Platinum-catalyzed cyclization of o-alkynyl(oxo)benzenes with alkenes by 1,2-migration of benzene: Synthesis of 8-oxabicyclo[3.2.1]octane derivatives

Article abstract of DOI:10.1002/ejoc.200800888

An interesting migration of the rigid structure of benzene was observed when propargylic esters were introduced to the cyclization chemistry of o-alkynyl(oxo)benzene. Various 8-oxabicyclo[3.2.1]octane derivatives with many functional groups could be synthesized from this efficient approach catalyzed by platinum. The high stereo- and regioselectivity involved in this transformation was also attractive. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.

Full text of DOI:10.1002/ejoc.200800888

FULL PAPER
DOI: 10.1002/ejoc.200800888
Platinum-Catalyzed Cyclization of o-Alkynyl(oxo)benzenes with Alkenes by
1,2-Migration of Benzene: Synthesis of 8-Oxabicyclo[3.2.1]octane Derivatives
Xing-Zhong Shu,[a] Shu-Chun Zhao,[a] Ke-Gong Ji,[a] Zhao-Jing Zheng,[a] Xue-Yuan Liu,[a]
and Yong-Min Liang*[a]
Keywords: Platinum / 1,2-Migration / Homogeneous catalysis / Alkenes
An interesting migration of the rigid structure of benzene
was observed when propargylic esters were introduced to
the cyclization chemistry of o-alkynyl(oxo)benzene. Various
8-oxabicyclo[3.2.1]octane derivatives with many functional
groups could be synthesized from this efficient approach cat-
alyzed by platinum. The high stereo- and regioselectivity in-
volved in this transformation was also attractive.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
a popular research topic.[1–7] The formation of metal-con-
taining benzopyrylium-type intermediates is considered a
common process, which upon further treatment with vari-
ous reaction partners, such as, nucleophiles,[2] alkynes,[3] al-
kenes,[4] vinyl ethers,[5] carbonyl compounds,[6] and ketene
acetals,[7] result in diverse products (Scheme 1). However, to
our surprise there was no skeletal rearrangement observed,
although oxonium ions and metal carbenes are presumed
to exist in almost all reactions.[8] We envisioned that inter-
mediate VII, formed from the Diels–Alder reaction of
benzopyrylium with olefin, might undergo 1,2-aryl or alkyl
migration driven by both the oxonium ion and the negative
metal (Scheme 2). Herein, we report a platinum[9]-catalyzed
cyclization of o-alkynyl(oxo)benzenes with conventional al-
kenes to afford synthetically useful 8-oxabicyclo[3.2.1]oc-
tane derivatives in good yield, where the 1,2-migration of
the rigid benzene groups was the key step.[10]
Introduction
As a result of its synthetic potential, the transition-metal-
catalyzed cyclization of o-alkynyl(oxo)benzenes is currently
Scheme 2.
Results and Discussion
Scheme 1.
We started by using o-(phenylethynyl)benzaldehyde (1a)
with styrene (3 equiv.) in the presence of PtCl2 (5 mol-%)
under CO (1 atm) in toluene at 80 °C, and desired product
2a was obtained in 25% yield after 2.5 h (Table 1, entry 1).
To improve this result, we examined different types of al-
kynes, among which the exciting result was just obtained
when propargylic ester[11] was used (Table 1, entries 2–4). A
[a] State Key Laboratory of Applied Organic Chemistry, Lanzhou
University
Lanzhou 730000, P. R. China
Fax: +86-931-8912582
E-mail: liangym@lzu.edu.cn
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2009, 117–122
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
117

X.-Z. Shu, S.-C. Zhao, K.-G. Ji, Z.-J. Zheng, X.-Y. Liu, Y.-M. Liang
FULL PAPER
similar result was also observed with a lower temperature, Table 2. Scope study of the cyclization of o-alkynyl(oxo)benzenes.[a]
whereas the changes in solvent and catalyst systems could
not improve the yield (Table 1, entries 5–7). In contrast,
gold catalysis gave either a low yield or no desired product
(Table 1, entries 8–11). Thus, the use of PtCl2 (5 mol-%) and
CO (1 atm) in toluene (3 mL) at 60 °C was found to be the
most efficient system, and it was used as the standard con-
ditions.
Entry Substrate
Time
[h]
Product
(% Yield)[b]
1
2
3
4
5
X = R = R1 = R2 = H (1d)
1.5
4
4
2d (83)
2e (82)
2f (76)
2g (86)
Table 1. Optimization of the reaction conditions.[a]
X = R = R1 = H, R2 = Ph (1e)
X = R = R1 = H, R2 = 4-ClC6H4 (1f)
X = R = R1 = H, R2 = 4-CH3C6H4 (1g)
X = R = R1 = H,
1
R2 = 2,3-methylenedioxy (1h)
3
3
1
6
1.5
8
2h (73)
2i (48)
1j (72)
2k (73)
2l (25)
2m (41)
2n (89)
2o (98)
6
7
8
9
10
11
12
X = R = R1 = H, R2 = 2-furanyl (1i)
X = R = R1 = H, R2 = CH3 (1j)
X = R = R1 = H, R2 = C6H5CH2 (1k)
X = R = H, R1 = R2 = CH3 (1l)
X = H, R = CH3, R1 = R2 = H (1m)
X = 4-Cl, R = R1 = R2 = H (1n)
X = 3-CH3[c], R1 = R2 = H (1o)
Entry
R
Conditions
Product
(% Yield)[b]
1
2
Ph (1a)
C5H11 (1b)
PtCl2, CO, toluene, 80 °C, 2.5 h
PtCl2, CO, toluene, 80 °C, 3 h
2a (25)
2b (61)
2c (23)
2d (80)
2d (83)
2d (76)
2d (65)
2d (7)
4
2
3
4
5
6
CH2OH (1c) PtCl2, CO, toluene, 80 °C, 1 h
CH2OAc (1d) PtCl2, CO, toluene, 80 °C, 1 h
CH2OAc (1d) PtCl2, CO, toluene, 60 °C, 1.5 h
CH2OAc (1d) PtCl2, CO, DCE, 60 °C, 1 h
CH2OAc (1d) PtCl2, toluene, 60 °C, 10 h
[a] Unless noted, all reactions were carried out by using 1
(0.5 mmol) with styrene (3 equiv.) under PtCl2/CO (5 mol-%/1 atm)
in toluene (3 mL) at 60 °C. [b] Isolated yield. [c] The methyl substit-
uent is ortho to the alkyne.
