Gold-catalyzed intramolecular hydroalkoxylation/cyclization of conjugated dienyl alcohols

Article abstract of DOI:10.1016/j.tet.2012.03.120

Catalytic intramolecular additions of hydroxyl groups to tethered conjugated dienes are described. The reactions proceed smoothly at 60 °C in the presence of 5 mol % of (PPh₃)AuCl/AgOTf as a catalyst. A broad range of structurally diverse conjugated dienes produce substituted tetrahydrofurans and tetrahydropyrans in good yields. This reaction represents an atom-economic route to construct five- and six-membered cyclic ethers.

Full text of DOI:10.1016/j.tet.2012.03.120

Tetrahedron 68 (2012) 4805e4812
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journal homepage: www.elsevier.com/locate/tet
Gold-catalyzed intramolecular hydroalkoxylation/cyclization of conjugated dienyl
alcohols
*
B. Chandrasekhar, Jae-Sang Ryu
Center for Cell Signaling & Drug Discovery Research, College of Pharmacy and Division of Life & Pharmaceutical Sciences, Ewha Womans University, 11-1 Daehyun-Dong,
Seodaemun-Gu, Seoul 120-750, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Catalytic intramolecular additions of hydroxyl groups to tethered conjugated dienes are described. The
reactions proceed smoothly at 60 ꢀC in the presence of 5 mol % of (PPh3)AuCl/AgOTf as a catalyst. A broad
range of structurally diverse conjugated dienes produce substituted tetrahydrofurans and tetrahy-
dropyrans in good yields. This reaction represents an atom-economic route to construct five- and six-
membered cyclic ethers.
Received 4 February 2012
Received in revised form 29 March 2012
Accepted 30 March 2012
Available online 9 April 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Dedicated to Professor Young-Ger Suh on
his 60th birthday
Keywords:
Hydroalkoxylation
Conjugated diene
Alcohol
Gold
Cyclization
1. Introduction
Ag,5 Cu,6 Pt,7 Pd,8 Al,9 and Ln3,10 catalysts. Nevertheless, the rela-
tively low reactivity of alkenes and the intrinsic chirality of 1,3-
Oxygen heterocycles1 are widespread structural motifs found in
a diverse array of bioactive natural products. Despite the biological
relevance of these motifs, the traditional synthetic methods for
oxygen heterocycles are limited. Therefore, the development of
new, efficient synthetic methodologies for CeO bond formation is
of fundamental interest to modern organic chemists. In this con-
text, direct addition of OeH bond to non-activated CeC multiple
bonds, so-called hydroalkoxylation,2 offers in principle a straight-
forward, atom-economical process for the CeO bond formation.
disubstituted allenes have prompted chemists to search for new
hydroalkoxylation/hydroamination substrates.11 From this per-
spective, conjugated dienes are attractive precursors for the intra-
molecular hydroalkoxylations. Compared to alkenes, alkynes and
allenes, only a few examples of intramolecular hydroalkoxylation of
conjugated dienes are known. Yeh and co-workers reported
both CeCl3$7H2OeNaI-catalyzed intramolecular hydroalkoxylation
of 7-hydroxy-1,3-dienes,12 and Pd-catalyzed intramolecular
hydroalkoxylation/cross-coupling of 7-hydroxy-1,3-dienes and aryl
However, the relatively high bond enthalpies of most OeH
s
-bonds
bromides,13 while Dunach and co-workers reported Al(OTf)3-cata-
~
and the modest reactivity of electron-rich olefins with nucleophiles
make it elusive.3 Recently, transition-metal-catalyzed intra-
molecular insertion of the OeH bond of an alcohol across the
tethered CeC multiple bonds has emerged as an attractive method
to overcome these inherent problems. Specifically, the various
transition-metal-catalyzed intramolecular hydroalkoxylations of
alkenes, alkynes, and allenes have been well documented for Au,4
lyzed intramolecular hydroalkoxylation of conjugated dienyl alco-
hols that was applied to the synthesis of rose oxide.14
Over the last decade, gold catalysts have been extensively
studied due to their superior catalytic activity in various
organic transformations.15 In particular, gold-catalyzed intra-
molecular hydroalkoxylation has attracted considerable attention
as an effective approach toward cyclic ethers. In our ongoing efforts
to develop catalytic intramolecular hydroalkoxylation of un-
saturated alcohols,16 we herein report for the first time the gold-
catalyzed intramolecular hydroalkoxylation of conjugated dienyl
alcohols [Eq. 1].
* Corresponding author. Tel.: þ82 2 3277 3008; fax: þ82 2 3277 2851; e-mail
address: ryuj@ewha.ac.kr (J.-S. Ryu).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.03.120

4806
B. Chandrasekhar, J.-S. Ryu / Tetrahedron 68 (2012) 4805e4812
in the presence of various combinations of gold catalysts and silver
R3
R2 R3
salts: [(IPr)AuCl] (IPr¼N,N0-bis(2,6-diisopropylphenyl)imidazol-2-
ylidene), (PPh3)AuCl, AuCl, AuCl3, along with AgOTf, AgOTs,
AgSbF6, AgBF4 or AgNO3 (Table 1). To our delight, AueAg catalyst
systems were effective in cycloisomerization and produced the
corresponding cyclic ethers except for [(IPr)AuCl]/AgBF4, (PPh3)
AuCl/AgBF4, and AuCl/AgNO3 (Table 1, entries 4, 9, and 15). In most
cases, the gold-catalyzed intramolecular hydroalkoxylation affor-
ded the 5-exo 1,4-addition product 2 as the sole product, which was
derived from addition of the oxygen and proton across the conju-
gated diene system through 5-exo-trig cyclization. However, upon
treatment with [(IPr)AuCl]/AgOTs, [(IPr)AuCl]/AgNO3, (PPh3)AuCl/
AgOTs or (PPh3)AuCl/AgNO3, the formation of 5-exo 1,2-addition
product 3 was also observed (entries 2, 5, 7, and 10).
