| 词条 | Zinc–copper couple |
| 释义 |
SynthesisZinc–copper couple has been prepared by numerous methods, which vary mainly with respect to the source of copper, but also by the ratio of copper to zinc, the physical state of the zinc (e.g. powder or granules), the use of protic acids and other additives, and temperature of the preparation. Most often the couple is generated and isolated prior to use, but routes have been described to storable forms of the alloy. Most methods involve reduction of an oxidized copper species with zinc, which is used in excess. An early method for the synthesis of zinc–copper couple entailed treatment of a mixture of zinc dust and copper(II) oxide with hydrogen gas at 500 °C.[1] A more convenient and cheaper method proceeds by treatment of zinc powder with hydrochloric acid and copper(II) sulfate.[3] Treatment of zinc powder with copper(II) acetate monohydrate in hot acetic acid is reportedly highly reproducible.[4] The couple may also be generated in situ by reaction of one equivalent of zinc dust with one equivalent of copper(I) chloride (or copper powder) in refluxing ether.[5] The choice of method is dictated primarily by the application. The development of newer methods was motivated by the need for zinc–copper couple with reproducible behavior. ApplicationZinc–copper couple has found widespread use in organic synthesis, especially in the Simmons–Smith cyclopropanation of alkenes. In this process, the couple (typically a slurry in an ethereal solvent) reacts with methylene iodide to generate iodomethylzinc iodide, which is the intermediate responsible for cyclopropanation.
The couple has also been employed to generate alkyl zinc reagents for conjugate addition, as a dehalogenating reagent, as a promoter of reductive coupling of carbonyl compounds, and to reduce electron-deficient alkenes and alkynes. Sonication has been employed to enhance the rate of the zinc–copper couple-mediated cycloaddition of α,α’-dibromo ketones to 1,3-dienes.[6] References1. ^1 {{cite journal | title = A New Synthesis of Cyclopropanes | author = Howard H. Simmons, Ronald D. Smith | journal = J. Am. Chem. Soc. | year = 1959 | volume = 81 | issue = 16 | pages = 4256–4264 | doi = 10.1021/ja01525a036}} {{DEFAULTSORT:Zinc-copper couple}}2. ^{{cite book | author = Scott D. Rychnovsky, Jay P. Powers | title = Encyclopedia of Reagents for Organic Synthesis | year = 2001 | doi = 10.1002/047084289X.rz011 | chapter = Zinc/Copper Couple | isbn = 0-471-93623-5}} 3. ^{{OrgSynth| title = Norcarane | author = Howard H. Simmons, Ronald D. Smith | year = 1973 | collvol = 5 | collvolpages = 855 | prep = cv5p0855}} 4. ^{{cite journal | title = Cyclopropanes from an Easily Prepared, Highly Active Zinc-Copper Couple, Dibromomethane, and Olefins | author = Eugene LeGoff | journal = J. Org. Chem. | year = 1964 | volume = 29 | pages = 2048 | doi = 10.1021/jo01030a529 | issue = 7}} 5. ^{{cite journal | title = A Convenient Procedure for the Methylenation of Olefins to Cyclopropanes | author = Robert J. Rawson, Ian T. Harrison | journal = J. Org. Chem. | year = 1970 | volume = 35 | issue = 6 | pages = 2057–2058 | doi = 10.1021/jo00831a091}} 6. ^{{cite journal | title = Ultrasonics in the Metal Promoted Cycloaddition of α,α’-dibromo ketones to 1,3-dienes | author = Navalkishore N. Joshi, H. Martin R. Hoffmann | journal = Tetrahedron Letters | year = 1986 | volume = 27 | issue = 6 | pages = 687–690 | doi = 10.1016/S0040-4039(00)84073-3}} 2 : Zinc alloys|Reducing agents |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。