In a similar spirit to alternative solvents, alternative reagents are relatively environmentally benign reagents that are used to replace more toxic ones. One example of an alternative green reagent is dimethyl carbonate, which can be used to effect methylation and carbonylation reactions. Traditionally phosgene or methyl iodide have been used to carry out this same reaction, but the drawback is that these reagents are significantly more toxic and are thus also more costly to dispose of properly. Dimethyl carbonate is a non-toxic compound and it can be readily produced via an oxidative reaction of methanol with oxygen, thus avoiding any environmentally hazardous synthetic procedures.

Chemical structures of dimethyl carbonate (left), phosgene (middle), and a methyl iodide (right):