Patent Application
20060058178
The present invention concerns novel ligands for transition metals, their production and their use in catalytic reactions, especially for refining haloaromatics.
Haloaromatics, especially chlorine aromatics, are versatile intermediates of the chemical industry, which are used as pre-products for the production of agro-intermediates, pharmaceuticals, dyes, etc. Vinyl halides are also important intermediates that are used as starting materials for polymers and for the production of the aforementioned products.
Commonly used catalysts for the functionalisation of haloaromatics or vinyl halides to aromatic olefins or dienes (Heck reaction, Stille reaction), biaryls (Suzuki reaction), alkynes (Sonogashira reaction), carboxylic acid derivatives (Heck carbonylation), amines (Buchwald-Hartwig reaction) are palladium and nickel catalysts. Palladium catalysts are generally advantageous as far as the breadth of applicability of coupling substrates and in some cases catalyst activity is concerned, whilst nickel catalysts offer advantages in the area of the reaction of chlorine aromatics and vinyl chlorides and in terms of the cost of the metal.
Palladium and nickel catalysts that are used in the activation and further refining of haloaromatics are both palladium(II) and/or nickel(II) and palladium(0) and/or nickel(0) complexes, although it is known that palladium(0) and nickel(0) compounds are the actual catalysts for the reaction. In particular, coordinately unsaturated 14- and 16-electron palladium(0) and nickel(0) complexes, which are stabilised with donor ligands such as phosphanes, are formulated as active species according to instructions given in the literature.
Where iodides are used as educts in coupling reactions, it is also possible to dispense with the use of phosphane ligands. However, aryl and vinyl iodides are very expensive starting compounds and, in addition, stoichiometric amounts of iodine salt waste are obtained during their reaction. If less expensive educts, such as aryl bromides or aryl chlorides, are used in the Heck reaction, stabilising and activating ligands have to be added in order for the educts to be reacted in a catalytically effective manner.
The catalyst systems described for olefinations, alkynylations, carbonylations, arylations, aminations and similar reactions frequently have satisfactory catalytic turnover numbers (TON) only with uneconomic starting materials such as iodine aromatics and activated bromine aromatics. Otherwise, in the case of deactivated bromine aromatics and especially chlorine aromatics, large amounts of catalyst—usually over 1 mol %—generally have to be added in order to achieve technically useable yields (>90%). In addition, due to the complexity of the reaction mixtures, simple catalyst recycling is not possible, which means that recycling the catalyst also gives rise to high costs which generally stand in the way of implementation in industry. Furthermore, especially in the production of active ingredients or of pre-products for active ingredients, it is undesirable to work with large amounts of catalyst, since otherwise catalyst residues remain in the product in this case.
More recent active catalyst systems are based on cyclopalladated phosphanes (W. A. Herrmann, C. Broβimer, K. Öfele, C.-P. Reisinger, T. Priermeier, M. Beller, H. Fischer, Angew. Chem. 1995, 107, 1989; Angew. Chem. Int Ed. Engl. 1995, 34, 1844) or mixtures of sterically exacting aryl phosphanes (J. P. Wolfe, S. L. Buchwald, Angew. Chem. 1999, 111, 2570; Angew. Chem. Int Ed. Engl. 1999, 38, 2413) or tri-tert.-butyl phosphane (A. F. Littke, G. C. Fu, Angew. Chem. 1998, 110, 3586; Angew. Chem. Int Ed. Engl. 1998, 37, 3387) with palladium salts or palladium complexes.
However, inexpensive chlorine aromatics generally cannot be activated in a technically satisfactory manner even with these catalysts, in other words catalyst productivities (TON) are <10000 and catalyst activities (TOF) are <1000 h−1. This means that comparatively large amounts of catalyst have to be used to obtain high yields, a practice that is associated with high costs. For example, at current noble metal prices, using 1 mol % palladium catalyst, the catalyst costs for producing one kilogram of an organic intermediate with a molecular weight of 200 are over 100 US$, which illustrates the need to improve catalyst productivity. For that reason, despite all the further developments in catalysts over recent years, few industrial arylation, carbonylation, olefination, etc., reactions of chlorine aromatics have emerged to date.
