Oxidations pyridine

Oxidation of carbinols with chromium tri-oxide-pyridine... 

Note 2. Under acidic conditions and in the presence of water, the 18,20-hemiacetal formed from the 18-iodo-18,20-ether is transformed into a dimeric anhydro product, resistant to further oxidation. Pyridine is added to prevent this transformation. 

Ethylene sulfite is prepared from ethylene oxide, pyridine, and sulfur dioxide in excess to prevent polymerisation of ethylene oxide. Use of a deficiency of sulfur dioxide led to rupture of a reactor from that cause. 

Mudd, Mudd et Menzel, and Nasr et have reported that ozonization of aqueous solutions of NADH or NADPH results in their oxidation. However, there is a difference in their findings as to whether the resulting product is a biologically active oxidized pyridine nudeotide (NAD or NADP), as suggested by Menzel, or is molecularly disrupted to the extent that it is unable to participate in enzymatic processes. Inasmuch as more drastic effects are likely to be observed in vitroy it is more likely that oxidation of intracellular reduced pyridine nucleotides proceeds mainly to NAD or NADP after ozone inhalation but further resolution of this question would be of value. 

Nasr et failed to observe a change in the ratio of NADPH to NADP in the tracheal epithelium of rats exposed to ozone at 33 ppm for an hour. This apparently negative in vivo finding is not surprising, inasmuch as NADP will be rapidly reduced back to NADPH if ozone does not disrupt the structural integrity of pyridine nucleotides. In addition, de novo thesis of pyridine nucleotides may also occur. The intracellular ratio of reduced to oxidized pyridine nucleotides is under tine cellular control, in that the oxidation of NADPH or NADH results in the stimulation of enzymatic activity, which restores the initial ratio. In the case of NADPH, its oxidation increases the activity of the hexose monophosphate shunt this also occurs after the oxidation of glutathione. The rel-... 

The next phase focused on the goal of elaboration of the side chain in the desired sense. The primary alcohol function at C7 was unveiled by hydrogenolysis (Pd(OH)2/EtOAc-MeOH). Oxidation of the resultant compound 13 with chromic oxide pyridine afforded aldehyde 14, which was now to be elongated through some variation of a Homer-Emmons type of reaction. Shortly before tiiese investigations were launched. Still had demonstrated the use of phosphonate 15 as a device to achieve the two-carbon extension of an aldehyde to a Z-enoate (12). Happily, application of the Still method to compound 14 afforded the desired 16, mp 120-121° C, in 80% yield as a 20 1 mixture of Z E enoates. 

The oxidation of picolinaldehydes to the corresponding Af-oxides with dimethyldioxirane proceeds in good yield without the need to protect the aldehyde function <99T12557>. The urea-hydrogen peroxide complex oxidizes pyridines to pyridine Af-oxides <990L189>. 

Oxetanol can be oxidized to 3-oxetanone in fair yield by means of the chromic oxide-pyridine complex. This ketone reacts with base in an unknown manner and polymerizes on standing. 

Pentanone Petroleum distillates Phenyl ether vapor Phenyl glycidyl ether n-Propyl acetate Propyl alcohol n-Propyl nitrate Propylene dichloride Propylene oxide Pyridine... 

All of the usual chromium-based oxidation reagents that have been used for the oxidation of cyclobutanols to cyclobutanones, for example, chromium(VI) oxide (Jones reagent),302 pyri-dinium chlorochromate,304 pyridinium dichromate,307 and chromium(YI) oxide/pyridine (Collins),303 are reported to do so without any serious problems. Alternatively, tetrapropylam-monium perruthenate in the presence of A-methylmorpholine A -oxide. oxalyl chloride in the presence of triethylamine in dimethyl sulfoxide (Swern),158,309,310 or phenyl dichlorophos-phate in the presence of triethylamine and dimethyl sulfoxide in dichloromethane (Pfitzner-Moffatt),308 can be used. The Pfitzner-Moffatt oxidation procedure is found to be more convenient than the Swern oxidation procedure, especially with respect to the strict temperature control that is necessary to achieve good yields in the latter, e.g. oxidation of 1 to give 2.308... 

Osmium tetroxide-Trimeth> lamine N-oxide-Pyridine... 

Osmium tetroxide-Trimethylamine N-oxide-Pyridine, 223 Oxymercuration 1,3-Propanedithiol, 261 Oxysulfenylation... 

Trimethylsilyldiazomethane, 327 Silyl substituted arenes Bis(trimethylsilyl)acetylene, 97 Chromium carbene complexes, 82 Titanium(IV) chloride-Diethylalu-minum chloride, 309 Other organosilanes Osmium tetroxide-Trimethylamine N-oxide-Pyridine, 223 Tributyltin chloride, 315 Di- x-carbonylhexacarbonyldicobalt, 99 Trimethylsilyl trifluoromethanesul-fonate, 329... 

Osmium tetroxide-N-Methyl-morpholine N-oxide, 222 Osmium tetroxide-Trimethylamine N-oxide-Pyridine, 223 Palladium Compounds Benzylchlorobis(triphenylphosphine)-palladium(II), 30 Bis (ace tonitrile) chloronitropalla-dium(II)-Copper(II) chloride, 33 Bis(acetonitrile)dichloropalladium(II), 33, 211, 236... 

An older paper <1971MI873> reported that ozonolysis of alkenes in the presence of tertiary amines resulted in the formation of aldehydes. A recent reinvestigation <20060L3199> has shown that amine oxides were responsible for this reductive ozonolysis . Indeed, pretreatment of the tertiary amines with ozone, giving rise to amine oxides, accounted for this phenomenon. A preparative method emerged, by treating the alkene (e.g., 1-decene) at 0 °C with a solution of 2% 03/02 in dichloromethane (2 equiv of ozone relative to the alkene) in the presence of an excess (about threefold molar excess) of A-methylmorpholine A-oxide, pyridine A-oxide, or l,4-diazabicyclo[2.2.2]octane A-oxide (DABCO A-oxide). Yields of aldehydes (nonanal in the above example) were 80-96%, and the excess of amine oxide ensured the absence of residual ozonide (Scheme 21). 

Organic solvent(s)p No data Acetic acid, anisole, chloroform, o-dichlorobenzene, dioxane, diphenyl oxide, pyridine, xylene8... 

Vanadate stimulates protein kinases in the cytosol, as demonstrated in adipose cells and extracts. The activation of a membrane and cytosolic protein tyrosine kinase have been demonstrated in adipocytes, and the membranous enzyme has been postulated to be a way to involve PI-3K actions without activation of insulin receptor substrate-1 (IRS-1) in the insulin signal transduction pathway [140], It is always difficult to determine if protein kinase activation is direct or the result of stimulation of a protein phosphatase. The fact that kinase stimulation was seen in isolated extracts after cell disintegration in this adipocyte cell system supports the idea that vanadium addition to cells could directly stimulate kinases via an as-yet-undetermined mechanism. In other experiments with 3T3-L1 adipocytes bis(acetylacetonato)oxovana-dium (IV) BMOV and bis(l-N-oxide-pyridine-2thiolato)oxovanadium (TV) caused increased tyrosine phosphorylation of both the insulin receptor and IRS-1 in a synergistic way with insulin, as measured by antibodies to phosphotyrosine residues [141]. 

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