FIELD OF THE INVENTION

The present invention relates to a process of production of the herbicide (S) -metoiachior comprising a step of hydrogenation of N- [2' -methyl-6' -ethyl-phenyl) -N- {1-methoxymethyl) ethyl imine to (S) -N- (2' -methyl-6' -ethyl- phenyl ) -N- (l-methoxylmethyl) ethylainine in the presence of an iridium complex and a phos ^' phine-phosphoramidite ligand.

BACKGROUND OF THE INVENTION

The synthesis of (S) -metoiachior is described by the following sequence of reactions:

(SHnet iac iar

The key step in this synthesis is the asymmetr.i hydrogenation of N- (2' -methyl-6' -ethyl-phenyl ) -N- { 1 methoxymethyl ) ethyl imine (I) to (S) -N~ (2' -methyl-6' -ethyl phenyl ) -N- ( 1-methoxylmethyl ) ethyiamine (II) :

(!)

(li)

The first successful catalyst for this transformation was disclosed in patent application W095/21151. The catalyst has the general formula [XlrYZ] , wherein:

- Y is a ferrocenyl -diphosphine ligand of the formula

(III), also kno

(III)

wherein:

- Ph is phenyl,

- X is a diene ligand, more specifically 1, 5-cyclooctadiene (COD), and

- Z is a halogen, more specifically chlorine.

The reaction can be carried out with or without an inert solvent, and the reaction mixture contained an ammonium chloride, bromide or iodide and additionally an acid. The asymmetric hydrogenation of (I) was described in detail in example 1: the reaction was carried out at a temperature of 50 °C and at a H? pressure of 80 bar, in the presence of tetrabutylammonium iodide and acetic acid, without any other solvent; the molar ratio between the ligand and the substrate (I) was 0.Q135 mmol : 1 mol ( Imol of ligand : 74000 mol of substrate) . After 18 hours, the conversion was 97% and the optical yield

75.6% (S-isoraer) .

Patent US652521Q discloses a chiral ligand binaphtyl motif connected b a ferrocene backbone ⁽ IV)

The patent description further provides a general process for the hydrogenat ion of imin s: the reaction was carried out in diehloromethane, at room temperature and a hydrogen pressure of 68 bar and the ligand to substrate ratio was 0.044 irarsoi : 1 moI (1 mol of ligand : 22700 mol of substrate) . An enantiomeric excess of 80% of the (S) -isomer (II) was obtained when the above conditions were used for the hydrogenat ion of (I) .

Patent application WO2010Q94164 discloses a ligand with the general formula (V) :

The asymmetric hydrogenation of (I) was carried out using a ligand (V) wherein R ¹ -, R ² and R ⁵ are H, R ³ is CH _¾ and R< is N (CH3> 2, and the reaction was carried out in tetrahydrofuran, at 50 °C and a hydrogen pressure of 80 bar, in the presence of 2, 3, 4 , 5, 6-pentafluorobenzyl bromide, at a molar ratio of ligand : substrate of 0.012 mmol : 1 mol (1 raol of ligand : 83000 mol of substrate) . After 7 hours, the conversion was >99 and an enantiomeric excess of 78% (S-isomer) was obtained.

Patent application CN101857612 discloses a ligand with the general formula (VI) :

wherein Ph is phenyl and R is methyl (Via) or terfc-butyl (VIb . When (Via) was used at a molar ratio of metal to ligand of 1:1 and a substrate to metal ratio of 100000:1, after 10 hours the conversion was 98% and the enantiomeric excess was 83%; when the substrate to metal ratio was increased to 200000:1 it took 15 hours to achieve a conversion of 98%, but the enantiomeric excess decreased to 80%. Replacing ligand (Via) by (VIb), a conversion of 98% and an enantiomeric excess of 86.5% were obtained at a substrate to metal ratio of only 50000:1 and after 26 hours. When the reaction temperature was increased from 40 °C to 115 ° _t the time required to achieve the same conversion was 15 hours but the enantiomeric excess was reduced to 80%.

Patent application O20121I6493 discloses a ehiral ligand with the general formula (VII) :

(VII)

The asymmetric hydrogenation of (1) was carried out. using a ligand (VII) wherein R ¹ , R ² , R ³ and R ⁴ are H and X is phenyl, at a temperature of 50 °C and at a ¾ pressure of 80 bar, in the presence of tetrabutylarranonium iodide and dichloroethane as the solvent. No acid was required and the molar ratio between the ligand and the substrate was 0.0083 mmol : 1 mol (1 mol ligand: 120000 mol substrate) . After 18 hours, the conversion was 97% and the optical. yield 93.5% (S) . No information about the enantiomeric excess is provided.

