SMILES Aromatic rearrangement

Smiles rearrangement Intramolecular nucleophilic aromatic rearrangement of activated aromatic substrates. 416... 

The ratio between the isomeric phenoxazine products suggests that the main route of cyclization is a direct attack of the second nucleophilic center at the ortho-carbon atom of the aromatic ring an alternative route is a Smiles type rearrangement (70M9). Therefore, the following route of cyclization was proposed (Scheme 171). 

Heteroatom Heteroatom Aromatic Rearrangements (Smiles Rearrangement) The... 

Heteroatom Carbon Aromatic Rearrangements (Truce-Smiles Rearrangement)... 

In the Schmidt reaction of fluonnated dicarboxyhc acids, the appropnate amides can be obtained in fairly good yield [48] Complications arise from possible cychzation if the fluorine atom is in the 8 position relative to the newly formed amino group [/] Fluonnated aromatic ethers, upon heating in dimethylformamide, undergo Smiles rearrangement to give diarylamines [49, 50] (equation 11)... 

Directed lithiation of aromatic compounds is a reaction of broad scope and considerable synthetic utility. The metalation of arenesulfonyl systems was first observed by Gilman and Webb and by Truce and Amos who reported that diphenyl sulfone is easily metalated at an orf/io-position by butyllithium. Subsequently, in 1958, Truce and coworkers discovered that metalation of mesityl phenyl sulfone (110) occurred entirely at an orf/io-methyl group and not at a ring carbon, as expected. Furthermore, refluxing an ether solution of the lithiated species resulted in a novel and unusual variation of the Smiles rearrangement and formation of 2-benzyl-4,6-dimethyl-benzenesulfinic acid (111) in almost quatitative yield (equation 78). Several other o-methyl diaryl sulfones have also been shown to rearrange to o-benzylbenzenesulfinic acids when heated in ether solution with... 

Nowhere, perhaps, is this phenomenon better illustrated than in the phenothiazine class. The earlier volume devoted a full chapter to the discussion of this important structural class, which was represented by both major tranquilizers and antihistamines. The lone phenothiazine below, flutiazin (130), in fact fails to show the activities characteristic of its class. Instead, the ring system is used as the aromatic nucleus for a nonsteroidal antiinflammatory agent. Preparation of 130 starts with formylation of the rather complex aniline 123. Reaction with alcoholic sodium hydroxide results in net overall transformation to the phenothiazine by the Smiles rearrangement. The sequence begins with formation of the anion on the amide nitrogen addition to the carbon bearing sulfur affords the corresponding transient spiro intermediate 126. Rearomatization... 

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). 

Among the more recent approaches to phenoxazines and phenothiazines the reductive cyclization of 2-nitrodiphenyl ethers and sulfides with trialkyl phosphites is the most interesting. Here too a spiro intermediate is involved, produced by attack of an initially formed aryl nitrene on the second aromatic ring. The sulfide (252), for example, reacts with triethyl phosphite to yield 1-methylphenothiazine (253) and it is clear that in this case ring opening of the spiro intermediate also proceeds with a rearrangement of the Smiles type (Scheme 113) (75JCS(P1)2396). 

The photoaddition to aromatic ring is simply classified in Table 13. Direct attack of nucleophiles such as cyanide anion and carbanion to aromatic rings in the excited species has been recognized by SRN2 reactions [Eq. (4)], which were discussed in the past three decades [27,28], We will discuss briefly some examples in this section, including intramolecular photocyclization such as photo-Smiles rearrangement. 

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