Deoxygenated product

Hydrogenation of epoxides lends itself well to both synthetic applications and mechanistic studies. The reaction is complex, for either carbon-oxygen bond may break with or without inversion of configuration, and the product may contain deoxygenated products (92,93) as well as ketones derived by isomerization (26). The reaction is especially sensitive to both catalyst and environment (74). 

In a few cases, it is possible to remove an oxygen substituent directly from the aromatic ring. Treatment of an aryl mesylate (ArOMs) with a nickel catalyst in DMF, for example, leads to the deoxygenated product, Ar—H." ... 

Attempted deoxygenation of several fT-aryl thiono carbonates gave the unexpected product shown. In contrast, the corresponding a-isomers gave the desired deoxygenation product. Account for the formation of the observed products, and indicate why these products are not formed from the a-stereoisomers. 

Table 16-1. Reduction of alcohols with tri- -butyl stannane via imidazole-Y-thionocarboxylates to the corresponding deoxygenated products.

Problems of dilution and pH sensitivity have also been encountered in the synthesis of cts-[Pt(S-R2SO)(olefin)Cl2] complexes (85), where deoxygenation of the sulfoxide with concomitant oxidation of the metal center occurs at low pH. The reactions of [M(Ph2PCH2CH2PPh2)Cl2] (M = Pd, Pt) with one equivalent of silver perchlorate in the presence of Me2SO yield either the O-Me O complex or its deoxygenation product, depending upon reaction conditions. A sequence of reactions, Eq. (27), has been proposed (143). 

The deoitygenation reaction of ethyl stearate was carried out for 4-6 h at reaction temperatures between 270-360°C and under reactor pressure of 0-7 bar. The effect of the catalyst pretreatment and the catalyst mass as well as the influence of reaction temperature were studied. The observed products in the ethyl stearate reaction are the deoxygenation products (desired), intermediate product (fatty acid), hydrogenation products (unsaturated Et-SA) and by-products (Figure 3). 

As a class, the 2-azaquinoIizinium iV-oxides are of less theoretical interest than their deoxygenation products. Fortunately, Glover et al. found a satisfactory deoxygenation procedure (Section 2.10.5.3.2) (67JCS(C)239l). 

C-glycoside 21 with an additional oxygen functionality at the para-position [11c]. Hydro-genolysis of the derived triflate 22 gives the deoxygenated product 23 having a para-oxygen function (Sec. III.I) [lie]. 

Irradiation of 1,2,4-triazine 4-oxides (124) led to the deoxygenated products, and also, when position 5 was unsubstituted, to 1,2,4-triazoles (364) (76LA153). 4-Amino-l,2,4-triazin-5-ones (365) are photochemically deaminated. This has been demonstrated, in particular, with the 6-r-butyl-3-methylthio compound (8) which is used as a herbicide... 

Inokuchi, Kusumoto and Torii reported the electrochemical reduction of epoxyketone 29 at a carbon cathode (equation 16)62. In the absence of a proton source, two deoxygenated products (enone 30 and pinacol dimer 31) were produced in a combined yield of 37%. However, in the presence of a proton source (CH2(CC>2Et)2), ring-opened product 32 was produced in 65% overall yield. 

If this process seems particularly useful for small quantities of acetates some difficulties are observed for the deoxygenation of larger quantities of substrates which necessitate longer times of photolysis and leads to lower yields of deoxygenation products [81]. 

A recently reported regioselective photoreduction of benzoates by photosensitized electron transfer reaction was applied to nucleosides [85]. In presence of jV-methyl-carbazole as the electron donor sensitizer and in an isopropanol, water solution, w-trifluoromethylbenzoates of adenosine 83 or benzoates of uridine 84 give deoxygenated products in good yields (73 %). 

The photolysis of 682 in carefully dried and distilled CD2CI2 yielded a mixture of products, which is a little different in relative composition from that of the photoreaction in nondried CD2CI2. Most noticeable is the higher yield of the purely deoxygenated products, 683 (25%), and a lower yield in the total amount of hydroxylated products, 684 and 685 (27 and 12%). The formation of hydroxylated products in dried solvents, however, means that oxygen in the hydroxyl/alkoxymethyl moieties of the products stems from thiophene S-oxides. The addition of ethanol (5 equiv.) to the reaction mixture in nondried CD2C12 leads to the formation of 2-ethoxymethyl-5-... 

Controlled potential electrolysis of emmotin A 97 at —1.4 V vs. SCE furnishes the corresponding deoxygenated product, 2-deoxyemmotin A 98, in 74% yield (Scheme 3-37) 84). 

A solution of Bu3SnH (200 mg, 0.69 mmol) inp-cymene (3 ml) was added dropwise over 2 h to a solution of methyl xanthate of hederagenin (50 mg, 0.087 mmol) in p-cymene (3 ml) at 150 °C. After the addition, the mixture was stirred at the same temperature for 10 h. After the reaction, CC14 was added and the mixture was refluxed for 3 h. After removal of the solvent, molecular iodine in ether was added until the iodine color remains. Then, the solution was washed with 10% aq. KF solution (5 ml), and the organic layer was dried over Na2S04. After removal of the solvent, the residue was recrystallized to give the deoxygenated product [2]. 

When 28 was subjected to Cp2TiCl in dry THF, the allylic alcohol 29, together with the cyclization product 30 and a minor quantity of the reduction product 31, was isolated. The expected deoxygenation product 32 was not formed at all (Scheme 22) [73, 74],... 

The formation of the major product suggested that a mixed disproportionation reaction between the radical intermediate 33 and a second equivalent of Cp2TiCl had taken place [76]. This process was slightly faster than the cyclization reaction leading to 30 and much faster than the potential radical trapping by the second titanium species, which would have led to the elusive deoxygenation product 32 (Scheme 23). 

Reduction of 5,7-diaminopyrido[3,4-6]pyrazine with NaBH4 gives the 1,2-dihydro derivative whose enantiomers can be separated by reaction with (K)-1 -(1 -naphthyl)ethylisocyanate <89JMC2089, 89JMC2363). Reduction of the iV-oxides with sodium dithionate gives the deoxygenated product <92S1206>. 

Hydrogenolysis of styrene oxide in ethanol affords not 1-phenylethanol but always 2-phenylethanol, together with deoxygenated products and phenyl acetaldehyde (eq. 13.13). The hydrocarbon formed at the initial stages over Raney Ni was found to be... 

Aluminum atom reactions are relevant to interfacial chemistry associated with aluminum-polyimide junctions. Al deposited under ultra high vacuum will reduce surface carbonyl functional groups (22). MVS co-condensation experiments show that besides ketones, aldehydes and epoxides, atomic aluminum will deoxygenate ethers. Chapter 7 of the monograph by Klabunde (12) includes tables of deoxygenation products of a variety of cyclic and acyclic ketones and ethers. 

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