Nitroso decarboxylation

E. Nitroso Decarboxylations (Elimination-Type Reaction). 2-5. Preparation of 2,6-Dibromo-4-nitrosophenol. ... 

A reaction which has some resemblance to this nitroso decarboxylation is the pyrolytic or photolytic decarboxylation of fluorinated nitrites (Eqs. 24 and 25) [63]. The nitroso compounds derived from these nitrite esters appear... 

Azetidine, 7V-bromo-, 7, 240 Azetidine, AT-r-butyl- N NMR, 7, 11 Azetidine, AT-t-butyl-3-chloro-transannular nucleophilic attack, 7, 25 Azetidine, 3-chloro-isomerization, 7, 42 Azetidine, AT-chloro-, 7, 240 dehydrohalogenation, 7, 275 Azetidine, 7V-chloro-2-methyl-inversion, 7, 7 Azetidine, 3-halo-synthesis, 7, 246 Azetidine, AT-halo-synthesis, 7, 246 Azetidine, AT-hydroxy-synthesis, 7, 271 Azetidine, 2-imino-stability, 7, 256 Azetidine, 2-methoxy-synthesis, 7, 246 Azetidine, 2-methyl-circular dichroism, 7, 239 optical rotatory dispersion, 7, 239 Azetidine, AT-nitroso-deoxygenation, 7, 241 oxidation, 7, 240 synthesis, 7, 246 Azetidine, thioacyl-ring expansion, 7, 241 Azetidine-4-carboxylic acid, 2-oxo-oxidative decarboxylation, 7, 251 Azetidine-2-carboxylic acids absolute configuration, 7, 239 azetidin-2-ones from, 7, 263 synthesis, 7, 246... 

When an acylaminomalonic acid monoester is treated with nitrous acid, the nitroso derivative XX decarboxylates into a N-acyl amidoxime which spontaneously cyclizes into an oxadiazole 33 a). 

Cycloaddition of a-nitroso acrylic esters (749) to alkenes followed by base hydrolysis provides a route to 5,6-dihydro-4//-l,2-oxazine-3-carboxylic acids (750). These heterocycles on heating above 150 °C decarboxylate to furnish y-hydroxynitriles (thus the overall c/s-addition of OH and CH2CN to a double bond), which can be transformed further to y-lactones (751) by treatment with methanolic hydrochloric acid (Scheme 172) (79CC1090). The adducts were also reduced to a-amino esters (752) by the action of aluminum amalgam (Scheme 173) (79CC1089). 

The solvent deuterium isotope effect in the reaction of 359 with glyoxylate decreases from ( H2o/ D2o) °f 1-66 to ( H2o/ D2o) °f 1-12 with increasing pH from 1.25 to 6.43, respectively. 361 probably decarboxylates via a cyclic transition state. Transfer of the carboxylic proton takes place simultaneously with heavy-atom reorganization as indicated by small solvent DIE in the acid-catalysed reaction. The solvent DIE h2o/ D20 °f 1-20 at 1. M H+, observed in the reaction of 359 with pyruvic acid, is similar to the reaction of pyruvic acid with nitrosobenzene for which nucleophilic attack of nitroso nitrogen has been proposed395. 

Incorporation of natural amino acids (114, 115,116, 117, 118) and homologs (119,120,121) without further chain lengthening (VII to XVI) proceeds with retention of the a-amino nitrogen (119, 120, 122). An enzyme catalyzing the oxidation and decarboxylation of the N-hydroxyamino acid VIII to the aldoxime XI (123,124) has been purified 1400-fold (125). It is stimulated by FMN, O2 uptake is observed, and the a-keto acid oxime V is not used as a substrate (124,125). Decarboxylation may occur via the a-nitroso acid IX. Incorporation of the nitro compound XIII (126) presumably occurs via the acf-nitro compound XII which was suggested by Ettlinger and Kjaer (72) as an intermediate. The addition of thiols to... 

