Cationic gold-catalyzed regioselective hydration of 1-arylalkynes through carbonyl group participation

Article abstract of DOI:10.1055/s-0031-1290619

The unsymmetrically substituted internal alkynes were regioselectively hydrated through carbonyl-group participation using cationic gold catalyst where the nature and position of carbonyl functionalities play a key role in governing the regioselectivity o

Full text of DOI:10.1055/s-0031-1290619

LETTER
897
Cationic Gold-Catalyzed Regioselective Hydration of 1-Arylalkynes through
Carbonyl Group Participation
R
egioselec
i
tive
H
s
e
f
1-Arylalk
o
ynes n Jeong, Devalina Ray, Chang Ho Oh*
Department of Chemistry, Hanyang University, Sungdong-Gu, Seoul 133-791, Korea
Fax +82(2)22990762; E-mail: changho@hanyang.ac.kr
Received 19 November 2011
efficient methodology. Herein we report an operationally
Abstract: The unsymmetrically substituted internal alkynes were
regioselectively hydrated through carbonyl-group participation us-
ing cationic gold catalyst where the nature and position of carbonyl
functionalities play a key role in governing the regioselectivity of
simple, efficient, and nonhazardous method for the regio-
selective hydration of internal alkynes in substituted 1-
arylalkynes to obtain regioselectively hydrated products
products as well as facilitating the reaction. A new atom-economi- in good to excellent yield.
cal, cationic gold-catalyzed regioselective hydration of 1-aryl-
alkynes substituted with various functionalities in the absence of
The initial attempt to hydrate internal alkynes was carried
out with the ortho-alkynylaryl aldehyde 1a as substrate
which has been repeatedly used in our lab previously for
the gold-catalyzed cyclization to obtain fused substituted
cycloheptanones.11 The reaction conditions for the regio-
selective hydration were optimized with substrate 1a by
screening various metal catalysts in different solvents at
varying temperature and time in the presence of water
(Table 1). The amount of water was found to be crucial in
dictating the product. PtCl2 mostly facilitated cyclization
resulting in the products 1c and 1d, rather than alkyne hy-
dration in toluene with excess water both at room temper-
ature as well as elevated temperature. Although the
change in solvent from toluene to 1,4-dioxane was able to
provide the desired hydrated product 1b in 46% yield, but
the decrease in the amount of water from 20 equivalents
to 10 equivalents in the reaction led to the cyclized prod-
uct 1c even in 1,4-dioxane. Improved yields of hydrated
products resulted when platinum was replaced with gold
catalysts. AuBr3 alone was found to be effective in re-
gioselective hydration of internal alkynes. Most striking
observation directing to remarkable yield of the regiose-
lectively hydrated product was achieved when the catalyt-
ic system AuCl(PPh3)–AgOTf was used in 1,4-dioxane.
This led to the formation of 1b in 87% yield at room tem-
perature in two hours. The change of AgOTf to AgSbF6
resulted in the declination of product yield from 87% to
70% while the removal of silver from the catalytic system
led to total recovery of starting material after two hours
(Table 1, entry 8). Delighted and enlightened with the op-
timized outcome, we proceeded further with various other
similar substrates.
any toxic catalyst, strong acid, or other additives have been report-
ed.
