[5]Ferrocenophane based ligands for stereoselective Rh-catalyzed hydrogenation and Cu-catalyzed Michael addition

A series of homochiral [5]ferrocenophane based N/P, N/S, N/Se, Se/P and P/P ligands was prepared from (R)-N,N-dimethylamino[5]ferrocenophane. These ligands were tested in the Rh-catalyzed hydrogenation of dimethyl itaconate and in Cu-catalyzed Michael addition of Et2Zn to cyclohex-2-enone. The best results in terms of conversion and enantioselectivity in the Rh-catalyzed hydrogenation provided bis(diphenylphosphine) ligand 2h (100% conversion and 95% ee) and aminophosphine 2a in the Cu-catalyzed conjugate addition (100% conversion 84% ee). The enantioselectivity of the Rh-catalyzed hydrogenation of methyl 2-acetamidoacrylate was lower (41% ee).

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(R,pS)-1-(Dicyclohexylphosphanyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]ferroceneC29H44FeNP[α]D = −207 (c 0.70, acetone)Source of chirality: asymmetric synthesisAbsolute configuration: (R,pS)

(R,pS)-1-(Di-tert-butylphosphanyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]ferroceneC25H40FeNP[α]D = −395 (c 0.45, methanol)Source of chirality: asymmetric synthesisAbsolute configuration: (R,pS)

(R,pS)-1-(Phenylsulfanyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]ferroceneC23H27FeNS[α]D = −155 (c 0.79, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,pS)

(R,pS)-1-(Phenylselenyl)-2,1′-[1-(dimethylamino)pentan-1,5-diyl]ferroceneC23H27FeNSe[α]D = −148 (c 0.85, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,pS)

(R,pS)-1-(Phenylselenyl)-2,1′-[1-(diphenylphosphanyl)pentan-1,5-diyl]ferrocene, borane complexC33H34BFePSe[α]D = −259 (c 0.27, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,pS)

(R,pS)-1-(Dicyclohexylphosphanyl)-2,1′-[1-(diphenylphosphanyl)pentan-1,5-diyl]ferrocene, bis(borane) complexC39H54B2FeP2[α]D = −204 (c 0.32, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,pS)