Diels-Alder dimerization of Morita-Baylis-Hillman acetates catalyzed by organocatalysts

Article abstract of DOI:10.1007/s11164-012-0626-6

DABCO-catalyzed dimerization of Morita-Baylis-Hillman acetates to synthesize a series of 3-alkyl-4-(E)-alkenyl-cyclohex-1-ene-1,4-dicarbonyl compounds in excellent yields with modest to excellent diastereoselectivity is reported. A plausible reaction mechanism is also proposed on the basis of previous literature and preliminary investigation the asymmetric version of the reaction.

Full text of DOI:10.1007/s11164-012-0626-6

Res Chem Intermed (2013) 39:5–18
DOI 10.1007/s11164-012-0626-6
Diels–Alder dimerization of Morita–Baylis–Hillman
acetates catalyzed by organocatalysts
Hong-Ping Deng
•
Yin Wei Min Shi
•
Received: 16 August 2011 / Accepted: 30 August 2011 / Published online: 22 June 2012
Ó Springer Science+Business Media B.V. 2012
Abstract DABCO-catalyzed dimerization of Morita–Baylis–Hillman acetates to
synthesize a series of 3-alkyl-4-(E)-alkenyl-cyclohex-1-ene-1,4-dicarbonyl com-
pounds in excellent yields with modest to excellent diastereoselectivity is reported.
A plausible reaction mechanism is also proposed on the basis of previous literature
and preliminary investigation the asymmetric version of the reaction.
Keywords Diels–Alder dimerization ꢀ MBH acetates ꢀ Organocatalysis
Introduction
Morita–Baylis–Hillman (MBH) acetates and carbonates are valuable building blocks
in organic synthesis, because of their diverse reactivity in a variety of chemical
transformations [1–13]. Recently, significant effort has been directed toward two
aspects of the transformation of MBH acetates and MBH carbonates: substitution of
MBH acetates or MBH carbonates and cycloaddition with electron-deficient olefins
in the presence of organocatalysts. Catalyzed by Lewis base, MBH acetates or MBH
carbonates could be transformed to intermediate I which could be easily substituted
at the b or b’-position by nucleophiles (Scheme 1, Eqs. 1 and 2). As can be seen from
Scheme 1, when nucleophiles attacked the b’-position, the corresponding product
was obtained with no chiral center. Kim and co-workers have used this method to
synthesize a variety of trisubstituted alkenes and heterocyclic and carbocyclic
molecules of biological importance in good yields with defined stereochemistry
Electronic supplementary material Theonlineversionofthisarticle(doi:10.1007/s11164-012-0626-6)
contains supplementary material, which is available to authorized users.
H.-P. Deng ꢀ Y. Wei ꢀ M. Shi (&)
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
e-mail: mshi@mail.sioc.ac.cn
123

6
H.-P. Deng et al.
[
14–20]. When nucleophiles attacked at the b-position, the chiral center was retained
and the development of the asymmetric substitution was feasible. In this respect,
Chen [21–28] and Wang [29, 30] have reported use of cinchona alkaloids and their
derivatives as catalysts in asymmetric substitution of MBH carbonates, affording the
corresponding adducts in excellent yields and with excellent enantioselectivity.
Krische [31] and our group [32–35] have also developed a series of chiral phosphine
0
0
catalysts which could succeed in S 2 –S 2 asymmetric substitution of MBH
N
N
acetates and MBH carbonates with a variety of nucleophiles in good yields with high
enantioselectivity. Moreover, MBH acetates and MBH carbonates have also attracted
scientists’ attention as a source of in-situ-generated phosphorus ylides upon
treatment with tertiary phosphines (Scheme 1, Eq. 3). For example, Lu and others
have succeeded in using MBH acetates and MBH carbonates as 1,3-dipoles in a
series of intra and intermolecular phosphine-catalyzed [3 ? n] annulations (n = 2,
4
, 6) to give the corresponding cycloadducts in high yields and with good
regioselectivity [36–43]. In 2010, Tang and his co-workers used spirobiindane-based
chiral phosphines as catalysts to provide the corresponding intramolecular [3 ? 2]
annulation products in good yields and with good enantioselectivity [44]. More
recently, Zhang [45], Huang [46], and He [47] and their co-workers have also
developed several [4 ? 1] annulations of MBH acetates and carbonates to give the
cycloaddition products in high yields. Besides the two methods mentioned above,
Hoffmann [48] discovered that MBH alcohols derived form aliphatic aldehydes
could be transformed to dienes, then dimerized spontaneously by treatment with
MsCl, DABCO, and DMAP under mild conditions (Scheme 1, Eq. 4). They also
found that MBH alcohols derived from acrylates [49] produced the corresponding
3
-alkyl-4-(E)-alkenyl-cyclohex-1-ene-1,4-dicarbonyl compounds in good yields
with high diastereoselectivity, and MBH alcohols derived from phenyl vinyl sulfone
50] only gave the trans isomers diastereoselectively in modest to good yields under
[
the standard conditions. In 2002, Kim [51] and his co-workers isolated the similar
Diels–Alder dimerized compound as side-product during their investigation of the
allylic amination of the MBH acetates promoted by DABCO in H O–THF.
2
Recently, we have been devoting much effort to asymmetric MBH and aza-MBH
reactions [52] and asymmetric substitution of MBH acetates and MBH carbonates
[
32–35] catalyzed by chiral bifunctional phosphines. As a part of our continuing
interest in asymmetric allylic amination of MBH acetates with phthalimide
catalyzed by chiral bifunctional phosphines, we have tried asymmetric allylic
amination of MBH acetate 1a, derived from phenylpropyl aldehyde, with
phthalimide, catalyzed by chiral thiourea–phosphine (TP5), which has been
previously reported as the best catalyst for asymmetric allylic amination of MBH
acetates derived from aromatic aldehydes [32]. Instead of asymmetric allylic
amination of the MBH acetates, we found that different reaction occurred and the
same product, 2a, as reported by Hoffmann [48] was obtained in[99 % yield with
3
:1 dr (Scheme 2). We discovered this was a Diels–Alder dimerization of MBH
acetates catalyzed by commonly used nitrogen-containing or phosphorus-containing
organocatalysts. Herein, we report our findings from study of this reaction, which
can be used for efficient construction of 3-alkyl-4-(E)-alkenyl-cyclohex-1-ene-1,
4
-dicarbonyl compounds under mild conditions.
1
23

