Chlorine-free chemistry via dialkyl carbonates

In the last decades, due to the increasingly stringent environmental regulations, companies’ priority has become the conservation of high process performances by means of eco-compatible methodologies. In this view, green solvents and reagents dialkyl carbonates (DACs) have been extensively investigated as possible alternatives to some chlorine reagents (methyl and acyl halides, phosgene) and solvents (dichloromethane and chloroform). In this talk the following aspects and applications of chlorine-free chemistry via DAC will be addressed: Heterocycles synthesis: DACs chemistry has been proved efficient in the preparation of numerous 5- and 6-membered heterocycles including: furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines and cyclic carbamates. In these reactions, the selected DAC acts as sacrificial molecule being completely converted, at the end of the reaction, into CO2 and an alcohol. Chlorine and carbonate moieties can both be used as sacrificial groups in nucleophilic displacements, however the latter do not produce salts and harmful wastes to be disposed of and display low toxicity and high biodegradability. Renewables upgrade: The reactivity of isosorbide with DMC is an industrially relevant process as it can lead to the formation of dicarboxymethyl isosorbide, a potential monomer for isosorbide-based polycarbonate, and dimethyl isosorbide, a high boiling green solvent. The peculiar reactivity of isosorbide via chlorine-free DMC-based approaches is paving the way to several industrial potential applications. From war chemicals to green reagents: Mustard gases are vesicant and blistering agents that have been sadly used in several chemical warfare. The toxicity of these compounds is strictly related to their high reactivity. Sulfur and nitrogen (half-)mustard carbonate analogues are a new class of compounds, easily synthesized via DAC chemistry retaining the reactivity of mustard gases, but that are not toxic for the operators or the environment. Their reactivity as novel, green electrophiles and their possible potential application as green reagents will be discussed.