An Asymmetric Dehydrogenative Diels–Alder Reaction for the Synthesis of Chiral Tetrahydrocarbazole Derivatives
作者:Xiang Wu、Hai-Jie Zhu、Shi-Bao Zhao、Shu-Sen Chen、Yun-Fei Luo、You-Gui Li
DOI:10.1021/acs.orglett.7b03251
日期:2018.1.5
An asymmetric dehydrogenative Diels–Alder reaction of 2-methyl-3-phenylmethylindoles and α,β-unsaturated aldehydes has been established. The successful in situ generation of the indole ortho-quinodimethane intermediate and the iminium activation of enals are the keys to success, providing various tetrahydrocarbazole derivatives with up to >99% ee.
iron carbonyl complexes have been applied in alkylation of indoles with various benzylic alcohols, aliphatic alcohols (butanol, ethanol, methanol and 2‐methylpentanol) via the hydrogen autotransfer strategy in mild reaction conditions. Experimental works highlight the role of the bifunctional iron complexes and the base. These iron complexes demonstrated a broad applicability in mildconditions and
An efficient route to 2,3-disubstituted indoles was developed via reductive alkylation of 2-substitutedindoles using hydrogen as a clean and atom economic reductant under ambient pressure.
An initial study has been accomplished into the synthetic feasibility of the preparation of diarylcarbenium salt via the direct coupling of aryl (or heteroaryl) aldehydes and arenes (or heteroaryl analogues) in the presence of a strong organic Brønsted acid. A number of stabilized aryl or heteroaryl(3-indolyl)carbenium ions, never previously prepared in the solid state, have been isolated in excellent
98% ee using a strong Brønsted acid as the activator. This methodology was applied in the facile synthesis of biologically active products containing a chiral indoline skeleton. The mechanism of Pd-catalyzed asymmetric hydrogenation was investigated as well. Isotope-labeling reactions and ESI-HRMS proved that an iminium salt formed by protonation of the C═C bond of indoles was the significant intermediate