Au catalyst
Additive
R2
R1
R1
n
n
(1)
OH
O
R1, R2, R3 = H, alkyl, aryl
n = 1, 2
2. Results and discussion
To assess the feasibility of gold-catalyzed intramolecular
hydroalkoxylation of conjugated dienes, we began to investigate
the cycloisomerization of 2,2-diphenyl-hepta-(4E,6)-dien-1-ol (1)
Table 1
Intramolecular hydroalkoxylation of conjugated dienyl alcohol 1a
Ph
Ph
Ph
catalyst (5 mol%)
Ph
Ph
Ph
additive (5 mol%)
toluene
OH
O
O
1
2
3
Ph
Ph
O
O
Ph
Ph
4
Entry
Catalyst
Additive
Temp (ꢀC)
Time (h)
Yieldb (%)
2 (E/Z)
3
4
1
2
3
4
5
6
7
8
[(IPr)AuCl]
[(IPr)AuCl]
[(IPr)AuCl]
[(IPr)AuCl]
[(IPr)AuCl]
(PPh3)AuCl
(PPh3)AuCl
(PPh3)AuCl
(PPh3)AuCl
(PPh3)AuCl
AuCl
AuCl
AuCl
AuCl
AuCl
AuCl3
AuCl3
AuCl3
AuCl3
AgOTf
AgOTs
AgSbF6
AgBF4
AgNO3
AgOTf
AgOTs
AgSbF6
AgBF4
AgNO3
AgOTf
AgOTs
AgSbF6
AgBF4
AgNO3
AgOTf
AgOTs
AgSbF6
AgBF4
AgNO3
d
60
60
60
60
60
60
60
60
60
60
rt
60
rt
60
60
rt
60
rt
rt
60
60
60
60
4
24
144
72
144
12
120
12
24
120
48
72
48
72
72
36
24
12
36
48
24
50 (11:1)
38 (6:1)
65 (3:1)
0
49 (1:1)
85 (10:1)
40 (1:1)
65 (10:1)
0
10 (1:1)
31 (E only)
53 (E only)
36 (E only)
28 (E only)
0
68 (E only)
80 (E only)
83 (E only)
10 (E only)
10 (E only)
25 (E only)
0
0
19
0
0
30
0
10
0
0
20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
8
8
0
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
AuCl3
AuCl3
(PPh3)AuCl
d
0
0
0
20
0
0
d
12
12
AgOTf
0
a
Reaction condition: 1 (0.2 mmol), Au-catalyst (5 mol %), Ag salt (5 mol %), toluene (1 mL).
Isolated yields.
b
[(IPr)AuCl]
=
N
N
Au
Cl

B. Chandrasekhar, J.-S. Ryu / Tetrahedron 68 (2012) 4805e4812
4807
Among the catalysts screened, the best result was obtained from
a combination of 5 mol % of (Ph3P)AuCl and 5 mol % of AgOTf in
toluene at 60 ꢀC, which produced only 2 in 85% yield (E/Z¼10:1,
entry 6). The obtained 5-exo 1,4-addition product 2 was an in-
separable E/Z mixture and the ratio was measured by NMR. In the
meantime, AuCl/Ag salts or AuCl3/Ag salts exclusively produced the
E isomer (entries 11‒14, 16‒21). In our attempts to develop an ef-
fective catalytic system, we screened Au(III) catalysts as well. In-
terestingly, when conjugated dienyl alcohol 1 was treated with the
combination of AuCl3 and Ag salts, the dimeric compound 4 was
delivered as a minor product in low yield (entries 16‒18, 20). The
yield of the dimerization product 4 could be increased up to 20%
when the reaction was carried out only in the presence of AuCl3
(entry 21). Au(I)/Au(III)-catalyzed alkyne dimerizations have
sometimes been reported but Au(I)/Au(III)-catalyzed alkene di-
merizations are rare.15b,d In contrast to Au/Ag catalyst systems,
neither (PPh3)AuCl nor AgOTf by themselves effectively promoted
the reaction (entries 22 and 23). These intramolecular hydro-
alkoxylation reactions failed to give the desired products at 60 ꢀC.
After establishing the optimal conditions, we examined the scope
of the gold-catalyzed intramolecular hydroalkoxylation (Table 2). We
applied the (PPh3)AuCl/AgOTf catalytic system to the intramolecular
cycloisomerization ofvarious conjugated dienyl alcoholsin tolueneat
60 ꢀC. All reactions using (PPh3)AuCl/AgOTf in Table 2 provided E
isomer and trace amount of byproducts. Because of the negligible
amount, the structures of byproducts including Z isomer could not be
isolated and identified. Under the optimized reaction conditions,
conjugated dienyl alcohol 5a underwent cycloisomerization
smoothly to furnish the 5-exo 1,4-addition cyclic ether 6a (entry 1),
and 5b and 5c afforded 6-exo 1,4-addition cyclic ethers (entries 2 and
3). Five- and six-membered ring formations were rapid and smooth;
however, seven-membered ring formation was not effective. Instead
of giving the corresponding seven-membered cyclic ether, (E)-2,2-
diphenylnona-6,8-dien-1-ol (5d) produced the tetrahydropyran 6d
in 66% yield after 12 h (entry 4). The reaction was carried out several
times and the product was clearly confirmed by 2D NMR. This was an
unexpected result. Although there was no literature precedent for
this kind of intramolecular hydroalkoxylation cyclization, gold(I)-
catalyzed alkene hydroamination to give seven-membered ring
was reported to be sluggish and the alkene isomerization was ob-
served as an alternative.17 In addition, similar alkene migration was
also reported for (PPh3)AuOTf-catalyzed intermolecular hydro-
alkoxylation.18 Thus, we envisioned the possible mechanism of this
unusual cyclization based on the alkene isomerization. Presumably,
gold-catalyzed isomerization of a terminal diene to an internal diene
is much faster than seven-membered ring cyclization. The sub-
sequently generated internal diene would be cyclized rapidly to
tetrahydropyran.
