A Novel One-Pot Synthesis of Fluorinated α,β-Unsaturated Esters
摘要:
The reaction of pentafluorophenylmethylene-triphenylarsorane or p-chloro-tetrafluorophenylmethyl-enetriphenylarsorane, generated in situ from methylene-triphenylarsorane and hexafluorobenzene or chloropenta-fluorobenzene, with bromoacetates giving excellent yields of 3-pentafluorophenyl or 3-p-chloro-tetrafluorophenyl alpha,beta-unsaturated esters with high steroselectivity is described.
Wittig Reactions in Water Media Employing Stabilized Ylides with Aldehydes. Synthesis of α,β-Unsaturated Esters from Mixing Aldehydes, α-Bromoesters, and Ph<sub>3</sub>P in Aqueous NaHCO<sub>3</sub>
作者:Amer El-Batta、Changchun Jiang、Wen Zhao、Robert Anness、Andrew L. Cooksy、Mikael Bergdahl
DOI:10.1021/jo070665k
日期:2007.7.1
range of stabilized ylides and aldehydes. Despite sometimes poor solubility of the reactants, good chemical yields normally ranging from 80 to 98% and high E-selectivities (up to 99%) are achieved, and the rate of the reactions in water is unexpectedly accelerated. The efficiency of water as a medium in the Wittig reaction is compared to conventional organic solvents ranging from carbon tetrachloride
Water is demonstrated to be an excellent medium for the Wittigreaction employing stabilized ylides and aldehydes. Although the solubility in water appears to be an unimportant characteristic in achieving good chemical yields and E/Z-ratios, the rate of Wittigreactions in water is unexpectedly accelerated.
proton transport capacity of the resulting membrane, (iii) both aliphatic and aromatic perfluorinated tags to diversify the membrane polarity with respect to Nafion®, and (iv) a double bond to facilitate the polymerization under vacuum giving a preferential way for the chain growth of the polymer. A retrosynthetic approach persuaded us to attempt three main synthetic strategies: (a) organometallic Heck-type
Palladium-Based System for the Polymerization of Acrylates. Scope and Mechanism
作者:Christine Elia、Sharon Elyashiv-Barad、Ayusman Sen、Raquel López-Fernández、Ana C. Albéniz、Pablo Espinet
DOI:10.1021/om020435q
日期:2002.9.1
found to effect the polymerization of acrylates upon addition of 1 equiv of a monodentate phosphine or pyridine or an excess of halide. Methyl methacrylate was not polymerized, and furthermore, its addition stopped the progress of independently initiated methyl acrylatepolymerization in the phosphine-based system. Addition of ethene also inhibited the polymerization of methyl acrylate. However, over 10
发现中性钯络合物[Pd(C 6 F 5)Br(NCMe)2 ](1)通过添加1当量的单齿膦或吡啶或过量的卤化物来实现丙烯酸酯的聚合。甲基丙烯酸甲酯未聚合,此外,其添加停止了基于膦的体系中独立引发的丙烯酸甲酯聚合的进程。乙烯的添加也抑制了丙烯酸甲酯的聚合。但是,当将1-己烯与丙烯酸甲酯一起加入时,聚合物中1-己烯的掺入量超过10mol%。讨论了聚合机理。
Pd-Catalyzed Sequential C–C Bond Formation and Cleavage: Evidence for an Unexpected Generation of Arylpalladium(II) Species
作者:So Won Youn、Byung Seok Kim、Arun R. Jagdale
DOI:10.1021/ja304616q
日期:2012.7.18
A Pd(II)-catalyzed reaction engaging alkenyl beta-keto esters is reported that leads to the formation of 1-naphthols and an unexpected generation of arylpalladium-(II) species. Interception of the in situ generated arylpalladium(II) species in a Mizoroki-Heck reaction, together with additional mechanistic studies, provided strong evidence in support of the first aromatization-driven beta-carbon elimination process. A single Pd catalyst served to promote a series of both C-C bond forming and cleavage events in an unprecedented manner.