Gold(I)-Catalyzed Stereospecific [4+3]-Cycloaddition Reaction of 1-(Alk-1-ynyl)cyclopropyl Ketones with Nitrones: A Modular Entry to Enantioenriched 5,7-Fused Bicyclic Furo[3,4- d ][1,2]oxazepines

Article abstract of DOI:10.1055/s-0035-1561276

In our previous study, a gold(I)-catalyzed stereoselective formal [4+3]-cycloaddition reaction of 1-(alk-1-ynyl)cyclopropyl ketones with nitrones was found to afford 5,7-fused bicyclic furo[3,4-d][1,2]oxazepines in good to excellent yields with high diast

Full text of DOI:10.1055/s-0035-1561276

SYNTHESIS
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
© Georg Thieme Verlag Stuttgart · New York
2016, 48, 512–519
feature
512
Y. Zhang et al.
Feature
Synthesis
Gold(I)-Catalyzed Stereospecific [4+3]-Cycloaddition Reaction of
1-(Alk-1-ynyl)cyclopropyl Ketones with Nitrones: A Modular Entry
to Enantioenriched 5,7-Fused Bicyclic Furo[3,4-d][1,2]oxazepines
Yanqing Zhanga,b
Yuanjing Xiao*a
Junliang Zhang*a,c
–O
R5
R5
R3
R3
R3
N+
O
N
kinetic resolution
nitrones
R4
R2
R4
R2
R2
R1
R1
Ph3PAuOTf
CH2Cl2, r.t.
a Shanghai Key Laboratory of Green Chemistry and Chemical
Processes, School of Chemistry and Molecular Engineering,
East China Normal University, 3663 N. Zhongshan Road,
Shanghai, 200062, P. R. of China
chiral gold(I)
mild conditions
R1
O
O
O
(1R,2S)
up to 99% ee
rac
(1R,4R)
up to 99% ee
yjxiao@chem.ecnu.edu.cn
b Patent Examination Cooperation Jiangsu Center of the Patent
Office, Sipo, 88N. Guangqi Road, Suzhou, Jiangsu 215163,
P. R. of China
c State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, CAS. 345 Lingling Road,
Shanghai, 200032, P. R. of China
jlzhang@chem.ecnu.edu.cn
Received: 12.10.2015
Accepted after revision: 06.11.2015
Published online: 11.01.2016
which provides rapid and general access to furan-fused six-
membered carbo- or heterocyclic rings with notable regio-
selectivity.3a In their subsequent publication, an alternative
reaction pathway was observed when ethyl vinyl ether was
employed as the reaction partner, affording highly strained
bicyclo[3.2.0]heptanes.3b In addition, in our laboratory we
also developed a rhodium(I)-catalyzed carbonylation reac-
tion of 1-(alk-1-ynyl)cyclopropyl ketones that leads to
fused 5,5-bicyclic furans.4
DOI: 10.1055/s-0035-1561276; Art ID: ss-2015-z0602-fa
Abstract In our previous study, a gold(I)-catalyzed stereoselective for-
mal [4+3]-cycloaddition reaction of 1-(alk-1-ynyl)cyclopropyl ketones
with nitrones was found to afford 5,7-fused bicyclic furo[3,4-d][1,2]ox-
azepines in good to excellent yields with high diastereoselectivity cata-
lyzed by (triphenylphosphine)gold(I) triflate. In order to gain insight
into the mechanism of this [4+3] cycloaddition process, an enantiose-
lective version used a MeO-DTBM-BIPHEP derived gold(I) complex as
the catalyst, which resulted in the kinetic resolution of the 1-(alk-1-
ynyl)cyclopropyl ketones, affording the recovered ketones in high yield
with excellent enantioselectivity. An interesting chirality transfer was
observed in the gold(I)-catalyzed [4+3] cycloaddition of optically active
1-(alk-1-ynyl)cyclopropyl ketones with nitrones, indicating the reaction
undergoes a stereospecific SN2-type ring-opening of the cyclopropane.
Following our previous interest in gold catalysis,5 de-
signing and developing novel regio-divergent reactions,6 in
our previous work we observed that the cycloaddition pat-
tern of 1-(alk-1-ynyl)cyclopropyl ketones 1 with nitrones 2
can be altered by the selection of the catalyst. The reaction
of 1-(alk-1-ynyl)cyclopropyl ketones 1 with nitrones 2 cata-
lyzed by (triphenylphosphine)gold(I) triflate undergoes a
formal [4+3] cycloaddition to afford 5,7-fused bicyclic fu-
ro[3,4-d][1,2]oxazepines 3 in good to excellent yields with
excellent diastereoselectivity. Whereas the reaction of 1-
(alk-1-ynyl)cyclopropyl ketones 1 with nitrones 2 catalyzed
by scandium(III) triflate undergoes formal [3+3] cycloaddi-
tion to give tetrahydro-1,2-oxazines 4 in moderate to excel-
lent yields with up to 15.7:1 diastereomeric ratio (Scheme
1).7
Two controversial reaction pathways via either an un-
usual SN2 process or racemization through ring opening
and reclosure of the cyclopropane moiety have been pro-
posed to account for the formation of cycloadduct 3
(Scheme 2). In order to determine the real mechanism, the
[4+3] cycloaddition of enantioenriched 1-(alk-1-ynyl)cyclo-
propyl ketones 1 with nitrones was examined to see wheth-
er a chirality transfer takes place or not. Enantioenriched 1-
(alk-1-ynyl)cyclopropyl ketones 1 were obtained by kinetic
resolution reaction in good yield with excellent enantiose-
Key words gold, kinetic resolution, cycloaddition, fused-ring systems,
synthetic methods
Gold-catalyzed chemical transformations of strained
small-ring-containing molecules have drawn increased at-
tention and they have emerged as powerful methods for
the rapid construction of interesting carbocycles and het-
erocycles.1 In this context, 1-(alk-1-ynyl)cyclopropyl ke-
tones bearing carbonyl, alkynyl, and cyclopropyl groups
have received particularly attention due to their ease of
preparation, unique structure, and reactivity.