Sulfamethoxazole failed to produce any trappable radicals with an array of different spin traps, but naproxen afforded the EPR spectrum shown in Figure 2.11 when irradiated with 330 nm UV-R in the instrument cavity in the presence of 2-methyl-2-nitroso-propane (MNP). The spectrum contains contributions from di-t-butyl nitroxide, a known photoproduct of MNP. The H-atom adduct MNP-H also evident can arise by several different mechanisms, including the trapping of an H atom by MNP the reaction of MNP with an electron followed by protonation and the direct reduction of MNP by an excited state species. In view of the flash photolysis results, it was concluded that photoionization was the major precursor of MNP-H. The third radical corresponded to a C-centered radical carrying a single H atom, leading to the postulate of a decarboxylation reaction as the primary photochemical step. Confirmation of the participation of free radical intermediates came from the initiation of the free radical polymerization of acrylamide with rates as shown in Table 2.1. 

Motherwell and Potier have been interested in the reactivity of thionitrite esters as a potential surrogate of nitric oxide toward carbon-centered radicals. Tertiary thionitrite esters react with Barton esters to give after decarboxylation the corresponding oximes or the nitroso-dimers in moderate yield [57]. 

Primary and secondary nitroso compounds usually stabilize themselves, even under the conditions of their preparation, by passing irreversibly into their isomers, the oximes. In tertiary aliphatic nitroso compounds this transformation is accompanied by fission of the neighboring carbon-carbon bond by hydrolysis or decarboxylation. Aromatic nitroso compounds are more stable, and when oxime formation does occur this is usually reversible within the framework of a true tautomeric equilibrium for instance, the tautomeric pair -nitrosophenol/p-benzoquinone monooxime is obtained both by nitrosation of phenol and by oximation of />-benzoquinone. 

Ohshima et al. (2852) identified several A-nitrosamino acids, 3-(methylnitrosamino)propanoic acid [also known as A-methyl-A-nitroso-P-alanine (NMPA)], 4-(methylnitrosamino) butanoic acid (NMBA), and l-nitroso-2-piperidinecarboxylic acid (also known as A-nitrosopipecolic acid), in various types of tobacco (cigarette, chewing, pipe, cigar, and snuff tobaccos). Decarboxylation of these A-nitrosamino acids would yield NEMA, A-nitrosomethylpropylamine, and NPIP. lARC (1986) did note the 1985 Ohshima et al. findings on these A-nitrosamino acids in tobacco. 

The known free-radical decomposition of aryl nitrosoamides (ArN(NO)COR ) and the report that nitrosoamides of 0-alkyl-hydroxylamines decompose by a free-radical pathway indicate that free-radical processes might occur in the normal nitrosoamide decomposition. In fact, the aliphatic nitrosoamides have been used as initiators at elevated temperatures for the polymerization of styrene and other olefins At, or near, room temperature, however, it appears that free radicals are not formed in the nitrosoamide decomposition. It has been found, for example, that (1) COj (a product of the decarboxylation of carboxyl radicals) is not formed in the decomposition (2) the scavenger nitric oxide has no effect on the reaction (3) normal products and no polymer are formed in the decomposition of A -(i-butyl)-A -nitrosobenzamide ° ° and N-nitroso-7V-(l-phenylethyl)acetamide -in styrene and (4) no difference in acetate yields is observed when A -nitroso-A-(1-phenyl-ethyl) acetamide is decomposed in benzene in the presence or absence of 0-1 m Styrene and 1-phenylethyl acetate react with... 

Thioesters of malonic acids [R R C(COSEt)2] are reduced to the alcohols, R R CHCH20H, in 70—80% yield on treatment with W-2 Raney Nickel. ° N-Nitroso-a-amino-acids undergo smooth thermal decarboxylation to give... 

N-Alkyl(or aryO-JV-nitroso-a-amino-acids can be decarboxylated by photolysis under acidic conditions to give amidoximes. ... 

TNT, 1,3 DNB, 1,3,5-TNB, some nitrocresol isomers, and 3,5-dinitroani-line. Several unexpected compounds were also identified, including A -nitroso-morpholine, TV morpholinoacetonitrile and nitrobenzonitrile isomers. The morpholine derivatives are not directly related to the nitration of toluene, and are possibly the result of the use of morpholine as an algaecide in water-cooling devices at munitions facilities. The major component in the wastewater was 1,3-DNB. Its formation is attributed to oxidation followed by decarboxylation of the methyl group in 2,4-DNT rather than to direct nitration of benzene. 

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