| 词条 | Kauffmann olefination |
| 释义 |
The Kauffmann olefination is a chemical reaction to convert aldehydes and ketones to olefins with a terminal methylene group. This reaction was discovered by the German chemist Thomas Kauffmann and is related to the better known Tebbe olefination or Wittig reaction. Formation of the reagentThe reagent was generated in situ by conversion of different halogenides of molybdenum or tungsten with methyllithium at low temperatures (−78 °C).[1][2][3][4] During the warm-up process the formation of the active reagent occurs. nmr-experiments has shown that the active reagent is not a Schrock carbene (e.g. Tebbe-reagent). MechanismMechanism experiments shows that the olefination process is a sequence of cycloaddition and cycloelimination steps. ApplicationsFor a long time this reaction had no applications in the synthetic organic chemistry. In 2002 it was used in a total synthesis of the terpene gleenol as a mild and non-basic reagent.[5] An one-pot-protocol with an olefin metathesis step with Grubbs catalyst is also available.[6] It is remarkable that the organometallic catalyst tolerates the inorganic reaction products. References1. ^{{cite journal|author1=T. Kauffmann |author2=M. Papenberg |author3=R. Wieschollek |author4=J. Sander |journal=Chem. Ber.|year=1992|volume=125|pages= 143–148|doi=10.1002/cber.19921250123|title=Organomolybdän- und Organowolfram-Reagenzien, II. über den carbonylolefinierenden μ-Methylenkomplex aus Mo2Cl10 und vier äquivalenten Methyllithium}} {{DEFAULTSORT:Kauffmann Olefination}}2. ^{{cite journal|author1=T. Kauffmann |author2=P. Fiegenbaum |author3=M. Papenberg |author4=R. Wieschollek |author5=D. Wingbermühl |journal=Chem. Ber.|year=1993|volume=126|pages= 79–87|doi=10.1002/cber.19931260114|title=Organomolybdän- und Organowolfram-;Reagenzien, III. Chemoselektive, nichtbasische Carbonylmethylenierungs-;Reagenzien aus MoOCl3(THF)2 und MoOCl4: Bildung, Thermolabilität, Struktur}} 3. ^{{cite journal|author1=T. Kauffmann |author2=J. Braune |author3=P. Fiegenbaum |author4=U. Hansmersmann |author5=C. Neiteler |author6=M. Papenberg |author7=R. Wiescholleck |journal=Chem. Ber.|year=1993|volume=126|pages= 89–96|doi=10.1002/cber.19931260115|title=Organomolybdän- und Organowolfram-;Reagenzien, IV. über die Chemoselektivität des carbonylmethylenierenden Reagenzes aus 2 MoOCl3(THF)2 und 4 CH3Li}} 4. ^{{cite journal|author=T. Kauffmann|journal=Angew. Chem.|year=1997|volume=109|pages= 1312–1329|doi=10.1002/ange.19971091205|title=Neue Reaktionen molybdän- und wolframorganischer Verbindungen: Additiv-reduktive Carbonyldimerisierung, spontane Umwandlung von Methyl- in μ-Methylenliganden und selektive Carbonylmethylenierung|issue=12}} 5. ^{{cite journal|author1=K. Oesterreich |author2=D. Spitzner |journal=Tetrahedron|year=2002|volume=58|pages= 4331–4334|doi=10.1016/S0040-4020(02)00336-8|title=Short total synthesis of the spiro[4.5]decane sesquiterpene (−)-gleenol|issue=21}} 6. ^{{cite journal|author1=K. Oesterreich |author2=I. Klein |author3=D. Spitzner |journal=Synlett|year=2002|pages= 1712–1714|title='One-pot' Reactions: Total Synthesis of the Spirocyclic Marine Sesquiterpene, (+)-Axenol | doi = 10.1055/s-2002-34211 }} 3 : Name reactions|Carbon-carbon bond forming reactions|Olefination reactions |
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