In 2006, Schmalz and Zhang reported the first example
of a gold(I)-catalyzed tandem nucleophilic addition and
heterocyclization of 1-(alk-1-ynyl)cyclopropyl ketones to
afford trisubstituted furans in high yields.2 In 2008, Zhang
and co-workers developed an efficient gold-catalyzed for-
mal [4+2] annulation with carbonyl compounds, imines,
and polarized alkenes, such as indoles and silyl enol ethers,
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, 512–519

513
Y. Zhang et al.
Feature
Synthesis
R2
R3
R5
R5
O
R3
O
O
N
N
–O
R5
conditions B
R3
conditions A
N+
R4
R2
+
R4
O
formal [4+3]
cycloaddition
formal [3+3]
cycloaddition
R4
O
R1
R1
R1
4
R2
3
rac-1
2
up to 99%
d.r. >20:1
up to 97%
d.r. up to 15.7:1
conditions A: Sc(OTf)3/1,10-phenanthroline (10 mol%)
MS 4Å, DCE, 28–32 °C
conditions B: Ph3PAuOTf (2 mol%), CH2Cl2, r.t.
Scheme 1 Catalytic regioselective control in the diastereoselective cycloaddition reactions of 1-(alk-1-ynyl)cyclopropyl ketones with nitrones
lectivity.8 To the best of our knowledge, this is the first ex-
ample of kinetic resolution of racemates by a gold catalyst,9
although gold-catalyzed asymmetric cyclopropanation or
cyclopropenation reactions are well developed.10,11 Herein,
we report a comprehensive study of this gold(I)-catalyzed
enantioselective formal [4+3]-cycloaddition reaction.
In order to clarify whether the reaction proceeds via an
unusual SN2 process or racemization through ring opening
and reclosure of the cyclopropane moiety (Scheme 2), we
envisaged that this issue may be addressed by using opti-
cally active 1-(alk-1-ynyl)cyclopropyl ketones as the sub-
strates. Two approaches are available to obtain the optically
active cyclopropyl ketones, 1. asymmetric cyclopropanation
Biographical Sketches
Yanqing Zhang was born in
Henan Province, China, in 1983.
She received her Bachelor de-
gree from Luoyang Normal Uni-
versity in China in 2007 and her
Ph.D. from East China Normal
University under the supervi-
sion of Professor Junliang Zhang
in 2012. Since July 2012, she has
worked in the Patent Examina-
tion Cooperation Jiangsu Center
of the Patent Office. Her re-
search interests are transition-
metal-directed organic synthe-
sis and asymmetric catalysis.
Yuanjing Xiao was born in Hu-
bei Province, China, in 1974. He
received his Bachelor degree
from Hubei University in China
in 1997 and his Ph.D. from Wu-
han University under the super-
vision of Professor Yongbing He
and Professor Chengtai Wu in
2002. From 2002 to 2006, he
worked in the laboratory of Pro-
fessor Liping Yang at East China
Normal University as a lecturer.
From 2007 to 2010, he worked
with Professor Junliang Zhang in
East China Normal University as
a postdoctoral fellow and then
he was appointed as an associ-
ated professor. From October
2011 to October 2012, he visit-
ed the laboratory of Prof. Liming
Zhang at the University of Cali-
fornia, Santa Barbara as a Visit-
ing Scholar. His research
interest focuses on diversity ori-
ented
organic
synthesis,
asymmetric catalysis, and devel-
oping novel fluorinated building
blocks and their transformation.
Junliang Zhang received his
Bachelor degree from Tianjing
University in China in 1997 and
his Ph.D. from the Shanghai In-
stitute of Organic Chemistry un-
der the supervision of Professor
Shengming Ma in 2002. He con-
ducted his postdoctoral re-
search at University of Cologne
as a Humboldt Fellow with Pro-
fessor Hans-Günther Schmalz
(Germany, 2003–2004). In 2005
he moved to the United States
for postdoctoral work with Pro-
fessors Chuan He and Stephen
Kent at the University of Chica-
go (2005–2006). He started his
independent career as
a full
professor at East China Normal
University at the end of 2006.
His research interest focuses on
the development of synthetic
methodology based on enynes
and asymmetric catalysis.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, 512–519

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Y. Zhang et al.
Feature
Synthesis
R2
O
R2
O
Nu–
R3
2
R3
AuL
R2
R3
enantioenriched
1
3
AuIL
AuIL
racemic
stereochemistry
inversion at 2-position
R1
racemization
O+
R1
R1
(1R,2S)-1
(1S,2R)-1
Scheme 2 Two possible reaction pathways via an unusual SN2 process or consisting of the racemization through ring-opening and reclosure of cyclo-
propane moiety proposed for the gold-catalyzed cycloaddition reactions of 1-(alk-1-ynyl)cyclopropyl ketones
of the corresponding 2-(alk-1-ynyl)alk-2-en-1-ones, and 2.
kinetic resolution12 of the racemic 1-(alk-1-ynyl)cyclopro-
pyl ketones. Gold-catalyzed asymmetric cyclopropanation
reactions are known,10 but there are no reported examples
leading to optically active 1-(alk-1-ynyl)cyclopropyl ke-
tones. Unfortunately, our attempts to obtain optically active
1-(alk-1-ynyl)cyclopropyl ketones by direct asymmetric cy-
clopropanation of the corresponding 2-(alk-1-ynyl)alk-2-
en-1-ones failed (Scheme 3).
