Sulfur compounds, vinylic

Organocopper reagents, 207 Organovanadium reagents, 219 By desilylation of vinylsilanes Tetrabutylammonium fluoride, 286 By desulfurization of vinyl sulfides and related sulfur compounds Sodium dithionite, 281 Elimination reactions By dehalogenation Dichlorobis(cyclopentadienyl)-titanium, 102... 

Otsu, T. Vinyl polymerization. XIX. The preparation of block and graft copolymers using some sulfur compounds. J. Polymer Sci. 26,236 (1957). 

Among the very few reported cases of radiation induced isomerizations in sulfur compounds is that of JV-alkyl-iV-vinyl-sulfonamides. The products of the reaction are 2-sulfonyl vinyl amines, viz. 

The nucleophilicity of sulfur and its ability to stabilize a-carbanions provide sulfur compounds with unique opportunities for sigmatropic processes consecutive rearrangements are no exception. The formation of salt (140) via Sn2 alkylation of ( )-2-butenyl bromide (139) followed by deprotonation leads to the intermediate allyl vinyl ether (141) which, under the conditions of the deprotonation, undergoes a thio-Claisen rearrangement to afford thioamide (143 Scheme 10). Thermolysis of (143) at elevated temperature affords the Cope product (142) in addition to some of its deconjugated isomer. Several unique characteristics of the thio-Claisen sequence should be noted first, the heteroatom-allyl bond is made in the alkylation step, this connection teing not notrtudly practised in the parent Claisen reaction ... 

Garlic contains various sulfur-containing compounds, all of which are derived from allicin, which is formed from alliin by the action of allinase, which is released when garlic is chopped (Srivastava and Tyagi, 1993). Allicin then produces diallyl sulfide, diallyl disulfide, diallyl trisulfide, ajoenes, methyl allyl trisulfides, vinyl dithiins, and other sulfur compounds, depending on how the garlic is prepared. 

In the case of the observation of poor overall enantioselectivity due to the presence of two competing enzymes with different enantioselectivities, one of the most straightforward methods to improve the enantioselectivity is the use of the inhibitor of the unnecessary enzyme(s). Ethyl chloroacetate, methyl vinyl ketone, allyl alcohol, allyl bromide, sulfur compounds, Mg2+, Ca2+, etc. have been reported as inhibitors of enzymes in yeast [87 97l... 

The curves for n-paraflSns and sulfur compounds were adapted from similar plots by Grant and Manes, who used a different definition of the molar volume. Limited data show that highly chlorinated hydrocarbons are more strongly adsorbed than the sulfur compounds, as shown in Fig. 25.4, but data for vinyl chloride fall closer to the line for paraffins, as expected. The adsorption of oxygenated species such as ketones and alcohols on BPL carbon can be estimated using the curve for sulfur compounds. 

The potassio intermediates give excellent results in a number of derivatizations. For other functionalizations, particularly those with carbonyl compounds, potassium has to be replaced by lithium, this can be done most simply by addition of an equivalent amount of anhydrous lithium bromide, dissolved in THF. Although both vinyl ethers and the corresponding sulfides can be metallated in a short time, it is quite clear from the preparative experiments that the sulfides react faster [9]. A similar difference between oxygen and sulfur compounds has been observed in retaliations of other types of substrates. Some authors have invoked d-orbital effects to explain the easier retaliations of sulfur compounds [83], but an explanation on the basis of polarizability seems more satisfactory [84]. Using the kinetically very active bases mentioned, clean a-metallations of simple vinylic ethers and -thioethers can be realized at low temperatures. Under modified conditions two other processes have been observed [9,85] ... 

It appears from several reactions that sulfur stabilizes a negative charge better than does oxagen. In general anions derived from sulfur compounds are also formed more easily than the oxygen analogues. Thus, if methyl vinyl sulfide is added at... 

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