N as catalysts

The use of Al-N as catalyst support yields interesting catalysts with improved characteristics (especially in the case of Pd/Al-N). This support proves to be an interesting variable in catalyst design. 

Eve, T.S.C., Wells, A. and Turner, N.J. (2007) Enantioselective oxidation of 0-methyl-hydroxylamines using monoamine oxidase N as catalyst. Chemical Communications, 1530-1531. 

The transition-metal-catalyzed decomposition of methyl trialkylsilyldiazoacetates 5 in the presence of styrene, hex-l-ene and cyclohexene has been studied.34,36 In all cases, where cyclopropanation occurs, the formation of the thermodynamically favored cyclopropane dia-stereomers E-6 and anti-1 are formed predominantly. The steric demand of the trialkylsilyl substituent has a relatively small influence on the diastereoselectivity on the other hand, catalytic cyclopropanation with the triisopropylsilyldiazoacetate is more difficult than with 5 (R1 = Me, Et) or fails completely. Copper(I) triflate is a more efficient catalyst for these cyclo-propanations than rhodium(II) acetate dimer and rhodium(II) bis(perfluorobutanoate) dimer the catalyst [Ru2(CO)4(/i-OAc)2]n gives somewhat better results than copper(I) triflate for hex-l-ene, but not for styrene. The catalytic cyclopropanation of cyclohexene with 5 (R1 = Me, Et) to give bicyclo[4.1.0]heptanes 7 succeeds only with [Ru2(CO)4(,u-OAc)2]n as catalyst.36... 

More recently, a phosphine ligand-free ruthenium-catalyzed direct arylation with aryl bromides as electrophiles was disclosed. Notably, the use of inexpensive RuCl3(H20)n as catalyst in NMP as solvent allowed for economically attractive C-H bond functionalizations of pyridine, oxazoline and pyrazole derivatives, also with more sterically hindered orfftosubstituted aryl bromides as electrophiles (Scheme 21) [79, 80],... 

At the current level of development, Mn(III)-based oxidative free-radical cyclization is a very attractive procedure. Simple substrates are converted readily to highly functionalized and versatile products. The preferred solvent, acetic acid, is relatively safe since it becomes vinegar on dilution with water. Cu(OAc)2 is used in catalytic quantities. However, 2 equivalents of Mn(OAc)3 must be used. The amount of Mn(n) waste would be significantly decreased if Mn(OAc)3 could be used in catalytic quantities and regenerated by in situ reoxidation of the Mn(II) produced in the reaction. From the pollution point of view, electrochemical oxidation would be an effective way to regenerate Mn(ni). Oxidative free-radical cyclization using Mn(III) and Cu(n) as catalysts in an electrochemical oxidation would minimize the production of toxic chemicals and the resulting pollution. 

Subsequently, the authors extended this reaction to an enantioselective Mannich-cyclisation cascade using tridentate DBFox-Mg(n) as catalyst for the preparation of protected anh -a,p-diamino acids. After examining various BOX ligands in the process, they found that DBFox 39h could deliver the required adducts 71 in good to excellent yields (63-99%), diastereos-electivities (7 93-32 68) as well as enantioselectivities (84-99% ee). The scope of the reaction was rather broad and a variety of aryl-, heteroaiyl-, alkenyl-, and allqrl-derived imines could be tolerated (Scheme 3.22). 

Finally, it is worth mentioning that the carbonylation of 2-nitrostilbene (7d) to give 2-phenylindole (8d) with Ru3(CO)n as catalyst in acetonitrile proceeds at one atmosphere and 25 C under UV irradiation [14]. A blank experiment showed that the indole was not formed when irradiating 7d in the absence of RU3(CO)i2. 

In principle it is possible to distinguish between the two possibilities by a sufficient increase in rea nt concentration in practice a sufficiently high concentration is unattainable in the present system. A technically much more difficult method of distinguishing between the above two mechanisms involves isotopic fractionation experiments, a method used to make a similar mechanistic distinction for similar mercury(n)-catalysed aquations. A comparison of the relative effectiveness of thallium(m) and of mercury(n) as catalysts for aquation of the above complexes reveals that the activation enthalpies for the two catalysts are almost the same for a given complex - the difference lies in the activation entropies. Thallium(in) is a more effective catalyst for removing bromide from cobalt(ra), specifically from c/j-[Co(en)2(NH3)Br] +, than it is for removing chloride.ii It is interesting to contrast this result with the earlier demonstration that whereas in mercury(n)-catalysed aquation of the [Co(NH3)6C1] + and of the cis- and rrat/w-[Co(en)aCy+ cations there is evidence for a stable Co—Q— Hg intermediate, there is no evidence for a... 

Primary amides are readily dehydrated to the corresponding nitriles in the presence of silanes with nonacarbonyldiiron or Et3NH[HFe3(CO)n] as catalysts (Scheme 4-343). Functional groups like halogens, esters, and alkenes are tolerated. ... 