Table 2
Intramolecular hydroalkoxylation of conjugated dienyl alcohols catalyzed by (PPh3)AuCl/AgOTf in toluene at 60 ꢀCa
Entry
Substrate
Product
Time (h)
Yieldb (%)
1
12
60
OH
5a
O
6a
Ph
Ph
Ph
Ph
2
1
81
OH
O
6b
5b
3
12
62
OH
O
6c
5c
Ph
Ph
4
12
66
O
6d
Ph
Ph
Ph
Ph
Ph
Ph
5
2
60 (6e/6e0¼1:2)
n-Bu
O
n-Pr
O
OH
5e
6e
6e'
(continued on next page)

4808
B. Chandrasekhar, J.-S. Ryu / Tetrahedron 68 (2012) 4805e4812
Table 2 (continued )
Entry
Substrate
Product
Time (h)
Yieldb (%)
Ph
Ph
Ph
Ph
6
7
3
47
O
OH
5f
6f
Ph
Ph
Ph
4
70 (6g/6g0¼2:1)
O
6g (+)
O
6g' (+)
OH
5g
HO
HO
8
9
3.5
74c
OH
5h
O
6h
O
HO
9
63d
O
OH
6i
5i
Ph
Ph
Ph
Ph
Ph
Ph
10
2
69e (6j/6j0¼3:1)
O
OH
5j
O
6j (+)
6j' (+)
Ph
Ph
Ph
Ph
Ph
Ph
11
12
80 (6k/6k0¼1:3)
OH
O
6k (+)
O
6k' (+)
5k
a
Reaction conditions: conjugated dienyl alcohol (0.2 mmol), Au-catalyst (5 mol %), Ag salt (5 mol %), toluene (1 mL).
Isolated yields.
b
c
two isomers are not separable (dr¼2:1).
d
e
Three stereoisomers were isolated (dr¼2:1:1).
2,5-cis isomer and 2,5-trans isomer are not separable.
Meanwhile, the reactions were general for both terminal dienes
of note is that substituting C-2 with different groups gave rise to the
2,4,4-trisubstituted products 6g and 6g0, which were obtained in
70% yield and 2:1 dr, favoring the 2,4-cis diastereomer (entry 7).
The two isomers were separable by column chromatography and
unambiguously identified by 1D-NOE experiments (see
Supplementary data). Interestingly, the conjugated dienyl diol 5h
gave the monocyclized product in 74% yield (entry 8), whereas the
conjugated dienyl diol 5i containing two 1,3-dienes gave the
double cyclization product 6i with a mixture of isomers in 63% yield
(entry 9).
Many naturally occurring tetrahydrofurans and tetrahydropyr-
ans contain 2,5-disubstituents and 2,6-disubstituents, respectively.
Therefore, we were interested in the diastereoselectivity in the
cyclization of conjugated dienyl secondary alcohols. The cyclization
of substrates containing secondary eOH groups proceeded
and internal dienes. The internal-diene cycloisomerizations were
faster than the corresponding terminal-diene cyclization reactions
(Table 1, entry 6 vs Table 2, entries 5 and 6). Alkyl-substituted in-
ternal diene 5e afforded a 1:2 mixture of 5-exo 1,4-addition product
6e and 6-endo product 6e0 (entry 5). However, aryl-substituted
internal diene 5f allowed only 6-endo cyclic ether 6f in 3 h (entry
6). The 5-exo-trig cyclization was predominant for terminal dienes,
whereas 6-endo-trig cyclization was a major route for internal diene
cyclizations. The structures of 6e, 6e0, and 6f were unambiguously
confirmed by 2D NMR (HeH COSY), which can be found in
Supplementary data. The mechanistic reason for this regiose-
lectivity is quite puzzling and is still under investigation. However,
6-endo-trig cyclization for the internal diene hydroalkoxylation has
been already reported in the previous literatures.14 Another feature

B. Chandrasekhar, J.-S. Ryu / Tetrahedron 68 (2012) 4805e4812
4809
smoothly and provided 2,5-disubstituted tetrahydrofuran and 2,6-
disubstituted tetrahydropyran (entries 10 and 11). Interestingly, 5k
favored the formation of trans-2,6-disubstituted tetrahydropyran
6k0 with 3:1 diastereoselectivity, which was confirmed by 1D-NOE
(see Supplementary data). Notably, gold(I)-catalyzed diene hydro-
alkoxylation exhibits the opposite diastereoselectivity to allene
hydroalkoxylation favoring cis-2,6-disubstituted tetrahydropyr-
an.4e Likewise, 5j preferred the formation of cis-2,6-disubstituted
tetrahydrofuran 6j with 3:1 diastereoselectivity.
intermediate B does not occur under the optimum reaction con-
ditions. Instead, the intermediate B is converted to intermediate C
exclusively.
