Intramolecular reactions Smiles rearrangement

Intramolecular cyclization can yield fluorinated phenoxazines by a Smiles rearrangement (86IZV1855) and 2,3-dihydro-l,4-benzodioxins by a base-induced reaction [81JFC(18)483]. 

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. 

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. 

Photoamination of arenes the nucleophilic photosubstitution SN2Ar was briefly discussed in Section 6.2.3. An intramolecular version of such a reaction, termed photo-Smiles rearrangement, is shown in Scheme 6.199.1226... 

Intramolecular nucleophilic photosubshtutions have also been reported. The most commonly found example is the photo-Smiles rearrangement, which is the conversion of aryl-co-aminoalkylethers into the corresponding substituted anilines upon irradiahon [10, 97, 98]. Recently, the photochemistry of (Z)-N-acyldehy-droarylalaninamides in methanol in the presence of a base, such as DBU or triethylamine (TEA), has been reported and found to produce substituted dihydroquinolinones in high yields (Scheme 14.20) [99-101]. The reaction is initiated by ET from the amine to the excited state of the amide. Competitive side reactions were also observed, thereby lowering the yields of the cyclized products. 

Substitution of pentafluoropyridine with 2-bromothiphenol yields the 4-substituted derivative (54). Further treatment with butyl lithium results in lithium-bromine exchange followed by intramolecular substitution of the 3-fluorine to give the cyclized product (55). In the corresponding reaction with 2-bromophenol, the final product, (56), is likely to be formed following a Smiles rearrangement of the lithiated intermediate. There has been a detailed kinetic and computational study of the substitution of fluorine at the 6-position of 2,5,6-trifluoronicotinonitrile by... 

The Smiles rearrangement followed by intramolecular cyclization of 2-(3-cyanopropoxy)-6-methylpyridine-3-carbonitrile (13) in the presence of potassium tert-butoxide in dioxane afforded 5-amino-8-methyl-l,2-dihydrofuro[2,3-/ ][l,6]naphthyridine (14) in 83% yield. The structure of 14 was assigned with the help of spectroscopic data and elemental analysis. The precursor 13, in turn, was obtained from the reaction of 6-methyl-2-oxo-l,2-dihydropyridine-3-carbonitrile (12) with 4-bromobutyronitrile in DMF. 

The intramolecular displacement of an aromatic nitro group by N-substituted carboxamides, under mild conditions, to furnish 5-substituted pyrroloquinoxalinones, has been reported. The reaction of carboxamide 105 with NaH in DMF afforded pyrroloquinoxalinones 106 and a carboxamide 107. Further, 107 when treated with NaH in DMF for 4.5 h gave 106 as the sole product. From the above reactions, it has been confirmed that the carboxamide 105 undergoes a Smiles rearrangement to give 107. 

The carboxylic acid 163 underwent an initial loss of water and in situ Smiles rearrangement involving S—>N migration to afford the ketone 167. The reaction of 163 with l,r-carbonyldiimidazole (CDI) resulted in the formation of 164, which then underwent intramolecular nucleophilic substitution by the sulfur atom at the activated 7V-carbonyl carbon of 164 to give the intermediate 165. Subsequent displacement afforded 166, which finally on ring contraction gave 167. ... 

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