Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-03-21
2002-02-26
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S357000, C568S399000, C568S471000
Reexamination Certificate
active
06350916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the selective oxidation of alcohols to aldehydes or ketones by using an aryl chloride, e.g., chlorobenzene, as an oxidant. The process involves reacting a mixture of the alcohol, aryl chloride, and a base in the presence of metal-ligand complex or composition as a catalyst.
BACKGROUND OF THE INVENTION
Ancillary (or spectator) ligand-metal coordination complexes (e.g. organometallic complexes) and compositions are useful as catalysts, additives, stoichiometric reagents, monomers, solid state precursors, therapeutic reagents and drugs. Certain known ancillary ligand-metal complexes and compositions are catalysts for reactions such as oxidation, reduction, hydrogenation, and other transformations. Metal-ligand composition or complex catalyzed selective oxidations of alcohols to aldehydes and ketones typically involve an oxygen atom containing oxidant, e.g., air, oxygen and hydrogen peroxide based oxidations.
Other oxidations of alcohols to ketones or aldehydes based on non-oxygen atom containing oxidants are relatively rare. Examples include oxidations based on aryl bromides (see, e.g., Tamaru, Y. et al., “Oxidation of Primary and Secondary Alcohols by the Catalysis of Palladium,”
J. Org. Chem
. 1983, 48, pp. 1286-1292 and Tamaru, Y., et al., “Palladium Catalyzed Oxidations of Secondary Alcohols,”
Tet. Lett
. 1979, 16, pp. 1401-1404) and aliphatic chlorides (see, e.g., Nagashima, H., et al., “Activation of Polyhaloalkanes by Palladium Catalyst: Palladium Catalyzed Oxidation of Alcohols to Carbonyl Compounds with Carbon Tetrachloride,”
Chem. Lett
. 1981, pp. 1171-1172; Tsuji, J. et al., “A Palladium Catalyzed Conversion of Halohydrins to Ketones,”
Tet. Lett
. 1982, pp. 3085-3088; and Bouquillon, S., et al., “Critical Role of the Coordination Environment of Palladium Dichloride on the Course of Its Reaction with Secondary Benzylic Alcohols: Selective Oxidation or Etherification Catalysts,” Organometallics 2000, web edition released Mar. 8, 2000). However, these oxidations based on non-oxygen atom containing oxidants are industrially less attractive due to the high cost of aryl bromide and aliphatic chloride oxidants and/or industrially incompatible or unfavorable reaction conditions.
Others have studied a related reaction that forms an ether. The predominant formation of aryl ether products has been previously described to be favored under similar reaction conditions. See, e.g., Mann, G., et al., “Palladium-Catalyzed C—O Coupling Involving Unactivagted Aryl Halides: Sterically Induced Reductive Elimination To Form the C—O Bond in Diaryl Ethers,”
J. Am. Chem. Soc
., 1999, 121, pp. 3224-3225 and Aranyos, A., et al., “Novel Electron-Rich Bulky Phosphine Ligands Facilitate the Palladium-Catalyzed Preparation of Diaryl Ethers,”
J. Am. Chem. Soc
., 1999, 121, pp. 4369-4378.
Despite these attempts, the oxidation of alcohols to the corresponding aldehydes and ketones remains one of the most fundamental and important processes in organic synthesis that has not achieved very economical and environmental conditions. These oxidations are common reactions that are used to make many types of pharmaceuticals. Thus, those of skill in the art have long desired to replace the known processes with a process that does not require the use of expensive raw materials or processes that use environmentally hazardous heavy metals in stoichiometric or excess amounts.
SUMMARY OF THE INVENTION
This invention, then, overcomes at least some of the problems associated with the commercial oxidation of alcohols to the corresponding ketones or aldehydes. The present invention is directed toward the use of aryl chloride oxidants (such as chlorobenzene), which are relatively inexpensive and often used as solvent in industrial processes. This invention offers the additional benefit of allowing the starting alcohol substrate to contain other functionalities (such as sulfur or double or triple bonds) that do not oxidize under the reaction conditions employed. Moreover, the reactions of the present invention are performed at lower pressures than traditional oxidations, since the oxidant is typically in liquid form.
The present invention offers a process for the selective oxidation of alcohols to useful aldehydes and ketones by reacting a mixture of an alcohol, aryl chloride and a base in the presence of metal-ligand complex or composition as a catalyst and a suitable solvent. The products are the corresponding ketone or aldehyde of the starting alcohol substrate and benzene or benzene derivative of the aryl chloride. The invention identifies process conditions, which surprisingly result in the selective and predominant formation of aldehyde and ketone products rather than aryl ether products.
Thus, it is an object of this invention to provide a process for the oxidation of alcohols to ketones or aldehydes using aryl chloride.
It is another object of this invention to provide a process for the selective oxidation of alcohols to ketones or aldehydes where the alcohol comprises other reactive functionalities.
It is a further object of this invention to oxidize alcohols to ketones or aldehydes at lower reaction pressures.
It is yet a further object of this invention to oxidize alcohols to ketones or aldehydes at economically and/or environmentally sound conditions.
These and other objects of the invention are accomplished through a reaction using suitable metal-ligand compositions or complexes that can be generated in situ or separately by adding suitable ligands to suitable precursor metals. Suitable ligands of this process can be characterized by the general formulas PR
3
, NR
3
, SR
2
, OR
2
, or :CR
2
(carbenes) wherein each R is independently selected from the group consisting of hydrocarbyl (e.g., alkyl, alkenyl, alkynyl, aryl, alkaryl, aralkyl, etc.), substituted hydrocarbyl (e.g., substituted alkyl, alkenyl, alkynyl, aryl, aralkyl, alkaryl, etc.), heteroatom-containing hydrocarbyl (e.g., heteroatom-containing alkyl, alkenyl, alkynyl, aryl, aralkyl, alkaryl, etc.) and substituted heteroatom-containing hydrocarbyl (e.g., substituted heteroatom-containing alkyl, alkenyl, alkynyl, aryl, aralkyl, alkaryl, etc.). Suitable precursor metal complexes can be characterized by the form ML
n
wherein M is a transition metal, preferably Pd, Ni, Ru, Rh, Co, Ir, and most preferably Pd and Ni and L is a suitable neutral or charged organic or inorganic fragment or solid support. Suitable bases of this process can be organic and inorganic compounds such as amines, alkali and alkaline earth metal carbonates, phosphates, alkoxides, hydroxides and fluorides. Suitable solvents include hydrocarbons, ethers, ketones, alcohols, and nitrites. Optionally the starting alcohol substrate could be used as the solvent.
Further aspects of this invention will be evident to those of skill in the art upon review of this specification.
DETAILED DESCRIPTION OF THE INVENTION
It is to be understood that unless otherwise indicated this invention is not limited to specific reactants, catalyst compositions (including heteroatom-containing activators and acids), or synthetic methods. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
As used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, reference to “a reagent” includes mixtures of reagents, “a base” includes mixtures of bases, “a catalyst composition” includes mixtures of catalyst compositions, and the like.
In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. A named R group will generally have the structure that is recognized in the art as corresponding to R groups having that name. For the purposes of illustration, representative R groups as enumerated above are defined herein. These definitions are intended to supplement and
Bei Xiaohong
Guram Anil
Padmanabhan Sreeni
Symyx Technologies Inc.
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