Ruthenium(II)-Catalyzed Tandem C–H Allylation and [3 + 2] Dipolar Cycloaddition to Construct Bridged Tetracycles

The ruthenium­(II)-catalyzed tandem C–H allylation
and intramolecular
dipolar cycloaddition between azomethine imines and 2-methylidenetrimethylene
carbonate is described herein. The initially formed β-substituted
allyl fragment could trigger the exotype [3 + 2] cycloaddition with
the polar azomethine group, resulting in the formation of bridged
tetracycles bearing a hydroxymethylene group at a bridgehead carbon
center. A wide substrate scope and broad functional group compatibility
were observed. The gram-scale synthesis and synthetic transformations
demonstrate the synthetic utility of this process.