Smiles rearrangement substitution

Nucleophilic substitutions of halogen by the addition-elimination pathway in electron-deficient six-membered hetarenes by sulfinate anions under formation of sulfones have been described earlier120. The corresponding electron-poor arenes behave similarly121 (equation 30). A special type of this reaction represents the inverse Smiles rearrangement in equation 31122. 

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). 

The cine substitution of phenyl 3-nitro-4-thienyl sulfone has been discussed in Section 3.14.3.5. An intramolecular example of cine substitution by an AEa mechanism is provided by the Truce-Smiles rearrangement of the sulfone (459) to (460) (78JOC101). PhS02 as a leaving group has a higher steric requirement than Br in nucleophilic substitution reactions. In order to give a unified picture, details are deferred to Section 3.14.3.8. 

Publications on other types of rearrangements involving tetrazoles are cited at length in a review <2004SOS(13)861> in particular, the Smiles rearrangement of 2-[(l-alkyl/aryl-17/-tetrazol-5-yl)sulfanyl]pyridine-3-amines 208 to 3-[(l-alkyl/aryl-l/7-tetrazol-5-yl)amino]pyridine-2(l/f)-thiones 209 under acidic conditions and Smiles rearrangement of 5-sulfanyl/sulfone-substituted tetrazoles 210 to tetrazol-5-amines 211 under basic conditions (Scheme 19) <2004SOS(13)861>. 

Another reaction to yield unsymmetrically substituted 1,2,4,5-tetrazines is that of sodium ethoxide in ethanol with S-( 1 -aryl-1 7/-tetrazol-5-y 1) lV-(/Miitrophenyl)benzothiohydrazonates (11). The mechanism of the reaction is complex and seems to involve a competitive Smiles rearrangement, fragmentation and dimerisation (Scheme 7) [95JCR(S)224],... 

Chloro-5-formyl-l,3-dimethyluracil reacts, furthermore, with 2-aminothiophenole in the presence of l,5-diazabicyclo-[4,3,0]non-5-ene (DBN) via a Smiles rearrangement to afford pyrimido[4,5-6][l, 4]benzothi-azine, while, without base, a simple condensation-substitution step leads to the formation of pyrimido[4,5- ]-[ 1,5]benzothiazepines (85UP1) (Scheme 104). 

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