Schenk reaction

A further interesting extension of the allyl alcohol epoxidation reaction is the metal-catalyzed direct hydroxy-epoxidation of alkenes. In such a reaction an ene reaction with singlet oxygen, 02, or Schenk reaction forming an ally lie hydroperoxide is combined with metal-catalyzed intramolecular epoxidation to form epoxy alcohols For example, with 2,5-dimethyl-2,4-hexadiene (83) two different isomers, 84 and 85, were obtained with Ti(OPr-/)4 and VO(acac)2, respectively (equation 16). Similar reactions were also car-... 

The degradation of nicotine has been examined extensively in Arthrobacter nicotinovorans (oxydans) in which it is mediated by a plasmid (Brandsch et al. 1982 Schenk et al. 1998). In strain P34, the hrst metabolite was 6-hydroxynicotine, and experiments with 02 and H2 0 showed that the oxygen in the hydroxyl group was derived from H2O (Hochstein and Dalton 1965). Nicotine dehydrogenase has a molecular mass of 120,000 and contains FAD, Mo, Fe, and acid-labile sulfur (Freudenberg et al. 1988). Degradation involves a series of reactions ... 

In natural processes, metal ions are often in high oxidation states (2 or 3), whereas in chemical systems the metals are in low oxidation states (0 or 1). This fact inverts the role of the metal center, such that it acts as a one-electron sink in a natural system, but as a nucleophile in an artificial ones (see other chapters of this book and the review by Aresta et al. [109]). Nevertheless, important biochemical processes such as the reversible enzymatic hydration of C02, or the formation of metal carbamates, may serve as natural models for many synthetic purposes. Starting from the properties of carbonic anhydrase (a zinc metalloenzyme that performs the activation of C02), Schenk et al. proposed a review [110] of perspectives to build biomimetic chemical catalysts by means of high-level DFT or ah initio calculations for both the gas phase and in the condensed state. The fixation of C02 by Zn(II) complexes to undergo the hydration of C02 (Figure 4.17) the use of Cr, Co, or Zn complexes as catalysts for the coordination-insertion reaction of C02 with epoxides and the theoretical aspects of carbamate synthesis, especially for the formation of Mg2+ and Li+ carbamates, are discussed in the review of Schenk... 

Spreng M, Cotecchia S, Schenk F (2001) A behavioral study of am adrenergic receptor knockout mice increased reaction to novelty and selectively reduced learning capacities. Neurobiology of learning and memory 75 214-29... 

To examine the viability of CIM a number of photoreactions (electrocyclic reactions, Zimmerman (di-n) reaction, oxa-di-7i-methane rearrangement, Yang cyclization, geometric isomerization of 1,2-diphenyl-cyclopropane derivatives, and Schenk-ene reaction) which yield racemic products even in presence of chiral inductors in solution have been explored (Sch. 40) [187,189-200]. Highly encouraging enantiomeric excesses (ee) on two photoreactions within NaY have been obtained photocyclization of tropolone ethylphenyl ether (Eq. (1), Sch. 40) and Yang cyclization of phenyl benzonorbornyl ketone (Eq. (3), Sch. 40). The ability of zeolites to drive a photoreaction that gives racemic products in solution to ee >60% provides... 

Schenk et al. have used the a-chloro nitroso compound 93 for the reaction with cyclopentene 98 in order to solve the problem with the instability of the allyl amine product formed from the reaction with nitroso compounds [56c]. The product formed, 99, rearranges to the stable nitrone hydrochloride salt 100, which is easily hydrolyzed to the hydroxylamine 101 (Eq. (23)). 

The main methodologies developed until now for enantioselective oxidation of sulfides are effective only in the oxidation of alkyl aryl sulfoxides. Dialkyl sulfoxides on the other hand are generally oxidized with only poor selectivity. In an attempt to solve this problem, Schenk s group69 recently reported a stereoselective oxidation of metal-coordinated thioethers with DMD. The prochiral thioether is first coordinated to a chiral ruthenium complex by reaction with the chloride complexes [CpRu[(S,S)-chiraphos]Cl], 36. Diastereoselective oxygen transfer from DMD produces the corresponding sulfoxides in high yield and selectivity. The chiral sulfoxides 37 are liberated from the complexes by treatment with sodium iodide. Several o.p. aryl methyl sulfoxides have been obtained by this method in moderate to high ee (Scheme 12). 

