Application of alkane-diyl based chiral phosphine-aminophosphine (P-NP) and thioether-aminophosphine (S-NP) ligands in Rh-catalyzed asymmetric hydrogenation

Rhodium(I)-complexes of five new alkane-diyl based phosphine-aminophosphine (P,NP) type chiral lig-ands (Ph2PCH(CH3)(CH2)nCH(CH3)N(R1)PR2 2 (n = 0-2, R1 = Me, Et, iPr, R2 = Ph, Cy)) and a thioether-aminophosphine type compound (( S,S)-PhSCH(CH3)(CH2)CH(CH3)N(iPr)PPh2) have been synthesized. The investigation of the coordination chemistry of structurally analogous systems by NMR and IR spectroscopy and in one case by X-ray crystallography enabled the comparison of the effect of (i) the ligand backbone length, (ii) the N-substituent, (iii) the type of the coordinating functionality and (iv) the P-substituent in aminophosphine moiety on the stereo-electronic properties of the complexes. The novel Rh-compounds were tested in the asymmetric hydrogenation of a broad range of prochiral substrates including dimethyl itaconate, dehydroaminoacid derivatives and alpha,beta-unsaturated enol ester phosphonates. Catalysts modi-fied by the pentane-2,4-diyl based phosphine-aminophosphine ligands provided superior catalytic per-formance compared to the analogous butane-and hexane-diyl based systems and thioether containing compound. Most importantly, by the proper choice of the N-substituent outstanding enantioselectivities could be obtained in the asymmetric hydrogenation of acetamidocinnamic acid derivatives (up to 98% ee) and enol ester phosphonates (up to 97% ee).(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

In this study, five new Rhodium(I)-complexes of alkane-diyl based phosphine-aminophosphine (P,NP) type chiral ligands were synthesized and their coordination chemistry was investigated. The results showed that the ligand backbone length, N-substituent, coordinating functionality, and P-substituent in the aminophosphine moiety played a role in the stereo-electronic properties of the complexes. The catalysts modified by pentane-2,4-diyl based phosphine-aminophosphine ligands exhibited superior catalytic performance and excellent enantioselectivities in asymmetric hydrogenation reactions.