Synthesis of Cross-Conjugated Polyenes via Palladium-Catalyzed Oxidative C-C Bond Forming Cascade Reactions of Allenes

Article abstract of DOI:10.1021/acs.joc.0c00186

An efficient palladium-catalyzed oxidative C-C bond forming cascade reaction of allenes involving a coupling between an enallene and an allenyne followed by a carbocyclization of the generated Pd-intermediate was developed. This cascade reaction afforded functionalized cross-conjugated polyenes. The enallene is initially activated by palladium and reacts with the allenyne to give the cross-conjugated polyenes.

Full text of DOI:10.1021/acs.joc.0c00186

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Article
Synthesis of Cross-Conjugated Polyenes via Palladium-Catalyzed
Oxidative C-C Bond Forming Cascade Reactions of Allenes
Veluru Ramesh Naidu, and Jan-E. Bäckvall
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c00186 • Publication Date (Web): 24 Mar 2020
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The Journal of Organic Chemistry
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Synthesis of Cross-Conjugated Polyenes via Palladium-Catalyzed
Oxidative C-C Bond Forming Cascade Reactions of Allenes
Veluru Ramesh Naidu*,†,‡ and Jan-E. Bäckvall*,†,‡
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†Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
‡Department of Natural Sciences, Mid Sweden University, Holmgatan 10, SE-851 79, Sundsvall, Sweden
Supporting Information
In recent years, acyclic cross-conjugated polyenes (dendralenes)
have been used in diene transmissive Diels-Alder (DTDA)
sequences for rapid generation of complex scaffolds bearing
multiple stereogenic centers (Scheme 2).5 Due to regioselective
functionalization of the multiple olefinic sites, other applications
of dendralenes are found in the synthesis of ivyane family
compounds,6 vinylogous Nazarov reactions,7 organocatalytic
domino cyclizations,8 oxidative reactions9a and metathesis of
[3]dendralene-Fe(CO)3 complexes.9b However, synthetic methods
for the preparation of higher cross-conjugated polyenes are quite
limited as one step reactions. In this respect, Hopf, Sherburn,
Shimizu and their coworkers reported on acyclic cross conjugated
polyenes.3b,10,11,12 Recently, the Lipshutz group reported a tandem
borylation/Suzuki-Miyaura reaction for the synthesis of
cross-conjugated polyenes such as [4]- and [5]dendralene,
(Scheme 3A).13
ABSTRACT: An efficient palladium-catalyzed oxidative C-C
bond forming cascade reaction of allenes involving a coupling
between an enallene and an allenyne followed by
a
carbocyclization of the generated Pd-intermediate was developed.
This cascade reaction afforded functionalized cross-conjugated
polyenes. The enallene is initially activated by palladium and
reacts with the allenyne to give the cross-conjugated polyenes.
INTRODUCTION
Stereo- or regiocontrolled selective construction of unsaturated
molecular scaffolds through sequential multiple carbon-carbon
(C–C) bond formation remains one of the major challenges in
organic chemistry. In particular, in cascade reactions, transition
metal-catalyzed cyclizations of allenes provide efficient and
atom-economical routes to polyunsaturated molecules.1 Polyenes
and oligoenes occur as structural elements in pharmaceutically
active compounds and important natural products such as Vitamin
A, Lycopene, β-carotene, Lutein, lissoclinolide, and naturally
occurring [3]dendralenes etc. (Scheme 1).2 The synthesis of such
non-aromatic cross-conjugated [3]dendralenes have recently
attracted considerable interest.3,4
Scheme 3. Example of Polyene Synthesis and Proposal for this
Work
A) Example of polyene synthesis ( ref. 13).
Cu(iPr)Cl
Pd(DPEphos)Cl2
Et3N
Et3N
B2Pin2
R
O
B
R
R
n= 1, 2
2 wt% TPGS-
750-M/H2O
O
R
2nd allenoate
n
BzO
polyenes
(i.e, [4]- or [5]dendralene)
Scheme 1. Examples of Polyene Compounds
B) This work
X
Polyene
Oligo ene natural products examples: a) Acyclic linear conjugated poly enes
hydrocarbons
X
HO
OH
OH
EtO
n
O
n
Pd(II)
O
Lissoclinolide
(Antibiotic)
+
O
Vitamin A
Linear polyenes
Annulenes
this work
Fulvene
Oxidant
Allenyne
CO2Me
CO2Me
n
Allene
Enallene
EtO2C
X=
Cumulene
Dendralenes
Radiallene
Cross-conjugated
polyene
ref. 9b
Lycopene
OH
In the past decade, our research group has focused on
Pd(II)-catalyzed oxidative carbocyclization reactions of allenes1h
and we reported the synthesis of various types of [3]dendralenes
via C–C bond formation.3d Compared to intramolecular reactions
of allenes, intermolecular couplings of allenes are more challen-
ging and would provide an array of novel conjugated structures.
To the best of our knowledge intermolecular cascade reactions
between allenes with C-C bond formation for the synthesis of
cross-conjugated polyenes have not yet been reported in a one-pot
reaction. We therefore decided to study palladium-(II)catalyzed
oxidative coupling and carbocyclization reactions of enallenes
with allenynes for the synthesis of polyenes (Scheme 3 B). These
cross-conjugated polyenes will have the (Z)-configuration at the
e.g. Essential oils:
[3]dendralenes
Triene
Triene-OH
Scheme 2. Examples of Cross-Conjugated Polyenes
applications
O
O
H
H
Ref 12
Ref 12
MeN
O
NMe
O
H
H
O
RT,
and heat
RT,
H
H
NMe
O
tetracyclic
[5.6.6.6]fenestrane
O
O
N
Me
Tris adducts
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middle double bond. The synthesis of the unsubstituted
Table 1. Optimizatiion of the Reactiona
1
2
3
4
5
6
7
8
(E)-isomer of the corresponding polyene has been reported by
MeO2C CO2Me
MeO2C CO2Me
EtO
Paddon-Row and Sherburn (lower box, Scheme 3B).9b
Pd(II) (5 mol%) ,
BQ, (1.1 eq.),
MeO2C CO2Me
O
+
+
CH3CN, 80 oC, 12 h
In this report, palladium-catalyzed intermolecular carbocycliza-
tion cascade reactions provide a wide variety of interesting
polyene products in high yield and with excellent regio- and
stereoselectivity (Scheme 3, B).
(1.0 eq.)
(1.1 eq.)
2a
5
1a
EtO2C
3a
Entry
Cat. (Pd)
Solvent
Yield (%)b
Recovery of
RESULTS AND DISCUSSION
1a/2a (%)b
3a
5
1
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(TFA)2
DCE
64
51
55
43
50
33
65
75
-
6
6
-
-
In our initial investigation, allenyne 1a and enallene 2a were
chosen as the substrates for this challenging transformation
(Scheme 4).
9
2
Dioxane
DMSO
THF
-
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3
-
4 c
5c
6 c
-
-
MeOH
Acetone
Toluene
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
4
-
-
Scheme 4. Cascade Reaction
-
E
E
E
E
7
7
-
-
EtO
Method A
or
8
-
+
O
9
-
-
-
94/91
Method B
10
11
12
13g
14 df
15de
16deh
17dhi
18dhj
Pd(PPh3)2Cl2
Pd(MeCN)2Cl2
Pd(acac)2
Pd(OAc)2
-
70/71
2a
1a
-
71/47
E= CO2Me
Method B
3a
EtO2C
85-90%
60
80
83
88
94
91
90
6
-
-
-
-
-
-
-
-
-
-
-
-
-
PdII
Pd0
1
2a
H2O
+
HQ
Co (salophen)ox
Pd(OAc)2
Pd(OAc)2
3a
Pd(OAc)2
BQ
Co (salophen)
1/2 O2
Pd(OAc)2
Method A: 2a (2 equiv), Pd(OAc)2 (5 mol%), BQ (2 equiv),
Pd(OAc)2
o
Na2CO3 (20 mol%), CH3CN, 80 C, 24 h. Method B: Pd(OAc)2
aThe reaction was conducted in the indicated solvent (1 mL) at 80
oC using 1a (0.1 mmol), allene-ene 2a (0.11 mmol), and BQ (1.1
equiv) in the presence of palladium catalyst (5 mol%). bYield
determined by 1H NMR analysis using anisole as the internal
standard. cThe reaction was run at 60 oC. d2a (2.0 equiv) and 2.0
equiv of BQ was used. e0.2 equiv of Na2CO3 was used. f1 mol%
Pd(OAc)2 was used. g2a (1.5 equiv) and 1.5 equiv of BQ was
used. hReaction time 24 h. iEt3N (20 mol%). jAcOH (20 mol%).
(5 mol%), BQ (20 mol%), Co(salophen) (5 mol%), Na2CO3 (20
mol%), CH3CN, 80 oC, O2 balloon, 24 h.
