Mi Chen

A convenient solution and solid-phase synthesis of Δ5-2-oxopiperazines via N-acyliminium ions cyclization

An extremely efficient synthesis of Δ5-2-oxopiperazines in solution phase and on solid support has been established via a Ugi four-component condensation reaction (U-4CC) followed by N-acyliminium ion cyclization between the aldehyde (acetal) functionality and the newly formed amide bond. The desired Δ5-2-oxopiperazines are obtained in excellent yields and purity.

A traceless solid-phase synthesis of 2-imidazolones

A traceless solid-phase synthesis of 2-imidazolones has been developed. Polymer-bound glycerol resin was reacted with bromoacetaldehyde diethyl acetal to give the cyclic acetal bromide on the solid support. Amination of the resin-bound acetal bromide followed by urea formation by reaction with isocyanates afforded the resin-bound urea acetals. The aldehyde urea intermediate, which was released from the resin upon treatment with TFA, immediately cyclized to afford the desired 2-imidazolones in good yield and purity.