Sustainable Twist – Towards Highly Atom Efficient Grignard Processes

Copper salts, which are widely applied in chemical processes, are highly toxic for aquatic life with devastating and long-lasting effects. The most sustainable measure to prevent negative impact on surface water bodies is the elimination of copper from chemical processes. In Grignard reactions, acyl chlorides are widely used in combination with copper(I) chloride to introduce acyl substituents to aromatic compounds. We demonstrate that carboxylic acid anhydrides are a competent and highly selective alternative to acyl chlorides when used in the absence of copper(I) catalysts. An integrated value stream cycle allows for recycling of the carboxylate salt byproducts by reaction with ketene, thereby reducing the waste output to almost zero. This proposed process can therefore contribute to minimizing both chemical waste and heavy metal input into water bodies.