Preparation of Starting Materials. All allenynes 1 were
prepared from propargyl malonate and the corresponding
bromoallenes (Scheme 5). The eneallenes 2 were synthesized
from
propargyl
alcohol
derivatives
and
subsequent
1,3-rearrangement or iron-catalyzed SN2’ Grignard reaction (see
Supporting Information).
and Pd(PhCN)2Cl2 were not suitable for the reaction and in these
cases the allenyne 1a and enallene 2a were recovered (Table 1,
entries 9-11). However, Pd(acac)2 catalyzed the reaction
efficiently to give the product 3a in 60ꢁ% yield. (Table 1, entry
12). In further optimizations, treatment of 1a and 1.5 equiv. of 2a
with 5 molꢁ% of Pd(OAc)2, and 1.5 equiv. of BQ afforded 3a in
80ꢁ% yield (Table 1, entry 13). Increasing 1a and BQ to 2.0 equiv.
each with 1 molꢁ% of Pd(OAc)2 improved the yield of 3a to 83%
(Table 1, entry 14). The yield of 3a further increased with the
addition 0.2 equiv. of Na2CO3 (Table 1, entry 15). With an
increased reaction time, we found that treatment of 1a and 2.0ꢀ
equiv. of 2a with 5ꢀmolꢁ% of Pd(OAc)2, and 2.0ꢀequiv. of BQ in
Scheme 5. Preparation of Allenynes
E
E
E
E
H
1a
1b
1c
1d
E= CO2Me, R1=R2= Me
E= CO2Et, R1=R2= Me
E= CO2Me, R1=R2= - (CH2)5-
E= CO2Me, R1= Me, R2= t-Bu
Br
1.2 equiv. NaH
THF, 0 oC-60 o
20 h
C
+
R1
R2
R1
1a-d
R2
1ax
1cx
1dx
R1=R2= Me
R1=R2= -(CH2)5-
R1= Me, R2= t-Bu
OH OH
OR OR
EtO2C
CO2Et
R2
NaH, RX
THF or DMF
LiAlH4
1e
1f
Et2O
R= Me, R1=R2= Me
R= Me, R1=R2= -(CH2)5-
R= Me,R1= Me, R2= -Bu
R1
1a,
R1
R2
1ax,
1g
t
R1
R2
o
CH3CN at 80 C for 24 h afforded 3a in 94ꢁ% yield (Method-A)
(Table 1, entryꢀ16). Additives such as Et3N or AcOH did not
improve the yield of 3a (Table 1, entriesꢀ17-18).
1e-g, 1j
1c-1d
1cx-1dx
1j
O
O
R= Bn, R1=R2= Me
R1=R2= Me
2,2-Dimethoxy-
propane
p-TsOHH2O
Acetone
1h
1i
t
R1= Me, R2= -Bu
To demonstrate the necessity of the olefin group in the enallene
2a15 comparative experiments with allenes lacking the pending
olefin were carried out. Without the pending olefin, these
reactions, failed to give any cross-conjugated polyene product 3
with method A in CH3CN (Scheme 6). Thus, when 4a and 4b
were allowed to react with 1a, no detectable amounts of 3 were
formed.
R1
R2
1h-1i
In preliminary experiments, we observed that treatment of 1a and
1.1ꢀequiv of 2a with 5ꢀmolꢁ% of Pd(OAc)2 and 1.1 equiv. of
o
benzoquinone (BQ) in DCE at 80 C gave a 64ꢁ% NMR yield of
the regio- and stereodefined dendralene derivative 3a together
with 6ꢁ% of cycloisomerization product 5.14 With these inspiring
results in hand, we set out to determine the role of the solvent and
the Pd(II) catalyst. In screening of various solvents in the presence
of Pd(OAc)2 catalyst (Table 1, entries 1–8), CH3CN was found to
be the best solvent, which delivered the product 3a in 75ꢁ% yield
without formation of side product 5 (entry 8). Furthermore,
palladium catalyst screening showed that Pd(TFA)2, Pd(PPh3)2Cl2
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The Journal of Organic Chemistry
Scheme 6. Comparative Experiment
Table 2. Scope of Substrate 1a
1
2
3
4
5
6
MeO2C CO2Me
Pd(OAc)2 (5 mol%)
BQ, (2.0 eq.)
Na2CO3 (0.2 eq.)
R
R
R
MeO2C CO2Me
R
R
EtO2C
EtO
Method A
+
+
CH3CN, 80 oC, 24 h
O
or
Method B
(Method A)
R
(2.0 eq.)
2a
(1.0 eq.)
4
or
1
2a (
2.0 eq.)
(1.0 eq.)
1a
EtO2C
3
EtO2C
3
7
8
R = CO2Me, CO2Et, CH2OMe, CH2OBn, -CH2OC(CH3)2OCH2-
90% yield
2a
4a
R =
R =
MeO2C
MeO2C
EtO2C
MeO2C
CO2Me
CO2Me
CO2Me
CO2Et
4b
R = H or
Complex mixture
9
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These results are in accordance with previous results that the
olefin group of 2a is an indispensable assisting/directing group for
activation of the allene.15
EtO2C
EtO2C
EtO2C
3b
A-89%
EtO2C
3c
A-83%
In further studies, we investigated Pd(II)-catalyzed aerobic
oxidative coupling–carbocyclization reactions between allenyne
1a and enallene 2a for the synthesis of 3a (Scheme 4, Method B).
We have previously developed various biomimetic methods for
palladium-catalyzed aerobic oxidation of unsaturated substrates.16
The employment of an aerobic biomimetic oxidation system is an
environmentally benign process associated with high atom
economy.17 A key feature of Scheme 4, Method B is the multistep
3d
3a
A-82%, B- 78 %
A- 90%, B- 85%
MeO
MeO
MeO
OMe
OMe
OMe
O
O
electron transfer occurring, which enables
a mild aerobic
EtO2C
3f
A-77%
EtO2C
3g
A-81%
EtO2C
3e
A-80%
oxidation. This multistep electron transfer system involves three
redox pairs: PdII/Pd0, (BQ)/HQ, and Co(salophen)ox/Co(salophen.
The BQ and Co(salophen) are used as electron transfer mediators
(ETMs) and molecular oxygen is applied as the oxidant. We
found that reaction of 1a with 2a in the presence of catalytic
amounts of Pd(OAc)2 (5ꢀmolꢁ%), BQ (20ꢀmolꢁ%) and Co(salophen)
(5 molꢁ%) in CH3CN at 80ꢁ°C under molecular oxygen (1 atm) for
24ꢀh afforded 3a in 85ꢁ% yield (Method B). Under optimized
reaction conditions method A and B, we investigated the scope of
the reaction by using different allenyne substrates (Table 2, 1a–
1j).
3h
EtO2C
A-75%
O
O
BnO
OBn
3j
A-83%
EtO2C
3i
A-34%
EtO2C
aIsolated yield after column chromatography Method A: 2a (2
equiv), Pd(OAc)2 (5 mol%), BQ (2 equiv), Na2CO3 (20 mol%),
CH3CN, 80 C, 24 h. Method B: Pd(OAc)2 (5 mol%), BQ (20
mol%), Co(salophen) (5 mol%), Na2CO3 (20 mol%), CH3CN, 80
Under standard non-aerobic conditions (Method A), with methyl
groups at the terminal position of the allene moiety of the
allenenyne or when these methyl groups were changed to
cyclohexylidene or t-Bu, Me, the reaction with 2a gave the
corresponding cross-conjugated polyene (Table 2, 3a–3d) in good
yields (82–90%). The use of either stoichiometric amounts of BQ
(Method A) or catalytic amounts of BQ under aerobic conditions
(Method B) afforded similar results, as shown in Table 2 from the
examples 3a and 3d. It is worth noting that the reaction of
allenyne substrates 1e–1j (Table 2) having two methyl ethers, a
1,3 dioxane, or two benzyl ethers in place of the two carboalkoxy
groups, along with cyclopentylidene or tertiary butyl on the allene
moiety afforded the corresponding polyene derivatives (Table 2,
3e–3j) selectively in good yields (70–81%), except for 1i, which
afforded 3i in 34 % yield. These results show that the malonate
o
oC, O2 balloon, 24 h.
To expand the scope of the method, we tested differently
substituted enallenes 2 for the coupling–carbocyclization cascade
reaction using allenyne 1a as the co-substrate. Under standard
conditions (Method A), a number of functionalized enallenes 2
served as excellent candidates for formation of cross-conjugated
polyenes in good yields. When allyl‐substituted 2,3‐dienoate (2k)
was employed, the reaction gave the desired product 3k in 84%
yield. Variation of the methyl groups on the allene moiety of 2,
e.g. deuterated methyls (2l), cyclohexylidene group (2m),
cyclopentylidene group (2n) or one methyl presence (2o), in the
reaction with 1a provided the corresponding cross-conjugated
polyenes in good yields (Table 3, 3l–3o). Moreover, substrates
2p–2s with methyl, ethyl or phenyl substitution on the olefin
moiety afforded 3p–3s (Tableꢀ3) in moderate to good yields (52–
80%). Reaction of substituted enallenes 2t–2v with 1a afforded
the desired products 3t–3v in 60–80% yield (Tableꢀ3). As shown
in Table 3, the reaction also works under aerobic conditions with
catalytic amounts of BQ together with Co(salophen) in catalytic
amounts (Method B). Thus, reaction of enallenes 2k, 2m–2n with
1a using molecular oxygen as the oxidant afforded products 3k,
3m–3n in 75-85% yields (Tableꢀ3).
group of the tether is not necessary for
transformation.
a successful
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triggered by the coordination of the assisting olefin.15 Vinyl-
1
2
3
4
5
6
7
8
palladium intermediate Int‐2 would then undergo an insertion of
the vinylpaladium bond into the alkyne of allenyne 1, which leads
to Int‐3. Subsequent intramolecular insertion of the vinyl-
palladium bond of Int‐3 into the allene would lead to (π‐allyl)-
Table 3. Scope of Enallene Substrates 2a
R3
E
E
E
E
R1
R4
R2
Method A
+
MeO2C CO2Me
or
Pd(II) (5 mol%)
Rm
R
EtO2C
EtO2C
Method B
BQ, (2 eq.)
2
1a
R4
R3
+
+
2k
2l
Rm=R=Me, R1=CO2Et, R2=R3=R4=H
Na2CO3 (0.2 eq.)
