Dimethyl sulfide reaction

The mechanism of the N03 radical reaction with DMDS is complex. The rate constants for the N03 reaction with CH3SCH3, CH3SH, and CH3SSCH3 (Table 8.17) are similar and much larger than that for the reaction with H2S. This suggests that by analogy with the dimethyl sulfide reaction, the initial step is addition to a sulfur atom to form an adduct that then reacts further ... 

Langer, S., B. T. McGovney, and B. J. Finlayson-Pitts, The Dimethyl Sulfide Reaction with Atomic Chlorine and Its Implications for the Budget of Methyl Chloride, Geophys. Res. Lett., 23, 1661-1664 (1996). 

Selective reduction of ot,a-dihalo ketones." Reduction of a,a-dihalo ketones can he effected without hydrogenolysis of the halo groups with either DIBAH or borane dimethyl sulfide. Reactions with the former reagent are generally faster but work-up can be complicated by gelatinous aluminum salts. In general, the yields are roughly comparable. 

Direct Kinetic and Mechanistic Study of the OH-Dimethyl Sulfide Reaction Under Atmospheric Conditions... 

The desired pyridylamine was obtained in 69 % overall yield by monomethylation of 2-(aminomethyl)pyridine following a literature procedure (Scheme 4.14). First amine 4.48 was converted into formamide 4.49, through reaction with the in situ prepared mixed anhydride of acetic acid and formic acid. Reduction of 4.49 with borane dimethyl sulfide complex produced diamine 4.50. This compound could be used successfully in the Mannich reaction with 4.39, affording crude 4.51 in 92 % yield (Scheme 4.15). Analogous to 4.44, 4.51 also coordinates to copper(II) in water, as indicated by a shift of the UV-absorption maximum from 296 nm to 308 nm. 

Diborane [19287-45-7] the first hydroborating agent studied, reacts sluggishly with olefins in the gas phase (14,15). In the presence of weak Lewis bases, eg, ethers and sulfides, it undergoes rapid reaction at room temperature or even below 0°C (16—18). The catalytic effect of these compounds on the hydroboration reaction is attributed to the formation of monomeric borane complexes from the borane dimer, eg, borane-tetrahydrofuran [14044-65-6] (1) or borane—dimethyl sulfide [13292-87-0] (2) (19—21). Stronger complexes formed by amines react with olefins at elevated temperatures (22—24). 

Retardation of the reaction rate by the addition of dimethyl sulfide is in accord with this mechanism. Borane—amine complexes and the dibromoborane—dimethyl sulfide complex react similarly (43). Dimeric diaLkylboranes initially dissociate (at rate to the monomers subsequentiy reacting with an olefin at rate (44). For highly reactive olefins > k - (recombination) and the reaction is first-order in the dimer. For slowly reacting olefins k - > and the reaction shows 0.5 order in the dimer. 

Monohalogenoboranes are conveniendy prepared from borane—dimethyl sulfide and boron trihahdes (BX where X = Cl, Br, I) by redistribution reaction, eg, for monochloroborane—dimethyl sulfide [63348-81-2] (9) (81—83). Other methods are also known (84—87). 

Usually, organoboranes are sensitive to oxygen. Simple trialkylboranes are spontaneously flammable in contact with air. Nevertheless, under carefully controlled conditions the reaction of organoboranes with oxygen can be used for the preparation of alcohols or alkyl hydroperoxides (228,229). Aldehydes are produced by oxidation of primary alkylboranes with pyridinium chi orochrom ate (188). Chromic acid at pH < 3 transforms secondary alkyl and cycloalkylboranes into ketones pyridinium chi orochrom ate can also be used (230,231). A convenient procedure for the direct conversion of terminal alkenes into carboxyUc acids employs hydroboration with dibromoborane—dimethyl sulfide and oxidation of the intermediate alkyldibromoborane with chromium trioxide in 90% aqueous acetic acid (232,233). 

Through reaction with sulfide or elemental sulfur at 215°C, lignosulfonates can also be used in the commercial production of dimethyl sulfide and methyl mercaptan (77). Dimethyl sulfide produced in the reaction is further oxidized to dimethyl sulfoxide (DMSO), a useful industrial solvent (see Sulfoxides). 

