中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
—— | (5S,9R,21R,25S)-7,7,23,23-tetramethyl-6,8,22,24-tetraoxa-3,11,19,27-tetrazaoctacyclo[13.13.0.02,12.04,11.05,9.018,28.019,26.021,25]octacosa-1(15),2(12),3,13,16,18(28),26-heptaene | 1311201-21-4 | C24H24N4O4 | 432.479 |
—— | (5S,9R,21R,25S)-6,8,22,24-tetraoxa-3,11,19,27-tetrazaoctacyclo[13.13.0.02,12.04,11.05,9.018,28.019,26.021,25]octacosa-1(15),2(12),3,13,16,18(28),26-heptaene | 1311201-22-5 | C20H16N4O4 | 376.371 |
A monocationic Zn(II) acetate complex of a C2-chiral bisamidine-type sp2N bidentate ligand (LR) possessing two dioxolane oxygen n orbitals in the reaction site catalyzes, without the use of an external base, a highly efficient asymmetric 1,3-dipolar cycloaddition (1,3-DC) of tridentate α-substituted α-imino esters with acrylates, attaining up to >99:1 enantiomeric ratio with perfect regio- and diastereo-selectivities. A catalyst loading of 0.1 mol% is generally acceptable to furnish various chiral multi-substituted prolines. Both (S)-α-imino ester and the R enantiomer show a high level of enantioselectivity. An overall picture of the present 1,3-DC has been revealed via analyses of substrate structure/reactivity/selectivity relationships, NMR, MS, X-ray diffraction, 12C/13C isotope effects, rate law, and kinetics. The first success in the high performance 1,3-DC is ascribed to i) a Brønsted base/Lewis acid synergistic effect of [Zn(OAc)LR]OTf (R cat); ii) the existence of the n orbital, which determines the position of the intermediary N,O-cis-Zn enolate (dipole) by an n-π* non-bonding attractive interaction between the oxygen atom in LR and the C=N moiety of the dipole; and iii) utilization of chelatable α-imino esters capturing Zn(II) as a tridentate ligand. A 12C/13C analysis has clarified that a stepwise 1,3-DC mechanism is operating.