CH3CN,75 oC, 1 h
R1
E = CO2Me
D3C
CD3
Rm=R=CD3, R1=CH2CO2Et, R2=R3=R4=H
Rm=R=-(CH2)5-, R1=CH2CO2Et, R2=R3=R4=H
Rm=R=-(CH2)4-, R1=CH2CO2Et, R2=R3=R4=H
Rm=Me, R=H, R1=CH2CO2Et, R2=R3=R4=H
Rm=R=Me, R1=CO2Et, R2=R3=H, R4=Et
Rm=R=Me, R1=CO2Et, R2=R3=H, R4=Ph
Rm=R=Me, R1=CO2Et, R2=H, R3=Me, R4=Me
Rm=R=Me, R1=CH2CO2Et, R2=Me, R3=H, R4=H
Rm=R=Me, R1=Bu, R2=R3=R4=H
R2
1a
(1.0 eq.)
2m
2n
2o
2p
2q
2r
3
2a
2a-d
(1.0 eq.)
1
6 (1.0 eq.)
Conv = 72 %
:
1
9
MeO2C CO2Me
CO2Me
MeO2C
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
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52
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54
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57
58
59
60
2s
2t
(1)
+
CD3
CD2
2u
2v
Rm=R=Me, R1=Ph, R2=R3=R4=H
Rm=R=Me, R1=CH2CH2OH, R2=R3=R4=H
KIE- kH/kD = 3.5
eq. (1)
EtO2C
3a-d5
EtO2C
3a
3a/3a-d5 = 1.8:1
MeO2C
MeO2C
CO2Me
MeO2C
CO2Me
MeO2C
CO2Me
CO2Me
MeO2C CO2Me
CD3
CD2
MeO2C
CO2Me
Pd(II) (5 mol%)
BQ, (1 eq.)
EtO2C
+
(2)
CO2Et
3n
A-75%,
B-77%
Na2CO3 (0.2 eq.)
3m
A-78%,
B-80%
EtO2C 3l
EtO2C
EtO2C
CH3CN, 75 o
C
3k
A-72%
A-85%, B-87%
(0.5 eq.)
(1.0 eq.)
30 Min.
1a
2a
< 33% Yield
3a
EtO2C
MeO2C
MeO2C
CO2Me
MeO2C
CO2Me
MeO2C
CO2Me
CO2Me
KIE- kH/kD = 3.4
MeO2C
CO2Me
MeO2C CO2Me
Pd(II) (5 mol%)
BQ, (1 eq.)
EtO2C
Na2CO3 (0.2 eq.)
+
CD3
CD2
3a-d5
(3)
CH3CN, 75 o
30 Min.
C
D3C
CD3
Ph
Et
CO2Et
CO2Et
CO2Et
1a
2a-d
6 (1.0 eq.)
(0.5 eq.)
3q
EtO2C
3o
3p
3r
A-71%
< 33% Yield
A-57%
EtO2C
A-61%,
A-76%
MeO2C
MeO2C
CO2Me
CO2Me
MeO2C
MeO2C
CO2Me
CO2Me
palladium intermediate Int‐4. Subsequent β‐hydride elimination
via C(sp3)−H bond cleavage would provide the cross-conjugated
polyene 3 and release Pd0 for the next cycle.
Bu
Scheme 7. Proposed Mechanism for the Formation of 3
HO
3s
A-80%
3t
CO2Et
3v
A-63%
3u
A-80%
E
E
HQ
A-60% (E:Z)
BQ
E1
aIsolated yield after column chromatography. Method A: 2a (2
-HX
or
O2, ETM
PdX2
Pd(0)
equiv), Pd(OAc)2 (5 mol%), BQ (2 equiv), Na2CO3 (20 mol%),
o
2
CH3CN, 80 C, 24 h. Method B: Pd(OAc)2 (5 mol%), BQ (20
HPdX
mol%), Co(salophen) (5 mol%), Na2CO3 (20 mol%), CH3CN, 80
E1
E1
oC, O2 balloon, 24 h.
3
Pd
X
-hydride
elimination
X
Int-1
E
To gain further insight into the reaction mechanism, the deuterium
kinetic isotope effects (KIE) were studied (eqs. 1-3). An
intermolecular competition experiment was conducted at 75 °C
using a 1:1 mixture of 2a and 2a-d6 (eq. 1). The products ratio 3a
and 3a-d5 was measured as 1.8:1, from which the competitive KIE
was determined to kH/kD = 3.5 (see Supporting Information).
Furthermore, parallel kinetic experiments afforded a KIE (kH/kD
from initial rate) value of 3.4 (eqs. 2 and 3) which indicates the
initial allenylic C(sp3)−H bond cleavage is involved in the
rate-determining step in the reaction. The large competitive KIE
(kH/kD = 3.5) in C–H bond cleavage requires that this step is the
first irreversible step.
E
BQ
X
allene
attack
Pd
E1
Pd
X
Int-2
BQ
E1
E
E
E
E
Int-4
X
E
E
alkyne
insertion
Carbo-
cyclization
Pd
Pd
X
H
H
E= CO2CH3,
E1= CO2Et
1
E1
E1
Int-3
Based on the mechanistic studies including the KIE measurements
(eqs. 1-3) and our previous work,18 we propose the mechanism as
shown in Scheme 7. The large deuterium isotope effect found for
the C-H bond cleavage of the enallene 2a indicates that the
enallene is the compound first activated and not the allenyne.19
Initial reaction of Pd(OAc)2 with enallene 2 would give dienyl–
PdII complex Int‐2 via allenic C−H bond cleavage of chelated
π-complex Int‐1 (Scheme 7). This activation of the allene is
CONCLUSION
We have developed an efficient one-pot PdII‐catalyzed oxidative
coupling–carbocyclization cascade reaction for the synthesis of
cross-conjugated polyene via intermolecular C−C bond formation
and subsequent carbocyclization. This transformation allows
highly regio- and stereoselective formation of cross-conjugated
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The Journal of Organic Chemistry
polyenes using enallene and allenyne under aerobic conditions
Dimethyl-2-(prop-2-yn-1-yl)-2-(3,4,4-trimethyl-2λ5-penta-1,2-dien
-1-yl)malonate (1d). 1H NMR (400 MHz, CDCl3)  = 5.64 (q, J =
2.9 Hz, 1H), 3.74 (d, J = 9.5 Hz, 6H), 2.87 (d, J = 2.7 Hz, 2H),
1.97 (t, J = 2.7 Hz, 1H), 1.71 (d, J = 2.8 Hz, 3H), 1.02 (s, 9H);
13C{1H} NMR (100 MHz, CDCl3)  = 200.0, 169.6, 114.2, 89.2,
79.5, 70.7, 57.7, 52.8, 52.7, 33.7, 28.8, 24.6, 14.5; HRMS (ESI)
m/z: [M + Na]+ Calcd for C16H22O4Na: 301.1410; Found:
301.1421. Isolated yield: 32% (0.79 g), as a liquid. Column
chromatography on silica gel (pentane/ethyl acetate = 30/1).
1
2
3
4
5
6
7
with environmentally friendly O2 as terminal oxidant. These
important cross-conjugated polyenes, which are readily obtained
in a one-pot cascade reaction in the present work are difficult to
prepare by other methods. Further studies on the scope of natural
product synthesis and other synthetic application of this new
cascade reaction are currently underway in our laboratory.
EXPERIMENTAL SECTION
8
9
General Information. For the synthesis of complex molecules,
unless otherwise noted, all reagents were used as received from
the commercial suppliers. Pd(OAc)2 was obtained from Pressure
Chemicals and used without further purification. Alkynes were
commercially available from Sigma Aldrich or Acros. The
palladium-catalyzed cascade reactions could be performed
without any efforts to exclude moisture. DCE was distilled using
CaH2, Dry THF and toluene, were obtained froma VAC Solvent
Purifier. The other dry solvents were purchased from Sigma
Aldrich. Reactions were monitored using thin-layer
chromatography (TLC) (SiO2). TLC plates were visualized with
UV light (254 nm) or KMnO4 stain. Flash chromatography was
carried out with 60Å (particle size 35 - 70 μm) normal flash silica
gel. NMR spectra were recorded at 400 MHz (1H) or 500 MHz
(1H) and at 100 MHz (13C) or 125 MHz (13C), respectively.
Chemical shifts (δ) are reported in ppm, using the residual solvent
peak in CDCl3 (H = 7.26 and C = 77.0 ppm) as internal standard,
and coupling constants (J) are given in Hz. HRMS were recorded
using ESI-TOF techniques.
Representative Procedure for the Synthesis of 1ax, 1cx, and
1dx: Synthesis of 1ax. To a suspension of LiAlH4 (171 mg, 4.5
mmol) in anhydrous Et2O (15 mL) was added a solution of 1a
(0.34 g, 1.5 mmol) in anhydrous Et2O (10 mL) at 0 °C. After the
addition, the mixture was stirred for another 2 h at rt. and
carefully quenched with H2O (5 mL). The resulting mixture was
extracted with diethyl ether (2 x 30 mL). The combined organic
layers were washed with H2O (20 mL), dried (Na2SO4) and the
solvent was removed under reduced pressure. The crude product
was purified by column chromatography (silica gel, pentane/ethyl
acetate = 1:3) to yield 1ax (203 mg, 79% yield) as a white solid.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Compounds 1cx and 1dx were prepared from 1c and 1d,
respectively, in the same manner.
Characterization of Products 1ax, 1cx and 1dx.
2-(3-Methyl-2λ5-buta-1,2-dien-1-yl)-2-(prop-2-yn-1-yl)propane-1,
1
3-diol (1ax). H NMR (400 MHz, CDCl3)  = 4.94 (sept, J = 2.9
Allenynes 1a20 and 1c21 were prepared as described in literature.
Allenynes 1b and 1d were prepared from propargylmalonate and
the corresponding bromoallene in a similar manner.20 All allene
derivatives 2a, 2k-2v and 4a-4b were prepared according to a
previously described procedures.3d,15,18c,22
Hz, 1H), 3.69 (s, 4H), 2.40 (d, J = 2.7 Hz, 2H), 2.04 (bs, 2H), 2.02
(d, J = 2.7 Hz, 1H), 1.71 (d, J = 3.0 Hz, 6H); 13C{1H} NMR (100
MHz, CDCl3)  = 201.7, 98.3, 90.0, 81.1, 70.6, 67.4, 44.5, 22.9,
20.6; HRMS (ESI) m/z: [M + Na]+ Calcd for C11H16O2Na:
203.1043; Found: 203.1049. Isolated yield: 79% (203 mg), as a
semi solid. Column chromatography (silica gel, pentane/ethyl
acetate = 1:3).