Key words: catalysis, regioselectivity, internal alkynes, hydration
The alkyne hydration reaction, leading to the formation of
carbonyl derivatives, is of prime interest considering the
wide availability of alkynyl substrates and the fundamen-
tal importance of the carbonyl motif in modern organic
synthesis.1 Although this reaction has been known since
the 19th century, its potential in organic synthesis and in-
dustrial processes has yet to be fully exploited.2,3 Tradi-
tional alkyne hydration suffers drawback regarding harsh
reaction conditions such as the use of toxic catalysts as
well as strong and dangerous reagents (H2SO4, BF3).4
Until recent date, several groups attempted atom-econom-
ic approach toward hydration of terminal alkynes result-
ing in excellent selectivity while regioselective hydration
of internal alkynes still remains a challenge to be explored
further. Carriedo and co-workers developed the Au-cata-
lyzed hydration of a terminal alkyne5 in the presence of
H2SO4 at high temperature whereas Leyva developed a
progressive Au-catalyzed hydration at room temperature
in the absence of acidic cocatalysts.6
A major drawback associated with the hydration of an in-
ternal alkyne is the lack of regioselectivity resulting in a
mixture of ketones.7 Tanaka et al. reported the Au–acid
cocatalyzed hydration of internal alkynes leading to a
mixture of ketones.8 A recent report by Nolan described
the Au–acid co-catalyzed hydration of symmetrical inter-
nal alkynes.9 According to Kaspar, hydroamination of an
unsymmetrically substituted internal alkyne can regio-
selectively give an anti-Markovnikov ketone.10 There are
rare reports on mild and regioselective hydration of an in-
ternal alkyne which inspired us for the investigation of ap-
propriate reaction conditions in order to develop an
The regioselective hydration of internal alkynes in general
needs a directing group nearby which helps in the forma-
tion of cyclic intermediate followed by nucleophilic at-
tack with water. In this context, we proposed that the triple
bond in 1-arylalkene substrates S may be activated by a
metal catalyst forming intermediate B. The nearby oxygen
from carbonyl functionality can act as nucleophile and at-
tack the metal-activated alkyne to form either a five- or
six-membered ring intermediate C or D via 5-exo- or 6-
endo-dig mode of cyclization. Subsequent attack by water
SYNLETT 2012, 23, 897–902
x
x.
x
x.
2
0
1
2
Advanced online publication: 15.03.2012
DOI: 10.1055/s-0031-1290619; Art ID: U68811ST
© Georg Thieme Verlag Stuttgart · New York

898
J. Jeong et al.
LETTER
Table 1 Optimization of Reaction Conditions for the Regioselective Hydration of Substituted ortho-Alkynylaryl Aldehyde 1a
OH
O
O
O
O
+
+
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
O
EtO2C
CO2Et
1a
1b
1c
1d
Entry
Catalyst
(mol%)
Additive (
mol%)
H2O
(equiv)
Solvent
Temp
(°C)
Time
Yield of 1b Yield of 1c Yield of 1d
(h)
18
2
(%)a
(%)a
20
30
–
(%)a
15
27
–
1
2
3
4
5
6
7
8
PtCl2 (5)
PtCl2 (5)
PtCl2 (5)
PtCl2 (5)
–
20
20
20
10
3
toluene
toluene
25
80
25
60
25
25
25
25
–
–
–
–
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
1,4-dioxane
2
46
–
–
2
39
–
–
AuCl(PPh3) (1)
AuCl(PPh3) (1)
AuBr3 (5)
AgOTf (1)
2
87
70
76
–
–
AgSbF6 (1)
3
2
–
–
–
–
5
2
–
–
AuCl(PPh3) (2)
5
2
–
–
a Yields were determined by 1H NMR integration.
at the carbonyl center may afford the internediates E and
F.
O
The ring opening of particularly six-membered-ring inter-
mediate F to form intermediate H may have finally result-
ed in the regioselective formation of 1,5-dicarbonyl
compound P2 which was found in the case of ortho-alky-
nylaryl aldehydes (Scheme 1).
S
R
To test this hypothesis, we compared the reactivity of in-
ternal alkynes bearing a carbonyl functionality (1a and
3a) with that of the substrate lacking it (2a, Table 2). The
substrate 2a (Table 2) lacking carbonyl functionality
failed to react at all under the optimized reaction condi-
tions even after 24 hours at room temperature which was
fully in agreement with the proposed hypothesis where
neighboring-group participation was mandatory and sup-
posed to be the driving force for the reaction. Thus, the
substrate 1a yielded 87% of the product 1b. However, the
product 3c obtained from alkyne 3a bearing a keto func-
tionality was found to have altered regioselectivity as
compared to that obtained from ortho-alkynylaryl alde-
hyde 1a. Further, numerous internal alkyne substrates 4a–
7a containing various carbonyl functionalities apart from
aldehydes and ketones were screened (Table 3). The
alkyne substrate with hydroxy functionality 8a was also
tested out of curiosity and found to furnish cyclized prod-
uct 8b. With the substrate 4a containing a carbonate func-
tionality, the formation of hydrated product was
comparatively much slower and resulted in 50% yield of
the desired ketone derivative 4b in 24 hours at room tem-
perature. The homologated carbonate substrate 5a, when
subjected to the Au–Ag co-catalyzed reaction, did not af-
ford the hydrated product, and instead the entire starting
material was recovered even after 24 hours.
