Thiele–winter acetoxylation of quinones. Part VI. Methoxy- and hydroxy-(phenyl)-1,4-benzoquinones and (4-substituted phenyl)-1,4-benzoquinones

Abstract

The Thiele–Winter acetoxylation of the following 1,4-benzoquinones has been studied: 2-methoxy-3-phenyl-, 2-methoxy-6-phenyl-, 2-hydroxy-5-phenyl-, 2-hydroxy-6-phenyl-, and 2-(4-substituted phenyl)-(with NO₂, Br, OMe, OH, and OAc as substituents). All these quinones undergo the reaction except (4-methoxyphenyl)-1,4-benzoquinone which gives tars. The inserted acetoxy-group always enters ortho or para to the phenyl or aryl group: it never enters ortho to the hydroxy- or the methoxy-group. 2-Hydroxy-5-(4-hydroxyphenyl)-1,4-benzoquinone has been prepared: its pK_a values are 4·18 and 9·27 at 20°.