Representative Procedure for the Synthesis of 1b, and 1d:
Synthesis of 1b. To a suspension of NaH (60% in mineral oil,
0.456 g, 11.4 mmol) in anhydrous THF (60 ml) was added a
solution of diethyl propargylmalonate (2.0 g, 8.83 mmol) in
anhydrous THF (5 ml) at 0 ºC. After the addition, the mixture was
stirred for another 20 min at room temperature Then a solution of
bromoallene (2.6 g, 17.6 mmol) in anhydrous THF (5 ml) was
added at room temperature and the resulting mixture was refluxed
for 20 h. After the reaction was complete as monitored by TLC, it
was cooled to room temperature. Most of the solvent was
removed under vacuum, and then the reaction mixture was diluted
with 50 mL of Et2O and quenched with 10 mL of water. The
organic layer was separated, and the aqueous layer was extracted
with diethyl ether (2 x 20 mL). The combined organic layers were
dried over Na2SO4. Evaporation and column chromatography on
silica gel (pentane/ethyl acetate = 30/1) afforded 1b (0.71 g, 31%)
2-(2-Cyclohexylidene-2λ5-vinyl)-2-(prop-2-yn-1-yl)propane-1,3-di
ol (1cx). 1H NMR (400 MHz, CDCl3)  = 4.94 (quint, J = 2.9 Hz,
1H), 3.67 (d, J = 1.0 Hz, 4H), 2.39 (d, J = 2.7 Hz, 2H), 2.39 (bs,
2H), 2.16-2.06 (m, 4H), 2.00 (t, J = 2.7 Hz, 1H), 1.42-1.68 (m,
6H); 13C{1H} NMR (100 MHz, CDCl3)  = 198.3, 105.5, 89.8,
81.1, 70.6, 67.2, 44.4, 31.6, 27.3, 25.9, 22.9; HRMS (ESI) m/z:
[M + Na]+ Calcd for C14H20O2Na: 243.1356; Found: 243.1362.
Isolated yield: 81% (268 mg), as
a semi solid. Column
chromatography (silica gel, pentane/ethyl acetate = 1:2.5).
2-(Prop-2-yn-1-yl)-2-(3,4,4-trimethyl-2λ5-penta-1,2-dien-1-yl)pro
pane-1,3-diol (1dx). 1H NMR (400 MHz, CDCl3)  = 5.01 (q, J =
2.9 Hz, 1H), 3.70 (s, 4H), 2.41 (d, J = 2.7 Hz, 2H), 2.17 (bs, 2H),
2.02 (t, J = 2.7 Hz, 1H), 1.71 (d, J = 2.9 Hz, 3H), 1.05 (s, 9H);
13C{1H} NMR (100 MHz, CDCl3)  = 200.0, 111.6, 91.7, 81.2,
70.7, 67.5, 67.4, 44.3, 33.1, 29.0, 29.6, 22.8, 15.4; HRMS (ESI)
m/z: [M + Na]+ Calcd for C14H22O2Na: 245.1512; Found:
245.1521. Isolated yield: 97% (323 mg), as a semi solid. Column
chromatography (silica gel, pentane/ethyl acetate = 1:3).
Characterization of Allenynes 1b and 1d.
Diethyl-2-(3-methyl-2λ5-buta-1,2-dien-1-yl)-2-(prop-2-yn-1-yl)ma
1
lonate (1b). H NMR (400 MHz, CDCl3)  = 4.94 (sept, J = 2.9
Hz, 1H), 4.25-4.15 (m, 4H), 2.86 (d, J = 2.7 Hz, 2H), 1.95 (t, J =
2.7 Hz, 1H), 1.71 (d, J = 2.9 Hz, 6H), 1.25 (t, J = 7.1 Hz, 6H);
13C{1H} NMR (100 MHz, CDCl3)  = 201.7, 169.2, 100.5, 87.7,
79.6, 70.4, 61.7, 57.5, 24.3, 19.9, 13.9; HRMS (ESI) m/z: [M +
Na]+ Calcd for C15H20O4Na: 287.1254; Found 287.1263. Isolated
yield: 31% (0.71 g), as a liquid. Column chromatography on silica
gel (pentane/ethyl acetate = 30/1).
Representative Procedure for the Synthesis of 1e, 1f, and 1g:
Synthesis of 1e. To a suspension of 1ax (160 mg, 0.89 mmol) in
THF (10 mL) was added NaH (60% in mineral oil (142 mg, 3.6
mmol) at 0 °C. The reaction mixture was subsequently stirred for
30 minutes at the same temperature and then MeI (0.45 mL, 7.1
mmol) was added. The reaction mixture was warmed to room
temperature, and stirred for 1h. The reaction mixture was
quenched by addition of water, and extracted with Et2O (2 x 20
In
the
same
manner
1d
was
obtained
from
1-bromo-3,4,4-trimethyl-1,2-pentadiene.
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The Journal of Organic Chemistry
Page 6 of 11
mL). The combined organic layers were washed with brine (20
243.1356; Found: 243.1364. Isolated yield: 84% (111 mg), as a
1
2
3
4
5
6
7
8
mL), dried (Na2SO4) and the solvent was removed under reduced
pressure. The crude product was purified by flash column
chromatography (silica gel, pentane/ethyl acetate = 98:2) to afford
1e (150 mg, 81% yield) as a colorless oil.
colorless oil. Flash column chromatography (silica gel,
pentane/ethyl acetate = 97:3).
2,2-Dimethyl-5-(prop-2-yn-1-yl)-5-(3,4,4-trimethyl-2λ5-penta-1,2-
dien-1-yl)-1,3-dioxane (1i). 1H NMR (400 MHz, CDCl3)  = 4.98
(q, J = 2.9 Hz, 1H), 3.77-3.61 (m, 4H), 2.54 (qd, J = 13.0 Hz, 2.6
Hz, 2H), 1.99 (t, J = 2.7 Hz, 1H), 1.70 (d, J = 3.0 Hz, 3H), 1.40 (d,
J = 6.5 Hz, 6H), 1.04 (s, 9H); 13C{1H} NMR (100 MHz, CDCl3) 
= 199.9, 111.6, 97.9, 91.5, 81.5, 70.6, 66.9, 66.8, 36.8, 33.0, 29.0,
27.9, 24.0, 19.5, 15.3; HRMS (ESI) m/z: [M + Na]+ Calcd for
C17H26O2Na: 285.1825; Found: 285.1822. Isolated yield: 81%
(128 mg), as a colorless oil. Flash column chromatography (silica
gel, pentane/ethyl acetate = 97:3).
In the same manner 1f and 1g were obtained from 1cx and 1dx,
respectively.
Characterization of Products 1e, 1f and 1g.
4,4-Bis(methoxymethyl)-7-methyl-6λ5-octa-5,6-dien-1-yne (1e). 1H
NMR (400 MHz, CDCl3)  = 5.00 (sept, J = 2.9 Hz, 1H),
3.36-3.31 (m, 10H), 2.32 (d, J = 2.5 Hz, 2H), 1.94 (t, J = 2.5 Hz,
1H), 1.68 (d, J = 2.7 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3)
 = 201.5, 97.4, 90.7, 81.6, 75.4, 69.7, 59.3, 43.4, 23.4, 20.5;
HRMS (ESI) m/z: [M + Na]+ Calcd for C13H20O2Na: 231.1356;
Found: 231.1367. Isolated yield: 81% (150 mg), as a colorless oil.
Flash column chromatography (silica gel, pentane/ethyl acetate =
98:2).
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
.
Synthesis and Characterization of 1j.
(((2-(3-Methyl-2λ5-buta-1,2-dien-1-yl)-2-(prop-2-yn-1-yl)propa
ne-1,3-diyl)bis(oxy))bis(methylene))dibenzene (1j). To
a
suspension of NaH (60% in mineral oil, 124 mg, 3.1 mmol) in
anhydrous DMF (3 ml) was added a solution of 1ax (140 mg, 0.78
mmol) in anhydrous DMF (2 ml) at 0 ºC. After the addition, the
mixture was stirred for another 1 h at 0 ºC. Then BnBr (170 μL,
1.4 mmol) was added at 0 ºC and the resulting mixture was stirred
at rt overnight. Then the reaction mixture was diluted with 20 mL
of Et2O and quenched with 5 mL of water. The organic layer was
separated, and the aqueous layer was extracted with diethyl ether
(2 x 20mL). The combined organic layers were washed with H2O
(10 mL), dried (Na2SO4) and the solvent was removed under
reduced pressure. The crude product was purified by column
chromatography (silica gel, pentane/diethyl ether = 100:1) to yield
(3,3-Bis(methoxymethyl)-1λ5-hex-1-en-5-yn-1-ylidene)cyclohex-
ane (1f). 1H NMR (400 MHz, CDCl3)  = 5.00 (quint, J = 2.1 Hz,
1H), 3.34 (d, J = 2.9 Hz, 4H), 3.33 (s, 6H), 2.34 (d, J = 2.7 Hz,
2H), 2.19-2.05 (m, 4H), 1.94 (t, J = 2.7 Hz, 1H), 1.42-1.67 (m,
6H); 13C{1H} NMR (100 MHz, CDCl3)  = 198.0, 104.7, 90.5,
81.5, 75.5, 69.8, 59.4, 43.2, 31.5, 27.3, 26.1, 23.4; HRMS (ESI)
m/z: [M + Na]+ Calcd for C16H24O2Na: 271.1669; Found:
271.1670. Isolated yield: 95% (209 mg), as a colorless oil. Flash
column chromatography (silica gel, pentane/ethyl acetate = 98:2).
