Halogen-Mediated Cascade Cyclization Reaction of Aryldiynes to Indeno[1,2-c]chromene Derivatives.

The halogen-mediated cyclization reaction of aryldiynes to produce halogenated indeno[1,2-c]chromene derivatives is described. Treatment of aryldiynes 1 with one equivalent of iodine gave iodinated indeno[1,2-c]chromenes 3 in good chemical yields. When two equivalents of iodine were employed into the reaction mixture, dimer 9 was obtained as the major products. On the other hand, reaction of two equivalents of CuBr2 with compounds 1 gave the brominated indeno[1,2-c]chromenes 4. The DFT calculation of the iodine-mediated cyclization reactions for molecules containing methoxy, carboxy, amino, and sulfide substituents were carried out in order to understand how the substituent affects the cyclization pathway.