A gold(III)-catalyzed double Wacker-type reaction of 1,1-diethynyl acetate

Article abstract of DOI:10.1055/s-2006-956497

Treatment of 1,1-diethynyl acetates in the presence of Au or Pt catalyst (5 mol%) in methanol at 60 °C for 20-48 hours gave γ-ketoesters and lactones in 40-54% and 19-39% yields, respectively. An oxygen atom is introduced to the first acetylene moiety in

Full text of DOI:10.1055/s-2006-956497

LETTER
63
A Gold(III)-Catalyzed Double Wacker-Type Reaction of 1,1-Diethynyl Acetate
G
old(III)-Catalyze
e
dDouble
W
i
acker-
s
type Rea
c
u
tion of 1,1-D
k
iethynyl
A
c
e
etate Kato,*a Ryuhei Teraguchi,a Taichi Kusakabe,a Satoshi Motodate,a Shigeo Yamamura,a Tomoyuki Mochida,b
Hiroyuki Akita*a
a
Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
b
Department of Chemistry, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan
Fax +81(474)721825; E-mail: kkk@phar.toho-u.ac.jp
Received 5 October 2006
As the starting point in this study, we selected 2a as a stan-
Abstract: Treatment of 1,1-diethynyl acetates in the presence of
Au or Pt catalyst (5 mol%) in methanol at 60 °C for 20–48 hours
gave g-ketoesters and lactones in 40–54% and 19–39% yields,
respectively. An oxygen atom is introduced to the first acetylene
dard substrate to search for potential catalysts and suitable
reaction conditions (Equation 1 and Table 1). Treatment
of 2a in the presence of Au or Pt catalyst (5 mol%) in
moiety in accordance with Markovnikov’s rule, and to the second methanol at 60 °C for 20–48 hours gave the g-ketoester 3a
acetylene moiety with anti-Markovnikov regioselectivity.
and the lactone 4a in 40–54% and 19–39% yields, respec-
tively (entries 1–6). Commercially available gold(I) chlo-
ride (AuCl), chloroauric acid hydrate (HAuCl4·3H2O),
platinum(IV) chloride (PtCl4), platinum(II) chloride
(PtCl2), gold(III) chloride (AuCl3) and cationic triphen-
ylphosphinegold(I) chloride (Ph3PAuCl)–silver hexa-
fluoroantimonate (AgSbF6)3g exhibited almost the same
catalytic activity. Among these, HAuCl4·3H2O gave
better total yield (entry 1). When isobutanol was used as a
solvent, isobutyl ester 3f and 4a were obtained in similar
yields (entry 7). However, a complex mixture was ob-
tained when toluene was used as the solvent (entry 8).
Key words: 1,1-diethynyl acetates, double Wacker-type reaction,
gold, platinum, catalyst
Transition-metal-catalyzed reaction of unsaturated sys-
tems has recently proven to be a powerful method for the
construction of a variety of carbo- and heterocycles.1 Gold
and platinum salts are recognized as efficient catalysts for
hydration and related cyclization of alkynes.2 A large
number of reactions of propargylic esters mediated by
gold and platinum catalysts have been recently reported.3
However, the reactions of 1,1-diethynyl acetates are
extremely rare.4 Previously, we have reported the in-
tramolecular oxycarbonylation of 4-yne-1-ols,5a–c 4-yne-
1-ones5d and propargyl acetates5e,f catalyzed by Pd(II)
complexes. Herein, we report a Au(III)-catalyzed double
Wacker-type reaction of 1,1-diethynyl acetates 2. 1,1-Di-
ethynyl acetates 2 were prepared from the corresponding
esters 1 by the following three step procedure with a sin-
gle column purification.6 Addition of lithiated acetylene
moiety to 1 followed by desilylation, and subsequent
acetylation afforded 2 in good yields (Equation 1).