1
1j (221 mg, 79% yield) as a liquid; H NMR (400 MHz, CDCl3):
4,4-Bis(methoxymethyl)-7,8,8-trimethyl-6λ5-nona-5,6-dien-1-yne
 = 7.34-7.26 (m, 10H), 5.12 (sept, J = 2.9 Hz, 1H), 4.54 (s, 4H),
3.53 (s, 4H), 2.45 (d, J = 2.7 Hz, 2H), 1.95 (t, J = 2.7 Hz, 1H),
1.70 (d, J = 2.9 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3):  =
201.5, 138.7, 128.2, 127.3, 97.4, 90.9, 81.7, 73.3, 73.1, 69.8, 43.8,
23.5, 20.5; HRMS (ESI) m/z: [M + Na]+ Calcd for C25H28O2Na:
383.1982; Found: 383.1987.
1
(1g). H NMR (400 MHz, CDCl3)  = 5.08 (q, J = 2.9 Hz, 1H),
3.36-3.29 (m, 10H), 2.32 (d, J = 2.6 Hz, 2H), 1.94 (t, J = 2.6 Hz,
1H), 1.68 (d, J = 2.7 Hz, 3H) 1.04 (s, 9H); 113C{1H} NMR (100
MHz, CDCl3)  = 199.7, 110.7, 92.5, 81.7, 75.5, 69.9, 59.3, 43.3,
33.1, 29.0, 23.3, 15.2; HRMS (ESI) m/z: [M + Na]+ Calcd for
C16H26O2Na: 273.1825; Found: 273.1829. Isolated yield: 85%
(189 mg), as a colerless oil. Flash column chromatography (silica
gel, pentane/ethyl acetate = 98:2).
Method A: Non-aerobic Oxidative Coupling-Carbocyclization
for Preparation of 3
Representative Procedure: Synthesis of 3a. In a sealable
microwave tube were placed 1a (47.2 mg, 0.2 mmol), Pd(OAc)2
(2.2 mg, 0.01 mmol), 1,4-benzoquinone (BQ) (43.2 mg, 0.4
mmol), anhydrous Na2CO3 (4.2 mg, 0.04 mmol) and 2a (77 mg,
0.4 mmol). To this mixture, 2.0 mL of anhydrous CH3CN solvent
was added and the tube was sealed with the cap. The reaction was
Representative Procedure for the Synthesis of 1h and 1i:
Synthesis of 1h. To a suspension of 1ax (108 mg, 0.60 mmol) in
acetone (5 mL) was added 2,2-dimethoxypropane (72 mg, 0.69
mmol) and p-TsOH·H2O (5.7 mg, 0.03 mmol). The reaction
mixture was stirred at room temperature for 3 h and quenched
with sat. NaHCO3 (aq.). Acetone was evaporated and the residue
was extracted with Et2O (2 x 20 mL). The combined organic
layers were washed with brine (20 mL), dried (Na2SO4) and the
solvent was removed under reduced pressure. The crude product
was purified by flash column chromatography (silica gel,
pentane/ethyl acetate = 97:3) to yield 1h (111 mg, 84% yield) as a
colorless oil.
o
stirred at 80 C in an oil bath for 24 h. After full consumption of
starting material 1a as monitored by TLC, the reaction mixture
was concentrated in vacuo and purified via short column
chromatography on silica gel (eluent: ethyl acetate/pentane, 5:95)
affording 77 mg (90%) of 3a as a liquid. The reaction was also
run on a 1.3 mmol scale using 1a (0,307 g, 1,3 mmol), which
afforded 0.45g (81%) of 3a after short column chromatography on
silica gel (eluent: ethyl acetate/pentane, 5:95).
In the same manner 1i was obtained from 1dx.
Method B: Aerobic Oxidative Coupling-Carbocyclization for
Preparation of 3.
Characterization of Products 1h and 1i.
Representative Procedure: Synthesis of 3a. In a sealable
microwave tube were placed 1a (47.2 mg, 0.2 mmol), Pd(OAc)2
(2.2 mg, 0.01 mmol), Cobalt(salophen) (3.7 mg, 0.01 mmol), 20
mol% of 1,4-benzoquinone (BQ) (4.4 mg, 0.04 mmol), anhydrous
Na2CO3 (4.2 mg, 0.04 mmol) and 2a (77 mg, 0.4 mmol). The tube
was sealed with the cap. To this mixture was added 2.0 mL of
anhydrous CH3CN via syringe. Then the reaction was stirred at 80
oC in an oil bath under an oxygen atmosphere using molecular
2,2-Dimethyl-5-(3-methyl-2λ5-buta-1,2-dien-1-yl)-5-(prop-2-yn-1-
1
yl)-1,3-dioxane (1h). H NMR (400 MHz, CDCl3)  = 4.88 (sept,
J = 2.9 Hz, 1H), 3.70 (qt, J = 14.5 Hz, J = 11.6 Hz, 4H), 2.53 (d, J
= 2.6 Hz, 2H), 1.99 (t, J = 2.7 Hz, 1H), 1.40 (d, J = 3.0 Hz, 6H),
1.39 (d, J = 8.1 Hz, 6H); 13C{1H} NMR (100 MHz, CDCl3)  =
201.7, 98.2, 97.9, 89.9, 81.4, 70.4, 66.9, 36.9, 27.6, 23.8, 20.5,
19.8; HRMS (ESI) m/z: [M + Na]+ Calcd for C14H20NaO2:
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The Journal of Organic Chemistry
oxygen balloon connected via a needle for 24 h. After full
Isolated yield: method A-82% (78 mg), method B-78% (74 mg),
1
2
3
4
5
6
consumption of starting material 1a as monitored by TLC, the
reaction mixture was concentrated in vacuo and purified via short
column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95) afforded 73 mg (85%) of 3a as a liquid.
as a liquid. Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95).
Ethyl-(Z)-3-allyl-4-((Z)-(4,4-bis(methoxymethyl)-2-(prop-1-en-2-y
l)cyclopent-2-en-1-ylidene)methyl)-5-methylhexa-3,5-dienoate
1
Characterization of Products 3.
(3e). H NMR (400 MHz, CDCl3)  = 6.18 (s, 1H), 5.85 (s, 1H),
5.78-5.66 (m, 1H), 5.09 (s, 1H), 5.05-4.98 (m, 4H), 4.82 (s, 1H),
4.11 (q, J = 7.1 Hz, 2H), 3.31 (s, 6H), 3.26 (s, 4H), 3.19 (s, 2H),
2.94 (d, J = 6.4 Hz, 2H), 2.43 (d, J = 2.1 Hz, 2H), 1.91 (s, 3H),
1.79 (s, 3H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz,
CDCl3)  = 172.2, 148.8, 145.0, 144.6, 140.6, 138.9, 136.1, 135.3,
127.2, 118.1, 115.8, 115.3, 115.0, 60.3, 59.3, 52.2, 38.0, 36.9,
36.4, 23.3, 23.2, 14.1; HRMS (ESI) m/z: [M + Na]+ Calcd for
C25H36O4Na: 423.2506; Found: 423.2494. Isolated yield: method
A-80% (64 mg), as a liquid. Column chromatography on silica gel
(eluent: ethyl acetate/pentane, 4:96).
Dimethyl-(Z)-4-((Z)-3-(2-ethoxy-2-oxoethyl)-2-(prop-1-en-2-yl)he
xa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-dic
arboxylate (3a). H NMR (400 MHz, CDCl3)  = 6.24 (s, 1H),
7
8
9
1
5.94 (s, 1H), 5.76-5.66 (m, 1H), 5.15 (s, 1H), 5.10 (s, 1H), 5.06 (s,
1H), 5.02 (d, J = 4.9 Hz, 1H), 4.98 (s, 1H), 4.85 (d, J = 1.2 Hz,
1H), 4.09 (q, J = 7.1 Hz, 2H), 3.71 (s, 6H), 3.19 (d, J = 4.0 Hz,
4H), 2.93 (d, J = 6.4 Hz, 2H), 1.92 (s, 3H), 1.81 (s, 3H), 1.22 (t, J
= 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3)  = 171.9, 170.9,
151.1, 144.2, 142.3, 139.9, 138.0, 135.0, 128.8, 119.5, 116.3,
116.0, 115.9, 63.8, 60.4, 52.7, 38.1, 36.9, 36.7, 23.2, 23.0, 14.1;
HRMS (ESI) m/z: [M + Na]+ Calcd for C25H32O6Na: 451.2091;
Found: 451.2069. Isolated yield: method A-90% (77 mg), method
B-85% (73 mg), as a liquid. Column chromatography on silica gel
(eluent: ethyl acetate/pentane, 5:95).
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Ethyl-(Z)-3-allyl-4-((Z)-(2-(cyclohex-1-en-1-yl)-4,4-bis(methoxym
ethyl)cyclopent-2-en-1-ylidene)methyl)-5-methylhexa-3,5-dienoat
e (3f). 1H NMR (400 MHz, CDCl3)  = 6.14 (s, 1H), 5.83-5.68 (m,
3H), 5.06-4.98 (m, 3H), 4.81 (dd, J = 2.4 Hz, 0.9 Hz, 1H), 4.10 (q,
J = 7.1 Hz, 2H), 3.31 (s, 6H), 3.26 (s, 4H), 3.19 (s, 2H), 2.94 (d, J
= 6.4 Hz, 2H), 2.40 (d, J = 2.1 Hz, 2H), 2.16-2.07 (m, 4H), 1.79 (s,
3H), 1.71-1.57 (m, 4H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR
(100 MHz, CDCl3)  = 172.2, 149.8, 145.5, 144.7, 140.8, 135.3,
134.5, 132.1, 126.9, 126.9, 117.7, 115.8, 115.2, 60.3, 59.3, 52.1,
38.1, 36.9, 36.4, 28.7, 25.3, 23.2, 22.9, 22.2, 14.1; HRMS (ESI)
m/z: [M + Na]+ Calcd for C28H40O4Na: 463.2819; Found:
463.2825. Isolated yield: method A-77% (68 mg), as a liquid.
Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95).