7
8
9
10
11
CH2OAc (1d) AuCl3, DCM, room temp., 3 h
CH2OAc (1d) AuCl, DCM, room temp., 4 h
CH2OAc (1d) Au(PPh3)BF4, DCM, room temp., 4 h
CH2OAc (1d) Au(PPh3)OTf, DCM, room temp., 4 h
2d (11)
[c]
–
–
Table 3. Scope of the platinum-catalyzed cyclization of 1d with dif-
[c]
ferent alkenes.[a]
[a] Unless noted, all reactions were carried out by using 1
(0.5 mmol) with styrene (3 equiv.) under catalyst (5 mol-%) in sol-
vent (3 mL). [b] Isolated yield. [c] The substrate disappeared after
4 h; however, no desired product was observed.
Under the optimal conditions, we studied the scope of
this cyclization, as shown in Table 2. Various substituents
at the propargylic position were tolerated (Table 2, en-
tries 1–9), where aryl groups, such as phenyl and electron-
withdrawing and electron-rich aromatics, all led to good
yields of the desired products (Table 2, entries 2–5). The 2-
furyl substituent gave a moderate yield of 2i (Table 2, en-
try 6). The reaction efficiency was consistent with the steric
hindrance. The less-hindered methyl group gave a better re-
sult than a benzyl group on the propargyl acetate or di-
methyl substituents (Table 2, entry 7 vs. entries 8 and 9).
When the substrate with a ketone function was used, the
reaction also proceeded smoothly to afford 2m in slightly
lower yield (Table 2, entry 10). Furthermore, substituents
on the benzene ring did not affect the reaction, and always
good-to-excellent results were always achieved (Table 2, en-
tries 11 and 12).
We tested this cyclization with different alkenes (Table 3).
Among these, styrene gave the best result, especially the
electron-rich one (Table 3, entries 1 and 2). Hexene was also
applied in this transformation and a moderate yield was
obtained (Table 3, entry 3). However, alkenes with func-
tional groups always led to a poor yield of the desired prod-
uct or decomposition of the substrate (Table 3, entries 4 and
5). Internal alkenes, such as cyclohexene and trans-stilbene,
reacted smoothly to give corresponding trans and cis prod-
ucts in moderate yield (Table 3, entry 6 vs. 7).
Entry
R1
R2
R3
Time
[h]
Product
(% Yield)[b]
1
2
3
4-ClC6H4
4-CH3C6H4
C4H9
CH2OTBS
OEt
H
H
H
H
H
H
H
H
H
H
H
Ph
4
1
3
4
1
6
5
3a (53)
3b (82)
3c (51)
3d (21)
4
5[c]
6
–
[d]
–(CH2)4–
Ph
3e (37)
3f (46)
7
H
[a] Unless noted, all reactions were carried out by using 1d
(0.5 mmol) with the alkenes (3 equiv.) under PtCl2/CO (5 mol-%/
1 atm) in toluene (3 mL) at 60 °C. [b] Isolated yield. [c] Run at
room temp. [d] Decomposed.
Interestingly, when o-alkynyl(oxo)benzene (1e; Scheme 3)
was exposed to the conditions containing PtCl2 (5 mol-%)
and 1,5-cycloctadiene (3 equiv.) in toluene at 80 °C, polycy-
clic product 3g was obtained in 81% yield after 4 h. In this
reaction, one of the double bonds in the 1,5-cycloctadiene
Scheme 3. Cyclization of 1e with 1,5-cycloctadiene.
118
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Eur. J. Org. Chem. 2009, 117–122

Synthesis of 8-Oxabicyclo[3.2.1]octane Derivatives
CDCl3 by using TMS as an internal standard. IR spectra were
recorded with an FTIR spectrometer and only major peaks are
reported. Melting points were determined with a microscopic appa-
ratus and are uncorrected. All new compounds were further char-
acterized by element analysis. X-ray crystallography of 2e-1 is also
provided. Diastereomeric ratio was determined by H NMR spec-
troscopy. Commercially available reagents and solvents were used
without further purification.
was saved, what could be used for constructing more com-
plex structures.
A plausible mechanism for this transformation is shown
in Scheme 4. As previously reported, benzopyrylium-type
intermediate A is formed after coordination of the alkynes
to the platinum catalyst.[1–7] Subsequently, a high stereo-
and regiospecific Diels–Alder reaction of A with alkenes
leads to the formation of complex C, where the oxonium
ion might trigger the 1,2-migration of an adjacent group
when assisted with a metal to give compound D.[8] Further,
a 1,2-hydrogen-atom shift of nonstabilized carbene interme-
diate D afforded the desired products 2 and 3.[12] The excel-
1
General Produce for the Platinum-Catalyzed Cyclization of o-Alk-
ynyl(oxo)benzenes with Alkenes: To a stirred solution of o-alk-
ynyl(oxo)benzene 1 (0.50 mmol) in toluene (3.0 mL) was added
PtCl2 (6.7 mg, 5 mol-%) under a CO atmosphere (1 atm) at 60 °C.
