Patent Application
20050288523
The present invention relates to chiral diphosphorus compounds and transition metal complexes thereof, and to a process for preparing chiral diphosphorus compounds and oxides thereof. In a further aspect, the invention relates to the use of the chiral diphosphorus compounds or transition metal complexes thereof in asymmetric syntheses.
Enantiomerically enriched chiral compounds are valuable starting substances for preparing agrochemicals and pharmaceuticals. Asymmetric catalysis has gained great industrial significance for the synthesis of such enantiomerically enriched chiral compounds.
The multitude of publications in the field of asymmetric synthesis shows clearly that transition metal complexes of diphosphorus compounds are particularly suitable as catalysts in asymmetric reactions (H. C. Brown, K. Murray, J. Am. Chem. Soc., 1959, 81, 4108). In particular, transition metal complexes of diphosphorus compounds have found use in industrial processes as catalysts in asymmetric hydrogenations of C═O, C═N and C═C bonds, hydrocyanations and hydroformylations.
For example, Achiwa et al., Synlett, 1991, 49 disclose that it is possible to use (1R,2R)-1-diphenylphosphino-2-diphenylphosphinomethylcyclopentane as a ligand in rhodium-catalysed hydrogenation to achieve satisfactory enantioselectivities.
However, the fundamental disadvantage is that the preparation process described does not allow steric and electronic variation of the ligand system which is needed for controlled optimization and adaptation of the ligand and thus of the catalyst for a given substrate. This disadvantage has hitherto complicated industrial utilization.
There is therefore a need to develop a ligand system which can be readily varied in its steric and electronic properties and whose transition metal complexes as catalysts in asymmetric synthesis, in particular asymmetric hydrogenations, enable not only high enantioselectivity but also high turnover rates. In addition, there is a need to develop convenient access for such a ligand system and the corresponding precursors.
Compounds of the formula (I) have now been found
in which
The scope of the invention includes all radical definitions, parameters and illustrations listed above and hereinbelow, in general or within areas of preference, in any combination with one another, i.e. between the particular areas and areas of preference too.
In the context of the invention, unless stated specifically, aryl is preferably a carbocyclic aromatic radical having 6 to 24 skeleton carbon atoms or a heteroaromatic radical having 5 to 24 skeleton carbon atoms, in which no, one, two or three skeleton carbon atoms per cycle, but at least one skeleton carbon atom in the entire molecule, may be substituted by heteroatoms selected from the group of nitrogen, sulphur or oxygen. In addition, the carbocyclic aromatic radicals or heteroaromatic radicals may be substituted by up to five identical or different substituents per cycle, selected from the group of hydroxyl, fluorine, nitro, cyano, free or protected formyl, C1-C12-alkyl, C5-C14-aryl, C6-C15-arylalkyl, —PO—[(C1-C8)-alkyl]2, —PO-[(C5-C14)-aryl]2, —PO—[(C1-C8)-alkyl)(C5-C14)-aryl)], tri(C1-C8-alkyl)siloxy or radicals of the formulae (IIa) to (IIf). The same applies to the aryl moiety of an arylalkyl radical.
For example, aryl is more preferably phenyl, naphthyl or anthracenyl, each of which is optionally mono-, di- or trisubstituted by radicals which are each independently selected from the group of C1-C6-alkyl, C5-C14-aryl, C1-C6-alkoxy, C1-C6-alkoxy-carbonyl, halogen, hydroxyl, nitro or cyano.
In the context of the invention, alkyl, alkylene and alkoxy, unless stated specifically, are preferably each independently a straight-chain, cyclic, branched or unbranched alkyl, alkylene and alkoxy radical respectively, each of which may optionally be further substituted by C1-C4-alkoxy radicals. The same applies to the alkylene moiety of an arylalkyl radical.
For example, alkyl is more preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, cyclohexyl and n-hexyl, n-heptyl, n-octyl, isooctyl, n-decyl and n-dodecyl.
