Fluoro nitrobenzenes

The syntheses of these three compounds share a common route as described by Brickner et al. [53] and Barbachyn et al. [54]. Namely, the coupling reaction of 3,4-difluoronitrobenzene (82) with piperazine, morpholine, or thiomorpholine to yield the corresponding 4-substituted 3-fluoro-nitrobenzene (83), which upon reduction gives rise to the aniline derivative (84). Carbobenzoxy protection of the active nitrogen of 84 using benzyloxy-carbonyl chloride (CbzCl) results in the formation of carbamates 85a and 85b. Treatment of 85a,b with n-BuLi and (i -glycidyl butyrate yields a 5-(R)-... 

The PE spectra of several substituted nitrobenzenes like the nitrotoluenes, fluoro-nitrobenzenes and dinitrobenzenes have been investigated141. Some data are summarized in Table 18. For the characteristic IPs of the nitro group ( o+, 2) one or two... 

Shimizu N, Yasui Y, Matsumoto N. 1983. Structural specificity of aromatic compounds with special reference to mutagenic activity in Salmonella typhimurium - a series of chloro- or fluoro-nitrobenzene derivatives. Mutat Res 116 217-238. 

Nitrobenzene starburst polymers were also prepared by reacting amine-termini intermi-nates with 4-fluoro-nitrobenzene. Thereafter the nitro component was reduced using 5% palladium on carbon and is described by the author. 

Another example for the coordinative behaviour of phenoxy functionalised carbene ligands comes from the Bielawski group [76]. They synthesised a phenoxy functionalised benzimi-dazolium salt starting from o-fluoro-nitrobenzene, which they reacted with o-hydroxyaniline. Reductive ring closure reaction with formic acid/formate and palladium/charcoal as catalyst... 

For a-substitution, we can compare, for instance, a for the p-fluoro-nitrobenzene radical-anion with a. for the nitrobenzene radical-anion in aqueous solution the ratio is 7-95 3-40, i.e. 2-3 1 (Kolker and Waters, 1964) for the o-fluoro and p-fluoro-substituted phenoxy radicals the corresponding ratios are 2-6 (Stone and Waters, 1964a). There are probably two contributions to the observed fluorine-splitting (Carrington et al., 1965) a spin-polarization term, as for C— H, giving negative spin density at the fluorine nucleus, and a spin-polarization of the fluorine Is and 2s electrons which arises from spin density in a 2p orbital on fluorine (C—— F) and results in a positive spin density at the... 

Use Spartan View to examine electrostatic potential maps of the intermediate Meisenheimer complexes in the reactions of o-fluoronitrobenzene and m-fluoro-nitrobenzene with CHsO". Which atoms in each complex are most negatively charged Which reaction is more likely to occur ... 

Synthesis of bis[4-(2-phenyl-2-isopropyl)phenyl]-4-nitrophenylamine) (1). In a 500 ml three neck round-bottom flask was placed bis[4-(2-phenyl-2- isopropyl)phenyl] amine (20.0 g, 49 mmol), 4-fluoro-nitrobenzene (5.23 g, 49 mmol), sodium hydroxide (1.18 g, 49 mmol), and 120 ml DMSO. The mixture was heated with stirring at 120°C for 24 hr. The reaction mixture was cooled and then poured into 11 methanol. The yellow precipitate was eolleeted by filtration and dried under vacuum. The product was purified by silica gel column chromatography ( -hexane dichloromethane = 2 1) to afford nitro compound 1 16.3 g in a 63% yield mp 150-151"C by DSC (lO C/min). 

The principle of the split-split method is illustrated by an example of a three combinatorial step benzimidazole library that uses 24 amines, 12 o-fluoro-nitrobenzenes, and 48 acids, producing a library of 13,824 compounds (Scheme 1) (10), The first step can be performed in 24 La Marast reaction vessels, each containing 12 g of resin. For the second combinatorial step, resin from each La Marast reaction vessel is split into 24 syringes and the Domino Block synthesizer is used to handle the syringes. The last combinatorial step is performed in wells of 96-well plates, with the resin from each syringe being split into two rows (24 wells) of a plate. 

Most of the kinetic data obtained to determine the influence of the base concentration in die VNS reaction have been obtained from competitive experiments between VNS and SnAt reactions in fluoro nitrobenzenes like 4 with carban-ions derived from sulfones 5. Could you explain why (R is a substituent that cannot be replaced by SNAr). 

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