When the reaction was considered complete as determined by TLC
lent stereoselectivity might be due to the steric hindrance of analysis, the reaction mixture was diluted with ethyl acetate
the R group, which orients R2 away from it in steps A to B.
In contrast, the regioselectivity of this reaction might be
(30 mL), and the solvent was evaporated under reduced pressure.
The residue was purified by chromatography on silica gel to afford
the corresponding products.
accounted for by considering carbocation intermediate E
2a: Yield: 38.7 mg (25%). Solid. M.p. 141–142 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.74–7.72 (m, 2 H), 7.49–7.14 (m, 11 H),
7.00–6.94 (m, 1 H), 6.93 (s, 1 H), 5.74–5.72 (d, J = 6.0 Hz, 1 H),
on the way from B to C.[4] When R2 is an aryl group or an
electron-donating substituent, carbocation E could be well
stabilized. The two factors directly lead to the formation of
favored intermediate C, which further transforms into de-
sired products 2 and 3.
3.32–3.26 (m, 1 H), 2.43–2.39 (dd, J = 17.3, 0.8 Hz, 1 H) ppm. 13
C
NMR (100 MHz, CDCl3): δ = 150.5, 142.5, 139.8, 139.4, 132.6,
130.1, 128.6, 128.3, 128.1, 127.6, 126.9, 126.8, 126.6, 124.9, 121.0,
118.6, 84.3, 77.3, 31.4 ppm. IR (KBr): ν = 3380, 3058, 3028, 2952,
˜
2923, 2855, 2246, 1952, 1809 cm–1. C23H18O (310.39): calcd. C
89.00, H 5.85; found C 88.86, H 5.92.
2b: Yield: 92.7 mg (61%). Solid. M.p. 88–89 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.29–7.14 (m, 8 H), 7.04–7.03 (m, 1 H),
6.39 (s, 1 H), 5.54–5.53 (d, J = 6 Hz, 1 H), 3.21–3.15 (m, 1 H),
2.29–2.24 (d, J = 17.2 Hz, 1 H), 2.16–2.12 (m, 1 H), 2.07–2.03 (m,
1 H), 1.57–1.54 (m, 2 H), 1.42–1.35 (m, 4 H), 0.92–0.89 (t, J =
14 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 149.9, 143.0,
139.8, 131.9, 131.0, 128.2, 127.4, 126.8, 126.5, 124.7, 120.9, 117.3,
83.3, 76.9, 34.2, 32.4, 31.3, 23.3, 22.6, 14.0 ppm. IR (KBr): ν =
˜
3051, 3025, 2952, 2931, 2863, 2729, 1944, 1896, 1795, 1708 cm–1.
C22H24O (304.43): calcd. C 86.80, H 7.95; found C 86.69, H 8.02.
2c: Yield: 30.4 mg (23%). Solid. M.p. 121–122 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.34–7.11 (m, 9 H), 6.43–6.42 (m, 1 H),
5.60–5.59 (d, J = 6.0 Hz, 1 H), 4.22–4.19 (m, 2 H), 3.27–3.21 (m,
1 H), 2.37–2.32 (m, 1 H); 2.06 (s, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 147.1, 143.2, 139.3, 133.4, 128.3, 127.7, 127.1, 127.1,
Scheme 4. Proposed mechanism with stereo- and regiospecific
study.
127.0, 124.8, 121.1, 117.7, 84.1, 77.2, 63.6, 31.5 ppm. IR (KBr): ν
˜
= 3430, 3051, 3027, 2923, 2857, 2246, 1951, 1791, 1692 cm–1.
C18H16O2 (264.32): calcd. C 81.79, H 6.10; found C 81.90, H 6.07.
2d: Yield: 127.0 mg (83%). Solid. M.p. 120–121 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.33–7.08 (m, 9 H), 6.45 (s, 1 H), 5.62–
5.60 (d, J = 6.0 Hz, 1 H), 4.82–4.79 (d, J = 12.4 Hz, 1 H), 4.63–
4.60 (d, J = 12.0 Hz, 1 H), 3.28–3.22 (m, 1 H), 2.32–2.28 (m, 1 H),
2.10 (s, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 171.0, 147.1,
Conclusions
We reported an efficient approach to 8-oxabicyclo[3.2.1]-
octane derivatives by platinum-catalyzed cyclization of o-
alkynyl(oxo)benzenes with alkenes. In this transformation, 142.7, 139.2, 133.3, 128.2, 127.7, 127.1, 127.0, 126.6, 124.7, 121.1,
117.4, 82.1, 77.3, 64.5, 31.2, 20.8 ppm. IR (KBr): ν = 3465, 3051,
˜
a 1,2-migration of the rigid structure of benzene was ob-
served. The high stereo- and regioselectivity was also dis-
closed. In comparison with conventional alkynes, propar-
gylic esters gave the best result. The detailed mechanism of
the influence of the ester group is worthy of further study.
3026, 2950, 2899, 2251, 1953, 1741 cm–1. C20H18O3 (306.36): calcd.
C 78.41, H 5.92; found C 78.46, H 5.77.
