Phosphine catalyzed [3+2] cyclization/Michael addition of allenoate with CS2to form 2-thineyl vinyl sulfide

Article abstract of DOI:10.1039/d0cc05070a

We have developed a DPPE-catalyzed three molecular two component tandem reaction of γ-substituted allenoate and CS2 to construct 2-thineyl vinyl sulfide through phosphine catalyzed [3+2] cyclization followed by Michael addition. The synthetic value of the

Full text of DOI:10.1039/d0cc05070a

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DOI: 10.1039/D0CC05070A
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Phosphine catalyzed [3+2] cyclization/Michael addition of
allenoate with CS2 to form 2-thineyl vinyl sulfide
Weihong Fei, a † Ping Xu, a † Jie Houa and Weijun Yao*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
obstructive
We have developed
a DPPE-catalyzed three molecular two
1)
Virieux's work
O
component tandem reaction of -substituted allenoate and CS2 to
construct 2-thineyl vinyl sulfide through phosphine catalyzed [3+2]
cyclization followed by Michael addition. The synthetic value of
these 2-thineyl vinyl sulfide was demonstrated by a concise
synthesis of an anti-glaucoma agent.
R2
O
R2
Ph
+
PPh3 (0.1-1.0 equiv.)
CH2Cl2, N2
N
C S
NHPh
R1
S
R1
low yield
Me
2) Shi's work
Me
CO2R1
During the past two decades, nucleophilic phosphine catalysis 1
has grown into a powerful synthetic tool for the construction
of functionalized cyclic compounds. Since the pioneer work of
H
Me
N
R2
N
S
CO2R1
PPh2Me (2.0 equiv.)
THF, 60 oC, 40h
R2
+
C S
+
PPh2CH2CO2R1
2
Lu et al , who reported the first phosphine catalyzed [3+2]
3) This work
CO2R1
cyclization of allenoate with electron-deficient olefins to
construct cyclopentene derivatives in 1995, a variety of
R2
CO2R1
+
S
CO2R1
CO2R1
DPPE (10 mol%)
CS2, rt
3
S
annulations involving electron-deficient allenes and suitable
+
C
S
electrophiles catalyzed by tertiary phosphines were developed
to form various carbocycles 4, nitrogen-containing heterocycles
5 and oxygen heterocycles 6 through [3 + 2], [4 + 2], [4 + 1], and
other annulations. However, as an important member of
heterocyclic compounds, sulfur heterocycles were seldom
S
R2
R2
R2
2 C-S bonds, 1 C=C bond, one ring
highly E selective
Scheme 1 Thiophene synthesis involving phosphine catalyzed
or mediated Cycizations.
7
explored in this methodology. In 2006, Virieux et al reported
a PPh3-catalyzed [3 + 2] cycloaddition of electron-deficient
allenes with phenyl isothiocyanate to form 2-aminothiophenes
11
12
8
pulmonary disease; P22077 and CCT365623 is a potential
chemotherapeutic agent in cancer therapy, MK0507
(Dorzolamide hydrochloride)
which is carbonic
bis(arylthio)oligothiophenes
in low yield (Scheme 1, eq. 1). Later, Shi et al discovered a
PPh2Me-mediated tandem reaction of 2-alkyl-2,3-
13
is an anti-glaucoma agent,
inhibitor, and
shows good electronic
butadienoates with isothiocyanates to synthesis 2-
aminothiophenes in moderate yield (Scheme 1, eq. 2). Given
the importance of thiophenes in organic synthesis, there still
remains high demand and changeling for the construction of
thiophenes via cyclization catalyzed by phosphine.
a
anhydrase
14
properties (Figure 1). A considerable number of methods have
been developed to access these functionalized 2-thienyl
sulphides 15. To the best of our knowledge, there is currently
no report on the construction of a thiophene ring and sulfide
C−S bonds in one pot catalyzed by organocatalyst. Herein, we
document a novel tandem process to construct 2-thienyl vinyl
sulfide through phosphine catalyzed [3+2] cyclizations of -
substituted allenoate with CS2 16, followed by Michael addition
17 (Scheme 1, eq. 3)
Initially, we choose benzyl penta-2,3-dienoate 1a as model
substrate to explore the feasibility of the reaction catalyzed by
common Lewis bases in CS2 at room temperature.
Unfortunately, no reaction took place when PPh3, DABCO,
2-thienyl sulphides 9 represent an important structural motif
featured in pharmaceutical compounds and functional
10
materials. For example, AZD4407
is a 5-lipoxygenase
inhibitor and is effective for treating asthma and chronic
a. Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou, 310018, P.R.
China. E-mail: Orgywj@zstu.edu.cn.
† The authors contribute equally to this work.
Electronic Supplementary Information (ESI) available: Experimental procedures,
analytical data and NMR spectra. CCDC 2018743 (4a) compound for X-ray data.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/
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Journal Name