O
catalyst
(5 mol%)
O
O
Me
CO2R
Ph
+
60 °C in ROH
O
Me
O
Ph
3a, R = Me
3f, R = i-Bu
Me
Ph
2a
4a
Equation 2
Next, substrates 2b–e were tested for the reaction using
5 mol% of HAuCl4·3H2O as catalyst; the corresponding
results are listed in Table 2 (Equation 3).7 The reaction of
2b containing a benzyl group, afforded the corresponding
products 3b and 4b in 53% and 27% yields, respectively
(entry 1). In the case of 2c and 2d containing long alkyl
chains, 3c,d and 4c,d were obtained in about a 1:1 ratio
(entries 2 and 3). The present reaction was performed
under an argon atmosphere, suggesting that the reaction
does not require molecular oxygen (entry 4). When the
substrate 2e, containing a phenyloxy group, was em-
ployed in the reaction, a complex mixture was obtained.
–
Li+ (3 equiv)
R
TMS
1)
RCO2Et
O
2) TBAF, THF
3) Ac2O, pyridine
O
1
2
R
2a, R = PhCH2CH2: 91%
2b, R = PhCH2: 87%
2c, R = Octyl: 93%
2d, R = Pentyl: 87%
2e, R = PhOCH2: 89%
O
HAuCl4·3H2O
(5 mol%)
Equation 1
O
O
R
+
Me
CO2Me
O
60 °C in MeOH
Me
R
O
Me
R
3
4
SYNLETT 2007, No. 1, pp 0063–0066
0
4.
0
1.
2
0
0
7
2
Advanced online publication: 20.12.2006
DOI: 10.1055/s-2006-956497; Art ID: U12006ST
© Georg Thieme Verlag Stuttgart · New York
Equation 3

64
K. Kato et al.
LETTER
Table 1 Double Wacker-type Reaction of 2a (Equation 2)
Entry
Catalyst (5 mol%)
Solvent
Time
3a
4a
Yield (%)
Yield (%)
1
2
3
4
5
6
7
8
HAuCl4·3H2O
AuCl
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
i-BuOH
toluene
20 h
20 h
48 h
20 h
20 h
48 h
20 h
20 h
51
39
26
22
30
19
26
26
46
AuCl3
52
PtCl4
40
PtCl2
42
Ph3PAuCl–AgSbF6
HAuCl4·3H2O
HAuCl4·3H2O
54
52: 3f
complex mixture
Table 2 HAuCl4·3H2O-Catalyzed Double Wacker-Type Reaction
of 2
the second alkyne by methanol with anti-Markovnikov
regioselectivity, followed by cyclization to produce the
furan intermediate B. Hydrolysis of the furan intermediate
B gives the products 3 and 4.
Entry
R
Time
22 h
22 h
18 h
20 h
Yield (%) Yield (%)
1
2b: PhCH2
2c: Octyl
2d: Pentyl
2a: Ph(CH2)2
3b (53)
3c (46)
3d (46)
3a (48)
4b (27)
4c (47)
4d (40)
4a (38)
R
2
H
O
O
OMe
R
R
OMe
3
Me
O
O
B
2
4a
Me
hydrolysis
MeO
•
a The reaction was performed under an argon atmosphere.
MCln
R
O
O
H+
MCln
R
Me
M–Cln
CO2Me
To elucidate the mechanism of the present reaction, 1a
was treated with the same catalyst at –20 °C for 48 hours
to afford the orthoester 5 in 58% yield (Equation 4). This
result is in good accordance with a previous report;3f the
double Wacker-type reaction depicted in Equations 2
and 3 should be initiated by cyclization of the acetyl
group.
R
O
O
3
+
MeOH
Me
H+
O
R
MeO
•
O
4
R
O
MeOH
Me
M–Cln
M–Cln
Me
R
O
MeO
H
A
O
HAuCl4·3H2O
(5 mol%)
AcOMe
Ph
Ph
O
Scheme 1
O
O
–20 °C, 48 h, MeOH
O
OMe
Me
Me
In conclusion, we have reported the double Wacker-type
reaction of 1,1-diethynyl acetates. During the reaction, the
acetate has dual functions: 1) neighboring group partici-
pation of the carbonyl oxygen leads to the ‘Markovnikov’
hydration of the first acetylene moiety; 2) elimination of
the MeOAc leaving group leads to addition of methanol to
the second acetylene, which follows ‘anti-Markovnikov’
addition. As a result, simple ester groups can be success-
fully converted into g-ketoesters and lactones.
