N-Dehydroxylation

Re2Pt(CO)n Dehydroxylated AI2O3 Adsorption from solution and thermal treatment under H2 Re4Pt2 entities, model catalyst for methylcyclohexane dehydrogenation [57, 60]... 

Liver microsomes have shown that zileuton and its N-dehydroxylated metabolite can be oxidatively metabolized by the cytochrome P450 isoenzymes 1A2, 2C9, and 3A4. Use caution when prescribing a medication that inhibits any of these enzymes. 

Machinist, J.M. Kukulka, M.J. Bopp, B.A. In vitro plasma protein binding of zileuton and its N-dehydroxylated metabolite. Clin. Pharmacokinet. 1995, 29 (suppl. 2), 34-Al. 

Masuda N, H Oda, S Hirano, M Masuda, H Tanaka (1984) 7a-dehydroxylation of bile acids by resting cells of a Eubacterium lentum-like intestinal anaerobe, strain c-25. Appl Environ Microbiol AT. 735-739. 

Gorny N, B Schink (1994a) Hydroquinone degradation via reductive dehydroxylation of gentisyl-CoA by a strictly anaerobic fermenting bacterium. Arch Microbiol 161 25-32. 

RESPONSE We have not looked at that at all. But it is surprising. 1 expected to see either hydroxylation or dehydroxylation, so 1 expected to see similar activities. But this is what we see. If you compare the activities on a milligram per kilogram basis, the N-hydroxy amphetamine appears to be equipotent. However, when you look at the molecular weights (it is a different salt), it is in fact twice as potent. 1 cannot explain that. 

Dehydroxylase Dehydroxylation of C- and N-hydroxy Bile acids, N-hydroxyfluorenyl-... 

The second approach (Equation(3)) has a number of advantages over the first one (Equation(2)). The alkyl complexes are more reactive than the related alkoxides, the latter being for group 4 elements generally associated into dimers or trimers 48 also, reaction (2) liberates an alcohol which may further react with the surface of silica, whereas the alkane ( Equation(3)) is inert. It was demonstrated by various spectroscopic techniques and elemental analysis that with a silica dehydroxylated at 500 °C under vacuum, the stoichiometry of reaction (3) corresponds to n = 1.45,46 Moreover, a better control of the surface reaction was achieved with the procedure represented in Equation(3). 

The exact nature of the alkylidenes formed on various oxide surfaces is still uncertain, as is the nature of the alkylidenes responsible for the often observed metathesis activity. Mo(N)(CH2CMe3)3 also has been employed as a precursor to a surface-bound species believed to be of the type Mo(NH)(CHCMe3)(CH2CMe3) (Osurf) [115]. Although the alkylidene carbon atom could not be observed in solid state NMR spectra, which is typical of surface supported alkylidenes, reaction with acetone to give 2,4,4-trimethylpent-2-ene quantitatively confirmed the presence of the reactive neopentylidene complex. Such species would initiate various metathesis reactions when prepared on partially dehydroxylated silica. 

Clearly, strong 0-H interaction occurs leading to dissociation of ammonia, formation of OH groups, dehydroxylation, and surface imide formation. The NH(a) species has a characteristic N(ls) value of 398 eV, i.e., 1 eV greater than N(a) and 1 eV less than NH2(a). 

The carbonyl cluster Rh,5(CO)i,5 was initially stable as such on the completely dehydroxylated alumina surface. But as soon as hydroxyl groups were generated (e.g., by adding traces of water) it decomposed to give various surface transformations. First, the cluster structure was dismpted, with breakage of the core cluster frame, into (Al-0-)(Al-0H)Rh (C0)2, Rh > monoatomic species sigma and n-bonded to the oxygens atoms of the alumina surface, with formation of molecular... 

The surface complex [=Si-NH2] can be obtained on siUca by reaction of ammonia on silicajiooo) (Scheme 2.7) [9]. The addition of ammonia on siUca, normally unable to induce N-H cleavage at room temperature, becomes possible in this case because of the drastic dehydroxylation treatment, which produces a few highly strained [=Si-0-Si=] bridges (0.15 nm ) that undergo cleavage by bimolecular oxidative addition of otherwise unreactive bonds [10-13]. 

A detailed study on the immobilization of Ln[N(SiMe3)2]3 on fumed silica showed that the nature of the grafted species is considerably affected by the thermal pretreatment of the support [117]. Whereas at low (AS-380.2so) and intermediate dehydroxylation temperatures (AS-380.5oo) mixtures of bipodal [(=SiO)2Ln N(SiMe3)2 ] and monopodal [(=SiO)Ln N(SiMe3)2 2] species prevailed... 

Surface Ln-silylamido moieties lla- obtained via grafting of homoleptic silyl-amides Ln[N(SiMe3)2]3 on dehydroxylated silica Vulkasil S (BAYER AG, a = 175 ... 

The tris-neopentyl Mo(VI) nitride, Mo(-CH2- Bu)3(=N) [134], reacts with surface silanols of silica to yield the tris-neopentyl derivative intermediate [(=SiO)Mo (-CH2- Bu)3(=NH)] followed by reductive elimination of neopentane, as indicated by labeling studies from labeled starting organometallic complex, to yield the final imido neopentylideneneopentyl monosiloxy complex [(=SiO)Mo(=CH- Bu)(-CH2 - Bu)(=NH)] [135]. The surface-bound neopentylidene Mo(VI) complex is an active olefin metathesis catalyst [135]. Improved synthesis of the same surface complex with higher catalytic activity by benzene impregnation rather than dichlorometh-ane on silica dehydroxylated at 700 °C has been reported [136],... 

Figure 13.6 (a) Mechanism for the hydroxy I ation of lysine N-methyl group leading to dehydroxylation and release of formaldehyde, succinate and CO2. 

The first route to nitrenium ions is the acid-catalyzed dehydroxylation of N-... 

The relationship between acid site density and effective acidity may account for the interesting observation of Hopkins that maximum cracking activity of n-hexane was obtained over a partially dehydroxylated hydrogen zeolite Y (45). While the normal hydrogen form would contain a greater overall concentration of acid sites, the partially dehydroxylated form may have a greater overall acid activity because of the increased effective acidity of the remaining sites. 

A summary of the weight losses ascribed to deammination and dehydroxylation of the various samples is shown in Table II. The assumption that the weight loss in the region 250-400°C observed with the NH4+-ZSM-5 is due to decomposition of NH4+, is justified by infrared spectra taken of the samples over that temperature range. As the activation temperature increases to 400°C, the spectra show a decrease in the N-H stretching bands and the growth of an OH band at 3610 cm l. 

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