RESUMEN
In this study, we developed mild conditions for the synthesis of an aryl thioether via aromatic substitution using aryl halides, which is a process that has rarely been studied. Aromatic substrates such as aryl fluorides activated with a halogen substituent are difficult to use for substitution reactions, but by using 18-crown-6-ether as an additive, these were successfully converted to their corresponding thioether products. Under the conditions we established, in addition to a wide variety of thiols, less-toxic and odorless disulfides could be used directly as nucleophiles at 0 to 25 °C.
Asunto(s)
Disulfuros , Sulfuros , Estructura Molecular , Compuestos de Sulfhidrilo , HalógenosRESUMEN
In this study, we developed a method for etherification via aromatic substitution at the ipso-position of an electron-withdrawing group (EWG) that exists at the meta-position of another EWG. To heighten the reactivity of the substitution reaction, we added a t-BuOK solution in tetrahydrofuran (THF) to a mixture of an aromatic substrate, an alcoholic nucleophile, and 18-crown-6-ether in dimethylformamide (DMF), which proved to be a particularly effective sequence. Under the conditions we established, aromatic substrates that are difficult to use for substitution reactions such as aryl fluorides activated with either a bromide or a chloride substituent were aptly converted to corresponding ether products at 25 °C. This reaction would potentially be useful to link an alcohol to an additional functional group through further chemical transformations via the use of a residual bromide or chloride substituent.
RESUMEN
In this study, mild conditions for aromatic substitutions during the syntheses of aryl ethers were developed. In the reaction conditions, the choices of solvent, base, and the sequence for the addition of the reagents proved important. A wide variety of alcohols were used directly as nucleophiles and smoothly reacted with aryl chlorides that possessed either a nitro or a cyano group at either the ortho- or para-position. Controlled experiments we performed suggested that the reaction underwent a charge-transfer process mediated by a combination of DMF and tert-BuOK.