Preparing unsaturated carbocyclic compounds

Abstract

Disclosed are methods of preparing unsaturated carbocyclic compounds through dehydrogenation of corresponding saturated carbocyclic compounds.

Claims

1. A method of preparing an unsaturated compound of Formula (II), comprising dehydrogenation of a saturated compound of Formula (I) in the presence of a pincer-iridium catalyst under conditions that effect loss of one or more molecules of hydrogen (H.sub.2) per molecule of the saturated compound: ##STR00010## wherein R.sub.1 is H or CH.sub.3, n is 1, each --- represents a double bond, the number of the double bonds represented by --- in Formula (II) is 1 or 2, and said conditions comprise one or more solvents.

2. The method of claim 1, further comprising adding one or more hydrogen acceptors to the dehydrogenation reaction to consume the hydrogen molecules.

3. The method of claim 2, wherein the hydrogen acceptor is 3,3-dimethylbut-1-ene.

4. The method of claim 1, wherein said pincer-iridium catalyst is (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4), (iPr.sub.4PCP)Ir(C.sub.2H.sub.4), (iPr.sub.4POCOP)Ir(C.sub.2H.sub.4), or any combination thereof.

5. The method of claim 1, wherein R.sub.1 is H.

6. The method of claim 5, further comprising adding one or more hydrogen acceptors to the dehydrogenation reaction to consume the hydrogen molecules, wherein the hydrogen acceptor is 3,3-dimethylbut-1-ene, and the pincer-iridium catalyst is (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4).

7. The method of claim 1, wherein the one or more solvents are p-xylene, and the pincer-iridium catalyst is present at a level of 1% to 10% by mole of the compound of Formula (I).

8. The method of claim 1, wherein the number of the double bonds represented by --- is 1.

9. The method of claim 1, wherein the number of the double bonds represented by --- is 2.

10. The method of claim 1, wherein the conditions further comprise an elevated temperature, a stream of nitrogen to purge liberated hydrogen, or a combination thereof.

11. The method of claim 1, wherein the one or more solvents are xylene.

12. The method of claim 1, wherein the pincer-iridium catalyst is present at a level of 1% to 10% by mole of the compound of Formula (I).

13. A method of preparing an unsaturated compound of Formula (II), comprising dehydrogenation of a saturated compound of Formula (I) in the presence of a pincer-iridium catalyst under conditions that effect loss of one or more molecules of hydrogen (H.sub.2) per molecule of the saturated compound: ##STR00011## wherein R.sub.1 is H or CH.sub.3, n is 0 or 1, each --- represents a double bond, the number of the double bonds represented by --- in Formula (II) is 1 or 2, the pincer-iridium catalyst is present at a level of 1% to 10% by mole of the compound of Formula (I), and said conditions comprise one or more solvents.

14. The method of claim 13, further comprising adding one or more hydrogen acceptors to the dehydrogenation reaction to consume the hydrogen molecules.

15. The method of claim 14, wherein the hydrogen acceptor is 3,3-dimethylbut-1-ene.

16. The method of claim 13, wherein said pincer-iridium catalyst is (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4), (iPr.sub.4PCP)Ir(C.sub.2H.sub.4), (iPr.sub.4POCOP)Ir(C.sub.2H.sub.4), or any combination thereof.

17. The method of claim 13, wherein R.sub.1 is H and n is 1.

18. The method of claim 17, further comprising adding one or more hydrogen acceptors to the dehydrogenation reaction to consume the hydrogen molecules, wherein the hydrogen acceptor is 3,3-dimethylbut-1-ene, and the pincer-iridium catalyst is (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4).

19. The method of claim 13, wherein R.sub.1 is CH.sub.3 and n is 0.

20. The method of claim 19, further comprising adding one or more hydrogen acceptors to the dehydrogenation reaction to consume the hydrogen molecules, wherein the hydrogen acceptor is 3,3-dimethylbut-1-ene, and the pincer-iridium catalyst is (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4), (iPr.sub.4PCP)Ir(C.sub.2H.sub.4), (iPr.sub.4POCOP)Ir(C.sub.2H.sub.4), or any combination thereof.

21. The method of claim 13, wherein the one or more solvents are xylene.

22. The method of claim 13, wherein the number of the double bonds represented by --- is 1.

23. The method of claim 13, wherein the number of the double bonds represented by --- is 2.

24. The method of claim 13, wherein the conditions further comprise an elevated temperature, a stream of nitrogen to purge liberated hydrogen, or a combination thereof.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1(a) shows the GC-MS chromatogram of 1,1,4,4-tetramethyl-decalin, the starting material used in the reactions of Examples 1-4.

(2) FIG. 1(b) shows the GC-MS chromatogram of the reaction mixture of Example 1.

(3) FIG. 1(c) shows the NMR chromatogram of the reaction mixture of Example 1.

(4) FIG. 2(a) shows the GC-MS chromatogram of the reaction mixture of Example 2.

(5) FIG. 2(b) shows the NMR chromatogram of the reaction mixture of Example 2.

(6) FIG. 3 shows the GC-MS chromatogram of the reaction mixture of Example 3.