Hu, Xiang-Ping et al . _f Organic letters, 2012, Vol.14 _f Nol3, 3554-3557, reported that ligand (VII) was used for the asymmetric hydrogenation of compound (I) . The hydrogenation was performed at 100 °C for 18 hours at a ¾ pressure of 80 bar with Bi NI as the additive, employing a substrate to catalyst loading of 100000:1. The conversion was complete and the enantiomeric excess was 80%.

Novel phosphine-phosphoramidite compounds with the formula (Villa) or (VI I lb) were disclosed in WO2006012045A1:

(Villa) (VHIb)

Especially preferred were the compounds wherein R is aryl, most preferably phenyl, R ¹ is aryl, most preferably phenyl, 4-methoxyphenyl , or 4-trifluoromethylphenyl; R ² is aryl, most preferably phenyl, 4-methoxyphenyl, or

4-trifluoromethylphenyl, or P. ¹ and R ² are collectively 1 , 2-et.hanediyl , 1 , 3-propanediyi, 1 , 2-ben2enediyl , 2,2'- biphenyldiyl, racemic 1 , 1 ' -binaphthyl-2 , 2 ' -diyl , (R,R) - 1,1 ^» -binaphthyl-2, 2 ' -diyl, or { S, S ) -1 , 1 ' -binaphthyl-2 , 2 ' - diyl; R ³ is hydrogen, Ci-Ce alkyl, or aryl, most preferably methyl; R' ^! is hydrogen or C_-Ce alkyl, most preferably methyl; R ^Cj and R ⁶ are hydrogen; n is 0; m is 0; and M is iron. The patent application shows the use of this ligand with a catalyticaliy-active metal selected from rhodium, iridium, or ruthenium, preferably ruthenium, for the asymmetric hydrogenation of an enamide of the general formula (IX) to the corresponding amino acid derivative (X) :

(!X) <X) However, no reference or suggestion is made to the use of the above ligand for the catalytic asymmetric hydrogenation of compound (I) .

Hu, Xiang-Ping et al . , Organic Letters, 2004, Vol.6, No20, 3585-3588, also reported that ligand {XI}

(S _c ,R _p ,S)- (XI) was used for the rhodium catalyzed asymmetric hydrogenation of enamides of general formula (XII)

R= H, F, CI, Br, CF ₃ {XII) ,

and also of dimethyl Itaconate and methyl (2} -acetamidocinnamate , In all cases the ligand was complexed with Rh (COD) 2BF4.

No reference is made to the combination of this ligand with Iridium catalysts or to the asymmetric hydrogenation of compound (I) . DETAILED DESCRIPTION OF THE INVENTION

The object of the invention is a process for the production of ( S) -metolachlo-r comprising a step of asymmetric hydrogenation of N- (.2' -methyl-6' -ethyi-pheny1 ) - N- { 1-m.ethox.ymethyl ) ethylimine (I ) to ( S) ~N~ (2' -methyl-6' - eth l-phenyl) -N- ( 1-methoxylmethyl } ethylamine (II ) having the following characteristics:

High conversion;

High selectivity, measured by the enantiomeric excess of the S-isomer;

Low catalyst to substrate ratio;

Acceptable reaction time. Surprisingly, it was found that when N~ {2' -methyl—6' - ethyi-phenyl ) -N~ { 1-methoxylmethyi ) ethylimine (I) contacts with hydrogen in the presence of;

-a coordinatio compound formed by a ligand having the structural formula (XIII)

wherein :

R ¹ is phenyl or 3, 5-dimethylphenyl ;

R is hydrogen or methyl, and

R ² and R ⁴ collectively represent, a divalent radical connecting the two phosphoramidite oxygen atoms selected from the group consisting of (R, R) -1 , I' - binaphthyl-2, 2' -diyl, (S, S) -1,1' -binaphthy.I-2, 2' - diyl, 3,.3 ' , 5, 5 ' -tetramethyl-l, 1' -biphenyI-2 , 2 ' - diyl, 3, 3' , 5, 5 ' -tetra-tert-butyi-1, 1' -biphenyl- 2,2' -diyl and ( R, R ) -5 , 5 ' , 6 , 6 ' , 7 , 7 ' , 8 , 8 ' -octahydro- 1,1' -binaphthyl-2, 2 ' -diyl ,

and a di iridium complex of the formula [IrXCl j 2, wherein X is 1 , 5-cyclooctadiene (COD), at a molar ratio of iigand : Iridium in the range of 1:2 to

