Frontier-controlled cycloaddition reactions of cyclopentadienones having electron-donating or -attracting substituents: configuration of adducts and kinetic studies
作者:Masato Mori、Ayako Hayamizu、Ken Kanematsu
DOI:10.1039/p19810001259
日期:——
inverse electron demand. By contrast, in the correlation for the cycloaddition of (1b) with (2a–h), two lines with markedly different slopes were observed, which can be ascribed to a Diels–Alder reaction with neutral electron demand. The initial cycloadditions of (1a) and (1b) with tropone (29) gave the [4 + 6]π adducts (32a,b). Subsequently the adduct (32b) underwent oxy-Cope rearrangement to (35). The
2,5-二甲氧基羰基-和2,5-二乙基-3,4-二苯基环戊二烯酮[CPC(1a)和EPC(1b)]与对位取代的苯乙烯(2a–h)的环加成反应产生的主要加合物的立体化学证实降冰片二烯(7),降冰片烯(8),1,4-二氢-1,4-环氧萘(9),马来酸酐(10)和N-苯基马来酰亚胺(11)具有内构型。为了定义取代基对Diels-Alder反应速率的影响,对(1a,b)与一系列苯乙烯(2a-h)的反应性进行了动力学研究。(1a)与(2a–h)的环加成的对数k / k H值与冈本布朗的σp +相关常数和ρ值为–0.941。该结果表明,环加成反应被归类为具有反电子需求的Diels-Alder反应。相比之下,在(1b)与(2a–h)的环加成反应的相关性中,观察到两条斜率明显不同的线,这可以归因于具有中性电子需求的Diels–Alder反应。(1a)和(1b)与对苯二酚(29)的初始环加成反应产生[4 +