1. The reactions of (1R, 2S)-1a with various nitrones 2a–f
afforded the desired products in high yields with excellent
enantiomeric excess as a single diastereomer (Table 1, en-
tries 1–6). Moreover, different functional groups on the
substrate (1R,2S)-1 (R1, R2, and R3) and nitrone 2 (R4 and R5)
were compatible and the desired heterobicyclic products 3
were isolated in high to excellent yields with excellent en-
antiomeric excess and diastereomeric ratio (>20:1) (Table 1,
entries 7–9 and 11–17), with the exception of 3ed (Table 1,
entry 10); even reducing the reaction temperature in the
addition of 1e and 2d to 0 °C did not improve the enantio-
meric excess of 3ed. This result indicates that when R3 is a
strong electron-donating 4-methoxyphenyl group, 1e may
undergo racemization under the reaction conditions, which
was consistent with our findings in the DyKAT study.8 In
some cases, racemic products 3 could not be efficiently sep-
arated by chiral HPLC, thus other nitrones were used to ob-
tain the enantiomeric excess. The structure and absolute
stereochemistry of (1R,4R)-3ib with a bromine atom was
confirmed by single-crystal X-ray diffraction analysis (Fig-
ure 1);15 All other compounds were assumed to have the
same configuration as (1R,4R)-3ib.
R3
asymmetric
cyclopropanation
R2
x
R1
failed
O
R3
AuCl(SMe2) (5 mol%)
(S)-MeO-DTBM-BIPHEP
R5
(3 mol%)
R3
–O
N+
R2
+
R2
R1
R1
AgOTf (5 mol%)
DCE, 4 Å MS, r.t.
R4
O
O
kinetic resolution
worked well!
rac-1
2
(1R,2S)-1
up to 99% ee
easily made
Scheme 3 Kinetic resolution of 1-(alk-1-ynyl)cyclopropyl ketones with
a nitrone catalyzed by a chiral gold(I) species
We next turned our attention to the kinetic resolution
of racemic 1-(alk-1-ynyl)cyclopropyl ketones catalyzed by
chiral gold(I) species.13,14 After screening a series of gold(I)
complexes with chiral ligands, we are pleased to find that
optically active (1R,2S)-1-(alk-1-ynyl)cyclopropyl ketones 1
were efficiently obtained by the kinetic resolution of the
readily available racemic 1-(alk-1-ynyl)cyclopropyl ketones
catalyzed by an (S)-MeO-DTBM-BIPHEP-derived gold(I)
complex (Scheme 3).8
The gold(I)-catalyzed [4+3] annulations of optically ac-
tive (1R,2S)-1-(alk-1-ynyl)cyclopropyl ketones 1 with ni-
trones were then investigated and the result are listed in Ta-
ble 1. In general, reaction of (1R,2S)-1 catalyzed by (tri-
phenylphosphine)gold(I) triflate gives enantioenriched 5,7-
fused bicyclic furo[3,4-d][1,2]oxazepines 3 with the same
level of enantiomeric purity as that of the starting material
Figure 1 X-ray crystal structure of 3ib
Based on the above results, a mechanistic rationale for
chirality transfer in gold(I)-catalyzed [4+3]-cycloaddition
reactions proceeding via a stereospecific SN2 process on the
2-substituted cyclopropane is depicted in Scheme 4. The
coordination of gold(I) with the alkyne and carbonyl group
of (1R,2S)-1 would give intermediate IA, the subsequent
heterocyclization of IA gives the oxonium-containing vinyl–
gold intermediate IB. This is followed by stereospecific nuc-
leophilic attack of nitrone 2 at the more substituted posi-
tion of the cyclopropyl ring,2,16 leading to inversion at that
position, which produces furanyl–gold intermediate IC.
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Y. Zhang et al.
Feature
Synthesis
Table 1 Gold(I)-Catalyzed [4+3]-Annulations of Optically Active (1R,2S)-1-(Alk-1-ynyl)cyclopropyl Ketones 1 with Nitrones
R5
R3
O
R3
N
Ph3PAuOTf
(2 mol%)
–O
R5
R4
R2
N+
R2
+
CH2Cl2, r.t., 30 min
R1
R1
R4
2a
O
O
(1R,2S)-1
(1R,4R)-3
enantioenriched
Entry
Substrate 1
Nitrone 2
Product 3
R1
Me
R2
Ph
R3
ee (%)
R4
Ph
R5
Ph
Yield (%) ee (%)
1
2
1a
1a
1a
1a
1a
1a
1b
1c
1d
1e
1f
Ph
Ph
Ph
Ph
Ph
Ph
92
92
92
92
92
92
95
87
94
93
96
97
99
97
99
92
92
2a
2b
2c
2d
2e
2f
3aa
3ab
3ac
3ad
3ae
3af
84
87
88
80
80
78
85
96
85
95
88
82
85
75
78
67
80
91
88
94
91
90
94
94
85
92
26
98
92
98
97
99
92
87
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
2-furyl
Ph
Ph
Ph
Ph
Bn
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
3a
4-O2NC6H4
4-MeOC6H4
(E)-styryl
Ph
4
5
6
7
1-naphthyl
Ph
Ph
Ph
2a
2a
2b
2d
2b
2b
2d
2b
2d
2d
2b
Ph
3ba
3ca
3db
3ed
3fb
3gb
3hd
3ib
8b,c
9
4-MeC6H4
Ph
4-BrC6H4
Ph
2-furyl
10b,c
11a,b
12
13
14
15
16
17b
4-MeOC6H4
4-MeC6H4
4-ClC6H4
2-BrC6H4
4-BrC6H4
Ph
4-MeOC6H4
2-furyl
Ph
1g
1h
1i
Ph
2-furyl
Ph
4-MeOC6H4
2-furyl
Ph
1j
Ph
4-MeOC6H4
4-MeOC6H4
2-furyl
3jd
1k
1l
Ph
Ph
4-ClC6H4
Ph
3kd
3lb
4-ClC6H4
Ph
a The reaction was carried out at 0 °C.
b The reaction was complete after 2 h.
c The reaction was complete after 1 h.
