Carboxylic acid esters are basic compounds in organic chemistry, and have a wide range of uses as various chemical products such as pharmaceuticals, agrochemicals, cosmetics, flavors, and electronic materials, and their synthetic intermediates. As for synthetic methods of ester compounds, "Fisher esterification" is well-known since a long time ago, by which ester compounds can be synthesized using carboxylic acids and alcohols in the presence of acid catalysts.1) This reaction is reversible, and it is possible to obtain the desired esters by using excess amount of alcohols, or removing water under azeotropic condition.
As other traditional synthetic method, the methylation reaction of carboxylic acids is also known using in situ generated diazomethane. This reaction proceeds fast under neutral condition. However, since there are several reports on the explosive and cancer-causing property of diazomethane, trimethylsilyldiazomethane – hexane solution [T1146], which is less explosive, has been used as an alternative to diazomethane in recent years.
In addition to these reactions above, various kinds of synthetic methods for ester synthesis by alkylating carboxylic acids have been also reported. Alkylating reagents for ester synthesis are listed as below.