Cycloaddition of tungsten−η1-3-furyl compounds with a variety of organic alkenes and alkynes proceeds smmothly at ambient conditions, yielding tungsten−η1-oxabicyclo[2.2.1]heptene and −η1-oxabicyclo[2.2.1]heptadiene compounds in high regioselectivities and stereoselectivities. The cycloaddition is proposed to proceed via a mechanism involving a zwitterion intermediate. Cleavage of oxygen bridges of η1-oxabicyclo[2.2.1]heptenes and η1-oxabicyclo[2.2.1]heptadienes occurs on treatment of CF3SO3H and Lewis acid, leading to atypical carbon−carbon bond scission and deoxygenation reactions to give highly substituted benzene and furan derivatives, respectively. The role of the tunsten fragment in these demetalation reactions is discussed in detail.

Treatment of tungsten-q~-7-oxabicyclo[2.2. llheptadiene and -q1-7-oxabicyclo[2.2.l]heptene with CF3S03H leads to atypical carbon-carbon bond scission and deoxygenation; the reaction intermediates in the bond scission involves a tungstenq 1-2-h ydrofurylium cation.

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