LAuI
(1R,2S)-1
(1R,4R)-3
R4
R3
R3
AuL
O
N
R3
Kint
R2
R2
R2
R1
R1
R5
O
R1
R3 = PMP
AuL
AuL
O
O
IC
R4
IA
ent-IA
N+
R5
O–
R3
2
Path a
AuL
R2
2
R1
O+
IB
Scheme 4 A mechanistic rationale for chirality transfer in gold(I)-catalyzed [4+3]-cycloaddition reaction
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, 512–519

516
Y. Zhang et al.
Feature
Synthesis
Ring closure via a chairlike conformation would afford the
cycloadduct and regenerate the gold(I) catalyst. Our find-
ings with regard to the absolute configurations of the [4+3]
cycloadducts (1R,4R)-3a and (1R,2S)-1a are consistent with
this proposal. Consistent with the findings in the DyKAT
study,8 substrates with a strong electron-donating 4-meth-
oxyphenyl group at R3 such as 1e give lower enantiomeric
excess of the cycloadduct 3ed due to the rapid interconver-
sion of intermediate IA to its enantiomer ent-IA catalyzed
by gold(I).
(1R,4R)-6-Methyl-1-(4-nitrophenyl)-2,4,8-triphenyl-1,2,4,5-tetra-
hydrofuro[3,4-d][1,2]oxazepine (3ac)7a
Column chromatography afforded 3ac as a pale yellow oil; yield: 88.5
mg (88%); 94% ee [HPLC (Daicel IC column, hexanes–i-PrOH, 98:2, 1.0
mL/min, λ = 254 nm): tR = 11.08, 12.79 min].
1H NMR (400 MHz, CDCl3): δ = 8.14–8.05 (m, 2 H), 7.40–7.27 (m, 12
H), 7.23–7.17 (m, 2 H), 6.97–6.83 (m, 3 H), 6.16 (s, 1 H), 5.12 (dd, J =
8.0, 4.8 Hz, 1 H), 3.17–3.09 (m, 2 H), 2.37 (s, 3 H).
(1R,4R)-1-(4-Methoxyphenyl)-6-methyl-2,4,8-triphenyl-1,2,4,5-
tetrahydrofuro[3,4-d][1,2]oxazepine (3ad)7a
In summary, we have developed a gold(I)-catalyzed ki-
netic resolution of 1-(alk-1-ynyl)cyclopropyl ketones with
nitrones and 1-(alk-1-ynyl)cyclopropyl ketones were recov-
ered in high yield with excellent enantiomeric excess.
These optically active cyclopropyl ketones can be employed
in the asymmetric synthesis of various 5,7-fused bicyclic
furo[3,4-d][1,2]oxazepines in moderate to high yields with
excellent enantiomeric excess. These results indicated that
the reaction proceeds via a stereospecific SN2 process.
Column chromatography afforded 3ad as a pale yellow oil; yield: 78.0
mg (80%); 91% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH, 98:2,
0.5 mL/min, λ = 230 nm): tR = 11.27, 12.57 min].
1H NMR (400 MHz, CDCl3): δ = 7.44 7.04 (m, 14 H), 6.94–6.82 (m, 3 H),
6.82–6.73 (m, 2 H), 6.08 (s, 1 H), 5.09 (d, J = 10.8 Hz, 1 H), 3.75 (s, 3 H),
3.19 (t, J = 15.2 Hz, 1 H), 3.02 (d, J = 15.2 Hz, 1 H), 2.34 (s, 3 H).
(1R,4R)-6-Methyl-2,4,8-triphenyl-1-[(E)-styryl]-1,2,4,5-tetrahy-
drofuro[3,4-d][1,2]oxazepine (3ae)7a
Column chromatography afforded 3ae as a pale yellow oil; yield: 77.4
mg (80%); 90% ee [HPLC (Daicel AD-H column, hexanes–i-PrOH, 95:5,
0.8 mL/min, λ = 220 nm): tR = 4.89, 6.17 min].
1H NMR (400 MHz, CDCl3): δ = 7.63–7.53 (m, 2 H), 7.46–7.16 (m, 15
H), 7.04–6.98 (m, 2 H), 6.92 (t, J = 7.2 Hz, 1 H), 6.65 (dd, J = 16.4, 4.0
Hz, 1 H), 6.45 (d, J = 16.4 Hz, 1 H), 5.63 (s, 1 H), 5.08 (d, J = 10.8 Hz, 1
H), 3.16 (dd, J = 14.8, 11.6 Hz, 1 H), 2.93 (d, J = 14.8 Hz, 1 H), 2.35 (s, 3
H).
The starting materials, racemic 1a–l, were prepared according litera-
ture procedures.2,7a Enantioenriched 1-(alk-1-ynyl)cyclopropyl ke-
tones 1 were obtained by kinetic resolution.8 Compounds 2a–f were
synthesized according to a literature procedure.17
Furo[3,4-d][1,2]oxazepines 3aa–3lb;7a General Procedure
A solution of Ph3PAuOTf (1.0 mL, 0.004 M in CH2Cl2, 2.0 mol%) was
added to a solution of optical active ketone 1 (0.2 mmol) and nitrone
2a (0.24 mmol) in CH2Cl2 (1.0 mL). The resulting mixture was stirred
for 10–30 min at r.t. (TLC monitoring). When the reaction was com-
plete, the mixture was filtered and concentrated under reduced pres-
sure, and the residue was purified by flash column chromatography
(silica gel, hexanes–Et2O, 50:1).
(1R,4R)-2-Benzyl-6-methyl-1,4,8-triphenyl-1,2,4,5-tetrahydrofu-
ro[3,4-d][1,2]oxazepine (3af)7a
Column chromatography afforded 3af as a pale yellow oil; yield: 73.6
mg (78%); 94% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH, 98:2,
0.8 mL/min, λ = 230 nm): tR = 7.99, 8.90 min].
1H NMR (400 MHz, CDCl3): δ = 7.50–7.13 (m, 18 H), 7.00–6.75 (m, 2
H), 5.26 (s, 1 H), 4.79 (d, J = 10.4 Hz, 1 H), 3.93 (d, J = 12.8 Hz, 1 H),
3.71 (d, J = 12.8 Hz, 1 H), 3.27 (dd, J = 14.0, 12.0 Hz, 1 H), 3.07 (d, J =
14.8 Hz, 1 H), 2.32 (s, 3 H).
(1R,4R)-6-Methyl-1,2,4,8-tetraphenyl-1,2,4,5-tetrahydrofuro[3,4-
d][1,2]oxazepine (3aa)7a
Column chromatography afforded 3aa as a pale yellow oil; yield: 76.8
mg (84%); 91% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH,
90:10, 0.5 mL/min, λ = 230 nm): tR = 8.40, 9.35 min].