Dimerization of MBH acetates catalyzed by organocatalysts
7
O
Nu substitutes
from β' position
O
R
R
R'
β
eq 1
R
R'
LB
Nu
O
Lewis Base
β'
Nu
LG
O
I
*
eq 2
eq 3
Nu substitutes
R'
R
R'
from
β
position
R=alkyl or aryl group
R'=alkyl or alkoxyl group
LG=OA cor OBoc
R1
EWG
EWG
O
O
R'
R
Phosphine
R
R'
P
R1
GWE
EWG
O
II
MsCl (120 mol-%),
DABCO (300 mol-%),
DMAP (10 mol-%)
R
OH
O
O
Dimerization
R
R
O
eq 4
DCM,0 °C-r.t.
R
Scheme 1 Transformation of MBH acetates and carbonates or MBH alcohols
S
N
H
N
H
PPh2
MeO
O
O
O
OAc O
(
TP5, 25 mol-%)
N
R1
O
+
NH
1
,2-dichlorobenzene, 4 Å MS
R1
o
1
0 C
O
(
1.0 equiv.)
(
2.0 equiv.)
77- >99% yield
80-90% ee
R1 = aromatic group
Ph
O
NH
O
OAc O
(
TP5, 25 mol-%)
1,2-dichlorobenzene, 4 Å MS
0 °C
Ph
+
Ph
1
O
1
a (1.0 equiv.)
(
2.0 equiv.)
O
a, >99% yield, 3:1 dr
2
Scheme 2 Asymmetric substitution of MBH acetates catalyzed by bifunctional thiourea–phosphine
Results and discussion
Initially, we tested the solvent effects in the reaction of MBH acetate 1a catalyzed
by 20 mol % DABCO at room temperature; the results are summarized in Table 1.
It was found that the solvent effects in this reaction were not obvious. THF is the
123

8
H.-P. Deng et al.
Table 1 Examination of solvent effects
Ph
Ph
Ph
O
O
OAc O
DABCO (20 mol-%)
solvent, r.t.
Ph
Ph
+
O
O
1
a
trans-2a
cis-2a
a
b
Entry
Solvent
Yield (%)
dr (trans: cis)
1
2
3
4
5
THF
[99
99
3:1
DCM
2.5:1
3:1
CH
3
CN
94
Toluene
DMF
99
3:1
97
3:1
Reactions were performed with 1a (0.2 mmol) in solvent (1.0 mL) for 24 h
a
Isolated yield of 2a
b
1
Determined by H NMR spectroscopy
best solvent for this reaction, affording product 2a in more than 99 % total yield as a
diastereoisomeric mixture of trans-2a and cis-2a in 3:1 ratio (Table 1, entry 1, the
relative configuration of product 2a was determined by two-dimensional NMR
spectroscopy, on the basis of Hoffmann’s work). Other tested solvents, for example
dichloromethane (DCM), CH CN, toluene, and N,N-dimethylformamide (DMF) did
3
not substantially affect total yield or diastereoselectivity (Table 1, entries 2–5). Use
of DCM resulted in slight reduction of the diastereoselectivity of 2a (Table 1, entry
2
) and use of CH CN resulted in slight reduction of the total yield of 2a (Table 1,
3
entry 3).
Next, we examined the effects of temperature and different catalysts and catalyst
loading on this reaction; the results are summarized in Table 2. It was found that
reducing the temperature to 0 or -20 °C still afforded 2a in excellent total yield
with good diastereoselectivity (4:1 dr) (Table 2, entries 2 and 3). Further reducing
the temperature to -40 °C did not change the diastereoselectivity (4:1 dr), but
reduced the total yield of 2a to 70 % (Table 2, entry 4). We then conducted the
reaction in THF at 0 °C and reduced the amount of catalyst (DABCO) used to 10 or
5
mol%; the results obtained were the same as for use of 20 mol% catalyst (Table 2,
entries 2, 5, and 6). Instead of DABCO, we also examined other catalysts, for
example PPh , DMAP, and DBU; we found that DABCO was the best catalyst for
this reaction and DBU was much inferior (Table 2, entries 6–9).
3
Having identified the optimum reaction conditions, we next examined the
generality of this reaction with different MBH acetates 1; the results are summarized
in Table 3. When R2 was an alkyl group, all of the reactions proceeded smoothly
under the optimum conditions, producing the corresponding products 2 in excellent
yields (93–99 %), with modest diastereoselectivity (3:1–s4:1), (Table 3, entries
1
–8). Because substrates derived from ethyl acrylate were less reactive than methyl
vinyl ketone, we increased the amount of DABCO used to 20 mol%, and the
reactions also proceeded successfully with good diastereoselectivity (6:1–10:1) and
1
23

