Nitro alkanes, acidity

The selection of solvents for quantitative work is not easy. Nitro-alkanes are sufficiently inert, but nitronium tetrafluoroborate is poorly soluble in them c. 0-3 %). Nitronium salts react rapidly with acetic anhydride, and less rapidly with acetic acid, A, A -dimethylformamide and acetonitrile, although the latter solvent can be used for nitration at low temperatures. Sulpholan was selected as the most suitable solvent ... 

The use of chiral crown ethers as asymmetric phase-transfer catalysts is largely due to the studies of Bako and Toke [6], as discussed below. Interestingly, chiral crown ethers have not been widely used for the synthesis of amino acid derivatives, but have been shown to be effective catalysts for asymmetric Michael additions of nitro-alkane enolates, for Darzens condensations, and for asymmetric epoxidations of a,P-unsaturated carbonyl compounds. 

Weis, C. D. Newkome, G. R. Facile elimination of nitrous acid from quaternary nitro-alkanes./. Org. Chem. 1990, 55, 5801-5802. 

Primary CH/CD or CH/CT kinetic isotope effects, corresponding to D+ or T+ abstraction rate constants, compared to those for H+, have been extensively studied and compared to similar effects for other C—H acids such as nitro-alkanes. For monocarbonyl compounds, the effects are usually large (kA)H/-(kA )o > 4 and sometimes close to or even higher [e.g. (koH-)H/(koH-)D = 9.8 between acetone and [2H6)acetone (J. R. Jones, 1965)1 than the theoretically expected maximum value ( 1). 

A considerable number of experiments with 1,3-cycloaddition were reported by Tartakovskii, Novikov and co-workers (181-1851- They reacted nitronic acid esters (esters of aciform of primary or secondary nitro alkanes) with dipole-philes such as styrene, vinyl chloride, acrylic esters and methyUvinyl ketone (36c). The reaction occurs at room temperature (or lower) with an excess of un-satured compound, the yield is 60-90%. 

Albright ct al (971 examined the inlluence of gamma radiation upon Ihc vapour phase nitration of propane with nitric acid at 400 450°(. There was a slight effect of irradiation on the yield of nitro products, in agreement with the above finding (Ob). The increase of the yield o nitro alkanes was of the order of onlv 10 15%. 

The alternative disconnection (20) requires the Michael addition of an acyl anion equivalent. Cyanide ion, a reagent for COjH and nitro alkane anions (Chapter 22) are both good at Michael additions, so that addition of cyanide ion to (21) is a route to y-keto acids (22). 

Nitro alkanes are so acidic that only a weak base is needed for the Michael reaction. The cyclisation gives the more substituted double bond. 

When a molecule contains electronegative substituens isotope exchange is simpler than it is with hydrocarbons. It occurs relatively readily with nitro-alkanes, alkyl cyanides, monochloroacetic acid, acetamide, and similar compounds. The following prescription has been given for the preparation of [1,1-D2] nitroethane 8 5... 

Nitric acid also has many irKlustrial uses for production of nitro-aromatics and nitro-alkanes, of wdiich explosives manufacture is the largest. Another application of nitric add is for adipic acid production (an intermediate product in Nylon production). In this case the concentrated add is used. A summary of applications of nitric add is given in Figure 8.1. 

The condensation reaction of coordinated amines with formaldehyde and nitro-alkanes is believed [166] to proceed through an imine (or aminol) intermediate sensitive to attack of the carbon acid conjugate base on the imine carbon atom (Scheme 2-11). The intramolecular path shown in this diagram is entropically favourable, so construction of the six-membered chelate cycle becomes possible and its formation proceeds in high yield. It should also be pointed out that the first condensation step involves nucleophilic attack on an HCHO molecule by a coordinated amido ligand arising from deprotonation of the metal-bound primary amine. 

In 1988 Reetz et al. introduced the concept of metal-free polymerization of acrylates, methacrylates and acrylonitrile [224,225]. Metal-free initiators are salts consisting of a carbanion (A ) having R4N as cationic counterions. They are synthesized by the reaction of neutral CH or NH-acidic compounds such as malonic acid esters, nitriles, sulfones, nitro-alkanes, cyclopentadiene, fluorene derivates, carbazoles and succinimide. Water is removed azeotropically using toluene. 

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