Donor- and/or Acceptor-Substituted Expanded Radialenes: Theory, Synthesis, and Properties

The synthesis of donor- (D) and/or
acceptor (A)-expanded [4]­radialenes
has been developed on the basis of readily available dibromoolefin
(7), tetraethynylethene (10 and 20), and vinyl triflate (12) building blocks. The successful
formation of D/A radialenes relies especially on (1) effective use
of a series alkynyl protecting groups, (2) Sonogashira cross-coupling
reactions, and (3) the development of ring closing reactions to form
the desired macrocyclic products. The expanded [4]­radialene products
have been investigated by spectroscopic (UV–vis absorption
and emission) and quantum chemical computational methods (density
functional theory and time dependent DFT). The combined use of theory
and experiment provides a basis to evaluate the extent of D/A interactions
via the cross-conjugated radialene framework as well as an interpretation
of the origin of D/A interactions at an orbital level.

本研究以易得的二溴烯烃(dibromoolefin)(7)、四乙炔基乙烯(tetraethynylethene)(10和20)以及三氟甲磺酸乙烯酯(vinyl triflate)(12)为构筑模块，开发了给体(D)和/或受体(A)取代的扩环[4]径向烯的合成方法。D/A型径向烯的成功合成尤其依赖于以下三点：(1) 一系列炔基保护基团的高效应用；(2) Sonogashira交叉偶联反应；(3) 用于制备目标大环产物的关环反应开发。现已通过光谱学方法（紫外-可见吸收与发射光谱）以及量子化学计算方法（密度泛函理论(density functional theory)与时域密度泛函理论(time-dependent DFT)）对扩环[4]径向烯产物进行了表征研究。理论与实验相结合的研究手段，为评估通过交叉共轭径向烯骨架实现的D/A相互作用程度提供了依据，同时也可从轨道层面阐释D/A相互作用的起源。