Syntheses of armed-azacrown ethers by the Mannich reaction: Molecular structures and reaction mechanism for the side reaction products

Armed-azacrown ethers having phenols as a side arm were synthesized by the Mannich reaction of 2,6-disubstituted phenols with N-methoxymethylmonoaza-1 2-crown-4 ether. When the groups next to OH of the phenols are Me, i-Pr, t- Bu, OMe, F, Ph and -CH2CH=CH2, armed-azacrown ethers 13-20 were obtained. O n the other hand, the reaction using dichloro- and dibromophenols gave salt s of dihydroxydiphenylmethane with monoaza-12-crown-4 ether 21 and 22. The oxidized product 23b of 4,4'-bis(2-methyl-1-hydroxynaphthyl)methane 23a was obtained when 2-methyl-1-naphthol was allowed to react with N-methoxymethy lmonoaza-12-crown-4 ether. The structures of these salts and dinaphthylmeth ane derivatives were confirmed by X-ray crystallography. It is proposed tha t the acidity and the electrostatic charge of the phenols and naphthols are an indication of the reactivity of the 2,6-disubstituted phenols for the M annich reaction.