Dimerization of MBH acetates catalyzed by organocatalysts
9
Table 2 Optimization of other reaction conditions
Ph
Ph
+
O
O
OAc O
Ph
Ph
catalyst (x mol-%)
Ph
THF, T
O
O
1a
trans-2a
cis-2a
a
b
Entry
Catalyst
x
T (°C)
Yield (%)
dr (trans: cis)
1
2
DABCO
DABCO
DABCO
DABCO
DABCO
DABCO
PPh
20
20
20
20
10
5
r.t.
0
[99
[99
99
3:1
41
c
3
-20
-40
0
4:1
4:1
4:1
4:1
3:1
3:1
2:1
c
4
70
5
R
7
8
9
99
0
99
5
0
99
DMAP
DBU
5
0
97
5
0
1R
Reactions were performed with 1a (0.2 mmol) in solvent (1.0 mL) for 24 h
a
Isolated yield of 2a
b
c
1
Determined by H NMR spectroscopy
Reactions were performed for 48 h
excellent yields (85–99 %) (Table 3, entries 9–13). Unfortunately, substrates derived
from isobutylaldehyde and hexahydrobenzaldehyde did not undergo this reaction
(
Table 3, entries 14 and 15).
We further confirmed that 3-benzyl-(E)-4-alken-cyclohex-1-ene-1,4-dione 2a could
be also synthesized from MBH alcohol I directly via a one-pot approach. Compared
with the result obtained with 1a, it was found that treatment of MBH alcohol I and
Boc O (2.0 equiv.) with DMAP (20 mol%) in DCM at 0 °C to room temperature
2
afforded 2a in 70 % total yield with lower diastereoselectivity (2.5:1) (Scheme 3).
Based on the above experimental results and Hoffmann’s proposed mechanism,
[
8b, 8c]
a plausible mechanism is outlined in Scheme 4. Direct addition of nucleophilic
DABCO to the b’ position of the MBH acetate generates the electrophilic leaving
-
group AcO ; this anion deprotonates the c position of the cationic substrate to produce
the intermediate diene A. Substrates derived from isobutylaldehyde and hexahydro-
benzaldehyde did not undergo this reaction under identical conditions because of
steric hindrance of the c-proton and the substituent effects of the Diels–Alder reaction
[53]. Finally, intermediate diene A spontaneously affords the desired product 2 via
Diels–Alder dimerization. The regio and diastereoselectivity might be because the
(
[
E)-double bond of the dienophile has a secondary orbital interaction with the diene.
We also attempted to use chiral catalysts (4-(3-ethyl-4-oxa-1-azatricyclo
3
,8
4,4,0,0 ]dec-5-yl)-quinolin-6-ol (also called as b-isocupreidine) (b-ICD) and
bifunctional thiourea–phosphine TP for the asymmetric version of this reaction,
using 1e as substrate. Unfortunately, b-ICD (10 mol%) gave 2e in[99 % yield with
123

10
H.-P. Deng et al.
Table 3 Substrate scope for Diels–Alder dimerization of MBH acetates
R1
R2
R1
R2
O
O
OAc O
R1
R1
R1
DABCO (5 or 20mol-%)
THF, 0°C
R2
+
R2
trans-2a-m
O
R2
cis-2a-m
O
1
a-m
1
R
2
R
a
b
Entry
Yield (%)
dr (frans:c/s)
1
2
3
4
5
1a, PhCH
1b, Me
1c, Et
2
Me
Me
Mo
Me
Me
Et
2a, [99
2b, [99
2c, 93
2d, [99
2e, 99
2f 97
4:1
4:1
4:1
4:1
3:1
4:1
4:1
4:1
–
1d, Pr
1e, Bu
c
6
1f, PhCH
2
7
8
1g, o-MeC
6
H
4
CH
2
Me
2g, 95
2h, 96
2i, 95
2j, 99
2k, 94
2l, 95
2m, 85
–
1h, p-BrC
6
H
4
CH
2
Me
d
9
1i, H
OEt
OEt
OEt
OEt
OEt
d
10
11
12
13
14
15
1j, Me
1k, Et
10:1
6:1
7:1
7:1
–
d
d
d
1l, Pr
1m, Bu
OAc O
OAc O
–
–
Reactions were performed with 1 (0.2 mmol) in solvent (1.0 mL) for 18 h
a
Isolated yield of 2
b
c
d
1
Determined by H NMR spectroscopy
Reaction was performed for 24 h
Reactions were performed for 36 h
Ph
Ph
+
O
O
OH
O
Boc O(200mol-%),
2
DMAP(10mol-%)
Ph
Ph
Ph
DCM, 0°C~r.t.
O
O
I
trans-2a
cis-2a
yield(2a):70%,trans:cis=2.5:1
Scheme 3 One-pot Diels-Alder dimerization with the corresponding MBH alcohol
1
23

