Preparation of Mesoporous Silica-Supported Chiral Amino Alcohols for the Enantioselective Addition of Diethylzinc to Aldehyde and Asymmetric Transfer Hydrogenation to Ketones

Table 3

Asymmetric transfer hydrogenation of ketones using immobilized ligands 2b^a.

Entry	Ketone^b	Time (h)	Conv. (%)^c	e.e. (%)^d
1	Acp	3	96 (92)^e	77 (74)^e
2	Pp	3	94	70
3	3-OMe-Acp	3	98	75
4	4-Cl-Acp	3	99	71
5^f	4-Cl-Acp	4	92	82

The reactions were carried out at room temperature in 2-propanol; ketone : Ru : ligand : KOH = 100 : 1 : 2 : 5. ^bAcp = acetophenone and Pp = propiophenone. ^cDetermined by GC analysis. ^dDetermined by HPLC analysis using Chiralcel OD-H column (3% of 2-propanol in hexane, 1 mL/min). ^eThe catalyst was reused two times. ^f[RuCl₂(hexamethylbenzene)]₂ was used instead of [RuCl₂(-cymene)]₂.