Application of directed metalation in synthesis. Part 8: Interesting example of chemoselectivity in the synthesis of thioaurones and hydroxy ketones and a novel anionic ortho-Fries rearrangement used as a tool in the synthesis of thienopyranones and thiafluorenones

Abstract

Chemoselective synthesis of thioaurones or 3-hydroxy benzo[ b]thiophen-2-aryl ketones, 1-hydroxy naphtho[2,1- b]thiophen-2-aryl ketones and chalcones from N, N-diethyl- ortho-methyl sulfanyl aryl amides were described. (Benzo[ b]thiophen-2-yl) alkylates and (naphtho[2,1- b]thiophen-2-yl) alkylates undergo a novel anionic ortho-Fries rearrangement leading to (3-hydroxy benzo[ b]thiophen-2-yl) and (1-hydroxy naphtho[2,1- b]thiophen-2-yl) alkyl ketones. The hydroxy ketones were used as intermediates in the synthesis of wide range of benzothienopyranones and thiafluorenones.