New Method for Preparation of Coumarins and Quinolinones via Pd-Catalyzed Intramolecular Hydroarylation of C−C Triple Bonds
摘要:
A new and general method has been developed for preparation of coumarins and quinolinones by intramolecular hydroarylation of alkynes. Various aryl alkynoates and alkynanilides undergo fast intramolecular reaction at room temperature in the presence of a catalytic amount of Pd(OAc)(2) in a mixed solvent containing trifluoroacetic acid (TFA), affording coumarins and quinolinones in moderate to excellent yields with more than 1000 turnover numbers (TON) to Pd. The methodology proved to tolerate a number of functional groups such as Br and CHO. On the basis of isotope experiments, a possible mechanism involving ethynyl chelation-assisted electrophilic metalation of aromatic C-H bonds by in-situ generated cationic Pd(II) species has been discussed. Also the involvement of vinylcationic species has been suggested.
Copper/Selectfluor-System-Catalyzed Dehydration-Oxidation of Tertiary Cycloalcohols: Access to β-Substituted Cyclohex-2-enones, 4-Arylcoumarins, and Biaryls
作者:Shaobo Ren、Jian Zhang、Jiahui Zhang、Heng Wang、Wei Zhang、Yunkui Liu、Miaochang Liu
DOI:10.1002/ejoc.201500610
日期:2015.8
A route to β-substitutedcyclohex-2-enones, 4-arylcoumarins, and biaryls has been developed. This approach involves a one-pot Cu0/Selectfluor-catalyzed dehydration–oxidation of tertiary cycloalcohols. Thus, by using 2 equiv. of Selectfluor at 25 °C, the dehydration–oxidation of tertiary cyclohexanols and oxabenzocyclohexanols gave β-substitutedcyclohex-2-enones and 4-arylcoumarins, respectively; whereas
Metal-free annulative hydrosulfonation of propiolate esters: synthesis of 4-sulfonates of coumarins and butenolides
作者:Rodney A. Fernandes、Ashvin J. Gangani、Rupesh A. Kunkalkar
DOI:10.1039/c9nj06438a
日期:——
An efficient metal-free and cost-effective method for the synthesis of coumarin and butenolide 4-sulfonates has been developed involving addition of sulfonic acids to ethyl propiolates followed by lactonization.
Straightforward Entry toward Highly Substituted 2,3-Dihydrobenz[<i>b</i>]oxepines by Ring Expansion of Benzopyryliums with Donor–Acceptor Diazo Compounds
作者:Thibaut Courant、Morgane Pasco、Thomas Lecourt
DOI:10.1021/acs.orglett.8b00984
日期:2018.5.4
Ylide-type reactivity of diazo compounds is exploited in a new way to prepare benzo[b]oxepines thanks to the formation of three chemical bonds and two contiguous and highly substituted stereocenters in a single pot. This cationic reaction cascade first involves addition of a donor–acceptor-substituted diazo compound to a benzopyrylium. Selective 1,2 migration of the endocyclic C–C bond then results
由于在单个罐中形成了三个化学键和两个连续且高度取代的立体中心,重氮化合物的Ylide型反应性被以一种新的方式用于制备苯并[ b ]氧杂环丁烷。这种阳离子反应级联首先涉及将供体-受体取代的重氮化合物添加到苯并吡啶中。内环C–C键的选择性1,2迁移随后导致环扩展并生成第二个氧碳鎓,该碳鎓被依次添加的亲核试剂捕获。
New Method for Preparation of Coumarins and Quinolinones via Pd-Catalyzed Intramolecular Hydroarylation of C−C Triple Bonds
A new and general method has been developed for preparation of coumarins and quinolinones by intramolecular hydroarylation of alkynes. Various aryl alkynoates and alkynanilides undergo fast intramolecular reaction at room temperature in the presence of a catalytic amount of Pd(OAc)(2) in a mixed solvent containing trifluoroacetic acid (TFA), affording coumarins and quinolinones in moderate to excellent yields with more than 1000 turnover numbers (TON) to Pd. The methodology proved to tolerate a number of functional groups such as Br and CHO. On the basis of isotope experiments, a possible mechanism involving ethynyl chelation-assisted electrophilic metalation of aromatic C-H bonds by in-situ generated cationic Pd(II) species has been discussed. Also the involvement of vinylcationic species has been suggested.
Efficient Functionalization of Aromatic C−H Bonds Catalyzed by Gold(III) under Mild and Solvent-Free Conditions
作者:Zhangjie Shi、Chuan He
DOI:10.1021/jo0497353
日期:2004.5.1
A gold(III)-catalyzed carbon-carbon bond formation reaction between arenes and electron-deficient alkynes or alkenes is described. Electron-rich arenes can be efficiently functionalized with the alkyne or alkene substrates. This reaction can be run with neat reactants at ambient temperature. Under the "solventless" conditions, clean product was obtained from a reaction of equal molar amounts of arene and alkyne substrates. The mild conditions and potential tolerance to different functional groups make this method practical for arene functionalization and for constructing complicated molecules. Efficient preparation of various coumarins from aryl alkynoates was demonstrated. Preliminary mechanistic studies were performed to probe the pathway of this reaction.