Air- and moisture-stable Cu(OTf)2–bipy catalyses the addition of phenols to 1,3-dienes under aerobic conditions in a tandem hydroalkoxylation–rearrangement–hydroalkylation sequence, furnishing O-heterocycles in moderate to good yields, and can be recycled without any loss in catalytic activity.

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

Conversion of aldehydes to 1,3-dioxan-4-ones, followed by methylenation with dimethyl titanocene gave the corresponding vinyl acetals which could undergo a stereocontrolled aluminum-mediated rearrangement to afford substituted tetrahydropyrans.