(7) FIG. 4 shows the NMR chromatogram of the reaction mixture of Example 3.

(8) FIG. 5(a) shows the GC-MS chromatogram of 1,1,2,3,3-pentamethylhexahydro-indane, the starting material used in the reactions of Examples 5 and 6.

(9) FIG. 5(b) shows the GC-MS chromatogram of the reaction mixture of Example 5.

(10) FIG. 5(c) shows the NMR chromatogram of the reaction mixture of Example 5.

(11) FIG. 6(a) shows the GC-MS chromatogram of the reaction mixture of Example 6.

(12) FIG. 6(b) shows the NMR chromatogram of the reaction mixture of Example 6.

(13) FIG. 7(a) shows the GC-MS chromatogram of 1,1,2,3,3-pentamethylhexahydro-indane, the starting material used in the reaction of Example 7.

(14) FIG. 7(b) shows the GC-MS chromatogram of the reaction mixture of Example 7.

(15) FIG. 7(c) shows the NMR chromatogram of the reaction mixture of Example 7.

DETAILED DESCRIPTION OF THE INVENTION

(16) In one aspect, the present invention provides a method of preparing an unsaturated compound, comprising dehydrogenation of a corresponding saturated compound in the presence of a pincer-iridium catalyst under conditions that effect loss of one or more molecules of hydrogen (H.sub.2) per molecule of the saturated compound.

(17) The saturated compounds are represented by Formula (I) below:

(18) ##STR00001##
In this formula, R.sup.1 is H or CH.sub.3 and n is 0 or 1.

(19) The structures of two representative compounds of Formula (I) are shown below:

(20) ##STR00002##

(21) The dehydrogenation of the compounds of Formula (I) forms the unsaturated compounds of Formula (II):

(22) ##STR00003##

(23) R.sup.1 and n are defined above. Each represents a double bond, and the number of the double bonds represented by is 1, 2 or 3.

(24) Representative products derived from Compound 1 include Compound 3 and analogs (e.g., Compounds 3a-c), Compound 4 and analogs (e.g., Compounds 4a-e), Compound 5, and any combination thereof:

(25) ##STR00004## ##STR00005##

(26) Representative products prepared from Compound 2 include Compound 6 and analogs, Compound 7 and analogs (e.g., Compounds 9-11), Compound 8, and any combination thereof:

(27) ##STR00006##

(28) A pincer-iridium catalyst is a catalyst having an iridium atom and a pincer ligand that binds tightly to three adjacent coplanar sites on iridium in a meridional configuration. It is used in the amount of 0.1 to 50% (e.g., 0.5 to 20%, 1 to 10%, and 2 to 8%) by mole of the compound of Formula (I).

(29) Exemplary pincer-iridium catalysts include (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4), (iPr.sub.4PCP)Ir(C.sub.2H.sub.4), (iPr.sub.4POCOP)Ir(C.sub.2H.sub.4), (tBu.sub.4POCOP)IrH.sub.n (n is 1, 2, 3, or 4, preferably n is 2 or 4.), (tBu.sub.4PCP)IrH.sub.n (n is 1, 2, 3, or 4, preferably n is 2 or 4.), and any combinations thereof.

(30) The pincer-iridium catalyst (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4) has the following structure:

(31) ##STR00007##
in which iPr represents isopropyl.

(32) In one embodiment, the conditions include one or more solvents (e.g., xylene, acetic acid, toluene, ethyl acetate, DMSO, and DMF), an elevated temperature (e.g., at least 50° C., at least 100° C., 50-800° C., 100-800° C., 100-400° C., and 150-350° C.), and/or a stream of nitrogen to purge liberated hydrogen. In another embodiment, the conditions include one or more hydrogen acceptor (e.g., tertiary butyl ethylene, 3,3-dimethylbut-1-ene, cyclohexene and other alkenes) to consume the liberated hydrogen.

(33) The duration of the dehydrogenation reaction varies from 30 minutes to 120 hours (e.g., 30 minutes to 60 hours, 1 to 30 hours, and 1 to 12 hours), depending on the solvent, reaction temperature, the starting material, the catalyst and its concentration, etc.

(34) The values and dimensions disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such value is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a value disclosed as “50%” is intended to mean “about 50%.”

(35) The invention is described in greater detail by the following non-limiting examples. Without further elaboration, it is believed that one skilled in the art can, based on the description herein, utilize the present invention to its fullest extent. All publications cited herein are incorporated by reference in their entirety.

EXAMPLES

(36) All the reagents used in the examples below were degassed and dried. The reagents include starting materials, catalysts, solvents, and hydrogen receptors.