For the reasons stated, the object underlying the present invention was to satisfy the great need for novel, more productive catalyst systems which have simple ligands and exhibit none of the disadvantages of the known catalytic processes, which are suitable for large-scale use and which convert inexpensive chlorine and bromine aromatics and corresponding vinyl compounds to their respective coupling products with high yield, catalyst productivity and purity.
This object is achieved according to the invention by the development of novel P-functionalised amines of nitrogen-containing aromatics, in particular by P-functionalised aminopyridines, having the general formula
R1(R2)P—N(R′)R″ (I)
wherein
The aforementioned radicals can themselves each be mono- or polysubstituted.
These substituents can mutually independently be hydrogen, C1-C20 alkyl, C2-C20 alkenyl, C1-C10 haloalkyl, C3-C8 cycloalkyl, C2-C9 heteroalkyl, aromatic radicals having 6 to 10 C atoms, in particular phenyl, naphthyl or fluorenyl, wherein 1, preferably up to 4, of the C atoms can also be replaced by a heteroatom, mutually independently selected from the group N, O and S, C1-C10 alkoxy, preferably OMe, C1-C9 trihalomethylalkyl, preferably trifluoromethyl and trichloromethyl, halo, especially fluoro and chloro, nitro, hydroxy, trifluoromethyl sulfonato, oxo, amino, C1-C8 substituted amino in the forms NH-alkyl-C1-C8, NH-aryl-C5-C6, N-alkyl2-C1-C8, N-aryl2-C5-C6, N-alkyl3-C1-C8+, N-aryl3-C5-C6+, NH—CO-alkyl-C1-C8, NH—CO-aryl-C5-C6, cyano, carboxylato in the forms COOH and COOQ wherein Q represents either a monovalent cation or C1-C8 alkyl, C1-C6 acyloxy, sulfinato, sulfonato in the forms SO3H and SO3Q, wherein Q represents either a monovalent cation, C1-C8 alkyl or C6 aryl, phosphato in the forms PO3H2, PO3HQ and PO3Q2, wherein Q represents either a monovalent cation, C1-C8 alkyl or C6 aryl, tri-C1-C6 alkyl silyl, especially SiMe3,
wherein
R1 and R2 are preferably mutually independently a radical selected from the group consisting of phenyl, cyclohexyl, alkyl, 2-alkylphenyl, 3-alkylphenyl, 4-alkylphenyl, 2,6-dialkylphenyl, 3,5-dialkylphenyl, 3,4,5-trialkylphenyl, 2-alkoxyphenyl, 3-alkoxyphenyl, 4-alkoxyphenyl, 2,6-dialkoxyphenyl, 3,5-dialkoxyphenyl, 3,4,5-trialkoxyphenyl, 3,5-dialkyl-4-alkoxyphenyl, 4-dialkylamino, wherein the aforementioned alkyl and alkoxy groups can preferably each mutually independently contain 1 to 6 carbon atoms, 3,5-trifluoromethyl, 4-trifluoromethyl, 2-sulfonyl, 3-sulfonyl and 4-sulfonyl.
R1 and R2 are particularly preferably mutually independently a radical selected from the group consisting of phenyl, cyclohexyl and tert.-butyl.
In a preferred embodiment the radicals R1 and R2 are identical.
R′ is an aromatic radical containing at least one N atom and having 4 to 13 C atoms, which is bound to the nitrogen atom according to formula I in the 2-position relative to the at least one aromatic N atom. One or more, preferably up to three, of the cited aromatic C atoms can also be replaced here by a further heteroatom, mutually independently selected from the group consisting of N, O and S.
The aromatic radical having 4 to 13 C atoms is preferably pyrimidyl, pyrazinyl, pyridyl or quinolinyl.
R″ is trimethylsilyl or an aromatic radical having 5 to 14 C atoms, wherein one or more, preferably up to four, C atoms can be replaced by a heteroatom mutually independently selected from the group consisting of N, O and S.
The aromatic radical is preferably pyrimidyl, pyrazinyl, pyridyl, quinolinyl, phenyl, fluorenyl or naphthyl.
In a preferred embodiment R″ is the same radical as R′, the radical preferably being bound to the N atom according to formula (I) in the same way as R′, in other words in the 2-position relative to the aromatic N atom.
