Collidine, Synthesis

Oltra and Cuerva have reported a unified strategy for the synthesis of the eudesmanolides that relies on the collidine-chlorotrimethylsilane reagent... 

It was found that the reaction conditions which were optimized for the synthesis of poly(arylene siloxanylenes) (43) could be employed for the synthesis of siloxane-modified poly-(arylene carbonates). 2,4,6-Trimethylpyridine (collidine) was selected as the most suitable of all catalysts investigated (43) for the synthesis of the siloxane modified poly(arylene carbonates). Properties of polymers prepared by this method are given in Table I. In comparision to the phosgene-catalyzed homo-polycondensation of bis-silanols, III, the inherent viscosities... 

All of the sulfone diols were able to form oligomers in the second step of the reaction sequence, the Ullmann ether synthesis. As with the synthesis of the mono(bromophenoxy)phenol products, two methods were used to form the dibromo materials. Method A used pyridine, potassium carbonate and cuprous iodide, while Method B employed collidine and cuprous oxide with the dibromobenzene and higher molecular weight diol (IV). The major difference between the syntheses of the mono(bromophenoxy)phenols described earlier and these lies in the stoichiometry of the reactions. In order to... 

Precursors in the biosynthesis of niacin In animals and bacteria, tryptophan and in plants, glycerol and succinic acid. Intermediates in the synthesis include kynurenine, hydroxyanthranilic acid, and quinolinic acid. In animals, the niacin storage sites are liver, heart, and muscle. Niacin supplements are prepared commercially by (1) Hydrolysis of 3-cyanopyndine or (2) oxidation of nicotine, quinoltne, or collidine. 

More advanced students should work through a synthesis involving several steps, e.g., Collidine, and should also attempt the preparation of homologues of some of the substances given in detail. In the lists given above, several preparations of industrial importance are included. 

The synthesis of O-vinylacetoxime by direct vinylation of acetoxime with calcium carbide in an aqueous medium, reported by Pivnenko (70ZOR2146), failed to be reproduced (75ZOR1141). Under these conditions, a symmetrical collidine was obtained instead of O-vinylacetoxime (75ZOR1141,75KGS1427). 

Cleavage of alkyl ary ethers (4, 305). The most difficult step in a recent synthesis of aklavinone (3) is demethylation of 1 to 2. Lewis acid reagents (BBr3) were useless because of preferential attack of the allylic hydroxyl nucleophilic demethylation (LiSCH3) results in concomitant aromatization of ring A. Demethylation "with Lil buffered with benzoic acid in pyridine-collidine at 145° was successful and proceeded in 92% yield.4, Aklavinone is the aglycone of an antitumor anthracycline that is less toxic than adriamycin. 

The conditions using 2,4,6-collidine/Tf20 and having the reaction warm from -78 °C to 25 °C were chosen mainly to avoid using more expensive reagents such as 2,6-di-r-butyl-4-methylpyridine or A-phenyl triflimide. (a) Stang, P. J. Hanack, M. C. Subramanian, L. R. Synthesis 1982, 85. (b) McMurray, J. E. Scott, W. J. Tetrahedron Lett. 1983,24,979. 

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