Recent Advances in Aerobic Oxidative of C-H Bond by Molecular Oxygen Focus on Heterocycles

Unveiling New Reactivities in Complex Mixtures: Synthesis of Tricyclic Pyridinium Derivatives

The discovery of new transformations drives the development of synthetic organic chemistry. While the main goal of synthetic chemists is to obtain the maximum yield of a desired product with minimal side product formation, meticulous characterization of the latter offers an opportunity for discovering new reaction pathways, alternative mechanisms, and new products. Herein, we present a case study on the discovery and development of a new chemical transformation using online mass spectrometry. This highly sensitive method enabled the discovery of a new reaction pathway in a catalyst-free cross-dehydrogenative coupling of 1,2,3,4-tetrahydroisoquinoline with acetone via peroxide intermediate, ultimately yielding a tricyclic pyridinium compound. Mass spectrometry was instrumental in detecting and identifying the structure of the pyridinium compound, initially formed as a trace byproduct, which allowed us to develop a general methodology for its exclusive formation.

Iron-catalyzed selective construction of indole derivatives via oxidative C(sp3)-H functionalization of indolin-2-ones

Considering the importance of developing powerful catalysts and the pharmacophore characteristics of indole derivatives, we describe a switchable approach for the iron-catalyzed oxidative C(sp3)-H functionalization of indolin-2-ones. Selective transformations displayed excellent activity and chemoselectivity using FeCl2 as the catalyst, air as the oxidant, and alcohol as the solvent. By manipulating the reaction conditions, particularly the choice of solvent, catalyst loading, and reaction sequence, a series of valuable indole derivatives, including isatins and symmetrical and nonsymmetrical isoindigos, were selectively synthesized in good to excellent yields. Furthermore, the gram-scale synthesis of compounds with biological anticancer activity under simple conditions highlights their great potential in practical applications.