- Effects of alkali and alkaline earth metals on the Kolbe-Schmitt reaction
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It was found that the carboxylations of magnesium, calcium, and barium phenoxides with carbon dioxide at 260 °C produced salicylic acid and dicarboxylic acids (4-hydroxyisophthalic acid and 2-hydroxyisophthalic acid) in very high yields (80-100%), exceeding that of the ordinary Kolbe-Schmitt reaction. The orientation (ortho/para ratio) was controlled not only by chelations of the intermediate with alkaline earth metal (Mg, Ca, Ba) ions, resulting in salicylic acid, but also by the sizes of metal ions (Rb, Cs), giving p-hydroxybenzoic acid in a much higher ratio than the widely used method with potassium or sodium phenoxide. These alkaline earth metals worked to produce 3-hydroxy-2-naphthoic acid by the reaction of 2-naphthoxide with carbon dioxide, but the yield of 6-hydroxy-2-naphthoic acid was comparable to that of 3-hydroxy-2-naphthoic acid when cesium or rubidium 2 naphthoxide was employed. Considerably high yields (~60%) of 6-hydroxy-2-naphthoic acid, a monomer of one of the best liquid-crystal polymers, was attained by the carboxylation of cesium or rubidium 2-naphthoxide in the presence of potassium or sodium carbonate, where the alkali metal ion was supposed to increase the reactivity of the substrate. The formation of "binol" was observed in the preparation of 2-naphthoxides with metal hydroxides, especially with copper(II) ion.
- Rahim, Mohammad Abdur,Matsui, Yoshihisa,Kosugi, Yoshio
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p. 619 - 622
(2007/10/03)
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- Organomagnesium Inner Complexes, Part I. Bis(dialkylaminoalkyl)- and Bis(alkoxybutyl)magnesium Compounds
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A series of magnesium inner complexes has been prepared by reacting MgH2 (prepared by homogeneous catalysis) with dialkylallyl- and -3-butenylamines and -3-butenylethers in the presence of catalytic amounts of ZrCl4.The monomeric nature of bis(4-methoxybutyl)magnesium has been confirmed by X-ray diffraction.The analogous syntheses of bis(3-alkoxypropyl)magnesium compounds failed: cleavage of the allyl ether with elimination of propene occurred.This cleavage reaction is accelerated by catalytic amounts of NiCl2 or ZrCl4. - Keywords: Magnesium, Inner Complexes, Crystal Structure, X-Ray
- Angermund, Klaus,Bogdanovic, Borislav,Koppetsch, Gudrun,Krueger, Carl,Mynott, Richard,et al.
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p. 455 - 466
(2007/10/02)
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- Process for producing o-methylated phenols
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A process for producing o-methylated phenols useful as raw materials for resins and medicines in high yields comprising reacting methanol with phenols in the presence of a catalyst containing at least one compound selected from the group consisting of (1) magnesium oxide, manganese oxide and iron oxide which are all pre-treated with phenols and (2) magnesium phenolate.
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