Photolytic reduction

Amine oxides, prepared to protect tertiary amines during methylation and to prevent their protonation in diazotized aminopyridines, can be cleaved by reduction (e.g., SO2/H2O, 1 h, 22°, 63% yield H2/Pd-C, AcOH, AC2O, 7 h, 91% yield Zn/HCl, 30% yield). Photolytic reduction of an aromatic amine oxide has been reported [i.e., 4-nitropyridine A-oxide, 300 nm, (MeO)3PO/CH2Cl2, 15 min, 85-95% yieldl. ... 

Disulfur decafluoride, S2F10, is obtained as a byproduct of the direct fluorination of sulfur to SFg but is somewhat tedious to separate and is more conveniently made by the photolytic reduction of SCIF5 (prepared as above) ... 

The photolytic reduction of N2 at TiO -suspensions was at first reported by Schrauzer et al. Small amounts of NH3 and N2H4 were obtained as products. The highest activity was found with anatase containing 20-30 % rutile. Very low yields were also obtained with p-GaP electrodes under illumination It is much easier to produce NH3 from NO -solutions at CdS- and Ti02-particles using S -ions as hole scavengers . Efficiencies are not reported yet. Recently the formation of NH3 from NO was observed at p-GaAs electrodes under illumination. In this case NH3-formation was only found in the presence of transition metal ions or their complex with EDTA. 

Another possible route for reduction of the iron center is photoreduction. This has been studied in a variety of marine siderophore systems, such as aquachelin, marinobactin, and aerobactin (2), where it was demonstrated that photolytic reduction was due to a ligand-to-metal charge transfer band of the Fe(III)-siderophore complex, eventually resulting in reduction ofiron(III) and cleavage of the siderophore (31,154,155). This suggests a possible role for iron reduction in iron release (71,155). 

A photolytic reduction of the 5-chloro-substituted tetrazolo[l,5- ]pyridine derivative 60 was observed by Dias et al. <1996JHC1035> (Scheme 17). These authors found that the photolysis of the starting compound 60 when carried out with unfiltered light followed an unusual pathway instead of a ring-enlargement reaction experienced with use of Pyrex filter in many cases, a photolytic reduction takes place in 44% yield, and the chlorine substituent is replaced by... 

There are several synthetic pathways that permit the synthesis of undecanuclear clusters. The reduction of the mononuclear precursor [AuI(PPh3)] or the dinuclear precursor [Au2X2(BINAP)] with NaBH4 leads to clusters [ ( 3)713] [28] and [Aun(BINAP)4X2] [29] (X = C1 or Br BINAP = 2,2 -bis(diphenylphosphino)-1,1 -binaphthyl), respectively reaction of gold vapor with complex [Au(SCN)(PPh3)] in ethanol leads to cluster [Auu(PPh3)7(SCN)3]3+ [30] the photolytic reduction of... 

Photolytic reduction of a toluene solution of a chlorobis(amido)arsane, as shown in Equation... 

Note that in the C204 reactant, C is in the +3 oxidation state, whereas in the C20 product it is +7/2. Thus, it underwent oxidation in order to reduce Fe(III) to Fe(II). This Fe(II) can (in the presence of H202) generate the potent OH radicals. This is called the Fenton reaction, and when the Fe(II) is produced by the photolytic reduction of Fe(III), it is called a photo-Fenton reaction (see Section 10.1.1.2). 

Photolytically, reduction of SF5CI with H2 gives the largest known binary sulfur fluoride, disulfur decafluoride. It is also a trace by-product of the industrial preparation of SFe, but it is not isolated and is destroyed by heating to 400 °C. Disulfur decafluoride is a liquid at room temperature that will completely decompose at 200 °C to SF4 and SFe. It is intermediate in properties when compared to SF4 and SFe. It is not hydrolyzed by water alone, but it is slowly attacked by aqueous NaOH. Disulfur decafluoride can be stored at room temperature as a liquid for years. Like SF4, it is extremely... 

The nse of polysnlfide complexes in catalysis has been discnssed. Two major classes of reactions are apparent (1) hydrogen activation and (2) electron transfers. For example, [CpMo(S)(SH)]2 catalyzes the conversion of nitrobenzene to aniline at room temperature, while (CpMo(S))2S2CH2 catalyzes a number of reactions snch as the conversion of bromoethylbenzene to ethylbenzene and the rednction of acetyl chloride, as well as the rednction of alkynes to the corresponding cw-alkenes. Electron transfer reactions see Electron Transfer in Coordination Compounds) have been studied because of their relevance to biological processes (in, for example, ferrodoxins), and these cluster compounds are dealt with in Iron-Sulfur Proteins. Other studies include the use of metal polysulfide complexes as catalysts for the photolytic reduction of water by THF and copper compounds for the hydration of acetylene to acetaldehyde. ... 

Perfluorinated ketones form stable hydrates, (Rp)2C(OH)2, and these diols are very acidic. Hexafluoroacetone hydrate is known to be a very good solvent and is particularly useful for certain polymers [112, 152]. Perfluoropinacol may be obtained from hexafluoroacetone by photolytic reduction (Figure 8.44), whilst classical reduction with magnesium amalgam gives only low yields [112]. The same pinacol is also obtained by heating 8.44A, which is produced as shown in Figure 8.44 [153]. 

Tripathy, Sahoo, and Patnaik have reduced alcoholic solutions of uranyl compounds photochemically, but the photolytic reduction is not complete in a reasonable time, and the products are partially hydrolyzed and/or hydrated. A large amount of acetic anhydride is required for complete conversion of the oxide acetate into the desired product and subsequent recovery. Oxide oxalate and oxalate can, however, be prepared by the addition of oxalic acid to the reduced aqueous solutions. The method reported below is unique in the sense that reduction is complete in a fairly short time and the yield is almost quantitative. Two alternative procedures are outlined. 

DIBAL-H/n-butyllithium, in cyclic and acyclic systems with iron pentacarbonyl, in cyclodecanes with lithium dihydrodimethoxyaluminate(III)/copper(I) iodide, and in cyclohexane and cyclopentane systems with NaH/sodium r-butylpentyl/Ni(OAc)2. ° The monoreduction of 1,3-diketones can be carried out under similar conditions, as illustrated by the reaction of a substituted cyclohexane-1,3-dione with oxalyl chloride to give the corresponding 1-chlorocyclohexenone, which was subsequently reduced to the enone with zinc-silver couple (Scheme 45). Kropp et al. have reported the photolytic reduction of vinyl iodides in acyclic systems however, when an a-hydrogen is present, formation of the diene product is a limiting side reaction (Scheme 46). For a more extensive discussion of vinyl halide reductions, see the preceding chapter in this volume. 

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