Formic acid reduction with

Formic acid has been used in a variety of rather specific reductions. Heating triphenylcarbinol (580) in formic acid, for example, led to triphenylmethane (581). 92 most common application of formic acid reduction involves enamines, presumably via conversion to an iminium salt, which is the actual species reduced 

Several modifications of this reduction involve formates and are effective for reduction of various functional groups. A mixture of formic acid and ethyl magnesium bromide was used to reduce decanal to decanol in 70% yield. Decanal was also reduced to decanol in 69% yield by using sodium formate in N-methyl-2-pyrrolidinone as a solvent. Functional groups other than carbonyl derivatives can be reduced under relatively mild conditions with formate derivatives. Ammonium formate, in the presence of palladium on carhon was used to reduce an azide to a primary amine.Aliphatic nitro compounds are also converted to an amine with this reagent. l° 

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The reduction of the double bond of an enamine is normally carried out either by catalytic hydrogenation (MS) or by reduction with formic acid (see Section V.H) or sodium borohydride 146,147), both of which involve initial protonation to form the iminium ion followed by hydride addition. Lithium aluminum hydride reduces iminium salts (see Chapter 5), but it does not react with free enamines except when unusual enamines are involved 148). 

That the reduction with formic acid proceeds by a hydride transfer reaction was proposed by Lukes and Ji2ba 100) and finally proven by Leonard and Sauers 63). The use of variously deuterated formic acid allowed Leonard and Sauers to determine that (1) protonation or... 

An interesting addition of ethyl acrylate has been reported in the case of l-methyl-2-ethylidenepyrrolidine. An unsaturated amino ketone 144 is formed, which rearranges to 1,7-dimethyloctahydroindole (145) on reduction with formic acid, as established by dehydrogenation to 1,7-dimethyl-indole (Scheme 12) 217). 

Scheme 2.26 Palladium(0)-catalyzed reduction with formic acid.

The pyridine ring is easily reduced in the form of its quaternary salts to give hexahydro derivatives by catalytic hydrogenation [446], and to tetrahydro and hexahydro derivatives by reduction with alane aluminum hydride) [447], sodium aluminum hydride [448], sodium bis 2-methoxyethoxy)aluminum hydride [448], sodium borohydride [447], potassium borohydride [449], sodium in ethanol [444, 450], and formic acid [318]. Reductions with hydrides give predominantly 1,2,5,6-tetrahydro derivatives while electroreduction and reduction with formic acid give more hexahydro derivatives [451,452]. 

But Au, Pd, Be, and Po are not among the strongly active products of U fission. Thus, Au and Fd are separated from Tm by reduction with formic acid. Be la ppted. from 12 V SCI by SQe. Te la not ppted. under these conditions. On the other hand, hydrazine HC1 ppte. Te hut not Fo. 

The main types of halocarbonyl compounds found with the heavier halogens are depicted in Scheme 7. One example has already been presented in Scheme 3. Though methods of preparation other than those shown in Scheme 7 are also successM, reduction with formic acid/hydrohalic acid gives a clear picture of the successive events leading to individual members of the series. Not all compounds listed for chlorine in Scheme 7 can be obtained for bromide and iodine, and in some cases stereoisomers are found with iodine only (cis/trans forRu(CO)4l2). 

The preparation of palladium black by reduction with formic acid has been described by Wieland.135 For preparation of he Brown catalyst see Brown and Brown (p. 40). 

Ignition of the isomers appears to result in loss of platinum, whereas reduction with formic acid or hydrazine hydrate seems incomplete. The sample is therefore boiled with concentrated sulfuric acid until the supernatant liquid becomes clear and almost colorless (about 4 hours). The residual platinum is collected on a sintered-glass funnel, washed with water, ethanol, ether, and then air-dried. Anal. Calcd. for [PtCl2 (C4H9)3P 2] Pt, 29.10. Found Pt, 29.00 (trans), 29.10 (cis). 

Lizcano-Valbuena WH, De Souza A, Paganin VA et al (2002) Performance of a DMFC using Pt-Ru/C catalysts prepared by reduction with formic acid. Enel Cells 2 159—165... 

Colmati F, Antolini E, Graizalez ER (2005) Pt-Sn/C electrocatalysts for methanol oxidation synthesized by reduction with formic acid. Electiochim Acta 50 5496-5503... 

Colmati F, Antohni E, Gonzalez ER. Ethanol oxidation on a carbon-supported Pt75Sn2s electrocatal5Tst prepared by reduction with formic acid Effect of thermal treatment. App Cat B Env 2007 73 106-15. 

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