Oxidative Cyclization of o-(1-Hydroxy-2-alkynyl)-N-tosylanilides for the Synthesis of 4-Quinolones

Abstract

The treatment of easily accessible o-(1-hydroxy-2alkynyl)-N-tosylanilides 1 with excess manganese(IV) oxide in the presence of substoichiometric tetrabutylammonium iodide (TBAI) in chloroform (or in the absence of TBAI in dimethylformamide, DMF) promoted a sequential oxidation/intramolecular hydroamination to give 4-quinolones 3 and/or (Z)-2-alkylidene-3-oxindoles (Z)-4 in good yields. Possibly, MnO 2 played dual roles as an oxidant and as a Lewis acidic activator of intermediary ynones 2. The product distributions between 3 and (Z)-4 could be controlled by the choice of solvents.

Recent Developments in the Synthetic Strategies of 4‐Quinolones and Its Derivatives

“…[61] The oxidative processes carried out in the presence of oxygen and visible-light-induced photocatalysis are considered as a green and efficient synthetic strategy to achieve the synthesis of a wide variety of medicinal compounds. Xiaochen et al reported a mild, highly efficient, atom economical onepot synthetic strategy for the synthesis of 4-quinolones (69) . The presence of small electron-withdrawing halogen atom or groups such as methyl led to better yields and high ee (76-86 %).…”

“…The proposed mechanism of the reaction is dissipated below in figure 20. [69] Babu et al, developed a facile, three-component synthesis of 2-amino-3-carboxylate-4-quinolones (101). It was observed that the reaction between phosphorus ylides (97, 1 mmol) and isocyanate (98, 1 mmol) was carried out in 1, 2-DCE at room .…”