Why Do ManyC2-Symmetric Bisphosphine Ligands Fail in Asymmetric Hydroformylation? Theory in Front of Experiment

Abstract

Supported by a pure QM and MM treatment, stereoselectivities of rhodium systems containing the C2-symmetric ligands CHIRAPHOS (2,3-bis(diphenylphosphino)butane; 2), BINAP (2,2‘-bis(diphenylphosphino)-1,1‘-binaphthyl; 3), DIOP (2,2-dimethyl-4,5-bis((diphenylphosphino)methyl)-1,3-dioxolane; 4), and NAPHOS (2,2‘-bis((diphenylphosphino)methyl)-1,1‘-binaphthyl; 5) have been calculated with a combined QM/MM method. On the basis of the RSAI (requirement of synchronous asymmetric inductions), which states that all ligand coordination modes favor transition states with the same asymmetric induction, we demonstrate that the performance of C2-symmetric bidentate phosphine ligands is governed by two interdependencies, namely induction influence of the chelate ring and backbone flexibility. In a further step, the NAPHOS derivatives 6 (2,2‘-bis((2-dinaphthylphosphino)methyl)-1,1‘-binaphthyl) and 7 (2,2‘-bis((1-dinaphthylphosphino)methyl)-1,1‘-binaphthyl) which to our knowledge have not been tested experimentally up to ...