Push-Pull Buta-1,2,3-trienes: Exceptionally Low Rotational Barriers of Cumulenic CC Bonds and Proacetylenic Reactivity
作者:Przemyslaw Gawel、Yi-Lin Wu、Aaron D. Finke、Nils Trapp、Michal Zalibera、Corinne Boudon、Jean-Paul Gisselbrecht、W. Bernd Schweizer、Georg Gescheidt、François Diederich
DOI:10.1002/chem.201406583
日期:2015.4.13
[3]cumulenes (buta‐1,2,3‐trienes) were synthesized by developed procedures. The activation barriers to rotation ΔG≠ were measured by variable temperature NMR spectroscopy and found to be as low as 11.8 kcal mol−1, in the range of the barriers for rotation around sterically hindered single bonds. The central CC bond of the push–pull‐substituted [3]cumulene moiety is shortened down to 1.22 Å as measured
通过开发的方法合成了多种不对称的供体-受体取代的[3]枯烯(丁二烯,1,2,3-三烯)。旋转的激活壁垒ΔG ≠通过可变温度NMR光谱法测量,发现低至11.8 kcal mol -1在围绕位阻单键旋转的障碍范围内。通过X射线晶体学测定,推挽取代的[3]异丙苯部分的中央CC键缩短到1.22Å,导致键长交替(BLA)高达0.17Å。DFT计算支持所有实验结果。键旋转的两性离子跃迁状态(TS)证实了供体-受体[3] cumulenes的假定的炔炔原特性。这些生色团的原炔性质的额外支持是通过它们与供体极化的乙炔的环加成-逆电环化(CA-RE)级联反应中的四氰基乙烯(TCNE)反应提供的。