Regio- and stereoselective Au(I)-catalyzed intermolecular hydroalkoxylation of aryl allenes

Article abstract of DOI:10.1055/s-0028-1088158

In the presence of a catalytic amount of Ph₃PAuNO₃ and H₂SO₄, the hydroalkoxylation of allenes with alcohols has been shown to proceed smoothly and give allylic ethers in good yields and high regio- and stereoselectivity. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0028-1088158

LETTER
1103
Regio- and Stereoselective Au(I)-Catalyzed Intermolecular Hydroalkoxylation
of Aryl Allenes
A
u(I)-Catalyze
d
In
o
termolecular
n
H
ydroalkox
g
ylation of
A
r
-
yl
A
llen
M
es ei Cui,*a Ke-Rui Yu,a Chen Zhang*b
a
College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China
Fax +86(571)88208459; E-mail: cuidongmei@zjut.edu.cn
b
School of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, P. R. of China
Received 27 October 2008
reactions were run under solvent-free conditions. All pri-
mary alcohols could serve as good substrates to afford the
corresponding allylic alcohols (Table 2, entries 1, 2, 5,
and 7). Secondary and tertiary alcohols were also convert-
ed into the expected allylic ethers in good yields with per-
fect regio- and stereoselectivity (Table 2, entries 3, 4, 8,
11, 12, 15, 18). Benzyl alcohol also reacted efficiently
(Table 2, entry 6). Allenes with an electron-donating alkyl
group on the benzene ring gave good isolated yields of the
corresponding allylic ethers (Table 2, entries 9–15). With
a more electron-donating alkoxy group, the expected ad-
ducts were obtained in good yields (Table 2, entries 16–
20). In addition, the hydroalkoxylation of allene bearing
electron-withdrawing fluoro group on the benzene ring
with ethanol also took place smoothly to show similar
reactivity and selectivity (Table 2, entry 21). Hydroalkoxy-
lation of 1,3-disubstituted allene 1g gave the correspond-
ing product as a single stereoisomer in good yield (Table
2, entry 22).
Abstract: In the presence of a catalytic amount of Ph3PAuNO3 and
H2SO4, the hydroalkoxylation of allenes with alcohols has been
shown to proceed smoothly and give allylic ethers in good yields
and high regio- and stereoselectivity.
Key words: allenes, catalysis, alcohols, regioselectivity, stereo-
selectivity, hydroalkoxylation
Gold salts are powerful soft Lewis acids and readily pro-
mote reaction of unsaturated C–C bonds with a variety of
nucleophiles for the formation of carbon–carbon and car-
bon–heteroatom bonds.1–3 In the literature, a wide range
of metal-catalyzed intramolecular hydroalkoxylation of
allenes are known,4 but only a few examples of intermo-
lecular hydroalkoxylation of allenes have been dis-
closed.5–7 Recently, Widenhoefer6 and Yamamoto7
independently reported the utility of cationic Au(I)–N-
heterocyclic carbene or phosphine complex together with
AgOTf as catalysts for intermolecular hydroalkoxylation
of allenes. As part of our ongoing studies on metal-cata-
lyzed atom-economical reactions, we have been interested
in the use of gold compounds for simple and highly effi-
cient transformations.8 Herein we report that the Au(I)–
sulfuric acid systems can serve as powerful catalysts,
which promote the intermolecular hydroalkoxylation of
allenes with high regio- and stereoselectivity.
Table 1 Au-Catalyzed Hydroalkoxylation of Allenes 1a with Alco-
hols 2aa
Ph3PAuNO3
acidic promoter
MeOH
Ph
•
+
Ph
O
solvent free
1a
2a
3a
Entry
Ph3PAuNO3
(mol%)
H2SO4
(mol%)
Temp Time Yield
(%)b
The reaction of (propa-1,2-dienyl)benzene (1a, 0.5 mmol)
with methanol (2a, 0.6 mmol) in the presence of a catalyt-
ic amount of PPh3AuNO3 (2 mol%) and concentrated sul-
furic acid (5 mol%) at 40 °C proceeded efficiently to form
allylic ether 3a in 72% isolated yield with perfect regio-
and stereoselectivity (Table 1, entry 7). Other possible
isomers could not be detected. The reaction did not pro-
ceed in the absence of either the Au catalyst or sulfuric
acid (Table 1, entries 2 and 10). Decreasing the amount of
the Au catalyst or sulfuric acid resulted in a lower yield,
and the addition of a large amount of them did not affect
the reaction (Table 1, entries 5–8).
