Synthesis of supported transition metal catalysts

0.42 g (2.20 mmol) of tertraethylene glycol, 0.25 g (0.22 mmol) of tetrakistriphenylphosphine palladium(0), 9.5 g (38.5 mmol) of aluminum tri-sec-butoxide and 3 mL (32.7 mmol) of butanol were mixed in a 25 mL reaction vessel and kept at 120° C. for 10 hours. Then, 1.80 mL of water was added thereto, the mixture was kept at the same temperature for 0.5 hours, and then cooled to room temperature. The precipitated solids were filtered, washed three times with 10 mL of acetone and dried for 24 hrs to obtain 2.75 g of a palladium catalyst supported on an alumina-based carrier (palladium particle average-size: 3 nm, palladium content: 0.85%, palladium yield: 98.0%).

An energy dispersive x-ray (EDX) scan of the supported palladium catalyst thus obtained is shown in FIG. 1A which confirms the presence of palladium particles. Lower and higher magnification transmission electron microscope (TEM) photographs thereof are shown in FIGS. 1B and 1C , respectively.

The results of N 2 -absorption BET analysis at 77K and CO-chemisorption at room temperature show that the supported palladium catalyst of Example 1 has a specific surface area of 611.5 m 2 /g catalyst, a palladium surface area of 216.53 m 2 /g catalyst and a palladium dispersion of 48%.

0.190 g (1.00 mmol) of tertraethylene glycol, 0.116 g (0.100 mmol) of tetrakistriphenylphosphine palladium(0) and 2.58 g (17.0 mmol) of tetramethyl orthosilicate were mixed in a 25 mL reaction vessel and kept at 120° C. for 2 hours. Then, 0.920 mL of water was added thereto, the mixture was kept at the same temperature for 10 hours, and then cooled to room temperature. The precipitated solids were filtered, washed tree times with 10 mL of acetone and dried for 24 hrs to obtain 1.29 g of a palladium catalyst supported on a silica-based carrier (palladium particle average-size: 5 nm, palladium content: 0.78%, palladium yield: 94.5%).

A TEM photograph of the supported palladium catalyst thus obtained is shown in FIG. 2 .

0.42 g (2.20 mmol) of tertraethylene glycol, 0.25 g (0.22 mmol) of tetrakistriphenylphosphine palladium(0) and 10.9 g (38.5 mmol) of titanium tetraisopropoxide were mixed in a 25 mL reaction vessel and kept at 120° C. for 2 hours. Then, 1.80 mL of water was added thereto, the mixture was kept at the same temperature for 10 hours, and then cooled to room temperature. The precipitated solids were filtered, washed three times with 10 mL of acetone and dried for 24 hrs to obtain 3.95 g of a palladium catalyst supported on a titania-based carrier palladium particle average-size: 5 nm n, palladium content: 0.59%, palladium yield: 97.4%).

A TEM photograph of the supported palladium catalyst thus obtained is shown in FIG. 3 .

<Performance of Various Organic Reactions Using Inventive Palladium Catalysts>

0.180 g (1.0 mmol) of trans-stilbene, a measured amount of the supported palladium catalyst prepared in Example 3 (the amount corresponding to 2 mol % of palladium based on the amount of trans-stilbene) and 4 mL of ethylacetate were mixed and stirred at room temperature for 60 min under 1 atm of H 2 . The resulting mixture was filtered and the solvent was removed. The resulting residue was subject to silica gel column chromatography (eluent: hexane/ethylacetate(10/1)) to obtain 0.182 g of the title compound, 1,2-diphenylethane (yield: 100%).

The supported palladium catalyst used in the above reaction was simply recovered by filtration, and it retained its original activity even after 15 recycles.

EXAMPLES 5 TO 14

The procedure of Example 4 was repeated employing the specifics shown in Table 1, to perform the hydrogenation of various alkynes or alkenes, whose respective yields are listed in Table 1.

0.122 g (1.0 mmol) of phenylethylalcohol, a measured amount of the supported palladium catalyst prepared in Example 1 (the amount corresponding to 0.5 mol % of palladium based on the amount of phenylethylalcohol) and 2 mL of toluene were mixed and refluxed for 6 hrs under 1 atmospheric air pressure. The resulting mixture was filtered and the solvent was removed. The resulting residue was subject to silica gel column chromatography (eluent: hexane/ethylacetate(5/1)) to obtain 0.120 g of the title compound, acetophenone (yield: 99%).

The supported palladium catalyst used in the above reaction was simply recovered by filtration, and it retained its original activity even after 15 recycles.

In contrast to the above, the procedure of Example 15 was repeated using commercially available 5% Pd/Al 2 O 3 in an amount which was equivalent to the amount of palladium used in the above reaction, to obtain acetophenone in a low yield of only 31%.

EXAMPLES 16 TO 26

The procedure of Example 15 was repeated employing the substrates shown in Table 2 in a mixed solvent of trifluorotoluene (TFT) and toluene, to perform oxidations of various alcohols or diols, i.e., the conversion of corresponding esters or aldehydes. The observed yields are listed in Table 2 (the values in parentheses belong to cases of employing toluene as the solvent).

The oxidation of cholesterol in accordance with the above scheme was conducted by a procedure similar to that used in Example 15 (yield: 99%).

0.262 g (1.0 mmol) of methyl 4-iodobenzoate, 0.424 g (2.0 mmol) of potassium phosphate, 0.461 g (2.2 mmol) of phenyl boronic acid, a measured amount of the supported palladium catalyst prepared in Example 3 (the amount corresponding to 0.75 mol % of palladium based on the amount of methyl 4-iodobenzoate) and 3 mL of toluene were mixed and stirred at 110° C. for 5 hrs under an argon atmosphere. The resulting mixture was filtered and the solvent was removed. The resulting residue was subject to silica gel column chromatography (eluent: hexane/ethylacetate(8/1)) to obtain 0.213 g of the title compound, methyl biphenyl-4-carboxylic ester (yield: 100%).

The supported palladium catalyst used in the above reaction was simply recovered by filtration, and it retained its original activity even after 3 recycles.

49.4 mmol of cyclohexene, and a measured amount of each of the supported palladium catalyst prepared in Examples 1 and 3, commercially available 5% Pd/C and 5% Pd/Al 2 O 3 (the amount corresponding to 0.83 mol % of palladium based on the amount of cyclohexene) were mixed and stirred at 40° C. for 24 hrs under 1 atm of H 2 . The resulting mixture was filtered and the solvent was removed. The resulting residue was subject to silica gel column chromatography (eluent: hexane/ethylacetate(8/1)) to obtain the title compound, cyclohexane.

The yields of cyclohexane thus obtained are listed in Table 3.

As described above, in accordance with the method of the present invention, a recyclable supported transition metal catalyst which has a high activity and keeps its original activity even after repeated use of more than 15 recycles can be easily synthesized in one pot. The inventive catalyst can be advantageously employed in the hydrogenation of alkenes and alkynes, the oxidation of alcohols, carbon-carbon coupling reactions and the like.

While the invention has been described with respect to the above specific embodiments, it should be recognized that various modifications and changes may be made to the invention by those skilled in the art which also fall within the scope of the invention as defined by the appended claims.