Synthesis of an electron-rich KITPHOS monophosphine, preparation of derived metal complexes and applications in catalysis

Abstract

This protocol describes the synthesis of a representative example of the electron-rich biaryl-like KITPHOS class of monophosphine, 11-dicyclohexylphosphino-12-phenyl-9,10-dihydro-9,10-ethenoanthracene (H-KITPHOS). The bicyclic architecture of H-KITPHOS is constructed via [4+2] Diels-Alder cycloaddition between 1-(dicyclohexylphosphinoylethynyl)benzene and anthracene. H-KITPHOS monophosphine is prepared via an operationally straightforward three-step procedure and is isolated in an overall yield of ∼55%. The synthesis of palladium and gold precatalysts of H-KITPHOS are also described; the yields of analytically pure complexes are high (75-85% and 85-90%, respectively). The palladium complex of H-KITPHOS forms a highly active catalyst for C-C and C-N cross-coupling of a range of aryl and heteroaryl chlorides and bromides, and the electrophilic Lewis acid gold complex efficiently catalyzes a host of cycloisomerizations. The total time required for the synthesis of H-KITPHOS is 95 h; the preparation of corresponding palladium and gold precatalysts requires an additional 7-8 h, and, if necessary, crystallizations will require a further 48 h.