Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-05-20
2001-04-03
Kight, John (Department: 1612)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06211378
ABSTRACT:
The instant process pertains to an environmentally friendly process for making 4-functionalized N—OR derivatives of 2,2,6,6-tetraalkylpiperidines.
BACKGROUND OF THE INVENTION
The hydrogen peroxide oxidation of 2,2,6,6-tetramethylpiperidines with hydrogen peroxide alone, or with carbonate catalyst, of with divalent metal catalyst is known. U.S. Pat. Nos. 5,654,434 and 5,777,126 describe the oxidation using hydrogen peroxide alone. U.S. Pat. No. 5,629,426 discloses the use of carbonate catalyzed hydrogen peroxide oxidations. U.S. Pat. No. 5,416,215 describes the use of divalent metal catalysts for the hydrogen peroxide oxidation reaction.
E. G. Rozantsev et al., Synthesis, 1971, 190 disclose the use of tungstate catalyst for the hydrogen peroxide oxidation of 2,2,6,6-tetramethylpiperidines.
U.S. Pat. No. 5,204,473 describes the use of tert-butyl hydroperoxide for the oxidation of 2,2,6,6-tetramethylpiperidines to the corresponding N-oxyl compounds. I. Q. Li et al., Macromolecules 1996, 29, 8554 and T. J. Connolly et al., Tetrahedron Letters, 1996, 37, 4919 describe the use of di-tert-butyl peroxide for the same purpose.
G. G. Barclay et al., Macromolecules, 1997, (30), 1929 describe the formation of a diadduct of a nitroxyl with an activated double bond (styrene).
L. J. Johnson et al., J. of Organic Chem., 1986, (51), 2806 describe the photochemical hydrogen atom abstraction by nitroxyls followed by N—OR formation.
T. J. Connolly et al., Tetrahedron Letters, 1997, (38), 1133 disclose the thermal abstraction of benzylic hydrogen atoms followed by N—OR formation.
I. A. Opeida et al., Kinetics and Catalysts, 1995, (36), 441 (translation from Russian) also describe the thermal abstraction of benzylic hydrogen atoms.
The instant process differs significantly from each of these prior art references and provides the use of environmentally friendly hydrogen peroxide with water as an oxidation by-product. The formation of 4-functionalized N—OR derivatives is obtained without the use of organic peroxides and hydroperoxides.
DETAILED DISCLOSURE
The instant process involves two steps for the preparation of a selected N—OR derivative of the 2,2,6,6-tetraalkylpiperidines with a third step involving the recycling of the N—OH obtained concomitantly with the desired N—OR compound back to the corresponding N-oxyl starting material for the second step.
The overall process is outlined below:
Step 1 (preparing an N-oxyl compound by oxidation with hydrogen peroxide)
Step 2 (reacting two equivalents of N-oxyl with one allylic, benzylic or activated methine compound (R—H) to form one equivalent of N—OH and one equivalent of N—OR compound)
Step 3 (recycling the N—OH compound formed in Step 2 back to the N-oxyl compound needed as intermediate for Step 2)
In the formulas A, B, C and D,
G
1
and G
2
are independently alkyl of 1 to 4 carbon atoms, preferably methyl, or G
1
and G
2
together are pentamethylene;
X is hydrogen, hydroxyl, oxo, —NH—CO—E, —O—CO—E or —NH—CO—NH—E, where E is alkyl of 1 to 18 carbon atoms, said alkyl substituted by hydroxyl or E is aryl of 6 to 10 carbon atoms; and
R is as defined below.
In Step 2, the R—H compound is an allylic, benzylic or activated methine compound where the H-atom is highly vulnerable to being extracted by the N-oxyl radical so that the two equivalents of N-oxyl compound essentially react with one equivalent of R—H compound to undergo a disproportionation reaction give one equivalent of N—OR and one equivalent of N—OH. For environmental and economic concerns, it is most expedient to recycle the N—OH compound prepared in Step 3 back to the starting N-oxyl intermediate needed in Step 2.
Preferably, in the compounds of R—H which are allylic in nature, R is an alkenyl of 3 to 20 carbon atoms such as cyclohexene, 1,5-cyclooctadiene, cyclooctene, 1-octene, allylbenzene, &agr;-methylstyrene or &bgr;-methylstyrene (1-phenyl-1-propene), and in the compounds of R—H which are benzylic, R—H is a compound of formula Y—CH—Z where Y and Z are independently, hydrogen, alkyl of 1 to 18 carbon atoms, aryl of 6 to 10 carbon atoms or said aryl substituted by one to four alkyl groups of 1 to 4 carbon atoms, provided that at least one of Y and Z is aryl and where is Y is aryl, then Z can be part of a fused ring system having methylene groups such as 1,2,3,4-tetrahydronaphthalene, toluene, o-xylene, m-xylene, p-xylene, diphenylmethane, ethylbenzene, mesitylene or durene.
Most preferably, in Step 2, the compound R—H is cyclohexene, 1,5-cyclooctadiene, cyclooctene, 1-octene, &agr;-methylstyrene, &bgr;-methylstyrene, toluene, m-xylene, p-xylene, diphenylmethane or ethylbenzene.
Most preferably, in Step 2, the oxyl compound of formula B is 1-oxyl4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-oxyl-4-acetamido-2,2,6,6-tetramethylpiperidine, 1-oxyl-4-oxo-2,2,6,6-tetramethylpiperidine or 1-oxyl-4-benzoyloxy-2,2,6,6-tetramethylpiperidine.
The instant invention also pertains to the independent process of Step 2 and to the independent process comprising Step 2 and Step 3 together.
Preferably, in Step 1 and in Step 3, the concentration of aqueous hydrogen peroxide is 30% by weight or higher. Aqueous hydrogen peroxide of 30%, 50% or 70% by weight are effective.
Step 1 and Step 3 can be carried out where the hydrogen peroxide oxidation as taught by U.S. Pat. Nos. 5,654,434 and 5,777,126 without catalyst; or as taught by U.S. Pat. No. 5,629,426 using a carbonate catalyst
The hydrogen peroxide oxidation of Step 1 and Step 3 can also be carried out in the presence of a tungstate catalyst or divalent metal salts.
Step 2 can be carried out in the absence of solvent or in the presence of an inert solvent such a chlorobenzene.
Step 2 can be carried out at a temperature of 50 to 140° C. at atmospheric pressure or at 50 to 140° C. in a pressure vessel.
REFERENCES:
patent: 5204473 (1993-04-01), Winter et al.
patent: 5416215 (1995-05-01), Büschken et al.
patent: 5629426 (1997-05-01), Pastor et al.
patent: 5654434 (1997-08-01), Pastor et al.
patent: 5777126 (1998-07-01), Pastor et al.
E. G. Rozantsev et al., Synthesis, 1971, 190.
I. Q. Li et al., Macromolecules 1996, 29,8554.
T. J. Connolly et al., Tetrahedron Letters, 1996, 37,4919.
I. A. Opeida, et al., Kinetics and Catalysts, 1995, (36),441.
Linda J. Johnston, et al., J. Org. Chem., vol. 51, No. 14, 1986, 2807.
Davenport, et al., Macromolecules, vol. 30, No. 7, 1997, 1930.
Terrence J. Connolly, et al., Tetrahedron Letters, vol. 38, No. 7, pp. 1133-1136, 1997.
Babiarz Joseph E.
Cunkle Glen T.
Pastor Stephen D.
Ciba Specialty Chemicals Corporation
Covington Raymond
Hall Luther A. R.
Kight John
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