Planar Chirality Controls Diastereotopicity in [2.2]Paracyclophanyl Cyclopropenes

The synthesis of [2.2]paracyclophanyl (pCp) cyclopropenes through rhodium-catalyzed [2+1] cycloaddition of alkynes with a pCp-derived carbene is reported. The [2.2]paracyclophane topology induces diastereotopic differentiation of the alkyl substituents in the resulting cyclopropenes, which is consistently observed in their ¹H NMR spectra. Oxidation to the corresponding cyclopropenium ions removes this stereochemical bias and restores substituent equivalence, reflecting an increase in symmetry upon aromatization.