在甲醇中,顺式和反式-β-氯-4-硝基苯乙烯与苯硫醇盐和甲醇离子的反应显示出乙烯基反应性的通常特征:即,只有在顺式异构体与甲醇离子的反应中,消除反应才能与直接竞争代换。特别注意消除机理的研究,也对未取代的顺式-β-氯-和-β-溴-苯乙烯进行了研究。存在主要同位素效应(K H / K D = 1·6–3)且不存在任何H / D交换证明消除作用遵循E具有大碳负离子特征的2类机制。
Photochemical halogen-bonding assisted generation of vinyl and sulfur-centered radicals: stereoselective catalyst-free C(sp<sup>2</sup>)–S bond forming reactions
作者:Helena F. Piedra、Manuel Plaza
DOI:10.1039/d2sc05556b
日期:——
formation of highly reactive vinyl radicals would be a feasible process for the photochemical cross-coupling between thiols and alkenyl halides under basic conditions. The reaction shows indeed a very broad functional group tolerance, is stereoselective, simple and scalable. In-depth mechanistic studies point at the formation of vinyl and sulfur-centered radicals as the intermediates of the reaction and
Stereoselective Heck Reactions with Vinyl Sulfoxides, Sulfides and Sulfones
作者:Daniel G. Bachmann、Christopher C. Wittwer、Dennis G. Gillingham
DOI:10.1002/adsc.201300678
日期:2013.12.16
AbstractWe report the Heck cross‐coupling of notoriously unreactive, but synthetically valuable olefins: vinyl sulfoxides, vinyl sulfones, and vinyl sulfides. Key findings include the importance of the sterically hindered (tri‐tert‐butyl)phosphine ligand and the unique effectiveness of triethylamine as the base. The method is general, E‐selective, and can be used to synthesize disubstituted or trisubstituted olefins through simple adjustments of stoichiometry.magnified image
Mechanisms of Elimination Reactions. XII. The Reaction of cis- and trans-p-Nitro-β-bromostyrene with Ethanolic Alkali<sup>1,2</sup>
作者:Stanley J. Cristol、Arthur Begoon、William P. Norris、Patricia S. Ramey