Dimerization of MBH acetates catalyzed by organocatalysts
11
O
OAc O
O
R1
β
R2
R1
1 γ
R
-HOAc
R2
R2
N
β
γ
H
1
β'
R1
β'
N
O
N
OAc
R2
N
A
R1
R2
R1
R2
O
O
R1
R1
R2
trans-2
O
R2
cis-2
O
Scheme 4 Proposed reaction mechanism
a 5:1 diastereomeric ratio, but the corresponding major product trans-2e was
obtained as a racemic product. Chiral bifunctional thiourea–phosphine TP
(
20 mol%) also produced 2e in [99 % yield with a 4:1 diastereomeric ratio; in
this case, trans-2e was formed in only 3 % ee under the standard conditions
Scheme 5).
(
OH
O
N
Bu
Bu
O
Bu
O
Bu
N
OAc O
(
β-ICD,10 mol-%)
THF, 0 oC, 36 h
Bu
+
O
O
1e, 0.2 mmol
trans-2e
cis-2e
yield: >99%, trans:cis = 5:1,
racemic(trans-2e)
CF3
S
N
H
N
H
CF3 Bu
Bu
PPh2
O
O
Bu
OAc O
Bu
(
TP, 20 mol-%)
Bu
+
toluene, r.t., 36 h
O
O
1e, 0.2 mmol
trans-2e
yield: >99%, trans:cis = 4:1,
%ee (trans-2e)
cis-2e
3
Scheme 5 Preliminary exploration of enantioselectivity
123

12
H.-P. Deng et al.
Conclusion
In summary, we have synthesized a series of 3-alkyl-4-(E)-alkenyl-cyclohex-1-ene-
,4-dicarbonyl compounds in excellent yield and with moderate to good diastere-
1
oselectivity via organocatalyzed Diels–Alder dimerization of MBH acetates. We also
attempted the asymmetric version of this reaction, although the enantioselectivity
obtained was poor. Future studies will focus on improving the enantioselectivity and
on using this method to prepare synthetically more interesting compounds.
General procedure for Diels–Alder dimerization of MBH acetates
Under an argon atmosphere, a solution of compound 1a (0.2 mmol) and DABCO
(
0.01 or 0.04 mmol) in THF (1.0 mL) was stirred at 0 °C. After compound 1a was
completely consumed, the solvent was removed under reduced pressure and the
residue was purified on a TLC plate (elution with petroleum ether–EtOAc 30:1) to
provide compounds trans-2a and cis-2a.
trans-3-Benzyl-4-((E)-3-phenylprop-1-enyl)cyclohex-1-ene-1,4-diyl)diethanone
(
trans-2a)
[8a] 1
2
8 mg, yield: 75 %, this is an known compound.
H NMR (300 MHz, CDCl3,
TMS): d 1.86–1.96 (2H, m, CH), 2.09 (3H, s, CH ), 2.11 (3H, s, CH ), 2.15–2.28
3
3
(
2H, m, CH), 2.20-2.58 (1H, m, CH), 2.98 (1H, dd, J = 4.2, 12.9 Hz, CH),
.18–3.24 (1H, m, CH), 3.45 (2H, d, J = 6.9 Hz, CH ), 5.50 (1H, d, J = 15.9 Hz,
CH), 5.84 (1H, dt, J = 6.9, 15.9 Hz, CH), 6.59 (1H, d, J = 5.1 Hz, CH), 7.14–7.32
3
2
1
3
(
10H, m, ArH); C NMR (75 MHz, CDCl , TMS): d 20.8, 24.5, 24.7, 25.0, 38.2,
3
3
9.3, 41.2, 56.6, 126.2, 128.4, 128.5, 129.0, 131.5, 132.5, 136.3, 139.5, 139.6,
43.9, 198.8, 208.6.
1
cis-3-Benzyl-4-((E)-3-phenylprop-1-enyl)cyclohex-1-ene-1,4-diyl)diethanone (cis-
2
a)
[8a] 1
1
0 mg, yield: 25 %, this is an known compound.
H NMR (300 MHz, CDCl3,
TMS): d 1.92–1.97 (2H, m, CH), 2.03–2.16 (4H, m, CH ? CH ), 2.19 (3H, s, CH ),
3
3
2
CH), 3.35 (2H, d, J = 6.9 Hz, CH ), 5.40 (1H, d, J = 15.9 Hz, CH), 5.68 (1H, dt,
.39–2.50 (2H, m, CH), 2.70 (1H, dd, J = 4.2, 13.2 Hz, CH), 2.85–2.92 (1H, m,
2
J = 6.9, 15.9 Hz, CH), 6.55 (1H, d, J = 5.1 Hz, CH), 7.05 (2H, d, J = 7.2 Hz,
3
1
ArH), 7.14–7.34 (8H, m, ArH); C NMR (75 MHz, CDCl , TMS): d 20.7, 23.8,
3
2
5.2, 26.2, 38.3, 39.1, 43.5, 55.8, 126.2, 126.6, 128.2, 128.4, 128.5, 128.9, 131.6,
32.2, 138.4, 138.8, 139.5, 140.9, 198.8, 208.8.
1
trans-3-Methyl-4-((E)-prop-1-enyl)cyclohex-1-ene-1,4-diyl)diethanone (trans-2b)
[8a] 1
2
3 mg, yield (2b): [99 %, this is an known compound.
H NMR (400 MHz,
CDCl , TMS): d 0.95 (3H, d, J = 7.2 Hz, CH ), 1.75 (3H, dd, J = 2.0, 6.4 Hz,
3
3
CH ), 1.78–1.83 (1H, m, CH), 1.90–1.99 (1H, m, CH), 2.08–2.14 (4H, m,
3
1
23

