Polymer-supported ionic-liquid-catalyzed synthesis of 1,2,3,4-tetrahydro-2-oxopyrimidine-5-carboxylates via biginelli reaction

The Biginelli reaction between an aromatic alclehyde, ethyl acetoacetate, and urea - catalyzed by polymer-supported, re-usable, room-temperature ionic liquids (RTIL) such as 1b - was shown to efficiently proceed in glacial AcOH at 100 degrees to afford the corresponding pyrimidine-5-carboxylates 3 in yields up to 99% within 2 h (Table 2). The catalyst(s) could be reused at least five times, basically without loss of activity, which makes this transformation not only straight-forward, but also considerably less expensive compared to methods involving classical RTIL catalysts.