-an additive selected from iodine or an alkaline metal salt thereof; and

-an aprotic solvent,

at a temperature in the range of 20 °C to 90 °C and a hydrogen pressure in the range of 5 to 80 bar, a conversion to ( S) ~N~ (2' -methy1-6' -ethyl-phenyl } ~N- { 1-methoxylmethyl } ethylamine (II) greater than 95% and an enantiomeric excess of the S-isomer greater than 81% are obtained.

A preferred group of ligands is presented in table I.

Table I

No Name Structure

XIV R) -N- [ (R) , (R) -1,1' -binaphthyl-2, 2 ' - dioxyphosphino] - -methyl-l- [ (S) -2-

Fe PPh ₂

{diphenylphosphi.no) ferrocenyl] ethylareine V-Q.

XV ( J ) -N- [IS) , (S) -1,1' -binaphthyl-2, 2 ' - dioxyphosphino] -W-methyl-1- [ {S) -2- {diphen Iphosphino) ferrocenyl] ethylamine o Name Structure

XVI {R)-N-[ (5) , (S)-l, l'-binaphthyl-2,2'- /

dioxyphosphi.no] -1- [ (S) -2- (diphenylphosphino) ferrocenyl ] ethylamine

XVII ( R ⁾ -N- [ (R) , ( i¾) - 5, 5' ,6, 6' ,7, 7', 8,8'- octahydro-1 , 1 ' -binaphthyI-2 , 2 ' - dioxyphosphino] -W-methyl-1 - [ (S) -2- (diphenylphosphino) ferrocenyl] ethylamine

XVIII (i?) -W- [ (, ) , (R) -5, 5 ' , 6, 6 ' , 7, 7 ' , 8, 8 · - o tahydro-l , 1 ' -binaphthyl-2 , 2 ' - e PPh ₂

dioxyphosphino] -1- [ {3) -2- V-0 (diphenylphosphino) ferrocenyl ] ethylamine

XIX (R) -N- [3, 3' , 5, 5 ' -tetrame.thyl-1, 1' - biphenyl-2 , 2 ' -dioxyphosphino] -N-methyl-l - [ (S) -2- (diphenylphosphino) ferrocenyl] Fe PP^ V-0 / ethylamine

XX {R) -N- [3, 3 ',5,5' -tetra-tert-butyl-l, 1' - biphenyl-2, 2' -dioxyphosphino] -W-methyl-l- [ (5) -2- (diphenylphosphino) ferrocenyl]

ethylamine No Name Structure

XXI ί R) -N- { {P.) , (R) -1, 1 ' -binaphthy.1-2, 2 ' -- dioxyphosphino] -W-inethyl-1- [ !5) -2- (bis (3, 5-dimethyIpheny 1 ) pho.sphino) Fe PXy V-o ferrocenyl ] ethyiamine

XXII (R) -W-[ (R) , (J?) -5, 5' ,6, 6' , 7,7' , 8, 8'- octahydro-1, 1 ' -binaphthyl- , 2 ' - dioxyphosphino] -N-methyl-l- [ (S) ~2~

(bis (3, 5-d imeth lpheny1 ) hosphino)

ferrocenyl ] ethyiamine

Particularly preferred are the ligands (XVil) or (XVIII) . The molar ratio between the ligand (L) and the metal

(Ir) is in the range of 2:1 to 1:2 (L:Ir) . A molar ratio of 1.1:1 (L:Ir) is particularly preferred.

The molar ratio between the ligand and the imine (I) is in the range of 100:1 to 300000:1, preferably from 100000:1 to 250000:1, most preferably from 200000:1 to 250000:1.

The reaction is carried out in the presence of an aprotic solvent, selected from the group consisting of dichloromethane, toluene, xylene and n-heptane, preferably toluene .

The ratio between the solvent and the iraine (I) is in the range of 1:2 (volume : weight ) to 150:1 (volume : weight } , preferably 1:1 (volume : weight. ) to 4:1 (volume : weight. ) , most preferably 1:1 (volume: weight) .

