Kauffmann olefination
Encyclopedia
The Kauffmann olefination is a chemical reaction to convert aldehydes and ketones to methylene
-olefins. This reaction was discovered by the German chemist Thomas Kauffmann and is related to the better known Tebbe olefination or Wittig reaction
.
- or Tungsten
-halogenides with methyllithium at low temperatures (-78°C).
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).
Methylene
Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....
-olefins. This reaction was discovered by the German chemist Thomas Kauffmann and is related to the better known Tebbe olefination or Wittig reaction
Wittig reaction
The Wittig reaction is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide to give an alkene and triphenylphosphine oxide....
.
Formation of the reagent
The reagent was in situ-generated by conversion of different MolybdenumMolybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
- or Tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
-halogenides with methyllithium at low temperatures (-78°C).
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).