Alkyl nitrites groups

Nitroparaffias (or nitroaLkanes) are derivatives of the alkanes ia which one hydrogen or more is replaced by the electronegative nitro group, which is attached to carbon through nitrogen. The nitroparaffins are isomeric with alkyl nitrites, RONO, which are esters of nitrous acid. The nitro group ia a nitroparaffin has been shown to be symmetrical about the R—N bond axis, and may be represented as a resonance hybrid ... 

Under alkaline conditions, alkyl nitrites nitrosate imidazoles which possess a free NH group in the 4-position (70AHC(12)103). Nitrosation of 3,5-dimethylpyrazole gives the 4-diazonium salt by further reaction of the nitroso compound with more NO". 5-Pyrazolinones are often nitrosated readily at the 4-position. 3-Alkyl-5-acetamidoisothiazoles undergo 4-nitrosation. 

Doyle et al. (1977 c) and Oae et al. (1980) reported modified Meerwein arylations with significant improvements in the yield by the use of aryl amines and alkyl nitrites in place of arenediazonium salts. However, good yields are only achieved if alkenes activated by electron-withdrawing groups are present. 

Carbons adjacent to a Z group (as defined on p. 548) can be nitrosated with nitrous acid or alkyl nitrites. The initial product is the C-nitroso compound, but these are stable only when there is no tautomerizable hydrogen. When there is, the product is the more stable oxime. The situation is analogous to that with azo compounds and hydrazones (12-7). The mechanism is similar to that in 12-7 R—H —> R + N=0 — R—N=0. The attacking species is either NO or a carrier of it. When the substrate is a simple ketone, the mechanism goes through the enol (as in halogenation 12-4) ... 

Primary, secondary, and tertiary aliphatic amines have been cleaved to give aldehydes, ketones, or carboxylic acids with aqueous bromine and with neutral permanganate. The other product of this reaction is the amine with one less alkyl group. In a different type of procedure, primary alkyl primary amines can be converted to ge/n-dihalides, RCH2NH2 —> RCHX2 (X =Br or Cl), by treatment with an alkyl nitrite and the anhydrous copper(I) halide. 

The groups of Doyle and of Oae148 showed that the yields can be improved by the use of arylamines and alkyl nitrites in place of arenediazonium ion, i.e. by a one-pot diazotization-Meerwein procedure. A condition for good yields is, however, that the alkenes be activated by electron-withdrawing groups. 

Photolysis of primary, secondary, and tertiary alkyl nitrites in benzene indicated that a minimum chain length of five carbon atoms attached to the nitrite grouping is required for appreciable yields of secondary nitroso dimers via the Barton reaction. In the case of primary and secondary nitrites, a chain of length of four carbon atoms or more attached to the nitrite grouping is required for formation of the six-membered intermediate (e.g., A) involved in the Barton reaction.139140... 

Alkyl methyl ketones undergo nitrosation at the reactive methylene group when treated with nitrous acid or an alkyl nitrite [Method (fi)]. The presence of hydrogen on the a-carbon permits tautomeric rearrangement to the oxime of a 1,2-dicarbonyl compound. Acidic hydrolysis of the oxime, which is best carried out in the presence of a hydroxylamine acceptor such as laevulinic acid,143 affords a further useful route to the 1,2-dicarbonyl system. 

Acylaminomalonic esters and related reagents are widely used for the synthesis of a-amino acids. The method differs from those syntheses already discussed in that the amino group is incorporated into the system from the outset. A popular reagent is diethyl acetamidomalonate (35). The acetamido group can readily be introduced into the reactive methylene position in diethyl malonate by first converting the latter into the hydroxy-imino derivative (33) by reaction with nitrous acid or an alkyl nitrite (cf. Section 4.2.7, p. 413). This derivative is then reduced catalytically to diethyl aminomalonate (34) which is acetylated using acetic anhydride. 

Amyl nitrite is generally sold in small glass bottles or, in rare cases, small vials or ampoules. It is chemically related to nitroglycerine. It is part of a group of closely related chemicals known as alkyl nitrites. In street terminology, amyl, butyl, isobutyl, isoamyl, isopropyl, and cyclohexyl nitrates and nitrites are collectively... 

Acetals result from oxidative coupling of alcohols with electron-poor terminal olefins followed by a second, redox-neutral addition of alcohol [11-13]. Acrylonitrile (41) is converted to 3,3-dimethoxypropionitrile (42), an intermediate in the industrial synthesis of thiamin (vitamin Bl), by use of an alkyl nitrite oxidant [57]. A stereoselective acetalization was performed with methacrylates 43 to yield 44 with variable de [58]. Rare examples of intermolecular acetalization with nonactivated olefins are observed with chelating allyl and homoallyl amines and thioethers (45, give acetals 46) [46]. As opposed to intermolecular acetalizations, the intramolecular variety do not require activated olefins, but a suitable spatial relationship of hydroxy groups and the alkene[13]. Thus, Wacker oxidation of enediol 47 gave bicyclic acetal 48 as a precursor of a fluorinated analogue of the pheromone fron-talin[59]. 

Another example of the application of gas-phase NMR techniques to conformational equilibria is the investigation of conformational effects on the relative maxima in the N-0 bond internal rotation potential function in primary nitrites of one to five carbon atoms [27,22]. Alkyl nitrites (ONOR) exist as mixtures of syn and anti conformers which differ in the orientation of the alkyl group with respect to the nitrosyl group. 

A general method of replacement of the primary aromatic amino group by hydrogen is reduction of aromatic diazonium salts, prepared by diazotization, typically by treatment of the primary amine or its salts with sodium or potassium nitrite in strongly acidic aqueous media. Conversion to the diazonium salts may also be accomplished in nonaqueous media using acetic acid, or using alkyl nitrites (equation 86). Most diazonium salts decompose at temperatures above 0-5 C. Only certain salts such as naphthalene-1,5-sulfonates,tetrafluoroborates ° ° and hexafluorophosphates ° ° are stable at room temperature. 

The first absorption band of simple alkyl nitrites occurs in the region 3200-4400 A and displays considerable fine structure it appears to be related to an n - n transition of the non-bonding nitrogen electrons to the antibonding n group orbital of the double bond system . A second stronger absorption, has a maximum around 2200-2300 A (n, a transition). The major photodissociative process in alkyl nitrites is the homolytic cleavage of the O-N bond to form NO and alkoxy radicals which are usually vibrationally and/or electronically excited. 

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