PALLADIUM-CATALYZED REGIOSELECTIVE [3- A FACILE SYNTHESIS OF TETRAHYDROFURAN DERIVATIVES(2]CYCLOADDITION OF VINYLIC OXIRANES WITH ACTIVATEDOLEFINS )

The reaction of certain activated olefins (Michael accepters) 5 with v inylic oxiranes 1 in the presence of catalytic amounts of Pd(PPh3)(4) (5 mol %) in THF at 40 degrees C gave the corresponding [3 + 2] cycloa ddition products 6. In all cases the reactions proceeded in regioselec tive manner, affording the corresponding polysubstituted tetrahydrofur an derivatives. The nature of electron-withdrawing group in activated olefins affected significantly the reactivity of substrates. Michael a ccepters having sterically less bulky electron-withdrawing groups were essential for the cycloaddition reaction, and the presence of two ele ctron-withdrawing groups at the ct-position was needed. Accordingly, a ctivated olefins having (CN, CN), (CN, CO2Et), (CN, SO2Ph), (Meldrum's type), and (SO2Ph, SO2Ph) could be used as a Michael acceptor. The pr esent reaction provides a new method for the synthesis of tetrahydrofu ran derivatives from vinylic oxiranes and Michael acceptors.