Inherently Chiral Calixarenes from Catalytic Enantioselective Transannular Arene-Arene Cross-Coupling Reaction

Under the catalysis of PdBr2 and a chiral phosphoramidite ligand derived from R-3,3'-bis(trifluoromethyl)-[1,1'-binaphthalene]-2,2'-diol, the upper-rim mono (2-bromoaroyl)-substituted calix[4]arene derivatives underwent facile enantioselective desymmetrization reaction to afford 9H-fluorene-embedded inherently chiral cyclophanes in good yields with ee up to 94%. The transannular arene-arene cross coupling reaction proceeded most probably through an oxidation addition of Caryl-Br bond to ligated palladium catalyst, an unusual long range 1,5-palladium migration fol-lowed by the intramolecular arylation sequence. Because of the macrocyclic strain, the newly formed 9H-fuorene segment adopts curved structure, rendering highly rigid inherently chiral macrocycles unique chiroptical property.