For example, alkylene is preferably 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, S,S- or R,R-2,5-hexylene, 1,4-cyclohexylene, 1,2-cyclohexylene and 1,8-octylene.
For example, alkoxy is preferably methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, tert-butoxy and cyclohexyloxy.
In the context of the invention, arylalkyl, unless stated specifically, is preferably in each case independently a straight-chain, cyclic, branched or unbranched alkyl radical which is mono- or polysubstituted, more preferably monosubstituted, by aryl radicals as defined above.
In the context of the invention, unless stated specifically, haloalkyl and haloalkylene are preferably each independently a straight-chain, cyclic, branched or unbranched alkyl and alkylene radical respectively, each of which may be substituted singly, multiply or fully by halogen atoms selected independently from the group of fluorine, chlorine, bromine and iodine.
For example, haloalkyl is more preferably trifluoromethyl, trichloromethyl, 2,2,2-trifluoroethyl, pentafluoroethyl and nonafluorobutyl; C1-C8-fluoroalkyl is more preferably trifluoromethyl, 2,2,2-trifluoroethyl, pentafluoroethyl and nonafluorobutyl.
Preferred compounds of the formula (I) are defined below.
Very particularly preferred compounds of the formula (1) are: (1R, 2R)-1-diphenylphosphino-2-(1S-diphenylphosphinoethyl)cyclopentane, (1R, 2R)-1-diphenylphosphino-2-(1S-diphenylphosphino-2-methylpropyl)cyclopentane and (1R,2R)-1-diphenylphosphino-2-(S-diphenylphosphinocyclohexylmethyl)cyclopentane.
The invention also embraces complexes of compounds of the formula (I) with boranes, for example borane or borabicyclononane (BBN-9).
In the context of the invention, the terms stereoisomerically enriched and enantiomerically enriched include stereoisomerically pure and enantiomerically pure compounds and mixtures of stereoisomeric and enantiomeric compounds in which one stereoisomer or enantiomer is present in a greater relative proportion than the other stereoisomer(s) or enantiomer(s), preferably in a relative proportion of above 50 to 100 mol %, more preferably 90 to 100 mol % and even more preferably 98 to 100 mol %.
The compounds of the formula (I) can be prepared by a process which is likewise in accordance with the invention.
This process is characterized in that
In the formulae (II), (IV), (V), (VI), (VII), (IX) and (X) *1, *2 and *3, R1, R2, R3, R4, R5 and R6 each have the same definitions and areas of preference as have already been described under the formula (I).
Moreover, R7 in the formulae (VIII) and (IX) is alkyl, fluoroalkyl, arylalkyl or aryl, preferably alkyl and fluoroalkyl.
In the formulae (III) and (VIII), Hal is in each case chlorine, bromine or iodine, preferably chlorine.
The compounds of the formulae (II), (IV), (V), (VI), (VII) and (IX) are hitherto unknown and therefore likewise embraced by the invention as indispensable intermediates. The definitions and areas of preference specified above for *1, *2 and *3, R1, R2, R3, R4, R5, R6 and R7 each apply in the same manner.
Also embraced by the invention are complexes of compounds of the formula (VII) with boranes, for example borane or borabicyclononane (BBN-9).
The invention further provides processes which comprise the steps below, as have been described above:
The chemical nature of the individual steps is already known in principle and they can be employed in a similar manner to the inventive compounds.
Preferred compounds of the formula (II) are:
A preferred compound of the formula (III) is chlorodiphenylphosphine.
Preferred compounds of the formula (IV) are:
Preferred compounds of the formula (V) are:
Preferred compounds of the formula (VI) are:
Preferred compounds of the formula (VI) are:
Preferred compounds of the formula (IX) are:
A preferred compound of the formula (X) is diphenylphosphine.
In the manner described, the compounds of the formula (I) are obtainable in high yields in an efficient manner.
