Oxidation with lead tetraacetate. IV. Cyclization of phenylhydrazones of levulinic acid, levulinanilide, 5-ketohexanoic acid, 4-keto-1-pentanol, and of levulinic acid oxime

Gubelt, Gertfried; Warkentin, John

doi:10.1139/v69-663

Cited by 10 publications

(6 citation statements)

References 2 publications

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“…Acyloxy nitroso compounds (Scheme 1) have been reported by several research groups. [25][26][27][28][29][30][31][32][33][34] Although Rehse and Herpel showed these compounds inhibit platelet aggregation and thrombus formation (indicative of NO release), they generate only small amounts (<1%) of NO and HNO (judged by N 2 O formation) under neutral conditions. 32 We propose that hydrolysis of the acyl portion of these molecules will generate an unstable intermediate that decomposes to HNO and the corresponding ketone (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Hydrolysis of Acyloxy Nitroso Compounds Yields Nitroxyl (HNO)

et al. 2006

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Nitroxyl (HNO/NO(-)), the reduced form of nitric oxide, has gained attention based on its separate chemistry and biology from nitric oxide. The inherent reactivity of HNO requires new and mechanistically unique donors for the detailed study of HNO chemistry and biology. Oxidation of cyclohexanone oxime with lead tetraacetate yields 1-nitrosocyclohexyl acetate, whereas oxidation of oximes in the presence of excess carboxylic acid gives various acyloxy nitroso compounds. These bright blue compounds exist as monomers as indicated by their infrared, proton, and carbon NMR spectra, and X-ray crystallographic analysis reveals the nitroso groups possess a "nitroxyl-like" bent configuration. Hydrolysis of these compounds produces nitrous oxide, the dimerization and dehydration product of HNO, and provides evidence for the intermediacy of HNO. Both thiols and oxidative metal complexes inhibit nitrous oxide formation. Hydrolysis of these compounds in the presence of ferric heme complexes forms ferrous nitrosyl complexes providing further evidence for the intermediacy of HNO. Kinetic analysis shows that the rate of hydrolysis depends on pH and the structure of the acyl group of the acyloxy nitroso compound. These compounds relax pre-constricted rat aortic rings similar to known HNO donors. Together, these results identify acyloxy nitroso compounds as a new class of HNO donors.

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Section: Introductionmentioning

confidence: 99%

Hydrolysis of Acyloxy Nitroso Compounds Yields Nitroxyl (HNO)

et al. 2006

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“…It is unclear whether the oxidation occurs by coordination of the lead oxidant to the oxygen of the hydroxyl group or to the NH function (or either) of 7. We have postulated intermediates analogous to 10 previously [3] and adherence to that mechanism would have 4, 8 and 11 formed according to Scheme 4. Possible mechanisms of formation of 9 are discussed below.…”

Section: Resultsmentioning

confidence: 80%

“…A similar, but less likely, process could begin with the lead function attached to the hydroxyl oxygen (14), Scheme 5. It is less likely because the favored configuration of 14 is expected to be one that would keep the CO 2 Me group remote from the OPb(OAc) 3 group but formation of a 7-membered intermediate, such as 15, from 10 could possibly be involved. The postulated species 13 is (www.interscience.wiley.com) DOI 10.1002/poc.1280 at the right oxidation state to lead to 9, but the steps that would take it there are purely speculative, Scheme 5.…”

Section: Resultsmentioning

confidence: 99%

6,7‐diaza‐1‐methoxy‐ 5‐methyl‐2, 8‐dioxabicyclo[3.2.1]oct‐6‐ene. An unstable bicyclic precursor of a dioxa carbonyl ylide and carbenes by ylide ring opening

Czardybon¹,

Sokół²,

Warkentin³

2007

J of Physical Organic Chem

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Synthesis of a bicyclic 2,2-dioxa oxadiazoline (6,7-diaza-1-methoxy-5-methyl-2,8-dioxabicyclo[3.2.1]oct-6-ene) is reported. Its thermolysis at 27-C is about 200 times as fast as the thermolysis of a monocyclic oxadiazoline model system. Presumably, a cyclic dioxa carbonyl ylide is formed initially and the ylide then undergoes a bond scission to afford either a dioxacarbene or a dialkylcarbene or it cyclizes to an oxirane. A small fraction of a dialkylcarbene was trapped as the product of addition to dimethyl acetylenedicarboxylate (DMAD). Computations of the barriers to the loss of N 2 from the oxadiazolines and to the formation of the carbenes from the carbonyl ylide resulting from thermolysis of the bicyclic oxadiazoline are compared to corresponding barriers for a similar monocyclic oxadiazoline. The rate acceleration is accounted for in terms of geometric factors. The complex products from the decomposition of the bicyclic oxadiazoline were not studied.

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“…218 Oxidative cyclization of the oxime of levulinic acid (145) to the 7-nitroso-7-valerolactone dimer (146) occurs on oxidation with LTA in a reaction similar to the oxidative cyclization of the corresponding phenylhydrazone. 179 2. Aromatic and ,ß-Unsaturated Ketoximes LTA oxidation of aromatic ketoximes does not proceed via a single pathway.…”

Section: Cmementioning

confidence: 99%