Bromo sulfoxides, reaction

Rodriguez, N. Cuenca, A. Ramirez de Arellano, C. Medio-Simon, M. Asensio, G. Unprecedented Pd-catalyzed cross-coupling reaction of a-bromo sulfoxides with boronic adds. Org. Lett. 2003, 5,1705-1708. 

Bromomethyl ketones. Aldehydes can be converted into bromomethyl ketones by reaction with the anion of bromomethyl phenyl sulfoxide to form a p-hydroxy-a-bromo sulfoxide followed by pyrolysis in xylene or diglyme (equation I). ... 

Iron pentacarbonyl is an excellent reagent for deoxygenating dialkyl, diaryl, or heterocyclic sulfoxides to sulfides (Alper and Keung, 1970). The mechanism for this reaction is similar to that described for the N-oxide-Fe(CO)5 reaction. Moderate yields of thiobenzophenones were realized by reaction of diaryl sulfines with Fc2(CO)9 in benzene or Mn2(CO)io in heptane (Alper, 1975b). a-Bromo sulfoxides (XL) react with Mo(CO)g in 1,2-dimethoxyethane to... 

The addition proceeds most smoothly with highly functionalized (more polar) steroids as seen in examples by Bernstein and others. The polar reaction conditions pose solubility problems for lipophilic androstane, cholestane and pregnane derivatives. Improved yields can be obtained in some cases by using dimethyl sulfoxide or t-butanol " as solvents and by using sodium A-bromobenzenesulfonamide or l,3-dibromo-5,5-dimethyl hydantoin (available from Arapahoe Chemicals) as a source of positive bromine. The addition of bromo acetate and bromo formate to steroid olefins has been studied to a limited extent. ... 

When electron-withdrawing groups are attached to the double bond, the reaction is strongly inhibited and may fail completely. In such cases, the bromide anion, produced by the reaction of dimethyl sulfoxide with N-bromosuccinimide, competes with the dimethyl sulfoxide for the bromonium (or bromo carbonium) ion, an intermediate of the reaction. Thus, dibromide may accompany recovered alkene or any bromohydrin formed. Similarly, exogenous anions often compete with dimethyl sulfoxide for the cation. ... 

An unusual one-pot intramolecular sulfoxide alkylation-elimination reaction was found by Gibson et al. <2001SL712>. These authors found that treatment of 459 with potassium bis-trimethylsilylamide resulted in a ring closure to 460 in acceptable yield. Furthermore, Batori and Messmer found an effective method for preparation of [l,2,3]triazolo[l,5- ]pyrimidinium salts <1994JHC1041> oxidative cyclization of hydrazones 461 by 2,4,4,6-tetrabromo-2,5-cyclohexadienone gave rise to the quaternary salts 462. Under certain reaction conditions, the formation of 6-bromo-salts 462 (R6 = Br) was also experienced. As neither the starting compound nor the quaternary triazolopyridinium salt underwent bromination in this position, the authors assumed that this bromination process occurred on one of the intermediates in the course of the above-mentioned cyclization reaction. 

B. (3-Bromo-3,3-difluoropropyl)trimethylsilane. A 1-L, four-necked flask is equipped with a mechanical stirrer, thermometer, Claisen adapter, septum inlet, reflux condenser (the top of which is connected to a calcium chloride drying tube), and a solid addition funnel. The flask is charged with (1,3-dibromo-3,3-difluoropropyl)trimethylsilane (78.3 g, 0.25 mol), and anhydrous dimethyl sulfoxide (200 mL), and the solid addition funnel is charged with sodium borohydride (11.5 g, 0.30 mol) (Notes 7 and 8). The stirred solution is warmed to 80°C, and sodium borohydride is added at a rate sufficient to maintain a reaction temperature of 80-90°C (Note 9). Toward the end of the addition, an additional portion of dimethyl sulfoxide (200 mL) is added via syringe to lower the viscosity of the reaction mixture. After the addition is complete, the mixture is cooled in an ice-water bath, diluted with 100 mL of pentane, and cautiously quenched with 12 M hydrochloric acid until no further gas evolution occurs. The mixture is transferred to a separatory funnel and washed with three, 100-mL portions of 5% brine. The pentane extract is dried over calcium chloride and the solvent removed through a 15-cm Vigreux column. Further fractionation yields 41.5 g (72%) of 3-bromo-3,3-difluoropropyltrimethylsilane, bp 139-141 °C (Note 10). 

The 5-unsubstituted-l,2,3-triazol-4-ones (176, R = H) participate in electrophilic substitution reactions. Bromination in chloroform of anhydro-4-hydroxy-l,3-dimethyl-1,2,3-triazolium hydroxide (180) gave its 5-bromo derivative (182). The meso-ionic 3-aryl-1,2,3-triazol-4-ones (176, R = Me, R = Ar, R = H) gave 5-bromo derivatives (176, R = Me, R = Ar, R = Br) with bromine in acetic acid. Their reaction with sulphur monochloride gave the sulfide (189, X = S), and with thionyl chloride they gave the sulfoxide (189, X = SO). ... 

Preparation of the title compound by interaction of dimethyl sulfoxide and bromo-methane, sealed into a resin-coated glass bottle and heated at 65°C, led to an explosion after 120 h. The isolated salt thermally decomposes above 180°C to produce formaldehyde and a residue of methanesulfonic acid. In solution in dimethyl sulfoxide, the salt begins to decompose after several hours at 74—80°C (after exposure to light), the exothermic reaction accelerating with vigorous evolution of vapour (including formaldehyde and dimethyl sulfide), the residue of methanesulfonic acid finally attaining 132°C. Some white solid, probably poly-formaldehyde, is also produced. The explosion... 

The last results reported in this field are related to the 1,3-dipolar reactions of tert-butyl ( )-4,4-diethoxy-2-p-tolylsulfinylbut-2-enoate and (S5,Ss) and (R5,Ss) 5-ethoxy-3-p-tolylsulfinylfuranones (42a and 42b) with different nitrile oxides [ 167]. Acyclic sulfoxides react with benzonitrile, acetonitrile, and bromo-formonitrile oxides to yield isoxazoles resulting in desulfinylation from the adducts. Cyclic dipolarophiles afford bicyclic isoxazolines in their reactions with benzonitrile oxide. The reactivity of the double bond as a dipolarophile is strongly increased by the sulfinyl group. The regioselectivity of these reactions... 

The rate of fluorination using potassium fluoride alone follows the reverse order dimethyl sulfoxide > sulfolane > Af-methylpyrrolid-2-one > acetonitrile > 1,2-dimcthoxyethane. This can be explained by considering the different abilities of the solvents to stabilize the anionic (Meisenheimer) intermediate in the reaction. Therefore, the use of bromo(tetraphenyl)-A -phos-phane results not only in an increase in the concentration of fluoride in the media, but also helps to stabilize the anionic Meisenheimer intermediate when the solvent itself is too poor at realizing this function. 

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