Highly Efficient N-Monomethylation of Primary Aryl Amines

A highly efficient method for specific synthesis of N-monomethylarylamines is presented. Anilines were treated with acetic anhydride and triethylamine in dry CH2Cl2 to give the corresponding acetamides. The subsequent N-monomethylation of acetyl aryl amines with methyl iodide and NaH in THF introduced methyl group. Acid hydrolysis of the N-methyl acetanilides in ethylene glycol generated the corresponding N-methyl-N-aryl amines in high yields. This method was also used to synthesize (E)-2-bromo-5-(4-methylaminostyryl)pyridine that may be useful as an amyloid imaging agent for Alzheimer's disease.