Production of 2,2,4,4-tetramethylcyclobutane-1,3-diol from isobutanol using homogeneous catalysts

Abstract

A process for preparing 2,2,4,4-tetramethylcyclobutane-1,3-diol by reacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol in the presence of a tandem transfer hydrogenation and Tischenko reaction catalyst.

Description

Technical Field

[0001] This disclosure generally relates to a homogeneous catalytic method for preparing 2,2,4,4-tetramethylcyclobutane-1,3-diol by reacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol. Background Technology

[0002] Conventionally, 2,2,4,4-tetramethylcyclobutane-1,3-diol (TMCD) can be produced by hydrogenating 2,2,4,4-tetramethylcyclobutanedione (diketone) using a ruthenium-containing mixed metal heterogeneous catalyst.

[0003] In this conventional method, TMCD can be produced by (i) converting isobutyric acid to isobutyric anhydride, (ii) converting isobutyric anhydride to a diketone, and (iii) hydrogenating the diketone to TMCD.

[0004] Hydrogen is required in this conventional method. This method operates at relatively high hydrogen pressure and is subject to the generation of many byproducts, some of which are generated by acid-catalyzed ring-opening of cyclobutane during the hydrogenation process.

[0005] This disclosure presents a novel method for converting 2,2,4,4-tetramethylcyclobutanedione to 2,2,4,4-tetramethylcyclobutane-1,3-diol using isobutanol instead of hydrogen, while simultaneously producing isobutyl isobutyrate (IBIB). This novel method eliminates the use of hydrogen and removes safety concerns associated with its use. This new method is a highly efficient one-step process for producing TMCD and IBIB. The hydrogen transfer from isobutanol to the diketone replaces the H2-dependent reduction from the diketone to the diol, while isobutanol is converted to IBIB.

[0006] This disclosure addresses these unmet needs, as well as other needs, as will become apparent from the following description and the appended claims. Summary of the Invention

[0007] The method disclosed herein is as described in the appended claims.

[0008] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising: (1) a tandem transfer hydrogenation and Tischenko reaction catalyst. (1) In the presence of a catalyst, 2,2,4,4-tetramethylcyclobutanedione is contacted with isobutanol to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone; (2) Optionally, any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone are hydrogenated to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol; (3) Optionally, in the presence of an acid catalyst, isobutyl isobutyrate is hydrolyzed to produce isobutyric acid and isobutanol, and optionally, isobutanol is recycled to step (1); (4) Isobutyric acid is converted to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally, 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

[0009] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising: (1) contacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol in the presence of a tandem ruthenium transfer hydrogenation and Tischenko reaction catalyst to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone, said catalyst comprising H2Ru(PPh3)4, Ru3(CO) 12 One or more of (Ar4C4CO)Ru(CO)3 and (Ar4C4CO)2H(μ-H)(CO)4Ru2

[0010] The general formula for (Ar4C4CO)Ru(CO)3 is as follows:

[0011]

[0012] And Ar is represented by the following general formula:

[0013]

[0014] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0015] Furthermore, (Ar4C4CO)2H(μ-H)(CO)4Ru2 is represented by the following general formula:

[0016]

[0017] And Ar is represented by the following general formula:

[0018]

[0019] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0020] (2) Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol;

[0021] (3) Optionally, isobutyl isobutyrate is hydrolyzed in the presence of an acid catalyst to produce isobutyric acid and isobutanol, and optionally, isobutanol is recycled to step (1).

[0022] (4) Isobutyric acid is converted to 2,2,4,4-tetramethylcyclobutanedione, wherein the 2,2,4,4-tetramethylcyclobutanedione is optionally recycled to step (1).

[0023] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising: (1) contacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol in the presence of a tandem ruthenium transfer hydrogenation and Tischenko reaction catalyst to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone, said catalyst being selected from ((Ph4C4CO)2H(μ-H)(CO)4Ru2), (Ph4C4CO)2H(μ-H)(CO)4Ru2, [(4-ClC6H4)4C4CO]2H(μ-H)(CO)4Ru2, [2,5-(C6H5) ... (1) 2,3,4-(4-MeOC6H4)2C4CO]2H(μ-H)(CO)4Ru2 or [2,5-(C6H5)2-3,4-(4-FC6H4)2C4CO]2H(μ-H)(CO)4Ru2; (2) optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol; (3) optionally hydrolyze isobutyl isobutyrate in the presence of an acid catalyst to produce isobutyric acid and isobutanol, and optionally, wherein the isobutanol is optionally recycled to step (1); (4) convert isobutyric acid to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally the 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

[0024] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising:

[0025] (1) In the presence of a tandem transfer hydrogenation and Tischenko reaction catalyst, 2,2,4,4-tetramethylcyclobutanedione was contacted with isobutanol to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone.

