Chloranil as an Efficient Oxidant of the Cyclohexadiene Intermediates Formed by a Cycloaddition of Substituted 2H‐Pyran‐2‐ones and Styrenes En Route to the Boscalid Derivatives

We describe a three-step one-pot metal-free domino procedure yielding a set of boscalid derivatives, parent compound being a highly important agrochemical agent. The first step of the process consists of the Diels–Alder reaction between a substituted 2H-pyran-2-one and styrene derivatives, followed by the elimination of CO2 and aromatization (oxidation). The last step was found to be efficiently promoted by the application of chloranil as the oxidant. Alternatively, activated carbon Darco KB could also act as the dehydrogenation catalyst necessitating a larger excess of the styrene to act as the hydrogen acceptor.