The invention also embraces transition metal complexes which comprise the inventive compounds of the formula (I).
Transition metal complexes are preferably those of ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum and copper, preferably those of ruthenium, rhodium, iridium, nickel, palladium and platinum, more preferably those of ruthenium, rhodium, iridium and palladium.
The inventive transition metal complexes are especially suitable as catalysts. The invention therefore also embraces catalysts which comprise the inventive transition metal complexes.
The catalysts used may, for example, either be isolated transition metal complexes or be those transition metal complexes which are obtainable by reacting transition metal compounds and compounds of the formula (I).
Isolated transition metal complexes which contain the compounds of the formula (I) are preferably those in which the ratio of transition metal to compound of the formula (I) is 1:1.
Preference is given to the inventive compounds of the formula (XI)
[(I)L12M][An1] (XI)
in which (I) represents compounds of the formula (I) with the definition specified there and its areas of preference and
Preferred transition metal complexes are those which are obtainable by reacting transition metal compounds and compounds of the formula (I)
Suitable transition metal compounds are, for example, those of the formula
M(An2)q (XIIa)
in which
Additionally suitable as transition metal compounds are, for example, Ni(1,5-cyclooctadiene)2, Pd2(dibenzylideneacetone)3, Pd[PPh3]4, cyclopentadienyl2Ru, Rh(acac)(CO)2, Ir(pyridine)2(1,5-cyclooctadiene), Cu(phenyl)Br, Cu(phenyl)Cl, Cu(phenyl)I, Cu(PPh3)2Br, [Cu(CH3CN)4]BF4 and [Cu(CH3CN)4]PF6 or polynuclear bridged complexes, for example [Rh(1,5-cyclooctadiene)Cl]2, [Rh(1,5-cyclooctadiene)Br]2, [Rh(ethene)2Cl]2, [Rh(cyclooctene)2Cl]2.
The transition metal compounds used are preferably:
[Rh(cod)(acac)] where acac is acetylacetonate, [Ir(ethylene)2(acac)], [Rh(ethylene)2(acac)], [Rh(cod)Cl]2, [Rh(cod)Br]2, [Rh(cod)2]ClO4, [Rh(cod)2]BF4, [Rh(cod)2]PF4, [Rh(cod)2]ClO6, [Rh(cod)2]OTf, [Rh(cod)2]BAr4 (Ar=3,5-bistrifluoromethylphenyl), [Rh(cod)2]SbF6, RuCl2(cod), [(cymene)RuCl2]2, [(benzene)RuCl2]2, [(mesityl)RuCl2]2, [(cymene)RuBr2]2, [(cymene)Rul2]2, [(cymene)Ru(BF4)2]2, [(cymene)Ru(PF6)2]2, [(cymene)Ru(BAr4)2]2 (Ar=3,5-bistrifluoromethylphenyl), [(cymene)Ru(SbF6)2]2, [Ir(cod)Cl]2, [Ir(cod)2]PF6, [Ir(cod)2]ClO4, [Ir(cod)2]SbF6, [Ir(cod)2]BF4, [Ir(cod)2]OTf, [Ir(cod)2]BAr4 (Ar=3,5-bistrifluoromethylphenyl), RuCl3, NiCl3, RhCl3, PdCl2, PdBr2, Pd(OAc)2, Pd2(dibenzylideneacetone)3, Pd(acetylacetonate)2, CuOTf, CuI, CuCl, Cu(OTf)2, CuBr, CuI, CuBr2, CuCl2, CuI2, [Rh(nbd)Cl]2, [Rh(nbd)Br]2, [Rh(nbd)2]ClO4, [Rh(nbd)2]BF4, [Rh(nbd)2]PF6, [Rh(nbd)2]OTf, [Rh(nbd)2]BAr4 (Ar=3,5-bistrifluoromethylphenyl), [Rh(nbd)2]SbF6, RuCl2(nbd), [Ir(nbd)2]PF6, [Ir(nbd)2]ClO4, [Ir(nbd)2]SbF6, [Ir(nbd)2]BF4, [Ir(nbd)2]OTf, [Ir(nbd)2]BAr4 (Ar=3,5-bistrifluoromethylphenyl), Ir(pyridine)2(nbd), [Ru(DMSO)4Cl2], [Ru(CH3CN)4Cl2], [Ru(PhCN)4Cl2], [Ru(cod)Cl2]n, [Ru(cod)4(methallyl)2], [Ru(acetylacetonate)3].
