METHOD FOR REDUCTION OF ORGANIC MOLECULES

Abstract

A method for the reduction organic molecules comprising a Ruthenium-Triphosphine complex with aromatic ligands at the phosphors which are ortho or meta substituted.

Claims

1. A method for the reduction of organic molecules, comprising the step of a) hydrogenating at least one organic molecule in the presence of a Ruthenium-Triphosphine-complex whereby the triphosphine-complex comprises at least one aryl and/or heteroaryl moeity bound to a phosphine which is substituted in ortho and/or meta position to the phosphine.

2. The method according to claim 1, wherein the Ruthenium-Triphosphine-complex comprises a phosphororganic compound where two or all three phosphors have an aryl and/or heteroaryl moeity which is substituted in ortho and/or meta position to the phosphine bound thereto.

3. The method according to claim 1, wherein the Ruthenium-Triphosphine-complex comprises a phosphororganic compound of the following structure ##STR00007## whereby R.sup.1 to R.sup.6 are independent from each other substituted or unsubstituted aryl or heteroaryl, provided that one of R.sup.1 and R.sup.2, R.sup.3 and R.sup.4, R.sup.5 and R.sup.6 is substituted in ortho and/or meta position to the phosphine, and R.sup.7 is hydrogen or an organic moeity

4. The method according to claim 1, wherein step a) is performed under acidic conditions.

5. The method according to claim 1, wherein step a) is performed under acidic conditions whereby the (initial) concentration of acid is ≧0.5 to ≦20 times the concentration of Ruthenium (in mol:mol).

6. The method according to claim 5, wherein step a) is performed under acidic conditions whereby the acid is selected out of the group comprising sulfonic acids, especially methanesulfonic acid, trifluormethansulfonic acid, p-toluolsulfonic acid, p-bromobenzosulfonic acid, p-nitrobenzosulfonic acid, sulfuric acid, hydrochloric acid, hydrofluoric acid, trifluoracetic acid, perchloric acid, bis(trifluoromethane)sulfonimide or mixtures thereof

7. The method according to claim, wherein step a) is carried out at an initial hydrogen pressure of ≧1 bar.

8. The method according to claim 1, wherein step a) is carried out in a dipolar protic or aprotic solvent or in CO.sub.2

Description

EXAMPLES

[0046] In the following, the following catalyst systems are used, being referred to as 1b, 2b (both comparative) and 3b (inventive):

[0047] These are made according to the following synthesis scheme:

[0048] a) Synthesis of the triphosphine compound:

TABLE-US-00001 [00003] Ligand R 1a Phenyl 2a 4-Methylphenyl 3a 3,5-dimethylphenyl

[0049] b) Synthesis of the Ruthenium-complex

TABLE-US-00002 [00004] [00005] Catalyst R 1b Phenyl 2b 4-Methylphenyl 3b 3,5-dimethylphenyl

[0050] These complexes were then used for the hydrogenation of Dimethyl itaconate. This model compound was selected since it comprises an alkene and two ester moieties. Full hydrogenated reaction products are either 2-Methyl-1-4-Butanediol (BDO) or the cyclic form 3-Methyotetrahydrofuran (3-MTHF).

##STR00006##

[0051] In case the hydrogenation is not complete, also Dimethyl methylsuccinate (MBS DME) and/or 2/3-Methyl-γ-Butyrolactone (MGBL) may be found as reaction products.

General Procedure for Hydrogenation Experiments

[0052] For the hydrogenation experiments the following general procedure, here exemplified with Ruthenium(Triphos-Xyl)TMM (1b) was used except where noted

[0053] A 20 mL stainless steel autoclave with a glass inlet was charged with Dimethyl itaconate (3.7258 g, 23.6 mmol), Ruthenium(Triphos-Xyl)TMM (1b) (0.0095 g, 0.01 mmol) and HBTA=Bis(trifluormethylsulfon)imid (0.0028 g, 0.01 mmol). It should be noted that the ratio of catalyst/HBTA is always set 1:1 (mol/mol), also when different concentration of catalyst were used.

[0054] The autoclave was sealed, evacuated at high vacuum and refilled with argon at least 3 times and subsequently pressurized with 100 bar H.sub.2 and placed into a steel cone preheated to 200° C. on a magnetic stir plate. Stirring speed was increased from 0 rpm to 700 rpm within 5 minutes to assure the movement of the stirring bar. Due to the high substrate loading the autoclave needed to be repressurized several times with H.sub.2 to 100 bar. After no pressure drop was observable, the autoclave was cooled to 0° C. in an ice bath and was than depressurized to ambient pressure.

[0055] Using the general procedure, a series of test hydrogenations were made. The results are listed in the following table (average results out of three test reactions):

TABLE-US-00003 MBSDME MGBL BDO 3-MTHF Entry Catalyst S/C (in %) (in %) (in %) (in %) 1 1b 1000 0 2 2 88 2 1b 2000 23 10 0 35 3 2b 1000 2 2 1 93 4 2b 2000 3 1 7 81 5 3b 1000 2 2 1 94 6 3b 2360 0 0 77 20 7 3b 2000 0 5 1 87

[0056] However in the reaction corresponding to entry 7 additionaly 0.2 ml H.sub.2O were given to the reaction. “S/C” means the ratio of substrate/catalyst (in mol/mol). The further abbreviations are explained above.

[0057] It can be seen from the table that when a concentration of substrate/catalyst S/C of 2000 more is used, as in entries 2, 4 and 6 the inventive catalyst is clearly superior over the catalyst 1b and also 2b. This is quite surprising when taking into account that comparative catalyst 2b has a substitution in para-position, which is a strong indication that the ortho and/or meta-substitution has a great effect. 2b, however is not as efficient as the unsubsituted catalyst 1b.

[0058] Furthermore it could be found that even at a much lower concentration (2360 vs. 1000) the inventive catalyst is still active and even has higher TONs as with the higher concentration, whereas with the comparative catalyst 1b it is the contrary, here significant non-reduced products are found. Catalyst 2b behaves similar as 1b, although here the differences are not as strong.

[0059] Even when adding significant amounts of water—which would usually be expected to lead to a complete inertness of the catalyst—the inventive catalyst was still active and gave only minor amounts of not fully reduced byproducts, but not of MBSDME as it was the case with the other catalysts in the absence of water.

[0060] The particular combinations of elements and features in the above detailed embodiments are exemplary only; the interchanging and substitution of these teachings with other teachings in this and the patents/applications incorporated by reference are also expressly contemplated. As those skilled in the art will recognize, variations, modifications, and other implementations of what is described herein can occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the foregoing description is by way of example only and is not intended as limiting. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The invention's scope is defined in the following claims and the equivalents thereto. Furthermore, reference signs used in the description and claims do not limit the scope of the invention as claimed.