Safety Assessment of Diels–Alder Reactions with Highly Reactive Acrylic Monomers

The Diels–Alder reactions of the diene (cyclohexa-1,5-dien-1-yloxy)trimethylsilane with either of the two dienophiles α-acetoxyacrylonitrile or α-chloroacrylonitrile pose severe safety hazards for scale-up. We report the systematic thermal hazard assessment of these Diels–Alder reactions and discuss their classification according to the Stoessel criticality diagram. Whereas the use of α-acetoxyacrylonitrile is not recommended, the reaction of the diene with α-chloroacrylonitrile can be scaled up when running the reaction in toluene in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sodium bicarbonate.