Dimerization of MBH acetates catalyzed by organocatalysts
13
CH ? CH ), 2.26 (3H, s, CH ), 2.45–2.51 (1H, m, CH), 3.01 (1H, dd, J = 6.4,
3
3
7.2 Hz, CH), 5.31 (1H, dd, J = 2.0, 16.0 Hz, CH), 5.58 (1H, dq, J = 6.4, 16.0 Hz,
CH), 6.86 (1H, dq, J = 1.2, 6.4 Hz, CH).
trans-3-Methyl-4-((E)-prop-1-enyl)cyclohex-1-ene-1,4-diyl)diethanone (trans-2c)
[8a] 1
2
3 mg, yield (2c): 93 %, this is an known compound.
H NMR (400 MHz,
CDCl , TMS): d 0.98–1.03 (6H, m, CH ? CH ), 1.06–1.15 (1H, m, CH),
3
3
3
1
.58–1.68 (1H, m, CH), 1.78–1.85 (1H, m, CH), 1.93–2.04 (1H, m, CH), 2.06–2.17
6H, m, CH ? CH ? CH ? CH ), 2.28 (3H, s, CH ), 2.45–2.51 (1H, m, CH),
(
3
3
2
.76–2.79 (1H, m, CH), 5.28 (1H, d, J = 16.4 Hz, CH), 5.62 (1H, dt, J = 6.4,
6.4 Hz, CH), 7.03 (1H, dt, J = 1.6, 5.2 Hz, CH).
1
trans-4-((E)-Pent-1-enyl)-3-propylcyclohex-1-ene-1,4-diyl)diethanone (trans-2d)
2
8 mg, yield (2d):[99 %, a colorless oil; IR (CH Cl ): m 2957, 2931, 2872, 1703,
-1 1
2
2
1
668, 1642, 1463, 1435, 1389, 1352, 1257, 1155, 979, 849, 738, 626 cm ; H
NMR (400 MHz, CDCl , TMS): d 0.87–0.95 (6H, m, CH ? CH ), 1.06–1.14 (1H,
3
3
3
m, CH), 1.34–1.44 (3H, m, CH ? CH ? CH), 1.45–1.52 (2H, m, CH ? CH),
1
.78–1.86 (1H, m, CH), 1.95–2.08 (3H, m, CH ? CH ? CH), 2.09 (3H, s, CH3),
2
m, CH), 5.29 (1H, d, J = 15.6 Hz, CH), 5.57 (1H, dt, J = 6.8, 15.6 Hz, CH), 7.01
.11–2.17 (1H, m, CH), 2.27 (3H, s, CH ), 2.44–2.51 (1H, m, CH), 2.85–2.88 (1H,
3
1
3
(
1H, dt, J = 1.6, 4.8 Hz, CH); C NMR (75 MHz, CDCl , TMS): d 13.6, 14.4,
3
2
0.96, 21.04, 22.3, 24.6, 24.7, 25.1, 34.3, 35.0, 38.8, 56.8, 130.6, 133.4, 136.4,
?
44.8, 199.0, 209.4; MS (ESI) m/z (%): 299.2 (100) [M ? Na]; HRMS (ESI)
1
Calcd. For C H NaO (M ? Na) requires 299.1982, Found: 299.1985.
?
1
?
1
8
28
2
trans-3-Butyl-4-((E)-hex-1-enyl)cyclohex-1-ene-1,4-diyl)diethanone (trans-2e)
3
1
7
1
0 mg, yield (2e): 99 %, a colorless oil; IR (CH Cl ): m 2956, 2929, 2859, 1703,
2
2
668, 1642, 1465, 1435, 1389, 1351, 1255, 1217, 1155, 1076, 979, 954, 871,
-
1 1
38 cm ; H NMR (400 MHz, CDCl , TMS): d 0.89–0.92 (6H, m, CH ? CH ),
3
3
3
.05–1.14 (1H, m, CH), 1.27–1.46 (8H, m, CH ? CH ? CH ? CH ), 1.50–1.58
2
2
2
2
(
CH ? CH ? CH ? CH ), 2.27 (3H, s, CH ), 2.44–2.50 (1H, m, CH), 2.83–2.85
1H, m, CH), 1.78–1.86 (1H, m, CH), 1.93–2.02 (1H, m, CH), 2.06–2.17 (6H, s,
3
3
(
1H, m, CH), 5.28 (1H, d, J = 16.0 Hz, CH), 5.57 (1H, dt, J = 6.8, 16.0 Hz, CH),
1
3
7
2
1
.01 (1H, dt, J = 1.6, 5.6 Hz, CH); C NMR (75 MHz, CDCl , TMS): d 13.8, 13.9,
3
1.0, 22.1, 22.9, 24.6, 24.7, 25.1, 30.1, 31.3, 31.7, 32.6, 39.0, 56.8, 130.4, 133.5,
?
36.4, 144.8, 199.0, 209.4; MS (ESI) m/z (%): 327.3 (100) [M ? Na]; HRMS
?
1
?
(
Enantiomeric excess was determined by HPLC with a Chiralcel AD-H column
ESI) Calcd. For C H NaO (M ? Na) requires 327.2294, Found: 327.2300;
20 32 2
(
k = 230 nm; eluent: hexane/isopropanol = 95/5; Flow rate: 0.7 mL/min).
123

