Nitrosation alkenes

The well-known method of furazan formation is based on nitrosation of alkenes. Thus, several NO donor 3,4-disubstituted 1,2,5-oxadiazole 2-oxide derivatives and the related 1,2,5-oxadiazoles, containing methylsulfonylphe-nyl, phenylsulfonyl, sulfonylamidophenyl, and phenylsulfonylamido groups were synthesized by nitration of... 

Aside from the relatively trivial conversions of nitronates to the corresponding oxime and carbonyl compounds (10,11), the chemistry of nitronates remained relatively unexplored for much of the early 1900s. However, in 1964, Tartakovskii et al. (12) demonstrated that alkyl nitronate esters were competent partners in the newly discovered class of dipolar cycloadditions with alkenes (Scheme 2.1). Both cyclic and acyclic nitronates participated, thus providing a new functional group were the nitrogen atom existed at the center of an acetal (13). These compounds were subsequently referred to as nitroso acetals (14) or nitrosals (15). 

Aziridines can undergo loss of a nitrogen atom in a number of ways and this process is frequently stereospecific in terms of the alkene formed. For example, the reaction of aziridines, e.g. (268), with nitrosating agents such as nitrosyl chloride or methyl nitrite results in the formation of alkenes wit.h greater than 99% stereoselective deamination (64JOC1316). Such transformations proceed via N- nitrosoaziridine intermediates which are isolable at temperatures below -20 °C, but which decompose to the observed products at higher temperatures. 

The minor products frequendy formed in deaminations may result from such side reactions as reaction of the intermediate cation with nucleophiles, for example, acetate or chloride ions,49,30 present in low concentration. Nitrite ions can give rise to nitrite esters or ni-troalkanes 50,51 the former are probably hydrolyzed prior to or during processing of the products.52 Some alkenes have been reported to react with nitrous acid or related nitrosating agents.19,58 Enol ethers would be expected to be more nucleophilic than simple alkenes, and it has been found that D-glucal reacts with nitrous acid under the conditions of deamination.54... 

An unusual chloronitro(bipy)(N,N -dinitroso-l,2-ethylenediaminato)platinum(IV) complex has been prepared by nitrosation of [PtCl2(en)(bipy)]Cl2.1166 Similar arylnitroso complexes of platinum(0) can be formed from nitrosobenzene and an appropriate precursor platinum(O) complex (equation 363).1167 This compound reacts with C02, CS2, alkenes and alkynes to give megacycles (equation 364).1168... 

Synthesis of 1,3,2-dithiazoles has been the most extensively studied. Various structural types of these compounds have been synthesized in 1990s from raV-dithiols, bis(sulfenylchlorides), and alkynes <1996CHEC-II(4)433>. Much attention has been paid to the preparation of stable 1,3,2-dithiazolyl radicals and, especially, cations. The synthetic potential of 1,3,2-oxathiazoles and 1,3,2-dioxazoles is restricted by several uncommon procedures including nitrosation of thiolcarboxylic acids and photochemical addition of nitrobenzene to alkenes <1996CHEC-II(4)433>. 

Rearrangement of N-nitrosoamides. N-Nitrosamides (1), prepared by acetylation of primary amines followed by nitrosation, are known to decompose in nonpolar solvents at 80-100° to form alkyl acetates with elimination of nitrogen.9 The presumed diazoalkane intermediate (a) can be trapped as a rhodium carbene (b), which undergoes rearrangement to an alkene (equation I). The overall result is a mild, nonbasic version of the classical Hofmann degradation of amines. 

Nitrosyl chloride has been much used in organic solvents synthetically to bring about various nitrosations e.g. of alkenes and amines. A recent example... 

The monosubstituted (trifluoromethyl)carbene has only been generated by irradiation of 2,2,2-trifluorodiazocthane, which is prepared by nitrosation of 2,2,2-trifluoroethylamine.1,3 175 The course of reactions with alkenes is dependent on concentration and pressure conditions. Thus, insertion products and pyrazolines may be obtained in competition with [2+1] cycloaddition giving the cyclopropane system. Yields of the latter are often moderate and, depending on singlet or triplet carbene formation, the reaction is not always stereoselective (Table 14). 

The amide N-H may also be halogenated, oxidized and nitrosated. A -Bromosuccinimide (NBS), like a number of other iV-halo compounds, readily undergoes a radical fission to give a bromine radical. This provides a useful reagent for radical bromination at, for example, allylic or benzylic positions. In the presence of acid, NBS is also a mild source of the halonium ion, which is used for the addition of hypobromous acid (Scheme 3.74) to alkenes or for the bromination of reactive aromatic rings. 

Less common methods of synthesis include nitrosation of suitable alkenes in acetonitrile solution (see Section 3.02.8.1.3(ii)) <84TLI319>, cyclization of iV-alkoxy ureas <87S1058>, and specific approaches to benzimidazole oxides from quinoxaline oxides, and to imidazole oxides from oxa-diazine and pyrazine oxides <93CHE127>. 

Oxidative transformations of substituents may be found in Section 7.2.2.1.1.5.6. (oxidations of thioethers, aldehydes, alkenes, and methyl groups). Included for formal reasons are nitrosations (formation of azides and diazonium cations from hydrazines or amines) (Section 7.2.2.I.1.5.6.). 

A rather complex mixture of seven alcohols can be detected (besides alkenes and nitrites). The product ratio of the alcohols (normalized to 100 in Table 7-3) is dependent on the initial concentration of the amine 7.74, on the nitrosating reagent and on the mineral acid used. The product ratio in HCIO4, to a lesser extent also in HCl, is dependent on the concentration of the amine, and is obviously also influenced by the cmc. The influence of micelles can be seen in the yields for 7.75, i. e., the product of straightforward substitution, and also in the configuration of the compounds formed by a 1,2-hydride shift, 3-methylhexan-3-ol (7.76) and... 

In Summary Nitrous acid attacks amines, thereby causing N-nitrosation. Secondary amines give Ai-nitrosamines, which are notorious for their carcinogenicity. Ai-Nitrosamines derived from primary amines decompose through SnI or Sn2 processes to a variety of products. Ai-Nitrosation of N-methylamides results in the corresponding N-nitrosamides, which liberate diazomethane upon treatment with hydroxide. Diazomethane is a reactive substance used in the methylesterification of carboxylic acids and as a source of methylene for the cyclo-propanation of alkenes. 

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