Safe, Selective, and High-Yielding Synthesis of Acryloyl Chloride in a Continuous-Flow System.

Acid chlorides are an important class of compounds and their high reactivity and instability has prompted us to develop a straightforward procedure for their synthesis with on-demand and on-site synthesis possibilities. The focus of this report is acryloyl chloride, mainly important for the acrylate and polymer industry. A continuous-flow methodology was developed for the fast and selective synthesis of the otherwise highly unstable acryloyl chloride. Three routes were investigated in a microreactor setup and all three can potentially be used for its production. The methodology was further expanded to the synthesis of other unstable acid chlorides by both the thionyl chloride and the oxalyl chloride mediated processes. The most sustainable method was the oxalyl chloride mediated procedure under solvent-free conditions, in which near-equimolar amounts of carboxylic acid and oxalyl chloride were used in the presence of catalytic amounts of DMF at room temperature. Within 1 to 3 min, nearly full conversions into the acid chlorides were achieved.