(1R, 4R)-6-Methyl-8-(1-naphthyl)-1,2,4-triphenyl-1,2,4,5-tetrahy-
drofuro[3,4-d][1,2]oxazepine (3ba)7a
Column chromatography afforded 3ba as a pale yellow oil; yield: 86.3
mg (85%); 94% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH, 98:2,
0.5 mL/min, λ = 220 nm): tR = 11.78, 14.16 min].
1H NMR (400 MHz, CDCl3): δ = 7.42–7.13 (m, 17 H), 6.92–6.80 (m, 3
H), 6.14 (s, 1 H), 5.09 (d, J = 10.8 Hz, 1 H), 3.19 (t, J = 14.8 Hz, 1 H), 3.02
(d, J = 15.2 Hz, 1 H), 2.36 (s, 3 H).
1H NMR (400 MHz, CDCl3): δ = 8.21–8.04 (m, 1 H), 7.88 (m, 2 H), 7.59–
7.49 (m, 2 H), 7.41–7.29 (m, 6 H), 7.25–7.10 (m, 6 H), 7.10–7.00 (m, 2
H), 6.85–6.71 (m, 3 H), 5.91 (s, 1 H), 5.21 (d, J = 10.4 Hz, 1 H), 3.26 (dd,
J = 13.2, 10.8 Hz, 1 H), 3.09 (d, J = 15.2 Hz, 1 H), 2.41 (s, 3 H).
(1R,4R)-1-(2-Furyl)-6-methyl-2,4,8-triphenyl-1,2,4,5-tetrahydro-
furo[3,4-d][1,2]oxazepine (3ab)7a
Column chromatography afforded 3ab as a pale yellow oil; yield: 77.8
mg (87%); 88% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH, 98:2,
0.5 mL/min, λ = 220 nm): tR = 11.38, 13.14 min].
1H NMR (400 MHz, CDCl3): δ = 7.55–7.12 (m, 13 H), 7.02–6.84 (m, 3
H), 6.30 (s, 1 H), 6.10 (d, J = 2.4 Hz, 1 H), 6.06 (s, 1 H), 5.11 (d, J = 10.4
Hz, 1 H), 3.25 (dd, J = 14.8, 11.2 Hz, 1 H), 3.01 (d, J = 14.8 Hz, 1 H), 2.33
(s, 3 H).
(1R,4R)-6-Methyl-1,2,4-triphenyl-8-(4-tolyl)-1,2,4,5-tetrahydrofu-
ro[3,4-d][1,2]oxazepine (3ca)
Column chromatography afforded 3ca as a pale yellow solid; yield:
90.5 mg (96%); 85% ee [HPLC (Daicel OD-3 column, hexanes–i-PrOH,
95:5, 0.6 mL/min, λ = 220 nm): tR = 7.73, 8.33 min]; mp 83–85 °C.
1H NMR (400 MHz, CDCl3): δ = 7.32–7.11 (m, 10 H), 7.11–6.95 (m, 6
H), 6.82–6.66 (m, 3 H), 6.04 (s, 1 H), 4.99 (d, J = 10.4 Hz, 1 H), 3.09 (dd,
J = 14.0, 12.0 Hz, 1 H), 2.90 (d, J = 15.6 Hz, 1 H), 2.23 (s, 6 H).
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13C NMR (100 MHz, CDCl3): δ = 149.63, 147.52, 147.19, 141.02,
137.91, 129.30, 129.04, 128.77, 128.34, 128.15, 127.86, 127.76,
127.30, 126.31, 125.89, 121.44, 121.02, 118.59, 116.05, 85.65, 66.80,
34.91, 21.21, 11.82.
MS (EI): m/z (%) = 471 [M]+ (6.35), 363 (100).
HRMS: m/z [M]+ calcd for C33H29NO2: 471.2198; found: 471.2202.
(1R,4R)-4-(4-Chlorophenyl)-1-(2-furyl)-6-methyl-2,8-diphenyl-
1,2,4,5-tetrahydrofuro[3,4-d][1,2]oxazepine (3gb)
Column chromatography afforded 3gb as a pale yellow solid; yield:
79.0 mg (82%); 92% ee [HPLC (Daicel AD-H column, hexanes–i-PrOH,
98:2, 0.8 mL/min, λ = 220 nm): tR = 10.81, 12.80 min]; mp 168–
171 °C.
1H NMR (400 MHz, CDCl3): δ = 7.48–7.14 (m, 12 H), 6.98–6.87 (m, 3
H), 6.27 (s, 1 H), 6.11–6.01 (m, 2 H), 5.09 (d, J = 10.0 Hz, 1 H), 3.18 (dd,
J = 15.2, 10.0 Hz, 1 H), 2.99 (d, J = 15.2 Hz, 1 H), 2.32 (s, 3 H).
(1R, 4R)-8-(4-Bromophenyl)-1-(2-furyl)-6-methyl-2,4-diphenyl-
1,2,4,5-tetrahydrofuro[3,4-d][1,2]oxazepine (3db)
13C NMR (100 MHz, CDCl3): δ = 151.89, 149.88, 147.49, 147.44,
142.21, 139.44, 133.53, 130.69, 128.66, 128.54, 127.73, 127.39,
126.06, 121.90, 120.42, 118.33, 116.48, 109.99, 109.44, 85.47, 62.16,
34.42, 11.76.
MS (EI): m/z (%) = 481 [M]+ (1.17), 77 (100).
HRMS: m/z [M]+ calcd for C30H24NO3Cl: 481.1445; found: 481.1443.
Column chromatography afforded 3db as a pale yellow solid; yield:
89.5 mg (85%); 92% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH,
95:5, 0.8 mL/ min, λ = 220 nm): tR = 5.51, 6.03 min]; mp 178–181 °C.