The radicals listed for R′ and R″ can furthermore mutually independently display at least one, particularly preferably up to three, substituents in addition to hydrogen atoms, which can mutually independently be selected from the group consisting of C1 to C8 alkyl, O-alkyl(C1-C8), OH, OCO-alkyl(C1-C8), O-phenyl, phenyl, aryl, fluorine, NO2, Si-alkyl(C1-C8)3, CN, COOH, CHO, SO3H, NH2, NH-alkyl(C1-C8), N-alkyl(C1-C8)2, NH-aryl, N-aryl2, P(alkyl(C1-C8))2, P(aryl)2, SO2-alkyl(C1-C6), SO-alkyl(C1-C6), CF3, NHCO-alkyl(C1-C4), COO-alkyl(C1-C8), CONH2, CO-alkyl(C1-C8), NHCHO, NHCOO-alkyl(C1-C4), CO-phenyl, COO-phenyl, CH═CH—CO2-alkyl(C1-C8), CH═CHCOOH, PO(phenyl)2, PO(alkyl(C1-C4))2, PO3H2, PO(O-alkyl(C1-C6))2, SO3(alkyl(C1-C4)), wherein aryl represents an aromatic having 5 to 14 ring-carbon atoms, wherein one or more ring-carbon atoms can be replaced by nitrogen, oxygen and/or sulfur atoms and the alkyl radicals can be branched, unbranched and/or cyclic, saturated or unsaturated.
Heteroaromatic radicals can for example be at least five-membered rings containing 1 to 13 ring-carbon atoms, which contain up to 4 nitrogen atoms and/or up to 2 oxygen or sulfur atoms. Preferred heteroaromatic aryl radicals contain one or two nitrogen or one oxygen or one sulfur or one nitrogen and one oxygen or sulfur heteroatom.
The at least one substituent for R′ and R″ is preferably a group selected from C1-C8-alkyl, O-alkyl(C1-C8), OH, OCO-alkyl(C1-C8), O-phenyl, phenyl, aryl, fluorine, Si-alkyl(C1-C8)3, CN, COOH, SO3H, SO2-alkyl(C1-C6), SO-alkyl(C1-C6), CF3, COO-alkyl(C1-C8), CO-alkyl(C1-C8), CO-phenyl, COO-phenyl and SO3(alkyl(C1-C4)).
The at least one substituent for R1, R2, R′ and R″, in addition to H atoms, is mutually independently in each case particularly preferably a radical selected from the group consisting of C1 to C6 alkyl, O-alkyl(C1-C6), OH and N-pyridyl2.
The substituted radical R′ is particularly preferably a radical selected from the group consisting of 3-methylpyridyl, 4-methylpyridyl, 6-methylpyridyl, 4,6-dimethylpyridyl, 6-methoxypyridyl, pyridyl, pyrimidyl, pyrazinyl, 4-methyl quinolinyl or Py2(o-P) (see Table 1), wherein R′ is bound in the 2-position to the N atom according to formula (I).
The present invention also provides a process for the production of P-functionalised N-containing aromatic amine ligands, wherein in the presence of a strong base, a compound having the formula NHR′R″ is reacted with a compound having the formula R1(R2)PX, wherein R1, R2, R′ and R″ have the same meaning as in formula (I) and wherein X preferably stands for a halogen atom, in particular for chlorine or bromine. The strong base is preferably an organometallic reagent, particularly preferably butyl lithium, sec.-butyl lithium, tert.-butyl lithium or lithium diisopropylamine. The reaction can be performed in an organic solvent, for example hexane, under anaerobic conditions.
Amines having the formula NHR′R″ and in particular a large number of bipyridyl amines, 2-aminopyridines or related N-heterocyclic amines, which can be used as starting compounds for the production of ligands according to the invention, can be prepared here by means of palladium-catalysed aryl aminations starting from primary amines in the classical way according to the scheme below (S. Wagaw, S. L. Buchwald, J. Org. Chem. 1996, 61, 7240; J. Stilberg et al., J. Organomet. Chem. 2001, 622, 6-18; J. F. Hartwig, Synleft 1996, 329):
R′NH2+R″X→R′NHR″ or
R″NH2+R′X→R′NHR″,
wherein X stands for a halogen atom, in particular for chlorine, bromine or iodine, or possibly for a protected oxygen atom, for example OTf.
