Asymmetric Hydrophosphonylation of α,β-Unsaturated Ketones Catalyzed by Rare-Earth Metal Complexes Bearing Trost Ligands

Abstract

Chiral dinuclear rare-earth metal complexes RE 2 L n 2 (n = 1, RE = Y(1), Eu(2), Nd(3), La(4), Gd(5); n = 2, RE = Eu(6), Gd( 7)) stabilized by the corresponding Trost ligandswere prepared and three unknown complexes 5−7 were characterized by X-ray diffraction analysis. The chiral rare-earth metal complexes 1−7 displayed high reactivity in the asymmetric hydrophosphonylation of α,β-unsaturated ketones, and 5 mol % of complex 7 together with 10 mol % of chiral diamine (1S,2S)-1,2-cyclohexanediamine were proved to be the optimal catalyst combination. Various hydrophosphonylation products with excellent yields and high to excellent enantiomeric excess (ee) values were obtained in toluene (up to 99% yield, >99% ee).

Enantioselective Michael Addition of Malononitrile to Unsaturated Ketones Catalyzed by Rare-Earth Metal Amides RE[N(SiMe3)2]3 with Phenoxy-Functionalized TsDPEN Ligands

“…In general, the use of bifunctional catalysts with both basic and acidic sites is more conducive to enantioselective modulation of the reaction. , Usually, the addition of some kinds of basic additive has a significant effect on the outcomes of the enantioselective reaction when Lewis acidic rare-earth metal complex is used as the catalyst. − So, a number of organic and inorganic bases were further investigated but the results were unsatisfactory (Table , entries 9–12). Chiral additive was also found to have a positive effect on the reaction in our previous work . However, the strategy was not helpful to the current transformation (Table , entries 13 and 14).…”

Asymmetric addition of P-H compounds to unsaturated carbonyl derivatives

“…The rare-earth-metal complex 54, bearing Trost ligands, was successfully applied in the asymmetric hydrophosphonylation of chalcones. 59 The reaction of chalcone (1, R 1 = Ph, R 2 = Ph) with diethyl phosphonate (51, R 3 = Et) resulted in the enantioselective formation of product 52 (R 1 = Ph, R 2 = Ph, R 3 = Et) when cyclohexane-1,2-diamine (55) was present in the reaction mixture (99% ee, Table 17, entry 8). Replacing diethyl phosphonate (51, R 3 = Et) with diisopropyl phosphonate (51, R 3 = iPr) did not affect the enantioselectivity (99% ee, Table 17, entry 9).…”