1-Methoxynaphthalenes 3-7 having sulfonyl substituents SO2R (R = Me, Pri, But, OPh and N[CH2]3CH2) at the 2-position undergo displacement of the 1-methoxy group on treatment with the Grignard reagents 8a-d by a chelation-assisted conjugate addition-elimination process. Activating ability of these sulfonyl groups for the apparent nucleophilic aromatic substitution is compared with that of an ester group, isopropoxycarbonyl, and a sulfinyl group, tert-butylsulfinyl, and found to fall roughly in the order CO2Pri > SO2OPh > SO2N[CH2]3CH2 ≥ SO2Alkyl ≫ SOBut. The activation order is interpreted as being the outcome of a balance between the electron-withdrawing strength of the 2-substituents and the steric hindrance caused by the Grignard reagents 8a-d on approach to the substrates 1-methoxynaphthalenes 1-7. Asymmetric binaphthyl coupling by reaction of the chiral sulfamoyl-substituted naphthalene 20 with 1-naphthyl Grignard reagents 8d,e is also reported.
|Number of pages||7|
|Journal||Journal of the Chemical Society, Perkin Transactions 1|
|Publication status||Published - 1997 Apr 21|