Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-01-05
2002-05-14
Solola, T. A. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06388093
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to syntheses for preparing 1,4-diketopyrrolo[3,4-c]pyrroles useful as pigments or intermediates in the coloration of plastics, paints and printing inks.
2. Description of Related Art
A variety of syntheses exist in the prior art for the preparation of 1,4-diketopyrrolo[3,4-c]pyrroles of the general formula:
wherein R
1
to R
4
are commonly used substituent groups such as alkyl or hydrogen. For example, U.S. Pat. No. 4,415,685 discloses preparing a 1,4-diketopyrrolo[3,4-c]pyrrole, where R
1
and R
3
are hydrogen and R
2
and R
4
are phenyl, by heating benzonitrile with bromoacetic ester and zinc in toluene. Alternatively, 1,4-diketopyrrolo [3,4-c]pyrrole derivatives where R
2
and R
4
are different and prepared by subsequently introducing the substituent groups or by converting pre-existing precursor substituent groups via halogenation, acylation, sulfochlorination, etc. which may be followed by reaction of the sulfochloride, for example with an amine, alcohol or phenol.
U.S. Pat. No. 4,579,949 describes a process for preparing structurally similar pyrolopyrroles where R
2
and R
4
are each independently isocyclic or heterocyclic aromatic radicals by reacting disuccinate with a nitrile of the general formula R
2
—CN or R
4
—CN in an organic solvent and strong base at elevated temperatures followed by a hydrolysis step.
U.S. Pat. No. 4,931,566 represents an improvement over the process described in U.S. Pat. No. 4,579,949 wherein the hydrolysis step is carried out in stages.
U.S. Pat. No. 4,659,775 describes a process for preparing these pyrrolopyrroles by reacting an amino ester or pyrrolinone containing the R
2
substituent with a nitrile of the general formula R
4
—CN, where R
4
represents an alkyl or aralkyl group or an isocyclic or heterocyclic or aromatic radical, in a strong base and an organic solvent.
U.S. Pat. No. 4,585,878 describes two processes for preparing N-substituted 1,4-diketopyrrolo[3,4-c]pyrroles. The first involves reacting a 1,4-diketopyrrolo [3,4-c]-pyrrole, where R
1
and R
3
are hydrogen, with a compound containing the radicals replacing R
1
and R
3
as leaving groups, in an organic solvent. The second method involves reacting a compound of the formula R
2
—CH═N—R
3
or R
4
—CH═N—R
1
or both with a succinic acid diester in a base and organic solvent, then dehydrogenating the resulting product.
An object of the present invention is to provide an m improved synthesis for preparing asymmetrical or symmetrical 1,4-diketo pyrrolo[3,4-c]pyrroles from one or more &bgr;-ketoamides.
SUMMARY OF THE INVENTION
The first synthesis of the present invention involves a reaction between a halogenated &bgr;-ketoamide and an alkaline metal or alkaline earth salt of a &bgr;-ketoamide to produce a succinamide, which is then heated in the presence of a Lewis Acid or acid chloride to produce a 1,4-diketopyrrolo[3,4-c]pyrrole.
The second synthesis of the present invention involves an oxidative dimerization of an alkali metal or alkaline earth salt of a &bgr;-ketoamide to form a succinamide, which is then heated in the presence of a Lewis Acid or acid chloride to produce a 1,4-diketopyrrolo[3,4-c]pyrrole. diketopyrrolo[3,4-c]pyrrole.
An advantage of the syntheses of the present invention is the flexibility, in that a wide variety of either symmetrical or asymmetrical 1,4-diketopyrrolo[3,4-c]pyrroles can be produced.