The additive is iodine or an alkaline metal salt thereof selected from the group consisting of Lil, Na l and KI, preferably iodine or Lil.

The molar ratio between the additive and the imine (I) is in the range of 0.00125:1 to 0.05:1, preferably 0.0025:1 to 0.005:1.

The reaction temperature is in the range of 20 °C to 90 °C, preferably in the range of 50 °C to 70 ^,;j C, most preferably 70 °G .

The hydrogen pressure is in the range of 5 to 80 bar, preferably in the range of 20 to 80 bar, most, preferably 30 bar. Examples

The following embodiments illustrate the process according to the invention. In the following examples, the conversion is calculated using the results of the H ^' PLC analysis of the reaction product and equation (I):

% conversion = (AS+AR) / ( AS ^■ ( ^■ AR-fAI†A ) *100 ( I ) wherein : AS- HPLC area of the peak corresponding to the isomer of the amine (II)

AP~ HPLC area of the peak corresponding to the isomer of the amine (II)

AI- HPLC area of the peak corresponding to the

(I)

AA - HPLC area of the peak corresponding to an (precursor of the imine (I)) . The enantiomeric excess is the difference between the area percentages of the (S) and (R) isomers of the amine

In the following examples, unless specifically indicated, the ratios are per mol .

Example 1

A reaction vial is charged with ligand, [IrCODCl]? (ligand: Ir ratio of 1:1) and the solvent (0.1 ml) and stirred under nitrogen for 30 minutes. To the vial is added a solution of the imine (I) (0.1 mmol) in the solvent (0.1 ml) and a solution of the additive (0.005 mmol) in the solvent (0.1 ml) . The Ir: imine ratio is 1:100 and the additive : imine ratio is 0.05:1. The reaction vial is loaded into the hydrogenation equipment, which is purged with nitrogen. The vessel is then purged with ¾ in three cycles (10-20 bar, normal pressure) with stirring (750 rpm) . The hydrogen pressure is set at 20 bar and the reaction is carried out. at 20 °C for 16 h under stirring (750 rpm) . After cooling to room temperature the pressure is released, reaction mass is sampled (-10 μΐ, diluted to 1.5 ml with isopropanol) and analysed by H LC. The following values conversion and enantiomeric excess {% e . e . } were obtained

Table II

Example 2

2.3 mg of ligand (XVIII) and 1 mg of [IrCODCl { ligand :Ir ratio of 1.1:1) were pre-mixed in 0.25 ml of toluene under nitrogen and the mixture was stirred for 15- 20 minutes. 50 μΐ of the previous mixture were fed to a reaction vial containing 32.6 mg Lil (Lil : imine ratio of 0.02:1), _: 2.5 g of imine (I) (Ir limin ratio of 1:20000) and 2.5 ml of toluene (toluene : imine ratio of 1:1 volume : weight } , and the reaction vial was loaded into the hydrogenation equipment, which was purged with nitrogen. The reaction vessel was purged with Ha in five cycles (20- 30 bar, normal pressure) under stirring (650 rpra) . The hydrogen pressure was set as indicated in table III and the mixture heated to 70 °C for 20 hours under stirring (650 rpm) . After cooling to room temperature, the pressure was released, reaction mass was sampled (-10 pi, diluted to 1.5 mi with isopropanoi) and analysed by HPLC, The following values of conversion and enantiomeric excess were obtained :

Table III

Example 3

2.3 rag of ligand {XVIII} and 1 mg of (IirCODClh (ligand:.lr ratio of 1.1:1) were pre-mixed in 1 ml of toluene under nitrogen and the mixture was stirred for 20- 30 minutes. 20 μΐ of the previous mixture were fed to a reaction vial containing 7.7 mg l ₂ (I2: iraine ratio of 0.005:1), 1.25 g of imine {I) (Ir: imine ratio of 1:100000} and 1.25 ml of toluene ( toluene : imine ratio of 1:1 volume : weight ) , and the reaction vial was loaded into the hydrogenation equipment, which was purged with nitrogen. The reaction vessel was purged with ¾ in five cycles (20- 30 bar, normal pressure) under stirring (650 rpm) . The hydrogen pressure was set at 30 bar and the mixture heated to 70 ^» C for 16 hours under stirring {650 rpm} . After- cooling to room temperature, the pressure was released, reaction mass was sampled (-10 μΐ, diluted to 1.5 ml with isopropanoi) and analysed by HPLC, The conversion of the imine ( I ) to (S) ~N~ {2 ^f -methyl~6' -ethyl-phenyl) ~N- {1- methoxylmethyl ) ethylamine (II) was 98.8% and the enantiomeric excess of the (S) -isomer was 88.3%. The estimated reaction time, based on hydrogen uptake data, was 2 hours.

