Sulfuryl bromide bromination

One Te-C bond in a diorgano tellurium can be cleaved by alkali metals, organic lithium compounds, sodium hydroxide, lithium aluminum hydride, sodium borohydride, Grignard reagents, tributyltin hydride, sulfuric acid, sodium sulfide, sulfuryl chloride, hydrogen bromide, bromine, or iodine. The Te-C bond can also be broken thermally or through photostimulation. 

The decomposition of sulfuryl chloride is accelerated by light and catalyzed by aluminum chloride and charcoal. Many of the reactions of sulfuryl chloride are explainable on the basis of its dissociation products. Sulfuryl chloride reacts with sulfur at 200°C or at ambient temperature in the presence of aluminum chloride producing sulfur monochloride. It hberates bromine or iodine from bromides or iodides. Sulfuryl chloride does not mix readily with water and hydrolyzes rather slowly. 

Oxidation of sulfur dioxide in aqueous solution, as in clouds, can be catalyzed synergistically by iron and manganese (225). Ammonia can be used to scmb sulfur dioxide from gas streams in the presence of air. The product is largely ammonium sulfate formed by oxidation in the absence of any catalyst (226). The oxidation of SO2 catalyzed by nitrogen oxides was important in the eady processes for manufacture of sulfuric acid (qv). Sulfur dioxide reacts with chlorine or bromine forming sulfuryl chloride or bromide [507-16 ]. 

Diphenyl diselenide has been prepared by disproportionation of phenyl selenocyanate in the presence of potassium hydroxide" or ammonia/ and by air oxidation of benzeneselenol. The preparation of benzeneselenol is described in an earlier volume in this series/ In the present procedure phenylselenomagnesium bromide formed from phenylmagnesium bromide and selenium is oxidized directly to diphenyl diselenide with bromine/ Thus the liberation of the malodorous and toxic hydrogen selenide and benzeneselenol is avoided. Benzeneselenenyl chloride has been prepared by thermal elimination of ethyl chloride from ethyl phenyl selenide di-chloride/ by thermal elimination of chlorine from phenylselenium trichloride," and by chlorinolysis of diphenyl diselenide with either sulfuryl chloride " or chlorine. " ... 

Reactions with chlorine or bromine yield sulfuryl chloride, SO2CI2, or sul-furyl bromide, S02Br2 ... 

Pyridinium bromide perbromide efficiently brominates pyrroles already substituted by electron-withdrawing substituents and also gives a high yield of 3-bromoindole in its reaction with indole. In conjunction with sulfuryl chloride, it has been used in the synthesis of 3-bromo-2-chloro-, 2-bromo-3-chloro- and 2,3-dibromo-indole (81SC253). 3-Methylindole reacts with A-bromosuccinimide in acetic acid to give the 2-bromo derivative which reacts further with an excess of A-bromosuccinimide to yield 2,6-dibromo-3-methylindole (B-70MI30500, 72HC(25-2)127) whilst in aqueous or alcoholic media, 3-bromo-3-methylox-indole is produced (cf. Scheme 15). All of these reactions proceed via the 3-bromo-3A-indolium cation, but the course of the reaction depends not only upon the orientation or... 

Further studies of electrophilic substitution using the 2,3-dihydrothiazolo analogue (320) show that regioselective bromination can be effected in the 7-position (347) at low temperature. Chlorination with sulfuryl chloride, however, occurs exclusively in the 5-position. The 5-chloro derivative (348) can be further nitrated in the 7-position. By analogy, bromination of quinoline analogues (349) occurs in the azine ring, in the 5-position. The [3,2-a]pyrimidine analogue (350 R=H) similarly yields the 7-bromide. The activation by... 

There are various ways to generate and synthesize selenium electrophiles and some of these compounds are commercially available. The addition reaction can also be dependent on the counterion X of these reagents and several protocols have been developed to exchange the counterions. The most commonly used electrophile is the phenylselenyl electrophile and compounds like phenylselenenyl chloride 6 and phenylselenenyl bromide 7 are commercially available. They can also be easily generated from diphenyl diselenide 8 by treatment with sulfuryl chloride or elementary chlorine or bromine, respectively. Diselenides in general are very versatile precursors for selenium electrophiles. For addition reactions using external nucleophiles the use of selenenyl halides can lead to complications, because chloride or bromide ions can also act as nucleophiles and lead to undesired side-products. An... 

Attempts to brominate benzo[h]quinolizinium bromide (3) with liquid bromine gave an addition product (Section II,B). Bromination with bromine and aluminum bromide in dimethylformamide gave 1 l-bromobenzo[b]-quinolizinium bromide (137).71 Sulfuryl chloride and aluminum chloride under similar reaction conditions gave the chlorobenzquinolizinone (139), presumably from the 6,11-dichlorobenzquinolizinium salt (138).71 Without... 

When the sulfone has an a-halo substituent, formation of the carbanion is often accompanied by loss of the SO2 moiety via the so-called Ramberg-Backlund reaction.335 An illustration is the conversion of 1-bromo-ethyl ethyl sulfone (327) to 2-butene.336 Initial reaction with potassium hydroxide generated the sulfone carbanion (328), which displaced bromide intramolecularly to give an episulfone (329). Under the reaction conditions, 329 lost sulfur dioxide (SO2) to give the alkene. Meyers introduced a modification of this reaction in which the sulfone was converted directly to the alkene without isolating the a-halosulfone, using KOH in CCl4.337,338 Sulfuryl chloride and bromine can also be used.338... 

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