Ring transfer process

As with other hydroperoxides, hydroxyaLkyl hydroperoxides are decomposed by transition-metal ions in an electron-transfer process. This is tme even for those hydroxyaLkyl hydroperoxides that only exist in equiUbrium. For example, those hydroperoxides from cycHc ketones (R, R = alkylene) form an oxygen-centered radical initially which then undergoes ring-opening -scission forming an intermediate carboxyalkyl radical (124) ... 

Far superior yields of l-(arylsulfonyl)-l//-azepines 16 are now available by a one-pot synthesis involving the action of sodium azide on an arylsulfonyl chloride under solid-liquid phase-transfer conditions which prevents the formation of acidic sulfonamides and, hence, the ring-contraction process.75 This procedure also has the advantage of avoiding the use of high pressures and the isolation and handling of the potentially explosive sulfonyl azides. 

At high copper(II) chloride indole ratios the pyrrole ring of 2-methylindole was chlorinated in yields approaching 92%. This reaction is believed to involve radical cations of indoles formed in an electron-transfer process. At low copper(ll) chloride indole ratios dimers were formed [86JCS(P 1)2305]. 

The ESR spectrum of the furan radical anion indicates that the Cem-0 bond is ruptured in the electron transfer process whereby the oxygen atom acquires the negative charge and the C-2 end of the open ring possesses a free radical character ... 

HT (hole transfer) processes, and by what mechanism would the charge transfer take place, superexchange or by a conduction-like mechanism with the electron or hole hopping between aromatic rings ... 

CH4/O2 and CF4 as the reactant gases and observed the formation of [M — 4 H] ions in the Cl plasma (Scheme 13)166. Thus, repeated deprotonation and electron transfer processes appear to offer an efficient access to more highly unsaturated and/or ring condensed trimethylenemethane radical anions. The [M — 4 H]- ion is considered identical to the molecular radical anion (42) of acepentalene (43), which was generated as a short-lived species from the former by neutralization-reionization mass spectrometry167. Efforts to apply Squires methodology to triquinacene 41 and the tribenzotriquinacenes 44 have been made168. 

Arylamines and hydrazines react with tosyl azide under basic conditions to yield aryl azides [1] and arenes [2], respectively, by an aza-transfer process (Scheme 5.25). Traditionally, the reaction of anilines with tosyl azides requires strong bases, such as alkyl lithiums, but acceptable yields (>50%) have been obtained under liquidiliquid phase-transfer catalytic conditions. Not surprisingly, the best yields are obtained when the aryl ring is substituted by an electron-withdrawing substituent, and the yields for the corresponding reaction with aliphatic amines are generally poor (-20%). Comparison of the catalytic effect of various quaternary ammonium salts showed that tetra-/i-butylammonium bromide produces the best conversion, but differences between the various catalysts were minimal [ 1 ]. 

Benzene and naphthalene rings having an electron withdrawing carboxylic acid or ester substituent are more easily reduced by an electron transfer process than the parent hydrocarbons themselves, Phthalic acid 13 and terephthalic acid 14 are converted to the dihydro derivatives at a lead cathode in sulphuric acid [49, 50]. These... 

The cyclic voltammograms of thiadiazole fused [2,5-(l,3-dithiol-2-ylidene)-l,3,4,6-tetrathiapentalenes], BDT-TTPs 88, in benzonitrile exhibited four pairs of redox waves corresponding to one-electron transfer processes at 4-0.60, 4-0.81, 4-1.30, and 4-1.47 V (vs. saturated calomel electrode (SCE)). The El values are a little higher than that of 4,5-bis(methylthio)-BDT-TTP (4-0.49 V). The difference is attributed to the electron-withdrawing character of the fused thiadiazole ring on the bicycle <1997SM(86)1821>. 

The TTF-porphyrin dyad 3 was described by the group of Odense.11 The fluorescence of 3 is significantly quenched by the photoinduced electron transfer process. Notably, the fluorescence intensity of dyad 3 increases largely after addition of Fe3 + that oxidizes TTF into TTF" +. Successive reduction of TTF" + is not reported. Nevertheless, it is anticipated that the fluorescence of dyad 3 can be reversibly modulated by redox reactions. In fact, the fluorescence of the supramolecule 4, formed between Zn-tetraphenylporphyrin and a pyridine-substituted TTF (TTF- ), can be reversibly tuned by sequential oxidation and reduction of the TTF moiety in 4.12 It should be noted in this context that the synthetically challenging system associating a porphyrin ring fused to four TTFs (5) was also reported.13... 

A limited number of reports of indoles arising from o-bromoaniline and enolates have appeared (equation 107) (80JOC1546,8lT(S9)393). The final cyclization step is of the condensation type already recognized in several other procedures. The inertness of unactivated halobenzenes, such as o-bromoaniline, requires an alternative to direct aromatic nucleophilic substitution and those cases where success has been reported depend upon photoinitiated substitution by an electron transfer process. The scope of this method remains to be explored but it appears that alkyl, alkoxy and carboxy groups can be tolerated on the aromatic ring. When the enolates are derived from an unsymmetrical ketone in which one group is methyl, there appears to be a preference for exclusive involvement of the less substituted enolate, leading to 2-alkylindoles. 

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