The amount of the transition metal compounds used may, for example, be 25 to 200 mol % based on the compound of the formula (D used; preference is given to 50 to 150 mol %, very particular preference to 75 to 125 mol % and even greater preference to 100 to 125 mol %.
The catalysts which comprise the inventive transition metal complexes are especially suitable for use in a process for preparing stereoisomerically enriched, preferably enantiomerically enriched, compounds.
Preference is given to using the catalysts for asymmetric 1,4-additions, asymmetric hydroformylations, asymmetric allylic substitutions, asymmetric hydrocyanations, asymmetric Heck reactions, asymmetric hydroborations and asymmetric hydrogenations, more preferably for asymmetric hydrogenations, asymmetric 1,4-additions, asymmetric hydroborations and asymmetric allylic substitutions.
Preferred asymmetric hydrogenations are, for example, hydrogenations of prochirals C═C bonds, for example of prochiral enamines, enamides, olefins, enol ethers, C═O bonds, for example of prochiral ketones, and C═N bonds, for example of prochiral imines. Particularly preferred asymmetric hydrogenations are hydrogenations of prochiral C═C bonds, for example of prochiral enamines and enamides, olefins.
The invention therefore also embraces a process for preparing stereoisomerically enriched, preferably enantiomerically enriched, compounds by catalytic hydrogenating olefins, enamines, enamides, imines or ketones, which is characterized in that the catalysts used are those which comprise transition metal complexes of compounds of the formula (I) with the definitions specified there.
The amount of the transition metal compound used or of the transition metal complex used may, for example, be 0.001 to 5 mol %, based on the substrate used; preference is given to from 0.001 to 0.5 mol %, very particular preference to 0.001 to 0.1 mol % and even greater preference to 0.001 to 0.008 mol %.
In a preferred embodiment, asymmetric hydrogenations, 1,4-additions and hydroborations may be carried out, for example, in such a way that the catalyst is obtained from a transition metal compound and compound of the formula (1), optionally in a suitable solvent, the substrate is added and the reaction mixture is admixed with the reactant at reaction temperature (hydrogen, boronic acids, boranes, etc.).
Suitable solvents for the asymmetric catalysis are, for example, chlorinated alkanes such as methyl chloride, short-chain C1-C6-alcohols, e.g. methanol, isopropanol or ethanol, aromatic hydrocarbons, e.g. toluene or benzene, ketones, e.g. acetone, or carboxylic esters, e.g. ethyl acetate.
The asymmetric catalysis is carried out advantageously at a temperature of −20° C. to 200° C., preferably 0 to 1001C and more preferably at 20° to 70° C.
The inventive catalysts are especially suitable in a process for preparing stereoisomerically enriched, preferably enantiomerically enriched, active ingredients in medicaments and agrochemicals, or intermediates of these two classes.
The advantage of the present invention is that the compounds of the formula (I) can be prepared in an efficient manner, and their electronic and steric properties are variable to a wide degree starting from readily available reactants. In addition, the inventive ligands and their transition metal complexes show good performance in asymmetric syntheses.
