Smiles rearrangement mechanism

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. 

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],... 

Single electron transfer (SET), as antioxidant mechanism 844, 896, 897 Size exclusion chromatography 953 Slash pine bark, phenolic compounds in 944 Smiles rearrangement 466-470, 759 S Ar reactions 673 Soil samples, phenolic compounds in, analysis of 932, 965, 972, 985 field screening of 938 Sol-gel technique 1082 Solid acid catalysis 612-621 Solid-phase extraction (SPE) 930-933, 936, 942, 944-950, 955, 958, 960, 962-964, 969, 972, 985, 986, 995, 1354 Solvation energy 500, 992 Solvation free energy 5 Solvatochromic comparison method, for solvent hydrogen-bond basicity 591 Solvent effects,... 

The a-CD complexation proved to be effective in modifying the course of the photo-Smiles rearrangement of p-nitrophenyl ethers 100 (Scheme 18). The reaction mechanism in solution involves a heterolytic nucleophilic attack on the triplet state to give the high-energy zwitterionic final product either directly or by irreversibly losing a proton (base-catalyzed reaction). In the base-catalyzed... 

Propose a detailed mechanism for the Smiles rearrangement shown as equation 8.74, page 530. 

A range of substrates have been deemed successful in the Smiles rearrangement under basic conditions, but notable examples revealing its versatdity are shown in Figure 18.1, all of which proceed via the same mechanism to that shown in Scheme 18.1. 

Although the mechanism of this process was not studied, a plausible mechanistic hypothesis is invoked by the authors (Scheme 8.4). On the latter, the nitrophenol 16 is assumed to act as acid surrogate activating the aldehyde to promote the further isocyanide addition. The resulting nitrilium 17 is trapped by the nucleophilic phenoxide generating imidate intermediate 18, which undergoes a final Smiles rearrangement [15,16] to provide the more stable a-aryloxy amide 15 (Scheme 8.4). 

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