In one aspect, the present invention relates to a synthesis for preparing asymmetrical or symmetrical 1,4-diketo pyrrolo[3,4-c]pyrrole of formula I:
wherein R
1
, R
2
, R
3
and R
4
are each independently selected from hydrogen, C
1
-C
2
alkyls, cycloalkyls, aralkyls, or isocyclic or heterocyclic aromatic radicals comprising the steps of:
(a) reacting a &bgr;-ketoamide of either formula II:
or wherein R
2
and R
4
are each independently selected from hydrogen, C
1
-C
20
alkyls, cycloalkyls, aralkyls, or isocyclic or heterocyclic aromatic radicals or a &bgr;-ketoamide of formula III:
wherein R
2
and R
1
are each independently selected from hydrogen, C
1
-C
20
alkyls, cycloalkyls, aralkyls, or isocyclic or heterocyclic aromatic radicals, with a strong base to form an alkali metal or alkaline earth salt;
(b) halogenating &bgr;-ketoamide of formula II or formula III, thereby forming a halogenated &bgr;-ketoamide;
(c) reacting said alkali or alkaline earth metal salt with said halogenated &bgr;-ketoamide, thereby forming a succinamide of the formula VI:
wherein R
1
and R
2
are each independently selected from hydrogen, C
1
-C
20
alkyls, cycloalkyls, aralkyls, or isocyclic or heterocyclic aromatic radicals;
(d) heating the succinamide of Formula IV in the presence of a Lewis acid or acid chloride.
In another aspect, the present invention relates to a synthesis for preparing a symmetrical 1,4-diketopyrrolo[3,4-c]pyrrole conforming to formula V:
wherein R
1
and R
s
are as previously defined; comprising the steps of:
(a) reacting a &bgr;-ketoamide conforming to formula II:
wherein R
4
and R
1
are each independently selected from hydrogen, C
1
-C
20
alkyls, cycloalkyls, aralkyls, or isocyclic or heterocyclic aromatic radicals with a strong base to form an alkali or alkaline earth metal salt;
(b) oxidatively dimerizing said alkali or alkaline earth metal salt, thereby forming a succinamide of formula VI:
wherein R
1
, R
2
, R
3
and R
4
are each independently selected from hydrogen, C
1
-C
20
alkyls, cycloalkyls, aralkyls, or isocyclic or heterocyclic aromatic radicals; and
(c) heating said succinamide of formula IV in the presence of a Lewis Acid or acid chloride to effect ring closure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Step (a) of the asymmetrical of symmetrical synthesis of the present invention comprises reacting a &bgr;-ketoamide conforming to either formula II or III with a strong base to form an alkali metal or alkaline earth metal salt &bgr;-ketoamide. This reaction IV may be conducted in a non-reactive organic solvent at temperatures of from about 20 to about 140° C., more preferably 20 to 100° C. The particular temperature employed for forming of the metal &bgr;-ketoamide salt will depend on the temperature required to solubilize the amide.
Suitable non-reactive organic solvents include n-octane, n-decane, benzene, ethylbenzene, toluene, xylene, chlorobenzene, decalin and the like.
As for the strong base, examples include alkali metal hydroxides such as sodium, potassium and lithium hydroxide; alkaline earth metal hydroxides such as calcium and magnesium hydroxide; alkali metal amides such as sodium, potassium and lithium amide, diethylamide, diisopropylamide or isopropylcyclo-hexylamide; and alkali metal hydrides such as sodium, potassium or lithium hydride, as well as alkali metal or alkaline earth metal alcoholates derived from primary, secondary or tertiary C
1
-C
10
alcohols e.g. sodium, potassium or lithium methylate, ethylate, n-propylate, isopropylate, n-butylate, sec-butylate, tert-butylate, 2-methyl-2-butylate, 2-methyl-2-pentylate, 3-methyl-3-pentylate, 3-ethyl-pentylate, or alkali metal or alkaline earth metal phenolates, o-alkyl substituted phenolates, such as sodium or potassium o-cresolate.
It is preferred to use an alkali metal amide, hydride or alcoholate to form the metal amide salt and it is particularly preferred that the alkali metal be sodium or potassium. If alcoholates are employed, it is preferred that the alcohol moiety be derived from a secondary or tertiary alcohol such as isopropyl alcohol, sec- or tert-butyl alcohol and tert-amyl alcohol. If desired, the alkali metal alcoholates may be prepared in situ by reacting the appropriate alcohol with the desired alkali metal, alkali metal hydride or alkali metal amide.
The starting material for step (a) of the first synthesis is a &bgr;-ketoamide of either formula II:
or formula III:
where R
1
, R
2
, R
3
and R
4
are each indepen
Chamberlain Terrence R.
Thornley Craig
Thornley Jack
Anderson Rebecca
Persley Sidney
Solola T. A.
Sun Chemical Corporation
Thornley Jack
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