Synthesis, Structure, and Complexation of an S‐Shaped Double Azahelicene with Inner‐Edge Nitrogen Atoms
Takahiro Kawashima, Yuki Matsumoto, Takuma Sato, Yoichi M. A. Yamada, Choji Kono, Akihiro Tsurusaki, Ken Kamikawa
Abstract
Abstract An S‐shaped double azahelicene ( 1 ) was synthesized in excellent yield by a palladium‐catalyzed double dehydrogenative C−H coupling reaction. The stereochemistry of 1 was confirmed to be dl by single‐crystal X‐ray diffraction analysis. Selective formation of dl‐ 1 was attributed to the isomerization of the kinetically controlled product ( meso ‐ 1 ) into the more thermodynamically stable dl‐ 1 under the applied reaction conditions. dl‐ 1 can coordinate to palladium(II) in a bidentate trans ‐chelating fashion, which was confirmed by X‐ray absorption fine structure (XAFS) as well as by X‐ray photoelectron spectroscopy (XPS), diffuse reflectance (DR) UV/Vis, and far‐infrared (FIR) absorption spectroscopy. Theoretical calculations of palladium complex 16 revealed a weak attractive interaction between palladium and carbon atoms on the central dimethoxynaphthalene core, which could facilitate a disproportionation between a trans ‐chelating ( dl‐ 1 ) ⋅ PdCl 2 complex and PdCl 2 to form 16 .