Cp*Co(III)-Catalyzed C(8)-Nucleophilic Cascade Cyclization of Quinoline N-Oxide with 1,6-Enyne

Base-Mediated Chemodivergent [4 + 1] and [2 + 1] Cycloadditions of N-Alkylpyridiniums and Enones

Divergent synthesis of structurally different products from the same kinds of starting materials is highly synthetically useful but very challenging. Herein, we reported a base-mediated chemodivergent [4 + 1] and [2 + 1] cycloaddition of N-alkylpyridinium and enone under mild conditions, leading to furan-fused bicycles with high diastereoselectivity and spirobicycles, respectively, from moderate to high yields. N-Alkylpyridinium salts were modular nucleophilic transfer reagents and C1 synthons, which underwent tandem Michael addition to the α,β-unsaturated ketones and cyclization under the base conditions. Late-stage derivatization of 4-propyldicyclohexylanone from an important industrial raw of liquid crystal display (LCD) screens was realized. In vitro, compound 3f exhibited good activities against human colon cancer cells (HCT116) with IC50 values in 9.82 ± 0.27 μM. Further biological evaluations investigated the mechanism of the effective inhibition of cell growth, including apoptosis ratio detection, cell cycle analysis, and migration capacity of HCT116 cells. In apoptosis effect studies, complex 3f increased the percentage of apoptotic HCT116 cells to 26.8% (15 μM).

Reversal of Regioselectivity in Asymmetric C-H Bond Annulation with Bromoalkynes under Cobalt Catalysis

Metal-catalyzed asymmetric C-H bond annulation strategy offers a versatile platform, allowing the construction of complex P-chiral molecules through atom- and step-economical fashion. However, regioselective insertion of π-coupling partner between M-C bond with high enantio-induction remain elusive. Using commercially available Co(II) salt and chiral-Salox ligands, we demonstrate an unusual protocol for the regio-reversal, enantioselective C-H bond annulation of phosphinamide with bromoalkyne through desymmetrization. The reaction proceeds through ligand-assisted enantiodetermining cyclocobaltation followed by regioselective insertion of bromoalkyne between Co-C, subsequent reductive elimination, and halogen exchange with carboxylate resulted in P-stereogenic compounds in excellent ee (up to >99 %). The isolation of cobaltacycle involved in the catalytic cycle and the outcome of control experiments provide support for a plausible mechanism.

Co(III)-Catalyzed C6-Selective C-H Activation/Pyridine Migration of 2-Pyridones with Propiolates

A versatile Co(III)-catalyzed C6-selective C-H activation/pyridine migration of 2-pyridones with available propiolates as coupling partners was demonstrated. This method features high atom economy, excellent regioselectivity, and good functional group tolerance by employing an inexpensive Co(III) catalyst under mild reaction conditions. Moreover, gram-scale synthesis and late-stage modifications of pharmaceuticals were performed to prove the effectiveness of these synthetic approaches.