Diethyl-(Z)-4-((Z)-3-(2-ethoxy-2-oxoethyl)-2-(prop-1-en-2-yl)hex
a-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-dica
rboxylate (3b). 1H NMR (400 MHz, CDCl3)  = 6.24 (s, 1H), 5.95
(s, 1H), 5.76-5.66 (m, 1H), 5.15 (s, 1H), 5.10 (s, 1H), 5.06 (s, 1H),
5.02 (d, J = 6.6 Hz, 1H), 4.98 (s, 1H), 4.86 (s, 1H), 4.22-4.04 (m,
6H), 3.19 (s, 4H), 2.94 (d, J = 6.1 Hz, 2H), 1.93 (s, 3H), 1.82 (s,
3H), 1.23 (t, J = 7.1 Hz, 9H); 13C{1H} NMR (100 MHz, CDCl3) 
= 171.9, 170.5, 151.1, 144.3, 142.6, 140.0, 138.1, 135.0, 129.2,
128.7, 119.4, 116.1, 115.9, 115.8, 64.0, 61.5, 60.4, 38.2, 36.8,
36.7, 23.2, 23.1, 14.1, 13.9; HRMS (ESI) m/z: [M + Na]+ Calcd
for C27H36O6Na: 479.2404; Found: 479.2382. Isolated yield:
method A-89% (82 mg), as a liquid. Column chromatography on
silica gel (eluent: ethyl acetate/pentane, 5:95).
Ethyl-(Z)-3-allyl-4-((Z)-(2-(3,3-dimethylbut-1-en-2-yl)-4,4-bis(me
thoxymethyl)cyclopent-2-en-1-ylidene)methyl)-5-methylhexa-3,5-d
ienoate (3g). 1H NMR (400 MHz, CDCl3)  = 5.97 (s, 1H),
5.76-5.68 (m, 1H), 5.66 (s, 1H), 5.20 (d, J = 1.7 Hz, 1H),
5.07-4.97 (m, 3H), 4.82 (dd, J = 2.4 Hz, 0.9 Hz, 1H), 4.69 (d, J =
1.7 Hz, 1H), 4.11 (q, J = 7.1 Hz, 2H), 3.32 (s, 6H), 3.28 (s, 4H),
3.18 (s, 2H), 2.91 (d, J = 6.4 Hz, 2H), 2.39 (d, J = 2.3 Hz, 2H),
1.76 (s, 3H), 1.24 (t, J = 7.1 Hz, 3H), 1.06 (s, 9H); 13C{1H} NMR
(100 MHz, CDCl3)  = 172.3, 152.7, 148.7, 148.5, 144.4, 140.7,
136.5, 135.2, 127.1, 117.8, 115.6, 115.5, 112.2, 60.3, 59.3, 52.8,
38.1, 36.8, 35.8, 35.2, 29.5, 23.3, 14.1; HRMS (ESI) m/z: [M +
Na]+ Calcd for C28H42O4Na: 465.2975; Found: 465.2985. Isolated
Dimethyl-(Z)-3-(cyclohex-1-en-1-yl)-4-((Z)-3-(2-ethoxy-2-oxoethy
l)-2-(prop-1-en-2-yl)hexa-2,5-dien-1-ylidene)cyclopent-2-ene-1,1-
dicarboxylate (3c). 1H NMR (400 MHz, CDCl3)  = 6.21 (s, 1H),
5.86 (s, 1H), 5.82-5.80 (m, 1H), 5.78-5.68 (m, 1H), 5.11-5.09 (m,
1H), 5.04-5.02 (m, 1H), 4.99 (s, 1H), 4.85 (d, J = 1.2 Hz, 1H),
4.09 (q, J = 7.1 Hz, 2H), 3.71 (s, 6H), 3.20 (s, 2H), 3.18 (d, J =
2.2 Hz, 2H), 2.94 (d, J = 6.4 Hz, 2H), 2.14-2.10 (m, 4H), 1.82 (s,
3H), 1.72-1.56 (m, 4H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR
(100 MHz, CDCl3)  = 172.0, 171.2, 152.0, 144.2, 142.8, 140.2,
135.0, 131.4, 128.5, 128.1, 127.5, 119.2, 115.9, 115.8, 63.8, 60.4,
52.7, 38.2, 36.9, 36.8, 28.6, 25.3, 23.3, 22.7, 22.0, 14.1; HRMS
(ESI) m/z: [M + Na]+ Calcd for C28H36O6Na: 491.2404; Found:
491.2392. Isolated yield: method A-83% (77 mg), as a liquid.
Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95).
yield: method A-81% (71 mg), as
a
liquid. Column
chromatography on silica gel (eluent: ethyl acetate/pentane, 4:96).
Ethyl-(Z)-3-allyl-4-((Z)-(8,8-dimethyl-3-(prop-1-en-2-yl)-7,9-diox
aspiro[4.5]dec-3-en-2-ylidene)methyl)-5-methylhexa-3,5-dienoate
1
(3h). H NMR (400 MHz, CDCl3)  = 6.21 (s, 1H), 5.96 (s, 1H),
5.77-5.66 (m, 1H), 5.11 (s, 1H), 5.07 (s, 1H), 5.04-4.99 (m, 3H),
4.84 (d, J = 1.3 Hz, 1H), 4.11 (q, J = 7.1 Hz, 2H), 3.69 (d, J =
11.3 Hz, 2H), 3.59 (d, J = 11.3 Hz, 2H), 3.20 (s, 2H), 2.93 (d, J =
6.4 Hz, 2H), 2.49 (d, J = 2.2 Hz, 2H), 1.92 (s, 3H), 1.79 (s, 3H),
1.43 (d, J = 5.8 Hz, 6H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR
(100 MHz, CDCl3)  = 172.1, 149.1, 144.5, 144.1, 140.4, 138.8,
135.2, 135.1, 127.8, 118.6, 115.9, 115.6, 115.2, 97.5, 68.4, 60.4,
46.5, 38.1, 37.5, 36.8, 24.0, 23.5, 23.3, 23.3, 14.1; HRMS (ESI)
m/z: [M + Na]+ Calcd for C26H36O4Na: 435.2506; Found:
435.2497. Isolated yield: method A-75% (62 mg), as a liquid.
Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95).
Dimethyl-(Z)-3-(3,3-dimethylbut-1-en-2-yl)-4-((Z)-3-(2-ethoxy-2-
oxoethyl)-2-(prop-1-en-2-yl)hexa-2,5-dien-1-ylidene)cyclopent-2-
ene-1,1-dicarboxylate (3d). 1H NMR (400 MHz, CDCl3)  = 6.07
(s, 1H), 5.80 (s, 1H), 5.76-5.63 (m, 1H), 5.25 (d, J = 1.4 Hz, 1H),
5.11 (s, 1H), 5.02-4.97 (m, 2H), 4.87-4.86 (m, 1H), 4.74 (d, J =
1.4 Hz, 1H), 4.09 (q, J = 7.1 Hz, 2H), 3.73 (s, 6H), 3.19 (s, 2H),
3.17 (d, J = 2.2 Hz, 2H), 2.91 (d, J = 6.4 Hz, 2H), 1.79 (s, 3H),
1.23 (t, J = 7.1 Hz, 3H), 1.06 (s, 9H); 13C{1H} NMR (100 MHz,
CDCl3)  = 172.0, 171.2, 152.0, 144.3, 142.8, 140.1, 135.0, 131.4,
128.5, 128.1, 127.5, 119.2, 115.9, 115.8, 63.8, 60.4, 52.7, 38.2,
36.9, 36.8, 28.7, 25.3, 23.3, 22.7, 22.0, 14.1; HRMS (ESI) m/z:
[M + Na]+ Calcd for C28H38O6Na: 493.2561; Found: 493.2573.
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Ethyl-(Z)-3-allyl-4-((Z)-(3-(3,3-dimethylbut-1-en-2-yl)-8,8-dimeth
Hz, 2H), 3.73 (s, 6H), 3.22 (d, J = 2.2 Hz, 2H), 3.17 (s, 2H), 2.94
1
2
3
4
5
6
7
8
yl-7,9-dioxaspiro[4.5]dec-3-en-2-ylidene)methyl)-5-methylhexa-3,
5-dienoate (3i). H NMR (400 MHz, CDCl3)  = 6.00 (s, 1H),
(d, J = 6.1 Hz, 2H), 2.11-2.09 (m, 2H), 1.98-1.93 (m, 5H),
1.60-1.70 (m, 4H), 1.23 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100
MHz, CDCl3)  = 172.2, 171.1, 151.4, 141.9, 140.5, 138.1, 137.1,
135.2, 129.1, 128.5, 126.9, 120.1, 116.2, 115.8, 63.9, 60.4, 52.8,
38.3, 37.0, 36.8, 28.9, 25.3, 23.1, 22.7, 21.9, 14.1; HRMS (ESI)
m/z: [M + Na]+ Calcd for C28H36O6Na: 491.2404; Found:
491.2421. Isolated yield: method A-78% (74 mg), method B-80%
(76 mg), as a liquid. Column chromatography on silica gel (eluent:
ethyl acetate/pentane, 5:95).
