# US 7,608,742 B2 · Diarylphenoxy aluminum compounds

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- Number: US 7,608,742 B2
- Document ID: US7608742B2
- Status: Granted
- Kind: B2
- Application number: 11/817,468
- Filed: 2006-03-03
- Published: 2008-07-10
- Granted: 2009-10-27
- Earliest claimed: 2005-03-03
- Assignees: BASF SE
- Inventors: Marko Friedrich; Klaus Ebel; Norbert Götz; Wolfgang Krause; Christian Zahm
- Web page: https://patentgrep.com/patent/US7608742B2

## CPC

- C07F 5/069: {without C-aluminium linkages}
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)

## Abstract

The present invention relates to diarylphenoxyaluminum compounds which are obtainable by reacting a bis(diarylphenol) ligand of the formula (I) with an alkylaluminum compound and/or a complex aluminum hydride. The invention moreover relates to the use of such diarylphenoxyaluminum compounds as catalysts. Moreover, the invention relates to a method of producing isopulegol by cyclization of citronellal in the presence of diarylphenoxyaluminum compounds as catalysts. The invention also relates to a method of producing menthol by cyclization of citronellal in the presence of diarylphenoxyaluminum compounds as catalysts and subsequent hydrogenation.

## Claims

### Claim 1

A diarylphenoxyaluminum compound obtainable by reacting a bis(diarylphenol) ligand of the formula (I)
wherein
Ar1, Ar2, Ar3 and Ar4 are identical or different and in each case, independently of one another, are an aryl radical having 6 to 15 carbon atoms or a heteroaryl radical having 2 to 15 carbon atoms which, optionally can in each case carry 1 to 7 identical or different substituents selected from the group of substituents C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alkoxy, C7- to C12-aralkyl, halogen, —SiR5aR6aR7a, substituted or unsubstituted C6- to C10-aryl, —NR8aR9a, —SR10a or —NO2,
R1, R2, R3 and R4 are identical or different and in each case, independently of one another, are hydrogen, C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-allcoxy, C7- to C12-aralkyl, halogen, —SiR5bR6bR7b, substituted or unsubstituted C6- to C10-aryl, —NR8bR9b, —SR10b, —NO2, and R1 or R2 and/or R3 or R4, together with A, can form a cyclic aromatic or nonaromatic cycle, and
A is A(1), A(2) or A(3),
A(1) is a straight-chain or branched and/or cyclic hydrocarbon radical having 1 to 25 carbon atoms which is optionally saturated or mono- or polyunsaturated and/or partially aromatic and optionally can have one or more identical or different hetero atoms selected from the group consisting of hetero atoms O, S and NR11, and/or one or more identical or different functional groups selected from the group consisting of functional groups C(O), S(O) and S(O)2, and, optionally can carry one or more identical or different substituents selected from substituents C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alloxy, C1- to C10-acyloxy, C7- to C12-aralkyl, halogen, —SiR5cR6cR7c, substituted or unsubstituted C6- to C10-aryl, substituted or unsubstituted C2- to C10-hetaryl, —NR8cR9c, —SR10c, —NO2, C1-to C12-acyl, or C1- to C10-carboxyl,
A(2) is an aryl radical having 6 to 15 carbon atoms or a heteroaryl radical having 2 to 15 carbon atoms which, optionally can in each case carry 1 to 5 substituents, selected from the group of substituents C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alkoxy, C7- to C12-aralkyl, halogen, —SiR5dR6dR7d, substituted or unsubstituted C6- to C10-aryl, —NR8dR9d, SR10d or NO2,
A(3) is a functional group or a hetero atom selected from the group consisting of —O—, —S—, —N(R11)—, —S(O)—, —C(O)—, S(O)2—, —P(R11), —(R11)P(O)— and Si(R12R13),
wherein the radicals R5a, R6a, R7a, R8a, R9a, R10a to R5d, R6d, R7d, R8d, R9d, R10d and R11 to R13 are in each case, independently of one another, C1- to C6-alkyl, C7- to C12-aralkyl and/or substituted or unsubstituted C6- to C10-aryl, and the radicals R8a and R9a, R8b and R9b, R8c and R9c, R8d and R9d, independently of one another, can in each case together also form a cyclic hydrocarbon radical having 2 to 8 carbon atoms which can have one or more identical or different hetero atoms selected from the group consisting of O, S and NP11a and R11a can have the meanings given for R11,
with an aluminum compound of the formula (II) or formula (III) or a mixture of compounds of the formulas (II) and (III)
(R14)3-pAlHp (II),
wherein
Al is aluminum and
R14 is a branched or unbranched alkyl radical having 1 to 5 carbon atoms and
p is 0 or an integer from 1 to 3,
MAlH4 (III),
wherein
Al is aluminum and
M is lithium, sodium or potassium.

