Dimethyl sulfide structure

Compare this step to the mechanisms we saw in the previous section syn dihydroxy-lation), and you should see striking similarities. The initial product (shown above) is called a molozonide, and it subsequently undergoes further rearrangements, before ultimately giving the product upon treatment with dimethyl sulfide (DMS). The structure of DMS is ... 

Todd JD, Rogers R, Li YG, Wexler M, Bond PL, Sun L, Curson ARJ, Malin G, Steinke M, Johnston AWB (2007) Structural and regulatory genes required to make the gas dimethyl sulfide in bacteria. Science 315 666-669... 

FIGURE 4. Transition structures for the oxidation of tiimethylamine (a), trimethylphosphine (b) and dimethyl sulfide (c,d) with peroxynitrous acid optimized at the B3LYP/6-311G, MP2(full)/6-31G (in parentheses) and QCISD/6-31G (in brackets) levels... 

FIGURE 31. Transition structure for the HO—OH oxidation of dimethyl sulfide with three water molecules fully optimized at the B3LYP/6-31++G(d,p) level. The reaction barrier (A ) was calculated at the MP4//B3LYP/6-31-I— -G(d,p) level with respect to the reactant cluster... 

FIGURE 33. Transition structures [B3LYP/6-31+G(d,p)] for the oxidation of dimethyl sulfide with (a) monomeric CH3O—OH and (b) dimeric methyl hydroperoxide... 

In an analogous manner, nitroalkenes can be utilized as the electrophile in a tandem coupling-cyclization process (Eq. 2.18). Addition of a stabilized sulfonium ylide such as 209, to a variety of nitroalkenes provides an intermediate nitronic acid, which upon displacement of dimethyl sulfide provides a mixture of the corresponding nitrocyclopropane (XL) and cyclic nitronate (XLI). The ratio of products is highly dependent on the structure of the nitroalkene. For example, without a substituent on the a-position of the nitroalkene (R = H), only the... 

Under similar conditions, diphenyl sulfide, C6H5-S-C6H5, was found to be unreactive, indicating that the reactions listed in Table XII take place inside the pore structure, which is not accessible to bulky molecules such as diphenyl sulfide. The selectivity to sulfoxides (Table XII) is the result of a competition between sulfides and sulfoxides for the catalytic site dimethyl sulfide competes effectively, and the selectivity to sulfoxide is 97% with only 3% sulfone produced. The other reactant molecules give larger amounts of sulfones. However the reaction of dimethyl sulfide was carried out at 298 K, whereas the other sulfides reacted at the reflux temperature of acetone the temperature difference may explain part of the differences shown in Table XII. 

However, this level of uniformity is not expected of all nucleophiles and substrates. An extreme example of variation in ApAR is provided by comparison of chloride and dimethyl sulfide as nucleophiles reacting, respectively, with the p-methoxybenzyl cation and the structurally very different electrophile, the di-trifluoromethyl quinone methide 57.220 In the case of the p-methoxybenzyl cation the addition of Me2S is more favorable than addition of chloride ion by a factor of 107-fold for the quinone methide it is 100 times less favorable. Toteva and Richard attribute the difference to the large and unfavorable steric and polar interactions between the positively charged... 

The crystalline 1,2,4-trioxolane derivative 123 is exceptionally stable. Its structure was determined by X-ray crystallography. Its reduction with dimethyl sulfide and intramolecular cyclization generates an oxonitrile with a six-membered ring even simpler one-pot synthesis without isolating the ozonide gives a >90% yield. 

The best reagent for this is borane, BH3. Borane is, in feet, a gas with the structure B2Hg, but it can be tamed1 as a liquid by complexing it with ether (Et20), THF, or dimethyl sulfide (DMS, Me2S). 

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