Manganese Lewis acids

Also, manganese added to cobalt on activated carbon catalysts resulted in a decrease in bulk carbide formation during reduction and a decrease in the subsequent deactivation rate.84 Magnesium and yttrium added to the support in alumina-supported cobalt catalysts showed a lower extent of carburization. This was explained by a decrease in Lewis acidity of the alumina surface in the presence of these ions.87... 

S / V CONTENTS Preface, Robert W. Hay. Structure and Function of Manganese-Containing Biomolecules, David C. Weather-bum. Repertories of Metal Ions as Lewis Acid Catalysts in Organic Reactions, Junghan Suh. The Multicopper-Enzyme Ascorbate Oxidase, Albrecht Messerschmidt. The Bioinorganic Chemistry of Aluminum, Tomas Kiss and Etelka Farkas. The Role of Nitric Oxide in Animal Physiology, Anthony R. Butler, Frederick Flitney and Peter Rhodes. Index. 

An application of industrial importance of Lewis acidic metal salts is the condensation of carboxylic diacids and diols to give polyesters. This is an acid catalysed reaction that in the laboratory is usually catalysed by protic acids. For this industrial application salts of manganese, nickel, or cobalt and the like are used. From a chemical point of view this chemistry may not be very exciting or complicated, the large scale on which it is being carried out makes it to an important industrial reaction [29],... 

Although the Sharpless catalyst was extremely useful and efficient for allylic alcohols, the results with ordinary alkenes were very poor. Therefore the search for catalysts that would be enantioselective for non-alcoholic substrates continued. In 1990, the groups of Jacobsen and Katsuki reported on the enantioselective epoxidation of simple alkenes both using catalysts based on chiral manganese salen complexes [8,9], Since then the use of chiral salen complexes has been explored in a large number of reactions, which all utilise the Lewis acid character or the capacity of oxene, nitrene, or carbene transfer of the salen complexes (for a review see [10]). 

A chiral alumi n i u m - s a I e n - PI13 PO combination catalyses addition to ketones in up to 92% ee the catalyst system essentially acts as a Lewis acid-Lewis base bifunctional system.248 A similar chiral manganese(III)-salen-Ph3PO method is comparable.249... 

Nanostructured aluminum [74—78], iron [74] and aluminum-manganese alloys [74] have been prepared from a Lewis acid A1Q3/[BMIM]Q mixture (65 mol% AICI3, 35 mol% [BMIMJC1) whereas palladium alloys have been deposited from a Lewis basic system (45 mol% Aid , 55 mol% [BMIMJC1). The electrochemical cell and all parts which are in contact with the electrolyte have to be built from inert materials. As cathode material glassy carbon can be used. A constant ion concentration in the electrolyte can be realized by the use of a sacrificial anode consisting of the... 

Prototypical radical additions were examined under manganese-mediated photolysis conditions with InCp as the Lewis acid, coupling isopropyl iodide with a variety of y-hydrazonoesters 35a-35d (Table 6) bearing varied substitution at the position a to the ester. The a-methyl, a,a-dimethyl, and a-benzyloxy substituents appeared to have little effect on reaction efficiency and selectivity, as all provided the isopropyl adducts with consistently high diastereoselectivities and excellent yields (91-98%). Surprisingly, the selectivity was only slightly... 

Salts of other transition metals including vanadium, cerium, chromium and manganese have been used for a-oxygenation, although rarely applied in synthesis. Manganese triacetate has been used for the efficient a -oxidation of enones (Section 2.3.2.2.1.i), but appears not to have been used for the a-hydrox-ylation of saturated ketones des]Hte its known ability to form the corresponding a-keto radicals. Similarly the use of Lewis acid assisted enolization in the oxidative process appears to have been limited to the LTA-mediated examples. 

Anions formed from group 6 and manganese Fischer carbene complexes undergo aldol condensations with aldehydes and ketones. Allylic carbenes exclusively react in the y position with aldehydes affording dienyl-substituted carbenes. For alkoxy-substituted carbenes, the presence of an excess Lewis acid see Lewis Acids Bases), such as boron trifluoride etherate, titanium tetrachloride, or tin tetrachloride is required for the reaction to proceed in reasonable yield. The initial aldol product can be isolated without elimination (Scheme 12). ... 

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