Ring-Enlargement of in Situ Generated Cyclopropanones by the Reaction with Sulfonium Ylides: One-Pot Synthesis of Cyclobutanones

In this report, we describe a simple method for the synthesis of 2-aryl-2-vinyl-cyclobutanones through the reaction of in situ generated cyclopropanones and cinnamylsulfonium ylides, representing an example of a formal carbene insertion into these three-membered rings. The cyclobutanones thus obtained are ideal substrates for palladium-catalyzed coupling reactions upon enol triflate formation, thereby providing access to densely functionalized cyclobutenes. A mechanistic proposal for the ring-enlargement is presented based on experimental evidence.