(°C)
70
40
70
40
40
40
40
40
70
40
(h)
20
20
20
9
1
2
0
5
5
5
5
5
2
1
2
0
0
0
0
0
3
0
0
4
20
5
69
5
3.5 70
6
2
8
4
52
7
5
72
To further assess the scope of this process, we have exam-
ined the hydroalkoxylation of different allenes with alco-
hols under the optimized conditions as indicated in entry
7 of Table 1. The results are summarized in Table 2.9 All
8
5
10
6
48
9
5
61
10
5
8
trace
a All reactions were performed with 0.5 mmol of 1a, 0.6 mmol of 2a,
0–5 mol% of Ph3PAuNO3, and 0–20 mol% of acid.
b Isolated yields.
SYNLETT 2009, No. 7, pp 1103–1106
Advanced online publication: 20.03.2009
DOI: 10.1055/s-0028-1088158; Art ID: W17208ST
x
x.
x
x.
2
0
0
9
© Georg Thieme Verlag Stuttgart · New York

1104
D.-M. Cui et al.
LETTER
Table 2 Au-Catalyzed Hydroalkoxylation of Allenes 1 with Alcohols 2a
R3
Ph3PAuNO3 (2 mol%)
R2
H2SO4 (5 mol%)
R1
•
R3 R2OH
+
R1
O
4 h, 40 °C
1
2
3
Entry
Allene
Alcohol
Product
Yield (%)b
1
2
3
4
5
6
MeOH
EtOH
i-PrOH
t-BuOH
n-C8H17OH
BnOH
3a
3b
3c
3d
3e
3f
72
77
81
78
79
82
Ph
•
1a
80
7
8
3g
3h
OH
OH
86
9
MeOH
EtOH
i-PrOH
t-BuOH
3i
83
85
85
85
10
11
12
3j
3k
3l
4-nBuC6H4
•
1b
13
14
15
MeOH
EtOH
i-PrOH
3m
3n
3o
93
99
93
4-nC5H11C6H4
•
1c
16
17
18
19
MeOH
EtOH
i-PrOH
BnOH
3p
3q
3r
3s
85
75
81
79
4-MeOC6H4
•
1d
4-EtOC6H4
•
20
21
EtOH
EtOH
3t
87
77
1e
3-FC6H4
•
3u
1f
OMe
OMe
OMe
MeO
MeO
•
22
MeOH
84
Br
Br
3v
1g
a All reactions were performed with 0.5 mmol of 1, 0.6 mmol of 2, 2 mol% of PPh3AuNO3, and 5 mol% of acid at 40 °C for 4 h.
b Isolated yields.
In conclusion, we have developed an efficient method that
uses PPh3AuNO3 and sulfuric acid that can catalyze the
intermolecular hydroalkoxylation of allenes with different
alcohols in good yields with high regio- and stereoselec-
tivity without solvent. Further studies are currently under
way in our laboratory.
Acknowledgment
This work was partially supported by the Natural Science Founda-
tion of China (No. 20672099, 20572094).
References and Notes
(1) Recent reviews, see: (a) Skouta, R.; Li, C.-J. Tetrahedron
2008, 64, 4917. (b) Shen, H. C. Tetrahedron 2008, 64,
3885. (c) Muzart, J. Tetrahedron 2008, 64, 3815.
(d) Hashmi, A. S. K. Chem. Rev. 2007, 107, 3180.
(e) Hashmi, A. S. K. Gold Bull. 2004, 37, 51. (f)Arcadi,A.;
Di Giuseppe, S. Curr. Org. Chem. 2004, 8, 795.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.
Synlett 2009, No. 7, 1103–1106 © Thieme Stuttgart · New York

LETTER
Au(I)-Catalyzed Intermolecular Hydroalkoxylation of Aryl Allenes
1105
(2) For examples, see: (a) Skouta, R.; Li, C. J. Angew. Chem.
Int. Ed. 2007, 46, 1117. (b) Dube, P.; Toste, F. D. J. Am.
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J. Am. Chem. Soc. 2006, 129, 2452. (h) Mézailles, N.;
Ricard, L.; Gagosz, F. Org. Lett. 2005, 7, 4133.
vacuo. The residue was purified by flash chromatography to
give the pure product.
