Ruthenium‐Catalyzed One‐Pot Double Allylation/Cycloisomerization of 1,3‐Dicarbonyl Compounds Leading to exo‐Methylenecyclopentanes

Abstract
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 RuII precatalyst, [Cp*RuCl(cod)], in 1,2‐dichloroethane at 90 °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 1H 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.