title: Synthesis, Structure, and Chiroptical Properties of a Double [7]Heterohelicene.
abstract: The synthesis of 11a,25a-dibora-11,12,25,26-tetraoxatetranaphtho[1,2-a:2',1'-f:1″,2″-j:2‴,1‴-o]perylene, a double [7]heterohelicene containing OBO units, has been achieved via tandem demethylation-borylation, representing the highest double helicene reported thus far with all six-membered rings. Single-crystal X-ray analysis clearly demonstrated a significantly twisted structure with the terminal aromatic rings overlapping at both ends, giving the first example of a double helicene with intramolecular π-layers. Such structural features resulted in a high theoretical isomerization barrier of 45.1 kcal/mol, which is the highest value for all the double helicenes ever reported, rendering the achieved molecule with high chiral stability. The (P,P)- and (M,M)-isomers were separated by chiral HPLC and the chiroptical properties were investigated, revealing opposite circular dichroism responses.
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Xiao-Ye
authors.initials: XY
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Chemical Engineering, Xiamen University , 361005 Xiamen, China.
authors.forename: Xin-Chang
authors.initials: XC
authors.lastname: Wang
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Narita
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Manfred
authors.initials: M
authors.lastname: Wagner
authors.affiliation: Department of Chemistry and Chemical Engineering, Xiamen University , 361005 Xiamen, China.
authors.forename: Xiao-Yu
authors.initials: XY
authors.lastname: Cao
authors.affiliation: Center for Advancing Electronics Dresden, Department of Chemistry and Food Chemistry, Technische Universität Dresden , 01062 Dresden, Germany.
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen