Several cyclic and acyclic enones and their ethylene ketals/acetals were reacted with dimethyl diazomalonate under bis(acetylacetonato)copper(II) catalysis. Cyclohex-2-en-I-one (1) yielded only C-H insertion products 2 and 3, whereas but-3-en-2-one gave a cyclopropane albeit in very low yield. The ethylene ketals 6 of cyclopent-2-en-I-one and cyclohex-2-en-I-one gave the corresponding cyclopropanes 7, which were in turn cleaved to the ketones 8. The acetals 9 and 10 of crotonaldehyde ((E)-but-2-enal) and cinnamaldehyde ((E)-3-phenylprop-2-enal), respectively, yielded C-0 insertion and [2,3]-sigmatropic rearrangement products l l b , c and 12b, c, as well as cyclopropanes l l a and l l b , all of which are polyfunctional and synthetically useful compounds.
')
See, r.g., the syntheses via dihydropyrazoles [I], via enones, dihromomdlonates, and Bu,Sb , from bromoesters and enones in the presence of bases [3], and vio enone threitol ketals and Simmons-Smith reagent with high enantiomeric purity [4]; for cyclopropanes in general, see . Scheme 1 2037 6 + N2<Co2Me PhHreflux C02Me ICu(acac),l 1 MDM 2 3 C0,Et CH&O H-co2Me C02Me 4 5 ') This interesting topic was the subject to an excellent review 1151