Disulfides diaryl

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

Sulfonyloxaziridines were recently proposed as O-transferring reagents. Oxaziridine (89) converted thioethers to sulfoxides (90) and diaryl disulfides into their 5-oxides (91) (78TL5171). Epoxidations are also possible (81TL917). 

Indolizine, hydroxy-conformations, 4, 451 GLC retention times, 4, 451 synthesis, 4, 121 tautomerism, 4, 198, 452 Indolizine, 2-hydroxy-synthesis, 4, 463 Indolizine, 8-hydroxy-conformation, 4, 452 Indolizine, 2-hydroxymethyl-synthesis, 4, 461 Indolizine, 3-hydroxymethyl-synthesis, 4, 461 Indolizine, 6-hydroxymethyl-synthesis, 4, 461 Indolizine, methyl-mass spectra, 4, 187, 450 NM 4, 448 Indolizine, 2-methyl-diazo coupling, 4, 454 mass spectra, 2, 529, 4, 450 nitration, 4, 50, 454 nitrosation, 4, 454 reaction with diaryl disulfide, 4, 460 reaction with nitroethane, 4, 460 Indolizine, 3-methyl-basicity, 4, 454 Indolizine, 5-methyl-acidity, 4, 461 synthesis, 4, 466 Indolizine, 6-methyl-mass spectra, 4, 450 Indolizine, l-methyl-2-phenyl-nitration, 4, 454 nitrosation, 4, 454, 455 Indolizine, 3-methyl-2-phenyl-reaction... 

Arylsulfenyl derivatives 151 were obtained from mesoionic 150 with diaryl disulfides in the presence of K2CO3 when air was bubbled through the reaction mixture (99M1147). u / yJro-(2-Hydroxy-4-oxo-4/7-pyrido[l,2-u]pyrimidinium)hydroxide (R = H) afforded 3-dialkylaminothiocarbo-nylthio derivatives 152 in the reaction of tetraalkylthiuram disulfides under similar conditions. 

The carbanion 5, formed from V,V-diethyl-5-phenyl-3//-azepin-2-amine (4) with potassium amide in liquid ammonia, or with lithium 2,2,6,6-tetramethylpiperidide in tetrahydrofuran, is thiolated by dialkyl or diaryl disulfides to yield 3-(alkylsulfanyl)-3//-azepines, e.g. 6.38... 

A wide range of dialkyf7 and diaryl disulfides,58 59 diaroyl disulfides,00 and xanthogens61 has been used as transfer agents (Scheme 6.8). Their use ideally leads to the incorporation of functionality at both ends of the polymer chain, thus they find application in the synthesis of tclcchclics (Section 7.5.2). 

Successive multiple insertions of an aryl isocyanide (ArNC) into the S-S bond of a diaryl disulfide (ArS)2 occurs in the presence of Pd(PPh3)4 to produce the corresponding poly(imino)alkane endcapped with an arylthio group (Equation (65)).167 Products of higher molecular weights are formed when isolated poly(imino)alkanes are again subjected to the conditions of the insertion reaction (up to n — 9). 

Introduction of two different chalcogen elements to the C-C unsaturated bond is of particular interest from both synthetic and mechanistic viewpoints. Therefore, extensive studies have been carried out on the development of the (RE)2/(R E )2 binary system without using RE-E R compounds, which are difficult to prepare. (Z)-l-Seleno-2-thio-1-alkenes are produced regio- and stereoselectively when a mixture of diaryl disulfides and diaryl diselenides is subjected to a rhodium-catalyzed reaction with alkynes (Equation (68)).193... 

Heating a mixture of diaryl disulfide (ArS)2, hexachlorodisilane (SiCl3)2, and alkynes under identical conditions provides a more convenient way to obtain thiosilylation products (Equation (122)). 

We turn now to consideration of the behavior of the anions of sulfenic acids, sulfenate ions. Basic hydrolysis (19) of a diaryl disulfide such as [ 11], that has several electron-withdrawing groups in the ring to help stabilize ArSO- and... 

