Enantioselective Synthesis of Axially Chiral Figure-Eight Spirocycloparaphenylenes via Rh-Catalyzed Intermolecular [2
Li-Hsiang Wang1, Juntaro Nogami1, Yuki Nagashima1
1Department of Chemical Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8550, Japan.
Abstract:
We have achieved the enantioselective synthesis of axially chiral figure-eight spiro[9.9]cycloparaphenylene (CPP) tetracarboxylates with up to 75:25 er via the cationic Rh(I)/(R)-H8-BINAP complex-catalyzed chemo-, regio-, and enantioselective intermolecular double [2 + 2 + 2] cycloaddition of an achiral symmetric tetrayne with dialkyl acetylenedicarboxylates followed by reductive aromatization. The spiro[9.9]CPP tetracarboxylates are highly distorted at the phthalate moieties with large dihedral and boat angles and exhibit weak aggregation-induced emission enhancement behavior.
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