A practical process to chiral ferrocenyl alcohols via asymmetric transfer hydrogenation catalyzed with a PEG-bound Ru catalyst in water and its application in preparing Ugi’s amine

Chiral ligand (S,S)-PEG-BsDPEN has been found to be efficient for the asymmetric transfer hydrogenation of various ferrocenyl ketones. With sodium formate as a hydrogen donor, PEG 2000 and water as the reacting media, the catalyst system could be recycled several times. This procedure could be scaled up to a 100 mmol or more in a common round flask which is easy to perform in ordinary laboratories. The preparation of Ugi’s amine with the ferrocenyl alcohol was also investigated.

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(S)-(+)-1-FerrocenylethanolC12H14FeO[α]D20=+28 (c 1.33, CH2Cl2)Ee: 98%Absolute configuration: (S)Source of chirality: asymmetric transfer hydrogenation

(S)-(+)-1-(α-Chloroferrocenyl)ethanolC12H13ClFeO[α]D20=+19 (c 0.93, CH2Cl2)Ee: 98%Absolute configuration: (S)Source of chirality: asymmetric transfer hydrogenation

(R)-(-)-FerrocenylphenylmethanolC17H16FeO[α]D20=-94 (c 1.01, CH2Cl2)Ee: 93%Absolute configuration: (R)Source of chirality: asymmetric transfer hydrogenation