H2O
H2O
O+
O
5-exo-dig
6-endo-dig
R
+
O
R
R
R
AuI
–AuI
–
R
AuI
B
D
C
OH
OH
O
O
O
O
–
R
–AuI
O
AuI
F
E
R
R
P2
O
H2O
O
H2O
O
P1
OH
OH
–
R
AuI
– AuI
H
G
Scheme 1 Plausible mechanism for the regioselective hydration of
1-arylalkynes S assisted by a carbonyl functionality
Synlett 2012, 23, 897–902
© Thieme Stuttgart · New York

LETTER
Regioselective Hydration of 1-Arylalkynes
899
Table 2 Comparative Study of Hydration of Internal Alkynes with
The same trend of reactivity was observed with the corre-
sponding OAc-substituted alkyne 6a where the C=O func-
tionality of the OAc group was unable to initiate the
reaction through neighboring-group participation. The
probable reason for inertness of substrates 5a and 6a to-
ward hydration reaction can be the requirement of inter-
mediate ring formation through neighboring-group
participation which may be unfavorable in this case. The
ester-substituted internal alkyne 7a was found to be reac-
tive enough to produce a mixture of hydrated and cyclized
products 7b and 7c in almost 1:1 ratio in two hours at
room temperature. In the literature, 3-alkynoates and 2-
alkynoates are reported to afford g- and b-keto esters regio-
selectively through neighboring carbonyl-group partici-
pation,12 the facile cyclization leading to the formation of
a six-membered ring is also possible in addition to hydra-
tion, which results in the formation of significant amount
of cyclized product 7c along with the hydrated product 7b.
The substrate 8a underwent cyclization much more rapid-
ly than hydration leading to the formation of substituted
furan derivative 8b in 68% yield.13 Thus it was obvious
that the ortho-alkynylaryl aldehydes among all other 1-
arylalkyne substrates underwent an efficient, clean, and
fast hydration resulting in the regioselective formation of
the desired hydrated products in good to excellent yields.
and without Aldehyde and Ketone Functionalitiesa
R
O
CO2Et
R
CO2Et
1b–3b
+
CO2Et
CO2Et
R
1a–3a
CO2Et
CO2Et
O
1c–3c
Entry
R
Time (h) Product
Yield (%)b
1
2
3
1a CHO
2a H
2
24
2
1b
87
–
n.r.c
3a COMe
3c
85
a Substrate (0.30 mmol), Au(PPh3)Cl (1 mol%), AgOTf (1 mol%),
H2O (1.0 mmol), 1,4-dioxane, r.t.
b Isolated yield.
c n.r. = no reaction.
Table 3 Hydration of Internal Alkynes Bearing Various Functionalitiesa
Entry
Substrates
Time (h)
24
Product
Yield (%)b
OCO2Me
OCO2Me
1
50
O
4a
5a
4b
OCO2Me
2
3
24
24
n.r.c
–
–
OAc
n.r.c
CO2Et
CO2Et
6a
CO2Et
CO2Et
CO2Et
CO2Et
O
7b
44
39
4
2
CO2Et
CO2Et
O
7a
O
CO2Et
CO2Et
7c
© Thieme Stuttgart · New York
Synlett 2012, 23, 897–902

900
J. Jeong et al.
LETTER
Table 3 Hydration of Internal Alkynes Bearing Various Functionalitiesa (continued)
Entry
5
Substrates
Time (h)
Product
Yield (%)b
OH
O
2
68
CO2Et
CO2Et
EtO2C CO2Et
8b
8a
a Substrate (0.3 mmol), Au(PPh3)Cl (1 mol%), AgOTf (1 mol%), H2O (1.0 mmol), 1,4-dioxane, r.t.
b Isolated yield.
c n.r. = no reaction.
