Miscellaneous Reductions

A laser flash photolysis examination of the behaviour of fine particles of C o when irradiated in the presence of an electron donor has shown that photo-induced electron transfer occurs. The photoexcited triplet state of is reported to be capable of abstracting both an electron and energy from P-carotene, and the partitioning of the two routes is dependent on solvent polarity. Photoinduced electron transfer from NADH and its dimeric analogues to Cso yields Cgo However, if 10-methyl-9,10-dihydroacridine is used as 

Photolysis of solutions of C6o(OH)ig at low solute concentration leads to [C6o(OH)i8] by electron transfer from Me2C(OH) radicals or from hydrated electrons, and this has enabled the reduction potential of the C6o(OH)ig/ [C6o(OH)ig] couple to be estimated. The kinetics of the photoreduction of hexanal using RhCl(PMe3)2CO as catalyst have been measured and the feasibility of a photocatalytic synthesis of hexanol from pentane, CO, and H2 in the presence of rhodium complexes has been demonstrated. Irradiation of a chiral bimolecular crystal of acridine and R-(-)- or S-(+)-2-phenylpropionic acid induces photodecarboxylation followed by stereoselective condensation to give a mixture of three optically active products, and the 3-0-S-methyl dithiocarbo-nate derivatives of oleanolic and ursolic methyl esters have been used as models for the photodeoxygenation of alcohols.  

Metal Hydrides. A number of patents and publications have appeared describing the use of lithium aluminum hydride in the reduction of nitro compounds, nitriles, amides, oximes, and azides to amines. Moderate to high yields have been obtained. This process is useful in the selective reduction of compounds sensitive to catalytic hydrogenation, but is quite costly. 

Finholt and coworkers have sttidied the use of sodium aluminum hydride. With nitrobenzene, azobenzene is obtained in 78 per cent yield With nitrobutane, butylamine is Produced in 73 per cent yield. With benzonitrile, the yield of benzylamW is 92 per cent of theory. 

Brown and Subba Rao have found that sodium borohydride reduces nitriles to amines, but does not affect nitro groups or amides. 

Sodium Hydroxide and Methyl Alcohol. On reacting nitrobenzene with methanol and caustic soda, azoxybenzene is the main reduction product formed. Sodium formate is obtained as the oxidation product of the methanol used. Naphthoquinone and its substitution products are promoters of this reaction.  

Nitrobenzene can also be reduced to azoxybenzene and azobenzene with magnesium and methanol. 

HMPT has been reported to be a useful solvent for the photoreduction of esters. For example, perfluorinated esters give defluorinated esters as well as the corresponding alkeme and alkyl esters give alkanes alone,in processes which involve electron-transfer from HMPT to ester. Methanesulphonates, ROjSMeCR-S-cholesten-Sp-yl, 4,4-dimethyl-3/3-cholestanyl, 

3/3-cholestanyl, n-nonyl) can also be photoreduced in the seune solvent.Colloidal platinum catalysts have been prepared by hydrogen- and photo-reduction of chloroplatinic acid in the presence of surfactants auid these have been found to be highly active catalysts for hydrogenation of olefins. Acetone-sensitized photolysis of 1,2,3,4-, 1,2,3,5-, and 

Valence isomerisations of some norbomadienes have been photosensitised using N-methylcarbazole and evidence presented supports the view that single 

Primary, secondary, and tertiary alkyl chlorides as well as aryl chlorides undergo reductive dechlorination using Sml2, and in the presence of CO ketones are formed by photocarbonylation. °  

Photoreductive dehalogenation of the insecticide bromodan has been described 

The photocatalytic activity of transition metal oxides incorporated into the framework of zeolites, and of transition metal ions exchanged within the zeolite cavities, has been reviewed in relation to the reduction of CO2 with H2O to give CH4 and. CH30H.  

In the synthetic area there have been a number of reports dealing with the photodeoxygenation of chalcogen oxides. Thus substituted dibenzothiopenes-S-oxides (62) undergo direct and sensitized photodeoxygenation at a rate which is not simply a function of the size of the substituents. The marked difference in the reactivity of the oxygenated dibenzothiophene dimers (63) and (64) was 

N-diaethyithiocarbaaates. Solvent viscosity has been found to Influence the effect exerted by a magnetic field on radical yields during the photoreduction of xanthene dyes.  

Irradiation of aromatic hydrocarbons such as phenanthrene, anthracene, naphthalene, and certain substituted naphthalenes in the presence of NaBH4 and m- or p-(NC)2C6H4 promotes a Birch-type photoreduction.The reaction seems to occur by electron transfer from the excited singlet state of the arene to the electron acceptor giving the arene radical cations, which are then reduced by the borohydride. Other reducing agents such as NaBH, NaBHjCN, and NaBH(OMe)3 have been found to be effective and all lead to different isomer ratios. In a mechanistically related reaction, both fluoren-9-ol and the corresponding acetate are reported to be photoreduced to the parent hydrocarbon in the presence of aliphatic amines. The products arise by photoinduced electron transfer followed by proton transfer from the amine. The yield depends on the structure of the amine and increases in the order primary secondary tertiary amine. In 

Matsuo, K. Takuma, K. Itoh, and K. Sakura, Kokagaku Toronkai Koen Yoshishu, 1979, 244. 

Okutsu and M. Kobayashi, Josai Shika Daigaku Kiyo, 1979, 8, 215. 

Photo-oxidation and photoreduction of the zinc tetraphenylporphyrin radical cation have been described. The disproportionation equilibrium [equation (1)] 

The hydrogenolysis of halopyridines can be convenient when carried out with 15% aqueous TiCl in presence of acetic acid. Aqueous titanium trichloride quantitatively removes cyano group from cyanopyridines. Reductive dehalogenation is also catalysed by Sml - 

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Miscellaneous. Reduction of a palladium salt by CO is the basis of a visual test for ambient carbon monoxide (227). Palladium compounds are used as photographic sensitizers (228). The low dimensional mixed valence compound Csq 3[Pd(S2C2(CN)2)] 0.5H2O behaves as a semimetal at room temperature (229). Palladium compounds isostructural with potent platinum antitumor compounds have poor antitumor activity (230). 

Magnesium-Methanol, 170 Miscellaneous reductions Cyanotrimethylsilane, 87 Nickel boride, 197 B -3-Pinany 1-9-borabicy clo[3. 3.1 ]no-nane, 249... 

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