(PPh3)AuCl (5 mol%)
Ph
Ph
Ph
Ph
O
O
AgOTf (5 mol%), toluene
60 oC, 24 h
3
2
Mechanistically, we envisage a plausible pathway for hydro-
alkoxylation of conjugated dienyl alcohols based on the pre-
viously reported gold(I)-catalyzed hydroamination mechanism of
1,3-dienes (Scheme 1).19 (PPh3)AuOTf, produced from the reaction
of (PPh3)AuCl and AgOTf, binds to the conjugated diene. Co-
ordination of the gold(I) species to the conjugated diene of 1
gives a gold(I)ediene complex A.20 Then, intramolecular addition
3. Conclusion
In conclusion, (PPh3)AuOTf, generated in situ from the combi-
nation of (PPh3)AuCl and AgOTf, catalyzes intramolecular hydro-
alkoxylation of conjugated dienyl alcohols, which offers a facile
synthetic route for formation of five- and six-membered rings such
as tetrahydrofuran and tetrahydropyran. The cycloisomerizations
proceed with a variety of substrates, including terminal dienes,
internal dienes, primary alcohols, and secondary alcohols, through
exo-trig and endo-trig modes of cyclization. We believe that this
method will be a good entry for the synthesis of tetrahydrofuran
and tetrahydropyran-containing natural products. Thus, our on-
going research is focused on the application of this new method
toward the synthesis of complex cyclic ether natural products.
of eOH generates the
formed CeO bond. Allylic isomerization of B leads to C. Proto-
nolysis of the CeAu bond of C affords the
2-alkene gold in-
h
1-allylgold intermediate B with the newly
h
termediate D. Replacement of the double bond of D with triflate
produces the tetrahydrofuran 2 and regenerates the reactive
species (PPh3)AuOTf in the catalytic cycle.
In the proposed mechanism there was a concern that the
terminal olefin product 3 might be initially formed and iso-
merized to the internal olefin product 2 during the Au-catalyzed
intramolecular hydroalkoxylation. In order to clarify the isomer-
ization concern, we isolated the terminal olefin product 3 and
treated compound 3 with optimum reaction conditions (PPh3)
AuCl/AgOTf). However, no isomerization was observed at 60 ꢀC
after 24 h and 3 was recovered.21 It means that the terminal olefin
product 3 is not formed under the optimum reaction conditions
4. Experimental
4.1. General method
Reagents were purchased from commercial suppliers, and used
without further purification. Reactions were performed in flame-
and mechanistically protonolysis of the CeAu bond of h
1-allylgold
Ph3PAuCl + AgOTf
AgCl
Ph
Ph
Ph
Ph
O
Ph3PAuOTf
2
OH
1
+
Ph
+
Ph
Ph
Ph
-
TfO
-
TfO
Au
O
Au PPh3
OH
PPh3
A
D
PPh3
Au
+
+
Ph
Ph
Ph
Ph
Ph
Ph
Au
PPh3
-
TfO
-
TfO
O
H
O
O
H
3
Ph3PAuOTf
C
B
Scheme 1. Plausible reaction mechanism for intramolecular hydroalkoxylation of conjugated dienyl alcohol 1.

4810
B. Chandrasekhar, J.-S. Ryu / Tetrahedron 68 (2012) 4805e4812
dried glassware under positive Ar pressure with magnetic stirring.
TLC was performed on 0.25 mm E. Merck silica gel 60 F254 plates
and visualized under UV light (254 nm) or by staining with cerium
ammonium molybdate (CAM). Flash chromatography was per-
formed on E. Merck 230e400 mesh silica gel 60. NMR spectra were
recorded on Varian Unity 400 instruments at 24 ꢀC. Chemical shifts
are expressed in parts per million relative toTMS (1H, 0 ppm), CDCl3
(1H, 7.26 ppm; 13C, 77.2 ppm); coupling constants are expressed in
hertz. High-resolution mass spectra electrospray ionization
(HRMS-ESI) was obtained on an Agilent technologies 6220 TOF LC/
MS spectrometer. Infrared spectra were recorded on FTIR (FTS-135)
made by Bio-Rad.
4.2.5. (E)-5,5-Diphenyl-2-(prop-1-enyl)tetrahydro-2H-pyran
(6b). Colorless oil. TLC: Rf 0.70 (4:1 hexane/EtOAc). 1H NMR
(400 MHz, CDCl3): d 7.43e7.40 (m, 2H), 7.30e7.23 (m, 4H), 7.19e7.14
(m, 4H), 5.72 (dqd, J¼15.6, 6.4, 1.2 Hz, 1H), 5.48 (ddq, J¼15.2, 6.8,
1.6 Hz, 1H), 4.65 (dd, J¼12.0, 2.4 Hz, 1H), 3.88 (m, 1H), 3.59 (d,
J¼12.0 Hz, 1H), 2.51e2.40 (m, 2H), 1.68 (dd, J¼6.8, 1.6 Hz, 3H),
1.61e1.56 (m, 1H), 1.40e1.25 (m, 1H). 13C NMR (100 MHz, CDCl3):
d
146.9, 145.9, 132.2, 129.1, 128.4, 128.2, 127.8, 127.2, 126.5, 125.8,
78.6, 75.0, 45.9, 34.7, 28.4, 18.0. HRMS m/z calcd for C20H22ONa
[MþNa]þ 301.1563, found 301.1559. IR (KBr film): 2934, 1494, 1004,
699 cmꢁ1
.
4.2.6. (E)-3-(Prop-1-enyl)-2-oxaspiro[5.5]undecane (6c). Colorless
oil. TLC: Rf 0.73 (4:1 hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
4.2. Representative procedure for intramolecular
hydroalkoxylation of conjugated dienyl alcohols (Table 1,
entry 6)
d
5.69 (dqd, J¼15.2, 6.4, 1.2 Hz, 1H), 5.52 (ddq, J¼15.2, 6.4, 1.6 Hz,
1H), 3.78 (dd, J¼11.2, 2.8 Hz, 1H), 3.66 (m, 1H), 3.12 (d, J¼11.2 Hz,
1H), 1.75 (ddd, J¼13.2, 6.0, 3.2 Hz, 1H), 1.69 (ddd, J¼6.4, 1.6, 0.8 Hz,
3H), 1.61e1.54 (m, 2H), 1.52e1.40 (m, 8H), 1.22 (td, J¼13.2, 4.4 Hz,
A mixture of (PPh3)AuCl (5.0 mg, 0.01 mmol) and AgOTf (2.5 mg,
0.01 mmol) in anhydrous toluene (0.2 mL) was stirred at room
temperature for 10 min, treated with a solution of 1 (57 mg,
0.21 mmol) in toluene (0.8 mL), and the resulting suspension was
stirred at 60 ꢀC for 12 h. Progress of the reaction was monitored by
TLC. Upon the completion of the reaction, solvent was evaporated.
