Displacements using nitronate salts as nucleophiles

Nitronate salts can react with alkyl halides to yield polynitroaliphatic compounds with varying degrees of success. The main by-products of these reactions arise for competitive 0-alkylation. Alkyl nitrates are formed as by-products when the nitroform anion is used in these reactions.  

Methyl iodide (31) reacts with silver nitroform (32) in acetonitrile to give a 51 % yield of 1,1,1-trinitroethane (33). ° The potassium salt of nitroform in acetone has been used for the same reaction.Yields between 28 % and 65 % have been reported for the reaction of silver nitroform in acetonitrile with higher molecular weight alkyl iodides. The choice of solvent is important in some reactions, for example, silver nitroform reacts with l,4-dibromo-2-butyne (34) in solvents like dioxane and acetone to give l,l,l,6,6,6-hexanitro-3-hexyne (35) in approximately 72 % yield, whereas the same reaction in acetonitrile is reported to give a mixture of compounds. 

Poor to modest yields of trinitromethyl compounds are reported for the reaction of silver nitroform with substituted benzyl iodide and bromide substrates. Compounds like (36), (37), and (38) have been synthesized via this route these compounds have much more favourable oxygen balances than TNT and are probably powerful explosives. The authors noted that considerable amounts of unstable red oils accompanied these products. The latter are attributed to O-alkylation, a side-reaction favoured by an SnI transition state and typical of reactions involving benzylic substrates and silver salts. Further research showed that while silver nitroform favours 0-alkylation, the sodium, potassium and lithium salts favour C-alkylation. The synthesis and chemistry of 1,1,1-trinitromethyl compounds has been extensively reviewed. The alkylation of nitronate salts has been the subject of an excellent review by Nielsen.  

The reactions of alkyl halides with the silver salt of dinitroacetonitrile have been shown to be of limited use for the synthesis of polynitroaliphatic compounds. These reactions give a mixture of C-, N- and O-alkylation products with product distribution highly dependent on the nature of the substrate.  

The addition of a-chloronitroalkanes to solutions of alkali metal hydroxide has been used for the synthesis of some 1,2-dinitroethylene derivatives (43). These reactions involve attack of the nitronate salt (40) on the aci-form (39) of the unreacted em-chloronitroalkane followed by formal loss of hydrogen chloride. 2,3-Dinitro-2-butene and 3,4-dinitro-3-hexene (45) are formed in this way from 1-chloro-l-nitroethane and 1-chloro-l-nitropropane (44) respectively. 

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