General Procedure 1 for the Synthesis of 2-alkylidenecyclopentanones
A 2 l Erlenmeyer flask was charged with 1 l of H2O, 15 g of KOH, 100 ml of MTBE and 30 ml of cyclopentanone. A solution of 0.3 mol of the particular aldehyde in 50 ml of MTBE was introduced dropwise at room temperature into the vigorously stirred mixture within 2 h. The reaction mixture was stirred for a further 30 min and then neutralized with conc. HCl. The organic phase was removed and the solvent was removed under reduced pressure. The residue was distilled fractionally with a 40 cm Vigreux column under reduced pressure. The typical yield range is 18 to 45%.
General Procedure 2 for the reduction of 2-alkylidenecyclopentanones to the corresponding alcohols
In a 500 ml round-bottomed flask, 36 g of CeCl3.7H2O were dissolved in 210 ml of methanol. 150 mM of the ketone were added, the mixture was cooled to 0° C. and 4.0 g of solid NaBH4 were subsequently added in small portions in such a way that the temperature did not rise above 5° C. The reaction mixture was stirred for a further 15 min and then added to 250 g of ice. The reaction mixture was allowed to warm to room temperature with stirring, the upper phase was removed and the aqueous phase was extracted three times with 100 ml each time of diethyl ether. The combined organic phases were washed with 50 ml of H2O and 50 ml of saturated sodium chloride solution, and dried over magnesium sulphate, and the solvent was removed under reduced pressure. The residue was fractionally distilled with a 40 cm Vigreux column under reduced pressure. Typical yield range: 93 to 96%.
General Procedure 3 for the Enzymatic Kinetic Optical Resolution of 2-alkylidene-cyclopentanols
100 mM of the particular alcohol were dissolved in 200 ml of hexane, then 20 ml of vinyl acetate and 0.80 g of Amano PS lipase (Pseudomonas cepacia, Aldrich) were added. The reaction mixture was stirred at 44 to 45° C. (internal temperature) for 6 to 8 h (GC monitoring), and then filtered through celite, and the solvent was removed under reduced pressure. The products were separated by means of chromatography (silica gel, 3:1 pentane-ether). The enantiomeric excess was determined on a chiral GC column (TFA-cyclodextrin column). The ee value was typically 99%, both for the alcohols and for the acetates. Typical yield range: 47 to 48%.
General Procedure 4 for the Allyl Phosphinite-Allylphosphine Oxide Rearrangement
12 mM of the chiral allyl alcohol were dissolved in 50 ml of anhydrous toluene under an argon atmosphere. 1.50 g of 4-dimethylaminopyridine (Acros) were added. The mixture was cooled to −30° C. and 2.2 ml of freshly distilled Ph2PCl (Strem) were added slowly at this temperature. The mixture was allowed to warm to room temperature and then heated to 80° C. for 6 h (monitoring with 31P NMR). The reaction mixture was cooled to room temperature and filtered through a 2 cm silica gel layer, and the filtercake was washed repeatedly with toluene. The solvent of the filtrate was removed under reduced pressure. The residue was recrystallized from heptane/CH2Cl2. Typical yield range: 70 to 77%.
General Procedure 5 for the Synthesis of Diphenylphosphinoyl Alcohols from Allylphosphine Oxides.
4 mM of the allylphosphine oxide were introduced under an argon atmosphere into a 20 ml glass autoclave (Ace®, Aldrich) and dissolved in 12 ml of a 0.5 M solution of 9-BBN in THF (Aldrich). The solution was heated to 75° C. for 48 h and then cooled to room temperature.
In a 250 ml flask, 6.0 g of m-chloroperbenzoic acid (70-75%, Acros) were dissolved in 40 ml of CH2Cl2. The solution was dried over MgSO4 for 5 min and then filtered. The flask was immersed in an acetone/dry ice bath and the solution of the borane adduct (see above) was added dropwise in such a way that the internal temperature was 10 to 15° C. After the end of the addition, the reaction mixture was stirred for a further 30 min and washed twice with 50 ml each time of 20% eq. Na2S2O5, and twice with 30 ml each time of 2 N NaOH and saturated sodium chloride solution. The filtrate was dried over magnesium sulphate and the solvent was removed under reduced pressure. 25 ml of diethyl ether were added to the residue and the mixture was stirred at room temperature for 12 h. The white precipitate was filtered off, washed with diethyl ether and dried under reduced pressure. Typical yield range: 55 to 67%.
