Heterocycles by cascade reactions of versatile thioureido-acetamides

Thioureido-acetamides () are quantitatively accessible by gas–solid reaction of amines with thiohydantoins. They are useful starting materials for various heterocyclic syntheses in one-pot cascade reactions with excellent atom economy: 2-iminothiazoles () are quantitatively formed from and phenacyl bromide in the solid state. Thioparabanic acids () are easily accessible from oxalyl dichloride and . Benzils react with to afford functionalized 5,5-diaryl-thiohydantoins () and dimethylacetylene dicarboxylate gives 2-imino-5-methylene-thiazolidine-4-ones () and () upon reaction with . The one-pot syntheses of imidazo[1,2-c]pyrimidines () and () from with benzaldehydes and ethyl cyanoacetate or malodinitrile are benign new accesses to these important heterocycles. All product structures are determined from spectroscopic and chemical data and preferred tautomers are judged by DFT calculations at the B3LYP/6-31G∗ level.