Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-08-28
2001-08-07
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C544S170000, C544S383000, C548S215000, C548S542000
Reexamination Certificate
active
06271382
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for preparing an organic compound having a nitroxide free radial of the formula (2):
wherein T is a methylene group, an ethylene group, an oxygen atom or a methyleneoxy group; R is an alkyl group, an aralkyl group, an aryl group, a cycloalkyl group, an alkoxy group, an acyl group an acyloxy group, an amino group, a hydroxyl group or a heterocyclic group; R
1
, R
2
, R
3
and R
4
are the same or different and each an alkyl group or an aryl group, or R
1
and R
2
and/or R
3
and R
4
together form a tetramethylene group or a pentamethylene group; and n is an integer of 0 to 6. This compound will be referred to as the “nitroxide compound (2)”.
The nitroxide compound (2) is useful as a spin label or a spin probe used in the ESR spectrum analysis, a polymerization inhibitor for unsaturated compound, or a stabilizer of organic polymers against thermal decomposition and photochemical decomposition.
BACKGROUND ART
It is known that an organic compound having a nitroxide free radical such as the nitroxide compound (2) is prepared by oxidizing a secondary amine having a steric hindrance with a peroxide. That is, the nitroxide compound (2) can be prepared by oxidizing a cyclic secondary amine having a steric hindrance of the formula (1):
wherein T, R, R
1
, R
2
, R
3
, R
4
and n are the same as defined above with a peroxide.
However, when 2,2,6,6-tetramethylpiperidine is used as a cyclic secondary amine (1) and it is oxidized to obtain 2,2,6,6-tetramethylpiperidine-N-oxyl, industrially satisfactory results are not attained, for example, the yield of the desired product is low as understood from the result of Comparative Examples described below, and the reaction time is long.
DISCLOSURE OF THE INVENTION
One object of the present invention is to provide a process for preparing the nitroxide compound (2) by oxidizing the cyclic secondary amine (1) with a peroxide at a high yield in a short reaction time.
The present inventors have made extensive study to solve the above problems. As a result, it has been found that the nitroxide compound (2) can be obtained at a high yield in a short reaction time, when the cyclic secondary amine (1) is reacted with the peroxide in the presence of at least 1 wt. part of an organic compound having a cyano group per 1 wt. part of the cyclic secondary amine (1), and the present invention has been completed.
Accordingly, the present invention provides a process for preparing the nitroxide compound (2) comprising the step of reacting a cyclic secondary amine of the formula (1):
with a peroxide in the presence of at least 1 wt. part of an organic compound having acyano group per 1 wt. part of the cyclic secondary amine (1).
REFERENCES:
patent: 3502692 (1970-03-01), Feldman et al.
patent: 5218116 (1993-06-01), Neri et al.
patent: 5436345 (1995-07-01), Lewis et al.
patent: 5777126 (1998-07-01), Pastor et al.
patent: 6-247932 (1994-09-01), None
patent: 8-3136 (1996-01-01), None
Higel Floyd D.
Koei Chemical Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
Wright Sonya N.
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