Yang Zhanhui, Chen Ning, Xu Jiaxi
State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China.
J Org Chem. 2015 Apr 3;80(7):3611-20. doi: 10.1021/acs.joc.5b00312. Epub 2015 Mar 25.
In the sulfa-Staudinger cycloadditions of imines and sulfonyl chlorides, the annuloselectivity is mainly controlled by the electronic effect of the α-substituents of sulfonyl chlorides and the nucleophilicity of imines. Sulfonyl chlorides with weakly electron-donating and withdrawing substituents prefer the [2(s)+2(i)] annulation, giving a mixture of cis- and trans-β-sultams. Sulfonyl chlorides bearing strongly electron-withdrawing α-substituents show different annuloselectivity depending upon the nucleophilicity of imines as following: (1) weakly nucleophilic imines with sterically larger substituents than the methyl group undergo only [2(s)+2(i)] annulation to produce trans-β-sultams; (2) strongly nucleophilic imines with the N-methyl substituent take place both [2(s)+2(i)] and [2(s)+2(i)+2(i)] annulations generally, delivering trans-β-sultams and rel(3S,5S,6R)-1,2,4-thiadiazinane 1,1-dioxides composed of one molecule of the sulfenes and two molecules of imines; (3) more strongly nucleophilic cyclic (Z)-imines give predominately [2(s)+2(i)+2(i)] annulations, resulting in a pair of diastereomeric [2(s)+2(i)+2(i)] annuladducts 1,2,4-thiadiazinane 1,1-dioxides. In the second case, the electronic and steric effects of the C-substituents of the N-methyl imines also affect the annuloselectivity. The stereochemistry and stereoselectivities of the [2(s)+2(i)] and [2(s)+2(i)+2(i)] annuladducts were investigated systematically and mechanistically rationalized.
在亚胺与磺酰氯的硫代 - 施陶丁格环加成反应中，环化选择性主要受磺酰氯α - 取代基的电子效应和亚胺的亲核性控制。具有弱供电子和吸电子取代基的磺酰氯倾向于[2(s)+2(i)]环化，生成顺式和反式β - 磺内酰胺的混合物。带有强吸电子α - 取代基的磺酰氯根据亚胺的亲核性表现出不同的环化选择性，具体如下：(1) 具有比甲基空间位阻更大取代基的弱亲核亚胺仅发生[2(s)+2(i)]环化以生成反式β - 磺内酰胺；(2) 具有N - 甲基取代基的强亲核亚胺通常同时发生[2(s)+2(i)]和[2(s)+2(i)+2(i)]环化，生成反式β - 磺内酰胺和由一分子亚磺烯和两分子亚胺组成的rel(3S,5S,6R)-1,2,4 - 噻二嗪烷1,1 - 二氧化物；(3) 亲核性更强的环状(Z)-亚胺主要发生[2(s)+2(i)+2(i)]环化，生成一对非对映异构的[2(s)+2(i)+2(i)]环化加合物1,2,4 - 噻二嗪烷1,1 - 二氧化物。在第二种情况下，N - 甲基亚胺的C - 取代基的电子效应和空间效应也影响环化选择性。对[2(s)+2(i)]和[2(s)+2(i)+2(i)]环化加合物的立体化学和立体选择性进行了系统研究并从机理上进行了合理化解释。
