The synthesis of carbonates and related compounds from carbon dioxide
The manufacture of carbonates and carbamates is essential due to their wide range of applications from polymers in foams, elastomers and engineering plastics to agrochemicals. Since there is a high demand for both types of compound, there is a commercial justification for use of phosgene in their synthesis. However, phosgene is highly toxic in small quantities. The development of an alternative reagent is therefore most desirable. This thesis relates our attempts to overcome the problem of phosgene use by utilising C02. Chapter One highlights previous research concerning the synthesis of carbonates and their derivatives from CO2. Chapter Two details the development of the reaction of CO2 to form methanesulfonyl carbonates (RO(CO)OS02Me) and carbamates (R2N(CO)OS02Me), which are precursors of carbonates and carbamates respectively. Alcohols or amines are reacted with CO2 at atmospheric pressure in acetonitrile to generate carbonate and carbamate anions in situ. Reaction with methanesulfonic anhydride leads to the methanesulfonyl carbonates and carbamates which are observed spectroscopically but are not isolable. Chapter Three explains the successful conversion of methanesulfonyl carbonates and carbamates to carbonates and carbamates, as well as testing the scope of the reaction. Chapter Four demonstrates the transfer of the synthetic methodology to multifunctional compounds to generate dendritic carbamates and highlights the various approaches used to achieve this goal. Chapter Five is the experimental section.