14
H.-P. Deng et al.
trans-3-Benzyl-4-((E)-3-phenylprop-1-enyl)cyclohex-1-ene-1,4-diyl)dipropan-1-one
trans-2f)
(
3
2
1
9 mg, yield (2f): 97 %, a pale yellow oil; IR (CH Cl ): m 3061, 3027, 2936, 2873,
2
2
855, 1743, 1706, 1669, 1602, 1495, 1454, 1377, 1341, 1269, 1215, 1202, 1076,
-
1 1
029, 977, 799, 738, 710 cm ; H NMR (300 MHz, CDCl , TMS): d 0.95–1.00
3
(
(
6H, m, CH ? CH ), 1.91–2.02 (2H, m, CH ), 2.16–2.28 (2H, m, CH ), 2.39–2.60
3 3 2 2
5H, m, CH ? CH ? CH), 2.97 (1H, dd, J = 3.9, 12.9 Hz, CH), 3.20–3.26 (1H,
2
2
m, CH), 3.45 (2H, d, J = 6.9 Hz, CH ), 5.50 (1H, d, J = 15.9 Hz, CH), 5.82 (1H,
2
dt, J = 6.9, 15.9 Hz, CH), 6.61 (1H, d, J = 4.8 Hz, CH), 7.14–7.19 (4H, m, ArH),
1
3
7
2
1
.21–7.33 (6H, m, ArH); C NMR (75 MHz, CDCl , TMS): d 8.41, 8.44, 21.1,
3
4.7, 29.9, 29.9, 38.3, 39.4, 41.4, 56.5, 126.3, 128.4, 128.4, 128.5, 128.5, 129.1,
31.8, 132.3, 135.7, 139.6, 139.8, 142.3, 201.5, 211.5; MS (ESI) m/z (%): 423.3
100) [M ? Na]; HRMS (ESI) Calcd. For C H NaO (M ? Na) requires
28 32 2
?
?1
?
(
4
23.2294, Found: 423.2296.
trans-3-(2-Methylbenzyl)-4-((E)-3-o-tolylprop-1-enyl)cyclohex-1-ene-1,4-
diyl)diethanone (trans-2g)
3
1
9
1
8 mg, yield (2g): 95 %, a colorless oil; IR (CH Cl ): m 3061, 3016, 2928, 1703,
2
2
666, 1644, 1603, 1491, 1460, 1388, 1351, 1253, 1213, 1156, 1107, 1080, 1050,
-
1
1
82, 956, 915, 862, 743, 622 cm
.90–2.01 (2H, m, CH ), 2.08 (3H, s, CH ), 2.11 (3H, s, CH ), 2.19–2.29 (8H, m,
; H NMR (300 MHz, CDCl , TMS): d
3
2
3
3
CH ? CH ? CH ? CH), 2.50–2.62 (1H, m, CH), 2.90 (1H, dd, J = 4.2, 12.6 Hz,
3
3
CH), 3.12–3.16 (1H, m, CH), 3.45 (2H, d, J = 6.0 Hz, CH ), 5.39 (1H, d,
2
J = 15.9 Hz, CH), 5.82 (1H, dt, J = 6.0, 15.9 Hz, CH), 6.55 (1H, d, J = 5.1 Hz,
1
3
CH), 7.01–7.15 (8H, m, ArH); C NMR (75 MHz, CDCl , TMS): d 19.3, 19.4,
3
2
1
2
0.8, 24.3, 24.6, 25.0, 35.4, 36.7, 39.5, 56.8, 125.8, 126.2, 126.5, 126.6, 129.1,
30.0, 130.3, 130.5, 131.5, 131.9, 136.0, 136.1, 136.4, 137.5, 137.6, 144.4, 198.9,
?
08.4; MS (ESI) m/z (%): 423.3 (100) [M ? Na]; HRMS (ESI) Calcd. For
?
1
?
C H NaO (M ? Na) requires 423.2294, Found: 423.2299.
2
8
32
2
trans-3-(4-Bromobenzyl)-4-((E)-3-(4-bromophenyl)prop-1-enyl)cyclohex-1-ene-1,
-diyl)diethanone (trans-2h)
4
5
1
9
1
2
1 mg, yield (2h): 96 %, a colorless oil; IR (CH Cl ): m 3023, 2928, 2854, 1704,
2
2
666, 1644, 1487, 1431, 1403, 1389, 1352, 1254, 1214, 1156, 1101, 1071, 1011,
-
1
1
81, 837, 803, 739, 704, 631 cm
.86–1.97 (1H, m, CH), 2.02–2.07 (1H, m, CH), 2.11 (6H, s, CH ? CH ),
; H NMR (300 MHz, CDCl , TMS): d
3
3
3
.14–2.24 (2H, m, CH ), 2.50–2.58 (1H, m, CH), 2.88 (1H, dd, J = 4.2, 12.9 Hz,
2
CH), 3.16–3.20 (1H, m, CH), 3.40 (2H, d, J = 7.2 Hz, CH ), 5.46 (1H, d,
2
J = 15.9 Hz, CH), 5.79 (1H, dt, J = 7.2, 15.9 Hz, CH), 6.55 (1H, d, J = 4.5 Hz,
1
CH), 7.00–7.05 (4H, m, ArH), 7.40–7.44 (4H, m, ArH); C NMR (75 MHz, CDCl3,
3
TMS): d 20.8, 24.7, 24.8, 25.1, 37.6, 38.7, 41.0, 56.6, 130.1, 130.7, 131.5, 131.5,
1
31.7, 131.7, 131.8, 132.1, 136.7, 138.4, 138.5, 142.9, 198.7, 208.3; MS (ESI)
1
23

