Nitrite esters, from alcohols

Dehydrations with phosphoric acid esters Nitrites from oximes Ethylene derivatives from alcohols Furans from y-diketones... 

All bacteria where nitrate ester degradation has been characterized have very similar enzymes. The enzymes eatalyze the nicotinamide cofactor-dependent reductive eleavage of nitrate esters that produces alcohol and nitrite. Purification of the PETN reduetase from Enterobacter cloacae yielded a monomerie protein of around 40 kilo Daltons, which required NADPH as a co-faetor for aetivity. Similar enzymes were responsible for the nitrate ester-degrading activity in Agrobacterium radiobacter (Snape et al. 1997) - nitrate ester reductase - and in the strains of Pseudomonas fluorescens and Pseudomonas putida (Blehert et al. 1999) - xenobiotic reduetases . All utilize a non-covalently bound flavine mononucleotide as a redox eofactor. 

Fortunately, Bertrand was able to obtain nitrite esters of ethylenic alcohols as pure, characterized products. She assumed that photolysis of the nitrites would lead to the alkoxyl radical, as in the Barton reaction, with subsequent intramolecular addition. Isolation of tetrahydrofurfural oxime (62 R = H) starting from the nitrite of 4-pentene-l-ol (61 R = H) supported this hypothesis (Scheme 33). This mechanism was later confirmed by esr spin-trapping techniques and, independently by Rieke, who scavenged the cyclized radical with bromotrichloromethane. 

The reactants are fed separately iato a stUl, from which the product is continuously removed by distillation (qv) (31). Isopropyl nitrate is a valuable engiae-starter fuel and can be used ia explosives (see Explosives and propellants) (32). The nitrite ester, isopropyl nitrite, can be prepared from the reaction of isopropyl alcohol and either nitrosyl chloride or nitrous acid at ambient temperature (33). The ester is used as a jet engine propellant (30). 

Cycloalkoxy radical intermediates are readily generated from a parent alcohol by various methods (e.g., nitrite ester photolysis, hypohalite thermolysis, lead tetraacetate oxidation) (83MI1). Once formed, reactive cycloalkoxy radicals undergo /3-scission to produce a carbonyl compound and a new carbon-centered radical. 

Nitrobenzaldehyde has been prepared from />-nitrotoluene by treatment with isoamyl nitrite in the presence of sodium methylate,1 by oxidation with chromyl chloride,2 cerium dioxide,3 or chromium trioxide in the presence of acetic anhydride.4 It can also be prepared by the oxidation of -nitrobenzyl chloride,5 7>-nitrobenzyl alcohol,6 or the esters of -nitrocinnamic acid.7... 

A series of reactions with gases have been selected for the rapid quantification of many of the major products from the oxidation of polyolefins. Infrared spectroscopy is used to measure absorptions after gas treatments. The gases used and the groups quantified include phosgene to convert alcohols and hydroperoxides to chloroformates, diazomethane to convert acids and peracids to their respective methyl esters, sulfur tetrafluoride to convert acids to acid fluorides and nitric oxide to convert alcohols and hydroperoxides to nitrites and nitrates respectively. 

These compounds contain the fragment R as an alkyl or aryl moiety. In other words, they result from the esterification of an alcohol or a phenol with nitrous acid, nitric acid, phosphoric acid, sulfuric acid, or sulfamic acid, respectively. Many of the esters to be examined in this chapter must be activated prior to eliciting their effects, e.g., the organic nitrites and nitrates, which act as donors of nitric oxide or an analogous molecule, and phosphates, which are activated by hydrolysis or even by phosphorylation (antiviral agents). Sulfates are very seldom active or used as prodrugs, but they have significance as metabolites and as industrial xenobiotics. 

A variation of this procedure is the nitrosation of a phenol such as thymol in an alcohol solution with hydrochloric acid and sodium nitrite. This procedure is said to avoid the evolution of oxides of nitrogen, since it may involve the intermediate formation of ethyl nitrite as the nitrosating agent [31]. However, from the safety standpoint, the oxides of nitrogen and nitrite esters must be considered hazardous. 

Reductive hydrolysis of n-butyl nitrate in an aqueous solution of ethyl alcohol in the presence of sodium hydrosulphide or ammonium hydrosulphide has been carried out by Merrow, Cristol and van Dolah [41], This is a complicated chemical reaction. As the result of hydrolysing the nitrate in the presence of sodium hydro-sulphide (the alkalinity of the solution corresponds to pH 10-11) 93% of nitrite ions and 7% of ammonia are obtained from the ester group nitrogen. When ammonium hydrosulphide is used, the nitrite ions initially produced rise to a maximum concentration and then fall to zero owing to the reducing action of the ammonium hydrosulphide. The reduction process takes place more effectively when the pH is above 10. 

The (R)-enantiomer of (242) has also been prepared and used as a chiral auxiliary in an enantioselective aldol synthesis of (+)-(S )-gingerol (79CB3703). (R )-Glutamic acid (246) was thus converted into (i )-pyroglutamic acid by simply heating in water. Conversion of (247) to its methyl ester and LAH reduction delivered alcohol (248). Ethyl nitrite treatment of (248) gave nitrosoamine (249), which was methylated to furnish (250). Exposure of (250) to LAH completed the synthesis of the required chiral auxiliary RAMP [(R)- l-amino-2-(methoxymethyl)pyrrolidine]. The hydrazone (252), derived from RAMP and acetone, was... 

It is necessary to use ethyl nitrite or other alcohol-soluble nitrous ester, instead of sodium nitrite, in order that advantage may be taken of a solvent from which the sodium azide will precipitate out. 

It is more difficult to remove an alcohol from the corresponding nitroalkane than it is to separate the nitrite ester and the nitroalkane. Minimal exposure to a moist atmosphere is, therefore, desirable since anhydrous ether is hygroscopic and nitrite esters hydrolyze readily, especially if a little acid is present. 

Problem 13.51 Inorganic acids such as H2S04, H3P04, and HOC1 (hypochlorous acid) from esters. Write structural formulas for (a) dimethyl sulfate, (b) tribenzyl phosphate, (c) diphenyl hydrogen phosphate, (d) f-butyl nitrite, (e) lauryl hydrogen sulfate (lauryl alcohol is n-C ]H23CH2OH), (/) sodium lauryl sulfate. ... 

Octyl alcohol, 34, 3 -Octyl fluoride, 36, 42 1-Octyl nitrite, 38, 75 Olefins from amine oxides, 39, 41, 42 Oleic acid, 37, 66, 68, 77 39, 15 Oleoyl chloride, 37, 66 Orthocarbonic acid, tetraethyl ESTER, 32, 68... 

The Barton reaction (photolysis of a nitrite ester ) has been employed to attack C-4 methyl substituents in 4,4-dimethyl-5a-steroids. Nitrites of the 6a-and 6)3-alcohols (714) afforded alkoxyl radical species, which attacked the 4a-and 4/ -methyl groups respectively, giving the corresponding aldoximes e.g. 715). Yields were quite high (56—60%) from the 6a-ol and the 19-nor-6 -ol, but attack... 

---