2 Frustrated Lewis Pair Catalyzed Asymmetric Reactions
67
Table 2.28 Asymmetric Piers-type hydrosilylation of ketones
Ar
R
O
1. HB(C 6 F 5 ) 2 10 (5 mol %)
chiral diene 9h (2.5 mol %)
t Bu 3 P (5 mol %)
Ph 2 SiH 2 (1.2 equiv)
2. TBAF, THF
Ar
R
OH
54
51
entry product
yield (%) ee (%)
1
51a
Ph
Me
OH
88
93
2
51c
Me
OH
F
98
97
3
51d
Me
OH
MeO
95
96
4
51j
Me
OH
Cl
87
94
5
51l
Me
OH
97
88
6
51m
Me
OH
S
96
81
7
51t
Ph
Bn
OH
99
86
8
51w
Ph
Et
OH
97
97
9
51x
OH
93
87
Chromanones and flavanones are important moieties contained in a variety of
biologically and medicinally active compounds. With 0.1 mol % of borane catalyst derived from pentafluorostyrene and HB(C 6 F 5 ) 2 , a Piers-type hydrosilylation of
chromones and flavones was realized to afford various chromanones and flavanones
in 60–99% yields [59]. The asymmetric hydrosilylation was performed using chiral