The residue was purified by column chromatography (49:1 hexane/
EtOAc) to afford 2 (48 mg, 85%) as a colorless oil.
1H), 1.14e1.18 (m, 2H). 13C NMR (100 MHz, CDCl3):
d 132.6, 127.2,
79.1, 76.7, 36.8, 34.3, 32.1, 31.4, 27.8, 27.0, 21.8, 21.7, 18.0. HRMS m/z
calcd for C13H26ON [MþNH4]þ 212.2009, found 212.2010. IR (KBr
film): 2925, 2848, 1451, 1077, 772 cmꢁ1
.
4.2.7. (E)-2-(But-1-enyl)-5,5-diphenyltetrahydro-2H-pyran
(6d). Viscous colorless oil. TLC: Rf 0.53 (19:1 hexane/EtOAc). 1H
NMR (400 MHz, CDCl3): d 7.44e7.41 (m, 2H), 7.3e7.14 (m, 8H), 5.75
(dtd, J¼15.2, 6.0, 0.8 Hz, 1H), 5.45 (ddt, J¼15.2, 7.2, 1.6 Hz, 1H), 4.66
(dd, J¼12.0, 2.4 Hz, 1H), 3.90 (m, 1H), 3.60 (d, J¼12.0 Hz, 1H),
2.53e2.41 (m, 2H), 2.03 (quin, J¼7.2 Hz, 2H), 1.59 (ddd, J¼13.6, 6.0,
3.6 Hz, 1H), 1.41e1.31 (m, 1H), 0.97 (t, J¼7.2 Hz, 3H). 13C NMR
4.2.1. (E)-4,4-Diphenyl-2-(prop-1-enyl)tetrahydrofuran (2).4e TLC:
Rf 0.56 (9:1 hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
d 7.30e7.25
(m, 6H), 7.23e7.18 (m, 4H), 5.68 (dq, J¼15.2, 6.4 Hz, 1H), 5.53 (ddd,
J¼15.2, 8.0,1.6 Hz,1H), 4.64 (dd, J¼8.8,1.2 Hz,1H), 4.38 (m,1H), 4.13
(d, J¼8.8 Hz, 1H), 2.61 (ddd, J¼12.4, 6.0, 1.2 Hz, 1H), 2.42 (dd, J¼12.4,
9.6 Hz, 1H), 1.68 (dd, J¼6.4, 1.6 Hz, 3H). 13C NMR (100 MHz, CDCl3):
(100 MHz, CDCl3):
d 146.9, 145.9, 134.6, 129.8, 129.1, 128.4, 128.2,
127.2, 126.5, 125.8, 78.8, 75.0, 45.9, 34.8, 28.6, 25.5, 13.4. HRMS m/z
calcd for C21H24ONa [MþNa]þ 315.1719, found 315.1723. IR (KBr
d
146.3, 146.0, 132.0, 128.7, 128.6, 128.5, 127.4 (2C),126.7, 126.5, 79.8,
film): 2959, 2845, 1494, 1078, 698 cmꢁ1
.
77.5, 56.4, 45.5, 17.9. HRMS m/z calcd for C19H20ONa [MþNa]þ
287.1406, found 287.1402. IR (KBr film): 1493, 1446, 1047, 699 cmꢁ1
.
4.2.8. (E)-2-(Hex-1-enyl)-4,4-diphenyltetrahydrofuran
(6e). Colorless oil. TLC: Rf 0.72 (9:1 hexane/EtOAc). 1H NMR
4.2.2. 2-Allyl-4,4-diphenyltetrahydrofuran (3). Colorless oil. TLC: Rf
0.60 (9:1 hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
7.31e7.18 (m,
(400 MHz, CDCl3):
d
7.33e7.17 (m,10H), 5.65 (dt, J¼15.2, 6.8 Hz,1H),
d
5.50 (dd, J¼15.2, 7.6 Hz, 1H), 4.65 (d, J¼8.8 Hz, 1H), 4.38 (m, 1H),
4.13 (d, J¼8.8 Hz, 1H), 2.60 (ddd, J¼12.4, 6.0, 0.8 Hz, 1H), 2.42 (dd,
J¼12.4, 9.6 Hz, 1H), 2.04e1.99 (m, 2H), 1.35e1.25 (m, 4H), 0.87 (t,
10H), 5.81 (m, 1H), 5.12e5.04 (m, 2H), 4.62 (d, J¼8.4 Hz, 1H), 4.13 (d,
J¼8.4 Hz, 1H), 4.09 (m, 1H), 2.59 (dd, J¼12.4, 6.0 Hz, 1H), 2.45e2.28
(m, 3H). 13C NMR (100 MHz, CDCl3):
d
146.5, 146.1, 134.9, 128.6,
J¼7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3):
d 146.3, 146.0, 134.0,
128.5, 127.4, 127.3, 126.6, 126.4, 117.4, 78.2, 77.1, 56.2, 44.5, 40.5, 17.9.
130.5, 128.6, 128.5, 127.3, 127.2, 126.6, 126.5, 79.8, 77.1, 56.4, 45.6,
HRMS m/z calcd for C19H20ONa [MþNa]þ 287.1406, found 287.1404.
