Cyclopropanes, nitro

Similar results are observed in the conjugative addition of CH-acidic methylene compounds with the metal derivatives of 2-nitro-5,10,15.20-tetraphenylporphyrin (6). The nickel porphyrin 6 (M = Ni) yields with an excess of dimethyl malonate the cyclopropane derivative 7 whereas the copper porphyrin 6 (M — Cu) forms with two equivalents of malononitrile the bisadduct 8.111... 

In recent years, the variety of useful diazo substrates for asymmetric intramolecular cyclopropanation processes has really expanded. As another example, Charette and Wurz have reported the first example of an intramolecular cyclopropanation involving a-nitro-a-diazo carbonyl compounds.This reaction, catalysed by Rh2[(S)-DOSP]4, led to the formation of nine-membered nitrocyclopropyl lactones in good yields and enantioselectivities with extremely high diastereoselectivities (Scheme 6.17). This novel methodology constituted an efficient entry into chiral functionalised macrocyclic-fused cyclopropane oc-amino acids. 

Scheme 6.17 Intramolecular cyclopropanations of a-nitro-a-diazo carbonyl compounds.

In cyclopropane, the C,C bond between the atom bearing the nitro group and the most substituted atom of the ring is cleaved. 

It was demonstrated (83) that the reaction of dinitrostyrenes (28) with aryl diazo compounds RR CN2 afford nitronates (24 g) in good yields. These products contain the nitro group at the C-4 atom in the trans position with respect to the substituent at C-5 (if R =H). Since the reaction mechanism remains unknown, the direct formation of cyclic nitronates (24 g) from pyrazolines A without the intermediate formation of cyclopropanes also cannot be ruled out. 

The -N(OSiMe3)2 fragment is an equivalent of the nitroso group. It was demonstrated (493) that cyclopropanes (385) can serve as equivalents of the corresponding nitrosocyclopropanes in coupling reactions of the nitroso group with anions of nitro compounds (Eq. 2). 

The corresponding para nitro-substituted cyclopropane does not eliminate ethylene. However, alkene elimination is observed for the higher homologues, i.e. n = 3-5. The product ion has in this case been proved to be 4-nitrostyrene77 see Scheme 9. 

Cyclopropanderivate setzen umgekehrt Reaktionen, die mit einer Erniedrigung der Koordinationszahl eines C-Atoms von 4 auf 3 verkniipft sind, betrachtlichen Widerstand entgegen. So besitzt Nitro-cyclopropan nach Hass und Shechtek 95) nur sehr geringe Aciditat und vermag selbst in stark alkalischem Medium keine Salze zu bilden. 

Cyclopropanes. XIII. 1-Acetyl-2-nitro-3-phenyl-cyclopropane and its... 

While primary aliphatic amines are converted to nitro compounds on reaction with ozone these reactions are accompanied by numerous by-products.Such side-reactions are largely suppressed by first dissolving the amine onto silica gel followed by passing a stream of 3 % ozone in oxygen through the solid at -78 °C under anhydrous conditions, where yields of between 60 and 70 % are reported. This route has been used to synthesize the energetic cyclopropane (65) from the diamine (64) (Table 1.7). ... 

Cyclopropane is reported to react with dinitrogen pentoxide in methylene chloride at subambient temperature to yield 3-nitro-l-propanol nitrate. ... 

In the presence of even only mild electrophiles, cycloproparenes react via cleavage of the cyclopropane ring. However, the extremely bulky bis(triisopropyl-silyl) group offers efficient steric protection, and 302 is unreactive towards Br2. It reacts however with 67% HNO at 25 °C to afford the 3-nitro derivative 303 in 58% yield. The nitro group of 303 has been reduced to the amine which was acetylated. Reaction of 303 with LiAlH, in turn, afforded the corresponding azo compound. ... 

