Reduction unsaturated aliphatic

Formic acid is a good reducing agent in the presence of Pd on carbon as a catalyst. Aromatic nitro compounds are reduced to aniline with formic acid[100]. Selective reduction of one nitro group in 2,4-dinitrotoluene (112) with triethylammonium formate is possible[101]. o-Nitroacetophenone (113) is first reduced to o-aminoacetophenone, then to o-ethylaniline when an excess of formate is used[102]. Ammonium and potassium formate are also used for the reduction of aliphatic and aromatic nitro compounds. Pd on carbon is a good catalyst[103,104]. NaBH4 is also used for the Pd-catalyzed reduction of nitro compounds 105]. However, the ,/)-unsaturated nitroalkene 114 is partially reduced to the oxime 115 with ammonium formate[106]... 

A method for the conversion of unsaturated aliphatic aldehydes to saturated aldehydes is a gentle catalytic hydrogenation. Palladium is more selective than nickel. Hydrogenation over sodium borohydride-reduced palladium in methanol at room temperature and 2 atm reduced crotonaldehyde to butyralde-hyde but did not hydrogenate butyraldehyde [57]. Nickel prepared by reduction with sodium borohydride was less selective it effected reduction of crotonaldehyde to butyraldehyde but also reduction of butyraldehyde to butyl alcohol, though at a slower rate [57]. Hydrogenation of 2,2,dimethyl-... 

Reduction of unsaturated aliphatic aldehydes to saturated alcohols was... 

The immense number of reductions performed on ketones dictates subdivision of this topic into reductions of aliphatic, alicyclic, aromatic and unsaturated ketones. However, since differences in behavior toward reduction are very small between aliphatic and alicyclic ketones the section on reductions of alicyclic ketones includes only specific examples due to stereochemistry of the ring systems. 

The principal transformations of caffeic acid mediated by microorganisms are reduction of the unsaturated aliphatic side chain, dehydroxylation, and decarboxylation. 

The reduction of oleic acid to stearic acid by this method is of technical importance and is one example of the reduction of unsaturated aliphatic acids to the corresponding saturated acids. 

The following tables are intended to include all the reductions with aluminum alkoxides which were reported prior to February, 1943, although some examples doubtless have been overlooked. Table I lists the reduction of aldehydes, which have been subdivided into (a) aliphatic aldehydes and (b) alicyclic and aromatic aldehydes. Table II lists the reduction of ketones, which have been classified as (a)-satu-rated and unsaturated aliphatic ketones, (b) aromatic ketones, (c) alicyclic ketones, (d) unsaturated alicyclic and aromatic ketones, (e) a- — halogen substituted ketones, (f) diketones, (g) protected diketones, (h) alcoholic and phenolic ketones (and ethers or esters of these), and (i) keto esters. 

A facile synthesis of cyclic alkylsilanes consisting in the electrochemical reduction of aliphatic dibromides in the presence of polychlorosilanes of the formula R SiCl4 ( = 0, 2) affords heterocyclic compounds in good yields <1995JOM213>. According to the procedure described in Equation (8), the compound 26 was obtained in 57% yield. In contrast to nonelectrochemical methods, which are based on the ring closure of terminal unsaturated compounds, the electrochemical route is claimed to be more efficient and selective. 

Bis(N-inethylpiperazinyl)aluniinum hydride (li. This hydride was originally prepared from aluminum hydride and N-methylpiperazine, and was used to reduce carboxylic acids directly to aldehydes. It can be prepared more conveniently from lithium aluminum hydride and the amine. It is useful for reduction of aliphatic and aromatic acids to aldehydes (80-95% yield). Significantly, it reduces a,p-unsaturated acids to aldehydes without reduction of the double bond (70-80% yield). ... 

Generation of Carbonyl Radical Ions by Electron Transfer 459 Table 2. Reduction potentials of some saturated and unsaturated aliphatic aldehydes and ketones. ... 

Similar studies carried out on the reduction of unsaturated aliphatic acids also show that rhodium and palladium function differently. In Tables III and IV data are presented on the reduction of various acids with these catalysts. With palladium it is noted that the rate of hydro-... 

The microbiological reductions of saturated and unsaturated aliphatic ketones and aldehydes have been studied since the early 1900s. One of the first reactions to be described was the reduction of citronellal to citronellol226. 

Investigation of the reduction of unsaturated aliphatic aldehydes of general formula CHsiCH = CH)nCHO has shown [54] that, under conditions where the reaction products have minimum hindering effect (at very low depolarizer concentrations, short drop times, and large... 