[0026] (2) Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol;

[0027] (3) Optionally, isobutyl isobutyrate is hydrolyzed in the presence of an acid catalyst to produce isobutyric acid and isobutanol, wherein the isobutanol is optionally recycled to step (1).

[0028] (4) Isobutyric acid is converted to 2,2,4,4-tetramethylcyclobutanedione, wherein the 2,2,4,4-tetramethylcyclobutanedione is optionally recycled to step (1).

[0029] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising:

[0030] 1. 2,2,4,4-Tetramethylcyclobutanedione is contacted with isobutanol in the presence of a tandem ruthenium transfer hydrogenation and Tischenko reaction catalyst to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone, wherein the catalyst comprises H₂Ru(PPh₃)₄ and Ru₃(CO). 12 One or more of (Ar4C4CO)Ru(CO)3 and (Ar4C4CO)2H(μ-H)(CO)4Ru2

[0031] The general formula for (Ar4C4CO)Ru(CO)3 is as follows:

[0032]

[0033] And Ar is represented by the following general formula:

[0034]

[0035] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0036] Furthermore, (Ar4C4CO)2H(μ-H)(CO)4Ru2 is represented by the following general formula:

[0037]

[0038] And Ar is represented by the following general formula:

[0039]

[0040] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0041] 2. Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol;

[0042] 3. Optionally, isobutyl isobutyrate is hydrolyzed in the presence of an acid catalyst to produce isobutyric acid and isobutanol, and optionally, isobutanol is recycled to step (1).

[0043] 4. Convert isobutyric acid to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally the 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

[0044] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising:

[0045] 1. In the presence of a tandem ruthenium transfer hydrogenation and Tischenko reaction catalyst, 2,2,4,4-tetramethylcyclobutanedione is contacted with isobutanol to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone, wherein the catalyst is selected from (Ph4C4CO)2H(μ-H)(CO)4Ru2, [(4-ClC6H4)4C4CO]2H(μ-H)(CO)4Ru2, [2,5-(C6H5)2-3,4-(4-MeOC6H4)2C4CO]2H(μ-H)(CO)4Ru2 or [2,5-(C6H5)2-3,4-(4-FC6H4)2C4CO]2H(μ-H)(CO)4Ru2;

[0046] 2. Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol;

[0047] 3. Optionally, isobutyl isobutyrate is hydrolyzed in the presence of an acid catalyst to produce isobutyric acid and isobutanol, wherein the isobutanol is optionally recycled to step (1);

[0048] 4. Convert isobutyric acid to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally the 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

[0049] In one embodiment of this disclosure, the catalyst for the tandem ruthenium transfer hydrogenation and Tischenko reaction is ((Ph4C4CO)2H(μ-H)(CO)4Ru2).

[0050] In one embodiment of this disclosure, the conversion of 2,2,4,4-tetramethylcyclobutanedione is at least 50%, at least 70%, or at least 90%.

[0051] In one embodiment of this disclosure, the selectivity of 2,2,4,4-tetramethylcyclobutane-1,3-diol is at least 30%, or at least 60%. Attached Figure Description

[0052] Figure 1 This is the GC / MS chromatogram of the reaction product. A 4:1 molar ratio of iBuOH to diketone was used. (1-Hydroxy-2,2,4-trimethylpentane-3-one (TMOP), 3-hydroxy-2,2,4,4-tetramethylcyclobutyl isobutyrate (Mester1 / 2). See Example 1 in the Experimental section.

[0053] Figure 2 It is a study of reaction kinetics. Detailed Implementation

[0054] In this disclosure, it has been found that TMCD can be formed from diketone and isobutanol in a single method step. The method for converting isobutanol to TMCD of this disclosure also converts isobutyric acid to isobutyric anhydride (IBAN) and IBAN to diketone.

