1,3-Dinitro compounds

The Michael addition of nitroalkanes to nitroalkenes is catalyzed by triethylamine to give 1,3-dinitro compounds (Eq. 4.45).60 In some cases, the intramolecular displacement of the nitro group takes place to give cyclic nitronates (Eq. 4.46).61... 

For aromatic or heteroaromatic monoaldehydes, ArCHO, an efficient procedure has been developed for synthesis of 1,3-dinitro compounds [132]. Rather than in situ reduction of O2, the O2 reduction is carried out in a divided cell with the aliphatic nitro compound as the solvent. Charge corresponding to 0.5 F with respect to the aldehyde is passed through the cell, the current is switched off... 

Wang and co-workers [57,58] reported several Michael-type enantioselective additions with nitro-olefins. Under neat conditions, 1,3-dinitro compounds were generated in the 74 addition of nitroalkanes 75 to various P-substituted nitro-olefins (Scheme 15). Other Michael-type involving nitro-olefins reactions were illustrated using triazole donors 77 to offer good yields and high enantioselectivities (Scheme 16). 

Nitration of indolizines is seldom attempted in view of accompanying oxidation reactions. Thus the synthesis of 6- and 8-nitro-2-phenyl-indolizine has been achieved by the cyclization of appropriately substituted 2-methyl-1-phenacylpyridinium bromide.179 However, 1-nitro and 1,3-dinitro compounds have been prepared.4 From the behavior of the indolizine nucleus toward other electrophiles, 3-nitroindolizine might be expected to be the primary product. This compound has been synthesized using a dilute solution of nitric acid in acetic acid at - 70°C where the substrate could well be the base and not the 3-protonated cation as in a nitric acid-sulfuric acid mixture.180... 

The resulting 1,3-dinitro compounds with two consecutive stereochemically defined stereocenters can be readily converted into the corresponding 1,3-diamines, which are versatile chiral building blocks from synthetic as well as pharmaceutical viewpoints (Scheme 9.19). 

A highly diastereo- and enantio-selective formal conjugate addition of nitroalkanes to nitroalkenes has been achieved using a chiral ammonium bifluoride catalyst (9)46 This strategy provides a reliable route to optically active 1,3-dinitro compounds. 

The chiral quaternary ammonium bifluoride (162) has been shown to catalyse a (g) highly diastereo- and enantio-selective conjugate addition of silyl nitronates (160) to nitroalkenes, giving rise to 1,3-dinitro compounds (161) (76-96% ee).213 ... 

Alcantara, M.-P.D., Dianez, M.J., Escribano, F.C., Estrada, M.D., Gomez-Sanchez, A., Lopez-Castro, A., and Perez-Garrido, S. 1996. Synthesis of aliphatic 1,3-dinitro compounds. Synthesis, 1 64-70. 

The series of unsubstituted, 6-chloro-, and 6-methoxy-4-methyl-7-azaindoles were nitrated at —10° to give the corresponding 3-nitro compounds in 56,57, and 60 %yield, respectively. At 0°, the methoxy isomer gave what appeared to be the 1,3-dinitro compound, which decomposed explosively on heating. 

Niazimbetova ZI, Evans DH, Liable-Sands LM, Rheingold AL (2000) Electrochemical synthesis of aliphatic 1,3-dinitro compounds. J Electrochem Soc 147 256-259... 

If an unsaturated aldehyde was combined with a 1,3-dinitro compound, chiral cyclohexanes were formed by a nitro-Michael/Heniy reaction sequence. Miehael addition followed by double Heniy reaction also led to ehiral eyelohexane derivatives. In another application of the Henry re-aetion, Hayashi used nitroalkenes with pentane-l,5-dial (generated in situ) to form ehiral eyelohexane carboxaldehydes. Chiral cyclopentanes were also eonstrueted in another manner. Enamine-mediated Michael addition of aldehydes to 5-iodo-l-nitropent-l-ene led to an intermediate enamine, which underwent intramoleeular cyclisation via iodide displacement. ... 

Nitration has been carried out under very mild conditions, using tetranitromethane [98-100], copperCII) nitrate in acetic anhydride [47,101], nitric acid in acetic anhydride [99], or urea nitrate [102], Either the 1-nitro- [47,98,99,101] or the 1,3-dinitro-compounds [99, 102] are produced. The first method appears to be the most useful. 1-Nitroazulene has been converted into 1-acetylaminoazulene, which was also obtained by Beckmann rearrangement of the oxime of 1-acetyl-azulene [47]. 

Potassium hydroxide alcohol Aliphatic 1,3-dinitro compounds... 

A chiral La(OTf)3//V,A/ -dioxide complex catalyzes enantioselective conjugate addition of nitroaUcanes to nitroalkenes (Scheme 8). This process provides various 1,3-dinitro compounds bearing two stereocenters in high diastereo-and enantioselectivities under mild conditions. 

Synthesis of aliphatic 1,3-dinitro compounds from 1,2-nitramines... 

Du and coworkers have developed a stereoselective direct Michael addition of nitroalkanes to nitroalkenes catalyzed by quinine-derived dimeric squaramide 21 [93]. This transformation provided facile access to 1,3-dinitro compounds in high diastereo- and enantioselectivities starting from aryl-substituted nitroalkenes (Scheme 10.18). However, the use of an aliphatic nitroalkene as Michael acceptor resulted in a low yield and diminished enantioselectivity. While nitroethane and 1-nitropropane are excellent substrates, branched 2-nitropropane did not undergo the Michael addition reaction. The authors also noted that slightly reduced dias-... 

An effective asymmetric synthesis of optically active 1,3-dinitro compounds via the Michael addition of nitroalkanes to nitroalkenes has been described to afford the corresponding adducts with 72 8 dr and up to 94% eeP The catalytic system, a modified cinchona alkaloid derivative (9), performs well with a broad variety of substrates, and the catalyst loading can be decreased to 2 mol% without compromising the asymmetric induction or the reaction rate. 

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