Miss Qin Han Teo
The formation of methylenated bicyclic adducts was achieved by formal (4+3) cycloadditions of epoxy allylsilanes with different dienes. The epoxy allylsilane functions as a dienophile in the (4+3) cycloaddition reaction. The oxirane in the epoxy allylsilane, once activated by a Lewis acid, serves as a good dienophile while the allylsilane moiety completes the construction of the cycloadducts by desilylation of the (trimethylsilyl)methyl group. Epoxy allylsilane reacts with simple dienes in the presence of a catalytic amount of TESOTf results in the formation of intermolecular (4+3) cycloadducts with moderate yields. The epoxy allylsilane tethered to furan with TESOTf constructs cycloadducts with 6,7- and 5,7-fused bicyclic systems in excellent yields. Both endo and exo cycloadducts are formed in the cycloaddition reaction. The synthesis of the dienophile precursor and the inter-and intramolecular (4+3) cycloadditions of epoxy allylsilanes with different dienes to provide methylenated cycloheptanes are presented.