The developed methodology was further illustrated with a sired hydrated product 13b in 74% yield. Although 14a
number of ortho-alkynylaryl aldehydes to prove its gener- afforded the corresponding ketone product 14b in some-
ality as described in Table 4. The simple internal alkyne what lower yield (58%) but the substrates 15a and 16a af-
9a with alkyl side chain afforded the desired ketone com- forded the desired products 15b and 16b in better yields.
pound 9b in 51% yield after two hours at room tempera- When the substrate 17a containing two alkyne functional-
ture while the substrate 10a with substituted alkene side ities was subjected to the hydration reaction, the regiose-
chain afforded 50% of product 10b. The hydration reac- lective product 17b was formed in good yield where the
tion of substrate 11a where the side chain is substituted alkyne close to the aldehyde functionality was specifically
with diester functionality afforded the product 11b in 63% hydrated leaving the other alkyne intact. Thus the method-
yield. When the substituent on the side chain possesses an ology has been found to work efficiently with a wide
OTBS functionality, a maximum yield of 95% of the de- range of substrates retaining its generality.
sired ketone product 12b was obtained. The O-benzyl-
substituted pyridine substrate 13a also afforded the de-
Table 4 Regioselective Alkyne Hydration of Various ortho-Alkynylaryl Aldehydesa
Entry
Substrates
Products
Yield (%)b
CHO
CHO
1
51
O
9a
9b
O
O
2
50
O
O
10a
10b
CHO
CHO
3
4
63
95
CO2Et
CO2Et
CO2Et
CO2Et
11a
11b
F
CHO
F
CHO
TBSO
Ph
N
OTBS
Ph
N
O
12a
12b
Synlett 2012, 23, 897–902
© Thieme Stuttgart · New York

LETTER
Regioselective Hydration of 1-Arylalkynes
901
Table 4 Regioselective Alkyne Hydration of Various ortho-Alkynylaryl Aldehydesa (continued)
Entry
5
Substrates
Products
Yield (%)b
F
CHO
F
CHO
BnO
N
74
BnO
N
CO2Et
CO2Et
CO2Et
CO2Et
O
13a
13b
F
CHO
F
CHO
6
7
58
71
N
N
N
N
O
14a
15a
14b
F
CHO
F
CHO
N
N
F
N
N
F
CO2Et
CO2Et
CO2Et
CO2Et
O
15b
CHO
CHO
N
N
O
8
9
75
68
16a
17a
16b
F
CHO
F
CHO
N
N
CO2Et
CO2Et
N
N
CO2Et
CO2Et
O
17b
a Substrate (0.3 mmol), Au(PPh3)Cl (1 mol%), AgOTf (1 mol%), H2O (1.0 mmol), 1,4-dioxane, 2 h, r.t.
b Isolated yield.
7.49–7.55 (m, 2 H), 7.80 (d, 1 H, J = 7.2 Hz), 9.99 (s, 1 H). 13C
NMR (100 MHz, CDCl3): d = 14.0, 29.1, 32.3, 45.1, 47.8, 55.3,
61.6, 115.2, 127.9, 132.9, 133.8, 134.2, 135.3, 135.4, 137.7, 170.8,
193.3, 203.9.
In conclusion, we have developed a new, convenient,
atom-economic, and mild method toward the regioselec-
tive hydration of 1-arylalkynes in the presence of gold cat-
alysts where the use of toxic strong acid or other additives
can be avoided. A series of internal alkynes having di-
verse carbonyl functionalities were screened for the effec-
tive hydration which can be further explored and utilized
in near future. The developed method is efficient enough
to be applied to a wide range of substituted alkynes show-
ing tolerance toward numerous functionalities.
1
Compound 1c: H NMR (400 MHz, CDCl3): d = 1.23–1.29 (m, 6
H), 1.47–1.57 (m, 1 H), 2.04–2.14 (m, 1 H), 2.19–2.27 (m, 1 H)
2.45–2.49 (m, 1 H), 2.57–2.65 (m, 2 H), 2.79–2.85 (m, 1 H), 3.06–
3.10 (m, 1 H), 4.16–4.25 (m, 4 H), 5.69–5.67 (m, 1 H), 7.51–7.55
(m, 2 H), 7.65–7.71 (m, 1 H), 7.88 (d, 1 H, J = 7.2 Hz). 13C NMR
(100 MHz, CDCl3): d = 13.9, 29.8, 30.2, 36.0, 45.7, 46.0, 57.8, 61.9,
80.4, 121.9, 125.5, 125.7, 129.2, 134.2, 150.2, 170.0, 170.3, 207.5.
