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2.5.15 Wittig reaction
[6, Ullmann, 2001, 9, Christ, 1999], *003F*
Chapter 2
The Wittig reaction is widely used in the production of vitamins, carotenoids, pharmaceuticals
and antibiotics. *003F* used Wittig reactions for the manufacture of fragrances but can no
longer due to the difficult handling of the waste streams.
Chemical reaction
The Wittig reaction leads to the formation of a double bond in three steps:
(1) R’ – CH2 – Cl + P(C6H5)3 � R’ – CH2 – P + (C6H5)3Cl -
(2) R’ – CH2 – P + (C6H5)3Cl - � R’ – CH = P(C6H5)3
(3) R’ – CH = P(C6H5)3 + R” – CHO � R’ – CH = CH – R” + O = P(C6H5)3
The deprotonation step (2) requires bases, e.g. alkali metal carbonate or amines. The reaction is
carried out in organic solvents such as alcohols or DMF or in aqueous solutions.
High yields are achieved under mild reaction conditions. However, equimolar amounts of
triphenylphosphine (TPP) must be used, and the inactive triphenylphosphine oxide (TPPO) is
formed.
Operations
Because Wittig reactions are diverse in nature, there is no universal method of carrying them
out. The production of each compound is thus considered individually, assessing the chemical,
engineering, and economic factors.
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