Iridium complexes of chiral oxazoline-based P,N-ligands provedto be efficient catalysts for the enantioselective hydrogenationof 2-aryl- and 2-alkyl-4 H-chromenes.The best results were obtained with a ligand derived from threonine(ThrePHOX), which induced ee values of 95% to >99% inthe hydrogenation of 2-methyl-, 2-cyclohexyl- and various 2-aryl-substitutedchromenes.
手性恶唑啉基P,N-配体的铱配合物被证明是2-芳基-和2-烷基-4 H-色烯对映选择性加氢的有效催化剂。使用苏氨酸衍生的配体(ThrePHOX)获得了最好的结果。在 2-甲基-、2-环己基-和各种 2-芳基-取代的色烯的氢化中诱导 ee 值达到 95% 至 >99%。
Visible-light-driven thio-carboxylation of alkynes with CO2: facile synthesis of thiochromones
carboxylation of alkynes with CO2 is a sustainable and important strategy to generate valuable acrylate derivatives from both readily available starting materials. Such protocols, however, always suffer from the use of excess metallic reagents and transitionmetal residue. Herein, we report the first thio-carboxylation of alkynes with thiophenols and CO2, which is a visible-light-driven and transition metal-free
用 CO 2对炔烃进行双官能团羧化是一种可持续且重要的策略,可以从两种现成的起始材料中生成有价值的丙烯酸酯衍生物。然而,此类协议总是会使用过量的金属试剂和过渡金属残留物。在此,我们报道了炔烃与苯硫酚和 CO 2的第一次硫代羧化反应,这是一个可见光驱动且无过渡金属的过程。与之前通过CO 2的双电子活化对炔烃进行羧化反应相比,机理和计算研究表明 CO 2的单电子活化参与硫代羧化,呈现独特的β-羧化。随后的环化酰化有效地提供了重要的硫色酮。此外,一锅法具有温和的反应条件(室温,1 个大气压的 CO 2)、高化学和区域选择性、易于扩展和易于将产物衍生为生物活性化合物。
Rh-Catalyzed Asymmetric Hydrogenation of 2-Substituted 4H-(Thio)chromenes for Synthesis of Chiral (Thio)chromanes
Rh-catalyzed asymmetric hydrogenation of 2-substituted 4H-thiochromenes and 4H-chromenes was successfully developed. This method provided highly efficient access to a series of chiral 2-substituted thiochromanes and chromanes in high yields with excellent enantioselectivities (up to 99% yield, 86–99% ee). The obtained chiral 2-substituted thiochromane products were also successfully transformed to