1
Compound 3b: H NMR (400 MHz, CDCl3): d = 1.25 (t, 6 H,
J = 7.2 Hz), 2.00 (m, 4 H), 2.36–2.41 (m, 2 H), 2.55 (s, 3 H), 2.74–
2.78 (m, 2 H), 4.19 (q, 4 H, J = 6.8 Hz), 4.96 (d, 1 H, J = 10.0 Hz),
5.04 (d, 1 H, J = 17.2 Hz), 5.73–5.81 (m, 1 H), 7.45–7.47 (m, 1 H),
7.51–7.57 (m, 2 H), 7.64–7.66 (m, 1 H). 13C NMR (100 MHz,
CDCl3): d = 14.0, 26.9, 28.1, 28.3, 32.5, 36.9, 56.6, 61.2, 115.0,
127.1, 128.3, 130.5, 131.6, 137.5, 138.1, 140.4, 171.3, 200.5, 203.8.
The substrate (0.3 mmol) was dissolved in distilled 1,4-dioxane (1.0
mL) in a test tube and treated with catalysts (1–3 mol%). Water (1.0
mmol) was incorporated with a microsyringe. After a quick purge
of argon gas, the reaction mixtures were stirred for 1–24 h either at
r.t. or preheated oil bath (60–80 °C) as given conditions. Upon com-
pletion of the reaction (as indicated by TLC), the solvent was re-
moved under vacuum, and flash column chromatography of the
residue afforded the pure products.
1
Compound 4b: H NMR (400 MHz, CDCl3): d = 0.87 (t, 3 H,
J = 7.2 Hz), 1.24–1.35 (m. 2 H), 1.51–1.58 (m, 2 H), 2.44 (t, 2 H,
J = 7.6 Hz), 3.66 (s, 2 H), 3.90 (s, 3 H), 7.20–7.26 (m, 3 H), 7.29–
7.34 (m, 1 H). 13C NMR (100 MHz, CDCl3): d = 13.8, 22.2, 25.8,
41.8, 44.4, 55.5, 122.0, 126.4, 126.8, 128.4, 131.5, 149.4, 153.8,
207.3.
Spectral Data of Compounds
1
Compound 1b: H NMR (400 MHz, CDCl3): d = 1.23 (t, 6 H,
J = 7.0 Hz), 2.05–2.11 (m, 4 H), 3.37 (s, 2 H), 4.14–4.19 (m, 6 H),
4.95–5.06 (m, 2 H), 5.70–5.83 (m, 1 H), 7.22 (d, 1 H, J = 6.4 Hz),
© Thieme Stuttgart · New York
Synlett 2012, 23, 897–902

902
J. Jeong et al.
LETTER
1
1
Compounds 7b and 7c (inseparable mixture): H NMR (400 MHz,
CDCl3): d = 1.21–1.28 (m, 12 H), 1.35 (t, 3 H, J = 7.2 Hz), 1.98–
2.15 (m, 8 H), 3.19 (s, 2 H), 3.31 (s, 2 H), 4.10 (s, 2 H), 4.14–4.31
(m, 10 H), 4.93–5.08 (m, 4 H), 5.73–5.82 (m, 2 H), 6.3 (s, 1 H), 7.18
(d, 1 H, J = 7.6 Hz), 7.32–7.36 (m, 2 H), 7.44–7.49 (m, 2 H), 7.66–
7.69 (m, 1 H), 8.01–8.03 (m, 1 H), 8.23 (d, 1 H, J = 8.4 Hz). 13C
NMR (100 MHz, CDCl3): d = 14.0, 28.5, 28.9, 31.5, 32.0, 36.5,
44.2, 48.9, 55.1, 56.8, 60.8, 61.4, 61.7, 106.1, 114.9, 115.4, 125.3,
127.3, 128.2, 129.6, 130.9, 132.29, 132.6, 134.7, 136.3, 136.9,
137.1, 137.7, 153.2, 161.9, 166.8, 170.4, 170.7, 204.2.
