1 3
Topics in Current Chemistry (2019) 377:38
synergistic employment of combined rhodium and simple chiral amine catalysts in
the enantioselective Michael addition of cyclic ketones with α,β-unsaturated 2-acyl
imidazoles [67]. Furthermore, Gong’s group devised a chemical reaction in the first
enantioselective α-allylation of aldehydes with terminal alkenes using asymmetric
counter-anion catalysis and palladium-catalyzed allylic C–H activation combined
with enamine catalysis [68]. The coupling between α-branched aromatic aldehydes
79 and terminal alkenes 80 delivered the chiral allylated products 82 in high yield,
and with moderate-to-high enantioselectivity (Scheme 17). Additionally, very
recently, the same group employed a combination of palladium catalyst integrated
with the chiral amine 85 to prepare γ-coupled product 86 (Scheme 18) [69]. In 2014,
O
+
78a R
1 = CH(CO 2 Me) 2 , 87% yield, 1.6:1 d.r.
78b R
1 = Ph, 82% yield, 1.7:1 d.r.
78c R
1 = 4-Br-Ph, 71% yield, 2.0:1 d.r.
78d R
1 = OH-CH 2 , 95% yield, 1.6:1 d.r.
[Rh(coe) 2 Cl] 2 (2.5 mol%)
76 (5 mol%), 77 (25 mol%)
TsOH H 2 O (10 mol%)
toluene (0.2 M), 130
o
C, 48 h
74
75
78
76
N
N
N
N
H
77
O
R
1
R
1
N
R
1
R
2
ML n
DG
H
N
R
1
R
2
M
III
L n
DG
H
N
R
1
R
2
M
III
L n
DG
H
H
N
R
1
R
2
ML n
DG
H
H
IX
X
X I
X II
Scheme 16 Regioselective α-alkylation of ketones 74 with ethylene 75 through combined rhodium and
amine catalysts
+
82a Ar = 4-MeC 6 H 4 , R = Ph , 65% yield, 88 % ee
82b Ar = 4-ClC 6 H 4 , R = Ph , 89% yield, 74 % ee
82c Ar = Ph, R = 4-tBuC 6 H 4 , 90% yield, 90 % ee
82d Ar = Ph, R = 4-MeOC 6 H 4 , 79% yield, 90 % ee
33 (R)-TRIP (3 mol%)
3Å M.S., DMBQ (1.5 equiv.)
[Pd(PPh 3 ) 4 ] (3 mol%)
79
80
82
CHO
Ar
R
R
CHO
Ar
Ph
NH 2
81 (40 mol%)
Scheme 17 Enantioselective α-allylation of aldehydes 79 and terminal alkenes 80
+
Pd(CH 3 CN) 2 Cl 2 (10 mol%)
PhCO 2 H (0.5 equiv.)
EtOH, 80
o
C, 72 h
84
83
86
85 (40 mol%)
N
H
OH
Ph
Ph
N
N
H
O
O
O
H
N
N
R
1
O
R
1
86a R
1 = Me, 74% yield, 4.9:1 d.r., 91% ee
86b R
1 = CF 3 , 63% yield, 1.3:1 d.r., 90% ee
86c R
1 = 4-MeC 6 H 4 , 98% yield, 3.1:1 d.r., 92% ee
86d R
1 = 4-ClC 6 H 4 , 89% yield, 2.6:1 d.r., 92% ee
Scheme 18 Enantioselective addition of cyclic ketones 83 to unactivated alkenes 84 generating the
γ-addition products 86
Reprinted from the journal
13
Topics in Current Chemistry (2019) 377:38
synergistic employment of combined rhodium and simple chiral amine catalysts in
the enantioselective Michael addition of cyclic ketones with α,β-unsaturated 2-acyl
imidazoles [67]. Furthermore, Gong’s group devised a chemical reaction in the first
enantioselective α-allylation of aldehydes with terminal alkenes using asymmetric
counter-anion catalysis and palladium-catalyzed allylic C–H activation combined
with enamine catalysis [68]. The coupling between α-branched aromatic aldehydes
79 and terminal alkenes 80 delivered the chiral allylated products 82 in high yield,
and with moderate-to-high enantioselectivity (Scheme 17). Additionally, very
recently, the same group employed a combination of palladium catalyst integrated
with the chiral amine 85 to prepare γ-coupled product 86 (Scheme 18) [69]. In 2014,
O
+
78a R
1 = CH(CO 2 Me) 2 , 87% yield, 1.6:1 d.r.
78b R
1 = Ph, 82% yield, 1.7:1 d.r.
78c R
1 = 4-Br-Ph, 71% yield, 2.0:1 d.r.
78d R
1 = OH-CH 2 , 95% yield, 1.6:1 d.r.
[Rh(coe) 2 Cl] 2 (2.5 mol%)
76 (5 mol%), 77 (25 mol%)
TsOH H 2 O (10 mol%)
toluene (0.2 M), 130
o
C, 48 h
74
75
78
76
N
N
N
N
H
77
O
R
1
R
1
N
R
1
R
2
ML n
DG
H
N
R
1
R
2
M
III
L n
DG
H
N
R
1
R
2
M
III
L n
DG
H
H
N
R
1
R
2
ML n
DG
H
H
IX
X
X I
X II
Scheme 16 Regioselective α-alkylation of ketones 74 with ethylene 75 through combined rhodium and
amine catalysts
+
82a Ar = 4-MeC 6 H 4 , R = Ph , 65% yield, 88 % ee
82b Ar = 4-ClC 6 H 4 , R = Ph , 89% yield, 74 % ee
82c Ar = Ph, R = 4-tBuC 6 H 4 , 90% yield, 90 % ee
82d Ar = Ph, R = 4-MeOC 6 H 4 , 79% yield, 90 % ee
33 (R)-TRIP (3 mol%)
3Å M.S., DMBQ (1.5 equiv.)
[Pd(PPh 3 ) 4 ] (3 mol%)
79
80
82
CHO
Ar
R
R
CHO
Ar
Ph
NH 2
81 (40 mol%)
Scheme 17 Enantioselective α-allylation of aldehydes 79 and terminal alkenes 80
+
Pd(CH 3 CN) 2 Cl 2 (10 mol%)
PhCO 2 H (0.5 equiv.)
EtOH, 80
o
C, 72 h
84
83
86
85 (40 mol%)
N
H
OH
Ph
Ph
N
N
H
O
O
O
H
N
N
R
1
O
R
1
86a R
1 = Me, 74% yield, 4.9:1 d.r., 91% ee
86b R
1 = CF 3 , 63% yield, 1.3:1 d.r., 90% ee
86c R
1 = 4-MeC 6 H 4 , 98% yield, 3.1:1 d.r., 92% ee
86d R
1 = 4-ClC 6 H 4 , 89% yield, 2.6:1 d.r., 92% ee
Scheme 18 Enantioselective addition of cyclic ketones 83 to unactivated alkenes 84 generating the
γ-addition products 86
Reprinted from the journal
13