Sulfur bridge

In the synthesis of commercial sulfur-heterocycles two interesting reactions are used (i) diphenylamines may be connected by a sulfur bridge in the orfho-positions (ii) the amino grouping of sulfonamides undergoes condensation reactions with neighboring imino- and amide groups. 

Semi-EV cures represent a compromise between conventional and EV cures. Although semi-EV cures do yield polysulftde cross-links, they tend to minimize formation of kiefficient moieties such as sulfur bridging with itself, accelerator-terminated sulfur linkages, etc. This cleaner usage of sulfur is the reason for thek compromise properties between conventional and EV cures. 

Pentichlor (bithionol, thiobis-(4,6-dichlorophenol)) [97-18-7] is a bisphenol having a sulfur bridge rather than a methylene bridge. Like... 

An interesting bridged-sulfur compound, which is a natural constituent of Iranian oil, has been synthesized 478) by the reaction of a bicyclic bis-enamine with sulfur dichloride and subsequent Wolff-Kishner reduction of an initial sulfur-bridged diketone. Sulfur dichloride has also been added to a number of vinylogous amides 479). 

In the oxidative Eschenmoser sulfide contraction (Scheme 11), thioamide 59 is oxidized by benzoyl peroxide to give either a symmetrical disulfide or the O-benzoate of the thiolactam-S-oxide. In any event, the once-nucleophilic thioamide sulfur atom is now forced to adopt the role of electrophile a reactivity umpolung has, in effect, been achieved.13 The nucleophilic enamide 65 attacks the sulfur atom leading to the formation of sulfur-bridged intermediate 66. The action of a phosphine or a phosphite thiophile on the putative episulfide then gives vinylogous amidine 67. 

The parent thionine system 1 up to now has not been prepared probably because the C-S bond in valence isomeric forms is too weak giving rise to facile rearrangement or decomposition. The obvious synthetic route, photochemical transformation of cyclooctatetraenccpisulfide 2 (9-thiabicyclo[6.1.0]nona-2,4,6-triene), does not lead to 1, but intriguingly to another valence isomer, the sulfur-bridged homotropylidene system 3.20... 

Cluster 2 appears to be unique among Fe-S-containing proteins whose structures have so far been determined, emd it has been termed the hybrid cluster (6) because of its diverse chemical nature. Figure 14 is a schematic drawing of the cluster as interpreted from the final electron density synthesis and the structure refinement. The cluster contains both oxygen and sulfur bridges, and X represents a site whose precise nature has not been determined, but which may contain a partially occupied and/or disordered substrate molecule (see Section III,B,3,b). The environments of the four iron atoms can be described as follows. 

The 6-function makes sure that if two segments and 2 meet on the huge network chain they can form a permanent constraint R( i) = R( 2)- Hence, this process will produce a network junction of functionality/n = 4, usually realized as sulfur bridges in technical elastomers like, for example, tire treads. 

In the same year, Evans and coworkers reported the electrochemical reduction of protons to H2 catalyzed by the sulfur-bridged dinuclear iron complex 25 as a hydrogenase mimic in which acetic acid was used as a proton source [201]. The proposed mechanism for this reaction is shown in Scheme 60. The reduction of 25 readily affords 25 via a one electron reduction product 25. Protonation... 

Picolylphenylketone S-benzyldithiocarbazate, 48, yielded paramagnetic [ Ni(48-H)A 2] (A = Cl, Br) and diamagnetic [Ni(48-H)I] [207]. All three compounds are non-electrolytes and the iodo complex is planar while the other two complexes involve sulfur bridging atoms and five-coordinate nickel(II) centers. All three complexes can be converted to monomeric, octahedral complexes by addition of pyridine, 2-picoline or quinoline. 

Figure 49 Cyclic sulfur-bridged octanuclear complexes [M2 Pd[Co(aet)3]2 2] ...

Reaction of a dihalide with sodium sulfide is perhaps the most direct way of creating a sulfur bridge it has, for example, been used to synthesize the thiophene (8) from a dichloro-substituted precursor (9).9... 

Muehlstaedt and co-workers have shown that similar sulfur bridges may be inserted into many other acyclic compounds typical products include benzoxathiins (23) and thiazolinones (24).29... 

Af,AT-Thiobisphthalimide (30) and l,l -thiobisimidazole (31) are two reagents of lesser reactivity they are particularly effective in building sulfur bridges between nitrogen or oxygen atoms. The thiadiazoline (32), for example, is easily prepared from 30 and JV,A/ -dimethyl-l,2-diaminoethane.1,34... 

Dihydroxy derivative 277 when treated with sulfur monochloride provided in 65% yield sulfur-bridged diketopiperazine structure 298 (Scheme 73) (77JOC948). 

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