1a
5: 58%
Equation 4
A plausible mechanism of the present reactions is pro-
posed as shown in Scheme 1. 5-exo-dig-Cyclization of
1,1-diethynyl acetates 2 via nucleophilic attack of the first
alkyne by a carbonyl oxygen in accordance with
Markovnikov’s rule generates the intermediate A. Elimi-
nation of MeOAc should induce a nucleophilic attack of
Synlett 2007, No. 1, 63–66 © Thieme Stuttgart · New York

LETTER
Gold(III)-Catalyzed Double Wacker-type Reaction of 1,1-Diethynyl Acetate
65
at –10 °C for 12 h and quenched with H2O (80 mL) and
EtOAc (80 mL). The organic layers were separated, the
aqueous layer was extracted with EtOAc (50 mL), and
combined organic layers were dried with MgSO4 and
References and Notes
(1) (a) Handbook of Organopalladium Chemistry for Organic
Synthesis, Vol. II; Negishi, E., Ed.; Wiley: New York, 2002,
2309. For recent reviews, see: (b) Nakamura, I.;
concentrated in vacuo. To a solution of the crude product in
THF (30 mL) was added TBAF (22.4 mL of 1 M in THF,
22.4 mmol) and the mixture was stirred for 0.5 h at r.t. The
mixture was diluted with H2O (80 mL) and EtOAc (80 mL).
The organic layers were separated, the aqueous layer was
extracted with EtOAc (2 × 50 mL), and combined organic
layers were dried with MgSO4 and concentrated in vacuo. To
a solution of the crude product in pyridine (3 mL) and Ac2O
(2 mL) was added 4-dimethylaminopyridine (50 mg) and the
mixture was stirred for 3–10 h at r.t. The mixture was diluted
with H2O (50 mL) and EtOAc (50 mL). The organic layers
were separated, the aqueous layer was extracted with EtOAc
(50 mL), and combined organic layers were washed with aq
10% HCl, dried with MgSO4 and concentrated in vacuo. The
crude product was purified by column chromatography on
silica gel. The fraction eluted with hexane–EtOAc (100:1–
20:1) afforded 2. 2a: colorless needles; mp 51 °C. 1H NMR
(CDCl3): d = 2.09 (s, 3 H), 2.37–2.41 (m, 2 H), 2.70 (s, 2 H),
2.93–2.97 (m, 2 H), 7.19–7.32 (m, 5 H). 13C NMR (CDCl3):
d = 21.3, 30.4, 43.8, 66.3, 74.4, 80.0, 126.2, 128.5, 128.5,
140.6, 168.3. FAB–MS: m/z = 249 [M+ + Na]. IR (KBr):
3253, 2935, 2120, 1748 cm–1. Anal. Calcd for C15H14O2: C,
79.62; H, 6.24. Found: C, 79.41; H, 6.41. 2b: colorless oil.
1H NMR (CDCl3): d = 2.07 (s, 3 H), 2.66 (s, 2 H), 3.37 (s, 2
H), 7.25–7.39 (m, 5 H). 13C NMR (CDCl3): d = 21.4, 47.6,
66.7, 74.9, 79.8, 127.5, 127.9, 131.2, 133.7, 168.2. HRMS–
EI: m/z [M+] calcd for C14H12O2: 212.0837; found: 212.0833.
