Pyridine-2-acetic ester

The Rf values given in column 5 were determined on Schleicher and Schull 2043 mgl paper, ascending in pyridine-acetic ester-acetic acid-water = 5 5 1 3. The relative values/tgiiico8aiiiiii6 or Ajv M6tyisiuco88iniii6 in columns 6 and 7 were ascertained on the same paper by descending chromatography using pyridine-acetic ester-acetic acid-water = 5 5 i 3- For vapour saturation pyridine-acetic ester-water = 11 40 6 was put in the bottom of the vessel used . 

Poly(W-pyiTOlidonylethylene), Poly((V-vinylpyrrolidone) (solubility depending on small amounts of W) acetone, dil. acids, aromatic alcohols, chloroacetic acid esters, chloroform, chlorohydrins, ethanol, glacial acetic acid, methanol, nitromethane, pyridine Acetic esters, acetone, acid 1 esters, carbon tetrachloride, 1 -chlorotoluene, diethyl ether, hydrocarbons, methoxybutyrate esters, nitomethaneAV 1-6,13,30... 

Figure 3 shows the production of acetaldehyde in the years 1969 through 1987 as well as an estimate of 1989—1995 production. The year 1969 was a peak year for acetaldehyde with a reported production of 748,000 t. Acetaldehyde production is linked with the demand for acetic acid, acetic anhydride, cellulose acetate, vinyl acetate resins, acetate esters, pentaerythritol, synthetic pyridine derivatives, terephthaHc acid, and peracetic acid. In 1976 acetic acid production represented 60% of the acetaldehyde demand. That demand has diminished as a result of the rising cost of ethylene as feedstock and methanol carbonylation as the preferred route to acetic acid (qv). 

The nameplate capacities for acetaldehyde production for the United States in 1989 are shown in Table 5 (120). Synthetic pyridine derivatives, peracetic acid, acetate esters by the Tischenko route, and pentaerythritol account for 40% of acetaldehyde demand. This sector may show strong growth in some products but all of these materials maybe prepared from alternative processes. 

The benzoylformate ester can be prepared from the 3 -hydroxy group in a deoxy-ribonucleotide by reaction with benzoyl chloroformate (anh. Pyr, 20°, 12 h, 86% yield) it is cleaved by aqueous pyridine (20°, 12 h, 31% yield), conditions that do not cleave an acetate ester. ... 

Thiophene-2-carbaldehyde condenses easily with ethyl acetoacetate or ethyl nitroacetate in the presence of TiCU and a tertiary organic base (pyridine or N- methylmorpholine) at 0-22 °C, giving (361) (72T663). Base-catalyzed condensation of thiophene-2-carbaldehyde with methyl (methylthio)methyl sulfoxide followed by treatment with HC1 in alcohols gives (2-thienyl)acetic esters (Scheme 114) (79BCJ2013). 

To begin the retrosynthetic analysis, note that the acetate ester is easily produced from the corresponding alcohol A. Therefore conversion of A to M using acetic anhydride/pyridine could be used in the synthetic step. (Remember For each retrosynthetic step, a reaction must be available to accomplish the synthetic step.)... 

Acetylation of the methyl ester with pyridine/acetic anhydride affords a triacetate. Reduction of the methyl ester with LiAIH4 in THF afforded 1,9-dihydroxynonanoate, m.p. 46°C. 

There are various ways wherein esters can be synthesised. An effective method is to react an acid chloride with an alcohol in the presence of pyridine yield. Acid anhydrides also react with alcohols to esters, but are less reactive. Moreover, the reaction is wasteful because half of the acyl content on the acid anhydride is wasted as the leaving group (i.e. the carboxylate ion). If the acid anhydride is cheap and readily available, this method can be used, e.g., acetic anhydride is useful for the synthesis of a range of acetate esters ... 

Esters are readily prepared by reaction of an alcohol with either an acyl chloride or an anhydride. Because it is more easily prepared from the acid, the acyl chloride is commonly employed. Again, a base, such as pyridine, is often added to react with the HC1 that is produced. Acetic anhydride, which is commercially available, is often used for the preparation of acetate esters. Following are several examples. 

Formation of acetate esters. Acetic anhydride and pyridine convert all the hydroxyl groups of a sugar to acetate esters. The stereochemistry at the anomeric carbon is usually preserved. 

The OH groups of monosaccharides can also be converted to esters. For example, treatment of P-D-glucose with either acetic anhydride or acetyl chloride in the presence of pyridine (a base) converts all OH groups into acetate esters. 

S3mthesis of Collidine.—The most important synthesis of pyridine homologues is that of collidine from which pyridine may be obtained by elimination of the methyl groups by oxidation and loss of carbon dioxide. When aldehyde ammonia is heated with aceto-acetic ester a derivative of a di-hydrogenated collidine is obtained, as follows ... 

The last step of this problem is the final cleavage of the two remaining secondary TBS-ethers. This is accomplished by HF-pyridine in THF and addition of hexafluorosilic acid. This significantly facilitates the cleavage of both TBS-ethers in terms of reaction time and yield. Furthermore, the reaction becomes less sensitive to the quality of the HF-pyridine batches. The conditions used are mild enough to allow the presence of acetals, esters and epoxides. Therefore the macrolactone is stable under these conditions, because the pH of hexafluorosilic acid is nearly the same as a solution of HF. Product 19 is itself an epothilone D analogue. 

Cellulose acetate phthalate is produced by reacting the partial acetate ester of cellulose with phthalic anhydride in the presence of a tertiary organic base such as pyridine, or a strong acid such as sulfuric acid. 

Protective group for nucleosides. Stepwise synthesis of oligonucleotides utilizing 2-cyanoethyl phosphate (1, 172-173) requires protection of the 3 -hydroxyl group which can be cleaved under essentially neutral conditions, since a methoxy-trityl ether is sensitive to acid and a /3-cyanoethyl phosphoric ester is sensitive to alkali. The /3-benzoylpropionyl group meets these requirements, since it is quantitatively cleaved by dilute solutions of hydrazine hydrate in pyridine-acetic acid. The esters are prepared by condensation with DCC (dicyclohexylcarbodiimide). Definitive paper R. L. Letsinger and P. S. Miller, Am. Soc., 91, 3356 (1969)... 

---