Dimerization of MBH acetates catalyzed by organocatalysts
15
?
m/z (%): 553.0 (100) [M ? Na]; HRMS (ESI) Calcd. For C H Br NaO
(
?1
2
2
6
26
2
?
M ? Na) requires 551.0192, Found: 551.0207.
Diethyl 4-vinylcyclohex-1-ene-1,4-dicarboxylate (2i)
[
8b] 1
2
4 mg, yield: 95 %, this is a known compound.
H NMR (300 MHz, CDCl3,
TMS): d 1.22–1.31 (6H, m, CH ? CH ), 1.76–1.85 (1H, m, CH), 2.06–2.14 (1H,
3
3
m, CH), 2.31–2.38 (3H, m, CH ? CH), 2.77–2.84 (1H, m, CH), 4.11–4.21 (4H, m,
CH ? CH ), 5.08–5.17 (2H, m, CH ), 5.88 (1H, dd, J = 10.8, 17.1 Hz, CH), 6.97
2
2
2
2
(
1H, s, CH).
trans-Diethyl 3-methyl-4-((E)-prop-1-enyl)cyclohex-1-ene-1,4-dicarboxylate
trans-2j)
(
[8b] 1
2
8 mg, yield (2j): [99 %, this is a known compound.
H NMR (300 MHz,
CDCl , TMS): d 0.98 (3H, d, J = 7.5 Hz, CH ), 1.20–1.30 (6H, m, CH ? CH ),
3
3
3
3
1
2
1
.68–1.78 (4H, m, CH ? CH ), 2.09–2.18 (1H, m, CH), 2.30–2.37 (2H, m, CH ),
3 2
.98–3.02 (1H, m, CH), 4.07–4.20 (4H, m, CH ? CH ), 5.40 (1H, dd, J = 1.2,
2
2
5.6 Hz, CH), 5.50–5.62 (1H, m, CH), 6.92 (1H, d, J = 5.1 Hz, CH).
trans-Diethyl 4-((E)-but-1-enyl)-3-ethylcyclohex-1-ene-1,4-dicarboxylate (trans-2k)
2
9 mg, yield (2k): 94 %, a colorless oil; IR (CH Cl ): m 2963, 2933, 2874, 1723,
-1 1
2
2
1
650, 1462, 1380, 1366, 1247, 1176, 1094, 1037, 976, 863, 781, 737 cm ; H
NMR (300 MHz, CDCl , TMS): d 0.95–1.03 (6H, m, CH ? CH ), 1.19–1.31 (7H,
3
3
3
m, CH ? CH ? CH), 1.64–1.79 (2H, m, CH ), 2.01–2.08 (2H, m, CH ),
3
3
2
2
2
4
.10–2.19 (1H, m, CH), 2.36–2.38 (2H, m, CH ), 2.74–2.77 (1H, m, CH),
2
.08–4.21 (4H, m, CH ? CH ), 5.38 (1H, d, J = 15.9 Hz, CH), 5.59 (1H, dt,
2
2
1
3
J = 6.3, 15.9 Hz, CH), 7.08 (1H, d, J = 4.8 Hz, CH); C NMR (75 MHz, CDCl3,
TMS): d 12.4, 13.6, 14.0, 14.2, 22.1, 24.6, 25.5, 25.9, 42.4, 50.3, 60.3, 60.7, 128.8,
?
29.3, 133.2, 142.0, 167.2, 175.0; MS (ESI) m/z (%): 331.1 (100) [M ? Na];
1
?
1
?
(M ? Na) requires 331.1880, Found:
HRMS (ESI) Calcd. For C H NaO
4
1
8
28
3
31.1884.
trans-Diethyl 4-((E)-pent-1-enyl)-3-propylcyclohex-1-ene-1,4-dicarboxylate
trans-2l)
(
3
1
6
1
2 mg, yield (2l): 95 %, a colorless oil; IR (CH Cl ): m 2958, 2933, 2872, 1721,
2
2
651, 1463, 1380, 1366, 1284, 1236, 1176, 1094, 1054, 1034, 976, 781, 759, 733,
-
1 1
13 cm ; H NMR (300 MHz, CDCl , TMS): d 0.85–0.94 (6H, m, CH ? CH ),
3
3
3
.19–1.31 (7H, m, CH ? CH ? CH), 1.34–1.42 (3H, m, CH ? CH), 1.49–1.61
3
3
2
(
CH), 2.32–2.37 (2H, m, CH ), 2.82–2.85 (1H, m, CH), 4.07–4.21 (4H, m,
2H, m, CH ), 1.70–1.80 (1H, m, CH), 1.99–2.06 (2H, m, CH ), 2.12–2.20 (1H, m,
2 2
2
CH ? CH ), 5.38 (1H, d, J = 15.6 Hz, CH), 5.54 (1H, dt, J = 6.6, 15.6 Hz, CH),
2
2
1
3
7
.05 (1H, d, J = 5.1 Hz, CH); C NMR (75 MHz, CDCl , TMS): d 13.5, 14.0,
3
1
4.2, 14.3, 20.9, 22.1, 22.4, 25.5, 33.9, 34.9, 40.4, 50.3, 60.3, 60.7, 128.6, 130.5,
123

