Nitroalkanes dinitroalkanes

Aliphatic nitroalkanes can be categorized into six basic groups primary, secondary and tertiary nitroalkanes, terminal and internal gem-dinitroalkanes, and trinitromethyl compounds. Primary and secondary nitroalkanes, and terminal gem-dinitroalkanes, have acidic protons and find particular use in condensation reactions for the synthesis of more complex and... 

A range of primary and secondary nitroalkanes and their derivatives have been converted to the corresponding gem-dinitroalkanes via oxidative nitration, including the conversion of nitroethane, 1-nitropropane, 2-nitropropane and 2-nitro-1,3-propanediol to 1,1-dinitroethane (78 %), 1,1-dinitropropane (86 %), 2,2-dinitropropane (93 %) and 2,2-dinitro-1,3-propanediol (77 %) respectively. The silver nitrate used in these reactions can be recovered quantitatively on a laboratory scale and this has led to a study where oxidative nitration has been considered for the large-scale production of 2,2-dinitropropanol (25) from the nitroethane (22). ... 

Oxidative nitration is a one step process from nitroalkane to gem- dinitroalkane, whereas the Ter Meer reaction requires two steps (initial halogenation followed by halide displacement with nitrite anion). 

Kaplan and Shechter found that certain oxidants react with the nitronate salts of secondary nitroalkanes to yield vic-dinitroalkanes (111) in a reaction referred to as oxidative dimerization. These reactions are believed to involve transfer of an electron from the secondary alkyl nitronate to the oxidant with the production of a nitroalkyl radical. The radical can then dimerize to the corresponding vtc-dinitroalkane (111) (Equation 1.2) or lose nitric oxide to form a ketone via the Nef reaction (Equation 1.3). Unfortunately, formation of the ketone is a major side-reaction during oxidative dimerization and is often the major product. 

Oxidative dimerization gives reasonable yields of vtc-dinitroalkanes for some substrates 2,3-dimethyl-2,3-dinitrobutane (48, 53 %) and 3,4-dimethyl-3,4-dinitrohexane (37 %) are obtained from 2-nitropropane (76) and 2-nitrobutane respectively.However, oxidative dimerization fails to convert 1,1-dinitroethane and trinitromethane into 2,2,3,3-tetranitrobutane and hexanitroethane respectively. Additionally, oxidative dimerisation is not a feasible route for the synthesis of v/c-dinitroalkanes from primary nitroalkanes. Although oxidative dimerization is limited in scope, and yields are often poor, the starting materials are usually inexpensive. 

Some 1,3-dinitroalkanes (145) have been synthesized from the reaction of nitroalkanes with a-nitroalkenes (144) generated in situ from the decomposition of Mannich bases (143) derived from primary nitroalkanes. Reported yields for these reactions are low and the formation of by-products limits the feasibility of the method. 

The reaction of nitroalkanes and dinitroalkanes with sodium hydrogen telluride gives nitrosoalkane dimers and olefins, respectively.96 The reduction of other nitrogenated species such as hydroxylamines, azides, nitroso, azo, and azoxy compounds can also be performed by using tellurium reagents.6,11,12... 

Preparation of gem-Dinitroalkanes. A methanolic solution of alkali metal hydroxide (Li, Na, or K) was treated with 10% excess nitroalkane and stirred for 30 minutes. The solution was evaporated to dryness in vacuo, and the alkali metal alkyl nitronate was aned over phosphorus pentoxide at reduced pressure (0.1 mm.) for 24 hours. (Caution nitronate salts may be shock sensitive and have been known to explode after prolonged storage.) A slurry of 3.3 grams (0.02 mole) of lithium 1-nitro-cyclohexane in 50 ml. of acetonitrile was cooled to —40°C., and 2.7 grams (0.02 mole) of nitronium tetrafluoroborate were slowly added. The reaction was not exothermic, and the reaction mixture turned brilliant blue upon adding nitronium tetrafluoroborate. The reaction mixture was stirred for 2 hours at —30° to —40°C., then filtered to give a quantitative yield of lithium tetrafluoroborate. The filtrate was quenched into 100... 

Cleavage of C-N bonds has been described elsewhere, for example, the reduction of g wj-dinitroalkanes to nitrite ion and nitroalkane anion [181,182] and f-nitroalkanes to nitrite and alkyl radical (Chapter 9) and the reduction of pyridylamines to picoline and ammonia (Chapter 18) [13,14] a rare case of a reductive loss of a nitro group from a benzene ring in l,2,4,5-tetrafluoro-3,6-dinitrobenzene has been reported [183]. Reduction of activated azides yields azide ion phenacyl azide is thus reduced to acetophenone and azide [236]. 

Dinitroalkanes, obtained by condensation of nitroalkane Mannich base with other nitroalkanes or by Michael addition of nitroalkanes to nitroalkenes give 1,3-diones only when a secondary amine is used as base however, yields are moderate (- 40%). 

The anions of nitroalkanes (nitronates) can be used as precursors in a connective and regiospecific synthesis of tetrasubstituted alkenes. They are easily formed on reaction with LiOMe and undergo oxidative dimerization in the presence of bromine. The resultant 1,2-dinitroalkanes (Scheme 37) participate in a reductive elimination involving an rc1 radical chain mechanism when irradiated in the presence of Na2S, PhSNa or the lithium nitronate derived from 2-nitropropane. 

Nitric acid (70 %) or the mixture of nitric acid and sulfuric acid or other mixed acids with catalytic function can nitrate secondary nitroalkanes directly into gem-inal dinitroalkane [8]. With the sodium alkoxide and tetranitromethane, primary nitroalkanes can be nitrated into dinitroalkanes and trinitroalkanes [9]. In a neutral or basic solvent, primary, secondary nitroalkane salts can be nitrated, step by step, into gem-dinitroalkanes by silver nitrate and sodium nitrite [10]. Alkali metal salts of aryl nitroalkanes can be nitrated, step by step, into dinitroalkanes and trinitroalkanes by dinitrogen tetroxide [11]. 

In 2007, Jorgensen and co-workers [51] developed cascade reaction between dinitroalkanes (77) and enals catalyzed by diphenylprolinol derivative XXIV and DABCO. After the first Michael addition between the nitroalkane and the enal, an... 

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