Vinyl hydrogen more reactive than benzyl hydrogen toward base in significantly twisted styrenes
摘要:
The novel example of vinyl hydrogen more reactive than benzylic hydrogen was found by treatment of a twisted styrene derivative with a strong base followed by D2O quenching. The characteristic nature of the vinyl hydrogen, which is activated by sigma-pi* orbital interaction, was apparently demonstrated. (C) 2001 Elsevier Science Ltd. All rights reserved.
Highly Activated Vinyl Hydrogen in a Significantly Twisted Styrene
摘要:
The novel example of a vinylic hydrogen more reactive than a benzylic hydrogen was found by treatment of a twisted styrene derivative with a strong base followed by D2O quenching. In this paper, the full details of the examples of the highly activated vinyl hydrogens in twisted styrene derivatives are described, with a discussion on the correlation between the reactivity of the vinyl hydrogens and the magnitude of the twist. The highly reactive vinyl hydrogens could be rationalized by considering the novel orbital interaction between the pi* orbital of the benzene ring and the sigma orbital of the vinylic C-H bond in the twisted styrene derivatives.
Multimetallic Ir–Sn3-catalyzed substitution reaction of π-activated alcohols with carbon and heteroatom nucleophiles
作者:Arnab Kumar Maity、Paresh Nath Chatterjee、Sujit Roy
DOI:10.1016/j.tet.2012.10.086
日期:2013.1
An atom economic and catalytic substitutionreaction of π-activated alcohols by a multimetallic Ir–Sn3 complex has been demonstrated. The multimetallic Ir–Sn3 complex can be easily synthesized from the reaction between [Cp∗IrCl2]2 and SnCl2. In presence of as little as 1 mol % of the catalyst three different types of π-activated alcohols, namely benzyl, allyl, and propargyl alcohols, have been successfully
Microwave-Promoted Copper-Free Sonogashira-Hagihara Couplings of Aryl Imidazolylsulfonates in Water
作者:José F. Cívicos、Diego A. Alonso、Carmen Nájera
DOI:10.1002/adsc.201200629
日期:2013.1.14
Aryl imidazol‐1‐ylsulfonates have been efficiently cross‐coupled with aryl‐, alkyl‐, and silylacetylenes in neat water under copper‐free conditions at 110 °C assisted by microwave irradiation. Using 0.5 mol% of an oxime palladacycle as precatalyst, 2‐dicyclohexylphosphino‐2′,6′‐dimethoxybiphenyl (SPhos, 2 mol%) as ligand, hexadecyltrimethylammonium bromide (CTAB) as additive, and triethylamine (TEA)
Sonogashira Coupling Using Bulky Palladium-Phenanthryl Imidazolium Carbene Catalysis
作者:Yudao Ma、Chun Song、Wei Jiang、Quansheng Wu、Yong Wang、Xueying Liu、Merritt B. Andrus
DOI:10.1021/ol035147k
日期:2003.9.1
[GRAPHICS]Bulky phenanthracenyl imidazolium-derived carbene ligands were investigated for copper-free Sonogashira coupling with terminal acetylenes. Aryl bromides and iodides gave coupled products in excellent yields from the Pd(PPh3)(2)Cl-2 complex with potassium t-butoxide and 18-crown-6 in THF. A remarkable dependence on the size of the ligand was found. The highest yields were obtained with the bulky 2,9-dicyclohexyl-10-phenanthryl ligand 5.
Palladacycle-Catalyzed Deacetonative Sonogashira Coupling of Aryl Propargyl Alcohols with Aryl Chlorides
作者:Hao Hu、Fan Yang、Yangjie Wu
DOI:10.1021/jo4014657
日期:2013.10.18
An efficient and general protocol for the deacetonative Sonogashira coupling of aryl propargyl alcohols with aryl chlorides is described. The reaction proceeded smoothly with the catalyst system of palladacycle/Xphos. This result represents the first successful deacetonative Sonogashira version for electron-poor, electron-neutral, and even inactive sterically hindered electron-rich aryl chlorides.