Zhi-Hua Zhou et al. / Chinese Journal of Catalysis 40 (2019) 1345–1351
1347
2.4. Characterization data of the products
The reactions were initially investigated with
2
-methylbut-3-yn-2-ol (1a) as the model substrate that was
1
3
-Hydroxy-3-methylbutan-2-one (2a). Colorless oil. H NMR
400 MHz, DMSO-d ) δ 5.23 (s, 1H), 2.15 (s, 3H), 1.17 (s, 6H)
ppm. 13C NMR (101 MHz, DMSO-d
) δ 213.83, 75.74, 26.18,
4.23 ppm. GC-MS (EI, 70 eV) m/z (%) 87 (100), 60 (92), 69
62), 102 (9).
-Hydroxy-3-methylpentan-2-one (2b). Yellow oil. H NMR
400 MHz, DMSO-d ) δ 5.04 (s, 1H), 2.13 (s, 3H), 1.60 (dq, J =
4.9, 7.5 Hz, 1H), 1.46 (dq, J = 14.8, 7.5 Hz, 1H), 1.12 (s, 3H),
.74 (t, J = 7.5 Hz, 3H) ppm. 13C NMR (101 MHz, DMSO-d
) δ
14.19, 78.55, 31.77, 25.10, 24.14, 7.88 ppm. GC-MS (EI, 70 eV)
reacted with water under atmospheric CO pressure to obtain
2
(
6
3-hydroxy-3-methylbutan-2-one (2a), as described in Table 1.
Obviously, 1a could not be effectively converted into 2a with-
out a catalyst or when DBU was used alone (entries 1 and 2).
When employing AgOAc, which was the optimal catalyst in
previous work [20], to promote the hydration, the yield of 2a
was only 10%, with the remaining being mostly 1a (entry 3),
6
2
(
1
3
(
6
1
0
2
indicating the low efficiency of Ag catalysis under ambient CO
pressure. Mechanically, a tandem process involving the cycliza-
tion of propargylic alcohol with CO and the following addition
of water to the in-situ generated α-alkylidene cyclic carbonate
is involved in the hydration of propargylic alcohol with CO as a
2
6
2
m/z (%) 43 (100), 73 (25), 87 (21), 45 (19), 57 (12), 101 (10).
-Hydroxy-3-methylnonan-2-one (2c). Yellow oil. 1H NMR
400 MHz, CDCl ) δ 3.88 (s, 1H), 2.13 (s, 3H), 1.69–1.51 (m, 2H),
.38–1.30 (m, 1H), 1.26 (s, 3H), 1.20 (dd, J = 15.9, 5.9 Hz, 6H),
.94 (tt, J = 15.9, 8.0 Hz, 1H), 0.79 (t, J = 6.8 Hz, 3H) ppm. 13
) δ 212.04, 78.43, 39.09, 31.24, 29.08,
4.93, 23.30, 22.92, 22.12, 13.57 ppm. GC-MS (EI, 70 eV) m/z
3
2
(
3
cocatalyst to prepare α-hydroxy ketone [20,21]. In particular,
efficient cyclization is crucial to the whole process. Therefore,
several Cu compounds were screened for converting 1a to 2a,
owing to their excellent performances in the rate-determining
cyclization [33–35] (entries 4–10). Excitingly, CuCl as the cata-
lyst allowed the reaction to proceed smoothly, affording 31% of
2a (entry 4). By changing the Cu source to CuI, the yield of 2a
was increased to 46% (entry 6). Moreover, a significant in-
1
0
C
NMR (101 MHz, CDCl
3
2
(
(
%) 69 (100), 129 (94), 59 (89), 43 (82), 55 (36), 41 (34), 84
20), 45 (19), 111 (18), 28 (16), 85 (14).
3
-Hydroxy-3,5-dimethylhexan-2-one (2d). Yellow oil. 1H
NMR (400 MHz, CDCl ) δ 3.83 (s, 1H), 2.18 (s, 3H), 1.69–1.57
m, 3H), 1.29 (s, 3H), 0.89 (d, J = 6.4 Hz, 3H), 0.79 (t, J = 6.1 Hz,
3
crease in the yield of 2a was observed when employing Cu
O as
2
(
3
2
the catalyst (entry 7). Comparatively, Cu(II) showed a lower
catalytic activity than Cu(I) (entries 7–9). The poor activity of
CuOAc should be ascribed to its moisture sensitivity (entry 10).
Notably, an increase in the amount of water could obviously
decrease the rate of hydration (entries 11 and 12), and no 2a
was observed when five equivalents of water was supplied
H) ppm. 13C NMR (101 MHz, CDCl
6.56, 24.19, 23.76, 23.41 ppm. GC-MS (EI, 70 eV) m/z (%) 81
) δ 212.71, 78.96, 47.71,
3
(
100), 99 (96), 43 (29), 55 (21), 79 (19), 57 (10).
