Diverse "roof shaped" chiral diamidophosphites: Palladium coordination and catalytic applications

A series of diamidophosphite ligands of various structures and denticities were synthesized from (11S,12S)-bis(hydroxymethyl)-9,10-dihydro-9,10-ethanoanthracene as a “roof shaped” 1,4-diol. On the basis of these ligands, we obtained three types of Pd(II) allylic complexes: a P,P-chelate, a P,S-bridged head-to-tail dinuclear complex, and complexes each containing a pair of P-monodentately coordinated P-, P,N- or P,S-ligands. The structures of the ligands and their complexes were determined using 2D NMR spectroscopy. Four diamidophosphites were also characterized via their X-ray structural data. This kind of stereoselector exhibited up to 98% ee in the Pd-mediated allylic substitution of (E)-1,3-diphenylallyl acetate with C- and N-nucleophiles. In the Pd-catalyzed allylic alkylation of cinnamyl acetate with various C-nucleophiles, ee values of up to 90% were obtained. In addition, up to 71% ee was achieved in the Pd-catalyzed asymmetric amination of 2-(diethoxyphosphoryl)-1-phenylallyl acetate with aniline, which is a pioneering example of diamidophosphite-type ligand involvement in this challenging reaction. The effects of the diamidophosphite moiety and the denticity of the ligands on the catalytic activity and enantioselectivity were investigated.