Dimethyl -sulfonium bromide

High-quality albuterol was obtained in good yield from this process. However, several environmental disadvantages were identified. The preparation of the keto aldehyde hydrate (KAH) generated dimethyl sulfide, methyl bromide, and trimethyl-sulfonium bromide (this compound sublimed in the condenser). In addition, reduction of the Schiff base with dimethylsulfide borane, although very attractive in simplifying... 

OXIRANES (Dimethylamino)phenyl-oxosulfonium methylide. Dimethyl-sulfonium methylide. (Dimethyl sulfoxide, derived reagent (b)). Methylene bromide-Lithium. Methylphenyl-N-p-tohienesulfonylsulfoximine. 

A 50%-NaH-oil dispersion added at 8-9° under N2 to a suspension of (3-phenyl-2-propynyl)dimethylsulfonium bromide and p-bromobenzaldehyde in tetrahydro-furan, stirring continued 0.5 hr. at 8-10° then 5 hrs. at room temp. dimethyl-sulfonium 2-oxo-3-phenyl-4-p-bromophenyl-3-butenylid. Y 75%. F. e. s. A. Terada and Y. Kishida, Chem. Pharm. Bull. 18, 490 (1970) reactions of the products cf. ibid. 18, 505. 

CgHg)2Te Thiophene Methylene blue Dimethylpropynyl-sulfonium bromide Sulfoxides, Dimethyl sulfoxide Thiirane 1-oxide (CHg)2N S-N(CHg)2 (Bisdimethy lamino-sulfane)... 

Dimethy Ipropyny l-sulfonium bromide Sulfoxides, Dimethyl sulfoxide Thiirane 1-oxide Tosy Imethylisocyanide Dialkoxysulfuranes Me,N-S-NMe, (Bisdimethylamino-sulfane) Thioacetamide Benzothiazole-2-thione, 3-methyl-Thiazolium salts - bromide, N-lauryl-Et,NCSSH Thiourea, Thioureas 1 -A cety l-2-thiourea Thiourea dioxide Selenourea Thiocyanates ArN C S (NCS),... 

Thiophene Methylene blue (C,H,S),N DimethylpropynyU sulfonium bromide Sulfoxidesy Dimethyl sulfoxide Thiirane 1-oxide Tosy Im ethy lisocyanide Dialkoxy sulfuranes (CHshN-S-N(CHsh (Bisdimethylamino-sulfane) Thioacetamide Thiazolium salt Thiazolium bromide, N-lauryl-... 

To circumvent these difficulties, Horton and Tucker 196) synthesized a water-soluble reagent, dimethyl (2-hydroxy-5-nitrobenzyl)-sulfonium bromide (132) which, like HNB-Br, can react selectively with tryptophan residues of proteins in aqueous solution, but in the absence of organic solvent. 

Barman, T. E., and W. Bagshaw Modification of the Tryptophan Residues of Bovine a-Lactalbumin with 2-Hydroxy-5-nitrobenzyl Bromide and with Dimethyl (2-hydroxy-5-nitrobenzyl) Sulfonium Bromide. II. Effect on the Specific Protein Activity. Biochim. Biophys. Acta. 278, 491-500 (1972). 

Heinrich, C. P., S. Adam, and W. Arnold The Reaction of Dimethyl (2-Hydroxy-5-Nitrobenzyl) Sulfonium Bromide with N-Acetyl-L-Tryptophan Amide. FEBS Lett. 33, 181-183 (1973). 

JoRKASKY, D. K., S. E. Pearson, and C. L. Borders, Jr. Reversible Inactivation of Avian Lysozymes by Dimethyl (2-Hydroxy-5-Nitrobenzyl)-Sulfonium Bromide. Biochem. Biophys. Res. Commun. 52, 987-991 (1973). 

Thioglycosides can be activated for gfycosylation reactions with sulfur electrophiles, e.g., with dimethyl(methylthio)sulfonium triflate or with methanesulfenyi bromide and silver(l +) to form reactive sulfonium intermediates (F. Dasgupta, 1988). 

It is well known that aziridination with allylic ylides is difficult, due to the low reactivity of imines - relative to carbonyl compounds - towards ylide attack, although imines do react with highly reactive sulfur ylides such as Me2S+-CH2-. Dai and coworkers found aziridination with allylic ylides to be possible when the activated imines 22 were treated with allylic sulfonium salts 23 under phase-transfer conditions (Scheme 2.8) [15]. Although the stereoselectivities of the reaction were low, this was the first example of efficient preparation of vinylaziridines by an ylide route. Similar results were obtained with use of arsonium or telluronium salts [16]. The stereoselectivity of aziridination was improved by use of imines activated by a phosphinoyl group [17]. The same group also reported a catalytic sulfonium ylide-mediated aziridination to produce (2-phenylvinyl)aziridines, by treatment of arylsulfonylimines with cinnamyl bromide in the presence of solid K2C03 and catalytic dimethyl sulfide in MeCN [18]. Recently, the synthesis of 3-alkyl-2-vinyl-aziridines by extension of Dai s work was reported [19]. 