1
(R,S/S,R)-2e-1: Yield: 82.1 mg (43%). Solid. M.p. 166–167 °C. H
NMR (300 MHz, CDCl3): δ = 7.56–7.54 (d, J = 7.2 Hz, 2 H), 7.30–
7.08 (m, 12 H), 6.70 (s, 1 H), 6.50 (s, 1 H), 5.55–5.53 (d, J = 5.7 Hz,
1 H), 3.23–3.15 (m, 1 H), 2.24–2.18 (m, 4 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 170.1, 147.7, 142.3, 139.5, 136.1, 132.8,
128.7, 128.2, 128.2, 127.8, 127.6, 126.9, 126.8, 124.7, 120.9, 118.1,
Experimental Section
General Remarks: Column chromatography was carried out on sil-
84.6, 77.2, 76.3, 31.2, 21.2 ppm. IR (KBr): ν = 3405, 3034, 2954,
˜
ica gel. Unless noted, 1H NMR spectra were recorded at 400 MHz
2922, 2853, 2527, 1952, 1733 cm–1. C26H22O3 (382.46): calcd. C
in CDCl3 and 13C NMR spectra were recorded at 100 MHz in 81.65, H 5.80; found C 81.82, H 5.73.
Eur. J. Org. Chem. 2009, 117–122
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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119

X.-Z. Shu, S.-C. Zhao, K.-G. Ji, Z.-J. Zheng, X.-Y. Liu, Y.-M. Liang
FULL PAPER
(R,R/S,S)-2e-2: Yield: 74.5 mg (39%). Solid. M.p. 129–130 °C. H
NMR (300 MHz, CDCl3): δ = 7.63–7.61 (d, J = 6.6 Hz, 2 H), 7.37–
1
110.4, 84.2, 77.5, 69.4, 31.3, 21.1 ppm. IR (KBr): ν = 3432, 3054,
˜
2954, 2924, 2854, 2252, 1748 cm–1. C24H20O4 (372.42): calcd. C
7.10 (m, 12 H), 6.55 (s, 1 H), 6.45 (s, 1 H), 5.65–5.63 (d, J = 6.0 Hz, 77.40, H 5.41; found C 77.34, H 5.42.
1 H), 3.17–3.10 (m, 1 H), 2.27–2.21 (m, 1 H), 2.02 (s, 3 H) ppm.
(R,R/S,S)-2i-2: Yield: 39.1 mg (21%). Solid. M.p. 88–89 °C. 1H
13C NMR (75 MHz, CDCl3): δ = 170.3, 147.6, 142.4, 139.3, 136.2,
132.5, 128.7, 128.4, 128.2, 128.1, 127.6, 127.1, 127.0, 124.8, 121.1,
NMR (400 MHz, CDCl3): δ = 7.45 (m, 1 H), 7.33–7.11 (m, 8 H),
6.89–6.88 (m, 1 H), 6.66–6.65 (m, 1 H), 6.62–6.60 (m, 2 H), 6.38–
6.36 (m, 1 H), 5.68–5.67 (d, J = 6.0 Hz, 1 H), 3.27–3.21 (m, 1 H),
3.33–3.28 (d, J = 17.2 Hz, 1 H), 2.04 (s, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 170.2, 149.4, 147.0, 142.9, 142.5, 139.4,
132.4, 128.3, 127.7, 127.1, 127.0, 126.9, 124.8, 121.0, 117.9, 111.2,
117.8, 85.2, 77.1, 74.5, 31.3, 21.1 ppm. IR (KBr): ν = 3632, 3457,
˜
3407, 3062, 3032, 2954, 2925, 1955, 1737 cm–1. C26H22O3 (382.46):
calcd. C 81.65, H 5.80; found C 81.87, H 5.74.
1
2f (10:7 dr): Yield: 158.1 mg (76%). H NMR (400 MHz, CDCl3,
110.5, 84.6, 77.4, 68.0, 31.3, 20.9 ppm. IR (KBr): ν = 3450, 3027,
˜
main isomer): δ = 7.49–7.47 (d, J = 8.4 Hz, 2 H), 7.30–7.12 (m, 11
H), 6.66 (s, 1 H), 6.45 (s, 1 H), 5.56–5.54 (d, J = 6.0 Hz, 1 H),
3.24–3.18 (m, 1 H), 2.27–2.21 (m, 1 H), 2.19 (s, 3 H) ppm. 1H
NMR (400 MHz, CDCl3, minor isomer): δ = 7.57–7.55 (d, J =
8.4 Hz, 2 H), 7.30–7.12 (m, 11 H), 6.50 (s, 1 H), 6.40 (s, 1 H), 5.63–
5.61 (d, J = 6.0 Hz, 1 H), 3.16–3.09 (m, 1 H), 2.27–2.21 (m, 1
H), 2.01 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3, mixture of
diastereoisomers): δ = 170.1, 170.0, 147.6, 147.3, 142.4, 142.3,
139.4, 139.2, 134.7, 134.7, 134.3, 134.1, 133.1, 132.8, 130.2, 130.2,
128.3, 128.3, 128.1, 127.7, 127.7, 127.3, 127.1, 127.1, 127.0, 127.0,
126.8, 124.8, 124.7, 121.1, 121.0, 118.1, 117.7, 85.0, 84.5, 77.4, 77.1,
2954, 2924, 2854, 2251, 1746 cm–1. C24H20O4 (372.42): calcd. C
77.40, H 5.41; found C 77.27, H 5.46.