### Claim 2 (depends on 1)

The diarylphenoxyaluminum compound according to claim 1, obtainable by reacting a bis(diarylphenol) ligand of the formula (Ia)
wherein the radicals Ar1 to Ar4, R1 to R4 and A have the meanings given in claim 1.

### Claim 3 (depends on 1)

The diarylphenoxyaluminum compound according to claim 1, wherein the radicals Ar1 to Ar4 are phenyl.

### Claim 4 (depends on 1)

The diarylphenoxyaluminum compound according to claim 1, wherein the radicals R1 to R4 are hydrogen.

### Claim 5 (depends on 1)

The diarylphenoxyaluminum compound according to claim 1, wherein the bis(diarylphenol) ligand of the formula (I) and the aluminum compounds of the formulae (II) and/or (III) are used in a molar ratio of from 10:1 to 1:1.

### Claim 6 (depends on 1)

The diarylphenoxyaluminum compound according to claim 1, wherein the bis(diarylphenol) ligand of the formula (I) and the aluminum compounds of the formulae (II) and/or (III) are used in a molar ratio of 3:2.

### Claim 7

A method of producing isopulegol of the formula (IV)
comprising cyclization of a citronellal of the formula (V)
in the presence of a catalyst which is obtainable by reacting a bis(diarylphenol) ligand of the formula (I)
wherein
Ar1, Ar2, Ar3 and Ar4 are identical or different and in each case, independently of one another, are an aryl radical having 6 to 15 carbon atoms or a heteroaryl radical having 2 to 15 carbon atoms which, optionally can in each case carry 1 to 7 identical or different substituents selected from the group of substituents C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alkoxy, C7- to C12-aralkyl, halogen, —SiR5aR6aR7a, substituted or unsubstituted C6- to C10-aryl, —NR8aR9a, —SR10a or —NO2,
R1, R2, R3 and R4 are identical or different and in each case, independently of one another, are hydrogen, C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alkoxy, C7- to C12-aralkyl, halogen, —SiR5bR6bR7b, substituted or unsubstituted C6- to C10-aryl, —NR8bR9b, —SR10b, —NO2, and R1 or R2 and/or R3 or R4, together with A, can form a cyclic aromatic or nonaromatic cycle, and
A is A(1), A(2) or A(3),
A (1) is a straight-chain or branched and/or cyclic hydrocarbon radical having 1 to 25 carbon atoms which is optionally saturated or mono- or polyunsaturated and/or partially aromatic and optionally can have one or more identical or different hetero atoms selected from the group consisting of hetero atoms O, S and NR11, and/or one or more identical or different functional groups selected from the group consisting of functional groups C(O), S(O) and S(O)2, and, optionally can carry one or more identical or different substituents selected from substituents C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alkoxy, C1- to C10-acyloxy, C7- to C12-aralkyl, halogen, —SiR5cR6cR7c, substituted or unsubstituted C6- to C10-aryl, substituted or unsubstituted C2- to C10-hetaryl, —NR8cR9c, —SR10c, —NO2, C1-to C12-acyl, or C1- to C10-carboxyl,
A(2) is an aryl radical having 6 to 15 carbon atoms or a heteroaryl radical having 2 to 15 carbon atoms which, optionally can in each case carry 1 to 5 substituents, selected from the group of substituents C1- to C6-alkyl, C1- to C6-perfluoroalkyl, C1- to C6-alkoxy, C7- to C12-aralkyl, halogen, —SiR5dR6dR7d, substituted or unsubstituted C6- to C10-aryl, —NR8dR9d, SR10d or NO2,
A(3) is a functional group or a hetero atom selected from the group consisting of —O—, —S—, —N(R11)—, —S(O)—, —C(O)—, —S(O)2—, —P(R11)—, —(R11)P(O)— and —Si(R12R13),
wherein the radicals R5a, R6a, R7a, R8a, R9a, R10a to R5d, R6d, R7d, R8d, R9d, R10d and R11 to R13 are in each case, independently of one another, C1- to C6-alkyl, C7- to C12-aralkyl and/or substituted or unsubstituted C6- to C10-aryl, and the radicals R8a and R9a, R8b and R9b, R8c and R9c, R8d and R9d, independently of one another, can in each case together also form a cyclic hydrocarbon radical having 2 to 8 carbon atoms which can have one or more identical or different hetero atoms selected from the group consisting of O, S and NR11a and R11a can have the meanings given for R11,
with an aluminum compound of the formula (II) or formula (III) or a mixture of compounds of the formulas (II) and (III),
(R14)3-pAlHp (II),
wherein
Al is aluminum and
R14 is a branched or unbranched alkyl radical having 1 to 5 carbon atoms and
p is 0 or an integer from 1 to 3,
MAlH4 (III),
wherein
Al is aluminum and
M is lithium, sodium or potassium.

