Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany.
J Am Chem Soc. 2011 Jun 1;133(21):8240-51. doi: 10.1021/ja200820m. Epub 2011 May 5.
The rates of the epoxidation reactions of aldehydes, of the aziridination reactions of aldimines, and of the cyclopropanation reactions of α,β-unsaturated ketones with aryl-stabilized dimethylsulfonium ylides have been determined photometrically in dimethyl sulfoxide (DMSO). All of these sulfur ylide-mediated cyclization reactions as well as the addition reactions of stabilized carbanions to N-tosyl-activated aldimines have been shown to follow a second-order rate law, where the rate constants reflect the (initial) CC bond formation between nucleophile and electrophile. The derived second-order rate constants (log k(2)) have been combined with the known nucleophilicity parameters (N, s(N)) of the aryl-stabilized sulfur ylides 4a,b and of the acceptor-substituted carbanions 4c-h to calculate the electrophilicity parameters E of aromatic and aliphatic aldehydes (1a-i), N-acceptor-substituted aromatic aldimines (2a-e), and α,β-unsaturated ketones (3a-f) according to the linear free-energy relationship log k(2) = s(N)(N + E) as defined in J. Am. Chem. Soc.2001, 123, 9500-9512. The data reported in this work provide the first quantitative comparison of the electrophilic reactivities of aldehydes, imines, and simple Michael acceptors in DMSO with carbocations and cationic metal-π complexes within our comprehensive electrophilicity scale.
醛的环氧化反应、亚胺的氮丙啶化反应以及α,β-不饱和酮与芳基稳定的二甲亚砜叶立德的环丙烷化反应的速率已在二甲基亚砜 (DMSO) 中通过光度法确定。所有这些硫叶立德介导的环化反应以及稳定的碳负离子与 N-对甲苯磺酰基活化亚胺的加成反应均遵循二级反应定律，其中速率常数反映了亲核体与亲电体之间的（初始）CC 键形成。推导的二级速率常数 (log k(2)) 已与芳基稳定的硫叶立德 4a,b 和受电子取代的碳负离子 4c-h 的已知亲核性参数 (N, s(N)) 结合，以根据 J. Am. Chem. Soc.2001, 123, 9500-9512 中定义的线性自由能关系 log k(2) = s(N)(N + E) 计算芳香族和脂肪族醛 (1a-i)、N-受电子取代的芳基亚胺 (2a-e) 和α,β-不饱和酮 (3a-f) 的亲电性参数 E。本工作中报道的数据提供了在我们综合亲电性标度中首次定量比较醛、亚胺和简单迈克尔受体在 DMSO 中的亲电性与碳正离子和阳离子金属-π 配合物的亲电性。
