Tellurium nitro compounds

Hydrogenation Catalysts. The key to catalytic hydrogenation is the catalyst, which promotes a reaction which otherwise would occur too slowly to be useful. Catalysts for the hydrogenation of nitro compounds and nitriles are generally based on one or more of the group VIII metals. The metals most commonly used are cobalt, nickel, palladium, platinum, rhodium, and mthenium, but others, including copper (16), iron (17), and tellurium... 

Tellurium Tetrahydrofuran Tetranitroaniline Tetranitromethane Thiocyanates Thionyl chloride Thiophene Thymol Halogens, metals Tetrahydridoaluminates, KOH, NaOH Reducing materials Aluminum, cotton, aromatic nitro compounds, hydrocarbons, cotton, toluene Chlorates, nitric acid, peroxides Ammonia, dimethylsulfoxide, linseed oil, quinoline, sodium Nitric acid Acetanilide, antipyrine, camphor, chlorohydrate, menthol, quinine sulfate, ure- thene... 

The reduction of nitro compounds 38 by tellurium reagents depends on the structure of the substrate and on the solvent used. For example, phenyl tellurol90 and sodium telluride95 reduce nitroarenes to anilines 39 in protic solvents. When an aprotic solvent is used, sodium telluride converts the nitroarenes 38 into the respective azo compounds 40 (Scheme 20).25... 

The ditellurium compounds, in which a Te —Te group joins two carbonyl groups, can be considered to be the tellurium analogs of peroxy compounds derived from carbonic acid or benzoic acids (e.g. benzoyl peroxides). Only a few of these compounds are known. During the reduction of aromatic nitro compounds with disodium telluride in dimethylfor-mamide, bis[dimethylaminocarbonyl] ditellurium was formed as a by-product in yields from 5 to 15%. The formation of this compound was attributed to the capture of the dimethylaminocarbonyl radical by the telluride anion and subsequent oxidation of the tellurocarbamoyl species4. 

Dimethoxyphenyl tellurium trichloride or bis [3,4-dimethoxyphenyl] ditellurium were nitrated, the ortho-nitro compound reduced to the 1,2,5-oxatellurazole with hypophospho-rousacid, and this heterocyclic compound converted to the 5,6-dimethoxy-l,3-benzotellur-azole1. 

Tellurides (H2Te, NaTeH, PhTeH and Na2Te) are inexpensive and effective agents for reducing aromatic nitro compounds to hydroxylamines. Catalytic quantities of tellurium, in the presence of sodium borohydride, reduce p-substituted nitrobenzenes to N-arylhydroxylamines (equation 9). Mild reaction conditions, absence of side reactions and experimental simplicity are the main features of this reduction sequence. 

Selenolates such as Na2Se, NaSeH, PhSeNa, etc., and tellurolates such as NapTe, NaTeH, PhTeNa, etc., are excellent nucleophiles and can reduce a variety of functional groups by nucleophilic attack or single electron-transfer. On treatment with alkali metal selenolates (or amine salts of HpSe and PhSeH), reduction or reductive selenation of ketones and aldehydes, C=C reduction of a,/l-unsaturated compounds, and reduction of nitrogen compounds such as nitro compounds occur successfully [118, 176]. Compared with these selenolate anions, the corresponding tellurium compounds are highly reactive not only toward the same substrates but also toward halo compounds such as a-bromo ketones and vic-dibromoalkanes [46, 52, 177]. 

Molecular structure and thermochemistry are interrelated here for species chosen from contributions to the earlier Volume 3 of this book series. Discussion includes halogenated species gaseous nonmetal dioxides X-Y bond-containing species (X,Y = C, N, O) small carbon molecules arenols and substituted arenes steroids aromatic carbocycles difluoramines and nitro compounds selenium- and tellurium-nitrogen compounds. 

Six derivatives of this system have been reported. Compound (113) was obtained by successive nitration of 3,4-dimethoxyphenyl tellurium trichloride (112) and partial reduction of the resulting 6-nitro derivative of (112) (Equation (10)). Compounds (47a)-(47c) were obtained by reaction of the oximes (114a)-(114c) with tellurium dioxide (Equation (11)) <86USP4607000,87USP4661438). 

There are general reviews on heterocyclic syntheses by cycloaddition reactions of isocyanates and on the use of heterocyclic cations in preparative organic chemistry. More specific topics are 5-hydroxymethylfuran-2-carb-aldehyde, isobenzofurans and related ort/io-quinonoid systems, the conversion of 2//-cyclohepta[Zj] furan-2-one (1) into derivatives of azulene, the synthesis of indoles from o-alkylphenyl isocyanides, and abnormal Fischer indolization reactions of o-methoxyphenylhydrazones. Two reviews on isoindoles have appeared and a lecture on highly conducting charge-transfer complexes that are based on heterocyclic selenium and tellurium donors has been reprinted.Recent advances in the chemistry of imidazole and in the use of nitro-imidazoles as radiosensitizers have been summarized. There have been reviews on benzimidazole A -oxides and on dihydrobenzimidazoles, benzimidazolones, benzimidazolethiones, and related compounds. Other topics are synthetic applications of 1,3-dithiolium and 1,3-oxathiolium salts and of isoxazoles, the chemistry of benzisoxazoles, 2-amino-oxazoles, 5-oxazolones (2), furoxans, benzofuroxans, and related systems, the synthesis of five-membered meso-ionic compounds, and tetrazoles. ... 

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