1
2j (10:5 dr): Yield: 115.2 mg (72%). H NMR (400 MHz, CDCl3,
main isomer): δ = 7.30–7.04 (m, 9 H), 6.49 (s, 1 H), 5.76–5.71 (q,
J = 6.4, 13.2 Hz, 1 H), 5.62–5.60 (d, J = 5.6 Hz, 1 H), 3.28–3.22
(m, 1 H), 2.29–2.25 (d, J = 17.2 Hz, 1 H), 2.15 (s, 3 H), 1.36–1.34
(d, J = 6.4 Hz, 3 H) ppm. 1H NMR (400 MHz, CDCl3, minor
isomer): δ = 7.30–7.04 (m, 9 H), 6.39 (s, 1 H), 5.70–5.65 (q, J =
6.8, 13.2 Hz, 1 H), 5.62–5.60 (d, J = 5.6 Hz, 1 H), 3.24–3.17 (m, 1
H), 2.30–2.26 (d, J = 17.2 Hz, 1 H), 2.00 (s, 3 H), 1.46–1.44 (d,
J = 6.4 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3, mixture of
diastereoisomers): δ = 170.6, 170.4, 147.8, 147.2, 142.5, 142.5,
139.3, 139.2, 132.8, 132.7, 128.2, 128.2, 127.7, 127.6, 127.5, 127.0,
127.0, 127.0, 126.8, 124.6, 124.6, 120.9, 117.8, 117.6, 84.9, 84.5,
75.6, 73.8, 31.3, 21.2, 20.9 ppm. IR (KBr): ν = 3664, 3462, 3054,
˜
3029, 2953, 2924, 2855, 2250, 1948, 1901, 1739 cm–1. C26H21ClO3
(416.90): calcd. C 74.91, H 5.08; found C 74.77, H 5.21.
1
2g (10:9 dr): Yield: 170.3 mg (86%). H NMR (400 MHz, CDCl3,
77.3, 76.8, 71.0, 69.6, 31.2, 21.1, 20.9, 14.8, 14.6 ppm. IR (KBr): ν
˜
main isomer): δ = 7.46–7.44 (d, J = 8.0 Hz, 2 H), 7.25–7.04 (m, 11
H), 6.71 (s, 1 H), 6.48 (s, 1 H), 5.54–5.52 (d, J = 6.0 Hz, 1 H),
3.21–3.15 (m, 1 H), 2.22–2.18 (m, 1 H), 2.21 (s, 3 H), 2.15 (s, 3 H)
ppm. 1H NMR (400 MHz, CDCl3, minor isomer): δ = 7.53–7.51
(d, J = 8.0 Hz, 2 H), 7.25–7.04 (m, 11 H), 6.54 (s, 1 H), 6.46 (s, 1
H), 5.62–5.60 (d, J = 6.0 Hz, 1 H), 3.13–3.07 (m, 1 H), 2.26 (s, 3
= 3452, 3052, 3027, 2987, 2939, 2902, 2251, 1951, 1733 cm–1.
C21H20O3 (320.39): calcd. C 78.73, H 6.29; found C 78.92, H 6.13.
1
2k (10:5 dr): Yield: 144.5 mg (73%). H NMR (400 MHz, CDCl3,
main isomer): δ = 7.33–7.13 (m, 14 H), 6.49 (s, 1 H), 6.05–6.01 (m,
1 H), 5.67–5.65 (d, J = 6.0 Hz, 1 H), 3.30–3.19 (m, 1 H), 3.13–2.92
1
H), 2.22–2.18 (m, 1 H), 1.96 (s, 3 H) ppm. 13C NMR (100 MHz, (m, 2 H), 2.31–2.27 (d, J = 17.2 Hz, 1 H), 1.97 (s, 3 H) ppm. H
CDCl3, mixture of diastereoisomers): δ = 170.1, 170.0, 147.8, 147.6,
142.4, 142.3, 139.5, 139.3, 138.0, 137.8, 133.2, 133.1, 132.7, 132.3,
128.8, 128.7, 128.6, 128.5, 128.2, 128.1, 127.7, 127.5, 127.2, 126.9,
126.8, 124.7, 124.6, 120.9, 120.8, 118.1, 117.7, 85.2, 84.6, 77.2, 76.2,
NMR (400 MHz, CDCl3, minor isomer): δ = 7.33–7.13 (m, 14 H),
6.35 (s, 1 H), 5.98–5.94 (m, 1 H), 5.67–5.65 (d, J = 6.0 Hz, 1 H),
3.30–3.19 (m, 1 H), 3.13–2.92 (m, 2 H), 2.33–2.28 (d, J = 17.2 Hz,
1 H), 1.81 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3, mixture of
diastereoisomers): δ = 170.5, 170.2, 147.6, 147.2, 142.3, 142.3,
139.3, 139.2, 137.7, 137.5, 132.8, 132.6, 129.4, 129.3, 128.3, 128.2,
127.7, 127.6, 127.2, 127.1, 127.0, 126.9, 126.5, 126.4, 124.7, 124.7,
121.1, 121.0, 117.9, 117.6, 85.3, 84.9, 77.4, 74.5, 73.3, 36.2, 35.7,
74.3, 31.2, 31.2, 21.1, 21.1, 21.0, 20.9 ppm. IR (KBr): ν = 3459,
˜
3051, 3028, 2952, 2923, 2858, 2248, 1948, 1904, 1739 cm–1.
C27H24O3 (396.48): calcd. C 81.79, H 6.10; found C 81.73, H 6.21.
