Intramolecular oxygen-transfer redox

A synthetic route to 3-pyrrolidinone and nitrone derivatives from A-sulfonyl hydroxylamines via gold-catalysed intramolecular oxygen-transfer redox cyclization and [l,3]-sulfonyl migration has been reported (Scheme 121). ... 

When 4-nitro-7-phenylthiobenzofuroxan (195) was oxidized by m-chloroperbenzoic acid, an intramolecular redox reaction resulted in the formation of the benzofurazan sulfone (197).443 It has been shown that the sulfoxide (196) (and a number of analogous compounds) can be isolated, and that it is thermally converted into 197.444 This result is interesting in view of the reported failure to observe intramolecular oxygen transfer in a number of fused furoxans.35 0,445... 

The redox properties can be divided among those involved with its reduction by potential substrates of the enzyme, its reoxidation by molecular oxygen, and by electron transfer to and from other redox centers within the molecule. Type 1 Cu + is reduced rapidly by a variety of both one-electron and potential two-electron substrates via a one electron process 63, 64). A likely reason for this ease of reduction of Type 1 Cu2+ ion lies with its exceptionally high redox potential (0.77 V at pH 6.2, Table 2). Introduction of molecular oxygen to reduced laccase results in a rapid reappearance of the blue color characteristic of Type 1 Cu2+. The question of intramolecular electron transfer occurring during reoxidation will be considered below. 

Thiocarbamate (tc, RHNCSO-) is a monodentate ambidentate ligand, and both oxygen- and sulfur-bonded forms are known for the simple pentaamminecobalt(III) complexes. These undergo redox reactions with chromium(II) ion in water via attack at the remote O or S atom of the S- and O-bound isomers respectively, with a structural trans effect suggested to direct the facile electron transfer in the former.1045 A cobalt-promoted synthesis utilizing the residual nucleophilicity of the coordinated hydroxide in [Co(NH3)5(OH)]2+ in reaction with MeNCS in (MeO)3PO solvent leads to the O-bonded monothiocarbamate, which isomerizes by an intramolecular mechanism to the S-bound isomer in water.1046... 

Our study was based initially on 2-nitrobenzyl derivatives. Cleavage of this group occurs at 350 nm. The mechanism involves an intramolecular redox reaction i.e., the transfer of an oxygen from the nitro group to the benzylic carbon atom. This is... 

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