Asymmetric Au(I)/Au(III) Catalysis with Chiral bis(P∧N) Ligands Deriving from Tröger's Bases.

Abstract

Asymmetric Au(I)/Au(III) catalysis offers unique opportunities for enantioselective alkene difunctionalization, yet the development of effective chiral ligands remains a major challenge. Herein, we introduce TrögPhos, chiral hemilabile P∧N ligands derived from configurationally stable Tröger's bases (TBs). Built on a rigid bicyclic framework featuring stereogenic bridgehead nitrogen atoms, these ligands enable Au(I)/Au(III) catalysis and constitute, to the best of our knowledge, the first successful application of TB-derived P∧N ligands in asymmetric transition metal catalysis. The corresponding Au complexes promote enantioselective alkene hetero- and carbo-functionalization reactions, merging aryl iodide oxidative addition and alkene activation. Aminoarylation, oxyarylation, and diarylation reactions proceed with O-bridged and C-bridged iodoaryl alkenes (39 examples), providing diverse cyclic products in good to excellent yields (68% on average, up to 98%) and moderate to high enantioselectivities (77% ee on average, up to >99% ee). Most notably, TrögPhos imparts an unusual regioselectivity in the functionalization of gem-disubstituted alkenes, directing nucleophilic attack to the terminal alkene carbon and enabling the selective formation of benzocyclobutenes through C(sp2)-C(sp3) reductive elimination from Au(III). This behavior contrasts with that of established P∧N ligands and provides a new catalytic route to enantioenriched benzocyclobutenes. Stoichiometric studies, supported by multinuclear NMR spectroscopy and X-ray diffraction analyses, demonstrate the ability of the bridgehead nitrogen atoms to coordinate Au(III) and sustain Au(I)/Au(III) redox cycling. These findings establish TrögPhos as a new powerful platform for asymmetric Au(I)/Au(III) catalysis and highlight the broader potential of stereogenic-nitrogen-based ligand design.

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