Silicon Nitride. SiUcon nitride is manufactured either as a powder as a precursor for the production of hot-pressed parts or as self-bonded, reaction-sintered, siUcon nitride parts. a-SiUcon nitride, used in the manufacture of Si N intended for hot pressing, can be obtained by nitriding Si powder in an atmosphere of H2, N2, and NH. Reaction conditions, eg, temperature, time, and atmosphere, have to be controlled closely. Special additions, such as Fe202 to the precursor material, act as catalysts for the formation of predorninately a-Si N. SiUcon nitride is ball-milled to a very fine powder and is purified by acid leaching. SiUcon nitride can be hot pressed to full density by adding 1—5% MgO. 

Iodine reacts with sulfuryl chloride ia the presence of aluminum chloride as catalyst-forming iodine chlorides. Sulfuryl chloride reacts with anhydrous ammonia yielding a series of sulfamides of the general formula NH2S02(NHS02) NH2, where n > 0. A cycHc compound of the formula... 

Although gravimetric methods have been used traditionally for the determination of large amounts of tellurium, more accurate and convenient volumetric methods are favored. The oxidation of teUurium(IV) by ceric sulfate in hot sulfuric acid solution in the presence of chromic ion as catalyst affords a convenient volumetric method for the determination of tellurium (32). Selenium(IV) does not interfere if the sulfuric acid is less than 2 N in concentration. Excess ceric sulfate is added, the excess being titrated with ferrous ammonium sulfate using o-phenanthroline ferrous—sulfate as indicator. The ceric sulfate method is best appHed in tellurium-rich materials such as refined tellurium or tellurium compounds. 

The earhest modification of the Oxo process (qv) employed cobalt hydrocarbonyl, HCo(CO)4, as catalyst. The reaction was carried out in the Hquid phase at 130—160°C and 10—20 MPa (1450—2900 psi) to give a ratio of n- to isobutyraldehyde of between 2 1 to 4 1. / -Butyraldehyde, the straight-chain isomer and the precursor of 2-ethylhexanol, was the more valuable product so that a high isomer ratio of n- to isobutyraldehyde was obviously advantageous. 

N O Y O R I Chiral homogeneous hydrogenation Homogeneous chiral hydrogenation ol unsaluraled alcohols, or cartMxyNc acids, enamides, ketones in the presence ol BINAP Ru or Rh complex 8 as catalyst. 

Propionic acid [79-09-4] M 74.1, b 141 , d 0.992, n 1.3865, n25 1.3843, pK 5-6.8 (Ho scale, aq H2SO4), pK2 4.88. Dried with Na2S04 or by fractional distn, then redistd after refluxing with a few crystals of KMn04. An alternative purification uses the conversion to the ethyl ester, fractional distn and hydrolysis. [Bradbury J Am Chem Soc 74 2709 1952.] Propionic acid can also be heated for 0.5h with an amount of benzoic anhydride equivalent to the amount of water present (in the presence of Cr03 as catalyst), followed by fractional distn. [Cham and Israel 7 C/iem 5oc 96 I960.]... 

Q. CO. C(COaEt). N(CO. Ph). CH. CHj. CHPr. CH, was hydrolysed and decarboxylated and the unstable keto-amine hydrogenated in methyl alcohol with palladised charcoal as catalyst to the... 

I) of which one form (picrate, m.p. 116°) is identical with dl-dihydro-de-N-methylheliotridane and the other (picrate, m.p. 126°) is diastereoisomeric with, and convertible into, it by, dehydrogenation to the corresponding pyrrole and hydrogenation of the latter in presence of copper chromite as catalyst. 

In presence of platinum oxide as catalyst in methyl alcohol, it hydrogenates to dihydrowogermine, which darkens >265° and melts at 277-8° (dec.) [a]n ° — 61° (pyridine). The dihydro-base still contains eight... 

The general rule has been formulated (P) that the less substituted enamine is formed from unsymmetrical ketones such as the 2-alkylcyclohexanones. In enamine 21 the R, group and the N-alkyl groups would interfere with one another if overlap is to be maintained between the nitrogen unshared electrons and the double bond. There would be less repulsion if the isomeric enamine (22) were formed. 2-Phenylcyclohexanone and pyrrolidine with p-toluenesulfonic acid as catalyst in refluxing benzene gave enamine... 

Chiral N,N-disubstituted 2-(aminomethyl)pyrrolidines as catalysts for asymmetric acylation of alcohols 99YGK598. 

In an extension of this work Scheeren et al. studied a series of derivatives of N-to-syl-oxazaborolidinones as catalysts for the 1,3-dipolar cycloaddition reaction of 1 with 2b [29]. The addition of a co-solvent appeared to be of major importance. Catalyst 3b was synthesized from the corresponding amino acid and BH3-THF, hence, THF was present as a co-solvent. In this reaction (-)-4b was obtained with 62% ee. If the catalyst instead was synthesized from the amino acid and... 

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