(E)-1-Butyl-4-(3-methoxyprop-1-enyl)benzene (3i)
1H NMR (500 MHz, CDCl3): d = 7.30 (d, J = 8.5 Hz, 2 H),
7.12 (d, J = 8.5 Hz, 2 H), 6.57 (d, J = 16.0 Hz, 1 H), 6.23 (dt,
J = 16.0, 6.0 Hz, 1 H), 4.07 (dd, J = 6.0, 1.5 Hz, 2 H), 3.37
(s, 3 H), 2.58 (t, J = 7.5 Hz, 2 H), 1.60–1.56 (m, 2 H), 1.37–
1.32 (m, 2 H), 0.92 (t, J = 7.5 Hz, 3 H). 13C NMR (125 MHz,
CDCl3): d = 142.6, 134.1, 132.5, 128.6, 126.4, 124.9, 73.2,
57.9, 35.4, 33.5, 22.3, 13.9. IR: n = 2950, 2929, 2958, 1635,
1512, 1456, 1384, 1191, 1119, 968, 847, 553 cm–1. HRMS:
m/z calcd for C14H20O [M + 1+]; 205.1592; found: 205.1591.
(E)-1-Butyl-4-(3-ethoxyprop-1-enyl)benzene (3j)
1H NMR (500 MHz, CDCl3): d = 7.80 (d, J = 8.0 Hz, 2 H),
7.12 (d, J = 8.0 Hz, 2 H), 6.57 (d, J = 16.0 Hz, 1 H), 6.26 (dt,
J = 16.0, 6.0 Hz, 1 H), 4.12 (dd, J = 6.0, 1.5 Hz, 2 H), 3.54
(q, J = 7.0 Hz, 2 H), 2.59 (t, J = 7.5 Hz, 2 H), 1.60–1.55 (m,
2 H), 1.39–1.30 (m, 2 H), 1.24 (t, J = 7.0 Hz, 3 H), 0.92 (t,
J = 7.5 Hz, 3 H). 13C NMR (125 MHz, CDCl3): d = 142.5,
134.2, 132.3, 128.6, 126.4, 125.3, 71.4, 65.6, 35.4, 33.6,
22.4, 15.3, 14.0. IR: n = 2928, 1636, 1508, 1384, 1095, 526
cm–1. HRMS: m/z calcd for C15H22O [M+]: 218.1671; found:
218.1680.
(E)-1-Butyl-4-(3-isopropoxyprop-1-enyl)benzene (3k)
1H NMR (500 MHz, CDCl3): d = 7.29 (d, J = 8.0 Hz, 2 H),
7.11 (d, J = 8.0 Hz, 2 H), 6.55 (d, J = 16.0 Hz, 1 H), 6.26 (dt,
J = 16.0, 6.5 Hz, 1 H), 4.12 (dd, J = 6.5, 1.5 Hz, 2 H), 3.71–
3.63 (m, 1 H), 2.58 (t, J = 7.5 Hz, 2 H), 1.63–1.55 (m, 2 H),
1.37–1.30 (m, 2 H), 1.20 (d, J = 6.0 Hz, 6 H), 0.92 (t, J = 7.5
Hz, 3 H). 13C NMR (125 MHz, CDCl3): d = 142.5, 134.4,
131.9, 128.7, 126.5, 126.0, 70.9, 69.0, 35.5, 33.7, 22.5, 22.3,
14.1. IR: n = 2932, 1614, 1558, 1515, 1456, 1384, 1247,
1156, 1137, 1029, 810, 749, 551 cm–1. HRMS: m/z calcd for
C16H24O [M+]: 232.1827; found: 232.1830.
(E)-1-(3-tert-Butoxyprop-1-enyl)-4-butylbenzene (3l)
1H NMR (500 MHz, CDCl3): d = 7.29 (d, J = 8.0 Hz, 2 H),
7.10 (d, J = 8.0 Hz, 2 H), 6.57 (d, J = 16.0 Hz, 1 H), 6.25 (dt,
J = 16.0, 6.0 Hz, 1 H), 4.06 (dd, J = 6.0, 1.5 Hz, 2 H), 2.58
(t, J = 7.5 Hz, 2 H), 1.61–1.54 (m, 2 H), 1.36–1.31 (m, 2 H),
1.25 (s, 9 H), 0.92 (t, J = 7.5 Hz, 3 H). 13C NMR (125 MHz,
CDCl3): d = 142.2, 134.5, 131.2, 128.5, 126.6, 126.3, 73.3,
63.0, 35.4, 33.6, 27.7, 22.4, 14.0. IR: n = 2958, 2929, 2858,
1681, 1625, 1512, 1457, 1384, 1194, 1122, 969, 525 cm–1.
HRMS: m/z calcd for C17H26O [M+]: 246.1984; found:
246.1989.
