Demjanov rearrangement

Source: Wikipedia, the free encyclopedia.

The Demjanov rearrangement is the

Nikolai Jakovlevich Demjanov (Dem'anov, Demianov),[4]
who first reported it in 1903.

Reaction mechanism

The reaction process begins with

nitrogen gas when displaced from the organic structure. This displacement can occur via a rearrangement (path A), in which one of the sigma bonds adjacent to the diazo group migrates. This migration results in an expansion of the ring. The resulting carbocation is then attacked by a molecule of water. Alternately, the diazo group can be displaced directly by a molecule of water in an SN2 reaction (path B). Both routes lead to formation of an alcohol.[5]

A.
B.

Uses

The Demjanov rearrangement is a method to produce a 1-carbon ring enlargement in four, five or six membered rings. The resulting five, six, and seven-membered rings can then be used in further synthetic reactions.

It has been shown that the Demjanov reaction is susceptible to regioselectivity. One example of this is a study conducted by D. Fattori looking at the regioselectivity of the Demjanov rearrangement in one-carbon enlargements of naked sugars.[6] It showed that when an exo methylamine underwent Demjanov nitrous acid deamination, ring enlargement was not produced.

However, when the endo methylamine underwent the same conditions, a mixture of rearranged alcohols were produced.

Problems

This rearrangement also leads to a substituted, but not expanded, byproduct. Thus it can be difficult to isolate the two products and acquire the desired yield. Also, stereoisomers are produced depending on the direction of addition of the water molecule and other molecules may be produced depending on rearrangements.

Variations

Tiffeneau-Demjanov rearrangement

The

hydrogen cation
. Using the Tiffeneau-Demjanov reaction is often advantageous as, while there are rearrangements possible in the products, the reactant always undergoes ring enlargement. As in the Demjanov rearrangement, products illustrate regioselectivity in the reaction. Migratory aptitudes of functional groups dictate rearrangement products.

Use of diazomethane

Tiffeneau-Demjanov rearrangement
.

References

  1. ^ Demjanov, N. J.; Lushnikov, M. (1903). "[Products of the action of nitrous acid on tetramethylenylmethylamine]". Zhurnal Russkago Fiziko-Khimicheskago Obshchestva [J. Russ. Phys. Chem.] (in Russian). 35: 26–42.
  2. ^ Demjanov, N. J.; Lushnikov, M. (1903). Chem. Zentr. 1: 828. {{cite journal}}: Missing or empty |title= (help)
  3. ^ Smith, P. A. S.; Baer, D. R. (1960). Org. React. 11: 157. {{cite journal}}: Missing or empty |title= (help) (Review)
  4. ^ Jack Li, Jie (2006). Name Reactions (Third ed.). Berlin: Springer.
  5. PMID 14985802
    .
  6. doi:10.1016/S0040-4020(01)80352-5
    .
  7. doi:10.1021/jo00987a023
    .
  8. doi:10.1021/jo01013a009
    .
  9. doi:10.1021/jo01017a030
    .
  10. doi:10.1021/jo00161a033
    .
  11. doi:10.1016/0040-4020(73)80128-0
    .
  12. doi:10.1021/jo00046a015
    .
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