32.0, 31.4, 22.4, 14.1. HRMS m/z calcd for C22H27O [MþH]þ 307.2056,
IR (KBr film): 2923, 1493, 1261, 1073, 699 cmꢁ1
.
found 307.2065. IR (KBr film): 2955, 1494, 1054, 699 cmꢁ1
.
4.2.3. (1E,5E)-1,6-Bis(4,4-diphenyltetrahydrofuran-2-yl)hexa-1,5-
4.2.9. (E)-2-(Pent-1-enyl)-5,5-diphenyltetrahydro-2H-pyran
diene (4). Light yellow oil. TLC: Rf 0.48 (9:1 hexane/EtOAc). 1H NMR
(6e0). Colorless oil. TLC: Rf 0.74 (9:1 hexane/EtOAc). 1H NMR
(400 MHz, CDCl3):
d
7.32e7.18 (m, 20H), 5.84 (AB quartet, J¼5.6 Hz,
(400 MHz, CDCl3): d 7.44e7.41 (m, 2H), 7.30e7.24 (m, 4H), 7.18e7.15
2H), 5.83 (AB quartet, J¼5.6 Hz, 2H), 4.69 (dd, J¼8.8, 1.2 Hz, 2H),
4.48e4.43 (m, 2H), 4.15 (d, J¼8.8 Hz, 2H), 4.04e4.02 (m, 4H), 2.67
(ddd, J¼12.0, 6.0, 1.2 Hz, 2H), 2.45 (dd, J¼12.0, 9.6 Hz, 2H). 13C NMR
(m, 4H), 5.69 (dtd, J¼15.2, 6.8, 0.8 Hz, 1H), 5.46 (ddt, J¼15.2, 6.8,
1.2 Hz, 1H), 4.65 (dd, J¼12.0, 2.4 Hz, 1H), 3.89 (m, 1H), 3.59 (d,
J¼12.0 Hz, 1H), 2.49e2.43 (m, 2H), 2.01e1.95 (m, 2H), 1.60e1.56 (m,
1H), 1.41e1.33 (m, 3H), 0.88 (t, J¼7.2 Hz, 3H). 13C NMR (100 MHz,
(100 MHz, CDCl3):
d 145.9, 145.5, 135.3, 128.7, 128.6, 127.5, 127.3,
127.2, 126.8, 126.6, 78.4, 56.4, 45.3, 44.4, 29.9. IR (KBr film): 2924,
1490, 1260, 699 cmꢁ1. HRMS m/z calcd for C38H38O2Na [MþNa]þ
549.2764, found 549.2805.
CDCl3): d 146.9, 146.0, 132.8, 131.0, 129.1, 128.5, 128.2, 127.2, 126.5,
125.8, 78.8, 75.0, 45.9, 34.8, 34.6, 28.6, 22.4, 13.9. HRMS m/z calcd
for C22H27O [MþH]þ 307.2056, found 307.2053. IR (KBr film): 2956,
1494, 1105, 698 cmꢁ1
.
4.2.4. (E)-3-(Prop-1-enyl)-2-oxaspiro[4.5]decane (6a). Colorless oil.
TLC: Rf 0.73 (4:1 hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
d
5.67
4.2.10. (E)-5,5-Diphenyl-2-(2-phenylethenyl)-tetrahydro-2H-pyran
(dq, J¼15.2, 6.8 Hz, 1H), 5.49 (ddq, J¼15.2, 7.2, 1.6 Hz, 1H), 4.30 (q,
J¼7.2 Hz, 1H), 3.62 (d, J¼8.4 Hz, 1H), 3.53 (d, J¼8.4 Hz, 1H), 1.88 (dd,
J¼12.4, 6.8 Hz, 1H), 1.69 (dd, J¼6.8, 1.6 Hz, 3H), 1.50e1.36 (m, 11H).
(6f). White solid. Mp: 118e120 ꢀC. TLC: Rf 0.77 (4:1 hexane/EtOAc).
1H NMR (400 MHz, CDCl3):
d 7.46e7.43 (m, 2H), 7.37e7.16 (m, 13H),
6.62 (d, J¼16.0 Hz, 1H), 6.22 (dd, J¼16.0, 6.0 Hz, 1H), 4.73 (dd,
J¼12.0, 2.4 Hz, 1H), 4.14e4.09 (m, 1H), 3.68 (d, J¼12.0 Hz, 1H),
2.55e2.47 (m, 2H),1.72 (qd, J¼6.0, 3.6 Hz,1H),1.51e1.41 (m, 1H). 13C
13C NMR (100 MHz, CDCl3):
d 132.6, 127.7, 79.7, 78.6, 45.2, 44.3, 37.1,
35.7, 26.2, 24.2, 23.8, 17.8. HRMS m/z calcd for C12H24ON [MþNH4]þ
198.1852, found 198.1852. IR (KBr film): 2924, 2853, 1449, 1050,
NMR (100 MHz, CDCl3):
d 146.8, 145.9, 137.0, 130.8, 130.4, 129.1,
962 cmꢁ1
.
128.7, 128.5, 128.3, 127.8, 127.2, 126.7, 126.6, 125.9, 78.5, 75.0, 46.0,

B. Chandrasekhar, J.-S. Ryu / Tetrahedron 68 (2012) 4805e4812
4811
34.8, 28.6. HRMS m/z calcd for C25H24ONa [MþNa]þ 363,1719, found
6j/6j0), 5.72e5.44 (m, 2H, 6j/6j0), 4.90 (q, J¼6.4 Hz, 1H, 6j),
4.79e4.72 (m, 2H, 6j0), 4.22 (m, 1H, 6j), 3.09 (dd, J¼13.6, 8.0 Hz, 1H,
6j0), 2.67 (dd, J¼12.0, 10.4 Hz, 1H, 6j), 2.34e2.28 (m, 1H, 6j/6j0), 1.71
(dd, J¼6.0, 0.8 Hz, 3H, 6j), 1.65 (dd, J¼6.4, 1.2 Hz, 3H, 6j0), 1.06 (d,
J¼6.0 Hz, 3H, 6j0), 0.90 (d, J¼6.4 Hz, 3H, 6j). 13C NMR (100 MHz,
363.1722. IR (KBr film): 2940, 1493, 1446, 1089, 764 cmꢁ1
.