The meso-ionic 1,3-oxazol-S-ones show an incredible array of cycloaddition reactions. Reference has already been made to the cycloaddition reactions of the derivative 50, which are interpreted as involving cycloaddition to the valence tautomer 51. In addition, an extremely comprehensive study of the 1,3-dipolar cycloaddition reactions of meso-ionic l,3-oxazol-5-ones (66) has been undertaken by Huisgen and his co-workers. The 1,3-dipolarophiles that have been examined include alkenes, alkynes, aldehydes, a-keto esters, a-diketones, thiobenzophenone, thiono esters, carbon oxysulfide, carbon disulfide, nitriles, nitro-, nitroso-, and azo-compounds, and cyclopropane and cyclobutene derivatives. In these reactions the l,3-oxazol-5-ones (66)... 

Photoexcited nitrobenzene may be used for benzylic hydroxylation (at C-9) of 17/3-acetoxy-3-methoxyoestra-l,3,5(10)-triene. The photochemistry of the 17/3-nitro-steroid (217) is markedly solvent dependent, the major products being in ether the 17-desnitro-compound (218), in propan-2-ol the hydroxylamine (219), and in EtOH-NaOEt the hydroxamic acid (220) and the cyclopropane (221). The hydroxamic acid (220) is probably formed through the oxaziridine (Scheme 7). Although there are analogies to this in the photochemistry of nitrones and oximes, the photoreduction of a nitroalkane in propan-2-ol to an alkyl-hydroxylamine appears to have no precedent. Further studies of photochemistry of conjugated... 

Of the many substituted and functionalized alkenes that have been combined with diazo dipoles to give A -pyrazolines or products derived from them (i.e., A -pyrazolines, pyrazoles, cyclopropanes), only a selection will be mentioned. These include ot-alkylidene-cycloalkanones (62), -flavanones, -thioflavanones, -chroma-nones, and thiochromanones (63,64) a-arylidene-indanones and -indolones (65) diarylideneacetones (66) l-benzopyran-2(77)-ones (coumarins) (67,68) 4-nitro-1,2-oxazoles (69) 2-alkylidene-2-cyanoacetates (70) dimethyl 2,3-dicyanofuma-rate (71) tetracyanoethylene (72) tetraethyl ethylenetetracarboxylate (72) 1,4-quinones (35,73-75) 2-X-l,l,l-trifluoro-2-propene [X = Br, (76), SPh, SOPh, S02Ph (77)] nitroalkenes (78) including sugar nitroalkenes (79) 1-diethoxyphos-phoryl-1-alkenyl-sulfoxides (80) methyl 2-(acetylamino)cinnamate and -acrylate... 

Mit x,/i-ungesattigten Carbonsaure-nitrilen werden aus dem Additionsprodukt unter Abspaltung der Nitro-Gruppe substituierte Cyclopropane erhalten1. 

Die Addition von Nitro-alkanen an 1 -(1 -Alkenyl)-1 -trimethylsilyloxy-cyclopropane in me-thanolischer Benzyl-trimethyl-ammonium-hydroxid-Losung (Triton B) liefert unter Ring-offnung 7-Nitro-4-oxo-alkansaure-Derivate z.B.1 ... 

Fluoro-3-nitro- ElOa. 625 (Cyclopropane + 02N BF ) Fluoro-oxo- ElOa. 683 (H -> F)... 

This cyclopropanation can be extended to anions of ally lie, benzylic, and tertiary nitro compounds. 

Acid-catalyzed seven-membered ring formation to afford the first stable A-oxo-2,1 -benzoxazepinium ions has been reported, based on reaction of l-chloro-2-(2-nitrobenzyl)cyclopropane with H2S04 and FSO3H nitro group trapping of an intermediate carbocation was proposed in this process <1996ZOR852>. 

Enantioselective organocatalytic cyclopropanations have been performed using directed electrostatic activation conditions.164 Using a new class of iminium catalysts, cyclopropanation has been conducted with enals but not electron deficient alkenes, such as unsaturated nitrile, nitro, or alkylidene malonate systems. 

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