Optically active aromatic thiosulfinates were first prepared by asymmetric oxidation of diaryl disulfides with (+)-percamphoric acid (105,112). Apart from the fact that the optical purity of diaryl... 

In an aprotic solution, the mechanism of oxidation of diaryl disulfides was shown to be more complex than a direct cleavage of the S—S linkage [116,117,123], The occurrence of two consecutive reactions being of second kinetic order if potential-determined and of first order if current-determined, was established for the two-electron transfer steps. Dimerization of the cation radicals occurs on the ArS fragment, whose contribution to the HOMO is more important, and produces an intermediate disulfonium dication. The subsequent cleavage of the latter results in two ArS+ cations and a molecule of a disulfide (the same as a starting disulfide in the case of symmetrical compounds). This mechanism, EC2C1E (E = electrochemical, C = Chemical), has... 

The direct electrosynthesis of sulfen-imines (19) from a-aminoalkanoates (18) and diaryl disulfides proceeds in a CH2CI2-H20-MgBr2-(Pt) system in 70 96% yields (Scheme 8) [50]. Electrolysis of sulfenami-des (20) is considered to be the intermediates in the direct conversion of (18)— (19). 

Di-/erJ-butylthianthrene and 1,3,6,8-tetra-tert-butylthianthrene were obtained from the diaryl sulfides in moderate yields by reaction with c. H2SO4 in nitromethane (68CB2956). A modified diaryl disulfide approach was based on intramoleculeir free radical substitution an o-phenoxy- (95% yield) or o-phenylthio-substituent (40% yield) being displaced as a radical (75G841). 

Besides the above data on PhSSPh, theoretical calculations were carried out also on a series of pura-substituted diaryl disulfides and corresponding radical anions. ... 

F. MARAN, D.D.M. WAYNER AND M.S. WORKENTIN Calculated parameters for the neutral diaryl disulfides and their radical... 

Table 12 Electrochemical, kinetic and thermodynamic parameters for the reduction of para-substituted diaryl disulfides (XPhS)2.

Fig. 14 Typical potential dependencies of the heterogeneous rate constant for the electroreduction of pora-substituted diaryl disulfides in DMF/O.IM TBAP. The dashed lines represent the parabolic fitting to the experimental data. The extrapolated standard potential and rate constant values (see text) are indicated.

A more recent investigation has been carried out on the homogeneous ET to an extended series of diaryl disulfides (X = NH2, OMe, H, F, C02Et, CN. NO2) in DMF. The redox catalysis approach was applied extensively. The mechanism of the homogeneous reaction between electrogenerated radical anion donors D and (ArS)2 takes place according to the sequence (equations 80-83) ... 

Fig. 15 Hammett plot of the logarithm of the heterogeneous ET rate constant for the electroreduction of diaryl disulfides in DMF. The solid line illustrates the experimental trend.

Fig. 16 Comparison between experimental ( ) and calculated ( concerted dissociative ET A stepwise dissociative ET) intrinsic ET barriers for the reduction of para-substituted diaryl disulfides in DMF/O.IM TBAP. The data are reported as a function of the corresponding standard potentials.

Thiols can be prepared by the reduction of sulfonyl halides652 with LiAIH4. Usually, the reaction is carried out on aromatic sulfonyl chlorides. Zinc and acetic acid, and HI. also give the reduction. Sulfonic acids have been reduced to thiols with a mixture of triphenyl-phosphine and either Ii or a diaryl disulfide.633 Disulfides RSSR can also be produced.634 For the reduction of sulfonyl chlorides to sulfinic acids, see 0-118. 

The question as to whether disulfides dissociate in solution into free radicals has been extensively studied. The sulfur-sulfur bonds in dialkyl and diaryl disulfides,13 154161 229 2 I0 in dialkyl tri- and tetrasulfidcs, 9 as well as in S8 undergo homolytic scission to free radicals under irradiation. 

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