Von richter rearrangement smile rearrangement

1. Von Richter Rearrangement
& Smiles Rearrangement
Submitted By :- Dalpat Singh

2. Von Richter Rearrangement :-
It is called Hydro-de-nitro-cine-substitution. When aromatic nitro compounds are
treated with cyanide ion, the nitro group is displaced and a carboxyl group enters
always ortho to the displaced group never meta or para.
It is an example of Cine substitution. As with other nucleophilic aromatic
substitutions, the reaction gives best results when electron-withdrawing groups are
in ortho and para positions

3. Mechanism :-
..

4. • N2 is a major product of the reaction. This indicates that nitrogen-nitrogen bond
must be formed during the course of the reaction
• (46) is a stable compound; hence it should be possible to prepare it independently and
to subject it to the conditions of the von Richter rearrangement. This was done and
the correct products are obtained.
• When the reaction was performed in H2
18O , with CN–
, half the oxygen in the
product was labelled, showing that one of the oxygen of the carboxyl group came
from the nitro group and one from the solvent, as required by this mechanism.
• When the reaction is carried out in the presence of D2O/C2H5OD, the carboxylic
acid formed contains the deuterium at the position originally occupied by the NO2
group. This confirms the formation of species.
Evidences in support of the above mechanism :-

5. Smiles Rearrangement :-
The Smiles rearrangement actually comprises a group of rearrangements that follow the
pattern given above -

6. Smiles rearrangements are simply intramolecular nucleophilic substitutions. In the
example given, SO2Ar is the leaving group and ArO
- the nucleophile, and the nitro
group serves to activate its ortho position.
Here X is usually S, SO, SO2, O, or COO, and Y is usually the conjugate base of
OH, NH2, NHR, or SH. The reaction has even been carried out with YH = CH3
(phenyl lithium PhLi was the base here) , in this case this reaction is called truce
smiles rearrangement.

7. • Z and Z’ are activating groups for nucleophilic aromatic substitution reaction. Z or Z‘
should be an electron with drawing group such as –NO2 , -CN , or CF3 to stabilize the
cyclohexadienylide anion formed.
• In this rearrangement the chain linking X and Y can be aromatic as well as aliphatic. This
rearrangement also takes place in heterocyclic aromatic systems.
Examples of substrates which follows smiles rearrangement:-

8. Examples of smile rearrangement :-

9. • The presence of an electron with drawing group para to the YH in the substrate retards
the rate of the smiles rearrangement because such groups reduce the nucleophilicity of Y
-

10. Thank you
Submitted to :- Dr. M.R.K. Sherwani