Methylation of hindered phenols, aromatic amines and carboxylic acids with dimethylcarbonate and a catalytic amount of DMAP is most effective, and the by-products are carbon dioxide and methanol. This procedure avoids the use of highly toxic dimethylsulfate and its by products are less environmentally undesirable.
F. Merger, F. Towae and L. Schroff, U. S. Patent, 1980, 4, 192,949.