A novel highly regio- and diastereoselective phosphine-catalyzed
[2 + 4] annulation of benzofuran-derived azadienes (BDAs) with acidic
hydrogen-tethered allyl carbonates has been developed ingeniously.
A range of functionalized spiro[benzofuran-cyclohexane] derivatives
with two consecutive stereocenters were smoothly obtained in moderate
to excellent yields under mild reaction conditions from readily available
materials. Moreover, this method is a practical and scalable strategy
that creates the core structural motif of the fungistatic drug, griseofulvin.