Corey-Kim oxidation
The Corey-Kim oxidation or Corey-Kim reaction was first described in 1972 by the American chemist Elias James Corey and Choung Un Kim. The reaction makes it possible to oxidize primary or secondary alcohols by adding gaseous chlorine (Cl 2 ) and dimethyl sulfide to the corresponding aldehydes or ketones . It is easy to use, very selective and efficient. The Corey-Kim oxidation is related to the Dess-Martin oxidation , the Swern oxidation and the Pfitzner-Moffatt oxidation .
mechanism
First, dimethyl sulfide ( 1 ) is reacted with chlorine (Cl 2 ), whereby the sulfonium salt ( 2 ) is formed. A primary or secondary alcohol that you want to oxidize is added to this. This forms molecule 4 , which by rearrangement of electron pairs allows hydrogen chloride (HCl for short) to escape from the molecule and itself becomes a dimethylalkoxyalkane 5 . 5 and 6 are two mesomeric boundary structures. If this is now worked up with a base (here triethylamine ), a methyl group of the sulfur is deprotonated, whereby the sulfonium ylide 7 is obtained. As a result of β-elimination with a cyclic transition state, the dimethyl sulfide used at the beginning is split off and the desired aldehyde (R 1 = organic radical , R 2 = hydrogen atom) or the desired ketone (R 1 , R 2 = organic radical) is formed. The dimethyl sulfide thus only acts as a catalyst in this reaction.
In laboratory use, instead of chlorine (Cl 2 ), N -chlorosuccinimide (NCS for short) is often used, as this can prevent the formation of hydrogen chloride. In industry, however, this is not done for reasons of cost.
Individual evidence
- ↑ a b Zerong Wang: Comprehensive Organic Name Reactions and Reagents: 3 Volume Set . Volume 1, John Wiley & Sons Inc., pp. 727, ISBN 978-0-471-70450-8 .