Nitronic acid esters

A considerable number of experiments with 1,3-cycloaddition were reported by Tartakovskii, Novikov and co-workers (181-1851- They reacted nitronic acid esters (esters of aciform of primary or secondary nitro alkanes) with dipole-philes such as styrene, vinyl chloride, acrylic esters and methyUvinyl ketone (36c). The reaction occurs at room temperature (or lower) with an excess of un-satured compound, the yield is 60-90%. 

The reaction of nitronic acid esters with acetylene derivatives yielded a2iri-dines(36d)(186]. 

Iminocarbonic acid esters Nitronic acid esters... 

Nitronic acid esters, cyclic s. 4H-l,2-Oxazine 2-oxide ring, 5,6-dihydro-Nitronitiic acid esters... 

Asymmetric additions of Reformatsky-type reagents to nitrones 258a and 258b have also been reported (Scheme 139). The reagents were prepared in situ from ZnEt2 and the corresponding iodoacetic acid ester. Diisopropyl (R,R)-tartrate 262 was employed as a chiral inductor. Enantioselectivities varied significantly the best results were obtained at 0 °C when a nitrone was added to the reaction mixture over a 2 h period. 

The chemistry of a-haloketones, a-haloaldehydes and a-haloimines Nitrones, nitronates and nitroxides Crown ethers and analogs Cyclopropane derived reactive intermediates Synthesis of carboxylic acids, esters and their derivatives The silicon-heteroatom bond Syntheses of lactones and lactams The syntheses of sulphones, sulphoxides and cyclic sulphides... 

Reactions with Carboxylic Acid Esters Alkyl nitrones can be metallized upon treatment with phenyl lithium in ether solution. The Li-derivatives react with carboxylic acid esters to give 3-oxo nitrones (305)- the analogs of 3-diketones and j3-keto esters (545). With the help of the 13C NMR method it has been found that 3-oxo nitrones (305) exist as an equilibrium mixture... 

The addition of lithium or magnesium ester enolates to nitrones in THF at 78°C or in Et20 at — 20°C, constitutes a direct synthesis of /V-hydroxy- 3-amino acid esters (Scheme 2.180) (645). 

Asymmetrical addition of alkynylzinc reagents to nitrones has been achieved in the presence of L-tartaric acid ester as a chiral additive (665). 

Nucleophilic addition of methyl- or phenylphosphite n -butyl- esters to oxo-imine salts, generated by nitrone alkylation of triethyloxoniumtetrafluoro borate (Meerwein salt), leads to a-aminophosphinic acid esters (Scheme 2.201) (691). 

Owing to the fact that silyl esters of nitronic acids (SENAs) are readily available, rather stable, and exhibit various reactivities, these compounds have attracted considerable interest in the chemistry of nitronates. 

Time-resolved resonance Raman spectroscopy has been used to study the photorearrangement of o-nitrobenzyl esters in polar and protic solvents53 in acetonitrile, the only primary photoproduct is nitronic acid 68 with a lifetime of 80 microsecond, while in methanol the nitronic acid exists in equilibrium with the nitronate anion 69, giving a lifetime of 100 microseconds (equation 41). 

A study of the regioselectivity of the 1,3-dipolar cycloaddition of aliphatic nitrile oxides with cinnamic acid esters has been published. AMI MO studies on the gas-phase 1,3-dipolar cycloaddition of 1,2,4-triazepine and formonitrile oxide show that the mechanism leading to the most stable adduct is concerted. An ab initio study of the regiochemistry of 1,3-dipolar cycloadditions of diazomethane and formonitrile oxide with ethene, propene, and methyl vinyl ether has been presented. The 1,3-dipolar cycloaddition of mesitonitrile oxide with 4,7-phenanthroline yields both mono-and bis-adducts. Alkynyl(phenyl)iodonium triflates undergo 2 - - 3-cycloaddition with ethyl diazoacetate, Ai-f-butyl-a-phenyl nitrone and f-butyl nitrile oxide to produce substituted pyrroles, dihydroisoxazoles, and isoxazoles respectively." 2/3-Vinyl-franwoctahydro-l,3-benzoxazine (43) undergoes 1,3-dipolar cycloaddition with nitrile oxides with high diastereoselectivity (90% de) (Scheme IS)." " ... 

Dihydro-5-isonitro-4,-methyl-4-methylene-1,1, 5 -trinitro-2,2 -biimidazole Methyl Ester or 4-Methyf-4,-methylene-1,1l,5I-trinitro-2,2 -biimidazole-5 -nitronic Acid Methyl Ester,... 

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