Regardless of the complexity of the molecule to be manufactured, chemists always try to find a way to reduce the reaction time and the number of steps required for synthesizing a molecule because of a constant concern regarding costs and profitability.
Many studies have been conducted for the purpose of controlling the various parameters capable of influencing the unfolding and speed of a reaction. Additives, such as solvents, catalysts, have been widely used. Although these compounds stimulate the reaction medium, they are sometimes toxic to man and the environment, and they require expensive post-treatments such as neutralization, washing, drying, filtration.
Today, the trend is toward manufacturing processes that are simple, low in cost, and respectful of man and his environment.
Some physical processes have been tested: the use of ultrasounds, high frequencies, and recently, microwaves.
The various tests conducted using dielectric heating, that is to say, heating under microwave frequencies or high frequencies, have shown the potential value of this new technology: indeed, dielectric heating permits considerable time and energy savings, combined with lower investment costs; the reactions no longer require the use of any solvent or catalyst; burn-up and unwanted reactions are avoided.
Although today there are available many types of high-frequency and microwave applicators, they are all nonetheless configured in such a way that the reaction medium is continuously exposed to electromagnetic waves in order to be able to benefit from the advantages inherent in this new technology. The amount of material processed in this manner is limited, because it depends on the dimensions of the waveguides that are themselves standardized.
USPTO Backgrounds
USPTO Backgrounds