[0055] This method enables the one-step production of TMCD and isobutyl isobutyrate (IBIB). Hydrogen transfer from isobutanol to a diketone replaces the H2-dependent reduction from a diketone to a diol, while isobutanol is oxidized to the carboxylic acid level required for its conversion to dimethyl ketene. The mild dehydrogenation coupling of isobutanol to IBIB, followed by acid-catalyzed hydrolysis to isobutyric acid, provides a higher isobutyric acid yield compared to the air oxidation of isobutyraldehyde, which is subject to the co-production of isopropyl formate (and associated isopropanol and formic acid).

[0056] This disclosure relates to a single process step in which 2,2,4,4-tetramethylcyclobutane-1,3-diol (TMCD) is formed from 2,2,4,4-tetramethylcyclobutanedione (diketone) and isobutanol. The diketone and isobutanol are oxidized to their acid oxidation states in substantially quantitative yields under mild conditions. In the process of this disclosure, due to the need for acid-catalyzed hydrolysis of IBIB and the acid sensitivity of the TMCD product, IBIB is hydrolyzed in a separate step.

[0057] In one embodiment, this disclosure provides a method for preparing 2,2,4,4-tetramethylcyclobutane-1,3-diol. The method comprises contacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol in the presence of a tandem transfer hydrogenation and a Tischenko reaction catalyst.

[0058] One embodiment of this disclosure is a method for producing TMCD using isobutanol as a raw material. In some embodiments, bio-isobutanol can be used as the isobutanol source in this disclosure to produce bio-TMCD. If isobutanol with a partial biomass content is used, bio-TMCD with a corresponding partial biomass content is produced. Similarly, if bio-isobutanol with a biomass content of 25-100% is used in the four-step method shown below, intermediates such as bio-IBIB, bio-isobutyric acid, and bio-IBAN can also be produced. In applications where bio-TMCD with a biomass content of 25-100% is introduced into copolyesters, novel polyesters with appropriate biomass content can be produced. The composition of 25-100% bio-TMCD is expected through this method, such as the corresponding bio-IBIB derived from the first step, the bio-isobutyric acid from the second step, and the bio-IBAN from the third step. In one embodiment of this disclosure, the isobutanol comprises at least 25% bio-isobutanol. In one embodiment of this disclosure, the isobutanol comprises at least 50% bio-isobutanol. In one embodiment of this disclosure, isobutanol comprises at least 75% bio-isobutanol. In another embodiment of this disclosure, isobutanol comprises 100% bio-isobutanol.

[0059] In one embodiment of this disclosure, the method requires the following steps:

[0060] (i) Using isobutanol as a hydrogen donor, hydrogenated tetramethylcyclobutanedione is transferred, simultaneously generating IBIB.

[0061] (ii) IBIB hydrolysis produces isobutyric acid and isobutanol (in some embodiments, the generated isobutanol is recycled to step (i)).

[0062] (iii) Using isobutyric acid (in some embodiments, isobutyric acid is generated in step (ii)) to generate isobutyric anhydride, and

[0063] (iv) Dimethyl ketone was produced by converting isobutyric anhydride.

[0064] In one embodiment of this disclosure, the method is as follows:

[0065]

[0066] In one embodiment, the method for converting isobutanol to TMCD of this disclosure requires the conversion of isobutyric acid to IBAN and the conversion of IBAN to a diketone. Hydrogen transfer from isobutanol to a diketone replaces the H2-dependent reduction of the diketone to a diol, while isobutanol is oxidized to the carboxylic acid level required for its conversion to dimethyl ketene. The efficient mild dehydrogenation coupling of isobutanol to IBIB provides a higher yield of isobutyric acid and is not subject to the co-production of isopropyl formate (or related isopropanol).

[0067] In one embodiment, the method of this disclosure includes contacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol in the presence of a tandem transfer hydrogenation and Tischenko reaction catalyst to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone.

[0068] Therefore, this disclosure provides a method for preparing 2,2,4,4-tetramethylcyclobutane-1,3-diol by reacting 2,2,4,4-tetramethylcyclobutanedione with isobutanol in the presence of a tandem transfer hydrogenation and a Tischenko reaction catalyst.