1
5.77 (s, 1H), 5.77-5.66 (m, 1H), 5.21 (s, 1H), 5.09 (s, 1H), 5.02 (d,
J = 6.8 Hz, 1H), 4.97 (s, 1H), 4.85 (s, 1H), 4.69 (d, J = 1.5 Hz,
1H), 4.11 (q, J = 7.1 Hz, 2H), 3.72 (d, J = 11.3 Hz, 2H), 3.60 (d, J
= 11.3 Hz, 2H), 3.19 (s, 2H), 2.91 (d, J = 6.4 Hz, 2H), 2.48 (d, J =
2.2 Hz, 2H), 1.77 (s, 3H), 1.43 (d, J = 4.3 Hz, 6H), 1.25 (t, J = 7.1
Hz, 3H), 1.06 (s, 9H); 13C{1H} NMR (100 MHz, CDCl3)  =
172.3, 152.5, 149.1, 147.4, 144.4, 140.5, 135.5, 135.0, 127.7,
118.7, 115.8, 115.7, 112.5, 97.5, 68.6, 60.4, 47.1, 38.2, 36.8, 36.6,
35.7, 29.6, 24.3, 23.4, 23.3, 14.2;; HRMS (ESI) m/z: [M + Na]+
Calcd for C29H42O4Na: 477.2975; Found: 477.2977. Isolated yield:
method A-34% (31 mg), as a liquid. Column chromatography on
silica gel (eluent: ethyl acetate/pentane, 5:95).
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Dimethyl-(Z)-4-((Z)-2-(cyclopent-1-en-1-yl)-3-(2-ethoxy-2-oxoeth
yl)hexa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,
1
1-dicarboxylate (3n). H NMR (400 MHz, CDCl3)  = 6.27 (s,
1H), 5.93 (s, 1H), 5.77-5.67 (m, 1H), 5.58 (s, 1H), 5.15 (s, 1H),
5.07 (s, 1H), 5.03-4.98 (m, 2H), 4.11 (q, J = 7.1 Hz, 2H), 3.72 (s,
6H), 3.17 (s, 2H), 3.09 (d, J = 2.2 Hz, 2H), 2.94 (d, J = 6.1 Hz,
2H), 2.36 (dt, J = 40.2 Hz, 7.1 Hz, 4H), 1.94-1.88 (m, 5H), 1.24 (t,
J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3)  = 172.0,
171.0, 150.8, 142.3, 142.1, 137.9, 135.2, 135.0, 130.0, 129.4,
128.7, 120.2, 116.2, 116.0, 63.7, 60.4, 52.8, 38.3, 37.2, 36.7, 36.2,
32.9, 23.4, 23.0, 14.1; HRMS (ESI) m/z: [M + Na]+ Calcd for
C27H34O6Na: 477.2248; Found: 477.2249. Isolated yield: method
A-75% (69 mg), method B-77% (71 mg), as a liquid. Column
chromatography on silica gel (eluent: ethyl acetate/pentane, 5:95).
Ethyl(Z)-3-allyl-4-((Z)-(4,4-bis((benzyloxy)methyl)-2-(prop-1-en-
2-yl)cyclopent-2-en-1-ylidene)methyl)-5-methylhexa-3,5-dienoate
(3j). 1H NMR (400 MHz, CDCl3)  = 7.34-7.23 (m, 10H), 6.19 (s,
1H), 5.93 (s, 1H), 5.80-5.68 (m, 1H), 5.11-4.99 (m, 5H), 4.84 (s,
1H), 4.51 (s, 4H), 4.10 (q, J = 7.1 Hz, 2H), 3.43 (s, 4H), 3.21 (s,
2H), 2.95 (d, J = 6.4 Hz, 2H), 2.50 (d, J = 2.1 Hz, 2H), 1.93 (s,
3H), 1.79 (s, 3H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100
MHz, CDCl3)  = 172.2, 148.9, 145.2, 144.7, 140.7, 139.0, 138.8,
136.4, 135.3, 128.2, 127.3, 127.3, 127.2, 117.9, 115.8, 115.3,
115.0, 73.5, 73.2, 60.4, 52.4, 38.0, 36.9, 36.6, 23.4, 23.3, 14.1;
HRMS (ESI) m/z: [M + Na]+ Calcd for C37H44O4Na: 575.3132;
Found: 575.3125. Isolated yield: method A-83% (91 mg), as a
liquid. Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 3:97).
Dimethyl-(Z)-4-((Z)-3-(2-ethoxy-2-oxoethyl)-2-vinylhexa-2,5-dien
-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-dicarboxylate
(3o). 1H NMR (400 MHz, CDCl3)  = 6.64 (dd, J = 17.1 Hz, 10.5
Hz, 1H), 6.13 (s, 1H), 6.02 (s, 1H), 5.74-5.63 (m, 1H), 5.20-5.13
(m, 4H), 5.03 (d, J = 6.1 Hz, 1H), 5.00 (s, 1H), 4.13 (q, J = 7.1 Hz,
2H), 3.71 (s, 6H), 3.25 (s, 2H), 2.98-2.96 (m, 4H), 1.98 (s, 3H),
1.25 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100 MHz, CDCl3)  =
171.2, 170.9, 149.1, 144.0, 137.6, 135.2, 134.9, 132.3, 130.4,
129.6, 119.3, 116.8, 116.6, 116.4, 63.3, 60.7, 52.8, 39.3, 37.1,
36.5, 22.9, 14.1; HRMS (ESI) m/z: [M + Na]+ Calcd for
C24H30O6Na: 437.1940; Found: 437.1931. Isolated yield: method
A-61% (50 mg), as a liquid. Column chromatography on silica gel
(eluent: ethyl acetate/pentane, 5:95).
Dimethyl-(Z)-4-((Z)-3-(ethoxycarbonyl)-2-(prop-1-en-2-yl)hexa-2,
5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-dicarbox
1
ylate (3k). H NMR (400 MHz, CDCl3)  = 6.19 (t, J = 2.2 Hz,
1H), 6.03 (s, 1H), 5.82-5.72 (m, 1H), 5.19 (s, 1H), 5.07-4.99 (m,
3H), 4.95 (s, 1H), 4.87 (d, J = 0.8 Hz, 1H), 4.11 (q, J = 7.1 Hz,
2H), 3.73 (s, 6H), 3.22 (d, J = 2.2 Hz, 2H), 3.07 (d, J = 6.1 Hz,
2H), 1.93 (d, J = 4.0 Hz, 6H), 1.23 (t, J = 7.1 Hz, 3H); 13C{1H}
NMR (100 MHz, CDCl3)  = 172.7, 169.9, 150.9, 145.8, 145.6,
144.7, 137.6, 134.2, 130.5, 129.8, 118.3, 116.6, 116.0, 115.2, 63.9,
60.3, 52.9, 37.0, 34.4, 23.0, 22.7, 13.8; HRMS (ESI) m/z: [M +
Na]+ Calcd for C24H30O6Na: 437.1940; Found: 437.1950. Isolated
yield: method A-85% (70 mg), method B-87% (72 mg), as a
liquid. Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95).
Dimethyl-(Z)-4-((2Z,5E)-3-(ethoxycarbonyl)-2-(prop-1-en-2-yl)-
octa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-di
1
carboxylate (3p). H NMR (400 MHz, CDCl3)  = 6.21(t, J = 7.1
Hz, 2H), 6.03 (s, 1H), 5.52-5.45 (m, 1H), 5.37-5.30 (m, 1H), 5.19
(pent, J = 1.4 Hz, 1H), 5.07 (s, 1H), 4.95 (pent, J = 1.6 Hz, 1H),
4.87 (dd, J = 1.0 Hz, 1.9 Hz, 1H), 4.11 (q, J = 7.1 Hz, 2H), 3.73 (s,
6H), 3.22 (d, J = 2.2 Hz, 2H), 3.01 (d, J = 6.1 Hz, 2H), 1.95-1.93
(m, 8H), 1.23 (t, J = 7.1 Hz, 3H), 0.93 (t, J = 7.4 Hz, 3H); 13C{1H}
NMR (100 MHz, CDCl3)  = 170.7, 170.1, 151.0, 145.7, 145.5,
143.7, 137.7, 134.0, 130.9, 130.3, 124.4, 118.5, 116.6, 115.2, 64.0,
60.3, 52.9, 37.0, 33.4, 25.5, 23.0, 22.7, 13.9, 13.7; HRMS (ESI)
m/z: [M + Na]+ Calcd for C26H34O6Na: 465.2248; Found:
465.2239. Isolated yield: method A-76% (67 mg), as a liquid.
Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 7:93).
Dimethyl-(Z)-4-((Z)-3-(2-ethoxy-2-oxoethyl)-2-(prop-1-en-2-yl-d5)h
exa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-di
1
carboxylate (3l). H NMR (400 MHz, CDCl3)  = 6.26 (s, 1H),
5.95 (s, 1H), 5.73-5.69 (m, 1H), 5.16 (s, 1H), 5.07-4.99 (m, 3H),
4.11 (q, J = 7.0 Hz, 2H), 3.72 (s, 6H), 3.20 (s, 4H), 2.95 (d, J =
5.7 Hz, 2H), 1.94 (s, 3H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR
(100 MHz, CDCl3)  = 172.0, 171.0, 151.2, 144.0, 142.3, 139.9,
138.0, 135.0, 128.9, 128.8, 119.6, 116.3, 116.0, 63.9, 60.4, 52.8,
38.2, 36.9, 36.8, 23.1, 14.1; HRMS (ESI) m/z: [M + Na]+ Calcd
for C25H27D5O6Na: 456.2410; Found: 456.2393. Isolated yield:
method A-72% (62 mg), as a liquid. Column chromatography on
silica gel (eluent: ethyl acetate/pentane, 5:95).
