A breakthrough PyrkJine-N-Oxides

by Reilly.

?&ΐ

R = H, CH3, 3-COOH,4-COOH. More to come. Pyridine-N-oxides are versatile chemical intermediates which also function as chemical reagents or catalysts. The N-oxides are gener­ally 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 tra­ditionally been expensive and dif­ficult to obtain in high purity. The new process technology developed at Reilly has improved N-oxide pur­ity, 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.

The N-oxide group activates the pyridine ring toward both elec-trophilic and nucleophilic aromatic substitution.

N02

C=CH

90% yield 90% yield Alkyl groups in the 2- and 4-positions are activated toward condensation \ ι aromatic al­dehydes and uHtifergo a variety of reactions not possible in the parent pyridine system.

CH3 CHO

NMe2

HC CH

NMe2

CH3 CH20Ac

6 0 % yield

1

p-TsCI ^ [ ^ ^ 1 9 0 % yield

SCH3 ^ î T ^ C H 2 C I

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 illus­trated in the following examples:

— the transformation of aliphatic halides to give aldehydes,

RCH2CI - + R-C-H

+ I

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

R - C - C 0 0 H -

o II

+ R-C-H + C02

+ T H Cr

— the oxidative decarboxylation of carboxylic acids or their anhydrides,

ο II

+ R-C-R'+C02 + RR' CH-C00H

Ac20

— the conversion of isocyanides to isocyanates.

+ R-N=C- + R-N=C=0

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

C0CI NH2 f-Q α-a—-à If you have forgotten how versatile pyridine-N-oxides are, write for our new brochure. Samples available on request.

in

New process technology. New lower price. Commercial availability.

78% yield KOH * pyridine

Reilly Tar & Chemical Corporation

1510.Market Square Center 151 North Delaware Street Indianapolis, Indiana 46204 (317) 247-8141 Telex: 27-404

R

Ν Ο