A. Horn, A. Schenk, J. Biener, B. Winter, C. Lutterloh, M. Wittmann, J. Kiippers H atom impact induced chemical erosion reaction at C H film surfaces. Chem. Phys. Lett. 231, 193 (1994)... 

Emanuel et al. °, recorded an absorption spectrum during the course of the reaction and observed the same spectrum reported earlier by Schenk from an electric discharge through a mixture of SO2 and sulfur. Agreeing with Schenk, they ascribed the spectrum to the SO soecies or its dimer, S2O2 and proposed it was formed in what they called an elementary reaction... 

A52. A. Schonberg, G. O. Schenk, and O.-A. Neumuller, Preparative Organic Photochemistry, 2nd ed. Springer, Berlin, 1968. Chapter 45, pp. 459-470 Photochemical formation and reactions of organometallic compounds. 

The reactions of aliphatic and aromatic amines with the trimeric chloride have been studied by Schenk (70) and by Bode, et al. (14), who give details of the preparation of the dichlorotetraanilide, the hexa-p-toluidide, the hexapiperidide, the tetrachloro-bis-dimethylamide and the corresponding compound with ethylenediamine. The tetrachloro-... 

According to Schenk, Semiller and Falcke (Ber, 40, 1708, 1906), the equilibrium pressure of carbon monoxide for the reaction—... 

Schenk H.J., Horsfield B. (1998) Using natural maturation series to evaluate the utility of parallel reaction kinetic models an investigation ofToarcian shales and Carboniferous coals, Germany. Org. Geochem. 29, 137—54. 

Stibine, Antimony hydride. HjSb mol wt 124.78. H 2 42%.. Sb 97.57%.. SbH,. Conveniently prepd by dissolving zinc-antimony or magaesium -antimony alloy in dil HC1 Hurd, Chemistry of the Hydrides (Wiley. New York, 1952) p 132. Detailed directions (including prepn of the alloy from powdered Sb and Mg) Schenk in Handbook of Preparative Inorganic Chemistry voL 1, O. Brauer, Ed. (Academic Press, New York. 2nd ed.. 1963) pp 606-608. Review of preparative methods Jolly, Norman, Hydrides of Groups IV and V in Preparative Inorganic Reactions vnl. 4, W. L. Jolty, Ed. (Interscience, New York, 1968) pp 1 -58. 

Reh, Laux, Schenk 1992 50(11 m/39 f) neurotic depression, brief depressive reaction or depressive disorder not elsewhere classified [1CD-9 300.4, 309.0, 311.0] Neuroplant" 2 capsules 8 weeks A all randomized patients (Hyp 25, Pic 25) R HAMD decrease in mean total score from approx. 19 to 7 (placebo approx. 20 to 11.5) response rate (decrease in total score >50% or total score <10%) 80% (placebo 40%), p<0.05 (Chi-square test) HAMA decrease in mean total score from approx. 28 to 10 (placebo approx. 30 to 19) D-S decrease in median score from 30 to 9 (placebo 32 to 22) CGI-change 90% of patients improved (placebo 55%)... 

Thermal loss of sulfur dioxide, i.e. desulfonylation to form a carbene and sulfur dioxide, was originally put forward by Wedekind and Schenk in 1911 to explain the formation of stilbene in the reaction of phenylmethanesulfonyl chloride with triethylamine5. As we have already recounted, another mechanism is much more likely for that transformation, but... 

P. W. Schenk 106) studied the reaction between OSCl2 and NH3 in the gas phase at low temperature. He obtained a product which was colorless and solid below —85° and melted at about —85° to a colorless liquid with an appreciable vapor pressure at —70°. Analysis and vapor density determinations indicated the formula OSNH, and one can assume with some certainty that this volatile substance is a true analog of sulfur dioxide with the structure (XLVIII). 

An apparatus for liquid—liquid NH3 reactions srielding solid precipitates is describedby Schwarz and Schenk and also by Schwarz and Jeanmaire [10]. 

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