Reductive conversions

Assimilatory nitrate reduction Conversion of nitrate to reduced forms of nitrogen, generally ammonium, for the synthesis of amino acids and proteins. 

Reduction Conversion of Nitriles into Amines Reduction of a nitrile with LiAIH4 gives a primary amine, RNH . The reaction occurs by nucleophilic addition of hydride ion to the polar C=N bond, yielding an imine anion, which still contains a C=N bond and therefore undergoes a second nucleophilic addition of hydride to give a dianion. Both monoanion and dianion intermediates are undoubtedly stabilized by Lewis acid-base complexafion to an aluminum species, facilitating the second addition that would otherwise be difficult Protonation of the dianion by addition of water in a subsequent step gives the amine. 

Iodination reagents combined with aryl phosphines and imidazole can also effect reductive conversion of diols to alkenes. One such combination is 2,4,5-triiodoimidazole, imidazole, and ttiphenylphosphine.297 These reagent combinations... 

The steps in the hydroformylation reaction are closely related to those that occur in the Fischer-Tropsch process, which is the reductive conversion of carbon monoxide to alkanes and occurs by a repetitive series of carbonylation, migration, and reduction... 

An analogy at least formally valid can be seen in the reductive conversion of cyclopropenone to hydroquinone occuringwith l%Na-amalgam201. ... 

The acceptor strength is quantitatively evaluated by the energetics of the reductive conversion of an organic acceptor (A) to its anion radical (A- ) and it is most readily evaluated in solution (Table 4) by the reversible potential E for one-electron reduction,63 i.e.,... 

The use of trimethylsilyl-based electrophilic catalysts with organosilicon hydrides also promotes the conversion of aldehydes into ethers and avoids the need to employ the potentially hazardous trityl perchlorate salt.314,334,338 One reagent pair that is particularly effective in the reductive conversion of aldehydes into symmetrical ethers is a catalytic amount of trimethylsilyl triflate combined with either trimethylsilane, triethylsilane, PMHS,334 or 1,1,3,3-tetramethyldisiloxane (TMDO, 64) as the reducing agent (Eq. 179).314 Either... 

Data reduction Conversion of raw analytical data to useable information Peak integration, spectrum analysis... 

Yields of the arenes from the hydrazines are variable and generally low (<40%) for simple aryl compounds, although acceptable yields (50-90%) are obtained for the 7t-electron-deficient heteroaryl derivatives. In this respect, the procedure has some utility, as the more usual reductive conversion of haloheteroarenes into the parent... 

Reductive conversion of allylic nitro compounds into conjugated oximes... 

A major challenge in chemical and food industry is to perform oxidative and reductive conversions by biological means. In the application of enzymes for oxidative or reductive conversions a coenzyme like NAD(P)H or FADH2 is needed. For two... 

A useful method for the reductive conversion of elemental tellurium into Te anions employs complex hydrides such as sodium or potassium borohydride and tetraalkyl ammonium borohydride as reducing agents. 

The review by Trewhella and Grint points out that a factor import in the ability of organic sulfur to enhance liquefaction is the reductive conversion of sulfur functional groups to H2S (. As the relative concentration of H2S increases, improvements are observed in both liquefaction rates and conversions (25). 

Iodination reagents combined with aryl phosphines and imidazole can also effect reductive conversion of diols to alkenes. One such combination is 2,4,5-triiodoimidazole, imidazole, and triphenylphosphine.215 These reagent combinations are believed to give oxyphosphonium intermediates which then serve as leaving groups, forming triphenylphosphine oxide as in the Mitsunobu reaction (see Section 3.2.4). The iodide serves as both a... 

In this scheme veratryl alcohol was viewed to be metabolized by the combined action of oxidative systems (the lignin peroxidase and possibly other active oxygen species) and reductive conversions (aldehyde and quinone reductions). A possible route via veratric acid was discounted because both veratraldehyde and veratric acid were not substrates for the lignin peroxidase under the condition studied. However, both veratraldehyde and veratric acid were rapidly and quantitatively reduced by ligninolytic cultures of P. chrysosporium (21). 

In searching for chemical methods of destroying organic pollutants, chemists tend to look to oxidative methods, since the preferred end product is usually C02, but, as discussed below, special methods are usually necessary to bring about oxidation to acceptable products. In 1995, however, it was shown that elemental (zero-valent) metals such as ordinary iron filings can be effective in the reductive conversion of halocarbon pollutants such as trichloroethene in wastewater to innocuous hydrocarbons over a few days14 ... 

NOx reduction conversions met in the DOC are quite low. Excess of air in burned lean fuel mixture results in excess of oxygen in the exhaust. Under such conditions, the reducing components naturally present in diesel exhaust (CO, H2 and HC) are readily oxidized by the excessive oxygen and NOx remains unreduced. However, the unburned hydrocarbons still exhibit a certain activity for NO reduction on NM/y-Al203 and NM/zeolites catalysts under lean conditions (HC-SCR). Many efforts have been put into the investigation of different NM-based or alternative catalysts tailored for the HC-SCR reaction and the development of reliable reaction mechanisms—cf., e.g., Joubert et al. 

Reductive conversion of hydroxymethyl to methyl during the catalytic hydrogenation of 6- and 7-hydroxymethylpterins (e.g. 703 — 706) probably involves H20 elimination from the intermediate 5,8-dihydro species (704) and subsequent reduction of the C = C and C = N bonds in (705) (B-89MI 718-02). 

Oxazines, which are readily prepared from enamines and a-bromokctoximes, are reductively converted to pyrroles in good yields by iron carbonyls (Scheme 116) (81CL869). The reductive conversion of cinnolines to indoles or indolines (71JCS(C)3088> and of phthalazines to isoindoles or phthalimidines (70ACS1867) may occasionally be of synthetic value. 

In general, any reaction which results in the addition of two hydrogen atoms across a jt bond of any type are reductions. Conversions of aldehydes and ketones... 

Several studies have been made of the effect of added metal ions on the pinacol/alcohol ratio. Addition of antimony(m) chloride in catalytic amounts changes the product of the electrochemical reduction of acetophenone in acidic alcohol at a lead electrode from the pinacol in the absence of added metal salt to the secondary alcohol in its presence53. Antimony metal was suspected to be an intermediate in the reduction. Conversely, addition of Sm(in) chloride to DMF solutions of aromatic aldehydes and ketones54 and manganese(II) chloride to DMF solutions of hindered aromatic ketones55 results in selective formation of pinacols in excellent yields. When considering these results one should keep in mind the fact that aromatic ketones tend to form pinacols in DMF even in the absence of added metal ions1,29,45. 

Nishimoto S, Ide H, Nakamichi K, Otsuki N, Kagiya T (1983c) Radiation-induced reductive conversion of 5-bromo-6-hydroxythymine to thymine promoted by transition metal salts in deaerated aqueous solution. Chem Lett 1441-1444... 

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