Examples 4 to 6

Using the procedure of example 3, but replacing with Lil, the following values of conversion enantiomeric excess were obtained;

Table IV

Exam les 7 to 9

Using the procedure of examples 4 to 6, but replacing toluene with n-hep ane, m-xylene and o-xylene, the following values of conversion and enantiomeric excess were obtained:

Table V

Example 7 j Example 8 Example 9 n-heptane : imine rat io 1:1 j

( v lume : ie ight )

/s~xyiene: imine ratio I 1:1

( o1ume : eight )

o~xylene : imine ratio —-— i 1:1 ( vo1 ume : eight )

Temperature (°C) 70 I 70 70

Ha Pressure (bar) 30 30 30

Estimated reaction 3.5 3.0 3.5 time (hours)

% conversio 98.6 97.7 97.7

% enantiomeric excess 89.1 88.4 ¹ 88.5 Example 10

As in example 5, but with a Ir; ligand ratio of 2:1. The conversion was 97.0% and the enantiomeric excess 88.8% (S-isomer) . The estimated reaction time, based on hydrogen uptake data, was 15 hours.

Ex mp e 11

2.2 rng of ligand (XVIII) and 1 mg of [IrCODCl]2. (ligand: Ir ratio of 1:1) were pre-mixed in 1 ml of toluene under nitrogen and the mixture was stirred for 30 minutes. 80. μ.Ι of the previous mixture were fed to a reaction vessel containing 16.3 mg Lil (Lil:imine ratio of 0.005:15, 5 g of imine (I) (Ir:imine ratio of 1:100000) and 5 mi of toluene { toluene : imine ratio of 1:1 volume : weight ) , and the reaction vessel was purged with nitrogen. The. reaction vessel was purged with ¾ in three cycles (10-20 bar, normal pressure) under stirring (750 rpm) . The hydrogen pressure was set. at 80 bar and the mixture heated to 60 °C for 20 hours under stirring (750 rpm) . After cooling to room temperature the pressure was released, reaction mass was sampled (~10 μ.1, diluted to 1.5 ml with isopropanol) and analysed by HPLC. The conversion of the imine (I) to S) -N- ( 2 ' -methyl ~6 ^f -ethyl-phenyl) ~N~ ( 1-inethoxylmethyl ) ethylamine (II)· was 98.2% and the enantiomeric excess 88.9% .(S-isomer) . The estimated reaction time, based on hydrogen uptake data, was 16 hours.

Example 12 2.3 mg of ligand (XVIII) and 1 rag of [IrCODCljs (ligand: Ir ratio of 1.1:1} were pre-mixed in 1 ml of toluene under nitrogen and the mixture was stirred for 30 minutes. 10 μΐ of the previous mixture were fed to a reaction vial containing 7.7 mg (Ij limine ratio of

0.005:1), 1.25 g of imine (I) {Ir: imine ratio of 1:200000) and 1.25 ml of toluene { toluene : imine ratio of 1:1 volume : weight ) , and the reaction vial was loaded into the hydrogenation equipment, which was purged with nitrogen. The reaction vessel was purged with ¾ in five cycles (20- 30 bar, normal pressure) under stirring { 650 rp ) . The hydrogen pressure was set at 30 bar and the mixture heated to 70 °C for 16 hours under stirring (650 rpm) . After- cooling to room temperature the pressure was released, reaction mass -was sampled (~10 ui, diluted to 1.5 ml with isopropanol ) and analysed by HPLC. The conversion of the imine ( I ) to ( S) -N- {2' -methyl-6' -ethyl -phenyl ) -N- (1- methoxylmethyi I ethylamine (II) was 97.6% and the enantiomeric excess was 89.0% .(S-isomer) . The estimated reaction time, based on hydrogen uptake data, was 10 hours.