16
H.-P. Deng et al.
?
31.7, 142.3, 167.2, 175.0; MS (ESI) m/z (%): 359.2 (100) [M ? Na]; HRMS
ESI) Calcd. For C H NaO (M ? Na) requires 359.2193, Found: 359.2198.
20 32 4
1
?
1
?
(
trans-Diethyl 3-butyl-4-((E)-hex-1-enyl)cyclohex-1-ene-1,4-dicarboxylate
trans-2m)
(
3
1
1 mg, yield (2m): 85 %, a colorless oil; IR (CH Cl ): m 2957, 2929, 2858, 1724,
-1 1
2
2
650, 1464, 1379, 1366, 1254, 1178, 1094, 1032, 976, 862, 782, 738, 608 cm ; H
NMR (300 MHz, CDCl , TMS): d 0.86–0.92 (6H, m, CH ? CH ), 1.19–1.36
3
3
3
(
13H, m, CH ? CH ? CH ? CH ? CH ? CH), 1.43–1.49 (1H, m, CH),
3 3 2 2 2
1
.55–1.63 (1H, m, CH), 1.69–1.80 (2H, m, CH ), 2.01–2.08 (2H, m, CH ),
2 2
2
.12–2.20 (1H, m, CH), 2.33–2.37 (2H, m, CH ), 2.79–2.83 (1H, m, CH), 4.07–4.21
2
(
4H, m, CH ? CH ), 5.38 (1H, d, J = 15.6 Hz, CH), 5.54 (1H, dt, J = 6.6,
2 2
1
3
1
1
6
5.6 Hz, CH), 7.06 (1H, d, J = 4.5 Hz, CH); C NMR (75 MHz, CDCl , TMS): d
3
3.8, 13.9, 14.0, 14.2, 22.0, 22.1, 22.9, 25.5, 29.9, 31.3, 31.4, 32.4, 40.7, 50.4, 60.3,
0.6, 128.5, 130.3, 131.9, 142.4, 167.2, 175.0; MS (ESI) m/z (%): 387.2 (100)
?
?1
?
[M ? Na]; HRMS (ESI) Calcd. For C H NaO (M ? Na) requires 387.2506,
22 36 4
Found: 387.2510.
Acknowledgments We thank the Shanghai Municipal Committee of Science and Technology
08dj1400100-2), National Basic Research Program of China (973)-2010CB833302, the Fundamental
(
Research Funds for the Central Universities and the National Natural Science Foundation of China for
financial support (21072206, 20472096, 20872162, 20672127, 20821002 and 20732008).
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