In particular, one of the following amines, selected from the group consisting of N-(4-methylpyrid-2-yl)-N-(pyrimid-2-yl) amine, N-(4,6-dimethylpyrid-2-yl)-N-(6-methoxypyrid-2-yl) amine, N,N-bis(pyrazinyl) amine, N,N,N′-tris(pyrid-2-yl)-o-phenylene diamine, can be used as a starting compound for the ligands according to the invention. These novel amines are also provided by the present invention.
The novel ligands are used according to the invention as catalysts in combination with transition metal complexes or transition metal salts of subgroup VIII of the periodic table of elements, such as e.g. palladium, nickel, platinum, rhodium, iridium, ruthenium, cobalt.
The ligands according to the invention can generally be added in situ to appropriate transition metal precursor compounds and used in this way for catalytic applications.
The present invention therefore also provides a coordination compound, comprising a P-functionalised amine according to the invention of an N-containing aromatic and a metal from group VIII. The transition metal here is preferably part of a five-membered ring and one phosphorus atom and two nitrogen atoms are particularly preferably also part of this five-membered ring.
By reason of the formation of a five-membered ring, in place of the six-membered ring that is normally to be found, the complex is especially well suited to the catalysis of reactions with substrates carrying substituents that are sterically particularly exacting.
The present invention also provides a process for the production of the coordination compounds according to the invention, characterised in that ligands according to the invention, which are preferably obtained as described above, are reacted with a complex and/or salt of a transition metal from group VIII of the periodic table. The group VIII transition metal is preferably Pd or Ni.
Examples of palladium components that can be used with the ligands according to the invention include: palladium(II) acetate, palladium(II) chloride, palladium(II) bromide, lithium tetrachloropalladate(II), palladium(II) acetyl acetonate, palladium(0) dibenzylidene acetone complexes, in particular dipalladium tris-dibenzylidene acetone, palladium (1,5-cyclooctadiene) chloride, palladium(0) tetrakis (triphenyl phosphane), palladium(0) bis(tri-o-tolyl phosphane), palladium(II) propionate, palladium(II) bis(triphenyl phosphane) dichloride, palladium(0) diallyl ether complexes, palladium(II) nitrate, palladium(II) chloride bis(acetonitrile), palladium(II) chloride bis(benzonitrile) and other palladium(0) and palladium(II) complexes.
Examples of nickel precursors that can be used include bis(1,5-cyclooctadiene) nickel(0), bis(triphenyl phosphine) nickel(II) bromide, nickel(II) acetate, nickel(II) chloride, nickel(II) acetylacetonate, nickel(II) bromide, nickel(0) tetrakis (triphenyl phosphane), nickel(II) iodide, nickel(II) trifluoracetylacetonate or nickel bromide dimethoxyethane adduct.
Alternatively, production of the complex can be made shorter by producing it starting directly from the ligand precursors, either in a batch process or, particularly preferably, in situ, without the need for a stepwise procedure and/or purification of the ligands according to the invention.
In this way, using di-tert.-butyl chlorophosphane, for example, production of the complex starting from the ligand precursors can be performed in situ by setting out all reaction partners together at the start.
If diphenyl and dicyclohexyl chlorophosphane are used, the complex is preferably produced in a batch process starting from the ligand precursors.
The complexes that are formed are particularly preferably also examined for activity without prior purification, by introducing the substrates for the reaction to be performed directly into the reaction solution obtained from production of the complexes.
In this way the entire process, starting from the ligand precursors through to the activity test for the complexes obtained, can therefore be performed in a batch process, in other words in a one-pot process. This is particularly advantageous since in this way a large number of complexes can efficiently be tested in parallel for catalytic activity on a large scale, and furthermore a miniaturisation of the process becomes possible. This ultimately leads to huge time and cost savings.
A particular advantage of the ligands and complexes according to the invention is therefore that they can be prepared efficiently and diversely by parallel synthesis under anaerobic conditions.
The present invention also provides a process for the activation of haloaromatics, characterised in that a ligand according to the invention, in the presence of a metal from group VIII of the periodic table and/or a coordination compound according to the invention, preferably in the presence of a base, such as e.g. K2CO3, NaOtBu, K3PO4 or Na2CO3, is used as catalyst.