### Claim 8 (depends on 7)

The method according to claim 7, wherein the cyclization is carried out in the presence of a catalyst which is obtainable by reacting a bis(diarylphenol) ligand of the formula (Ia)
wherein
Ar1, Ar2, Ar3, Ar4, R1, R2, R3, R4 and A are defined in claim 7.

### Claim 9 (depends on 7)

The method according to claim 7 for producing optically active isopulegol of the formula (IVa)
comprising the cyclization of optically active citronellal of the formula (Va)
wherein (*) refers in each case to an asymmetric carbon atom.

### Claim 10 (depends on 7)

The method according to claim 7 for producing L-(−)-isopulegol comprising the cyclization of D-(+)-citronellal and the aluminum compound used is a compound of the formula (II).

### Claim 11 (depends on 7)

The method according to claim 7, wherein the aluminum compound used is trimethylaluminum or triethylaluminum.

### Claim 12 (depends on 7)

The method according to claim 7, wherein the bis(diarylphenol) ligand of the formula (I) and the aluminum compounds of the formulae (II) and/or (III) are used in a molar ratio of from 10:1 to 1:1.

### Claim 13 (depends on 7)

The method according to claim 7, wherein the bis(diarylphenol) ligand of the formula (I) and the aluminum compounds of the formulae (II) and/or (III) are used in a molar ratio of 1.5:1.

### Claim 14 (depends on 7)

The method according to claim 7, wherein the cyclization is carried out in the presence of an organic acid.

### Claim 15 (depends on 14)

The method according to claim 14, wherein the organic acid used is acetic acid.

### Claim 16 (depends on 7)

The method according to claim 7, wherein the cyclization is carried out in the presence of at least one compound selected from the group of carboxylic acid anhydrides, aldehydes, ketones and vinyl ethers.