[0069] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising:

[0070] 1) In the presence of a tandem ruthenium transfer hydrogenation and Tischenko reaction catalyst, 2,2,4,4-tetramethylcyclobutanedione is contacted with isobutanol to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone, wherein the catalyst comprises H2Ru(PPh3)4 and Ru3(CO). 12 One or more of (Ar4C4CO)Ru(CO)3 and (Ar4C4CO)2H(μ-H)(CO)4Ru2

[0071] The general formula for (Ar4C4CO)Ru(CO)3 is as follows:

[0072]

[0073] And Ar is represented by the following general formula:

[0074]

[0075] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0076] Furthermore, (Ar4C4CO)2H(μ-H)(CO)4Ru2 is represented by the following general formula:

[0077]

[0078] And Ar is represented by the following general formula:

[0079]

[0080] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0081] 2) Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol;

[0082] 3) Optionally, in the presence of an acid catalyst, isobutyl isobutyrate is hydrolyzed to produce isobutyric acid and isobutanol, and optionally, wherein the isobutanol is recycled to step 1);

[0083] 4) Convert isobutyric acid to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally the 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

[0084] One embodiment of this disclosure is a method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising:

[0085] 1) In the presence of a tandem ruthenium transfer hydrogenation and Tischenko reaction catalyst, 2,2,4,4-tetramethylcyclobutanedione is contacted with isobutanol to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone, wherein the catalyst is selected from (Ph4C4CO)2H(μ-H)(CO)4Ru2, [(4-ClC6H4)4C4CO]2H(μ-H)(CO)4Ru2, [2,5-(C6H5)2-3,4-(4-MeOC6H4)2C4CO]2H(μ-H)(CO)4Ru2 or [2,5-(C6H4)2-3,4-(4-FC6H4)2C4CO]2H(μH)(CO)4Ru2;

[0086] 2) Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol;

[0087] 3) Optionally, in the presence of an acid catalyst, isobutyl isobutyrate is hydrolyzed to produce isobutyric acid and isobutanol, wherein the isobutanol is optionally recycled to step 1);

[0088] 4) Convert isobutyric acid to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally the 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

[0089] In one embodiment, the method of the present invention includes contacting a diketone with an alcohol at a molar ratio of alcohol to diketone greater than 1:1 and at most 50:1, under conditions that effectively produce a diol, in the presence of a tandem transfer hydrogenation and Tischenko reaction catalyst.

[0090] In one embodiment, the method of this disclosure is carried out at a molar ratio of isobutanol to 2,2,4,4-tetramethylcyclobutanedione greater than 1:1 and at most 50:1.

[0091] In one embodiment, an excess of alcohol or isobutanol is used to maximize selectivity and minimize the formation of byproducts. In some embodiments, the molar ratio of isobutanol to 2,2,4,4-tetramethylcyclobutanedione includes 1:1 to 50:1, 2:1 to 25:1, 3:1 to 25:1, 4:1 to 25:1, 8:1 to 25:1, 12:1 to 25:1, 16:1 to 25:1, 2:1 to 24:1, 3:1 to 24:1, 4:1 to 24:1, 8: 1 to 24:1, 12:1 to 24:1, 16:1 to 24:1, 2:1 to 20:1, 3:1 to 20:1, 4:1 to 20:1, 8:1 to 20:1, 12:1 to 20:1, 16:1 to 20:1, 2:1 to 16:1, 3:1 to 16:1, 4:1 to 16:1, 8:1 to 16:1 and 12:1 to 16:1.

[0092] In one embodiment, the catalyst for the tandem ruthenium transfer hydrogenation and Tischenko reaction is (Ph4C4CO)2H(μ-H)(CO)4Ru2. It is known in the literature as a Shvo catalyst, sometimes written as [Ru2(CO)4(μ-H)(C4Ph4COHOCC4Ph4)]. The Shvo catalyst is a ruthenium dicyclopentadienone ligand having structure 1.

[0093]

[0094] "RuCC" refers to a complex containing one or more ruthenium atoms and one or more ligands linked by direct metal-ligand bonding. There are no particular limitations on the form or oxidation state of the ruthenium atoms, or the type and number of groups acting as ligands. Examples of such ligands include carbon monoxide, phosphine, hydrides, and substituted cyclopentadienones. Substituted cyclopentadienones are preferred ligands.

