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

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.

Automated summary

An efficient protocol for the synthesis of spiro-imidazolidinone-cyclohexadienones from p-quinone methides and dialkyloxy ureas is reported, showing good functional group tolerance and providing a straightforward method for accessing the desired compounds. Additionally, the debenzylation of spiroimidazolidinones to give N-hydroxycyclic ureas has been demonstrated in follow-up chemistry.