Examples 13 to 15

Using the procedure of example 12 with different additives, the following values of conversion and enantiomeric excess were obtained:

Table VI

Example 13 Example 14 Example 15

Li I : iraine atio 0.005:1 0.005:1

I?:.imine ratio 0.0025:1

Temperature (°C) 70 60 70

¾ Pressure (bar) 30 30 30

Estimated reaction time 5 28 8 (hours )

% conversion 98.0 96.0 98.0

% enantiomeric excess 88.7 89.5 88.7 Example 16 2.3 mg of ligand {XVIII} and 1 mg of (.IrCODCl ] 2

(ligand:Ir ratio of 1.1:1} were pre-mixed in 1 ml of toluene under nitrogen and the mixture was stirred for 30 minutes. 32 μΐ of the previous mixture were fed to a reaction vessel containing 15.5 mg I2 {I2: imine ratio of 0.0025:1), 5 g of imine (I) {Ir: imine ratio of 1:250000) and 5 ml of toluene (toluene : imine ratio 1:1 volume : weight ) , and the vessel was purged with nitrogen. The reaction vessel was purged with Hs in three cycles {10- 20 bar, norma 1 pressure) under stirring {750 rpm) . The hydrogen pressure was set at 30 bar and the mixture heated to 70 °C for 20 hours under stirring (750 rpm) . After cooling to room temperature the pressure was released, reaction mass was sampled (—10 μΐ, diluted to 1.5 ml with isopropanoi} and analysed by HPLC. The conversion of the imine {I) to { S) ~N- ( 2 ' -methyl-6' -ethyi-phenyl ) -N- ( 1- methoxylmethyl j ethylamine (II) was 98.9% and the enantiomeric excess 88.2% (S-isomer) . The estimated reaction time, based on hydrogen uptake data, was 18 hours. Comparative example

1.9 mg of (R, S _P ) -Xyliphos {III) and 1 mg of [IrCODCl];; were pre-mixed in 1 ml of toluene under nitrogen and the mixture stirred for 20-30 minutes. 32 μΐ of the previous mixture were fed to a reaction vessel containing 12.4 mg I2, 216 mg acetic acid, 2.5 g of imine (I) and 10 ml of toluene, and the reaction vessel was purged with nitrogen. The reaction vessel, was purged with ¾ in three cycles (10- 20 bar, normal pressure) under stirring. The hydrogen pressure was set at 30 bar and the mixture heated to 70 'C for 18 hours under stirring. After cooling to room temperature the pressure was released, reaction mass was sampled (-10 μΐ, diluted to 1.5 ml with isopropanol) and analysed by HPLC. The conversion of the imine (I) to (S) ~N~ {2 ^' ' -methyl- 6' -ethyl-phenyl) ~N~ { 1-raethoxylmethyi } ethylamine (II) was 93.2% and the enantiomeric excess 74.6% ( S- isomer) . The estimated reaction time, based on hydrogen uptake data, was 12 hours.

2.2 mg of ligand (XVI II) and 1 mg of [IrCODCl]*. were pre-mixed in 1 ml of toluene under nitrogen and the mixture stirred for 20-30 minutes. 32 μΐ of the previous .mixture were fed to a reaction vessel containing 12.4 mg lz, 2.5 g of imine (I) and 10 ml of toluene, and the reaction vessel was purged with nitrogen. The reaction vessel was purged with ¾ in three cycles (10-20 bar, normal pressure) under stirring. The hydrogen pressure was set at 30 bar and the mixture heated to 70 °C for 18 hours under stirring. After cooling to room temperature the pressure was released, reaction mass was sampled (-10 μΐ, diluted to 1,5 ml with isopropanol) and analysed by HPLC. The conversion of the imine (I) to (S) ~N- (2' -methyl-6' -ethyl-phenyl) -N- (1- methoxylmethyl ) ethylamine ill) was 98.8% and the enantiomeric excess 91.1% {S-isomer) . The estimated reaction time, based on hydrogen uptake data, was 2 hours.

The results of the comparative test show that the process according to the invention results in a 5% increase conversion, a 16% increase n selectivity, and a reduction in reaction time from. 12 to 2 hours when compared to the process using xyliphos . It can be seen that the process according to the invention corresponds to a significant improvement, over prior art since it was possible to operate at. a imine to met l ratio of 250000:1 and achieve a conversion of 98.9% and an enantiomeric excess of 88.2% in a reaction time of 18 hours.