[0095] In one implementation, suitable examples of RuCC include H2Ru(PPh3)4 and Ru3(CO).12 , (Ar4C4CO)Ru(CO)3 and (Ar4C4CO)2H(μ-H)(CO)4Ru2, (Ph4C4CO)Ru(CO)3, [(4-ClC6H4)4C4CO]Ru(C O)3, [2,5-(C6H4)2-3,4-(4-MeOC6H4)2C4CO]Ru(CO)3, [2,5-(C6H4)2-3,4-(4-FC6H4)2C4CO]Ru( CO)3, (Ph4C4CO)2H(μ-H)(CO)4Ru2, [(4-ClC6H4)4C4CO]2H(μ-H)(CO)4Ru2, [2,5-(C6H5)2-3,4-(4-MeOC6H4)2C4CO]2H(μ-H)(CO)4Ru2, and [2,5-(C6H5)2-3,4-(4-FC6H4)2C4CO]2H(μ-H)(CO)4Ru2. These compounds can be synthesized using well-known methods (e.g., N. Menashe et al., Organometallics, Vol. 10, p. 3885 (1991)).

[0096] In one implementation, (Ar4C4CO)Ru(CO)3 is represented by the following general formula:

[0097]

[0098] And Ar is represented by the following general formula:

[0099]

[0100] And the groups R are the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0101] In one embodiment, (Ar4C4CO)2H(μ-H)(CO)4Ru2 is represented by the following general formula:

[0102]

[0103] And Ar is represented by the following general formula:

[0104]

[0105] And the groups R may be the same or different, selected from H, methyl, ethyl, or straight-chain or branched alkyl containing 3 to 10 carbon atoms, substituted or unsubstituted aryl, carbonyl groups such as aldehydes, ketones or esters having 2 to 10 carbon atoms, trifluoromethyl or fluorinated hydrocarbon groups such as perfluorobutyl or pentafluorophenyl.

[0106] In one embodiment, the amount of catalyst used may be 10 relative to the diketone. -7 : 1 to 1:1 (molar ratio). In one embodiment, the amount of catalyst used relative to the diketone can be 10- 3 The molar ratio is 1 to 0.01:1. In one embodiment, the catalyst concentration is from about 0.001 mol% to 10 mol% based on the concentration of 2,2,4,4-tetramethylcyclobutanedione. In one embodiment, the catalyst concentration is from about 0.001 mol% to about 9 mol%, or from about 0.001 mol% to about 5 mol%, or from about 0.001 mol% to about 1 mol%, or from about 0.01 mol% to about 10 mol%, or from about 0.01 mol% to about 5 mol%, or from about 0.01 mol% to about 1 mol%, or from about 0.1 mol% to about 5 mol%, or from about 0.1 mol% to about 1 mol%.

[0107] After the reaction, the catalyst can be separated from the product by distillation, extraction, adsorption or other conventional methods and then reused.

[0108] The method disclosed herein can be carried out without a solvent. However, if RuCC has low solubility in a reaction medium containing diketones and alcohols, the reaction can be carried out in a suitable solvent to dissolve the RuCC, or otherwise, as required. Examples of suitable solvents include hydrocarbons, such as hexane, benzene, and toluene; ethers, such as diethyl ether, dimethoxyethane, tetrahydrofuran, and dioxane; and esters, such as ethyl acetate, butyl acetate, and 2-ethylhexyl acetate.

[0109] Typically, the reaction is carried out by introducing a diketone, isobutanol, and a catalyst into a vessel, followed by mixing the contents. In one embodiment, the reaction is carried out by introducing 2,2,4,4-tetramethylcyclobutanedione, isobutanol, and a tandem transfer hydrogenation and Tischenko reaction catalyst into a vessel, followed by mixing the contents. In one embodiment, the reaction temperature can be 50 to 300°C, or 50 to 200°C, or 60 to 200°C, or 70 to 200°C, or 80 to 200°C, or 90 to 200°C, or 100 to 200°C, or 150 to 200°C, or 50 to 150°C, or 100 to 150°C, or 50 to 100°C. In one embodiment, the method temperature range is from about 50°C to about 300°C. In another embodiment, the method temperature range is from about 50°C to about 200°C.