The ligands produced according to the invention can thus be used as the ligand component for the catalytic production of arylated olefins (Heck reactions), biaryls (Suzuki reactions), α-aryl ketones and amines from aryl halides or vinyl halides and/or for the production of dienes, benzoic acid derivatives, acrylic acid derivatives, aryl alkanes, alkynes and amines. In addition, other transition metal-catalysed reactions such as palladium- and nickel-catalysed carbonylations of aryl halides, alkynylations with alkynes (Sonogashira couplings), cross-couplings with organometallic reagents (zinc reagents, tin reagents, etc.) can also be performed with the novel catalyst systems.
The compounds produced in this way can be used inter alia as UV absorbers, as intermediates for pharmaceuticals and agrochemicals, as ligand precursors for metallocene catalysts, as perfumes, active ingredients and building blocks for polymers.
In catalytic applications the phosphane ligand is generally used in excess relative to the transition metal. The ratio of transition metal to ligand is preferably 1:1 to 1:1000. Ratios of transition metal to ligand of 1:1 to 1:100 are particularly preferred. The exact ratio of transition metal to ligand to be used depends on the specific application and also on the amount of catalyst used.
According to the invention the transition metal concentration is preferably between 5 mol % and 0.001 mol %, particularly preferably between 1 mol % and 0.01 mol %.
According to the invention the catalysts according to the invention are preferably used at temperatures of 0 to 200° C.
A particular advantage of the ligands according to the invention is the high activity that the ligands induce in the activation of inexpensive yet inert chlorine aromatics. As shown in the comparative examples, palladium catalysts with the novel ligands surpass the best catalyst systems known to date.
For example, some of the most active ligands known until now in the palladium complex- and/or nickel complex-catalysed Suzuki coupling are TtBP (A. F. Littke, G. C. Fu, Angew. Chem. Int. Ed. 1998, 37, 3387-3388; A. F. Littke, C. Dai, G. C. Fu, J. Am. Chem. Soc. 2000, 122, 4020-28) and BINAP and BDPP (Wagaw and Buchwal, J. Org. Chem. 1996, 61, 724041; J. F. Hartwig, Synlett 1996, 329-340; Silberg et al., J. Organomet. Chem. 2001, 622, 6-18; Schareina et al. Eur. J. Inorg. Chem. 2001). Their activity is reproducibly surpassed by the catalyst systems according to the invention, as can also be seen from the tables.
General information: materials and mode of operation:
The commercially available materials were used without any further purification. Materials sensitive to air or water were handled in dried Schlenk flasks with strict exclusion of air and water or in a glove box (Braun, Labmaster 130). Solvents (Aldrich) and NMR solvents (Cambridge Isotope Laboratories, min. 99 atom % D) were distilled from sodium tetraethyl aluminate or molecular sieve (CH2Cl2, CD2Cl2).
In order to obtain a comparison with regard to reactivity, the following ligands, which represent the closest prior art, were used: TtBP=tri(t-butyl) phosphane, BINAP=rac.-bis(diphenyl phosphino)-1,1′-binaphthyl, BDPP=1,3-bis(diphenyl phosphino)propane; DtBPCl=di-tert.-butyl phosphine chloride;
The amines listed below were used as precursors for the production of the ligands produced in the embodiment examples.
2,2′-Dipyridyl Amine, Abbreviation—PyPy: Commercially Available
1J. Silberg, T. Schareina, R. Kempe, K. Wurst, M. R. Buchmeiser, J. Organomet. Chem., 2001, 622, 6.
2M. R. Buchmeiser, T. Schareina, R. Kempe, K. Wurst, J. Organomet. Chem., being printed.
For the ligands with only one heterocyclic substituent (e.g. PSiPy, CSiPm, etc.) the corresponding commercially available amines were used as starting material.
Trimethylsilyl-substituted compounds were produced from the amine in THF by addition of 1 equivalent of n-BuLi solution in hexane at −77° C., heating to room temperature, addition of 1 equivalent of pure (CH3)3SiCl and stirring for 24 hours at room temperature. Other modifications with phosphines were produced in a similar way.
The phosphanyl radicals diphenyl chlorophosphane, dicyclohexyl chlorophosphane and di-tert.-butyl chlorophosphane used according to the invention are all commercially available.