Interestingly enough, no reduction of aliphatic, unactivated nitro compounds seems to occur although the reduction of aromatic nitro compounds by BY is well documented [47,161,162] a few examples for the reduction of ketones containing an additional nitro moiety have been reported. However, these reactions gave only low yields of the desired hydroxy nitroalkanes [163,164]. Better results have been obtained using the masked amino ketones 122 (Fig. 34) to afford the (5 )-configurated alcohols 123. a,P-Unsaturated nitroal-kenes 124 were reduced with moderate to excellent e.e. to afford nitroalkanes 125. 

Excellent yields of the oximes of phenylacetaldehydes are obtained by reduction of 6-nitrostyrenes over Pd-on-C in a pyridine solvent (74,75). The technique gives yields of only about 60% when applied to aliphatic unsaturated nitrocompounds better yields are obtained in acidic media(6 5). Over 5% Rh-on-Al203 in ethanol-acetic acid-ethyl acetate, 2- 6-dinitro-styrenes are converted to 2-nitrophenylacetaldehyde oximes (13). 

A reiterative application of a two-carbon elongation reaction of a chiral carbonyl compound (Homer-Emmonds reaction), reduction (DIBAL) of the obtained trans unsaturated ester, asymmetric epoxidation (SAE or MCPBA) of the resulting allylic alcohol, and then C-2 regioselective addition of a cuprate (Me2CuLi) to the corresponding chiral epoxy alcohol has been utilized for the construction of the polypropionate-derived chain ]R-CH(Me)CH(OH)CH(Me)-R ], present as a partial structure in important natural products such as polyether, ansamycin, or macro-lide antibiotics [52]. A seminal application of this procedure is offered by Kishi s synthesis of the C19-C26 polyketide-type aliphatic segment of rifamycin S, starting from aldehyde 105 (Scheme 8.29) [53]. 

An unusual reaction was been observed in the reaction of old yellow enzyme with a,(3-unsat-urated ketones. A dismutation took place under aerobic or anaerobic conditions, with the formation from cyclohex-l-keto-2-ene of the corresponding phenol and cyclohexanone, and an analogous reaction from representative cyclodec-3-keto-4-enes—putatively by hydride-ion transfer (Vaz et al. 1995). Reduction of the double bond in a,p-unsaturated ketones has been observed, and the enone reductases from Saccharomyces cerevisiae have been purified and characterized. They are able to carry out reduction of the C=C bonds in aliphatic aldehydes and ketones, and ring double bonds in cyclohexenones (Wanner and Tressel 1998). Reductions of steroid l,4-diene-3-ones can be mediated by the related old yellow enzyme and pentaerythritol tetranitrate reductase, for example, androsta-A -3,17-dione to androsta-A -3,17-dione (Vaz etal. 1995) and prednisone to pregna-A -17a, 20-diol-3,ll,20-trione (Barna et al. 2001) respectively. 

Silyl(pinacol)borane (88) also adds to terminal alkenes in the presence of a coordinate unsaturated platinum complex (Scheme 1-31) [132]. The reaction selectively provides 1,2-adducts (97) for vinylarenes, but aliphatic alkenes are accompanied by some 1,1-adducts (98). The formation of two products can be rationalized by the mechanism proceeding through the insertion of alkene into the B-Pt bond giving 99 or 100. The reductive elimination of 97 occurs very smoothly, but a fast P-hydride elimination from the secondary alkyl-platinum species (100) leads to isomerization to the terminal carbon. 

Acroleins and u,(i-unsaturated ketones are coupled with aliphatic aldehydes in the Cr-catalyzed diastereoselective coupling in the presence of Mn and MesSiCl [60]. As shown in Scheme 24, the generated radical species undergoes the further one-electron reduction to afford the corresponding al-lylchromium 41, which reacts with the aldehyde to give the corresponding... 

Fatty acids have also been converted to difunctional monomers for polyanhydride synthesis by dimerizing the unsaturated erucic or oleic acid to form branched monomers. These monomers are collectively referred to as fatty acid dimers and the polymers are referred to as poly(fatty acid dimer) (PFAD). PFAD (erucic acid dimer) was synthesized by Domb and Maniar (1993) via melt polycondensation and was a liquid at room temperature. Desiring to increase the hydrophobicity of aliphatic polyanhydrides such as PSA without adding aromaticity to the monomers (and thereby increasing the melting point), Teomim and Domb (1999) and Krasko et al. (2002) have synthesized fatty acid terminated PSA. Octanoic, lauric, myristic, stearic, ricinoleic, oleic, linoleic, and lithocholic acid acetate anhydrides were added to the melt polycondensation reactions to obtain the desired terminations. As desired, a dramatic reduction in the erosion rate was obtained (Krasko et al., 2002 Teomim and Domb, 1999). 

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