Cycloaddition reactions of 1,3-diphenylthiazolo(3,4-a)benzimidazole with fulvene and tropone systems.
1,3-Diphenylthiazolo[3,4-a]benzimidazole (1) containing tetravalent sulfur reacts as a thiocarbonyl ylide dipole with 6,6-diphenylfulvene to give a mixture of two regioisomeric exo-[4 + 2] adducts and endo-[4 + 2] adduct. The reaction of 1 with tropone and 8,8-dicyanoheptafulvene proceeds via a [4 + 2] cycloaddition to the C4–C5and C1–C2 bond of the addend to afford the exo-adduct and desulfurized compound respectively.