The metal precursors were commercially available or were produced by instructions in the literature.
a) Production of Precursor—4MPm
Combined under Ar in a 100 ml Schlenk flask. The mixture is heated to 90° C. without solvent with stirring for 24 hours. Melts to a dark brown melt with no perceptible solids components. Working up: addition of dichloromethane (dissolves completely), then washed with water and saturated sodium chloride solution, dried over sodium sulfate and evaporated. Dark reddish brown tarry mass. The raw product is taken up with dichloromethane on silica gel, introduced into a Soxhiet thimble and extracted with petroleum ether (boiling range 80-100° C.)/toluene, v/v approx. 3:1, for 3 days. The deposit that appears after cooling is filtered through a P4 sintered-glass filter and washed with n-hexane and n-pentane. Weighed out quantity 2.12 g, 28% of theoretical, NMR pure.
Elemental analysis, calculated for C10H10N4 (Mw=186.21 g/mol): C, 64.50; H, 5.41; N, 30.09. Found: C, 64.47; H, 5.30; N, 30.31.
1H-NMR (CDCl3): 9.16 (bs, 1H, NH), 8.55 (m, 2H), 8.24 (m, 2H), 6.77 (m, 2H), 2.38 (s, 3H, CH3)
13C-NMR (CDCl3): 159.7, 158.4, 153.2, 150.1, 147.5, 136.1, 119.3, 113.7, 113.5, 22.1.
b) Production of Precursor—46MMx
The mixture is heated to 75° C. in an oil bath with stirring, and the temperature raised after 2 hours to 80° C. After a further 30 minutes a deposit is precipitated out. Thin-layer chromatography analysis (solvent dichloromethane, mobile solvent PE/ethyl acetate 1:1) shows that the reaction is still not completed after 4 hours, so stirring is continued for a further 12 hours at 80° C. Working up is performed with dichloromethane and water, the organic phase is dried over sodium sulfate and evaporated to a brown oil, which solidifies when left to stand overnight. The total amount is recrystallised out of 20 ml n-hexane. After crystallising out, large crystal conglomerates are obtained, which could not be removed from the flask. The solvent is decanted off, the solid rinsed with n-hexane, dissolved in dichloromethane, filtered, evaporated. The product is melted in an oil pump vacuum until no further solvent gases emerge, and allowed to stand. Reddish brown oil, from which crystal clusters grow rapidly. Weighed out quantity 4.81 g (85% of theoretical). Analyses OK.
Elemental analysis, calculated for C13H15N3O (Mw=229.28 g/mol): C, 68.10; H, 6.59; N, 18.33. Found: C, 68.24; H, 6.64; N, 18.08. 1H(C6D6): 7.347 (bs, 1H, NH); 7.12 (t, 1H); 6.98 (d, 1H); 6.92 (s, 1H); 6.30 (d, 1H); 6.26 (s, 1H); 3.77 (s, 3H, —O—CH3); 2.38 (s, 3H); 1.92 (s, 3H). 13C(C6D6): 163.8; 156.8; 154.4; 153.3; 148.7; 140.5; 117.1; 109.5; 103.3; 102.2; 53.3; 24.5; 21.2.
c) Production of Precursor—PaPa
Weigh into a Schlenk flask under argon, then add approx. 20 ml absolute toluene, stir at 80° C. in an oil bath. The contents of the Schlenk flask soon turn yellow, deposit. Working up after 4 hours. The reaction mixture is poured onto a sintered-glass filter and the Schlenk flask rinsed with ether. The solid on the sintered-glass filter is washed with ether, water and again with ether. Recrystallisation from water, with hot filtration. After drying in a desiccator over KOH, 1.03 g of fine orange-yellow needles are obtained (60% of theoretical).