IR (KBr): 3270, 2122, 1744 cm–1. 2c: colorless oil. 1H NMR
(CDCl3): d = 0.89 (t, J = 6.8 Hz, 3 H), 1.26–1.38 (m, 10 H),
1.58–1.66 (m, 2 H), 2.04–2.08 (m, 2 H), 2.09 (s, 3 H), 2.64
(s, 2 H). 13C NMR (CDCl3): d = 14.1, 21.4, 22.7, 23.9, 29.1,
29.2, 29.4, 31.8, 42.2, 66.8, 73.5, 80.3, 168.3. FAB–MS:
m/z = 235 [M+ + H]. IR (KBr): 3291, 2929, 2123, 1757
cm–1. Anal. Calcd for C15H22O2: C, 77.88; H, 9.46. Found: C,
76.12; H, 9.53. 2d: colorless oil. 1H NMR (CDCl3): d = 0.92
(t, J = 7.0 Hz, 3 H), 1.33–1.38 (m, 4 H), 1.59–1.67 (m, 2 H),
2.03–2.08 (m, 2 H), 2.09 (s, 3 H), 2.64 (s, 2 H). 13C NMR
(CDCl3): d = 13.9, 21.4, 22.4, 23.6, 31.3, 42.2, 66.8, 73.6,
80.3, 168.4. HRMS–EI: m/z [M+] calcd for C12H16O2:
192.1150; found: 192.1143. IR (KBr): 3292, 2958, 2123,
1756 cm–1. 2e: colorless needles; mp 47 °C. 1H NMR
(CDCl3): d = 2.09 (s, 3 H), 2.69 (s, 2 H), 4.36 (s, 2 H), 6.97–
7.01 (m, 3 H), 7.24–7.31 (m, 2 H). 13C NMR (CDCl3): d =
21.2, 65.7, 73.4, 74.9, 77.7, 115.4, 121.9, 129.5, 158.4,
168.1. HRMS–EI: m/z [M+] calcd for C14H12O3: 228.0787;
found: 228.0786. IR (KBr): 3281, 2132, 1767 cm–1.
Yamamoto, Y. Chem. Rev. 2004, 104, 2127. (c) Zeni, G.;
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(3) 1,2-Migration of acyl group: (a) Mamane, V.; Gress, T.;
Krause, H.; Fürstner, A. J. Am. Chem. Soc. 2004, 126, 8654.
(b) Shi, X.; Gorin, D. J.; Toste, F. D. J. Am. Chem. Soc. 2005,
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(6) Preparation of Substrates 2; General Procedure: To a
solution of trimethylsilyl acetylene (3.32 g, 33.8 mmol) in
THF (30 mL) under Ar was added n-BuLi (13.0 mL of 2.6
M in hexane, 33.8 mmol) at –78 °C and the mixture was
stirred for 0.5 h at 0 °C. After the solution was cooled to
–78 °C, the corresponding ester 1 (11.3 mmol) in THF (3 ×
8 mL) was slowly added dropwise. The mixture was stirred
(7) Reaction of 2; General Procedure: A 20-mL round-
bottomed flask, containing a magnetic stirring bar, catalyst
(0.015 mmol), 2 (0.3 mmol) and MeOH (5 mL) was fitted
with a Dimroth condenser capped with a rubber septum.
After being stirred for a certain period at 60 °C, the mixture
was diluted with EtOAc (20 mL) and washed with aq 3%
NaHCO3 (20 mL). The organic layers were separated, the
aqueous layer was extracted with EtOAc (30 mL), and
combined organic layers were dried with MgSO4 and
concentrated in vacuo. The crude product was purified by
column chromatography on silica gel. The fraction eluted
with hexane–EtOAc (100:1–50:1 and 10:1) afforded 3 and 4,
respectively. 3a: colorless oil. 1H NMR (CDCl3): d = 1.69–
1.78 (m, 1 H), 1.91–2.00 (m, 1 H), 2.22 (s, 3 H), 2.43 (dd,
J = 4.4, 16.8 Hz, 1 H), 2.58–2.62 (m, 2 H), 2.80 (dd, J = 9.6,
16.8 Hz, 1 H), 2.99–3.07 (m, 1 H), 3.66 (s, 3 H), 7.15–7.32
(m, 5 H). 13C NMR (CDCl3): d = 29.5, 32.8, 33.1, 34.9, 47.4,
Synlett 2007, No. 1, 63–66 © Thieme Stuttgart · New York

