Scheme 1 (a) Diphosphite ligands used as stabilising agents for Ir NPs; (b) hydrogenation of m–
and o–methylanisole by Ir NPs
Table 1 Hydrogenation of m– and o–methylanisole by Ir NPs stabilised with chiral diphosphite
ligands derived from carbohydrates
L
Size (nm)
Substrate
Conversion (%)
Cis (%)
ee (%)
TON
a
1.3
m-methylanisole
87
81
–
70
b
1.5
m-methylanisole
14
75
–
12
a
a
1.4
m-methylanisole
0
–
–
–
a
1.3
o-methylanisole
96
100
1
77
b
1.5
o-methylanisole
4
100
2
3
a
a
1.4
o-methylanisole
0
–
–
–
Reaction conditions: Substrate/Ir ¼ 40, methylanisole (1.24 mmol), pentane (10 mL), H 2 (40 bar),
room temperature (RT), 24 h
a [Ir(cod) 2 ]BF 4 as precursor
Scheme 2 (a) (R,R)-BDPP ligand employed for the synthesis of Ir NPs. (b) Asymmetric hydrogenation of ethyl pyruvate to ethyl lactate
400
L. M. Martínez-Prieto et al.