Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-09-15
2002-04-30
O'Sullivan, Peter (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C546S192000, C548S561000, C548S952000, C549S075000, C549S408000, C549S495000, C558S452000, C562S553000, C562S576000, C564S089000, C564S092000, C564S463000
Reexamination Certificate
active
06380429
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a process for the oxidation of sulfonamides to sulfonyl imines using chromium (IV) dioxide as oxidant.
TECHNICAL BACKGROUND OF THE INVENTION
There are no known routes to sulfonyl imines of the structure R
1
R
2
C═NSO
2
R
3
via oxidation of the corresponding sulfonamides.
S. M. Weinreb,
Topics in Current Chemistry
, Volume 190, 131-184 broadly reviews the preparation and chemical reactions of N-sulfonyl imines.
F. A. Davis et al.,
J. Org. Chem
., 1997,62, 2555-2563 disclose processes for the preparation of enantiomerically pure sulfinimines.
A Viso et al.,
J. Org. Chem
., 1997, 62, 2316-2317 discuss the cycloaddition reactions of sulfinimines.
T. Fukuyama et al.,
Tetrahedron Letters
, Vol. 36, No. 36, pp. 6373-6374 report the preparation of 2- and 4-nitrobenzenesulfonamides and their use as amine protective groups with easy chemical removal by thiolates.
R. A. Lee and D. S. Donald,
Tetrahedron Letters
, vol. 38, No. 22, pp. 3857-3860, 1997 disclose the utility of Magtrieve® chromium dioxide as an oxidant for the conversion of alcohols to aldehydes and ketones.
U.S. Pat. No. 5,698,744 discloses the utility of chromium dioxide for a variety of oxidation processes. Oxidation of alcohols and activated hydrocarbons are exemplified.
There is a need for a process for the oxidation of sulfonamides to corresponding sulfonyl imines.
SUMMARY OF THE INVENTION
This invention discloses the use of chromium dioxide as a suitable oxidizing agent for the preparation of sulfonyl imines. The use of chromium (IV) dioxide provides the advantage of using magnetism to separate residual chromium from the desired product.
Also disclosed is a process for the oxidation of sulfonamide of the structure I
where R
1
and R
2
are independently selected from the group consisting of hydrogen and organic radicals not possessing a hydrogen atom in the position beta to the nitrogen of the sulfonamide group; and R
3
is an organic radical selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl groups, and optionally, R
1
and R
2
can form a ring, to sulfonyl imines of the structure II,
wherein R
1
, R
2
, and R
3
are as described above, said process comprising:
(a) optionally, contacting a sulfonamide of the structure I with a suitable solvent or liquid;
(b) contacting the sulfonamide of the structure I with chromium (IV) dioxide under oxidizing conditions whereby a sulfonyl imine product is produced; and
(c) optionally, isolating the sulfonyl imine product.
Another disclosure of the present invention is a process for the preparation and in-situ use of imines of the structure III,
R
1
R
2
C═NH III
from corresponding sulfonyl imines of the structure II
having iminyl functionality and wherein R
1
and R
2
are independently selected from the group consisting of hydrogen and organic radicals not possessing a hydrogen atom in the position beta to the nitrogen of the sulfonamide group, and wherein R
3
is an organic radical selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl groups, and optionally, R
1
and R
2
can form a ring, comprising:
(a) contacting the sulfonyl imine of the structure II with a reagent that is capable of reacting with the iminyl functionality of the structure II to form a derivative of structure III having a sulfonyl group; and
(b) removing the sulfonyl group.
A further disclosure of the present invention is a process for the preparation and in-situ use of a combinatorial library of imines of the structure III,
R
1
R
2
C═NH III
from corresponding sulfonyl imines of the structure II
having iminyl functionality and wherein R
1
and R
2
are independently selected from the group consisting of hydrogen and organic radicals not possessing a hydrogen atom in the position beta to the nitrogen of the sulfonamide group, and wherein R
3
is an organic radical selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl groups, and optionally, R
1
and R
2
can form a ring, comprising:
(a) contacting the sulfonyl imines of the structure II with one or more reagents that are capable of reacting with the iminyl functionality of the structure II to form at least one derivative of structure III having a sulfonyl group; and
(b) removing the sulfonyl group.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a process for the oxidation of sulfonamides to produce sulfonyl imines. The invention lies in the use of chromium (IV) dioxide (CrO
2
) to afford yields which are generally greater than 50% and purities greater than 70% under reaction conditions that are relatively easy to carry out.
One source of chromium (IV) dioxide is E. I. du Pont de Nemours and Company, Wilmington, Del., which sells the material under the trade name Magtrieve®. Magtrieve® is a recyclable magnetic chromium (IV) dioxide.
In the process of the present invention,
the sulfonamides of the structure I and resulting sulfonyl imine products of the structure II may bear a wide variety of organic substituents. R
1
and R
2
are selected from the group consisting of hydrogen and organic radicals not possessing a hydrogen atom in the position beta to (i.e., 2 carbon atoms away from) the nitrogen of the sulfonamide group. R
1
and R
2
may be hydrogen, alkyl, alkenyl, substituted alkyl or alkenyl, alkynyl, and aryl, including phenyl, substituted aryl and heteroaryl, and optionally, R
1
and R
2
can together form a ring. Preferably, R
1
and R
2
are selected from the group consisting of hydrogen, optionally, substituted aryl and optionally, substituted heterocyclic groups. Specifically exemplified R
1
and R
2
substituents are hydrogen, phenyl, p-fluorophenyl, p-methoxyphenyl, 2-furanyl, and 2-thiophenyl.
R
3
is an organic radical selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl groups. Specifically exemplified R
3
substituents include 2-nitrophenyl, 2,4-dinitrophenyl, p-tolyl, p-methoxyphenyl, methyl, and trifluoromethyl.
The sulfonamide of the structure I may be prepared by contacting an amine of the structure R
1
R
2
CHNH
2
wherein R
1
and R
2
are independently selected from the group consisting of hydrogen and organic radicals not possessing a hydrogen atom in the position beta to the nitrogen, with a sulfonyl chloride of the structure R
3
SO
2
Cl. Other methods known in the art may be used also.
Sulfonyl imines may be prepared by the process disclosed at temperatures from about 20° C. to about 200° C., preferably from about 50° C. to about 200° C., and most preferably from about 100° C. to about 130° C.
The process is most conveniently carried out at atmospheric pressure. Super- or sub-atmospheric pressure may be used if desired.
The process can be carried out with the sulfonamide at least partially dissolved in a suitable solvent or liquid. A wide variety of solvents or liquids may be used. Suitable solvents and liquids are aprotic, non-nucleophilic liquids that are unreactive to the chromium dioxide oxidation reagent under reaction conditions. Preferred solvents and liquids are aromatic hydrocarbons (for example, benzene or toluene), substituted benzenes (for example, chlorobenzene or dichlorobenzene), halogenated aliphatic hydrocarbons (for example, carbon tetrachloride and dichloroethane), acetonitrile, nitromethane, esters, and ethers.
The reaction mixture is heterogeneous. Agitation by means customary in the art is acceptable.
Upon conclusion of the reaction, particulate chromium dioxide is conveniently removed from the liquid organic substrate/solvent phase by filtration, centrifugation or magnetic separation.
The process of this invention is useful in the synthesis of organic compounds (specifically sulfonyl imines). These compounds have utility as intermediates in the synthesis of further compounds and in combinatorial chemistry techniques.
The present invention also discloses a process for the in situ use of N-unsubstituted imines of the structure III,
R
1
R
2
C═NH &em
E. I. du Pont Nemours and Company
O'Sullivan Peter
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