4.2.11. (E)-4-Methyl-4-phenyl-2-(prop-1-enyl)tetrahydrofuran (6g,
6g0). Compound 6g: Colorless oil. TLC: Rf 0.42 (19:1 hexane/EtOAc).
1H NMR (400 MHz, CDCl3):
d
7.34e7.30 (m, 2H), 7.25e7.19 (m, 3H),
CDCl3): d
148.1 (6j), 147.4 (6j0), 145.5 (6j), 145.0 (6j0), 133.2 (6j0),
5.73 (dqd, J¼14.8, 6.4, 0.8 Hz, 1H), 5.51 (ddq, J¼14.8, 8.0, 1.6 Hz, 1H),
4.59 (m, 1H), 4.0 (d, J¼8.0 Hz, 1H), 3.95 (dd, J¼8.0, 0.8 Hz, 1H), 2.23
(ddd, J¼12.0, 6.0, 0.8 Hz, 1H), 2.00 (dd, J¼12.0, 9.6 Hz, 1H), 1.70 (dd,
132.6 (6j), 129.1 (6j0), 128.7 (6j), 128.6 (6j0), 128.4 (6j0), 128.3 (6j),
128.2 (6j), 128.1 (6j0), 128.0 (6j), 127.9 (6j), 127.5 (6j0), 126.5 (6j),
126.4 (6j0), 126.3 (6j/6j0), 80.5 (6j), 79.3 (6j0), 78.4 (6j), 77.6 (6j0),
59.3 (6j), 58.9 (6j0), 47.8 (6j0), 43.9 (6j), 21.0 (6j), 20.8 (6j0), 17.9 (6j),
17.5 (6j0). IR (KBr film): 2970, 1494, 1075, 699 cmꢁ1. HRMS m/z calcd
for C20H22ONa [MþNa]þ 301.1563, found 301.1555.
J¼6.4, 1.6 Hz, 3H), 1.44 (s, 3H). 13C NMR (100 MHz, CDCl3):
d 147.7,
132.3, 128.6, 128.1, 126.3, 126.1, 80.1, 78.9, 48.1, 46.2, 28.2, 17.9.
HRMS m/z calcd for C14H19O [MþH]þ 203.1430, found 203.1431. IR
(KBr film): 2963, 1496, 1048 cmꢁ1. Compound 6g0: Colorless oil. TLC:
Rf 0.45 (19:1 hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
d
7.35e7.29
4.2.15. (E)-2-Methyl-3,3-diphenyl-6-(prop-1-enyl)tetrahydro-2H-
(m, 4H), 7.23e7.19 (m, 1H), 5.72e5.65 (m, 1H), 5.62e5.56 (m, 1H),
4.37 (q, J¼7.6 Hz, 1H), 4.04 (d, J¼8.4 Hz, 1H), 3.91 (d, J¼8.4 Hz, 1H),
2.43 (dd, J¼12.4, 7.6 Hz, 1H), 1.83 (dd, J¼12.4, 7.6 Hz, 1H), 1.70 (dd,
pyran (6k, 6k0). 2,6-cis-Isomer 6k: Colorless oil. TLC: Rf 0.46 (19:1
hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
d 7.58e7.56 (m, 2H),
7.29e7.17 (m, 8H), 5.74 (dqd, J¼15.6, 6.4, 0.8 Hz, 1H), 5.58 (ddq,
J¼15.6, 7.2, 1.6 Hz, 1H), 4.03 (m, 1H), 3.74 (q, J¼6.8 Hz, 1H), 2.64 (td,
J¼13.2, 3.6 Hz, 1H), 2.10 (dt, J¼13.2, 3.6 Hz, 1H), 1.70 (ddd, J¼6.4, 1.6,
0.8 Hz, 3H), 1.50 (dq, J¼13.2, 2.8 Hz, 1H), 1.38e1.34 (m, 1H), 1.27 (d,
J¼6.4, 0.8 Hz, 3H), 1.45 (s, 3H). 13C NMR (100 MHz, CDCl3):
d 147.5,
132.6, 128.6, 128.2, 126.3, 126.2, 80.4, 79.0, 48.0, 46.9, 28.6, 17.9.
HRMS m/z calcd for C14H18ONa [MþNa]þ 225.1250, found 225.1255.
IR (KBr film): 2962, 1496, 1047, 771 cmꢁ1
.