1H NMR (400 MHz, CDCl3): δ = 7.54–7.08 (m, 12 H), 6.99–6.84 (m, 3
H), 6.27 (s, 1 H), 6.13–5.93 (m, 2 H), 5.11 (d, J = 10.0 Hz, 1 H), 3.22 (dd,
J = 15.2, 10.0 Hz, 1 H), 3.03 (d, J = 15.2 Hz, 1 H), 2.31 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 151.68, 149.88, 147.86, 146.27,
142.22, 140.90, 131.80, 129.68, 128.67, 128.38, 127.84, 127.47,
126.34, 121.91, 121.30, 118.85, 116.56, 110.05, 109.50, 86.12, 62.17,
34.35, 11.75.
MS (EI): m/z (%) = 525 [M]+ (1.88), 43 (100).
HRMS: m/z [M]+ calcd for C30H24NO3Br: 525.0940; found: 529.0939.
(1R,4R)-4-(2-Bromophenyl)-1-(4-methoxyphenyl)-6-methyl-2,8-
diphenyl-1,2,4,5-tetrahydrofuro[3,4-d][1,2]oxazepine (3hd)
Column chromatography afforded 3hd as a pale yellow solid; yield:
96.3 mg (85%); 98% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH,
98:2, 0.8 mL/min, λ = 220 nm): tR = 6.52, 7.16 min]; mp 90–93 °C.
1H NMR (400 MHz, CDCl3): δ = 7.55–7.23 (m, 8 H), 7.20–7.04 (m, 5 H),
6.92–6.83 (m, 3 H), 6.83–6.72 (m, 2 H), 6.06 (s, 1 H), 5.38 (d, J = 10.4
Hz, 1 H), 3.79 (s, 3 H), 3.20 (d, J = 15.2 Hz, 1 H), 2.94 (dd, J = 15.2, 10.4
Hz, 1 H), 2.38 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 158.78, 149.74, 147.77, 147.16,
141.00, 132.48, 130.94, 130.25, 129.90, 128.85, 128.73, 128.58,
127.69, 127.17, 125.98, 122.40, 121.37, 121.28, 118.39, 116.44,
113.22, 84.57, 67.10, 55.11, 34.34, 11.82.
(1R, 4R)-1,4-Bis(4-Methoxyphenyl)-6-methyl-2,8-diphenyl-1,2,4,5-
tetrahydrofuro[3,4-d][1,2]oxazepine (3ed)
Column chromatography afforded 3ed as a pale yellow solid; yield:
98.3 mg (95%); 26% ee [HPLC (Daicel AD-H column, hexanes–i-PrOH,
98:2, 0.4 mL/min, λ = 220 nm): tR = 22.39, 25.57 min]; mp 70–73 °C.
1H NMR (400 MHz, CDCl3): δ = 7.42–7.22 (m, 7 H), 7.20–7.04 (m, 4 H),
6.90–6.74 (m, 7 H), 6.08 (s, 1 H), 5.04 (d, J = 11.2 Hz, 1 H), 3.79 (s, 3 H),
3.77 (s, 3 H), 3.20 (dd, J = 14.8, 11.2 Hz, 1 H), 3.05 (d, J = 14.8 Hz, 1 H),
2.35 (s, 3 H).
MS (EI): m/z (%) = 565 [M]+ (1.77), 43 (100).
HRMS: m/z [M]+ calcd for C33H28NO3Br: 565.1253; found: 565.1254.
13C NMR (100 MHz, CDCl3): δ = 159.27, 158.80, 149.83, 147.64,
147.17, 133.33, 131.05, 130.24, 130.12, 128.85, 128.67, 127.85,
127.22, 126.00, 122.52, 121.08, 118.79, 116.24, 113.79, 113.32, 85.31,
66.47, 55.34, 55.18, 34.68, 29.78, 11.96.
MS (EI): m/z (%) = 517 [M]+ (1.27), 409 (100).
HRMS: m/z [M]+ calcd for C34H31NO4: 517.2253; found: 517.2255.
(1R, 4R)-4-(4-Bromophenyl)-1-(2-furyl)-6-methyl-2,8-diphenyl-
1,2,4,5-tetrahydrofuro[3,4-d][1,2]oxazepine (3ib)
Column chromatography afforded 3ib as a pale yellow solid; yield:
79.1 mg (75%); 97% ee [HPLC (Daicel AD-H column, hexanes–i-PrOH,
98:2, 0.5 mL/min, λ = 230 nm): tR = 11.26, 12.79 min]; mp 173–
176 °C.
1H NMR (400 MHz, CDCl3): δ = 7.55–7.41 (m, 4 H), 7.41–7.31 (m, 3 H),
7.31–7.15 (m, 5 H), 7.03–6.83 (m, 3 H), 6.28 (s, 1 H), 6.06 (d, J = 11.8
Hz, 2 H), 5.07 (d, J = 10.0 Hz, 1 H), 3.18 (dd, J = 14.4, 10.8 Hz, 1 H), 2.99
(d, J = 14.8 Hz, 1 H), 2.32 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 151.92, 149.90, 147.47, 142.20,
140.00, 131.51, 130.73, 128.67, 128.07, 127.39, 126.09, 121.93,
121.70, 120.46, 118.33, 116.52, 110.00, 109.45, 85.51, 62.20, 34.41,
11.75.
(1R, 4R)-1-(2-Furyl)-6-methyl-2, 8-diphenyl-4-(4-tolyl)-1,2,4,5-tet-
rahydrofuro[3,4-d][1,2]oxazepine (3fb)
Column chromatography afforded 3fb as a pale yellow solid; yield:
81.2 mg (88%); 98% ee [HPLC (Daicel AD-H column, hexanes–i-PrOH,
98:2, 0.8 mL/ min, λ = 220 nm): tR = 5.69, 6.02 min]; mp 196–199 °C.