66
K. Kato et al.
LETTER
51.7, 126.2, 128.2, 128.5, 140.9, 172.7, 210.5. HRMS–EI:
m/z [M+] calcd for C14H18O3: 234.1256; found: 234.1252. IR
(KBr): 1736, 1712 cm–1. 3b: colorless oil. 1H NMR (CDCl3):
d = 2.06 (s, 3 H), 2.28 (dd, J = 4.4, 17.0 Hz, 1 H), 2.54 (dd,
J = 8.4, 13.6 Hz, 1 H), 2.70 (dd, J = 10.0, 17.0 Hz, 1 H), 2.87
(dd, J = 7.2, 13.6 Hz, 1 H), 3.18–3.25 (m, 1 H), 3.55 (s, 3 H),
7.07–7.24 (m, 5 H). 13C NMR (CDCl3): d = 30.3, 35.0, 37.6,
49.6, 51.6, 126.7, 128.6, 128.8, 138.1, 172.6, 210.6. HRMS–
EI: m/z [M+] calcd for C13H16O3: 220.1100; found: 220.1097.
IR (KBr): 1738, 1205 cm–1. 3c: colorless oil. 1H NMR
(CDCl3): d = 0.81 (t, J = 6.8 Hz, 3 H), 1.14–1.38 (m, 13 H),
1.49–1.56 (m, 1 H), 2.16 (s, 3 H), 2.28 (dd, J = 4.4, 16.8 Hz,
1 H), 2.67 (dd, J = 10.0, 16.8 Hz, 1 H), 2.88–2.95 (m, 1 H),
3.58 (s, 3 H). 13C NMR (CDCl3): d = 14.0, 22.6, 26.8, 29.1,
29.3, 29.5, 29.5, 31.3, 31.8, 34.9, 47.9, 51.6, 173.0, 210.9.
HRMS–EI: m/z [M+] calcd for C14H26O3: 242.1882; found:
242.1893. IR (KBr): 2928, 1739, 1715 cm–1. 3d: colorless
oil. 1H NMR (CDCl3): d = 0.81 (t, J = 6.8 Hz, 3 H), 1.17–
1.21 (m, 6 H), 1.25–1.38 (m, 1 H), 1.50–1.59 (m, 1 H), 2.16
(s, 3 H), 2.28 (dd, J = 4.4, 16.8 Hz, 1 H), 2.67 (dd, J = 10.0,
16.8 Hz, 1 H), 2.88–2.95 (m, 1 H), 3.58 (s, 3 H). 13C NMR
(CDCl3): d = 13.9, 22.3, 26.5, 29.5, 31.2, 31.7, 34.9, 47.9,
51.6, 172.9, 210.9. HRMS–EI: m/z [M+] calcd for C11H20O3:
200.1413; found: 200.1416. IR (KBr): 2932, 1739, 1714
cm–1. 3f: colorless oil. 1H NMR (CDCl3): d = 0.92 (d, J = 6.8
Hz, 6 H), 1.69–1.78 (m, 1 H,), 1.86–2.01 (m, 2 H), 2.22 (s, 3
H), 2.44 (dd, J = 4.8, 16.8 Hz, 1 H), 2.55–2.66 (m, 2 H), 2.81
(dd, J = 9.6, 16.8 Hz, 1 H), 2.99–3.06 (m, 1 H), 3.80–3.88
(m, 2 H), 7.15–7.31 (m, 5 H). 13C NMR (CDCl3): d = 19.0,
27.6, 29.5, 32.9, 33.1, 35.2, 47.5, 70.8, 126.2, 128.2, 128.5,
141.0, 172.3, 210.5. HRMS–EI: m/z [M+] calcd for
Hz, 2 H), 4.90 (dq, J = 1.6, 6.8 Hz, 1 H), 5.81 (q, J = 1.6 Hz,
1 H), 7.18–7.34 (m, 5 H). 13C NMR (CDCl3): d = 18.2, 29.5,
33.1, 80.4, 115.6, 126.7, 128.1, 128.7, 139.7, 172.9, 173.1.
