Vinylogous Aza‐Michael Addition of Urea Derivatives with p‐Quinone Methides Followed by Oxidative Dearomative Cyclization: Approach to Spiroimidazolidinone Derivatives

Abstract Herein, we report an efficient protocol for the synthesis of spiro‐imidazolidinone‐cyclohexadienones from p ‐quinone methides ( p ‐QMs) and dialkyloxy ureas under mild conditions. The strategy follows a two‐step process involving an initial vinylogous conjugate addition of urea derivatives to p ‐QMs, followed by oxidative dearomative cyclization of open‐chain product to the projected spiro‐imidazolidinones. This protocol exhibits good functional group tolerance and provides a straightforward method to access spiro‐imidazolidinone‐cyclohexadienones. In follow‐up chemistry, we have shown the debenzylation of spiroimidazolidinones to give N ‐hydroxycyclic ureas. magnified image