ipso-Substitution of a sulphinyl or sulphonyl group attached to pyridine rings and its application for the synthesis of macrocycles

Abstract

A sulphinyl or sulphonyl group directly bound to the 2- or 4-position of a pyridine ring was readily displaced by several nucleophiles such as RO^–, RS^–, and CN^– to afford the corresponding ipso-substitution products. Similarly, 2-halogeno-6-methylsulphinyl- or -methylsulphonyl-pyridines also react with nucleophiles to afford 2-halogeno-6-substituted pyridine derivatives. Thus, the leaving abilities of the leaving groups fall in the order RSO₂ > RSO > Br ≃ Cl RS (R = alkyl or benzyl). The ipso-substitution can be applied to the synthesis of 2,6-disubstituted pyridino macrocycles containing both carbon–oxygen and carbon–sulphur bridges, resulting in several new macrocycles in moderate yields.