Compound 16b: H NMR (400 MHz, CDCl3): d = 0.92 (t, 3 H,
J = 7.2 Hz), 1.25–1.45 (m, 2 H), 1.57–1.69 (m, 2 H), 2.67 (t, 2 H,
J = 7.6 Hz), 4.37 (s, 2 H), 7.26–7.43 (m, 3 H), 7.64–7.61 (m, 2 H),
7.88 (d, 1 H, J = 8.0 Hz), 9.99 (s, 1 H). 13C NMR (100 MHz,
CDCl3): d = 13.8, 22.3, 25.6, 42.9, 49.5, 82.5, 98.9, 121.2, 125.3,
125.5, 128.5, 129.9, 132.2, 135.9, 136.0, 152.1, 157.9, 160.5, 189.2,
206.1.
1
Compound 17b: H NMR (400 MHz, CDCl3): d = 1.22 (t, 6 H,
J = 7.2 Hz), 1.66–1.70 (m, 6 H), 1.74 (t, 3 H, J = 2.4 Hz), 2.91 (d, 2
H, J = 2.0 Hz), 3.45 (s, 2 H), 3.75–3.76 (m, 4 H), 4.15–4.20 (m, 6
H), 7.52 (d, 1 H, J = 14.4 Hz), 9.79 (s, 1 H). 13C NMR (100 MHz,
CDCl3): d = 3.5, 13.9, 23.6, 24.7, 26.1, 44.7, 48.1, 49.6, 54.8, 61.8,
73.8, 78.9, 120.9, 124.5, 124.7, 169.3, 187.9, 203.8.
1
Compound 8b: H NMR (400 MHz, CDCl3): d = 1.25 (t, 6 H,
J = 7.4 Hz), 1.66–1.67 (m, 4 H), 1.98–2.02 (m, 6 H), 2.18–2.22 (m,
2 H), 2.39–2.51 (m, 4 H), 4.18 (q, 4 H, J = 7.2 Hz), 4.96–5.05 (m, 2
H), 5.75–5.79 (m, 1 H), 7.02 (s, 1 H). 13C NMR (100 MHz, CDCl3):
d = 14.1, 20.2, 20.3, 21.4, 23.3, 23.4, 28.4, 30.7, 31.6, 50.9, 61.2,
115.1, 116.0, 122.1, 135.0, 137.6, 148.0, 171.3.
Acknowledgment
Compound 9b: 1H NMR (400 MHz,CDCl3): d = 0.92 (t, 3 H J = 7.4
Hz), 1.35 (q, 2 H, J = 7.2 Hz), 1.62 (quint, 2 H, J = 7.6 Hz), 2.62 (t,
2 H, J = 7.6 Hz), 4.13 (s, 2 H), 7.22 (d, 1 H, J = 7.2 Hz), 7.48–7.57
(m, 2 H), 7.81 (d, 1 H, J = 7.6 Hz), 10.02 (s, 1 H). 13C NMR (100
MHz, CDCl3): d = 14.0, 22.4, 25.9, 42.6, 47.6, 127.6, 127.7, 132.7,
133.8, 135.2, 193.4, 207.5.
Financial support was provided by a grant from the National Re-
search Foundation of Korea (NRF 3|201000000001991) for finan-
cial support and BK21 for fellowships.
References
1
Compound 10b: H NMR (400 MHz, CDCl3): d = 0.98 (s, 6 H),
(1) Otera, J. Modern Carbonyl Chemistry; Wiley-VCH:
Weinheim, 2000.
(2) Kutscheroff, M. Chem. Ber. 1884, 17, 13.
1.26–1.30 (m, 2 H), 1.53–1.57 (m, 2 H), 2.59 (t, 2 H, J = 7.2 Hz),
4.11 (s, 2 H), 4.88–4.92 (m, 2 H), 5.72–5.79 (m, 1 H), 7.21 (d, 1 H,
J = 7.2 Hz), 7.47–7.57 (m, 2 H), 7.81 (d, 1 H, J = 7.4 Hz), 10.01 (s,
1 H). 13C NMR (100 MHz, CDCl3): d = 19.0, 26.8, 36.7, 42.2, 43.5,
47.6, 110.6, 127.8, 132.8, 133.8, 134.4, 135.3, 136.2, 148.3, 193.5,
207.4.
