Abstract
Abstract The ternary condensation of N-methoxyurea, aldehydes, and 1,3-dicarbonyl compounds, resulting in novel 1-methoxy-3,4-dihydropyrimidin-2(1H)-ones has been examined. Commonly used reaction conditions and catalysts (EtOH/HCl, HOAc, DMF) proved to be unsuitable and we found that the DMF–TMSCl system was the best catalyst. Similarly, the reaction of ureas with 4-chlorobenzaldehyde and 1,3-cyclohexanedione using the DMF/TMSCl system afforded 3,4,7,8-tetrahydroquinazolin-2,5(1H,6H)-diones, while other catalyst systems resulted in the formation of product mixtures. In addition, we have developed an effective and simple protocol for the synthesis of N-(methoxy)urea.
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