General Procedure 6 for the Conversion of Diphenylphosphine Oxides to Diphenylphosphine-Borane Complexes
Under an argon atmosphere, a dry Schlenk vessel was charged with 5 mM of the particular phosphine oxide, 20 ml of anhydrous toluene, 2 ml of polymethylhydrosiloxane (Aldrich) and 1.5 ml of titanium isopropoxide (Acros). A sample of the reaction mixture was transferred into an NMR tube in order to monitor the reaction. The reaction mixture and the NMR tube were heated to 105° C. for 2 to 4 h until full reduction was observed in the 31p NMR (oxide signals at 30 to 40 ppm, phosphines −20 to 0 ppm). The reaction mixture was cooled to room temperature and 1 ml of borane-dimethyl sulphide complex (Aldrich) was added. After 5 minutes, the reaction mixture was introduced cautiously into a 250 ml Erlenmeyer flask with 5 ml of methanol (H2 evolution!). After the gas evolution had abated, the solution was transferred into a 250 ml Nalgene®) bottle with 20 ml of 48% HF and 20 ml of H2O, and then stirred at room temperature for 12 h. The organic phase was removed and the aqueous phase was extracted with 15 ml of toluene. The combined organic phases were washed with saturated NaHCO3 solution and saturated sodium chloride solution, and dried over magnesium sulphate, and the solvent was removed under reduced pressure. The residue was taken up in 5 ml of diethyl ether and filtered through a 3 cm silica gel layer. The filter residue was washed with 5 ml of diethyl ether and the solvent of the filtrate was removed under reduced pressure. The residue was dried under high vacuum and the phosphine-borane complex was obtained as a viscous oil which solidified in the course of standing. Typical yield range: 94 to 96%.
General Procedure 7 for the Conversion of Phosphine-Borane Alcohols to the Corresponding Mesylates and the Substitution Thereof with Diphenylphosphine.
Under an argon atmosphere, a 100 ml dry Schlenk vessel was charged with 5 mM of a phosphine-borane alcohol and 40 ml of dry dichloromethane. The mixture was cooled to −30° C. and 2.4 ml of anhydrous triethylamine were added.
1.2 ml of methanesulphonyl chloride were then added dropwise at this temperature with vigorous stirring. The reaction mixture was left at −30° C. for 2 h and was introduced at this temperature with stirring into 200 ml of anhydrous diethyl ether. After 5 min, the white precipitate was filtered off through a 3 cm silica gel layer. The filtercake was washed with 100 ml of diethyl ether and the solvent was removed under reduced pressure down to a residue of 10 ml. The remaining solvent was removed under high vacuum in order to prevent thermal stress. The remaining residue was left under high vacuum for 5 h in order to remove traces of MsCl. The thus obtained mesylate was used in the next step without further purification.
In a 100 ml Schlenk vessel under an argon atmosphere, 2.00 g of t-BuOK in 25 ml of anhydrous THF and 2.32 g (3 equivalents) of diphenylphosphine (Strem) were combined. The orange-coloured solution was cooled to −20° C. and the above-described mesylate in 10 ml of THF was added slowly. The reaction mixture was allowed to warm to room temperature and then heated to 50° C. for 18 h. After cooling to room temperature, 2.5 ml of borane-dimethyl sulphide complex (Aldrich) were added. The contents of the reaction vessel were introduced cautiously into a 250 ml Erlenmeyer flask with 10 ml of methanol. After the gas evolution had abated, 50 ml of saturated NH4Cl solution were added, the organic phase was removed and the aqueous phase was extracted twice with 20 ml each time of dichloromethane. The combined organic phases were washed with saturated sodium chloride solution and dried over magnesium sulphate, and the solvent was removed under reduced pressure. The residue was dissolved in 5 ml of dichloromethane-pentane (1:1) and filtered through a 5 cm aluminium oxide layer on a 25 mm (diameter) filter. The majority of the solvent was removed under reduced pressure and the residue was diluted with 15 ml of diethyl ether and left at 0° C. for 12 h. The solid formed was filtered off and dried under reduced pressure. Typical yield range 52 to 54%.
