4 reduction. Hydrolysis and subsequent relactonization of 8a gave 1a in 88% yield. A similar treatment of 9a gave 1b in 87% yield. Using a similar sequence of reactions, 1a and 1b were also prepared from the nitrile analog 3j via 8b and 9b.