Ruthenium-catalyzed one-pot double allylation/cycloisomerization of 1,3-dicarbonyl compounds leading to exo-methylenecyclopentanes

The ruthenium-catalyzed one-pot double allylation/cycloisomerization of 1,3-diketones and methyl acetoacetate gave exo-methylenecyclopentanes in moderate to good yields with high isomer selectivity. The double allylation step effectively proceeded in the presence of a Ru(II) precatalyst, Cp*RuCl(cod)], in 1,2-dichloroethane at 90 degrees C. The subsequent cycloisomerization was carried out upon addition of triethylsilane as a hydride source without purification of a 1,6-diene intermediate. Detailed inspections of the reaction by (1)H NMR spectroscopy disclosed that triethylsilyl methyl ether plays an important role for the conversion of a ruthenium(IV) allyl complex formed in the double allylation step into a ruthenium(II) species required for the cycloisomerization.