General Procedure 8 for the Deprotection of a Phosphine-Borane with N,N′-bis(3-aminopropyl)piperazine
Phosphine-borane (1 mM) was introduced under an argon atmosphere into a 10 ml Schlenk vessel and dissolved in 2 ml of anhydrous toluene. 1 ml of N,N′-bis-(3-aminopropyl)piperazine (Lancaster) was added to this solution. The reaction mixture was heated to 105° C. for 2 h, cooled to room temperature and diluted with 10 ml of diethyl ether. Under an argon atmosphere, the mixture was filtered through diethyl ether-moistened silica gel into a flask (very strict oxygen exclusion). The silica gel was rewashed twice with 30 ml each time of diethyl ether. The solvent was removed under reduced pressure. The resulting phosphine is obtained as a white foam or highly viscous oil which solidifies. The product was stored under an argon atmosphere. Typical yield range: 99 to 100%.
Synthesized according to General Procedure 1 using acetaldehyde. Yield 18%, b.p. 60-65° C. (10 mbar)
Synthesized from 1a according to General Procedures 2 and 3. Yields: 93% and 47% (44% overall), b.p. 82-83° C. (10 mbar).
Synthesized from 1b) according to General Procedure 4. Yield 70%.
Synthesized from 1c) according to General Procedure 5. Yield 67%.
Synthesized from 1d) according to General Procedure 6. Yield 94%.
Synthesized from 1e) according to General Procedure 7. Yield 54%.
1 g) {(1S)-1(R)-[(2R)-2-(Diphenylphosphino)cyclopentyl] ethyl} (diphenyl)phosphine
Synthesized from 1f) according to General Procedure 8. Yield 97%.
Synthesized according to General Procedure 1 using isobutyraldehyde. Yield 45%, b.p. 88-90° C. (10 mbar)
Synthesized from 2a) according to General Procedures 2 and 3. Yields 95% and 48% (46% overall), b.p. 95-98° C. (10 mbar).
Synthesized from 2c) according to General Procedure 5. Yield 65%.
Synthesized from 2d) according to General Procedure 6. Yield 96%.
Synthesized from 2e) according to General Procedure 7. Yield 52%.
Synthesized from 2f) according to General Procedure 8. Yield 98%.
Synthesized according to General Procedure 1 using cyclohexane carbaldehyde. Yield 36%, b.p. 91-95° C. (0.5 mbar).
Synthesized from 3a) according to General Procedures 2 and 3. Yields 96% and 48% (46% overall), b.p. 100-103° C. (10 mbar).
Synthesized from 3b) according to General Procedure 4. Yield 76%.
Synthesized from 3c) according to General Procedure 5. Yield 55%.
Synthesized from 3d) according to General Procedure 6. Yield 96%.
Synthesized from 3e) according to General Procedure 7. Yield 52%.
Synthesized from 3′) according to General Procedure 8. Yield 94%.
