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Kauffmann Olefination
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 reagent The reagent was generated ''in situ'' by conversion of different halogenides of molybdenum or tungsten with methyllithium at low temperatures (−78 °C). During the warm-up process the formation of the active reagent occurs. NMR-experiments have shown that the active reagent is not a Schrock carbene (e.g. Tebbe-reagent). Mechanism Mechanism experiments shows that the olefination process is a sequence of cycloaddition and cycloelimination steps. Applications For a long time this reaction had no applications in synthetic organic chemistry. In 2002 it was used in a total synthesis of the terpene gleenol as a mild and non-basic reagent in a one-pot-protocol with an olefin metathesi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldehydes
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and play important roles in the technology and biological spheres. Structure and bonding Aldehydes feature a carbon center that is connected by a double bond to oxygen and a single bond to hydrogen and single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen. The central carbon is often described as being sp2- hybridized. The aldehyde group is somewhat polar. The C=O bond length is about 120-122 picometers. Physical properties and characterization Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile aldehydes have pungent odors. Aldehy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