Example 1: Selective Dehydrogenation of Compound 1 Using a Pincer-Iridium Catalyst

(37) ##STR00008## represents a double bond, and the number of double bond is 2

(38) In a J-Young tube were added in sequence the following agents: (i) a Pincer-iridium catalyst, i.e., 5.6 mg of (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4) (5% by mole of the saturated compound of Formula (I) as described below, 0.01 mmol at a concentration of 0.025 M in the resultant reaction mixture), (ii) a saturated compound of Formula (I), i.e., 38.8 mg of 1,1,4,4-tetramethyl-decalin (1 equivalent, 0.2 mmol, 0.5 M), and (iii) a hydrogen acceptor, i.e., 16.8 mg of tertiary butyl ethylene (“TBE”, 1 equivalent, 0.2 mol, 0.5 M), followed by the addition of a deuterated solvent, i.e., 0.4 mL of p-xylene-d.sub.10. The J-Young tube was sealed under argon and heated to 150° C. The reaction was monitored by GC-MS and .sup.1H NMR. See FIGS. 1(a)-(c). After 5 hours, 1,1,4,4-tetramethyl-decalin was reacted at a conversion of 70%. A compound of Formula (II), i.e., Compound 3, was obtained at a yield of 41%. Both the conversion and yield was calculated using the GC-MS and .sup.1H NMR data. The conversion was calculated as: the mass (by mole) of the saturated compound of Formula (I) consumed in the reaction/the mass (by mole) of the saturated compound added to the reaction×100%. The yield was calculated as: the actual yield (by mole) of the unsaturated compound of Formula (II)/the theoretical yield of the unsaturated compound of Formula (II)×100%.

Example 2

(39) In a J-Young tube were added 2.8 mg of Pincer-iridium catalyst (iPr.sub.4POCOP)Ir(C.sub.2H.sub.4) (1 mol %, 0.005 mmol, 0.01 M), 97 mg of 1,1,4,4-tetramethyl-decalin (1 eq., 0.5 mmol, 1 M), and 42 mg of TBE (1 eq., 0.5 mol, 1 M), followed by the addition of 0.4 mL of p-xylene-d.sub.10. The J-Young was sealed under argon and heated to 150° C. The reaction was monitored by GC-MS and .sup.1H NMR. After 13 hours, 1,1,2,3,3-pentamethylhexahydro-indane was reacted at a conversion of 56% and Compound 3 was obtained at a yield of 28% as observed by GC-MS and 1H NMR. See FIGS. 2(a) and 2(b).

Example 3

(40) The procedure in Example 2 was followed except that the reaction was carried out at 180° C., instead of 150° C. After heating for 4 hours, 1,1,2,3,3-pentamethylhexahydro-indane was reacted at a conversion of 44% and Compound 3 was obtained at a yield of 22% as observed by GC-MS and 1H NMR. See FIGS. 3 and 4.

Example 4

(41) In a 600 mL autoclave were added (i) 9.97 g of (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4) (5 mol %, 0.0178 mol, 0.032 M), (ii) 69 g of 1,1,4,4-tetramethyl-decalin (1 eq., 0.356 mol, 0.65 M), and (iii) 40.4 g of TBE (1.35 eq., 0.481 mol, 0.87 M), followed by the addition of 400 mL of p-xylene. The autoclave was sealed under argon and heated to 155° C. The reaction was monitored by GC-MS. After 6.5 hours, 1,1,2,3,3-pentamethylhexahydro-indane was reacted at a conversion of 95% and Compound 3 was obtained at a yield of 50% as observed by GC-MS.

Example 5: Selective Dehydrogenation of Compound 2 Using a Pincer-Iridium Catalyst

(42) ##STR00009## represents a double bond, the number of double bond is 1.

(43) In a J-Young tube were added (i) 2.8 mg of the Pincer-iridium catalyst (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4) (1 mol %, 0.005 mmol, 0.01 M), (ii) a compound of Formula (I), i.e., 97 mg of 1,1,2,3,3-pentamethylhexahydro-indane (1 eq., 0.5 mmol, 1 M), and (iii) 42 mg TBE (1 eq., 0.5 mol, 1 M), followed by 0.4 mL of p-xylene-d.sub.10. The J-Young was sealed under argon and heated to 150° C. The reaction was monitored by GC-MS and .sup.1H NMR. See FIGS. 5(a)-(c). After 1 hour, 1,1,2,3,3-pentamethylhexahydro-indane was reacted at a conversion of 34% and Compound 6 was obtained at a yield of 24% as observed by GC-MS and .sup.1H NMR. The aromatic product will increase quickly if continue heating.

Example 6

(44) The procedure described in Example 5 was followed except that (iPr.sub.4PCP)Ir(C.sub.2H.sub.4) was used, instead of (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4). After 2 hours, 1,1,2,3,3-pentamethylhexahydro-indane was reacted at a conversion of 33% and Compound 6 was obtained at a yield of 19% as observed by GC-MS and .sup.1H NMR. See FIGS. 6(a) and 6(b).

Example 7

(45) The procedure described in Example 5 was followed except that (iPr.sub.4POCOP)Ir(C.sub.2H.sub.4) was used, instead of (iPr.sub.4PCOP)Ir(C.sub.2H.sub.4). After 2 hours, 1,1,2,3,3-pentamethylhexahydro-indane was reacted at a conversion of 19% and Compound 7 and analogs were obtained at a yield of 14% as observed by GC-MS and .sup.1H NMR. See FIGS. 7(a) and 7(b).