For the examples below, the ligands of the formula (I) are used and are abbreviated as follows:
Rhodium-catalysed asymmetric 1,4-addition of phenylboronic acids to 2-cyclohexenone
General procedure for the Rh-catalysed asymmetric 1,4-addition of phenylboronic acid to 2-cyclohexenone
Under an argon atmosphere, Rh(acac)(cod) (3.7 mg, 12 μmol), the chiral diphosphine (12 μmol), PhB(OH)2 (244 mg, 2 mmol), anhydrous dioxane (2 ml) and 2-cyclohexenone (0.04 ml, 0.4 mmol) were introduced into a Schlenk vessel. The mixture was stirred at room temperature for 15 min and H2O (0.1 ml) was added. The reaction mixture was stirred at 100° C. for 3 h. Water (5 ml) was added and the mixture was extracted twice with 5 ml each time of diethyl ether. The combined organic phases were washed with 5 ml of saturated sodium chloride solution and dried over magnesium sulphate, and the solvent was removed under reduced pressure. Purification by flash chromatography (25% Et2O in pentane) gave (R)-3-phenylcyclohexanone (68.2 mg, 98%) with 88% ee as a colourless oil.
HPLC (Chiralcel OD-H, n-heptane/1-PrOH 99/2, 0.3 ml/min, 215 nm): tr/min=44.0 (S), 47.0 (R).
1H NMR (300 MHz, CDCl3): δ 7.30-7.20 (m, 5H), 3.01 (m, 1H), 2.60-2.30 (m, 4H), 2.10-2.00 (m, 2H), 1.89-1.70 (m, 2H) ppm.
13C NMR (75 MHz, CDCl3): δ 211.0, 144.3, 128.6, 126.6, 126.5, 48.9, 44.7, 41.1, 32.7, 25.5 ppm.
Rhodium-catalysed asymmetric hydroboration of styrene
General procedure for the Rh-catalysed hydroboration of styrene with catecholborane
A mixture of [Rh(cod2)]BF4 (8.1 mg, 0.020 mmol, 1 mol %) and the chiral diphosphine (0.020=mol, 1 mol % in Et2O) in dry THF (2 ml) was stirred at room temperature for 10 min in a 10 ml Schlenk vessel under an argon atmosphere. Styrene (2 mmol, 0.23 ml) was added to the orange-coloured solution. The homogeneous reaction mixture was cooled to −20° C. and stirred at this temperature for 15 min before freshly distilled catecholborane (2.4 mmol, 0.26 ml) was added. The reaction mixture was stirred at −10° C. for 16 h and then quenched by adding EtOH (2 ml). Aqueous NaOH (2 M, 2 ml) and 30% H2O2 were added successively and the reaction mixture was warmed to room temperature with vigorous stirring over 2 h. The mixture was then extracted twice with 5 ml each time of Et2O. The combined organic phases were washed with in each case 2 ml of NaOH (1 M) and saturated sodium chloride solution, and dried over magnesium sulphate. The residue was purified by means of flash chromatography (20% Et2O in pentane). In this way, (R)-phenylethanol (72%, 176 mg) was obtained as a colourless liquid with 80% ee.
HPLC (Chiralcel OD-H, n-heptane/i-PrOH 98/2, 0.4 ml/min, 215 nm): trimin=35.5 (R), 43.7 (S).
1H NMR (300 MHz, CDCl3): δ 7.20-7.09 (m, 5H), 4.66 (q, J=6.5 Hz, 1H), 2.80 (br 1.30 (d, J=6.5 Hz, 3H) ppm.
13C NMR (75 MHz, CDCl3): δ 146.4, 128.8, 127.7, 125.9, 70.6, 25.6 ppm.
Rhodium-catalysed asymmetric hydrogenation of methyl (Z)-α-acetamidocinnamate
Rhodium-catalysed asymmetric hydrogenation of acetophenone-phenylcarbonylhydrazone
Ruthenium-catalysed asymmetric hydrogenation of ethyl 3-phenyl-3-oxopropanoate
Palladium-catalysed asymmetric allylic substitution of 1,3-diphenylallyl acetate with methyl malonate
| Number | Date | Country | Kind |
|---|---|---|---|
| 1020040229007 | May 2004 | DE | national |
