Synthesis of [1,4]dioxino[2,3-c]quinolines and [1,4]dioxepino-[2,3-c]quinolines and their 1-sulfur analogues

The synthesis of [1,4]dioxino[2,3-c]quinolines and [1,4]dioxepino[2,3-c]qui nolines with restrained conformation of the piperidine ring, which represen t 1,2,3,4-tetrahydroquinolines containing two heteroatom substituents at po sitions 3 and 4, is described. In addition, the application of this approac h for the synthesis of 1-sulfur analogues is discussed. Both series are hel pful tools for three-dimensional quantitative structure-activity relationsh ip studies in the field of modulators of multidrug resistance.