A breakthrough in Pyridine-N-OxkJes by Reilly. - C&EN Global

Nov 7, 2010 - Advertisements that appeared within the print issues of Chem. Eng. News have been included in the C&EN Archives to provide a ...
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A breakthrough in Pyridine-N-OxkJes bv Reillv. New process technology. New lower price. Commercial availability. The N-oxide group activates the pyridine ring toward both electrophilic and nucleophilic aromatic substitution.

— the transformation of aliphatic halides to give aldehydes, +

RCH2CI -

0 II R-C-H

N02

n

Ο

HN03, Δ Ο

ci-

"Ί^ϊΤΟΙ

— the oxidation of a-halocarboxylic acids to give aldehydes and carbon dioxide,

90% yield 90% yield Alkyl groups in the 2- and 4-positions are activated toward condensation with aromatic al­ dehydes and undergo a variety of reactions not possible in the parent pyridine system.

R-C-COOH-

+ R-C-H + C02

cr

H

— the oxidative decarboxylation of carboxylic acids or their anhydrides, ο

R = H, CH 3 , 3-COOH, 4-COOH. More to come.

Ac2o +

yield

Pyridine-N-oxides are versatile chemical intermediates which also function as chemical reagents or catalysts. The N-oxides are gener­ ally prepared by oxidation of pyridine or its derivatives with a peracid. Because of the difficulty in separating acids from the weakly basic N-oxides, they have tra­ ditionally been expensive and dif­ ficult to obtain in high purity. The new process technology developed at Reilly has improved N-oxide pur­ ity, increased production capacity, and lowered the prices of most of our N-oxides by nearly 50%. The reactions outlined below illustrate the increased reactivity imparted to the pyridine ring by the N-oxide group and describe the utility of pyridine-N-oxide as a chemical reagent or catalyst.

CH3

RR' CH-COOH



r ^ ^ i ( )

" + R-C-R ' + C02

— the conversion of isocyanides to isocyanates.

CH20Ac % yield

+

03^-QU "

yield

When manipulation of the pyridine ring has been completed, the N-oxide group (if still present) can be removed under mild conditions with a variety of reagents. Pyridine-N-oxide functions as a chemical reagent when used in stoichiometric amounts as illus­ trated in the following examples:

Reilly Tar & Chemical Corporation

R-NEC-

Pyridine-N-oxide catalyzes the acylation of anilines when used in less than stoichiometric amounts.

COCI

NH2

*-©

6*6—-6

If you have forgotten how versatile pyridine-N-oxides are, write for our new brochure. Samples available on request.

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