(E)-1-(3-Methoxyprop-1-enyl)-4-pentylbenzene (3m)
1H NMR (500 MHz, CDCl3): d = 7.30 (d, J = 8.5 Hz, 2 H),
7.12 (d, J = 8.5 Hz, 2 H), 6.57 (d, J = 16.0 Hz, 1 H), 6.23 (dt,
J = 16.0, 6.0 Hz, 1 H), 4.06 (dd, J = 6.0, 1.5 Hz, 2 H), 3.37
(s, 3 H), 2.57 (t, J = 7.5 Hz, 2 H), 1.63–1.56 (m, 2 H), 1.34–
1.29 (m, 4 H), 0.88 (t, J = 7.0 Hz, 3 H). 13C NMR (125 MHz,
CDCl3): d = 142.6, 134.1, 132.5, 128.6, 126.4, 124.9, 73.2,
57.8, 35.6, 31.5, 31.1, 22.5, 14.0. IR: n = 2927,2855, 1634,
1384, 1124, 544 cm–1. HRMS: m/z calcd for C15H22O [M+]:
218.1671; found: 218.1665.
(i) Mézailles, N.; Ricard, L.; Gagosz, F. Org. Lett. 2005, 7,
4133.
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M. C.; Fischer, D.; Bats, J. W. Eur. J. Org. Chem. 2006,
1387. (g) Erdsak, J.; Krause, N. Synthesis 2007, 3741.
(h) Alcaide, B.; Almendros, P.; Martinez del Campo, T.
Angew. Chem. Int. Ed. 2007, 46, 6684. (i) Zhang, Z.; Liu,
C.; Kinder, R. E.; Han, X.; Qian, H.; Widenhoefer, R. A.
J. Am. Chem. Soc. 2006, 128, 9066. (j) Zhang, Z.;
Widenhoefer, R. A. Angew. Chem. Ind. Ed. 2007, 46, 283.
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2537. (l) Gockel, B.; Krause, N. Org. Lett. 2006, 8, 4485.
(m) Walkup, R. D.; Park, G. Tetrahedron Lett. 1987, 28,
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1585. (o) Yu, X.; Seo, S.-Y.; Marks, T. J. J. Am. Chem. Soc.
2007, 129, 7244.
(5) (a) Fukuda, Y.; Utimoto, K. J. Org. Chem. 1991, 56, 3729.
(b) Fukuda, Y.; Utimoto, K. JP 04095039, 1992; Chem.
Abstr. 1992, 117, 191330.
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(7) Nishina, N.; Yamamoto, Y. Tetrahedron Lett. 2008, 49,
1023.
(8) (a) Zhang, C.; Cui, D.-M.; Yao, L.-Y.; Wang, B.-S.; Hu,
Y.-Z.; Hayashi, T. J. Org. Chem. 2008, 73, 7811. (b) Cui,
D.-M.; Zheng, Z.-L.; Zhang, C. J. Org. Chem. 2009, 74,
1426. (c) Cui, D.-M.; Meng, Q.; Zheng, J.-Z.; Zhang, C.
Chem. Commun. 2009, DOI: 10.1039/b818863g.
(E)-1-(3-Ethoxyprop-1-enyl)-4-pentylbenzene (3n)
1H NMR (500 MHz, CDCl3): d = 7.29 (d, J = 8.0 Hz, 2 H),
7.10 (d, J = 8.0 Hz, 2 H), 6.57 (d, J = 16.0 Hz, 1 H), 6.25 (dt,
J = 16.0, 6.0 Hz, 1 H), 4.11 (dd, J = 6.0, 1.5 Hz, 2 H), 3.53
(q, J = 7.0 Hz, 2 H), 2.57 (t, J = 7.5 Hz, 2 H), 1.63–1.56 (m,
2 H), 1.33–1.30 (m, 4 H), 1.24 (t, J = 7.0 Hz, 3 H), 0.88 (t,
J = 7.0 Hz, 3 H). 13C NMR (125 MHz, CDCl3): d = 142.5,
134.2, 132.2, 128.6, 126.4, 125.3, 71.3, 65.6, 35.6, 31.5,
31.1, 22.5, 15.2, 14.0. IR: n = 2950, 2927, 2855, 1652, 1558,
1506, 1456, 1384, 1100, 968, 539 cm–1. HRMS: m/z calcd
for C16H24O [M+]: 232.1831; found: 232.1827.
(9) Typical Experimental Procedure
To a reactor containing allene (0.5 mmol), Ph3PAuNO3 (0.01
mmol), and alcohol (0.6 mmol) was added H2SO4 (0.025
mmol). The mixture was then sealed and stirred at 40 °C for
4 h. It was quenched with sat. soln of NaHCO3 and then
extracted with EtOAc (3 × 10 mL). The organic layer was
washed with brine, dried over Na2SO4, and concentrated in
Synlett 2009, No. 7, 1103–1106 © Thieme Stuttgart · New York

1106
D.-M. Cui et al.
