Use of Dimethyl Carbonate as a Methylating Agent under Phase Transfer-Catalysed Conditions Dimethyl carbonate (as well as diethyl, diallyl, dibenzyl carbonate and ethane-1, 2-diyl carbonate) in the presence of potassium carbonate and 18-crown-6 (or Aliqual 336) is a versatile, cheap, and safer reagent for the methylation of a variety of organic substrates.