HRMS–EI: m/z [M+] calcd for C13H14O2: 202.0994; found:
202.0996. IR (KBr): 2928, 1755, 1639 cm–1. 4b: colorless
oil. 1H NMR (CDCl3): d = 1.38 (d, J = 6.8 Hz, 3 H), 3.48 (dd,
J = 1.6, 16.8 Hz, 1 H), 3.68 (d, J = 16.8 Hz, 1 H), 4.86 (br q,
J = 6.8 Hz, 1 H), 5.59 (d, J = 1.6 Hz, 1 H), 7.10–7.30 (m, 5
H). 13C NMR (CDCl3): d = 18.3, 34.6, 79.9, 116.7, 127.3,
128.8, 129.0, 135.5, 172.6, 172.9. HRMS–EI: m/z [M+]
calcd for C12H12O2: 188.0837; found: 188.0834. IR (KBr):
2932, 1737, 1639 cm–1. 4c: colorless oil. 1H NMR (CDCl3):
d = 0.84 (t, J = 6.4 Hz, 3 H), 1.17–1.34 (m, 10 H), 1.38 (d,
J = 6.8 Hz, 3 H), 1.48–1.58 (m, 2 H), 2.16–2.37 (m, 2 H),
4.89 (dq, J = 1.6, 6.8 Hz, 1 H), 5.72 (d, J = 1.6 Hz, 1 H). 13
C
NMR (CDCl3): d = 14.0, 18.2, 22.5, 26.9, 27.9, 29.0, 29.1,
29.1, 31.7, 80.3, 114.8, 173.1, 174.5. HRMS–EI: m/z [M+]
calcd for C13H22O2: 210.1620; found: 210.1629. IR (KBr):
2927, 1755, 1639 cm–1. 4d: colorless oil. 1H NMR (CDCl3):
d = 0.84 (t, J = 7.2 Hz, 3 H), 1.26–1.31 (m, 4 H), 1.36 (d,
J = 6.8 Hz, 3 H), 1.49–1.57 (m, 2 H), 2.14–2.35 (m, 2 H),
4.87 (dq, J = 1.2, 6.8 Hz, 1 H), 5.70 (d, J = 1.6 Hz, 1 H). 13
C
NMR (CDCl3): d = 13.8, 18.2, 22.2, 26.5, 27.8, 31.3, 80.3,
114.8, 173.1, 174.5. HRMS–EI: m/z [M+] calcd for
C10H16O2: 168.1150; found: 168.1144. IR (KBr): 2932,
1754, 1638 cm–1. 5: colorless oil; diastereomeric mixture,
ratio = 2.3:1. 1H NMR (CDCl3, major diastereomer): d =
1.66 (s, 3 H), 2.05–2.25 (m, 2 H), 2.66 (s, 1 H), 2.79–2.96
(m, 2 H), 3.40 (s, 3 H), 4.18 (d, J = 2.8 Hz, 1 H), 4.50 (d, J =
2.8 Hz, 1 H), 7.18–7.32 (m, 5 H). 13C NMR (CDCl3, major
diastereomer): d = 24.0, 30.3, 44.4, 50.1, 73.9, 78.8, 80.8,
82.4, 123.1, 126.1, 128.4, 128.5, 141.0, 159.8. HRMS–EI:
m/z [M+] calcd for C16H18O3: 258.1256; found: 258.1258.
IR (KBr): 3287, 2117, 1687, 1052 cm–1.
C17H24O3: 276.1726; found: 276.1721. IR (KBr): 2962,
1733, 1160 cm–1. 4a: colorless oil. 1H NMR (CDCl3): d =
1.41 (d, J = 6.8 Hz, 3 H), 2.54–2.76 (m, 2 H), 2.92 (t, J = 8.0
Synlett 2007, No. 1, 63–66 © Thieme Stuttgart · New York

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