Nitrosyl chloride electrophilic

For nitrosyl chloride (Entry 8) and nitrosyl formate (Entry 9), the electrophile is the nitrosonium ion NO+. The initially formed nitroso compounds can dimerize or isomerize to the more stable oximes. 

The electrophilic addition of nitrosyl chloride with 3-methyl-l,2-butadiene at 0°C afforded 2-nitroso-3-chloro-3-methyl-l-butene, in which the nitrosyl group was connected to the central carbon atom [10]. 

Secondary aromatic amines under these conditions form initially the AT-nitroso derivative (see notes on the purification of secondary amines in Expt 6.56), which when treated with hydrogen chloride in anhydrous ethanol-ether solution rearranges to the nuclear substituted nitrosoamine (eg.. p-nitroso-AT-methylaniline, cognate preparation in Expt 6.62). This rearrangement proceeds via the intermediate formation of the electrophilic nitrosyl chloride ... 

A reaction corresponding to Eq. (5-30) is the addition of nitrosyl chloride to alkenes such as cyclohexene or styrene [84, 85]. The reaction seems to be faster in polar solvents e.g. nitrobenzene and trichloromethane) than in less polar solvents e.g. toluene and tetrachloromethane). This is consistent with the view that the reaction involves an electrophilic attack of NO —Cl . The reaction was, however, also found to be very slow in diethyl ether. Presumably, this is due to strong bonding of the NO+ cation to the ether oxygen atom [84]. 

The cis addition of nitrosyl chloride to cyclic unconjugated polyenes was observed in dichloromethane28. From cyclooctadiene a single diastereomeric dimer 3 (either meso or dl) was produced due to conformational factors associated with the cis configuration. This product underwent transannular electrophilic reaction to give 4. From (Z,Z,Z)-l,5,9-cyclododecatriene the chloro nitroso adduct 5 was obtained as a mixture of the meso and dl forms and was converted to -chloro amine 6 by lithium aluminum hydride/aluminum trichloride reduction 6 was converted to the corresponding aziridine. 13C-NMR spectroscopy was extremely useful in determining the diastereomeric composition of the nitroso dimers. 

The nitrosonium ion (NO ) is another electrophile which is generated either from the oxides of nitrogen or from nitrosyl chloride. The nitrosochloride may tautomerize to chloro-oxime adducts. 

Electron-deficient alkenes (e.g., NCHC=C(COOMe)2) can be aziridinated with 0-(aryl-sulfonyl)hydroxylamines <9lCOS(7)469>. The reaction is believed to involve a Michael addition followed by cyclization with expulsion of a sulfonate anion. Less electrophilic alkenes react in lower yield but with high stereoselectivity (Equation (2)). The chiral catalyst prepared from an optically active bisoxazoline and Cu(I)triflate is effective in promoting the enantioselective aziridination of alkenes <93JA5328>. The addition of nitrosyl chloride to alkenes, which are especially susceptible to... 

Reaction of the arylthallium(III) compound with an electrophile affords an intermediate cationic arylthallium derivative (90), which then undergoes elimination of the thallium moiety. Examples of this type of reactivity are the reactions of arylthallium(III) compounds with bromine affording aryl bromide, with iodine affording aryl iodide, 1 8-110 or with nitrosyl chloride giving nitroso-benzene. l ... 

The kinetics of addition of nitrosyl chloride to a number of olefins have been examined. In chloroform, methyl and phenyl substituents enhance the rate while electron-withdrawing groups (e.g. chlorine) retard it. Such be-haviour would be consistent with electrophilic attack by the dipole NO-CP. The effect of changes in the solvent was not simple, although more polar solvents (nitrobenzene, chloroform) speeded the reaction (compared with toluene or carbon tetrachloride). Methanol appeared to be a remarkably poor reaction medium, perhaps due to interaction with the reactant the low reactivity of nitrosyl chloride in diethyl ether was attributed to strong bonding between the solvent and the incipient NO cation. 

Mercuric acetate and mercuric trifluoroacetate are the usual reagents. The synthetic utility of the mercuration reaction derives from subsequent transformations of the arylmercury compounds. As indicated in Section 7.3.3, arylmercury compounds are only weakly nucleophilic, but the carbon-mercury bond is reactive toward various electrophiles. The nitroso group can be introduced by reaction with nitrosyl chloride or nitrosonium tetrafluoroborate as the electrophile. Arylmercury compounds are also useful in certain palladium-catalyzed reactions, as discussed in Section 8.2. 

However, the formation of other compounds of the halogens with other elements in which the sharing of electrons leads to more positive oxidation states for the halogen has served organic chemistry well. Examples of such compounds with positive oxidation states for the halogens were provided in Chapter 6 (cf. Table 6.1), and they include hypochlorous acid (HOCl) nitrosyl chloride (NOCl), iodine azide (IN3), and iodine isocyanate (INCO). It may be recalled that it was argued there that the electron-rich double bond attacked the electrophilic halogen to lead the process of electrophilic addition. 

Nitrogen.—An indirect method of determining the electrophilic reactivity of nitrosyl chloride towards various substrates in aqueous solution has been proposed. The action of nitrosyl chloride, bromide, and thiocyanate or nitrosating agents in micellar systems has been studied, and the results were interpreted in terms of the competition of anions present in solution for sites at the surface of a cationic micelle. The kinetics of the oxidation of nitrite to nitrate by chlorine and bromine are complex and have been interpreted in terms of mechanisms involving the nitryl halides as intermediates ... 

Electrophilic displacement. Account for the fact that nitrosyl chloride, C1N=0, and antimony pentachloride, SbClj, both of which are covalent molecules, react with each other to form a salt. 

Beyond these general characteristics of electrophilic addition, certain of the reagents shown in Scheme 4.4 exhibit special features which should be noted. The addition of nitrosyl chloride or nitrosyl formate to alkenes is accompanied by subsequent reactions if the nitroso group is not tertiary. The nitroso compound may dimerize or rearrange to the more stable oxime tautomer. 

The reaction of acylsilanes with acid chlorides in the presence of A1C13 leads to furans (Table 9.41) [45]. In these reactions an acyl cation initiates the addition with ensuing silyl migration yielding an intermediate vinyl cation. Attack of the carbonyl oxygen followed by proton loss affords the observed products (Scheme 9.16). An analogous reaction with nitrosyl fluoroborate provides a route to oxazoles (Table 9.42) [65]. The nitrosyl cation serves as the electrophile in this application. 

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