Elemental analysis, calculated for C8H7N5 (Mw=173.17 g/mol): C, 55.48; H, 4.07; N, 40.44. Found: C, 55.86; H, 4.19; N, 40.37. 1H (DMSO-d6): 9.52 (bs, 1H, NH); 8.16 (s, 2H); 7.43 (s, 2H); 7.30 (s, 2H). 13C (DMSO-d6): 150.6; 142.1; 136.9; 135.6.
d) Production of Precursor—Py2(o-P)Py
Add 20 ml diethylene glycol dimethyl ether, heat to 110° C., stir. Adjusted to 125° C. after 2 days, reaction terminated after a total of 6 days and the mixture worked up. The solvent is removed by condensation in a dry-ice-cooled flask. Water and dichloromethane are added until both phases are clear. The mixture is transferred to a separating funnel. The organic phase is washed once with water and once with saturated sodium chloride solution, dried over sodium sulfate, evaporated. Purification is performed by column chromatography on silica gel 60 from Merck, mobile solvent is ethyl acetate. The target product is eluted after the intermediate N,N′-bis(pyrid-2-yl)-o-phenylene diamine. After removal of the solvents, the weighed-out quantity is 1.70 g (50% of theoretical).
Elemental analysis, calculated for C21H17N5 (Mw=339.39 g/mol): C, 74.32; H, 5.05; N, 20.63. Found: C, 74.33; H, 4.91; N, 20.76. 1H (CDCl3): 8.22 (dd, 2H); 8.10 (d, 1H); 8.03 (m, 1H); 7.46 (m, 2H); 7.38 (bs, 1H), NH); 7.31 (m, 2H); 7.23 (dd, 1H); 7.03 (m, 1H); 6.91 (d, 2H); 6.82 (m, 2H); 6.59 (m, 2H). 13C, 157.3; 155.4; 148.3; 137.8; 137.4; 130.3; 128.3; 123.3; 121.6; 118.1; 115.8; 114.8; 110.1.
a) Production of the Ligand Ph2P—N(pyridyl)2
1.6 ml 2.5M (4 mmol) n-BuLi in hexane are added to 0.68 g (4 mmol) bipyrid-2-yl amine in 10 ml ether under argon at −77° C. After 1 hour 0.72 ml (0.882 g, 4 mmol) chlorodiphenyl phosphine in 4 ml ether are added dropwise. During the dropwise addition the contents of the Schlenk flask turn bright yellow. After stirring for 48 hours at room temperature the solution is transferred to another Schlenk flask by filtration and then rewashed twice with a mixture of 10 ml ether and 10 ml THF. The solvent is removed by condensation in vacuo in a flask cooled with dry ice, the solid is then dried under 1 mbar and at room temperature. Weighed out quantity 1.42 g (quantitative) NMR-pure substance. A sample is dissolved in diethyl ether and covered with a layer of n-hexane. After some time colourless crystals are precipitated out, which are examined by X-ray structural analysis.
Elemental analysis: C22H18N3P; molecular weight: 355.37 g-mol−1; calculated: C. 74.35; H. 5.11; N. 11.82; found: C, 74.50; H, 5.31; N, 11.68. 1H(C6D6): 8.16 (m, 2H); 7.73 (m, 4H); 6.97 (m, 6H); 6.57 (d, 2H); 6.33 (ddd, 2H). 13C(C6D6): 158.35; 158.29; 148.81; 138.74; 138.54; 136.97; 136.07; 136.06; 133.76; 133.55; 132.04; 128.77; 128.53; 128.11; 118.37; 118.26. 31p (C6D6): 69.37.
b) Production of the Pd Complex from Ph2P—N(pyridyl)2
4 ml of dry dichloromethane are added to 0.071 g (0.25 mmol) (COD)PdCl2 and 0.089 g Ph2P—N(pyridyl)2 in a Schlenk flask under argon. The solids dissolve very quickly. By covering with a layer of 6 ml diethyl ether, pale yellow crystals are obtained after approximately 1 week. Isolation by filtration, washed with 4 ml ether, dried in an oil pump vacuum. Yellow crystals, 0.10 g (75% of theoretical).
Elemental analysis: C22H18Cl2N3PPd; molecular weight: 532.70 g·mol1; calculated: C. 49,60; H. 3, 41; N. 7, 89; found: C, 49.29; H, 3.51, N, 7.81. 1H (CD2Cl2): 9.43 (m, 1H); 8.24 (m, 1H); 7.88 (m, 5H); 7.66 (m, 1H); 7.50 (m, 4H); 7.37 (m, 5H); 7.08 (m, 1H); 7.02 (m, 1H); 6.70 (m, 1H); 6.54 (m, 1H). 3C (CD2Cl2): 150.4; 150.1; 149.1; 140.2; 138.5; 133.4; 133.3; 132.2; 127.8; 127.7; 125.9; 125.3; 122.8; 121.7; 121.7; 120.8; 118.0. 31p (CD2Cl2): 99.2.
