Allylsilane and diallylsilane reactions with functionalized ethylene ketals or benzodioxoles

The bis-allylation of ethylene ketal and catechol ketal derivatives of 2,5-hexanedione occurred with a great stereoselectivity. The tetraallylation of bis-catechol ketal derivatives of 2,5-hexanedione and 2-methyl-1,3-cyclohexanedione or the diallylation of 4-phenylbutan-2-one derivatives arise in good yields and these compounds were suitable substrates for ring-closing metathesis leading to 4,4-dialkylcyclopentenes. Condensation of 1,8-bistrimethylsilyl-2,6-octadiene (Bistro) with 4-phenylbutan-2-one catechol ketal derivatives or 2-methylcyclohexan-1,3-dione mono catechol ketal afforded in good yields cyclic and tricyclic products 12 or 23, respectively.