Synthesis of novel 5-monoalkylbarbiturate derivatives: new access to 1,2-oxazepines

A simple and straightforward route to 5-monoalkylbarbiturates by the NHEt2 catalyzed Michael reaction of 1,3-dimethylbarbituric acid and α,β-unsaturated ketones is described. Significantly, the reaction exclusively furnished 5-monoalkylbarbiturates. Under neat conditions, the mixing and grinding of a representative 1,5-diketone and hydroxylamine hydrochloride gave the corresponding 1,2-oxazepine in very good yield.