Dimethyl-(Z)-4-((2Z,5E)-3-(ethoxycarbonyl)-6-phenyl-2-(prop-1-e
n-2-yl)hexa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-en
e-1,1-dicarboxylate (3q). 1H NMR (400 MHz, CDCl3)  =
7.33-7.18 (m, 5H), 6.40 (d, J = 15.8 Hz, 1H), 6.27 (s, 1H),
6.18-6.10 (m, 1H), 6.05 (s, 1H), 5.22-5.20 (m, 1H), 5.09 (s, 1H),
4.97 (s, 1H), 4.90 (s, 1H), 4.13 (q, J = 7.1 Hz, 2H), 3.72 (s, 6H),
3.26-3.23 (m, 4H), 1.96 (s, 6H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H}
NMR (100 MHz, CDCl3)  = 170.7, 169.9, 150.9, 146.0, 145.6,
Dimethyl-(Z)-4-((Z)-2-(cyclohex-1-en-1-yl)-3-(2-ethoxy-2-oxoethy
l)hexa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-
1
dicarboxylate (3m). H NMR (400 MHz, CDCl3)  = 6.27 (t, J =
2.2 Hz, 1H), 5.92 (s, 1H), 5.77-5.67 (m, 1H), 5.55 (sept, J = 2.2
Hz, 1H), 5.16-5.15 (m, 1H), 5.06-4.98 (m, 3H), 4.11 (q, J = 7.1
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The Journal of Organic Chemistry
144.9, 137.7, 137.4, 131.3, 130.6, 129.8, 128.4, 127.0, 126.2,
mg), as a liquid. Column chromatography on silica gel (eluent:
1
2
3
4
126.1, 118.4, 116.7, 115.2, 64.0, 60.4, 52.9, 37.1, 33.8, 23.1, 22.7,
13.8; HRMS (ESI) m/z: [M + Na]+ Calcd for C30H34O6Na:
513.2253; Found: 513.2260. Isolated yield: method A-57% (56
mg), as a liquid. Column chromatography on silica gel (eluent:
ethyl acetate/pentane, 5:95).
ethyl acetate/pentane, 3:97).
Dimethy-(Z)-4-((Z)-3-(2-hydroxyethyl)-2-(prop-1-en-2-yl)hexa-2,
5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-dicarbox
1
5
ylate (3v). H NMR (400 MHz, CDCl3)  = 6.27 (s, 1H), 5.93 (s,
1H), 5.81-5.71 (m, 1H), 5.17 (s, 1H), 5.13 (s, 1H), 5.06-5.01 (m,
3H), 4.84 (s, 1H), 4.45 (s, 1H), 3.73 (s, 6H), 3.67 (q, J = 7.1 Hz,
2H), 3.22 (d, J = 2.1 Hz, 2H), 2.91 (d, J = 6.1 Hz, 2H), 2.46 (t, J =
7.1 Hz, 2H), 1.94 (s, 3H), 1.86 (s, 3H); 13C{1H} NMR (100 MHz,
CDCl3)  = 171.1, 151.6, 149.4, 144.5, 141.3, 139.4, 138.1, 135.8,
132.6, 128.4, 119.9, 116.3, 116.1, 115.8, 115.6, 63.9, 61.8, 52.9,
36.9, 36.6, 36.2, 24.0, 23.2; HRMS (ESI) m/z: [M + Na]+ Calcd
for C23H30O5Na: 409.1985; Found: 409.1986. Isolated yield:
method A-63% (49 mg), as a liquid. Column chromatography on
silica gel (eluent: ethyl acetate/pentane, 10:90).
6
7
8
9
Dimethyl-(Z)-4-((Z)-3-(ethoxycarbonyl)-6-methyl-2-(prop-1-en-2-
yl)hepta-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,
1-dicarboxylate (3r). 1H NMR (400 MHz, CDCl3)  = 6.20 (t, J =
2.2 Hz, 1H), 6.02 (s, 1H), 5.19-5.17 (m, 1H), 5.07-5.04 (m, 2H),
4.93 (s, 1H), 4.86 (s, 1H), 4.10 (q, J = 7.1 Hz, 2H), 3.73 (s, 6H),
3.21 (d, J = 2.2 Hz, 2H), 3.01 (d, J = 6.9 Hz, 2H), 1.92 (d, J =
12.5 Hz, 6H), 1.66 (s, 3H), 1.60 (s, 3H), 1.23 (t, J = 7.1 Hz, 3H);
13C{1H} NMR (100 MHz, CDCl3)  = 170.7, 170.2, 150.9, 145.7,
145.3, 142.9, 137.7, 133.1, 131.6, 130.2, 120.2, 118.5, 116.6,
115.2, 63.9, 60.2, 52.9, 37.0, 29.4, 25.6, 23.0, 22.6, 17.8, 13.8;
HRMS (ESI) m/z: [M + Na]+ Calcd for C26H34O6Na: 465.2253;
Found: 465.2238. Isolated yield: method A-71% (63 mg), as a
liquid. Column chromatography on silica gel (eluent: ethyl
acetate/pentane, 5:95).
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ASSOCIATED CONTENT
Supporting Information
General preparation of starting materials, selected optimization
results, comparative experiments, mechanistic study, kinetic
isotope effect (KIE) experiments and compounds 1H/13C NMR
spectra. This material is available free of charge via the Internet at
http://pubs.acs.org.
Dimethyl-(Z)-4-((Z)-3-(2-ethoxy-2-oxoethyl)-5-methyl-2-(prop-1-e
n-2-yl)hexa-2,5-dien-1-ylidene)-3-(prop-1-en-2-yl)cyclopent-2-en
e-1,1-dicarboxylate (3s). 1H NMR (400 MHz, CDCl3)  = 6.26 (s,
1H), 5.94 (s, 1H), 5.16-5.12 (m, 2H), 5.06 (s, 1H), 4.87 (s, 1H),
4.76 (s, 1H), 4.66 (s, 1H), 4.10 (q, J = 7.1 Hz, 2H), 3.72 (s, 6H),
3.21 (d, J = 2.1 Hz, 2H), 3.19 (s, 2H), 2.90 (s, 2H), 1.93 (s, 3H),
1.84 (s, 3H), 1.65 (s, 3H), 1.24 (t, J = 7.1 Hz, 3H); 13C{1H} NMR
(100 MHz, CDCl3)  = 172.0, 171.0, 151.2, 144.4, 142.7, 142.2,
140.6, 138.0, 129.0, 128.7, 119.8, 116.2, 115.9, 111.7, 63.9, 60.4,
52.8, 40.4, 38.0, 36.9, 23.3, 23.1, 22.3, 14.1; HRMS (ESI) m/z:
[M + Na]+ Calcd for C26H34O6Na: 465.2248; Found: 465.2240.
Isolated yield: method A-80% (71 mg), as a liquid. Column
chromatography on silica gel (eluent: ethyl acetate/pentane, 5:95).
AUTHOR INFORMATION
Corresponding Authors
*rnchem@gmail.com, *jeb@organ.su.se
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Financial support from the Swedish Research Council
(2016-03897), the European Union, and the Olle Engqvist
Foundation is gratefully acknowledged.
Dimethyl-(Z)-4-((E)-3-allyl-2-(prop-1-en-2-yl)hept-2-en-1-ylide-
ne)-3-(prop-1-en-2-yl)cyclopent-2-ene-1,1-dicarboxylate (3t). 1H
NMR (400 MHz, CDCl3)  = 6.26 (s, 1H), 5.89 (s, 1H), 5.77-5.67
(m, 1H), 5.15 (s, 1H), 5.08 (s, 1H), 5.06 (s, 1H), 5.03-4.96 (m,
2H), 4.80 (s, 1H), 3.72 (s, 6H), 3.21 (d, J = 2.1 Hz, 2H), 2.86 (d, J
= 6.1 Hz, 2H), 2.13-2.09 (m, 2H), 1.93 (s, 3H), 1.84 (s, 3H),
1.36-1.27 (m, 5H), 0.88 (t, J = 7.1 Hz, 3H); 13C{1H} NMR (100
MHz, CDCl3)  = 171.2, 151.7, 144.7, 140.3, 138.2, 137.5, 136.5,
136.1, 127.7, 120.5, 116.2, 115.1, 63.9, 52.8, 36.9, 36.0, 32.9,
31.5, 23.9, 23.2, 23.0, 13.9; HRMS (ESI) m/z: [M + Na]+ Calcd
for C25H34O4Na: 421.2349; Found: 421.2353. Isolated yield:
method A-80% (64 mg), as a liquid. Column chromatography on
silica gel (eluent: ethyl acetate/pentane, 3:97).
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1H NMR (400 MHz, CDCl3)  = 7.27-7.15 (m, 10H), 6.42 (t, J =
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23.1, 22.8; HRMS (ESI) m/z: [M + Na]+ Calcd for C27H30O4Na:
441.2036; Found: 441.2034. Isolated yield: method A-60% (50
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Carbocyclization of Allenynes. Angew. Chem. Int. Ed. 2012, 51,
H.; Fu, X.; Chen, J.; Wang, E.; Liu, Y.; Li, Y. Generation of
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Cárdenas, D. J. Pd-Catalyzed Borylative Cyclization of Allenynes
and Enallenes. Org. Lett. 2009, 11, 4548–4551.
(22) (a) Zhu, C.; Yang, B.; Bäckvall, J.-E. Highly Selective
Cascade C–C Bond Formation via Palladium-Catalyzed Oxidative
Carbonylation–Carbocyclization–Carbonylation–Alkynylation of
Enallenes. J. Am. Chem. Soc. 2015, 137, 11868–11871. b) Zhang,
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Table of Content Graphics
R1 R1
R1 R1
R2
PdII
+
oxidant
Cross-conjugated
polyene
Y
X
R2
Z
Allenyne
Enallene
Cross-conjugated polyene
Oxidant is:
(a) either stoichiometric BQ (p-benzoquinone) or
(b) O2, with catalytic amounts of BQ and Co(salophen)
PdII
X + Y
HQ
BQ
Co(salophen)ox
Co(salophen)
H2O
Pd0
Z
1/2 O2
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