Chemistry Reference
In-Depth Information
Table 5.6 Asymmetric CDC reaction of 6,7-dimethoxytetrahydroisoquinolines with
alkynes by ball milling.
a,b
R
1
N
∗
R
2
Ar
DDQ/Pybox-1
R
1
Cu(OTf)
2
/Copper balls
+
H
R
N
Silica gel
ball milling
R
2
Ar
1
6
7
1d
: R
1
= R
2
= OMe, Ar = Ph
1g
: R
1
= R
2
= OMe, Ar = 4-MeOC
6
H
4
6a
: R = Ph
6f
: R = CO
2
Me
MeO
MeO
MeO
N
N
∗
∗
MeO
MeO
N
∗
MeO
OMe
O
OMe
7l 7s 7t
72%, 22% ee, 50 min 70%, 22% ee, 40 min 56%, 20% ee, 150 min
a
Reactions were carried out with 1 (1.0 mmol), 6 (1.1 mmol), DDQ (1.0 mmol), Cu(OTf)
2
(5 mol%), Pybox-1 (10 mol%), silica gel (0.5 g) and two copper balls (d
¼
12.0 mm) at 30 Hz for
10 min followed by a 5 min pause until the finish of reaction. Isolated yields based on 1.
b
Enantiomeric excess determined by HPLC analysis using a chiral stationary phase.
Table 5.7 Effects of frequency on C(sp
3
)
H and C(sp)
H bond coupling
reactions.
a
Reproduced from ref. 24. Copyright 2013, with permission
from Elsevier.
Yield (%)
b
ee (%)
c
Entry
Frequency (Hz)
Time (min)
1
30
30
69
74
2
25
60
62
69
3
20
60
42
70
4
15
80
—
—
5
d
30 30 75 43
a
Unless otherwise noted, reactions were carried out with 1a (1.0 mmol), 6a (1.1 equiv.), DDQ (1.0
equiv.), PyBox-1 (10 mol%), 0.5 g of silica gel and two copper balls (d
¼
12.0 mm) at a certain
frequency for 10 min followed by a 5 min pause until the finish of reaction.
b
Isolated yields based on 1a.
c
Determined by HPLC analysis using a chiral stationary phase.
d
The reaction was carried out without pause.
milling cycle of 10 min followed by a 5 min pause was adopted during the
reaction process, the heat generated by the mill was insignificant for each 10
min cycle. If the reaction was carried out without a pause in milling, the
conversion was accelerated and the product's ee was decreased. In this case,
the inside temperature would be relatively high (the measured outside
temperature was about 38-40 1C).
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