J¼6.8 Hz, 3H). 13C NMR (100 MHz, CDCl3):
d 146.9, 144.7, 132.6,
131.6, 129.4, 127.8, 127.5, 127.4, 126.4, 125.6, 82.3, 79.9, 51.2, 38.5,
28.6, 18.1, 18.0. HRMS m/z calcd for C21H25O [MþH]þ 293.1900,
found 293.1901. IR (KBr film): 2923, 1652, 1115, 701 cmꢁ1. 2,6-trans-
Isomer 6k0: White solid. Mp: 97e99 ꢀC. TLC: Rf 0.43 (19:1 hexane/
4.2.12. (E)-(6-(Prop-1-enyl)tetrahydro-2H-pyran-3-yl)methanol
(6h). Colorless oil. TLC: Rf 0.33 (1:1 hexane/EtOAc). 1H NMR
(400 MHz, CDCl3): d 5.76e5.67 (m, 1H, major/minor), 5.53e5.47 (m,
1H, major/minor), 4.12 (qd, J¼4.4, 2.0 Hz, 1H, major), 3.99 (dt, J¼2.0,
11.6 Hz, 1H, minor), 3.86 (dd, J¼8.0, 10.4 Hz, 1H, minor), 3.80e3.75
(m, 1H, minor), 3.74e3.67 (m, 2H, minor), 3.64 (dd, J¼2.8, 11.6 Hz,
1H, major), 3.51 (dd, J¼10.8, 5.6 Hz, 1H, major), 3.45 (dd, J¼10.8,
6.8 Hz, 1H, major), 3.22 (t, J¼11.2 Hz, 1H, major), 1.90e1.73 (m, 2H,
major/minor), 1.70e1.68 (m, 3H, major/minor), 1.55e1.48 (m, 1H,
major/minor), 1.45e1.38 (m, 1H, major/minor), 1.29e1.19 (m, 1H,
EtOAc). 1H NMR (400 MHz, CDCl3):
d 7.45e7.43 (m, 2H), 7.28e7.21
(m, 5H), 7.15e7.09 (m, 3H), 5.69 (dqd, J¼15.2, 6.4, 0.8 Hz, 1H), 5.44
(ddq, J¼15.2, 6.4, 1.6 Hz, 1H), 4.91 (q, J¼6.4 Hz, 1H), 4.13 (m, 1H),
2.66 (td, J¼13.2, 3.6 Hz, 1H), 2.20 (m, 1H), 1.66 (dd, J¼6.4, 1.6 Hz,
3H), 1.48 (dq, J¼13.2, 3.2 Hz, 1H), 1.23e1.19 (m, 1H), 0.99 (d,
J¼6.4 Hz, 3H). 13C NMR (100 MHz, CDCl3):
d 148.1, 147.9, 132.8,
129.3, 128.4, 127.9, 127.5, 127.4, 126.0, 125.5, 74.5, 70.1, 48.3, 29.2,
major/minor). 13C NMR (100 MHz, CDCl3):
d
132.2 (major), 132.1
28.4, 17.9, 15.4. HRMS m/z calcd for C21H24NaO [MþH]þ 293.1900,
(minor), 127.4 (minor), 127.3 (major), 78.5 (major/minor), 71.0 (ma-
jor), 68.4 (minor), 65.1 (major), 63.4 (minor), 38.7 (major), 36.0
(minor), 31.6 (major/minor), 27.9 (minor), 26.7 (major), 24.4 (minor),
18.0 (major). HRMS m/z calcd for C9H17O2 [MþH]þ 157.1223, found
found 293.1892. IR (KBr film): 2937, 1494, 1111, 750 cmꢁ1
.
Acknowledgements
157.1227. IR (KBr film): 3386, 2931, 2853, 1449, 1085 cmꢁ1
.
This work was supported by the grant from the National Core
Research Center Program (No. 2012-0000952) of the Ministry of
Science & Technology and by the Ewha Global Top5 Grant 2011 of
Ewha Womans University.
4.2.13. 3,9-Di((E)-prop-1-enyl)-2,8-dioxaspiro[5.5]undecane
(6i). Isomer A: Colorless oil. TLC: Rf 0.57 (15:1 hexane/EtOAc). 1H
NMR (400 MHz, CDCl3):
d 5.73e5.64 (m, 2H), 5.53e5.46 (m, 2H),
4.29 (d, J¼10.4 Hz, 2H), 3.66 (m, 2H), 3.09 (d, J¼10.4 Hz, 2H), 1.68
Supplementary data
(dd, J¼6.4, 1.0 Hz, 3H), 1.46e1.25 (m, 8H). 13C NMR (100 MHz,
CDCl3):
d 132.3, 126.9, 78.7, 71.8, 34.2, 31.5, 28.3, 18.0. HRMS m/z
13
1H and C NMR spectra of 2e4, 6aek0, 1D-NOE spectra of 6g,
calcd for C15H25O2 [MþH]þ 237.1849, found 237.1848. IR (KBr film):
6g0, 6k, and 6k0, and experimental procedure for the synthesis of
substrates 5aek are provided. Supplementary data associated with
this article can be found in the online version, at doi:10.1016/
j.tet.2012.03.120. These data include MOL files and InChiKeys of the
most important compounds described in this article.
2924, 1716, 1652, 1455, 1073 cmꢁ1. Isomer B: Colorless oil. TLC: Rf
0.55 (15:1 hexane/EtOAc). 1H NMR (400 MHz, CDCl3):
d 5.74e5.65
(m, 2H), 5.55e5.46 (m, 2H), 4.23 (dd, J¼12.0, 2.4 Hz, 1H), 3.70e3.63
(m, 2H), 3.49 (dd, J¼11.0, 2.4 Hz, 1H), 3.22 (d, J¼11.6 Hz, 1H), 3.20
(dd, J¼12.0, 1.6 Hz, 1H), 2.35 (ddd, J¼13.2, 6.8, 2.8 Hz, 1H), 1.69 (m,
6H), 1.62e1.10 (m, 7H). 13C NMR (100 MHz, CDCl3):
d 132.24, 132.23,
References and notes
127.6, 127.5, 79.3, 79.0, 76.2, 72.3, 33.1, 31.8, 28.6, 27.8, 27.2, 18.0.
HRMS m/z calcd for C15H24O2Na [MþNa]þ 259.1669, found
259.1665. IR (KBr film): 2933, 1723, 1447, 1075, 966 cmꢁ1. Isomer C:
Colorless oil. TLC: Rf 0.53 (15:1 hexane/EtOAc). 1H NMR (400 MHz,
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(400 MHz, CDCl3):
d
7.31e7.17 (m, 8H, 6j/6j0), 7.09e7.05 (m, 2H,

4812
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