(3) Jung, H. H.; Floreancig, P. E. Org. Lett. 2006, 8, 1949.
(4) (a) Kutscheroff, M. G. Chem. Ber. 1909, 42, 2759.
(b) Hennion, G. F.; Killian, D. B.; Vaughn, T. H.;
Nieuwland, J. A. J. Am. Chem. Soc. 1934, 56, 1130.
(c) Nieuwland, J. A.; Vogt, R. R.; Foohey, W. L. J. Am.
Chem. Soc. 1930, 52, 1018. (d) Killian, D. B.; Hennion,
G. F.; Nieuwland, J. A. J. Am. Chem. Soc. 1934, 56, 1786.
(e) Killian, D. B.; Hennion, G. F.; Nieuwland, J. A. J. Am.
Chem. Soc. 1936, 58, 80. (f) Kremsner, J. M.; Kappe, C. O.
Eur. J. Org. Chem. 2005, 3672.
(5) Carriedo, G. A.; López, S.; Suárez-Suárez, S.; Presa-Soto,
D.; Presa-Soto, A. Eur. J. Inorg. Chem. 2011, 1442.
(6) Leyva, A.; Corma, A. Org. Chem. 2009, 74, 2067.
(7) (a) Carey, F. A.; Sundberg, R. Reactions and Synthesis, In
J. Advanced Organic Chemistry, Part B, 5th ed.; Springer:
Berlin, 2007, 335. (b) Nishizawa, M.; Takemoto, T.; Sasaki,
I.; Nakano, M.; Ho, E.; Namba, K.; Yamamoto, H.;
Imagawa, H. Synlett 2009, 1175. (c) Imi, K.; Imai, K.;
Utimoto, K. Tetrahedron Lett. 1987, 28, 3127.
(d) Chevallier, F.; Breit, B. Angew. Chem. Int. Ed. 2006, 45,
1599. (e) Ogo, S.; Uehara, K.; Abura, T.; Watanabe, Y.;
Fukuzumi, S. J. Am. Chem. Soc. 2004, 126, 16520.
(f) Grotjahn, D. B.; Incarvito, C. D.; Rheingold, A. L.
Angew. Chem. Int. Ed. 2001, 40, 3884. (g) Grotjahn, D. B.;
Lev, D. A. J. Am. Chem. Soc. 2004, 126, 12232.
(h) Rajaram, A. R.; Pu, L. Org. Lett. 2006, 8, 2019.
(i) Bras, G. L.; Provot, O.; Peyrat, J.; Alami, M.; Brion, J.
Tetrahedron Lett. 2006, 47, 5497.
1
Compound 11b: H NMR (400 MHz, CDCl3): d = 1.23 (t, 6 H,
J = 7.0 Hz), 2.79 (d, 2 H, J = 7.2 Hz), 3.34 (s, 2 H), 4.13–4.19 (m,
6 H), 5.12 (d, 2 H, J = 12.0 Hz), 5.68–5.76 (m, 2 H), 7.21 (d, 1 H,
J = 7.2 Hz), 7.49–7.55 (m, 2 H), 7.80 (d, 1 H, J = 6.0 Hz), 9.99 (s,
1 H). 13C NMR (100 MHz, CDCl3): d = 14.1, 37.6, 44.9, 47.9, 55.3,
61.7, 119.6, 127.9, 132.9, 133.1, 133.8, 134.3, 135.3, 135.5, 170.4,
193.3, 203.9.
1
Compound 12b: H NMR (400 MHz, CDCl3): d = 0.89 (s, 9 H),
1.51–1.55 (m, 2 H), 1.66–1.72 (m, 2 H), 2.67 (t, 2 H, J = 7.6 Hz),
4.09–4.13 (m, 1 H), 4.38 (s, 2 H), 5.03 (d, 1 H, J = 10.4 Hz), 5.14
(d, 1 H, J = 17.2 Hz), 5.74–5.83 (m, 1 H), 7.49–7.52 (m, 3 H), 7.91
(d, 1 H, J = 10.8 Hz), 8.04–8.06 (m, 2 H), 10.04 (s, 1 H). 13C NMR
(100 MHz, CDCl3): d = 18.4, 19.5, 26.0, 37.5, 43.3, 49.9, 73.7,
114.0, 127.1, 127.3, 128.7, 129.1, 129.4, 129.5, 129.9, 130.5, 130.8,
134.3, 134.3, 141.5, 151.6, 151.6, 155.4, 158.0, 189.9, 206.4.
