Thianthrene complexes

Thianthrene complexes in solution with Ag(I) via a sulfur (70OMR491). It seems that thianthrene can serve as a mono- or a bidentate ligand. Thus,... 

Adam and Lohray122 have used thianthrene 5-oxide (88) as a mechanistic probe in oxidations with transition metal peroxides. They oxidized 88 with various diperoxo complexes of chromium, molybdenum and tungsten and formulated a plausible mechanism on the basis of the products formed, 89 and 90. 

Likewise, pyridines such as methyl isonicotinate 1999 or quinolines are readily oxidized by BTSP 1949 in the presence of HOReOs in CH2CI2 to give, after 6 h at 24°C, 98% yield of, e.g., methyl isonicotinate N-oxide 2000 [174] (Scheme 12.49). The oxidation of diphenylsulfide with BTSP 1949 and triphenylphosphine dichloride in acetonitrile results, after 60 h at room temperature, in only 12% diphenyl sulfoxide 2001 and 88% recovered diphenyl sulfide [175] (Scheme 12.49), whereas thianthrene 5-oxide 2002 is oxidized by the peroxy-Mo complex 2003 to give 58% of a mixture of 2004 to 2007 in which the trans 5,10-thioxide 2005 predominates [176] (Scheme 12.50). 

The formation of the thianthrene cation-radical complex with anisole, that is, (HetH) + ArH (HetH---ArH)+ ... 

To increase the stationary concentration of complex (HetH - - - ArH) +, a stronger oxidizer, as compared to the cation-radical of thianthrene, should be introduced into the reaction. This is the cation-radical of dibenzodioxine. It increases the rate of the reaction by 2 orders. 

Cycloaddition of dimethylbutene (DMB) to the thianthrene cation-radical [(HetH) ] also includes the stage of complexation and oxidation, but in this case the same (HetH)+ is capable of being an additional oxidant (Zhao et al. 2006) ... 

A complex reducing agent (CRA), dubbed NiCRA-bpy, was 99% effective in converting thianthrene into diphenyl over 18 hrs over 89 hrs, benzene (83%), diphenyl (8%), and dibenzothiophen (3%) were the products. The reductant was a4 2 1 2 mixture of NaH, /-AmONa, Ni(OAc)2, and bpy (88TL2963). 

A comparable monodentate role, but without crystallographic support, was proposed on the basis of UV spectroscopic analysis for complex 77 from reaction of [(bpy)(tpy(RuCl]PF6 (tpy = 2,2 6,2"-terpyridine) with thianthrene and Ag" " at room temperature (85IC1464). 

Fig. 7. Stacking of molecules in crystals of a charge-transfer complex between thianthrene and the dimer of quinone.

After (presumed). S-alkylation of diphenyl sulfide with Meerwein s reagent, heating the resultant material at 175°C gave a small quantity of thianthrene as a component of a complex product mixture (71JOC1513). 

SrnI processes have been shown to be relevant to the synthesis of simple thianthrenes which is done by irradiating the disodium salt of 4-methylbenzene-1,2-dithiol in the presence of 1,2-bromochlorobenzene (55%) or 1,2-di-iodobenzene (64%). More complex, fused thianthrenes result from l-bromo-2-iodonaphthalene (24%, 2 isomeric products) and 2,3-dichloroquinoxaline (100%). These clearly hold considerable promise for the controlled construction of unsymmetrical thianthrenes (87JOC1089). 

Generation of benzyne in the presence of 1,4,2-benzodithiazine gave a low yield of thianthrene among a complex product mixture (82CC612). 

To decrease the stationary concentration of complex (HetH ArH)2+, it will suffice to lower the concentration of the oxidizer, i.e., substrate (HetH)+. This also decreases the equilibrium concentration of the cation radical complex (HetH ArH)+. The rate of anisylation—the main process—drops sharply. The side process, one-electron transfer from anisole to the cation radical of thianthrene, also decelerates, but not so markedly. So this side process (route b on Scheme 5-6) remains the only one. 

Computational studies showed that the nature of the reactive species in the oxidation of trimethylamine, iodide ion, and dimethyl sulfide with lumiflavin is a C4 a-hydroperoxide complexed with water. The other two species, C4 a-hydroperoxide and C4 a-peroxide, yielded higher activation energies.237 Kinetic and spectroscopic studies on the effect of basic solvents, ethers, esters, and amides, on the oxidation of thianthrene-5-oxide with substituted peroxybenzoic acids indicated the involvement of the basic solvent in the transition state of the reactions. A solvent parameter, Xtc, based on the ratio of the trans to the cis form of thianthrene-5,10-dioxide, has been introduced.238... 

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