Nucleophilic substitution approach towards 1,3-dimethylbarbituric acid derivatives—new synthetic routes and crystal structures

We describe simple, convenient and high-yielding nucleophilic substitution reactions to synthesize new derivatives of 1,3-dimethylbarbituric acid (1a). Based on its active C5 position, condensing 1a with sulfuryl chloride gives the corresponding 5,5-dichloro-1,3-dimethylbarbituric acid (13). The latter was reacted with silver nitrite and potassium cyanide to afford 5-chloro-5-nitro-1,3-dimethylbarbituric acid (14) and 5-cyano-1,3-dimethylbarbiturate (17), respectively. Furthermore, by employing the nucleophilic character of 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (8) the obtained compounds 13 and 14 have been converted to 2-chloro-1,3-diisopropyl-4,5-dimethyl-1H-imidazol-3-ium-1,3-dimethyl-5-nitro-1,3-dimethylbarbiturate (18) and 1,3-dimethylbarbituric acid trimer (21), respectively. X-ray structures for compounds 13, 14, 17, 18 and 21 were determined.