1H NMR (400 MHz, CDCl3): δ = 7.52–7.08 (m, 12 H), 6.98–6.84 (m, 3
H), 6.28 (s, 1 H), 6.13–6.02 (m, 2 H), 5.08 (d, J = 10.4 Hz, 1 H), 3.25 (dd,
J = 15.2, 10.4 Hz, 1 H), 2.98 (d, J = 15.2 Hz, 1 H), 2.35 (s, 3 H), 2.32 (s, 3
H).
13C NMR (100 MHz, CDCl3): δ = 152.07, 149.99, 147.42, 147.36,
142.15, 138.03, 137.51, 130.78, 129.03, 128.65, 128.61, 127.33,
126.35, 126.08, 121.62, 120.62, 118.74, 116.40, 109.97, 109.39, 86.10,
61.86, 34.39, 21.16, 11.75.
MS (EI): m/z (%) = 527 [M]+ (1.38), 77 (100).
HRMS: m/z [M]+ calcd for C30H24NO3Br: 527.0919; found: 527.0917.
(1R,4R)-1-(4-Methoxyphenyl) -2,4,6,8-tetraphenyl-1,2,4,5-tetrahy-
drofuro[3,4-d][1,2]oxazepine (3jd)
MS (EI): m/z (%) = 461 [M]+ (1.65), 77 (100).
HRMS: m/z [M]+ calcd for C31H27NO3: 461.1991; found: 461.1992.
Column chromatography afforded 3jd as a pale yellow solid; yield:
85.8 mg (78%); 99% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH,
98:2, 0.5 mL/min, λ = 220 nm): tR = 11.74, 13.64 min]; mp 87–90 °C.
1H NMR (400 MHz, CDCl3): δ = 7.66–7.28 (m, 15 H), 7.21–7.10 (m, 4
H), 6.19 (s, 1 H), 6.98–6.74 (m, 5 H), 5.16 (d, J = 9.6 Hz, 1 H), 3.79 (s, 3
H), 3.55–3.35 (m, 2 H).
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13C NMR (100 MHz, CDCl3): δ = 158.82, 149.56, 149.28, 148.53,
140.98, 131.13, 130.69, 130.23, 129.74, 128.80, 128.65, 128.58,
128.40, 127.81, 127.68, 127.59, 127.04, 126.39, 126.33, 123.68,
121.24, 120.26, 116.27, 113.30, 85.69, 66.59, 55.11, 35.51, 29.68.
MS (EI): m/z (%) = 549 [M]+ (3.05), 105 (100).
HRMS: m/z [M]+ calcd for C38H31NO3: 549.2304; found: 549.2302.
(4) Zhang, Y.; Chen, Z.; Xiao, Y.; Zhang, J. Chem. Eur. J. 2009, 15,
5208.
(5) Liu, F.; Yu, Y.; Zhang, J. Angew. Chem. Int. Ed. 2009, 48, 5505.
(6) (a) Gao, H.; Zhang, J. Adv. Synth. Catal. 2009, 351, 85. (b) Xiao, Y.;
Zhang, J. Chem. Commun. 2009, 3594. (c) Liu, L.; Zhang, J. Angew.
Chem. Int. Ed. 2009, 48, 6093. (d) Zhou, G.; Zhang, J. Chem.
Commun. 2010, 46, 6593. (e) Chen, Z.; Tian, Z.; Zhang, J.-M.;
Zhang, J. Chem. Eur. J. 2012, 18, 8591. (f) Zeng, Q.; Zhang, L.;
Yang, J.; Xu, B.; Xiao, Y.; Zhang, J. Chem. Commun. 2014, 50,
4203.
(1R,4R)-4-(4-Chlorophenyl)-1-(4-methoxyphenyl)- 2,6,8-triphen-
yl-1,2,4,5-tetrahydrofuro[3,4-d][1,2]oxazepine (3kd)
Column chromatography afforded 3kd as a pale yellow solid; yield:
78.3 mg (67%); 92% ee [HPLC (Daicel OD-H column, hexanes–i-PrOH,
95:5, 0.8 mL/min, λ = 220 nm): tR = 6.87, 7.70 min]; mp 111–114 °C.
1H NMR (400 MHz, CDCl3): δ = 7.66–7.09 (m, 18 H), 6.93–6.75 (m, 5
H), 6.18 (s, 1 H), 5.12 (d, J = 9.6 Hz, 1 H), 3.76 (s, 3 H), 3.50–3.30 (m, 2
H).
13C NMR (100 MHz, CDCl3): δ = 158.91, 149.52, 149.34, 148.59,
139.46, 133.58, 131.08, 130.65, 130.21, 129.60, 128.84, 128.62,
128.58, 127.69, 127.03, 126.40, 123.60, 121.44, 119.95, 116.32,
113.35, 85.04, 66.80, 55.09, 35.52.
MS (EI): m/z (%) = 583 [M]+ (1.07), 77 (100).
HRMS: m/z [M]+ calcd for C38H30NO3Cl: 583.1914; found: 583.1913.
(7) (a) Zhang, Y.; Liu, F.; Zhang, J. Chem. Eur. J. 2010, 16, 6146.
(b) Bai, Y.; Fang, J.; Ren, J.; Wang, Z. Chem. Eur. J. 2009, 15, 8975.
(8) Part of this work has been published in a preliminary communi-
cation, see: Zhang, Y.; Zhang, J. Chem. Commun. 2012, 48, 4710.
(9) For Lewis acid catalyzed (dynamic) kinetic resolutions of cyclo-
propane diesters, see: (a) Sibi, M. P.; Ma, Z.; Jasperse, C. P. J. Am.
Chem. Soc. 2005, 127, 5764. (b) Kang, Y.-B.; Sun, X.-L.; Tang, Y.
Angew. Chem. Int. Ed. 2007, 46, 3918. (c) Parsonsand, A. T.;
Johnson, J. S. J. Am. Chem. Soc. 2009, 131, 3122. (d) Parsons, A. T.;
Smith, A. G.; Neel, A. J.; Johnson, J. S. J. Am. Chem. Soc. 2010, 132,
9688. (e) Campbell, M. J.; Johnson, J. S.; Parsons, A. T.; Pohlhaus,
P. D.; Sanders, S. D. J. Org. Chem. 2010, 75, 6317. Note, however,
that these reported catalytic systems are not applied to the
present 1-(alk-1-ynyl)cyclopropyl ketones.
