Heterocyclic analogs of pleiadiene
In most cases 2-R-2,3-dihydroperimidines are smoothly dehydrogenated by sulfur in refluxing xylene to give 2-substituted perimidines in high yields. 2-(5-Halo-2-furyl)-2,3-dihydroperimidines, which form IV and 2-(5-halo-2-furyl)perimidines when they are heated with sulfur, constitute an exception.