Pyridine, catalysis

The scope of this reaction is similar to that of 10-21. Though anhydrides are somewhat less reactive than acyl halides, they are often used to prepare carboxylic esters. Acids, Lewis acids, and bases are often used as catalysts—most often, pyridine. Catalysis by pyridine is of the nucleophilic type (see 10-9). 4-(A,A-Dimethylamino)pyridine is a better catalyst than pyridine and can be used in cases where pyridine fails. " Nonbasic catalysts are cobalt(II) chloride " and TaCls—Si02. " Formic anhydride is not a stable compound but esters of formic acid can be prepared by treating alcohols " or phenols " with acetic-formic anhydride. Cyclic anhydrides give monoesterified dicarboxylic acids, for example,... 

Acyl chlorides are highly reactive acylating agents and react very rapidly with alcohols and other nucleophiles. Preparative procedures often call for use of pyridine as a catalyst. Pyridine catalysis involves initial formation of an acyl pyridinium ion, which then reacts with the alcohol. Pyridine is a better nucleophile than the neutral alcohol, but the acyl pyridinium ion reacts more rapidly with the alcohol than the acyl chloride.103... 

The penta-acetoxy compound 7a could be prepared fi om this by using an excess of acetic anhydride in pyridine with 4-(dimethylamino)pyridine catalysis. 

Wamser, C. C., and J. A. Yates, Kinetics and Mechanisms for the Two-Phase Reaction Between Aqueous Aniline and Benzoyl Chloride in Chloroform, with and without Pyridine Catalysis, J. Org. Chem., 54, 150 (1989). 

However, because the addition of an alcohol to a ketene acetal is an acid-catalyzed reaction, formation of polymers by the addition of diols to this diketene acetal is greatly complicated by the extreme susceptibility of this monomer towards a competing cationic polymerization. Nevertheless, linear polymers could be prepared by using iodine in pyridine catalysis [24], This polymerization, illustrated for 1,6-hexanediol, is shown in Scheme 9. The polymer was characterized by 13C-NMR spectroscopy shown in Fig. 5 [24], The band assignments are shown in the figure. 

Bianchini C, Gatteschi D, Giambastiani G et al (2007) Electronic influence of the thienyl sulfur atom on the oligomerization of ethylene by cobalt(II) 6-(thienyl)-2-(imino)pyridine catalysis. Organometallics 26 726-739... 

Wamser. C.C. Yates. J.A. Kinetics and mechanisms for the two-phase reaction between aqueous aniline and benzoyl chloride in chlorofomi, with and without pyridine catalysis. J. Org. Chem. 1989, 54. 150-154. 

Scheme 24.2 Route for the conversion of (+)-(R)-balfourodine into (+)-(R)-isobalfourodine and (+)-(R)-isoplatydesmine into (—)-(S)-ribalinine with acetic anhydride in pyridine and ulterior hydrolyze. Mechanism as proposed by Fersht and coworker [141], in which pyridine catalysis involves initial formation of an acyl pyridinium ion, which then reacts with the alcohol...

Bettucci L, Bianchini C, Filippi J, Lavacchi A, Oberhauser W. Chemoselective aerobic diol oxidation by paUadium(II)-pyridine catalysis. Eur J Inorg Chem. 2011 1797-1805. 

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