The solvent dependence of the reaction rate is also consistent with this mechanistic scheme. Comparison of the rate constants for isomerizations of PCMT in chloroform and in nitrobenzene shows a small (ca. 40%) rate enhancement in the latter solvent. Simple electrostatic theory predicts that nucleophilic substitutions in which neutral reactants are converted to ionic products should be accelerated in polar solvents (23), so that a rate increase in nitrobenzene is to be expected. In fact, this effect is often very small (24). For example, Parker and co-workers (25) report that the S 2 reaction of methyl bromide and dimethyl sulfide is accelerated by only 50% on changing the solvent from 88% (w/w) methanol-water to N,N-dimethylacetamide (DMAc) at low ionic strength this is a far greater change in solvent properties than that investigated in the present work. Thus a small, positive dependence of reaction rate on solvent polarity is implicit in the sulfonium ion mechanism. 

Electrophilic attack on the sulfur atom of thiiranes by alkyl halides does not give thiiranium salts but rather products derived from attack of the halide ion on the intermediate cyclic salt (B-81MI50602). Treatment of ds-2,3-dimethyl thiirane with methyl iodide yields cis-2-butene by two possible mechanisms (Scheme 31). A stereoselective isomerization of alkenes is accomplished by conversion to a thiirane of opposite stereochemistry followed by desulfurization by methyl iodide (75TL2709). Treatment of thiiranes with alkyl chlorides and bromides gives 2-chloro- or 2-bromo-ethyl sulfides (Scheme 32). Intramolecular alkylation of the sulfur atom of a thiirane may occur if the geometry is favorable the intermediate sulfonium ions are unstable to nucleophilic attack and rearrangement may occur (Scheme 33). 

A. Dimethylprop-2-ynylsulfonium Bromide. A mixture of 6.2 g. (0.1 mole) of dimethyl sulfide (Note 1), 11.9 g. (0.1 mole) of 3-bromopropyne (Note 2), and 10 ml. of acetonitrile (Note 3) is stirred magnetically for 20 hours (Note 4) in a darkened 100-mi. round-bottomed flask (Note 6) fitted with a calcium chloride drying tube. The resulting white, crystalline mass is filtered with suction and washed with three 50-ml. portions of dry ether (Note 6) to give 16.4 g. (90%) of the sulfonium salt, m.p. 105-106°. This material may be used in the next step without purification but, if desired, it may be recrystallized from ethanol-ether (Note 7) with minimal loss to give a product melting at 109-110°. 

This evidence is based on IR-spectroscopic measurements on the copper-ylide complex prepared by two independent routes. First, sulfonium salt 417 was made by alkylation of dimethyl siflfide 416 with bromide 415. The... 

Dimethyl sulfoxide-derived reagent (b). DImethylsulfonlum methyllde, (CH S CHj. This heat-labile reagent is prepared in solution by dehydrohalogenation of trimethyl-sulfonium iodide, bromide, or perchlorate. It is an exceedingly selective methylene-... 

A modification of this general procedure was used in the synthesis of (prop-2-enylidene)cyclo-propane (allylidenecyclopropane, 12).Allyl bromide was first alkylated in 81 -90% yield with l-lithio-l-(phenylsulfanyl)cyclopropane (10) in the presence of copper(I) iodide or cop-per(I) iodide-dimethyl sulfide. The adduct was then methylated with methyl fluorosulfonate or with dimethyl sulfate, and the sulfonium salt cleaved with powdered potassium hydroxide in dimethyl sulfoxide, to give the product in 50-70% overall yield for the second step. 

When iVj-acyl-tryptophans are exposed to strong acid, the indolium cation is trapped by cyclisation involving the side-chain nitrogen. Comparable tricycles result from phenylselenylation of protected tryptophan or reaction with 4-methyl-l,2,4-triazoline-3,5-dione, ° or dimethyl(succinimido)sulfonium chloride (a CH2SMe group ends up at the indole C-3)." If M-bromosuccinimide is employed, the initially formed 3-bromo-tricycle loses hydrogen bromide to produce an aromatic indole. ... 

Similarly, reaction of a thioglycoside with a hydroxylic compound in the presence of an excess of a tetraalkylammonium bromide and the thiophilic promoter dimethyl(methylthio)sulfonium triflate (DMTST) proceeds with high stereoselectivity.131-133... 

Bohme and Krause312 describe the preparation of various dialkylphenacylsulfonium salts, e.g., dimethylphenacylsulfonium bromide co-Bromoacetophenone (9 g) is dissolved in a mixture of water (1 volume) and acetone (20 volumes), and dimethyl sulfide (3 g) is added. After about 0.5 h the sulfonium salt separates as long, colorless needles, m.p. 145° (10.2 g, 85 %). 

This synthesis of sulfenyl chlorides can also be used in the aliphatic series although here the limitation applies that most alkylsulfur halides are too unstable to be isolated from solution. In general, and also in the aromatic series, sulfenyl chlorides are easier to prepare than the bromides, whilst the iodides are known only in a few cases and the fluorides not at all. As an example, Schneider,665 chlorinating methanethiol in anhydrous carbon tetrachloride at —15°, obtained dimethyl disulfide dichloride [chloro(methyl)(methylthio)-sulfonium chloride] which passed into methanesulfenyl chloride when allowed to warm slowly to room temperature ... 

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