[0110] The reaction pressure and atmosphere are not particularly limited. The reaction can be carried out below atmospheric pressure, at atmospheric pressure, or under high pressure. In one embodiment, the reaction is carried out in an inert atmosphere such as nitrogen or argon. In one embodiment, the reaction is carried out under nitrogen pressure to keep the alcohol liquid. In one embodiment, the reaction is carried out under nitrogen pressure of at least 200 psig.

[0111] In one embodiment, the reaction time depends on the reaction temperature and catalyst concentration, and the reaction time can be, for example, 0.1 to 10 hours, or 0.5 to 3 hours, or 5 minutes to 5 hours, or 5 minutes to 4 hours, or 5 minutes to 3 hours, or 5 minutes to 2 hours, or 5 minutes to 1 hour, or 5 minutes to 30 minutes, or 30 minutes to 5 hours, or 30 minutes to 4 hours, or 30 minutes to 2 hours, or 30 minutes to 1 hour.

[0112] In one embodiment, the method of this disclosure is carried out in the presence of a tandem transfer hydrogenation and a Tischenko reaction catalyst, under conditions that efficiently produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutane-1,3-diol, at a molar ratio of isobutanol to diketone greater than 1:1 and at most 50:1. In one embodiment, the concentration of isobutanol to 2,2,4,4-tetramethylcyclobutane-1,3-diol is from 1:1 to 50:1. In one embodiment, the concentration of isobutanol to 2,2,4,4-tetramethylcyclobutane-1,3-diol is from 1:1 to 40:1. In one embodiment, the concentration of isobutanol to 2,2,4,4-tetramethylcyclobutane-1,3-diol is from 1:1 to 30:1.

[0113] In one embodiment, the concentrations of isobutanol and 2,2,4,4-tetramethylcyclobutanedione are in a molar ratio of 1:1 to 20:1.

[0114] In one embodiment, the molar ratio of isobutanol to 2,2,4,4-tetramethylcyclobutanedione is from 1:1 to 10:1. In another embodiment, the molar ratio of isobutanol to 2,2,4,4-tetramethylcyclobutanedione is from 1:1 to 5:1. In yet another embodiment, the molar ratio of isobutanol to 2,2,4,4-tetramethylcyclobutanedione is from 1:1 to 2.5:1.

[0115] In one embodiment, the method of this disclosure is capable of converting 2,2,4,4-tetramethylcyclobutanedione with a conversion rate of at least 50%; or at least 55%, or at least 60%, or at least 65%, or at least 70%, or at least 75%, or at least 80%, or at least 85%, or at least 90%, or at least 95%. In one embodiment, the conversion rate of 2,2,4,4-tetramethylcyclobutanedione is at least 70%. In one embodiment, the conversion rate of 2,2,4,4-tetramethylcyclobutanedione is at least 80%. In one embodiment, the conversion rate of 2,2,4,4-tetramethylcyclobutanedione is at least 90%.

[0116] In some implementations, the conversion rate is determined by the following equation:

[0117]

[0118] In some embodiments, the method of this disclosure may have a selectivity of at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95% for 2,2,4,4-tetramethylcyclobutane-1,3-diol. In one embodiment, the selectivity for 2,2,4,4-tetramethylcyclobutane-1,3-diol is at least 30%. In one embodiment, the selectivity for 2,2,4,4-tetramethylcyclobutane-1,3-diol is at least 50%. In one embodiment, the selectivity for 2,2,4,4-tetramethylcyclobutane-1,3-diol is at least 60%.

[0119] This disclosure includes and expressly contemplates any and all combinations of the embodiments, features, characteristics, parameters, and / or scopes disclosed herein. In other words, this disclosure may be defined by any combination of the embodiments, features, characteristics, parameters, and / or scopes mentioned herein.

[0120] As used in this text, the indefinite articles “one” and “a / a kind” refer to one or more / a variety of things, unless the context clearly indicates otherwise. Similarly, the singular form of a noun includes its plural form, and vice versa, unless the context clearly indicates otherwise.

[0121] As used herein, the term “and / or” when used in a list of two or more items means that any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B and / or C, the composition may contain A alone; B alone; C alone; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B and C.

