Most of the natural products isolated at present are heterocyclic compounds, so heterocyclic compounds occupy an important position in the research of organic chemistry. A compound: 591-12-8, is researched, SMILESS is O=C1OC(C)=CC1, Molecular C5H6O2Journal, Catalysis Today called Mechanism study on asymmetric Michael addition reaction between alkynone and α-angelica lactone catalyzed by chiral N, N’-dioxide-Sc(III) complex, Author is Zuo, Yini; Meng, Xiangxiang; Hu, Changwei; Li, Jing; Su, Zhishan, the main research direction is butenolide alkynone scandium catalyst Michael addition mechanism bond order.Safety of 5-Methylfuran-2(3H)-one.
The reaction mechanism and enantioselectivity of asym. 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-Cγ bond formation was predicted to be the chirality-controlling step as well as the rate-determining step, 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 asym. reaction. The less destabilizing Pauli repulsion and more stabilizing attractive interaction, especially the orbital interaction, 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 exptl. observations.
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Reference:
Pyrimidine | C4H4N2 – PubChem,
Pyrimidine – Wikipedia