1
2h (10:8 dr): Yield: 170.3 mg (73%). H NMR (400 MHz, CDCl3,
31.3, 31.3, 20.7, 20.6 ppm. IR (KBr): ν = 3652, 3454, 3061, 3028,
˜
main isomer): δ = 7.29–7.00 (m, 11 H), 6.68–6.66 (d, J = 8.4 Hz, 1
H), 6.66 (s, 1 H), 6.42 (s, 1 H), 5.83–5.81 (m, 2 H), 5.58–5.56 (d, J
= 6.0 Hz, 1 H), 3.25–3.19 (m, 1 H), 2.25–2.21 (m, 1 H), 2.18 (s, 3
H) ppm. 1H NMR (400 MHz, CDCl3, minor isomer): δ = 7.29–
7.00 (m, 11 H), 6.75–6.73 (d, J = 8.0 Hz, 1 H), 6.47 (s, 1 H), 6.40
(s, 1 H), 5.87–5.85 (m, 2 H), 5.64–5.63 (d, J = 6.0 Hz, 1 H), 3.17–
3.11 (m, 1 H), 2.25–2.21 (m, 1 H), 1.98 (s, 3 H) ppm. 13C NMR
(100 MHz, CDCl3, mixture of diastereoisomers): δ = 170.2, 170.1,
147.8, 147.6, 147.6, 147.4, 147.2, 142.4, 142.3, 139.5, 139.2, 132.9,
132.3, 129.9, 128.3, 128.2, 127.6, 127.6, 127.1, 126.9, 126.9, 124.7,
124.7, 122.8, 122.7, 121.0, 120.9, 118.2, 117.7, 109.4, 109.3, 107.7,
107.5, 100.9, 100.9, 85.2, 84.6, 77.3, 77.1, 76.1, 74.1, 31.3, 31.2,
2955, 2926, 2901, 2854, 2821, 2250, 1950, 1741 cm–1. C27H24O3
(396.48): calcd. C 81.79, H 6.10; found C 81.53, H 6.29.
1
2l: Yield: 41.7 mg (25%). Solid. H NMR (400 MHz, CDCl3): δ =
7.31–7.13 (m, 9 H), 6.81 (s, 1 H), 5.57–5.56 (d, J = 6.0 Hz, 1 H),
3.22–3.15 (m, 1 H), 2.30–2.26 (d, J = 17.2 Hz, 1 H), 2.20 (s, 3 H),
1.77 (s, 3 H), 1.63 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 169.8, 147.9, 143.1, 139.9, 132.3, 128.3, 127.6, 127.5, 126.8, 124.8,
120.8, 119.7, 86.7, 84.0, 76.9, 31.5, 22.6, 21.6, 21.0 ppm. IR (KBr):
ν = 3456, 3054, 2987, 2924, 2853, 1946, 1739 cm–1. C H O
˜
22 22
3
(334.41): calcd. C 79.02, H 6.63; found C 79.23, H 6.54.
2m: Yield: 65.6 mg (41%). Solid. 1H NMR (400 MHz, CDCl3): δ
= 7.30–7.17 (m, 8 H), 7.09–7.08 (m, 1 H), 6.48 (s, 1 H), 4.89–4.86
(d, J = 12 Hz, 1 H), 4.58–4.54 (d, J = 12.4 Hz, 1 H), 2.98–2.93 (m,
1 H), 2.39–2.34 (m, 1 H), 2.13 (s, 3 H), 1.83 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 171.2, 147.2, 145.6, 139.2, 135.3,
128.3, 127.7, 127.3, 127.0, 126.5, 124.8, 120.3, 117.4, 82.1, 82.0,
21.2, 21.0 ppm. IR (KBr): ν = 3457, 3050, 3026, 2954, 2924, 2901,
˜
2856, 2778, 2249, 1743 cm–1. C27H22O5 (426.47): calcd. C 76.04, H
5.20; found C 76.32, H 5.09.
1
(R,S/S,R)-2i-1: Yield: 50.2 mg (27%). Solid. M.p. 148–149 °C. H
NMR (400 MHz, CDCl3): δ = 7.37–7.36 (m, 1 H), 7.30–7.21 (m, 6
H), 7.18–7.15 (m, 3 H), 6.64 (s, 1 H), 6.62–6.61 (m, 1 H), 6.45 (m,
1 H), 6.29–6.27 (m, 1 H), 5.64–5.63 (d, J = 6.0 Hz, 1 H), 3.29–3.23
(m, 1 H), 2.32–2.27 (m, 1 H), 2.19 (s, 3 H) ppm. 13C NMR
64.9, 38.0, 24.2, 20.9 ppm. IR (KBr): ν = 3462, 3029, 2926, 2249,
˜
1952, 1741 cm–1. C21H20O3 (320.39): calcd. C 78.73, H 6.29; found
C 78.57, H 6.32.
(100 MHz, CDCl3): δ = 170.2, 149.5, 147.6, 142.5, 142.2, 139.5, 2n: Yield: 151.3 mg (89%). Solid. M.p. 153–154 °C. 1H NMR
133.0, 128.3, 127.7, 127.2, 127.1, 127.0, 124.9, 121.0, 118.2, 110.7,
(400 MHz, CDCl3): δ = 7.28–7.16 (m, 7 H), 7.09 (m, 1 H), 6.41 (s,
120
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 117–122

Synthesis of 8-Oxabicyclo[3.2.1]octane Derivatives
1 H), 5.58–5.56 (d, J = 6.0 Hz, 1 H), 4.76–4.73 (d, J = 12.4 Hz, 1 J = 6.0 Hz, 1 H), 4.65–4.62 (d, J = 12.4 Hz, 1 H), 4.54–4.49 (d, J
H), 4.60–4.57 (d, J = 12 Hz, 1 H), 3.27–3.21 (m, 1 H), 2.30–2.25
(d, J = 17.6 Hz, 1 H), 2.11 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 170.8, 149.2, 141.2, 138.9, 133.9, 132.8, 128.3, 127.9,
127.1, 125.9, 124.8, 122.2, 118.3, 82.0, 77.0, 64.1, 31.1, 20.7 ppm.