[0122] Although attempts have been made to be precise, the numerical values ​​and ranges described herein should be considered approximate (even when not limited by the term "about"). These values ​​and ranges may differ from their specified values ​​depending on the desired properties sought to be obtained by this disclosure and the variations arising from standard deviations present in the measurement techniques. Furthermore, the ranges described herein are intended and specifically anticipated to include all subranges and values ​​within the said ranges. For example, a range of 50 to 100 is intended to describe and include all values ​​within that range, including subranges such as 60 to 90 and 70 to 80.

[0123] All references cited herein, including both patent and non-patent literature, are incorporated herein in their entirety for reference. Where any incorporated subject matter contradicts any disclosure herein, the disclosure herein shall prevail over the incorporated content.

[0124] This disclosure may be further illustrated by the following embodiments of its preferred implementation, but it should be understood that these embodiments are included for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0125] Example

[0126] The tandem TH-Tishchenko reaction of i-BuOH and a diketone was carried out using Shvo catalyst 1. The experiment was conducted at 150 °C for 3 h using 0.1 mol% catalyst (relative to the diketone). After 3 h of reaction, the reaction products were analyzed using gas chromatography-mass spectrometry (GC-MS). Chromatogram ( Figure 1 The reaction proceeds directly to produce IBIB and a mixture of ketols and TMCD products (eq 1).

[0127]

[0128] Kinetic studies were conducted at 150 °C using iBuOH and diketone feed in a 4:1 molar ratio and 0.1 mol% Shvo catalyst. The reaction reached equilibrium in approximately 2 hours. Figure 2 Most of the diketones were consumed in less than 2 hours. The combined selectivity for keto-alcohol and TMCD products remained very high during the reaction (Table 1). Furthermore, the selectivity for IBIB remained above 96%.

[0129] Table 1. Tandem TH-Tishchenko reaction of isobutanol and diketone. a

[0130]

[0131] aA 4:1 molar ratio of iBuOH to diketone was used as the feed. The catalyst loading was 0.1 mol% shvo. Experiments were conducted at 150 °C. A 12-minute heating period was allowed before sampling at t=0 minutes. b Selectivity was calculated by dividing the number of moles of product in the liquid phase by the number of moles of reactants charged. The cis / trans ratio of TMCD remained at approximately 1.3 during the reaction (see Example 2 in the Experimental section).

[0132] Experimental Section

[0133] Materials: iBuOH and toluene were purchased from Aldrich. Shvo catalyst was obtained from Strem.

[0134] Gas chromatography. The method sample was analyzed using an Agilent 6890 gas chromatograph equipped with a split / heated injector (250°C) and a thermocouple detector (250°C). A capillary column (30 m × 0.32 mm ID) coated with a .25 μm film thickness of (50% methyl, 50% phenylsiloxane) was used (e.g., DB-Wax or equivalent). Helium was used as the carrier gas, with an initial column top pressure of 7.42 psi and an initial column flow rate of 1.56 mL / min, while maintaining a carrier gas linear velocity of 45 cm / s throughout the oven temperature program. The column temperature was programmed as follows: an initial oven temperature of 40°C was set and held for 3 minutes, followed by ramping the oven to 200°C at 8°C / min and holding at 200°C for 2 minutes (total run time 25 minutes). 0.5 μL of the prepared sample solution was injected at a split ratio of 75:1. EZ-Chrom Elite chromatographic data system software was used for data acquisition and data processing. Sample preparation was performed by weighing 0.1 g (accurate to 0.1 mg) of sample into a GC sample vial and adding 1.0 mL of ISTD solution (1% by volume diethylene glycol dimethyl ether in acetonitrile) into the GC sample vial.

[0135] The GC components of this method are shown below.

[0136]

[0137] The chemical structure of GC components was analyzed using this method.

[0138] Example 1. 20.0 g (269.2 mmol) iBuOH, 10.7 g (76.3 mmol) diketone, and 0.09 g (0.077 mmol) Shvo catalyst were charged into a 100 mL titanium autoclave. The autoclave was pressurized with approximately 100 psig of N2, and then vented twice. The autoclave was then pressurized again with 200 psig of N2, heated to 150 °C, and maintained at the reaction temperature for 3 hours. It was then cooled to room temperature and the pressure was reduced. The liquid product was analyzed by GC / MS. Figure 1 ).