### Claim 17 (depends on 16)

The method according to claim 16, wherein the cyclization is carried out in the presence of a carboxylic acid anhydride of the formula (VI)
wherein
R20 and R20′ are identical or different and are a branched or unbranched C1- to C12-alkyl radical or C7- to C12-aralkyl radical or a C6- to C10-aryl radical, wherein the specified radicals can in each case have one or more identical or different substituents selected from the group consisting of OR10e, SR10e, NR8eR9e and halogen and wherein R20 and R20′ can together also form a 5- to 8-membered ring which can have one or more ethylenic double bonds and one or more identical or different hetero atoms selected from the group consisting of O, S and NR11b and wherein R10e, R10f, R8e, R9e and R11b, independently of one another, can have the meanings given for R11,
or in the presence of an aldehyde of the formula (VII)
wherein
R21 is a branched or unbranched C1- to C12-alkyl radical or C7- to C12-aralkyl radical or a C6- to C10-aryl radical, wherein the specified radicals can in each case have one or more identical or different substituents selected from the group consisting of OR10e, SR10f and NR8eR9e and halogen, wherein R10e, R10f, R8e and R9e, independently of one another, can have the meanings given for R11,
or in the presence of a ketone of the formula (VIII)
wherein
R22 and R23 are identical or different and are in each case a branched or unbranched C1- to C12-alkyl radical or C7- to C12-aralkyl radical or a C6- to C10-aryl radical or a C1- to C6-alkoxycarbonyl radical, wherein the specified radicals can in each case have one or more identical or different substituents selected from the group consisting of OR10e, SR10f, NR8eR9e and halogen, and wherein R22 and R23 can together also form a 5- to 8-membered ring which has one or more ethylenic double bonds and one or more identical or different hetero atoms selected from the group consisting of O, S and NR11b, and wherein R10e, R10f, R8e, R9e and R11b, independently of one another, can have the meanings given for R11,
or in the presence of a vinyl ether of the general formula (IX)
wherein
R24, R25, R26 and R27 are identical or different and, independently of one another, are in each case a branched or unbranched C1- to C12-alkyl radical or C7- to C12-aralkyl radical or a C6- to C10-aryl radical, wherein the specified radicals can in each case have one or more identical or different substituents selected from the group consisting of oxo, OR10e, SR10f, NR8eR9e and halogen and wherein R25 and R26 can together also form a 5- to 8-membered ring which can have one or more ethylenic double bonds and one or more identical or different hetero atoms selected from the group consisting of O, S and NR11b and wherein R10e, R10f, R8e, R9e and R11b, independently of one another, can have the meanings given for R11.

### Claim 18 (depends on 16)

The method according to claim 16, wherein the cyclization is carried out in the presence of acetaldehyde, propionaldehyde, chloral, 1,1,1-trifluoroacetone, 1,1,1-trifluoroacetophenone, methyl pyruvate, ethyl pyruvate or hexafluoroacetone.

### Claim 19 (depends on 16)

The method according to claim 16, wherein the carboxylic anhydride, the aldehyde, the ketone and/or the vinyl ether is used in an amount of from 0.01 mol % to 5 mol %, based on the amount of citronellal used.

### Claim 20 (depends on 16)

The method according to claim 16, wherein a solution or suspension of the catalyst is initially introduced and a mixture of the citronellal to be reacted with the carboxylic acid anhydride, the aldehyde, the ketone and/or the vinyl ether is added.

### Claim 21 (depends on 20)

The method according to claim 20, wherein the mixture of the citronellal to be reacted with the carboxylic acid anhydride, the aldehyde, the ketone and/or the vinyl ether is added within a period of from 30 minutes to 6 hours.

### Claim 22 (depends on 11)

The method according to claim 11, wherein the bis(diarylphenol) ligand of the formula (I) and the diarylphenoxy-aluminum compound used as catalyst used is recovered after the reaction has taken place.

### Claim 23 (depends on 7)

The method according to claim 7, comprising the steps
a) optionally distillative removal of the solvent used, and optionally the further compound used from the product mixture,
b) addition of a high-boiling solvent to the residue obtained in step a),
c) distillative separation of the isopulegol from the mixture obtained in step b) and
d) cooling of the distillation bottom obtained in step c) with crystallization of the bis(diarylphenol) ligand of the formula (I) used.

### Claim 24 (depends on 7)

A method of producing menthol comprising the production of isopulegol of the formula (IV) according to claim 7 and subsequent hydrogenation of the ethylenic double bond of the isopulegol obtained in this way.

### Claim 25 (depends on 7, 24)

The method according to claim 24 of producing optically active menthol comprising the steps
a) production of optically active isopulegol of the formula (IVa) according to claim 7 and
b) hydrogenation of the ethylenic double bond of the optically active isopulegol obtained in this way.