Definition of the Subject: Phosgene and phosgene-like reagents are still employed in industry in the production of aliphatic and aromatic carbamates, along with their isocyanate derivatives. Those compounds are important precursors for the synthesis of pharmaceuticals, cosmetics, herbicides, pesticides, and polyurethanes commonly used in everyday life. However, despite their high reactivity and versatility, chlorine compounds usually displayed high toxicity and their reactions produce salts as by-products, which need to be disposed of. In this scenario, the development of methodologies that encompass phosgene-free insertion of carbon monoxide or carbon dioxide into substrates of interest represents an attractive and safer alternative to the carbamoylation reaction. As CO2 derivatives, dialkyl carbonates play a pivotal role in the development of chlorine-free procedure, and since the 1980, when a sustainable synthesis of dimethyl carbonate has been patented by Enichem, their used in industry has been increasing. In fact, under proper reaction conditions, dialkyl carbonates can provide alkoxycarbonylation reaction or methylation reaction according to Hard-Soft Acid-Base theory of Pearson, producing solely the corresponding alcohol and/or CO2 as reaction by-products. In this perspective, the carbamoylation reaction of amines (aliphatic and aromatic) and hydrazines through dialkyl carbonates - often used as reagents and solvents - has been extensively investigated with the aim to: (1) maximize the yields toward the desired carbamate, (2) reduce the amount of solvent used in the reaction, (3) find efficient and long-life catalysts, and (4) reduce the reaction energy consumption. Herein the most relevant investigations to date are reported and discussed. Furthermore, a section has been dedicated to the use of dialkyl carbonates for the synthesis of cyclic carbamates, nowadays extensively investigated due to their numerous applications as pharmaceuticals, herbicides, and monomers for the preparation of hyperbranched polyamines and polyurethane.
Replacement of Toxic Feedstocks in Chemical Synthesis
Pietro Tundo;
2019
Abstract
Definition of the Subject: Phosgene and phosgene-like reagents are still employed in industry in the production of aliphatic and aromatic carbamates, along with their isocyanate derivatives. Those compounds are important precursors for the synthesis of pharmaceuticals, cosmetics, herbicides, pesticides, and polyurethanes commonly used in everyday life. However, despite their high reactivity and versatility, chlorine compounds usually displayed high toxicity and their reactions produce salts as by-products, which need to be disposed of. In this scenario, the development of methodologies that encompass phosgene-free insertion of carbon monoxide or carbon dioxide into substrates of interest represents an attractive and safer alternative to the carbamoylation reaction. As CO2 derivatives, dialkyl carbonates play a pivotal role in the development of chlorine-free procedure, and since the 1980, when a sustainable synthesis of dimethyl carbonate has been patented by Enichem, their used in industry has been increasing. In fact, under proper reaction conditions, dialkyl carbonates can provide alkoxycarbonylation reaction or methylation reaction according to Hard-Soft Acid-Base theory of Pearson, producing solely the corresponding alcohol and/or CO2 as reaction by-products. In this perspective, the carbamoylation reaction of amines (aliphatic and aromatic) and hydrazines through dialkyl carbonates - often used as reagents and solvents - has been extensively investigated with the aim to: (1) maximize the yields toward the desired carbamate, (2) reduce the amount of solvent used in the reaction, (3) find efficient and long-life catalysts, and (4) reduce the reaction energy consumption. Herein the most relevant investigations to date are reported and discussed. Furthermore, a section has been dedicated to the use of dialkyl carbonates for the synthesis of cyclic carbamates, nowadays extensively investigated due to their numerous applications as pharmaceuticals, herbicides, and monomers for the preparation of hyperbranched polyamines and polyurethane.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
