Author Topic: Beckmann rearangement  (Read 1285 times)

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Captain_Mission

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Beckmann rearangement
« on: March 31, 2002, 05:56:00 PM »
As far as TFSE showed this reaction hasn´t been given much notice at the Hive. Undeservingly, I might say,because it seems to have a great potencial for clandestine chemistry.

  It is related to the Schmidt rearrangement (although it only applies to aldehydes and ketones) in the sense that the intermediate product is the same, but it doesn´t involve the use of NaN3 or HN3.
  It consists on turning a Ketoxime or an aldoxime into an N-alkyl amide, using a Lewis acid like H2SO4 or PCl5 according to the following scheme:
               
                        +H+
                        -H 2O
      (R)2-C=N-OH -------> R-C+=N-R

        H 2O
        -H+
       -------> R-(C=O)-NH-R

  The book where I took this from says that, for unsimetrical ketones, the rate of migration of the R groups should be similar to the Schmidt rearrangement:

         t-C4H9 > C6H5 ~ i-C3H7 > C2H5 > CH3

or, as a general rule, that the bulkier R group will migrate preferentialy.

   So, if I´m not mistaken, this offers the possiblity of turning, for example:
  -acetone oxime into N-methylacetamide(hydrolyse to get methylamine)
  - acetaldoxime into N-methyl formamide(you can also hydrolyse this one, if you want :) )
  -any phenylpropanal oxime into the corresponding N-formyl phenethylamine

 Unfortunately the only experimental procedures the book uses to "ilustrate" the rearrangement are for caprolactam from ciclohexanone oxime and Isatine from aniline and cloral hydrate and I don´t know how general these are. But some searching should dig up more usefull material. They also give some references:

      F. Möller, Houben-Weyl, Vol XI/1 page 872-876, 899-903 (1957)
      L. G. Donaruma and W. Z. Heldt, Org. reactions 11, 1-156 (1960)

and another one, a russian paper, I think, but it is written in cyrilic.

Captain_Mission

  • Guest
Come on, people!
« Reply #1 on: April 03, 2002, 03:09:00 PM »
I can´t believe nobody is interested in the possibility of making N-methylformamide from acetaldehyde and hydroxylamine :P .
   
If the procedure for this is like the one for caprolactam it should be as easy as dropping a solution of the oxime in conc. H2SO4 into hot H2SO4.

  Nobody cares to comment on this?  :(

Rhodium

  • Guest
Why
« Reply #2 on: April 03, 2002, 05:00:00 PM »
They probably are interested, but you have not come up with a verified synthetic procedure, just information that can be found in any organic chemistry book.

Moriarty

  • Guest
N-Methylformamide
« Reply #3 on: April 03, 2002, 05:28:00 PM »
H2SO4
NH2OH    +    CH3CHO----------------->CH3NHCHO   +    H2, right?
hydroxylamine  Acetaldehyde               N-Methylformamide

By definition, that should work.  By the way, when I started reading about this reaction I noticed that an article in the Journal of Organic chemistry, v. 28, p. 278, (1963), stated that this concept seems to work for all situations where the migrating alpha-carbon is not trisubstituted.  If so the intermediaries recombine in a Ritter reaction.

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