Nucleophilic aromatic substitution intramolecular rearrangements

Excited-state intramolecular nucleophilic aromatic substitutions are known as photo-Smiles rearrangements. Ealier, these were reported for 2,4-dinitrophenyl ethers and. v-lriazinyl ethers32. The exploratory33 and mechanistic34 studies on photo-Smiles rearrangements of p-(nitrophenoxy)- >-anilinoalkanes were carried out (equation 28). 

Smiles rearrangement. Intramolecular nucleophilic aromatic substitution in alkaline solution resulting in the migration of an aromatic system from one heteroatom to another. 

The Smiles rearrangement occurs via an intramolecular nucleophilic aromatic substitution as shown below. ... 

Despite both intramolecular and intermolecular mechanisms for the Chapman rearrangement having been postulated [28], it is the intramolecular one that has been confirmed by crossover experiments and isotopic labeling studies [29]. It has also been observed that the rearrangement follows first-order kinetics involving a nucleophilic aromatic substitution step [30]. 

Although chlorobenzene is rather inactive in usual reactions, its activity is enhanced by complex formation, and two products are formed by the reaction of stabilized carbanions on the complexed chlorobenzene 207, depending on the conditions [44], The anion of a-methy l propionitrile reacts at the meta position at —78 °C, and the mete-substituted product 208 is obtained by oxidation with I2. However, equilibration (rearrangement) of the carbanion occurs at 25 °C, because the attack of the carbanion is reversible, and the substitution product 209 of the chlorine is obtained. The fluorobenene 210, coordinated by Cr(CO)3, is very reactive. Reaction of y-butyrolactone to the o-lithiated fluorobenzene 211 gives rise to the alkoxide 212, which displaces the fluoride intramolecularly to give the cyclic ether 213 [52], In other words, the complex 211 can be regarded as the 1,2-dipolar synthon 214. However, Cr(CO)3-complexed aromatic bromide and iodide can not be used for the nucleophilic substitution. 

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