Reduction nitro group

The use of fixed bed catalysts is described in several patents (33—37). Methods of operation include upflow, trickle bed, and even vapor phase. Typically, a large volume of solvent is used to moderate the temperature rise associated with the high heat of reaction for nitro group reduction. 

Amide Cleavage Induced by Nitro Group Reduction... 

Palladium, platinum, or nickel, supported or unsupported, are the metals usually used in nitro-group reductions. The choice of catalyst often depends on what other functions are present and on the products desired,... 

Photolytic. The UV photolysis (7, = 300 nm) of bifenox in various solvents was studied by Ruzo et al. (1980). In water, 2,4-dichloro-3 -(carboxymethyl)-4 -hydroxydiphenyl ether and 2,4-di-chloro-3 -(carboxymethyl)-4 -aminodiphenyl ether were identifled. In cyclohexane, 2,4-dichloro-4 -nitrodiphenyl ether and methyl formate were the major products. In methanol, a dichloro-methoxy phenol was identified. Photodegradation occurred via reductive dechlorination, de-carboxymethylation, nitro group reduction, and cleavage of the ether linkage (Ruzo et al., 1980). 

Interestingly, treatment of a-nitrostilbene in water-ethyl acetate mixture by the cation-radical of A,A -dioctyl-4,4 -bipyridinium (the octylviologen cation radical) leads to the formation of products derived from the nitro group reduction. No dimerization is observed (Tomioka et al. 1986). Water is responsible for the fixation of transferred electron within the nitro group. Further reactions result in the formation of the corresponding oxime and ketone as shown in Scheme 2.10. 

Fusion of the imidazole ring to pyrrolo-benzothiadiazepine 340 can be achieved by straightforward TosMIC cycloaddition approach (Scheme 72, Section 4.2 (1994JHC1033)). An alternative sequence starts with the addition of nitromethane to the C-N double bond on the thiadiazepine ring, nitro group reduction and manganese oxide oxidation of the intermediate dihydroimidazole derived from amine 342 and tiiethyl ortho formate. 

The requisite hydroxylamine function for such cyclizations can also be generated from a precursor having a nitro group. This novel route has provided access to hitherto unknown l-hydroxy-6-allyl-, and -6,6-bisallyl-piperazine-2,5-diones (91UP1). The starting material is an W-nitroacetyl amino acid ester that can be either mono-or bis-allylated at the methylene adjacent to the nitro group. Reduction of the N02 to NHOH using zinc/ ammonium chloride, followed by cyclization, leads to the desired products (Scheme 76). Compound (215) is unique in that it possesses a chiral center at C-3 and a quaternary carbon at C-6 on a l-hydroxypiperazine-2,5-dione system. 

Achtnich, C., H. Lenke, U. Klaus, M. Spiteller, and H.-J. Knackmuss, Stability of immobilized TNT derivatives in soil as a function of nitro group reduction , Environ. Sci. Technol., 34, 3698-3704 (2000). 

The resin-bound phenylene diamine intermediates 3 are then generated by nitro group reduction with tin(II) chloride in NMP and cyclization/ aromatization with a wide variety of aldehydes gave the resin-bound benzimidazole intermediates 4. The treatment of this intermediate with 50% TFA/DCM liberates the substituted 3-(benzoimidazol-l-yl)-propionic acid derivative 4a. Analysis of this intermediate by HPLC and LC-MS gave a measure of the purity of the resin-bound product and enabled the optimization of conditions for the incorporation of the Rl-nitroarenes and R2-aldehydes by an iterative process. 

We have previously described the basic resin handling and washing procedures, as well as nitro group reduction, cyclization with aldehydes to form the benzimidazole ring, and chemical encoding procedures for a related benzimidazole system.18 Reagents and solvents used are available from Aldrich (Milwaukee, WI) and Calbiochem-Novabiochem (San Diego, CA). 

The resin-bound perfluoroalkylsulfonyl linker is compatible with many common solid-phase reactions, such as tin dichloride-mediated aromatic nitro group reduction, trifluoroacetic acid-mediated tBoc deprotection, reductive amination reactions, acylation, and sulfonation. It is possible to perform several sequential synthetic reactions on the nonflate resin so that multistep syntheses can be carried out. The solid-phase approach provides an operationally simple, inexpensive, and general protocol for the cleavage... 

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