= 12.4 Hz, 1 H), 2.77–2.71 (m, 1 H), 2.10–2.06 (m, 4 H), 1.99–1.93
(m, 1 H), 1.78–1.61 (m, 3 H), 1.39–1.28 (m, 1 H), 1.00–0.90 (m, 1
H), 0.79–0.70 (m, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
171.1, 148.9, 140.4, 138.7, 126.8, 126.2, 123.2, 122.1, 117.4, 82.5,
IR (KBr): ν = 3466, 3058, 3032, 2855, 2924, 2855, 2253, 1883, 81.2, 64.5, 39.6, 34.0, 27.6, 26.8, 25.2, 20.9 ppm. IR (neat): ν =
˜
˜
1742 cm–1. C20H17ClO3 (340.81): calcd. C 70.49, H 5.03; found C 3467, 3069, 3024, 2929, 2855, 2657, 2249, 1743 cm–1. C18H20O3
70.32, H 5.08.
(284.35): calcd. C 76.03, H 7.09; found C 76.11, H 7.33.
3f: Yield: 87.9 mg (46%). Solid. M.p. 182–183 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.48–7.43 (m, 3 H), 7.30–7.07 (m, 11 H),
6.57 (s, 1 H), 5.35 (s, 1 H), 4.85–4.82 (d, J = 12.4 Hz, 1 H), 4.78–
4.75 (d, J = 12.0 Hz, 1 H), 3.71 (s, 1 H), 2.16 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 171.1, 148.1, 142.4, 142.1, 138.9,
135.7, 128.7, 128.7, 128.6, 128.2, 127.5, 127.2, 126.8, 125.9, 121.6,
2o: Quantitative yield. Solid. M.p. 136–137 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.28–7.06 (m, 7 H), 6.93–6.92 (d, J =
7.6 Hz, 1 H), 6.50 (s, 1 H), 5.57–5.55 (d, J = 5.6 Hz, 1 H), 4.98–
4.95 (d, J = 12.4 Hz, 1 H), 4.63–4.60 (d, J = 12.4 Hz, 1 H), 3.20–
3.15 (m, 1 H), 2.31 (s, 3 H), 2.27–2.23 (d, J = 17.6 Hz, 1 H), 2.04
(s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.9, 145.1,
142.9, 139.2, 133.9, 129.3, 128.2, 127.9, 127.7, 127.2, 125.2, 124.7,
117.8, 84.3, 82.7, 64.3, 47.5, 20.9 ppm. IR (KBr): ν = 3449, 3058,
˜
3026, 2949, 2883, 2251, 1952, 1740 cm–1. C26H22O3 (382.46): calcd.
C 81.65, H 5.80; found C 81.79, H 5.77.
118.5, 83.1, 76.5, 65.2, 31.2, 20.7, 19.0 ppm. IR (KBr): ν = 3052,
˜
3026, 2955, 2924, 2857, 2729, 2250, 1951, 1740 cm–1. C21H20O3
(320.39): calcd. C 78.73, H 6.29; found C 78.94, H 6.21.
1
3g (10:8 dr): Yield: 156.3 mg (81%). H NMR (400 MHz, CDCl3,
3a: Yield: 90.1 mg (53%). Solid. M.p. 129–130 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.34–7.33 (d, J = 6.8 Hz, 1 H), 7.25–7.17
(m, 6 H), 7.11–7.09 (m, 1 H), 6.45 (s, 1 H), 5.62–5.60 (d, J = 6.0 Hz,
1 H), 4.82–4.79 (d, J = 12.4 Hz, 1 H), 4.62–4.59 (d, J = 12.4 Hz, 1
H), 3.25–3.18 (m, 1 H), 2.28–2.24 (m, 1 H), 2.12 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 171.0, 147.0, 142.6, 137.7, 133.5,
132.4, 128.4, 127.3, 127.2, 127.1, 126.1, 121.2, 117.5, 82.1, 77.3,
main isomer): δ = 7.52–7.50 (m, 2 H), 7.32–7.07 (m, 7 H), 6.37 (s,
1 H), 5.98 (s, 1 H), 5.65–5.56 (m, 2 H), 5.12–5.11 (d, J = 5.6 Hz, 1
H), 3.25–3.22 (m, 1 H), 2.78–2.32 (m, 3 H), 2.27 (s, 3 H), 2.16–2.11
(m, 2 H), 2.05–1.88 (m, 1 H), 1.66–1.60 (m, 1 H), 1.27–1.22 (m, 1
H) ppm. 1H NMR (400 MHz, CDCl3, minor isomer): δ = 7.58–
7.55 (m, 2 H), 7.32–7.07 (m, 7 H), 6.39 (s, 1 H), 5.77 (s, 1 H), 5.46–
5.42 (m, 2 H), 5.18–5.17 (d, J = 5.6 Hz, 1 H), 3.15–3.11 (m, 1 H),
2.78–2.32 (m, 3 H), 2.16–2.11 (m, 2 H), 2.06 (s, 3 H), 2.05–1.88
(m, 1 H), 1.66–1.60 (m, 1 H), 1.27–1.22 (m, 1 H) ppm. 13C NMR
(100 MHz, CDCl3, mixture of diastereoisomers): δ = 170.2, 170.1,
149.4, 149.2, 141.3, 140.8, 140.3, 140.1, 136.2, 136.1, 131.8, 131.7,
129.0, 128.8, 128.1, 128.0, 127.9, 127.7, 126.7, 126.6, 126.1, 126.0,
125.9, 125.6, 125.2, 125.2, 123.0, 122.9, 118.1, 117.8, 85.0, 84.6,
81.8, 81.6, 76.1, 74.5, 37.0, 35.2, 35.0, 31.1, 30.9, 26.8, 26.8, 23.9,
64.5, 31.2, 20.8 ppm. IR (KBr): ν = 3466, 3069, 3046, 2952, 2900,
˜
2251, 1900, 1742 cm–1. C20H17ClO3 (340.81): calcd. C 70.49, H
5.03; found C 70.61, H 5.05.