All solvents are dried by standard methods, distilled from Na benzophenone ketyl and sodium tetraethylate and stored under argon. Commercially available starting materials were used without any further purification, liquids stored under argon. All operations were performed under argon in Schlenk flasks.
Stock solutions of the substrates, ligands and metal precursors are produced in the stated solvents, the concentration for substrates (chlorine aromatics and phenyl boronic acid) was 1 mol l−1, for ligands and metal precursors c=0.025 mol l−1.
In the case of the diphenyl- and dicyclohexyl-substituted phosphanyl radicals the ligands were produced as follows: the amine (1 mmol) is metalated with 0.4 ml of a 2.5M solution of n-BuLi in hexane at −77° C., held for 30 minutes at −77° C., then allowed to heat up to room temperature, then one equivalent of chlorodiphenyl phosphane or chlorodicyclohexyl phosphane is added and the mixture stirred for at least 24 hours at room temperature. The solution is topped up with inert solvent so that the concentration of the ligand is 0.025 mol l−1.
Production of the di(tert.-butyl)phosphane-substituted ligands was performed in situ, by heating 1 equivalent each of amine, chlorodi(tert.-butyl)phosphane and metal precursor as stock solutions together with the base in a Schlenk reaction vessel for 1 hour at 60° C., then the substrates are added at room temperature.
The screening reactions were performed as follows: all reactions were performed in the parallel equipment under Ar. The base was dried in advance in vacuo at 130° C. for 24 hours, and the quantities weighed out in a vacuum box. Stock solutions of the substrates (haloaromatics 1 ml, phenyl boronic acid 1.2 ml) and reagents (ligands and metal precursors, c=0.025 mol 1-1) were then added and brought up to room temperature with stirring.
At the end of the reaction time aliquot samples were taken, an internal standard (dodecane) added, dilution carried out with diethyl ether and analysis performed by gas chromatography. In each case biphenyl was indicated as a by-product.
Library 1: solvent THF; 1.2 mmol base; 1 mmol 4-chlorobenzonitrile; 1.2 mmol phenyl boronic acid; 1% metal (precursor); 1 equivalent (relative to the metal) ligand.
Library 2: solvent THF; 1.2 mmol base, 1 mmol 4-chloroanisol; 1.2 mmol phenyl boronic acid; 1% metal (precursor); 1 equivalent (relative to the metal) ligand; 60° C.; 24 hours.
Library 3: solvent 1,4-dioxan; 1.2 mmol base; 1 mmol 3-chloropyridine; 1.2 mmol phenyl boronic acid; 1% metal (precursor); 1 equivalent (relative to the metal) ligand; 60° C.; 24 hours
The experiments were performed in the same way as the Suzuki reactions described, in a parallel reactor. Unless otherwise stated, the reaction temperature was 60° C. and the reaction time 24 hours. The solvent in all cases is THF. The molar ratios of the reaction partners were:
Substrate: 1 mmol (1M solvent).
Reagent (phenyl magnesium bromide): 1.2 mmol (1M solution).
Ligands: 0.01 mmol (0.02 mmol for monodentate ligands), unless otherwise stated, 0.4 ml (0.025M solution).
Metal precursors: 0.01 mmol, (0.025M solution).
At the end of the 24 hours the Schlenk flasks were allowed to cool and 0.5 ml methanol added to each to annihilate excess reagent. The yields were then determined by GC.
a) Cross-Coupling: 2-chloro-m-xylene+Phenyl Magnesium Bromide
b) Cross-Coupling: 2-chlorotoluene+Phenyl Magnesium Bromide
c) Cross-Coupling: 2-CIPy+PhMgBr
d) Cross-Coupling: 4-ClAn+Phenyl Magnesium Bromide
e) Cross-Coupling: 3-CIPy+PhMgBr
| Number | Date | Country | Kind |
|---|---|---|---|
| 101 57 358.8 | Nov 2001 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP02/13048 | 11/21/2002 | WO | 6/30/2005 |
