X=Y-ZH systems as potential 1,3-dipoles. Part 33. Generation of nitrones from oximes. Tandem Michael addition-1,3-dipolar cycloaddition reactions. Class 2 processes in which the dipolarophile is located within the oxime.
corresponding C-alkenyl nitrones which undergo an intramolecular cycloaddition. The cycloaddition can occur by one of two modes leading to either bridged- or fused-isoxazolidines. The latter is preferred in most cases except that of the C-(3-alkenyl) nitrone which gives exclusively the bridged-ring product and the C-(4-alkenyl)nitrones derived from N-allylpyrrole-2-carboxyaldehyde oxime which gives both bridged-
Intramolecular 1,3-dipolar addition reactions of nitrones were investigated. Four alkenyl nitrones were studied: 2-allyl-, 2-(3-butenyl)-, 2-(4-pentenyl)-, and 2-(9-decenyl)-N-methylcyclohexanimine N-oxides. Among these, 2-(3-butenyl)-N-methylcyclohexanimine N-oxide was found to cyclize most smoothly, giving a perhydroindene derivative as a single regio- and stereoisomer. A perhydroazulene derivative
Substituted hydrazulenones via cyclopropanone addition, cyclopropanol rearrangement, and a retroaldol/re-aldol sequence
作者:Valérie Reydellet、Paul Helquist
DOI:10.1016/s0040-4039(01)93365-9
日期:——
2-Substituted cycloheptanone enolates add to cyclopropanone to give adducts that undergo base-promoted rearrangement followed, in most cases, by a retroaldol/re-aldol sequence to give conjugated hydrazulenones that are substituted at a position γ to the carbonyl group.