Sulfoxide, dimethyl mechanism

The mechanism proposed for the reduction of thietane 1-oxide by hydrogen sulfide is complex the order of reactivity is ethyl methyl sulfoxide > thiolane 1-oxide > diethyl sulfoxide > dimethyl sulfoxide > thietane l-oxide. ... 

Benzyl bromide is converted into benzaldehyde by heating in dimethyl sulfoxide. Propose a structure for the intermediate, and show the mechanisms of the two steps in the reaction. 

Starting from l.l-dichloro-7b-ethoxy-2-methyl-1,1 a,2,7-tetrahydrobenzo[/)]cyclopropa[prepared from the corresponding benzothiopyran by addition of dichlorocarbene, the three 1-benzothiepins 6a-c are formed upon treatment with strong bases, i.e. sodium methoxide or ethoxide in dimethyl sulfoxide.73 The optimal yield of each 1-benzo-thiepin compound depends on the molar equivalents of base, as follows from different ring-opening mechanisms. 

In a 250-ml., three-necked, round-bottomed flask equipped with a mechanical stirrer, a gas inlet, and a stopper are placed 540 mg. (0.00346 mole) of a mixture of cis- and dimethyl sulfoxide (Note 3). While a slight positive pressure of argon is maintained... 

Ce4+ is a versatile one-electron oxidizing agent (E° = - 1.71 eV in HC10466 capable of oxidizing sulfoxides. Rao and coworkers66 have described the oxidation of dimethyl sulfoxide to dimethyl sulfone by Ce4+ cation in perchloric acid and proposed a SET mechanism. In the first step DMSO rapidly replaces a molecule of water in the coordination sphere of the metal (Ce v has a coordination number of 8). An intramolecular electron transfer leads to the production of a cation which is subsequently converted into sulfone by reaction with water. The formation of radicals was confirmed by polymerization of acrylonitrile added to the medium. We have written a plausible mechanism for the process (Scheme 8), but there is no compelling experimental data concerning the inner versus outer sphere character of the reaction between HzO and the radical cation of DMSO. 

Novi and coworkers124 have shown that the reaction of 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene with sodium benzenethiolate in dimethyl sulfoxide yields a mixture of substitution, cyclization and reduction products when subjected at room temperature to photostimulation by a sunlamp. These authors proposed a double chain mechanism (Scheme 17) to explain the observed products. This mechanism is supported by a set of carefully designed experiments125. The addition of PhSH, a good hydrogen atom donor, increases the percent of reduction products. When the substitution process can effectively compete with the two other processes, the increase in the relative yield of substitution (e.g., with five molar equivalents of benzenethiolate) parallels the decrease in those of both cyclization and reduction products. This suggests a common intermediate leading to the three different products. This intermediate could either be the radical anion formed by electron transfer to 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene or the a radical formed... 

B. Benzocyclopropene. A dry, three-necked, round-bottomed flask fitted with a sealed mechanical stirrer, a reflux condenser, and a pressure-equalizing dropping funnel is flushed with nitrogen. To the flask is added 35.0 g (0.312 mole) of potassium ferf-butoxide (Note 1), followed by 200 ml. of dimethyl sulfoxide (Note 5). The stirred mixture is cooled to 15-20° (Note 6) with an ice bath and 24.5 g. 

It was shown in the same article that the decarboxylation could also be performed by conventional heating but then copper cyanide was required and a mixture of saturated and imsaturated 2-pyridones 65 and 66 was obtained in a ratio of 1 10 (Fig. 10). A tentative mechanism was suggested for the reagent-free MAOS method where the carbonyl in the 2-pyridone ring is supposed to assist in the decarboxylation yielding an yUde 67 (Fig. 11). The decarboxylated bicyclic 2-pyridone 68 is thereafter obtained after protonation by the solvent. In agreement with the mechanistic suggestion, it was shown that a selective deuteration occurred when deuterated dimethyl sulfoxide (DMSO-de) was used as solvent. 

A. Succinimide silver salt (Note 1). A 3-1., two-necked, round-bottomed flask equipped with a mechanical stirrer and a pressureequalizing dropping funnel is charged with a solution of 28.9 g. (0.292 mole) of succinimide (Note 2) in 1.2 1. of absolute ethanol (Note 3). A solution of 48.58 g. (0.286 mole) of silver nitrate in 200 ml. of dimethyl sulfoxide (Note 4) is added in one portion. The resulting solution is stirred as 700 ml. (0.280 mole) of 0.4 M... 

Absorption rates of carbon dioxide were measured in organic solutions of glycidyl methacrylate at 101.3 kPa to obtain the reaction kinetics between carbon dioxide and glycidyl methacrylate using tricaprylylmethylammonium chloride(Aliquat 336) as catalysts. The reaction rate constants were estimated by the mass transfer mechanism accompanied by the pseudo-first-order fast reaction. An empirical correlation between the reaction rate constants and the solubility parameters of solvents, such as toluene, A-methyl-2-pirrolidinone, and dimethyl sulfoxide was presented. 

Selenophene was also obtained as the main component in the reaction between vinylacetylene and the selenium dianion, generated from elemental selenium (Se8), in dimethyl sulfoxide-potassium-water at 100-120°C.5° Bis-y,y-dimethylallenyl selenide (18) is converted by spontaneous cyclo-aromatization to 3-isopropenyl-4-isopropylselenophene (19).51 Two mechanisms are shown in Scheme 3. 

Some efforts have been taken to obtain the electrochemical response of Hb at solid electrode surfaces. Fan s electrochemical researches revealed that the electron-transfer reactivity of Hb could be greatly enhanced, simply by treating it with an organic solvent, dimethyl sulfoxide (DMSO) [115], Hb can also achieve its direct electron transfer in /V,/V-dimcthy I form am idc (DMF) film, as Xu [116] reported. These, therefore, suggested that there are many different factors that regulate electron-transfer reactivity of proteins. It also pointed out the complicated and precise regulation mechanisms of proteins in vivo. 

The potassium salt of dimethyl sulfoxide can also be prepared in the following manner. In a 1-1. three-necked flask equipped with an all-glass mechanical stirrer, a 125-ml. dropping funnel containing 90 ml. of dry dimethyl sulfoxide (Note 1), and a Claisen distillation head and condenser is placed 425 ml. of dry 2-butyl alcohol (Note 1). The system is flushed with dry... 

The kinetics and mechanism of ligand substitution reactions of square-planar platinum(II) dimethyl sulfoxide complexes have been exhaustively studied (173), and these workers conclude that the cis and trans influences and the trans effects of Me2SO and ethylene are similar in magnitude whereas the cis effect of Me2SO is about 100 times as large as that of ethylene. The results for reaction (5), where the stability constants, Kt, are reported to be 1.5 x 108 (L = S-Me2SO) and 4.5 x 108 (L = ethylene) corroborate this analogy (213). 

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