-(1-Hydroxycyclohexyl)ethan-1-one (2e). Yellow oil. 1
NMR (400 MHz, CDCl ) δ 2.24 (s, 3H), 1.75–1.64 (m, 6H), 1.49
d, J = 6.5 Hz, 2H), 1.28 (dd, J = 15.1, 10.3 Hz, 2H) ppm. 13C NMR
101 MHz, CDCl ) δ 212.74, 77.97, 33.82, 25.28, 23.69, 21.07
1
H
3
(
(
Table 1
3
Investigation on Cu catalysis for the hydration of propargylic alcohol
ppm. GC-MS (EI, 70 eV) m/z (%) 81 (100), 99 (71), 79 (21).
-Hydroxy-3-phenylbutan-2-one (2f). Brown oil. 1H NMR
400 MHz, CDCl ) δ 7.48–7.42 (m, 2H), 7.38 (t, J = 7.6 Hz, 2H),
.32 (dd, J = 10.5, 3.8 Hz, 1H), 2.09 (s, 3H), 1.79 (s, 3H) ppm. 13
a
with CO
2
as a cocatalyst .
3
(
3
7
C
3
NMR (101 MHz, CDCl ) δ 209.62, 141.37, 128.68, 128.05,
125.96, 79.84, 23.99, 23.43 ppm. GC-MS (EI, 70 eV) m/z (%)
1
21 (100), 77 (31), 105 (19).
3
Entry
Catalyst
—
—
AgOAc
CuCl
CuBr
CuI
Additive
—
Yield of 2a b (%)
-Hydroxy-3-methylpent-4-en-2-one (2g). Yellow oil. 1H
NMR (400 MHz, CDCl ) δ 5.91 (dd, J = 17.1, 10.5 Hz, 1H), 5.44
dd, J = 17.1, 0.9 Hz, 1H), 5.22 (dd, J = 10.6, 0.8 Hz, 1H), 3.93 (s,
1c
0
4
10
31
30
46
76
54
7
13
12
0
73
97
79
71
55
3
2
3
4
5
6
7
8
9
—
—
—
—
—
—
—
—
(
1
2
H), 2.20 (s, 3H), 1.43 (s, 3H) ppm. 13C NMR (101 MHz, CDCl
09.38, 138.76, 116.23, 79.31, 24.25, 23.60 ppm. GC-MS (EI, 70
3
) δ
eV) m/z (%) 55 (100), 83 (83), 43 (68), 99 (37), 101 (36), 41
2
Cu O
(
(
31), 45 (30), 71 (24), 29 (15), 57 (13), 100 (10), 74 (10), 27
10).
CuO
CuSO
4
10
11
12
13
CuOAc
—
—
—
1
7-Hydroxy-17βHpregn-4-ene-3,20-dione (2h). White solid,
d
e
Cu
2
Cu
2
Cu
2
Cu
2
Cu
2
Cu
2
Cu
2
O
O
O
O
O
O
O
1
m.p. 192–193 °C. H NMR (400 MHz, CDCl
3
) δ 5.72 (s, 1H), 2.92
(d, J = 30.2 Hz, 1H), 2.38–2.23 (m, 8H), 2.03–1.95 (m, 1H),
PPh
3
1
.91–1.84 (m, 1H), 1.72–1.40 (m, 10H), 1.18 (s, 3H), 1.10–1.04
14
15
L1
L2
L3
L4
m, 1H), 0.98 (s, 3H), 0.92 (dd, J = 9.8, 5.9 Hz, 1H) ppm. 13C NMR
(
(
16
101 MHz, CDCl
3
) δ 214.22, 199.43, 171.01, 123.82, 90.65,
1
7
5
3
C
3.18, 49.06, 38.47, 36.08, 35.55, 34.95, 33.81, 32.95, 32.68,
1.49, 28.19, 24.18, 20.66, 17.27, 14.07 ppm. HRMS (ESI):
a
Reaction conditions: 1a (1 mmol, 84.1 mg), H
2
O (1 mmol, 18.0 mg),
catalyst (20 mol%), additive (20 mol%), DBU (0.5 mmol, 76.1 mg), CO
balloon, CH CN (1 mL), 60 °C, 24 h. Determined by GC analysis with
2
+
b
21
H O
31 3
for [M + H] calcd 331.2268, found 331.2274.
3
c
d
biphenyl (20 mg) as the internal standard. Without DBU.
2
H O.
e
2
H O (5 mmol, 90.0 mg).
3
. Results and discussion