Catalyst-Free Double CH-Functionalization of Quinolines with Phosphine Oxides via Two S<sub>N</sub><sup>H</sup>Ar Reaction Sequences
Б. А. Трофимов, Pavel А. Volkov, Anton A. Telezhkin, Kseniya O. Khrapova, Nina I. Ivanova, Alexander I. Albanov, Nina K. Gusarova
Abstract
Quinolines undergo catalyst-free double CH-functionalization upon treatment with secondary phosphine oxides (70–75 °C, 20–48 h) followed by oxidation of the intermediate 2,4-bisphosphoryltetrahydroquinolines with chloranil. The yields of the target 2,4-bisphosphorylated quinolines are up to 77%. Thus, a double-SNHAr reaction sequence in the same molecule of quinoline has been realized. In the case of 2,4-bisphenylphosphoryltetrahydroquinolines, the aromatization occurs with elimination of one molecule of diphenylphosphine oxide to afford the products of monofunctionalization, 4-diphenylphosphorylquinolines, in 40–45% yields.