Enantioselective Synthesis of Axially Chiral Figure-Eight Spirocycloparaphenylenes via Rh-Catalyzed Intermolecular [2+2+2] Cycloaddition

We have achieved the enantioselective synthesis of axiallychiralfigure-eight spiro[9.9]-cycloparaphenylene (CPP) tetracarboxylateswith up to 75:25 er via the cationic Rh-(I)/(R)-H-8-BINAP complex-catalyzed chemo-, regio-, and enantioselectiveintermolecular double [2 + 2 + 2] cycloaddition of an achiral symmetrictetrayne with dialkyl acetylenedicarboxylates followed by reductivearomatization. The spiro[9.9]-CPP tetracarboxylates are highly distortedat the phthalate moieties with large dihedral and boat angles andexhibit weak aggregation-induced emission enhancement behavior.