Oxidative decarboxylation, potassium

A cursory inspection of key intermediate 8 (see Scheme 1) reveals that it possesses both vicinal and remote stereochemical relationships. To cope with the stereochemical challenge posed by this intermediate and to enhance overall efficiency, a convergent approach featuring the union of optically active intermediates 18 and 19 was adopted. Scheme 5a illustrates the synthesis of intermediate 18. Thus, oxidative cleavage of the trisubstituted olefin of (/ )-citronellic acid benzyl ester (28) with ozone, followed by oxidative workup with Jones reagent, affords a carboxylic acid which can be oxidatively decarboxylated to 29 with lead tetraacetate and copper(n) acetate. Saponification of the benzyl ester in 29 with potassium hydroxide provides an unsaturated carboxylic acid which undergoes smooth conversion to trans iodolactone 30 on treatment with iodine in acetonitrile at -15 °C (89% yield from 29).24 The diastereoselectivity of the thermodynamically controlled iodolacto-nization reaction is approximately 20 1 in favor of the more stable trans iodolactone 30. 

Potassium ferricyanide in oxidative decarboxylation, 40, 86 Potassium permanganate for oxidation of (trialkylmethyl)amines to tri-alkylnitromethanes, 43,87 Pregnenolone acetate, conversion to 3/3-acetoxyetienic acid, 42, 5 Propane, 2,2-dibotoxy-, 42,1 Propargylsuccinic anhydride, by-product in addition of maleic anhydride to allcne, 43, 27... 

Ruthenium(III) catalyses the oxidative decarboxylation of butanoic and 2-methylpropanoic acid in aqueous sulfuric acid. ° Studies of alkaline earth (Ba, Sr) metal alkoxides in amide ethanolysis and of alkali metal alkoxide clusters as highly effective transesterification catalysts were covered earlier. Kinetic studies of the ethanolysis of 5-nitroquinol-8-yl benzoate (228) in the presence of lithium, sodium, or potassium ethoxide revealed that the highest catalytic activity is observed with Na+.iio... 

Lower temperatures than those mentioned above inhibit the exothermic reaction and the reaction time is extended to approximately 24 hr. Less efficient cooling results in warming to 70-80°C, which causes decarboxylation of the Intermediate carboxylate and/or simple oxidation by potassium hypochlorite. 

Methylquinazoline is oxidized with potassium permanganate in aqueous potassium hydroxide solution to give pyrimidine-2,5-dicarboxylic acid in 39 % yield. The intermediate is probably pyrimidine-2,4,5-tricarboxylic acid which spontaneously decarboxylates to pyrimidine-2,5-dicarboxylic acid. ... 

OXIDATIVE DECARBOXYLATION Lead tetraacetate. Potassium persulfate. 

The reaction of 3-aroylpyrido[2,3-6]pyrazines 1 with sodium hydroxide in dimethyl sulfoxide is found to result in aryl migration, which is interpreted as a kind of benzilic acid rearrangement, followed by a decarboxylation step, and finally oxidation by potassium hexacyanoferrate(III).84... 

R = H, = Me) and (96 R = Me, R = H) is obtained by oxidative decarboxylation of the bicyclo[4.1.0]hept-3-ene-l,6-dicarboxylic acid (95) with lead tetra-acetate. The amino-acid (97), prepared from C- (o-hydroxyphenyl)glycine and t-butyl azidoformate, cyclizes to the aminobenzofuranone (98) this type of product exhibits chemiluminescence when exposed to oxygen in the presence of a base. Treatment of 2,2 -di(bromomethyl)benzil (99) with potassium t-butoxide results in an unusual intramolecular nucleophilic substitution to give the spiro-compound (100). 

At the same time an important paper (67) appeared in which essentially the same conclusions with regard to the structure of bebeerine were arrived at by a different route. Faltis, Kadiera, and Doblhammer (67) treated the inactive a, a -dimethylbebeerine methine, obtained by a one-stage Hofmann degradation of bebeerine dimethyl ether, with ozone and obtained a mixture of two dimethylamino dialdehydes. These were not isolated but were converted to the chloromethylate derivatives, oxidized with potassium permanganate to the acids, and boiled with dilute alkah to decompose the quaternary bases. Besides trimethylamine, a mixture of two vinyl carboxylic acids were obtained. One of these proved to be 4, 6-dicarboxy-2,3-dimethoxy-5-vinyldiphenyl ether (LIX). The other vinyl carboxylic acid, which was readily separated from LIX by virtue of its low solubility, was first decarboxylated by heating with quinoline and naturkupfer C and then oxidized with potassium permanganate in acetone. This yielded 4-carboxy-2,2 -dimethoxydiphenyl ether (LXIII), the structure of which was proved by direct comparison with the synthetic compound prepared by the Ullmann condensation of o-bromoanisole and vanillic acid. 

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