(10) (a) Johansson, M. J.; Gorin, D. J.; Staben, S. T.; Toste, F. D. J. Am.
Chem. Soc. 2005, 127, 18002. (b) Watson, I. D. G.; Ritter, S.; Toste,
F. D. J. Am. Chem. Soc. 2009, 131, 2056. (c) Cao, Z.-Y.; Wang, X.;
Tan, C.; Zhao, X.-L.; Zhou, J.; Ding, K. J. Am. Chem. Soc. 2013, 135,
8197. (d) Briones, J. F.; Davies, H. M. L. J. Am. Chem. Soc. 2012,
134, 11916.
(1R,4R)-6-(4-Chlorophenyl)-1-(2-furyl)-2,4,8-triphenyl-1,2,4,5-
tetrahydrofuro[3,4-d][1,2]oxazepine (3lb)
Column chromatography afforded 3lb as a pale yellow solid; yield:
87.0 mg (80%); 87% ee [HPLC (Daicel AD-H column, hexanes–i-PrOH,
95:5, 0.8 mL/min, λ = 220 nm): tR = 9.68, 14.34 min]; mp 101–104 °C.
1H NMR (400 MHz, CDCl3): δ = 7.65–7.12 (m, 17 H), 7.03–6.85 (m, 3
H), 6.28 (s, 1 H), 6.17 (d, J = 12.2 Hz, 2 H), 5.19 (d, J = 7.4 Hz, 1 H),
3.60–3.18 (m, 2 H).
13C NMR (100 MHz, CDCl3): δ = 151.71, 149.72, 149.06, 148.09,
142.22, 140.81, 133.42, 130.37, 129.46, 128.79, 128.72, 128.68,
128.44, 128.11, 127.99, 127.91, 126.53, 126.27, 121.94, 120.69,
116.52, 110.08, 109.55, 86.00, 62.05, 34.99.
(11) For selected reviews on gold-catalyzed reactions published
since 2011, see: (a) Bandini, M. Chem. Soc. Rev. 2011, 40, 1358.
(b) Krause, N.; Winter, C. Chem. Rev. 2011, 111, 1994. (c) Haro, T.
D.; Nevado, C. Synthesis 2011, 2530. (d) Wegner, H. A.; Auias, M.
Angew. Chem. Int. Ed. 2011, 50, 8236. (e) Boorman, T. C.; Larrosa,
I. Chem. Soc. Rev. 2011, 40, 1910. (f) Rudolph, M.; Hashmi, A. S.
K. Chem. Commun. 2011, 47, 6536. (g) Gaillard, S.; Cazin, C. S. J.;
Nolan, S. P. Acc. Chem. Res. 2012, 45, 778. (h) Rudolph, M.;
Hashmi, A. S. K. Chem. Soc. Rev. 2012, 41, 2448. (i) Zhang, D.;
Zhang, Z.; Shi, M. Chem. Commun. 2012, 48, 10271. (j) Haibach,
M. C.; Seidel, D. Angew. Chem. Int. Ed. 2014, 53, 5010. (k) Zhang,
L. Acc. Chem. Res. 2014, 47, 877. (l) Xie, J.; Pan, C.; Abdukade, A.;
Zhu, C. J. Chem. Soc. Rev. 2014, 43, 5245. (m) Obradors, C.;
Echavarren, A. M. Chem. Commun. 2014, 50, 16. (n) Hashmi, A. S.
K. Acc. Chem. Res. 2014, 47, 864. (o) Obradors, C.; Echavarren, A.
M. Acc. Chem. Res. 2014, 47, 902. (p) Zhang, D.; Tang, X.; Shi, M.
Acc. Chem. Res. 2014, 47, 913. (q) Fürstner, A. Acc. Chem. Res.
2014, 47, 925. (r) Alcaide, B.; Almendros, P. Acc. Chem. Res.
2014, 47, 939. (s) Fensterbank, L.; Malacria, M. Acc. Chem. Res.
2014, 47, 953. (t) Yeom, H.-S.; Shin, S. Acc. Chem. Res. 2014, 47,
966. (u) Qian, D.; Zhang, J. Chem. Rec. 2014, 14, 280. (v) Jia, M.;
Bandini, M. ACS Catal. 2015, 5, 1638. (w) Qian, D.; Zhang, J.
Chem. Soc. Rev. 2015, 44, 677. (x) Ranieri, B.; Escofet, I.;
Echavarren, A. M. Org. Biomol. Chem. 2015, 13, 7130. (y) Dorel,
R.; Echavarren, A. M. Chem. Rev. 2015, 115, 9028.
MS (EI): m/z (%) = 543 [M]+ (0.12), 77 (100).
HRMS: m/z [M]+ calcd for C35H26NO3Cl: 543.1601; found: 543.1609.
Acknowledgment
We are grateful to 973 Programs (2015CB856600), the National Natu-
ral Science Foundation of China (21372084, 21425205), and Changji-
ang Scholars and Innovative Research Team in University (PCSIRT) for
financial supports.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0035-1561276.
S
u
p
p
ortioInfgrmoaitn
S
u
p
p
ortiInfogrmoaitn
(12) For recent general reviews on non-enzymatic kinetic resolution,
see: (a) Pellissier, H. Adv. Synth. Catal. 2011, 353, 1613.
(b) Vedejs, E.; Jure, M. Angew. Chem. Int. Ed. 2005, 44, 3974.
(13) For selected reviews on enantioselective gold(I) catalysis, see:
(a) Widenhoefer, R. A. Chem. Eur. J. 2008, 14, 5382. (b) Bongers,
N.; Krause, N. Angew. Chem. Int. Ed. 2008, 47, 2178.
(c) Senguptaand, S.; Shi, X. ChemCatChem 2010, 2, 609.
(d) Pradal, A.; Toullec, P. Y.; Michelet, V. Synthesis 2011, 1501.
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, 512–519