Facile Photochemical Synthesis of 5,10-Disubstituted [5]Helicenes by Removing Molecular Orbital Degeneracy
作者:Natsuki Ito、Takashi Hirose、Kenji Matsuda
DOI:10.1021/ol5008718
日期:2014.5.2
Photocyclodehydrogenation is a key reaction to synthesize helicenes; however, because of overannulation, it is not applicable to the synthesis of [S]helicene. Introduction of a cyano group was found to remove the orbital degeneracy of the low-lying unoccupied MOs; consequently, the lowest excitation comprises a single transition involving the C-2-antisymmetric MO. Therefore, the problematic overannulation can be effectively suppressed. Moreover, in combination with the Knoevenagel reaction, a one-pot synthesis of 5,10-dicyano[5]helicene with 67% yield was accomplished.
Topologically diverse polycyclic aromatic hydrocarbons from pericyclic reactions with polyaromatic phospholes
Polycyclic AromaticHydrocarbons (PAHs) with planar, twisted and negatively curved topologies were obtained from polycyclic phospholes using pericyclic reactions. Deviation from planarity is due to steric interactions between the PAH core and the ester substituents. These structural effects on the optical and redox properties were studied and rationalized through DFT calculations. This synthetic approach