The reaction mechanism and enantioselectivity of asymmetric Michael addition reaction between alkynone (R1) with α-angelica lactone (R2) catalyzed by chiral N, N'-dioxide-Sc(III) complex were investigated at the M06/6-31G(d,p) (acetonitrile, SMD) level. The α-angelica lactone substrate could isomerize to the active enolized form in the presence of Sc(OTf)₃ reagent, assisted by the counter trifluoromethanesulfonate anion OTf. The alkynone substrate and enolized angelica lactone (or its anion) coordinated to Sc(III) center of N,N'-dioxide-Sc(III) complex catalyst simultaneously, forming a high active hexacoordinate-Sc(III) complex. The catalytic reaction occurred via a two-step mechanism, in which C₂-C_γ bond formation was predicted to be the chirality-controlling step as well as the rate-determining step (RDS), affording predominant S-enantiomer. The counterion OTf facilitated C-H construction as a proton-shuttle, producing mainly E-configuration product observed in experiment. The steric repulsion from the ortho-substituent of amide moiety as well as the chiral backbone of N, N'-dioxide-Sc(III) catalyst played the key role for chiral induction in the asymmetric reaction. The less destabilizing Pauli repulsion and more stabilizing attractive interaction, especially the orbital energy, along the si-face attack pathway enhanced the enantiodifference of the two competing pathways for high enantioselectivity. The energy barriers for E/Z isomerization of S or R-enantiomer assisted by HOTf was as high as 34.6˜35.0 kcal mol^-1, indicating that the product with Z-conformation was difficult to be obtained. These results were in good agreement with experimental observations.

在M06 / 6-31G（d，d）上研究了手性N，N'-二氧化物-Sc（III）配合物催化炔酮（R1）与α-当归内酯（R2）之间的不对称Michael加成反应的反应机理和对映选择性。p）（乙腈，SMD）水平。在抗氧化剂三氟甲烷磺酸根阴离子OTf的辅助下，在Sc（OTf）₃试剂存在下，α-当归内酯底物可以异构化为活性烯醇化形式。炔基底物和烯化的当归内酯（或其阴离子）同时与N，N'-二氧化物-Sc（III）络合物催化剂的Sc（III）中心配位，形成高活性六配位-Sc（III）络合物。催化反应通过一个两步机制，其中c ₂ -C _γ键的形成被预测为手性控制步骤以及所述速率确定步骤（RDS），得到主要的小号-对映体。抗衡离子OTf促进了质子穿梭的CH的构建，主要产生了在实验中观察到的E构型产物。来自酰胺部分的正取代基的空间排斥以及N，N'-二氧化物-Sc（III）催化剂的手性主链在不对称反应中起手性诱导的关键作用。沿硅的波利推斥力的不稳定程度较小，有吸引力的相互作用（尤其是轨道能量）更稳定面攻击途径增强了两个竞争途径的对映体差异，从而实现了高对映选择性。HOTf辅助的S或R-对映异构体E / Z异构化的能垒高达34.6〜35.0 kcal mol ^-1，表明难以获得具有Z-构象的产物。这些结果与实验观察结果非常吻合。