Publication Details (including relevant citation information):
Eur. J. Org. Chem., 2005, 593-599
The carbonyl ylide 1,3-dipoles generated by dirhodium tetraacetate-catalyzed decomposition from 1-diazo-5-phenylpentane-2,5-dione (4) and 1-(1-acetylcyclopropyl)-2-diazo-ethanone (5) cycloadd to substituted methylenecyclopropanes2a–e and bicyclopropylidene (3) to give substituted mono-, di-, and trispirocyclopropanated 8-oxabicyclo[3.2.1]octan-2-ones 7, 8, and 11 and 7-oxabicyclo[2.2.1]heptan-2-ones 10 and 12 in 6–75 % yields with different regio- and stereoselectivities. The structures of the two isomeric cycloadducts endo- and exo-10d formed from the carbonyl ylide derived from 5 and methyl 2-chloro-2-(cyclopropylidene)acetate (2d) were confirmed by X-ray crystal structure analyses. (Diphenylmethylene)cyclopropane and trans-3-methylenecyclopropane-1,2-dicarboxylate (diethyl ester of Feist’s acid) did not undergo such cycloadditions, while methylenecyclobutane (13) afforded a mixture of [3+2] and [2+1] cycloadducts 14 and 15 in 28 and 29 % yields, respectively. The scope and limitations of these cycloadditions as well as the influence of different factors upon their regio- and stereoselectivities are discussed.