Size‐ and Shape‐Selective Catalytic Dithioacetalization With an Endohedrally Functionalized Self‐Assembled Cage

An endohedrally functionalized self-assembled Fe₄L₆ cage complex can catalyze dithioacetal formation from suitably sized and shaped aldehydes and alkanethiols. The cage-catalyzed process is significantly accelerated, compared to small molecule sulfonic acid catalysis, and is selective for dithioacetal formation with fragile allyl-functionalized aldehydes that can otherwise undergo fragmentation and rearrangement. Species with putatively identical reactivity but different shapes show significant differences in conversion: p-anisaldehyde can be easily converted to a range of dithioacetals, but 9-anthraldehyde shows no reactivity. Substantially different reaction rates can be observed for isomeric species as similar as ortho- and para-anisaldehyde. These traits of mechanistic control, size-selectivity, and shape-selectivity are all the hallmarks of enzyme-mimicking catalysis.