1
Compound 13b: H NMR (400 MHz, CDCl3): d = 1.24 (t, 6 H,
J = 7.2 Hz), 2.01–2.04 (m, 2 H), 2.10–2.12 (m, 2 H), 3.33 (s, 2 H),
4.18 (q, 4 H, J = 7.6 Hz), 4.26 (s, 2 H), 4.97 (d, 1 H, J = 9.6 Hz),
5.02 (d, 1 H, J = 17.2 Hz), 5.52 (s, 2 H), 5.73–5.80 (m, 1 H), 7.34–
7.47 (m, 5 H), 7.75 (d, 1 H, J = 9.6 Hz), 9.91 (s, 1 H). 13C NMR (100
MHz, CDCl3): d = 14.1, 29.2, 32.6, 45.5, 49.6, 55.5, 61.8, 69.2,
115.4, 125.2, 125.4, 128.5, 128.5, 128.7, 135.9, 137.5, 170.7, 189.0,
203.0.
(8) Mizushima, E.; Sato, K.; Hayashi, Y.; Tanaka, M. Angew.
Chem. Int. Ed. 2002, 41, 4563.
1
Compound 14b: H NMR (400 MHz, CDCl3): d = 0.91 (t, 3 H,
J = 7.4 Hz), 1.32–1.36 (m, 2 H), 1.57–1.71 (m, 8 H), 2.58 (t, 2 H,
J = 7.4 Hz), 3.73–3.75 (m, 4 H), 4.11 (s, 2 H), 7.52 (d, 1 H, J = 14.0
Hz), 9.79 (s, 1 H). 13C NMR (100 MHz, CDCl3): d = 14.0, 22.4,
24.8, 25.9, 26.3, 42.9, 48.1, 48.2, 49.5, 121.0, 124.9, 125.1, 145.3,
147.8, 150.3, 152.3, 188.3, 207.3.
(9) Gaillard, S.; Bosson, J.; Ramén, R. S.; Nun, P.; Slawin,
A. M. Z.; Nolan, S. P. Chem. Eur. J. 2010, 16, 13729.
(10) Ackermann, L.; Kaspar, L. T. J. Org. Chem. 2007, 72, 6149.
(11) (a) Kim, N.; Kim, Y.; Park, W.; Sung, D.; Gupta, A. K.; Oh,
C. H. Org. Lett. 2005, 7, 5289. (b) Oh, C. H.; Lee, J. H.;
Lee, S. M.; Yi, H. J.; Hong, C. S. Chem. Eur. J. 2009, 15, 71.
(c) Oh, C. H.; Lee, S. M.; Hong, C. S. Org. Lett. 2010, 7,
5289.
(12) Wang, W.; Xu, B.; Hammond, B. J. Org. Chem. 2009, 74,
1640.
(13) Oh, C. H.; Yi, H. J.; Lee, K. H. Bull. Korean Chem. Soc.
2010, 31, 683.
1
Compound 15b: H NMR (400 MHz, CDCl3): d = 1.23 (t, 6 H,
J = 7.2 Hz), 1.65–1.68 (m, 10 H), 1.98–2.02 (m, 2 H), 2.09–2.13 (m,
2 H), 3.31 (s, 2 H), 3.73–3.76 (m, 4 H), 4.13 (s, 2 H), 4.17 (q, 4 H,
J = 7.2 Hz), 4.94–5.03 (m, 2 H), 5.70–5.80 (m, 1 H), 7.51 (d, 1 H,
J = 14.0 Hz), 9.77 (s, 1 H). 13C NMR (100 MHz, CDCl3): d = 14.0,
24.8, 26.2, 29.1, 32.4, 45.3, 48.2, 55.2, 61.6, 115.2, 120.9, 125.3,
137.6, 145.3, 150.2, 151.4, 170.7, 188.2, 203.5.
Synlett 2012, 23, 897–902
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