A highly enantioselective [4+2] cycloaddition involving aldehydes and β,γ-unsaturated-α-keto esters
摘要:
A stereoselective inverse electron demand oxo-Diels-Alder reaction involving electron poor dienes (gamma-aryl-beta,gamma-unsaturated-alpha-keto ester) and electron rich dienophiles has been studied. These cycloaddition reactions are extremely useful for the construction of O-, N-, S-centered heterocyclic compounds, which are routinely used in both synthetic organic and medicinal chemistry. The [4+2] hetero cycloaddition reactions involving various aldehydes and beta,gamma-unsaturated-alpha-keto esters were carried out in which three different types of substituted proline catalysts were examined. For these reactions, high selectivities (enantiomeric excess 93-98%) were obtained using catalyst 3. Due to the bulkiness of catalyst 3, compared to the other catalysts tested, it is more efficient at catalyzing these type reactions. (C) 2017 Elsevier Ltd. All rights reserved.
手性铜( II )络合物催化丙二酸酯对β,γ-不饱和-α-酮酯的对映选择性迈克尔加成反应,实现了高产率(高达96%)和高ee(高达92%) 。手性配体同时利用了联萘基和脯氨酸部分,并且可以容忍具有不同电子和空间特征的取代基。反应可以在温和的条件下进行,并且可以在不损失产率和对映选择性的情况下实现克级反应。
diastereo-, and enantioselective Diels–Alderreaction of β,γ-unsaturated α-ketoesters with (E)-1-phenyl dienes has been accomplished by using a stable and easily available chiral N,N′-dioxide/zinc(II) complex as catalyst. Only one isomer of the corresponding cyclohexenes with three chiral centers was obtained in good to excellent yields with excellent ee values under mild reaction conditions. The configurations
A highlyenantioselective Michael addition of allomaltol (5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one) to both aromatic and aliphatic β,γ‐unsaturated α‐ketoesters has been realized. Under the catalysis of a chiral bifunctional tertiary amine‐squaramide that bears a (1R,2R)‐1,2‐diphenylethane‐1,2‐diamine scaffold, the reaction proceeded smoothly with high levels of enantioselectivity to give the desired products
Michael Addition–Lactonization of Arylacetyl Phosphonate to β,γ-Unsaturated α-Keto Esters for the Synthesis of Chiral <i>syn</i>-3,4-Dihydropyranones and 5,6-Dihydropyranones
Catalytic asymmetric Michael addition–lactonization of arylacetyl phosphonates to β,γ-unsaturated α-ketoesters by a chiral bifunctional thiourea–tertiary amine was established. Using the developed protocol, a range of optically pure syn-3,4-dihydropyranones were generated in good yields with good to excellent stereoselectivities (up to >20:1 dr and 99% ee). Meanwhile, when stoichiometric diisopropylethylamine
Reported herein is an inverse-electron-demand oxa-Diels–Alder reaction that is remotely β,γ-regioselective with β,γ-unsaturated amides and β,γ-unsaturated-α-ketoesters using a bifunctional catalyst. It can provide different kinds of dihydropyrans bearing three subsequent chiral carbon centers in good to high yield (61–99%) and with complete enantioselectivity (99 to >99% ee). Furthermore, a larger-scale