Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-03-19
2002-04-30
Aulakh, Charanjit S. (Department: 1612)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C424S617000, C548S112000, C548S365100, C548S373100, C548S375100, C548S376100, C548S377100
Reexamination Certificate
active
06380393
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to ligands, transition metal complexes including such ligands and methods of using such ligands and complexes. More particularly the invention relates to ligands including first and second hetero atoms, transition metal complexes of such ligands in which only one of the first and second hetero atoms are directly bonded to the metal moiety and methods of using such ligands and complexes, for example, to facilitate chemical reactions, such as hydrolysis, alcoholysis and aminolysis reactions and carbon dioxide conversion reactions.
Medicinal chemists and biochemists want to know how amino acids are arranged in proteins, so that they can better understand the correlation between structures and the functions of drugs. One of the techniques used to accomplish the task of protein structure determination requires the breaking of amide bonds to liberate the amino acids. However, at physiological temperatures and pH 9, it takes an impractical length of time, for example, 168 years, to break half the amide bonds in a sample. In contrast, organisms found in nature have remarkably efficient systems to make and break amide bonds. Scientists have used natural enzymes such as carboxypeptidase to do the task of amide bond cleavage
In some cases it is believed the crucial step involves proton transfer between imidazole, a carboxylate, and the amide undergoing hydrolysis while other enzymatic systems involve a metal catalyzed amide bond cleavage such as that seen in the zinc(II)-metalloprotease. However, the available enzymatic systems can be very complicated and sometimes difficult to handle due to their sensitivity to temperature and pH.
Catalysis of amide hydrolysis has been catalyzed not only by enzymes, but also by acids, bases, and metal ions. These systems take advantage of one or more possible factors which facilitate amide bond cleavage. First, the amide bond cleaving reagent or catalyst could act as a proton transfer reagent which can be an important factor in amide bond hydrolysis. Secondly, a metal may catalyze or mediate amide hydrolysis by acting as a Lewis acid through O-complexation, delivery of a metal coordinated hydroxide or a combination of the latter two processes.
Considerable work has been directed toward studying the amide hydrolysis reaction and the development of reagents which assist amide hydrolysis. Some work toward the development of an amide hydrolysis catalyst has been published by Kostic. For example, Kostic and coworkers have found that a palladium(II) complex can accomplish the hydrolysis of a number of dipeptides, but with only a modest 4 catalytic turnovers.
It would be advantageous to provide reaction facilitators, e.g., catalysts, promoters and the like, that mimic enzymatic systems in their hydrogen-bonding and/or proton transfer abilities, but are robust, simple to handle, and have useful reactor facilitation.
Industrial hydrolysis of acrylonitrile is used to make acrylic acid which, in turn, can be converted to a variety of esters such as methyl, ethyl, butyl, and 2-ethylhexyl acrylates. The acrylates can then be used as comonomers with methyl methacrylate and/or vinyl acetate to give polymers for water-based paints, among other products A number of industrial methods exist for obtaining acrylic acids from nitriles and one of the more economical methods is the direct hydrolysis of the acrylonitrile to the acrylic acid. However, this synthetic route involves the use of a stoichiometric amount of sulfuric acid to produce the acrylamide sulfate which is then treated with an alcohol to give the acrylic ester. It would be advantageous to provide a direct route from the acrylonitrile and alcohol to yield the desired acrylate without the need to use and then neutralize a strong acid
As petroleum resources dwindle and the need to control the emissions of carbon dioxide into the environment increases, use of carbon dioxide as a feedstock becomes more desirable. It would be advantageous to provide materials useful to facilitate carbon dioxide conversion, for example, to carbonates, carbamates and ureas.
SUMMARY OF INVENTION
New ligands, transition metal complexes including such ligands and methods for using such ligands and complexes have been discovered. The present ligands and transition metal complexes can be produced using relatively straightforward synthetic chemistry techniques. Moreover, the structures of the present ligands and metal complexes can be effectively selected or even controlled, for example, in terms of proton transfer ability and/or hydrogen bonding ability, thereby providing ligands and complexes with properties effective to facilitate one or more chemical reactions. Thus, the present metal complexes can be effectively used to facilitate, for example, catalyze, promote and the like, various chemical reactions, such as hydrolysis, alcoholysis and aminolysis reactions and carbon dioxide conversion reactions, which provide useful benefits. The present ligands and complexes have one or more other advantageous properties or characteristics which enhance their production and/or usefulness.
In one broad aspect of the present invention, compositions are provided which comprise at least one organic ligand and a transition metal moiety partially complexed by the organic ligand.
The present organic ligands, many of which themselves are novel and within the scope of the invention, include a first hetero atom and a second hetero atom directly bonded to the first hetero atom or located one carbon atom away from the first hetero atom. When the present organic ligands are complexed to the transition metal moiety, only one of the first and second hetero atom is directly bonded to the transition metal moiety, with the other of the first and second hetero atoms not being directly bonded to another transition metal moiety or being directly bonded to H (hydrogen atom). In addition, in the event the first and second hetero atoms are nitrogen and are located in a heterocycle and the organic ligand includes only a single additional hetero atom separated from the first or second hetero atoms by one or two carbon atoms, then the additional hetero atom is not included in an additional heterocycle. Also, if the organic ligand includes more than four hetero atoms, then the organic ligand includes at least one hetero atom other than nitrogen bonded directly to two (or more) other atoms. Alternately, if the organic ligand includes two pyrazole rings and at least two hetero atoms in the group connecting the two rings, then the organic ligand includes at least one hetero atom other than nitrogen.
In another embodiment, compositions within the scope of the present invention include an organic ligand having the following structure:
wherein the carbon atoms ortho to the nitrogen atoms in the two pendant heterocycles are bonded to a substituent other than —CH
3
(methyl); and a transition metal moiety partially complexed by the organic ligand.
In an additional embodiment, the present compositions include an organic ligand having the following structure:
The transition metal moiety partially complexed with this organic ligand preferably is other than ruthenium.
The present organic ligands can be very effectively structured and adapted to control the proton transfer ability and/or hydrogen bonding ability of the transition metal complex of which the ligand is a part. In other words, the present ligands can be selected to obtain the desired degree of proton transfer ability and/or hydrogen bonding ability so that the resulting transition metal complex is highly effective in the desired application, for example, in facilitating a particular or specific chemical reaction. Such adaptability is very useful in providing the proper or desired degree of proton transfer and/or hydrogen bonding to achieve the desired degree of facilitation of a number of important chemical reactions, for example, hydrolysis, alcoholysis and aminolysis reactions, carbon dioxide conversion reactions, and reactions of alkenes or alkynes with water, a
Combs David
Grotjahn Douglas Bryan
Aulakh Charanjit S.
San Diego State University Foundation
Stout, Uxa, Boyan & Mullins, LLP
Uxa Frank J.
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