Ring-opening of tertiary cyclopropanols derived from β-diketones

The ring-opening reaction of 1,2-di substituted cyclopropanols, prepared from beta-diketones, mediated by Cu(NO3)(2), p-TsOH, and NaOH is reported. The Cu(II)-mediated ring-opening of cyclopropanols gave alpha-methylene-gamma-diketones in good yields. The reaction took place at the less substituted carbon of the cyclopropanols, involving mild conditions and a simple procedure. The reaction induced by p-TsOH in CH2O2 afforded alpha-methyl-gamma-diketones as the major product with minor amounts of 8-diketones. The 2,3,5-tri substituted furans were obtained in high yields when the ring-opening reaction was mediated by p-TsOH in methanol under reflux conditions. In the presence of sodium hydroxide the reaction proceeded smoothly in preference to the formation of beta-diketones, particularly for substrates with an aromatic group on the cyclopropane. (c) 2006 Elsevier Ltd. All rights reserved.