1
3b: Yield: 131.2 mg (82%). Oil. H NMR (400 MHz, CDCl3): δ =
7.32–7.31 (m, 1 H), 7.19–7.16 (m, 4 H), 7.09–7.04 (m, 3 H), 6.40
(s, 1 H), 5.60–5.59 (d, J = 6.0 Hz, 1 H), 4.81–4.78 (d, J = 12.0 Hz,
1 H), 4.63–4.60 (d, J = 12.4 Hz, 1 H), 3.26–3.20 (m, 1 H), 2.31–
2.26 (d, J = 17.2 Hz, 1 H), 2.28 (s, 3 H), 2.10 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 171.0, 147.2, 142.8, 137.5, 136.4,
133.2, 128.9, 127.1, 126.9, 125.7, 124.6, 121.1, 117.4, 82.2, 77.4,
23.9, 21.2, 21.0 ppm. IR (KBr): ν = 3655, 3462, 3067, 3010, 2932,
˜
2883, 2827, 2246, 1950, 1738 cm–1. C26H26O3 (386.49): calcd. C
80.80, H 6.78; found C 80.62, H 6.89.
X-ray Crystallography: The molecular structure of product 2e-1
was determined by X-ray crystallography. CCDC-695098 contains
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
64.5, 31.2, 20.9, 20.8 ppm. IR (neat): ν = 3651, 3464, 3026, 2950,
˜
2920, 2250, 1903, 1741 cm–1. C21H20O3 (320.39): calcd. C 78.73, H
6.29; found C 78.92, H 6.17.
3c: Yield: 72.9 mg (51%). Oil. 1H NMR (400 MHz, CDCl3): δ =
7.29–7.26 (m, 1 H), 7.19–7.15 (m, 2 H), 7.03–7.01 (m, 1 H), 5.72
(s, 1 H), 5.45–5.43 (d, J = 6.0 Hz, 1 H), 4.70–4.67 (d, J = 12.0 Hz,
1 H), 4.54–4.51 (d, J = 12.0 Hz, 1 H), 2.85–2.79 (m, 1 H), 2.09 (s,
3 H), 1.84–1.76 (m, 3 H), 1.31–1.23 (m, 2 H), 1.19–1.12 (m, 2 H),
0.83–0.79 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 171.1,
147.8, 142.9, 135.9, 126.8, 126.7, 124.6, 120.9, 117.1, 82.0, 77.3,
Supporting Information (see footnote on the first page of this arti-
1
cle): Detailed experimental procedures; H and 13C NMR spectra;
crystal data and structure refinement data for 2e-1.
Acknowledgments
64.5, 36.0, 32.8, 29.0, 22.0, 20.8, 13.8 ppm. IR (neat): ν = 3467,
˜
3069, 3044, 3025, 2955, 2929, 2866, 1743 cm–1. C18H22O3 (286.37):
calcd. C 75.50, H 7.74; found C 75.53, H 7.49.
We thank the NSF (NSF-20621091, NSF-20672049) and the “Hun-
dred Scientist Program” from the Chinese Academy of Sciences for
financial support.
3d: Yield: 39.3 mg (21%). Oil. 1H NMR (400 MHz, CDCl3): δ =
7.30–7.28 (m, 1 H), 7.21–7.14 (m, 2 H), 7.05–7.03 (m, 1 H), 5.98
(s, 1 H), 5.49–5.48 (d, J = 6.0 Hz, 1 H), 4.73–4.70 (d, J = 12.0 Hz,
1 H), 4.56–4.53 (d, J = 12.0 Hz, 1 H), 3.94–3.84 (m, 2 H), 2.84–
2.78 (m, 1 H), 2.10 (s, 3 H), 1.87–1.83 (d, J = 17.6 Hz, 1 H), 0.83
(s, 9 H), –0.04 (s, 3 H), –0.09 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 171.1, 147.5, 142.8, 135.2, 127.0, 126.9, 124.9, 121.1,
117.4, 82.0, 77.2, 65.8, 64.5, 30.1, 25.8, 20.8, 18.2, –5.41, –5.43 ppm.
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˜
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8.13.
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7.21–7.16 (m, 3 H), 7.06–7.04 (m, 1 H), 5.67 (s, 1 H), 5.20–5.18 (d,
Eur. J. Org. Chem. 2009, 117–122
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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121

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[10]
During the preparation of this work, Iwasawa and coworkers
reported that acyclic γ,δ-ynones could also react with electron-
rich alkenes with an 1,2-alkyl migration process under plati-
num catalysis, see: H. Kusama, K. Ishida, H. Funami, N. Iwas-
awa, Angew. Chem. 2008, 120, 4981–4983; Angew. Chem. Int.
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[11] As alkynes, propargylic esters have not been previously intro-
duced into the cyclization of o-alkynyl(oxo)benzenes. The de-
tailed effect is worthy of further study. For recent reviews on
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[12] For selected examples on 1,2-H shift induced by metal carb-
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Received: September 11, 2008
Published Online: November 12, 2008
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