Sulfinyl Ethylenes

The stereochemical course of these reactions and the configurational assignment of the adducts was rationalized by assuming that conformation B (s-cis, s-trans) must be favored over A (s-trans, s-trans), due to the strong electrostatic repulsion between the sulfinyl oxygens (Fig. 6). A complete 7r-facial selectivity (both p-tolyl groups are oriented toward the same face) and a higher endo-ori- 

One of the most interesting points that can be deduced from the studies carried out on the bis-sulfoxides is the much lower reactivity of acyclic dienophiles than that of cyclic examples (compare the results obtained from 80 and 75 or those from 82 and 83). The influence of the conformation around the C-S bond (with higher restrictions in cyclic sulfoxides), on the dienophilic character of the double bond in vinyl sulfoxides, emerge as the most likely causes of the observed differences in reactivity (see later). 

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The only paper concerning catalysis by Lewis acids of the Diels-Alder reactions of these simple sulfinyl ethylenes was due to Ronan and Kagan [20], who studied the influence of TMSOTf in the reaction of compound (S)-l with cyclo-pentadiene and furane. In the first case, the reaction occurs at 0°C in 3 h, giving an 89 11 mixture of endo and exo adducts (overall yield 60%) with very high n-facial selectivity (de> 92%). The high efficiency of the catalyst increasing the reactivity of 1 also made possible its reaction with furan, which evolved with low endo/exo selectivity (55 45) and lower 7r-facial selectivity (de 70%) than that observed with cyclopentadiene. These excellent results were nevertheless, eclipsed by those reported in the same paper [20] concerning the activation of... 

From the above results it can be inferred that sulfinyl ethylenes are not good dienophiles because of their low reactivity and poor stereoselectivity. In order to improve both of these factors, different electron-withdrawing groups (able to increase dienophilic reactivity and to restrict conformational movement around the C-S bond, thus improving the stereoselectivity) were incorporated into the double bond. They are presented in the sections below, classified according to the number and kind of the additional activating groups present in the vinyl sulfoxide moiety. 

In contrast to a, -ethylenic ketones or even a, -ethylenic sulfones, a, ) -ethylenic sulfoxides generally are not sufficiently electrophilic to undergo successful nucleophilic j8-addition . a-Carbonyl-a, j8-ethylenic sulfoxides, however, are potent, doubly activated alkenes which undergo rapid and complete -addition of various types of nucleophiles even at — 78 °C. A brief account summarizing this area is available . The stereochemical outcome of such asymmetric conjugate additions to enantiomerically pure 2-sulfmyl 2-cycloalkenones and 2-sulfinyl-2-alkenolides has been rationalized in terms of a metal-chelated intermediate in which a metal ion locks the -carbonyl sulfoxide into a rigid conformation (36 cf. 33). In this fixed conformation, one diastereoface of the cyclic n... 

Aluminum Ammonia, anhydrous Chlorinated hydrocarbons, halogens, steam Mercury, halogens, hypochlorites, chlorites, chlorine(I) oxide, hydrofluoric acid (anhydrous), hydrogen peroxide, chromium(VI) oxide, nitrogen dioxide, chromyl(VI) chloride, sulfinyl chloride, magnesium perchlorate, peroxodisul-fates, phosphorus pentoxide, acetaldehyde, ethylene oxide, acrolein, gold(III) chloride... 

Thus, a-sulfinyl lithium carbanion of 1-chloroethyl p-tolyl sulfoxide was reacted with 1,4-cyclohexanedione mono ethylene ketal (195) to afford the adduct (196) in quantitative yield. The adduct was treated with ferf-butylmagnesium chloride (magnesium alkoxide was initially formed) followed by isopropylmagnesium chloride to result in the formation of magnesium /3-oxido carbenoid 197. The /3-oxido carbenoid rearrangement then takes place to give one-carbon expanded magnesium enolate 198. Finally, an electrophile was... 

ENANTIOMERICALLY PURE a-SULFINYL-a.g-ENONES PREPARED FROM ETHYLENE KETALS OF a-BROMO-a.fi -ENONES... 

S)-(+)-2-(p-Toluenesulflnyl)-2-cyclopentenone ethylene ketal l,4-Dioxaspiro[4.4]non-6-ene, 6-[(4-methyl phenyl)sulfinyl]-,... 

The most common nonionic surfactants are those based on ethylene oxide, referred to as ethoxylated surfactants. Several classes can be distinguished alcohol ethoxylates, alkyl phenol ethoxylates, fatty acid ethoxylates, sorbitan ester ethoxylates, fatty amine ethoxylates, and ethylene oxide-propylene oxide copolymers (sometimes referred to as polymer surfactants). Another important class of nonionics are the multihydroxy products such as glycol esters, glycerol (and polyglycerol) esters, glucosides (and polyglucosides), and sucrose esters. Amine oxides and sulfinyl surfactants represent nonionic with a small head group. 

ETHANOL (64-17-5) CjHjOH Flammable liquid. Forms explosive mixture with air [explosion limits in air (% by volume) 3.3 to 19 flash point 55°F/13°C 68°F/20°C (80%) 72°F/22°C (60%) 79°F/26°C autoignition temp 685°F/363°C Fire Rating 3], Reacts, possibly violently, with strong oxidizers, strong acids bases, strong peroxides acetic anhydride, acetyl bromide, acetyl chloride, aliphatic amines, bromine pentafluoride, calcium oxide (quicklime), cesium oxide, chloryl perchlorate, disulfiiryl difluoride, ethylene glycol methyl ether, iodine heptafluoride, isocyanates, nitrosyl perchlorate, perchlorates, platinum, platinum-black catalyst potassium-tert-butoxide, potassium, potassium oxide, potassium peroxide, potassium superoxide phosphorus (III) oxide, silver nitrate, silver oxide, sulfuric acid, oleum, sodium, sodium hydrazide, sodium peroxide, sulfinyl cyanamide, tetrachlorosilane, s-triazine-... 

In spite of the CIDNP polarization pattern, we believe the sulfinyl mechanism can be dismissed. First, the SO bond in a sulfinyl radical is very strong. Using Benson s estimate for the heat of formation of the phenylsulfinyl radical (13 kcal/mol) [63] and standard values for the other relevant compounds [98], the S-0 bond energy is ca. 102 kcal/mol, whereas the C-S bond is some 35 kcal/mol weaker. Transfer of an O atom from phenylsulfinyl to a methyl radical is endothermic by 11 kcal/mol, and to epoxidize ethylene endothermic by 40 kcal/mol. (The relevance of the latter example will become clear below.) Furthermore, from the a-cleavage work discussed previously, it is clear that the expected product from reaction to an arylsulfmyl radical and a carbon radical is a sulfenic ester or disproportionation product. 

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