Intermolecular hydrogen transfers in 2,3-dihydroimidazol-2-ylidene and 2,3-dihydrothiazol-2-ylidene: a theoretical study

The remarkable stability of N-heterocyclic carbenes has been an area of great interest in chemistry. However, prototype carbenes of these molecules, i.e. those with hydrogen atoms bearing on the nitrogens, have not been isolated as stable compounds. It is clear from our theoretical study that these prototype carbenes (2,3-dihydroimidazol-2-ylidene and 2,3-dihydrothiazol-2-ylidene) should undergo intermolecular hydrogen transfers (forming imidazole and thiazole) easily at room temperature.