Enantioselective Construction of Consecutive Tetrasubstituted Stereogenic Centers by Reaction of α-Substituted β-Nitroacrylates with Oxazol-5-(4<i>H</i>)-ones Catalyzed by Cinchona Alkaloid Sulfonamide Catalysts
The enantioselective reaction of α-substituted β-nitroacrylates with oxazol-5-(4H)-ones (oxazolones) to construct consecutive tetrasubstituted stereogenic centers was accomplished. A cinchonaalkaloid sulfonamide catalyst afforded products bearing vicinal chiral centers with excellent enantio- and diastereoselectivities. The obtained products were successively converted into various chiral compounds
完成了α-取代的 β-硝基丙烯酸酯与 oxazol-5-(4 H )-ones (oxazolones) 的对映选择性反应,构建连续的四取代立体中心。金鸡纳生物碱磺酰胺催化剂为带有邻位手性中心的产物提供了出色的对映和非对映选择性。将所得产物连续转化为各种手性化合物而不损失其对映体纯度。此外,还进行了密度泛函理论 (DFT) 计算,以阐明观察到的反应立体选择性的机制和起源。
Pd(OAc)<sub>2</sub>-Catalyzed Asymmetric Hydrogenation of α-Iminoesters
An efficient Pd(OAc)(2)-catalyzed asymmetric hydrogenation of alpha-iminoesters was realized for the first time at 1 atm hydrogen pressure and room temperature. Pd(OAc)(2), a less expensive Pd salt with low toxicity, was found to be the most suitable catalyst precursor rather than Pd(TFA)(2) which is usually the catalyst of choice for homogeneous asymmetric hydrogenation. The chiral alpha-arylglycine fragments are widely found in many chiral products and bioactive molecules.
Enantioselective Rhodium-Catalyzed Addition of Arylboronic Acids to α-Ketoesters