Thermal Stability. Dimethyl sulfoxide decomposes slowly at 189°C to a mixture of products that includes methanethiol, formaldehyde, water, bis(methylthio)methane, dimethyl disulfide, dimethyl sulfone, and dimethyl sulfide. The decomposition is accelerated by acids, glycols, or amides (30). This product mixture suggests a sequence in which DMSO initially undergoes a Pummerer reaction to give (methylthio)methano1, which is labile and reacts according to equations 1—3. Disproportionation (eq. 4) also occurs to a small extent ... 

When DMSO is mixed with concentrated hydrochloric acid, protonated DMSO is in equiUbtium with the chlorodimethylsiilfonium ion. Pummerer reactions and subsequent reaction of the initial products give a complex mixture of products including formaldehyde, bis(methylthio)methane, methanethiol, dimethyl disulfide, dimethyl sulfide, and others. 

Processes involving oxygen and nitrogen oxides as catalysts have been operated commercially using either vapor- or Hquid-phase reactors. The vapor-phase reactors require particularly close control because of the wide explosive limit of dimethyl sulfide in oxygen (1—83.5 vol %) plants in operation use Hquid-phase reactions. Figure 2 is a schematic diagram for the Hquid-phase process. The product stream from the reactor is neutralized with aqueous caustic and is vacuum-evaporated, and the DMSO is dried in a distillation column to obtain the product. 

Atmosphere—Water Interaction. Although water is a very minor component of the atmosphere, less than 10 vol % of the atmosphere consisting of water, many important reactions occur ki the water droplets of cloud, fog, and rain. The atmosphere is an oxic environment ki its water phase, gigantic quantities of reductants, such as organic substances, Fe(II), SO2, CH SCH (dimethyl sulfide), and nitrogen oxides, are oxidized by oxidants such as oxygen, OH radicals, H2O2, and Fe(III). 

Certain base adducts of borane, such as triethylamine borane [1722-26-5] (C2H )2N BH, dimethyl sulfide borane [13292-87-OJ, (CH2)2S BH, and tetrahydrofuran borane [14044-65-6] C HgO BH, are more easily and safely handled than B2H and are commercially available. These compounds find wide use as reducing agents and in hydroboration reactions (57). A wide variety of borane reducing agents and hydroborating agents is available from Aldrich Chemical Co., Milwaukee, Wisconsin. Base displacement reactions can be used to convert one adduct to another. The relative stabiUties of BH adducts as a function of Group 15 and 16 donor atoms are P > N and S > O. This order has sparked controversy because the trend opposes the normal order estabUshed by BF. In the case of anionic nucleophiles, base displacement leads to ionic hydroborate adducts (eqs. 20,21). 

CF3CO2H, PhSCH3, 25°, 3 h. ° The use of dimethyl sulfide or anisole as a cation scavenger was not as effective because of side reactions. Benzyl ethers of serine and threonine were slowly cleaved (30% in 3 h complete cleavage in 30 h). The use of pentamethylbenzene had been shown to increase the rate of deprotection of 0-Bn-tyrosine. ... 

The cyclobutadiene analogue diazadiboretidine reacts with hexafluoroacetone to give a nng expansion product [776] (equation 90) 6-(3-Fluoroaryl)decaborane is formed by alkylation of decaboranyl anion and separation of the two isomers (5- and 6-benzyl) formed by reaction with dimethyl sulfide [777] (equation 91). 

Write an equation for the Lewis acid-Lewis base reaction between boron trifluoride and dimethyl sulfide [(0)3)25]. Use curved arrows to track the flow of electrons and show formal charges if present. 

Reduction of 3,5,5-tris-aryl-2(5// )-furanones 115 (R, R, R = aryl) with dimethyl sulfide-borane led to the formation of the 2,5-dihydrofurans 116 in high yields. However, in the case of 3,4-diaryl-2(5//)-furanones 115 (R, R = aryl R = H or r = H R, R = aryl), the reduction led to a complicated mixture of products of which only the diarylfurans 117 could be characterized (Scheme 36) (88S68). It was concluded that the smooth conversion of the tris-aryl-2(5//)-furanones to the corresponding furan derivatives with the dimethylsulfide-borane complex in high yields could be due to the presence of bulky aryl substituents which prevent addition reaction across the double bond (88S68). 

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]. 

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