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Arthur T Knackerbracket has found the following story:

Esters are among the most important classes of compounds in organic chemistry. Simple esters are known for their pleasant, often fruity aromas. Meanwhile, the larger, more complex examples have a wide spectrum of industrial uses, ranging from lenses and moisturizers to “green” fuel (biodiesel).

A common way to produce complex esters is to react simpler carboxylic esters with alcohols. Known as trans-esterification, this process typically relies on metal salts as catalysts. However, such catalysts tend to be expensive and/or polluting. Worse still, if the ester is long and flexible, it tends to wrap around the metal center through coordination bonds. By effectively tying up the metal, this “chelation” shuts down the reaction.

Now, a team at Nagoya University has developed a catalyst that dramatically expands the substrate range of trans-esterification. To avoid chelation, the researchers used a metal-free catalyst, tetramethylammonium methyl carbonate (TMC). Under the right conditions, TMC reacts in-situ with an alcohol to form an alkoxide ion, which then attacks the starting ester to give the complex target ester in high yields.

[...] “Being both recyclable and free of metals, this catalyst is a genuine example of green chemistry,” says lead author Kazuaki Ishihara. “Not only is the process itself green, but we can use it to produce green biodiesel, which is a mixture of esters. We synthesized hundreds of grams of a major biodiesel component, which is quite copious for a laboratory-scale reaction. This gives us confidence that the reaction can be scaled up to industrial production.”

Original Submission