The Effect of Pressure on the Cycloadditions of Cyanoacetylene to Furan Derivatives – [2.2](2,5)Furanoparacyclophane, [8](2,5)Furanophane, and Furan
作者:Volker Breitkopf、Peter Bubenitschek、Henning Hopf、Peter G. Jones、Frank-Gerrit Klärner、Dietmar Schomburg、Bernhard Witulski、Bernd Zimny
DOI:10.1002/jlac.199719970119
日期:1997.1
(2:1) adducts 20, 23, and 13 are probably formed by a sequence of Diels-Alder and [2 + 2] cycloadditions rather than by the reverse sequence starting with [2 + 2] cyclodimerization of 1 followed by Diels-Alder reaction with cyclobutadiene 2a as postulated by the analogy to the trimerization of 1 and the cycloaddition of 1 to paracyclophane. The high-pressure experiments led us to propose a new mechanism
在1 bar和160°C下,氰基乙炔(1)与[2.2](2,5)呋喃对环环烷(3)的反应产生了出乎意料的“环扩大”的酮6-11。在反应1与[8](2,5)furanophane(4)的可比产品21和22中观察到,除产品19和20从一个连续的Diels-Alder加成预期,阿尔德-李凯尔特裂解过程和将Diels-Alder将1,4-二氰基-1,3-环丁二烯(2a)分别添加到4中。在1与母呋喃5的反应中只有(2:1)和(1:2)狄尔斯-阿尔德加合物23,25,26,和27被发现了。通过(1:2)Diels-Alder的流热分解独立制备的2-氰基-7-氧杂双环-[2.2.1]庚2,5-二烯(24)的高压实验和反应性加合物26和27,提供的证据表明,(2:1)加合物20,23,和13可能是由狄尔斯-阿德耳的序列,并且形成[2 + 2]环加成而不是通过反向序列开始与[2 + 2 ]的环二聚1,随后用