α-Vinylation of 1,3-Dicarbonyl Compounds with Alkenyl(aryl)iodonium Tetrafluoroborates: Effects of Substituents on the Aromatic Ring and of Radical Inhibitors
1,3-dicarbonyl compounds with 4-tert-butyl-1-cyclohexenyl(aryl)iodonium 2 and 1-cyclopentenyl(aryl)iodonium tetrafluoroborates 3 are reported. Frequently, alpha-phenylations compete with the vinylations in the reaction of 1,3-dicarbonyl compounds with alkenyl(phenyl)iodoniumsalts 2a and 3a. Use of alkenyl(p-methoxyphenyl)iodoniumsalts 2b and 3b, however, leads to selective alpha-vinylation at the
Desymmetrization of cyclic 1,3-diketones <i>via</i> Ir-catalyzed hydrogenation: an efficient approach to cyclic hydroxy ketones with a chiral quaternary carbon
作者:Quan Gong、Jialin Wen、Xumu Zhang
DOI:10.1039/c9sc01769k
日期:——
We herein report an efficient method to synthesize cyclic hydroxy ketones with a chiral quaternary center. Catalyzed by an Ir/f-ampha complex, cyclic α,α-disubstituted 1,3-diketones were hydrogenated, giving mono-reduced products with both high enantioselectivities and diastereoselectivities. In addition, CC and CC bonds could survive in this catalytic system. This method was applied in the preparation
我们在此报告了一种合成具有手性季铵中心的环状羟基酮的有效方法。在 Ir/f-ampha 配合物的催化下,环状 α,α-二取代 1,3-二酮被氢化,得到具有高对映选择性和非对映选择性的单还原产物。此外,C C 和 C C 键可以在该催化体系中存活。该方法用于制备(+)-雌酮。在这种化学转化中没有观察到二醇。由于空间位阻,实现了对映异构体和非对映异构体的诱导。
Diboron-mediated palladium-catalyzed asymmetric transfer hydrogenation using the proton of alcohols as hydrogen source
The developments of hydrogensources stand at the forefront of asymmetric reduction. In contrast to the well-studied alcohols as hydrogensources via β-hydride elimination, the direct utilization of the proton of alcohols as a hydrogensource for activator-mediated asymmetric reduction is rarely explored. Herein we report the proton of alcohols as a hydrogensource in diboron-mediated palladium-catalyzed
quaternary stereocenter with high enantioselectivity and diastereoselectivity. Mechanistic studies and DFT calculations suggested that the rarely observed diastereoselectivity reversal is ascribed to the charge-charge interaction between the palladium and aromatic ring of the substrate, which could not only result in the reversal of the diastereoselectivity, but also improve the reactivity.