LETTER
(E)-1-(3-Ethoxyprop-1-enyl)-3-fluorobenzene (3u)
(E)-1-(3-Isopropoxyprop-1-enyl)-4-pentylbenzene (3o)
1H NMR (500 MHz, CDCl3): d = 7.29 (d, J = 8.0 Hz, 2 H),
7.11 (d, J = 8.0 Hz, 2 H), 6.57 (d, J = 15.5 Hz, 1 H), 6.25 (dt,
J = 15.5, 6.0 Hz, 1 H), 4.12 (dd, J = 6.0, 1.5 Hz, 2 H), 3.71–
3.65 (m, 1 H), 2.57 (t, J = 7.5 Hz, 2 H), 1.63–1.56 (m, 2 H),
1.34–1.29 (m, 4 H), 1.20 (d, J = 6.0 Hz, 6 H), 0.88 (t, J = 7.0
Hz, 3 H). 13C NMR (125 MHz, CDCl3): d = 142.4, 134.3,
131.8, 128.5, 126.4, 125.8, 70.8, 68.8, 35.6, 31.5, 31.1, 22.5,
22.1, 14.0. IR: n = 2950, 2927, 2856, 1633, 1384, 1123,
1070, 965, 544 cm–1. HRMS: m/z calcd for C17H26O [M+]:
246.1984; found: 246.1981.
1H NMR (500 MHz, CDCl3): d = 7.28–7.24 (m, 1 H), 7.15–
7.13 (m, 1 H), 7.10–7.06 (m, 1 H), 6.94–6.90 (m, 1 H), 6.58
(d, J = 16.0 Hz, 1 H), 6.30 (dt, J = 16.0, 6.0 Hz, 1 H), 4.14
(dd, J = 6.0, 1.5 Hz, 2 H), 3.56 (q, J = 7.0 Hz, 2 H), 1.25 (t,
J = 7.0 Hz, 3 H). 13C NMR (125 MHz, CDCl3): d = 163.1 (d,
J = 243.8 Hz), 139.2 (d, J = 8.8 Hz), 130.8, 129.9 (d, J = 8.8
Hz), 127.8, 122.3, 114.3 (d, J = 21.3 Hz), 112.9 (d, J = 21.3
Hz), 70.9, 65.9, 15.2. IR: n = 2995, 1770, 1759, 1635, 1834,
1246, 1058, 913, 743, 526 cm–1. HRMS: m/z calcd for
C11H13FO [M+]: 180.0950; found: 180.0946.
(E)-1-(3-Isopropoxyprop-1-enyl)-4-methoxybenzene (3r)
1H NMR (500 MHz, CDCl3): d = 7.33–7.31 (m, 2 H), 6.85–
6.83 (m, 2 H), 6.54 (d, J = 15.5 Hz, 1 H), 6.17 (dt, J = 15.5,
6.0 Hz,1 H), 4.11 (dd, J = 6.0, 1.5 Hz, 2 H), 3.80 (s, 3 H),
3.71–3.65 (m, 1 H), 1.20 (d, J = 6.0 Hz, 6 H). 13C NMR (125
MHz, CDCl3): d = 159.2, 131.5, 129.7, 127.6, 124.6, 113.9,
70.8, 68.9, 55.3, 22.2. IR: n = 2872, 1634, 1558, 1491, 1407,
1384, 1088, 1038, 1013, 937, 804, 485 cm–1. HRMS: m/z
calcd for C13H18O [M + 1+]: 207.1385; found: 207.1385.
(E)-1-Bromo-3,4-dimethoxy-2-(3-methoxybut-1-enyl)-
benzene (3v)
1H NMR (500MHz, CDCl3): d = 7.29 (d, J = 8.5 Hz, 2 H),
6.70 (d, J = 8.5 Hz, 2 H), 6.48 (d, J = 16.0 Hz, 1 H), 6.14 (dd,
J = 16.0, 7.5 Hz, 1 H), 3.95–3.90 (m, 1 H), 3.86 (s, 3 H), 3.75
(s, 3 H), 3.38 (s, 3 H), 1.36 (dd, J = 6.5, 2.5 Hz, 3 H).
13C NMR (125 MHz, CDCl3): d = 152.6, 148.1, 138.8,
131.2, 128.1, 125.9, 114.6, 112.1, 78.7, 60.1, 56.2, 56.0,
21.6. IR: n = 2928, 1636, 1508, 1384, 1095, 526 cm–1.
HRMS: m/z calcd for C13H17BrO3 [M+]: 300.0361; found:
300.0341.
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