[0139] Example 2. 20.0 g (269.2 mmol) iBuOH, 10.7 g (76.3 mmol) diketone, and 0.09 g (0.077 mmol) Shvo catalyst were charged into a 100 mL titanium autoclave. The autoclave was pressurized with approximately 100 psig of N2, and then vented twice. The autoclave was then pressurized again with 200 psig of N2, heated to 150 °C, and maintained at the reaction temperature for 3 hours. Samples were taken and their masses recorded at t = 0. Samples were also taken at t = 15, 30, 60, 90, 120, and 180 minutes. After 3 hours, the autoclave was cooled to room temperature and the pressure was reduced. The samples were analyzed by gas chromatography. Figure 2 Conversion rates and selectivity are shown in Table 1.

[0140] This disclosure has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications may be made within the spirit and scope of the invention.

Claims

1. A method for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising: (1) In the presence of tandem ruthenium transfer hydrogenation and Tischenko reaction catalysts, 2,2,4,4-tetramethylcyclobutanedione was contacted with isobutanol to produce isobutyl isobutyrate and 2,2,4,4-tetramethylcyclobutane-1,3-diol and 3-hydroxy-2,2,4,4-tetramethylcyclobutanone. The catalyst for the tandem ruthenium transfer hydrogenation and Tischenko reaction is (Ar4C4CO)2H(μ-H)(CO)4Ru2, represented by the following general formula. And Ar is represented by the following general formula: And the groups R may be the same or different, and are selected from H, methyl, ethyl, or straight-chain or branched alkyl groups containing 3 to 10 carbon atoms; (2) Optionally hydrogenate any unreacted 2,2,4,4-tetramethylcyclobutanedione and 3-hydroxy-2,2,4,4-tetramethylcyclobutane to produce 2,2,4,4-tetramethylcyclobutane-1,3-diol. (3) Optionally, isobutyl isobutyrate is hydrolyzed in the presence of an acid catalyst to produce isobutyric acid and isobutanol, and optionally, isobutanol is recycled to step (1). (4) Convert isobutyric acid to 2,2,4,4-tetramethylcyclobutanedione, wherein optionally the 2,2,4,4-tetramethylcyclobutanedione is recycled to step (1).

2. The method according to claim 1, wherein the transfer hydrogenation catalyst is a ruthenium complex having structure 1 as a ligand of cyclopentadienone:

3. The method according to claim 1, wherein the conversion rate of 2,2,4,4-tetramethylcyclobutanedione is at least 50%.

4. The method according to claim 1, wherein the conversion rate of 2,2,4,4-tetramethylcyclobutanedione is at least 70%.

5. The method according to claim 1, wherein the conversion rate of 2,2,4,4-tetramethylcyclobutanedione is at least 90%.

6. The method according to claim 1, wherein the selectivity of 2,2,4,4-tetramethylcyclobutane-1,3-diol is at least 30%.

7. The method of claim 1, wherein the selectivity of 2,2,4,4-tetramethylcyclobutane-1,3-diol is at least 60%.

8. The method according to claim 1, wherein the method temperature range is 50°C to 300°C.

9. The method according to claim 1, wherein the method temperature range is 50°C to 200°C.

10. The method of claim 1, wherein the method is carried out at a nitrogen pressure of at least 200 psig.

11. The method according to claim 1, wherein the method time is from 5 minutes to 5 hours.

12. The method of claim 1, wherein the catalyst concentration is from 0.001 mol% to 10 mol% based on the concentration of 2,2,4,4-tetramethylcyclobutanedione.

13. The method according to claim 1, wherein the concentrations of isobutanol and 2,2,4,4-tetramethylcyclobutanedione are in a molar ratio of 1:1 to 50:

1.

14. The method according to claim 1, wherein the concentrations of isobutanol and 2,2,4,4-tetramethylcyclobutanedione are in a molar ratio of 1:1 to 20:

1.

15. The method according to claim 1, wherein the concentrations of isobutanol and 2,2,4,4-tetramethylcyclobutanedione are in a molar ratio of 1:1 to 10:

1.

16. The method according to claim 1, wherein the concentrations of isobutanol and 2,2,4,4-tetramethylcyclobutanedione are in a molar ratio of 1:1 to 5:1.

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