2-nitropropane anion

The moderate resistance of DMSO to oxidation permits it to be used as a solvent for oxidations with lead tetraacetate or the 2-nitropropane anion (33,34). Dichromate oxidation and permanganate oxidation have been used for quantitative deterrnination of DMSO (35,36). 

A mechanism of this type permits substitution of certain aromatic and ahphatic nitro compounds by a variety of nucleophiles. These reactions were discovered as the result of efforts to explain the mechanistic basis for high-yield carbon alkylation of the 2-nitropropane anion by p-nitrobenzyl chloride. p-Nitrobenzyl bromide and iodide and benzyl halides that do not contain a nitro substituent give mainly the unstable oxygen alkylation product with this ambident anion ... 

The reacdon of l,2-dimethyl-5-nitroimidazole v/ith 2-nitropropane anion gives the new highly branched imidazole derivadve, which is formed via cine-snbsdtudon and Spj l subsdni-don fEq 5 67 ... 

Also other anions, such as the 2-nitropropanate anion, Grignard reagents (Table 8, numbers 8 and 9), and borates [113], can be added to olefins. 

The first clue to the existence of the SrnI mechanism came from product studies both in aliphatic and aromatic cases. It was noticed that in the reaction of benzyl and substituted benzyl chlorides with the 2-nitropropane anion, oxygen alkylation, yielding the oxime and then the aldehyde, occurs exclusively in the case of benzyl chloride and 3-nitrobenzyl chloride, whereas, with 4-nitrobenzyl chloride, the yield of aldehyde is only 6% and the carbon-alkylated (104) product is obtained in 92% yield (Kornblum, 1975). This was interpreted as the result of a competition between 8, 2 (O-alkylation) and S l (C-alkylation) reactions. In the aromatic case, it was observed that the reaction of 5- and 6-halopseudocumenes with KNHj in liquid ammonia (Kim and Bunnett, 1970) forms the 5- and 6-pseudocumi-dines in a ratio which is the same whether the starting compound is the 5- or 6-isomer in the case of the chloro- and bromo-derivatives, as expected from an aryne mechanism (Scheme 9), whereas much more non-rearranged... 

For carbon nucleophiles sequential addition of 2-potassio-2-nitropropane and oxygen to 4-arylidene-2-phenyl-5(47/)-oxazolones 623 has been reported (Scheme 7.200). The process involves a Michael reaction of the 2-nitropropane anion followed by reaction with molecular oxygen and elimination of nitrous acid to yield 2-aryl butenoic acid imides 626. 

Recently, sonication has been proposed as another possibility for initiation. The reaction of/ -nitrobenzyl bromide with 2-nitropropane anion may be thus initiated (equation 12)36. 

The reaction7641 of 2-chloromethyl-5-nitrothiophene with the 2-nitropropane anion was recently reinvestigated, and extended to various nitronate anions76b. These reactions, taking place by the S l mechanism, afforded good yields of new 5-nitrothiophenes bearing a trisubstituted ethylenic double bond at the 2-position. Some of these derivatives showed the same antiprotozoan activity as that of reference compounds. 

The m-nitrobenzyl chloride analogue 2-(chloromethyl)-l-methyl-4-nitroimidazole reacts with the 2-nitropropane anions by the S l mechanism under phase-transfer conditions. A base-promoted nitrous acid elimination from the C-alkylated product gives alkenylimidazole derivatives84. 

More recently, the reaction of 1-chloromethyl-5-nitroisoquinoline with 2-nitropropane anion was the first reported example of substitution by the S l mechanism in the... 

More recently the C-alkylation of 15 by 2-nitropropane anion was extended to the heterocycle nitronate anion derived from l-methyl-3-nitropyrrolidin-2-one93. 

Crozet, Vanelle and coworkers94 have also described the first example of an S l reaction involving an oxazole system activated by a non-fused tetrasubstituted p-benzo-quinone 17, with 2-nitropropane anion (equation 26). 

On the other hand, 4-chloromethylthiazole activated by a substituted / -benzoquinone in position 2 does not react with 2-nitropropane anion, neither by C- nor by O-alkylation (S l and S, respectively)95. 

Sterically hindered p-cyano- and / -nitro-a-haloisobutyrophenones (18) have been reported to react with the 2-nitropropane anion by the S l mechanism to form the C-alky-lation product99. However, a p-nitro group is necessary for the reactions with diethyl malonate and diethyl methylmalonate, benzenethiolate and /7-toluenesulphinate ions (equation 29). 

Substituted allyl halides also give substitution products by a radical chain process. Thus 3-bromo-l-nitrocyclohex-l-ene (19) undergoes S l reaction with the 2-nitropropane anion giving product 21 derived from valence tautomerism 20a = 20b of the radical intermediate (scheme 2)100. 

The structure of anew alkylating agent, 2-(l-methyl-l-nitroethyl)-5-nitrothiazole and its C-alkylation product of the reaction with 2-nitropropane anion by SRN1 mechanism has been assigned by proton and carbon NMR spectroscopy (Table 3.20) [541, 542],... 

Vanelle, R, Gellis, A., Kaafarani, M., Maldonado, J., and Crozet, M.P. 1999. Fast electron transfer C-aUcylation of 2-nitropropane anion under microwave irradiation. Tetrahedron Letters, 40 4343 6. 

Dinitropropane is in alkaline solution reduced in a two-electron reaction [39-42] to 2-nitropropane anion in slightly acid solution the nitronic acid is reduced to acetone oxime. 1,1-Dinitroethane behaves differently, and a wave height corresponding to n=5-6 is found in acid solution. The following explanation has been suggested [38] ... 

The formation of these products was rationalized in terms of the initial formation of (83). The diene (83), which is a stable, isolable compound tautomeric with (84), reacted with 2-nitropropane anion to give the above-mentioned products, and with sodium p-toluenesulphinate to give (85). The analogous compounds (86 ... 

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