Acyl chlorides reaction with pyridine

Esterification with acyl chlorides (Section 15 8) Acyl chlorides react with alcohols to give esters The reaction is usually carried out in the presence of pyridine... 

Acyl chlorides react with carboxylic acids to yield acid anhydrides When this reaction is used for preparative purposes a weak organic base such as pyridine is normally added Pyridine is a catalyst for the reaction and also acts as a base to neutralize the hydrogen chloride that is formed... 

This is the best procedure for the preparation of simple and mixed anhydrides. Benzoic anhydride is prepared simply by heating an equimolar mixture of benzoic acid and benzoyl chloride. The reaction is general when carried out in the presence of pyridine. The acyl halides react with pyridine to give pyridinium salts, which are powerful acylating agents. 

The addition of nucleophiles to 1-acylpyridinium salts has surfaced as a powerful method for the synthesis of substituted pyridines. The 1-acylpyridinium salts are formed in situ by adding an acyl chloride to a pyridine in an aprotic solvent such as tetrahydrofuran. The formation of the 1-acylpyridinium salt is very rapid and will occur in the presence of various organometallics without significant competition from the reaction of the nucleophile and the acyl chloride. The addition of ethyl chloroformate to a mixture of pyridine and ethylmagnesium bromide gives 1,2- and 1-4-dihydropyridines 29 and 30 in a ratio of 64/36. Although these dihydropyridine intermediates can be aromatized with hot sulfur to 2- and 4-alkylpyridines, the poor regioselectivity makes this procedure unattractive. 

Trifluoromethylated pyrones can also be prepared from acyl chlorides by reaction with pyridine and trifluoroacetic anhydride followed by capture of the intermediate trifluoroacyl ketene 8 with suitable reagents. Thus, addition of A -cyclohexenyl-morpholine to the intermediate from palmitoyl chloride gave pyrone 9 as the major product, accompanied by amide 10. Ethyl vinyl ether yielded pyrones 11a and 11b (through p-elimination of ethanol) [9] (Scheme 5). 

Now let s draw the forward scheme. Benzene is converted into bromobenzene upon treatment with Br2 and AlBrs (via an electrophilic aromatic substitution reaction). Bromobenzene is then converted to phenyl magnesium bromide (a Grignard reagent), which is then treated with formalddryde, followed by water work-up, to give benzyl alcohol. This alcohol then serves as a nucleophile in a subsequent acyl substitution reaction with acetyl chloride and pyridine to produce benzyl acetate (a process called acetylation). 

From acyl chlorides (Sections 15.8 and 20.4) Alcohols react with acyl chlorides by nucleophilic acyl substitution to yield esters. These reactions are typically performed in the presence of a weak base such as pyridine. 

Oil-soluble derivatives of testosterone itself predate those of its 19-nor congener these agents too are used to administer depot injections so as to provide in effect long-term blood levels of drug. Thus, acylation of testosterone with propionyl chloride in the presence of pyridine yields testosterone propionate (76a)acylation by means of decanoic anhydride yields testosterone decanoate (76b).Finally, reaction of 75 with 3-cyclopentylpropionyl chloride affords testosterone cypionate (76c)This last undergoes hydrolysis unusually slowly because of the presence of two substituents at the 5 position (see Newman s Rule of 6). ... 

The solvent system N2O4/DMF has been employed for the preparation of inorganic esters, e.g., phosphates and sulfates [221] as well as organic esters. The latter products were obtained by reacting the polymer with acyl chlorides, or acid anhydrides in the presence of a pyridine base. The nitrite ester formed has been successfully trans-esterified by the reaction with RCOCl... 

Imides can be prepared by the attack of amides or their salts on acyl halides, anhydrides, and carboxylic acids or esters. The best synthetic method for the preparation of acyclic imides is the reaction between an amide and an anhydride at 100°C catalyzed by H2S04. When acyl chlorides are treated with amides in a2 l molar ratio at low temperatures in the presence of pyridine, the products are N,N-diacylamides, (RCO)3N. ... 

These reactions are most important for the preparation of acyl fluorides. " Acyl chlorides and anhydrides can be converted to acyl fluorides by treatment with polyhydrogen fluoride-pyridine solution" or with liquid HF at — 10°C. Formyl fluoride, which is a stable compound, was prepared by the latter procedure from the mixed anhydride of formic and acetic acids. Acyl fluorides can also be obtained by reaction of acyl chlorides with KF in acetic acid or with DAST. Carboxylic esters and anhydrides can be converted to acyl halides other than fluorides by the inorganic acid halides mentioned in 10-77, as well as with PhsPXa (X = Cl or but this is seldom done. Halide exchange can be carried out in a... 

Lack of selectivity in the reaction of the /3-D-glucoside derivative with one molar equivalent of benzylthiocarbonyl chloride has also been noted 40% of the 2,3-diester and 40% of the starting material were isolated.40 Similarly, unimolar benzoylation of phenyl 4,6-0-benzylidene-/3-D-glucopyranoside gave only 9% of the 3-ester, together with 47% of the 2,3-diester.41 Acylation of benzyl 4,6-0-benzylidene-/8-D-glucopyranoside with acetic anhydride-pyridine-pyridine hydrochloride yielded,42 in contrast to the reaction with the... 

Finally, mesoionic oxazolo[3,2- ]pyridines such as 318, obtained by reaction of 317 with acyl chlorides, are readily hydrolyzed to pyridones 319 by treatment with diluted hydrochloric acid (Scheme 86) <2005MOL1109>. 

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