Enantioselective hydrogenation of 4-substituted 1,2-dihydroquinolines in presence of a chiral iridium catalyst

A process for preparing a compound of the formula (Ia) or (Ib),

• wherein
• R1 is C1-C6-alkyl,
• R2 and R3 are the same and are selected from the group consisting of C1-C6-alkyl,
• R4 is C1-C6-alkyl,
• n is 0 or 1,
• each substituent R5, if present, is independently selected from the group consisting of halogen, comprising enantioselective hydrogenation of a compound of the formula (II)
• wherein the substituents R1, R2, R3, R4, R5 and the integer n are each as defined for the compound of the formula (Ia) or (Ib),
• in presence of a chiral iridium catalyst,
• characterized in that the chiral iridium catalyst comprises a chiral ligand of the formula (IIIa) or (IIIb)
• wherein
• R6 and R7 are independently from one another selected from consisting of hydrogen, C1-C6-alkyl, and C6-C14-aryl,
• wherein the C6-C14-aryl is optionally substituted by one to five substituents selected from the group consisting of halogen, C1-C4-alkyl, C1-C4-haloalkyl, and C1-C4-alkoxy,
• R8 is methyl,
• R9 and R10 are independently from one another selected from the group consisting of C1-C6-alkyl, and C3-C12-cycloalkyl, and
• m is 1 or 2.