R1
O2N
S
Me
View Article Online
NHEt HCl
O
Me
2
DOI: 10.1039/D0CC05070A
CO2R
S
R1
N
O
S
DPPE 10 mol%
CS2, rt
F
CO2R2
SO2NH2
•
S
O
CO2R2
Me
S
OH
S
R1
1
O
O
2
S
S
R1 = alkyl, H; R2 = Et, Bn
MK0507
F
P22077
AZD4407
Me
n-Pr
CO2Bn
CO2Bn
i-Pr
CO2Bn
CO2Bn
Et
O
O
O
S
CO2Bn
S
O
O
S
S
CO2Bn
CO2Bn
S
S
O
S
S
Me
S
CO2Bn
S
S
S
H2N
S
S
n
Me
2a
n-Pr
i-Pr
Et
2c
, 64% yield
E/Z > 19:1
, 71% yield
E/Z > 19:1
2d
2b
, 79% yield
E/Z =10:1
, 73% yield
E/Z > 19:1
C6H13
CO2Bn
CO2Bn
t-Bu
n-Bu
CO2Bn
CO2Bn
i-Bu
bis(arylthio)oligothiophenes
CCT365623
CO2Bn
CO2Bn
S
S
S
CO2Bn
CO2Bn
S
S
S
S
S
Figure 1 Representative examples of 2-thienyl sulfides used in
pharmaceuticals and functional materials.
C6H13
2h
t-Bu
n-Bu
2e
i-Bu
2g,
80% yield
E/Z > 19:1
2f
, 50% yield
E/Z > 19:1
, 74% yield
E/Z > 19:1
, 58% yield
E/Z > 19:1
R
Cy
C5H9
CO2Bn
CO2Bn
DMAP was used. In the presence of Ph2PMe as catalyst, 2-
thienyl vinyl sulfide 2a could be isolated in 35% yield with 5:1
E/Z ratio. Subsequently, a series of common commercial
available phosphines were examined and it revealed that DPPE
was the best choice to offer 2a in 71% yield with more than
19:1 E/Z selectivity. Other conditions with adjustment were
investigated, including addition of MgSO4 to remove water,
EtO2C
CO2Bn
CO2Bn
S
CO2Bn
S
S
CO2Et
S
S
S
CO2Bn
S
R
S
Cy
C5H9
R = CH2CH2Ph
2i
, 73% yield
E/Z > 19:1
2j, 71% yield
E/Z > 19:1
2k,
59% yield
E/Z > 19:1
2l,
53% yield
Scheme 2 Substrate scope of g-alkyl substituted allenoates. a,b
Condition: a. allenoate 1 (0.4 mmol), DPPE (0.04 mmol) in 2 mL CS2 at room
temperature. b. isolated yield.
Table 1 Optimization of the three-component reaction a
Me
COBn
CO2Bn
S
dilution of the system or using mixture solvent, but no better
result was achieved.
Me
cat. 10 mol%
CS2, rt
S
•
CO2Bn
Me
1a
2a
With the optimal condition in hand, we applied this cascade
reaction to other allenoates. As show in Scheme 2, -alkyl
substituted allenoates worked well in this process to provide
the corresponding 2-thienyl vinyl sulfides in moderate to good
yield, not only the linear alkyl groups, but also the branch ones.
Moreover, -cyclopentyl and -cyclohexyl substituted
allenoates could also tolerate in this reaction to afford the
desired product 2i and 2j in 73% and 71% yield, respectively.
Meanwhile, 1k with a remote phenyl group of the long chain
was also employed to give the target product 2k, albeit yield
dropped a little to 59%. Notably, In view of the configuration
of the carbon-carbon double bound of the vinyl sulfides, high
stereoselectivity was detected and more than 19:1 of E/Z ratio
was obtained in most cases except 2d.
Entry
1
Catalyst (x mol%)
PPh3 (20 mol%)
DABCO (20 mol%)
DMAP (20 mol%)
PPh2Me (20 mol%)
PPhMe2(20 mol%)
PMe3 (20 mol%)
P(tBu)3(20 mol%)
DPPB (10 mol%)
DPPE (10 mol%)
DPPP (10 mol%)
DCPE (10 mol%)
DPPE (10 mol%)
DPPE (10 mol%)
DPPE (10 mol%)
DPPE (10 mol%)
Yield b(%)
NR
NR
NR
35
E/Z ratio c
-
2
-
3
-
4
5:1
5:1
-
5
47
6
NR
NR
30
7
-
8
11:1
>19:1
>19:1
-
9
71
10
11
12 d
13 e
14f
53
Encourage by these results, we turn our focus to the -aryl
substituted allenoates to further expand the generality of this
methodology. As show in scheme 3, aryl bearing electron
donating group underwent smoothly in this phosphine
catalyzed [3+2] cyclization, followed by Michael addition to
give the desired products in moderate to good yield with high
stereoselectivity. Aryl with fluorine 3e, a weak electron
NR
62
>19:1
>19:1
>19:1
>19:1
65
67
15g
70
a
Condition: allenoate 1a (0.2 mmol), catalyst (0.02 mmol) in 1 mL CS2 at
room temperature. b. isolated yield; c Determined by crude 1HNMR. d withdrawing group, also served to get the product in 40% yield.
e
f
adding 50 mg anhydrous MgSO4; using 2 mL CS2. 1:1 mixture of toluene
with CS2.
Diazabicyclo[2.2.2]octane; 4-dimethylaminopyridine; DPPE
Bis(diphenylphosphino)ethane; DPPB = 1,4-Bis(diphenylphosphino)butane;
DPPP 1,3-Bis(diphenylphosphino)propane; DCPE 1,2-
Due to the low stability, the allenoate bearing strong electron
withdrawing group was not prepared to be examined. 2-
Naphthyl and biphenyl-containing substrates could also be
used to achieve the 2-thienyl vinyl sulfides 4f, 4g in 54% and 77%
yield, respectively. The configuration of product 4a was
confirmed by X-ray analysis of the crystalstructure.
g
1:1 mixture of CH2Cl2 with CS2. DABCO
=
=
1,4-
1,2-
=
=
bis(dicyclohexylphosphino)ethane.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
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Journal Name
COMMUNICATION
O
Ar
a)
Ph
O
View Article Online
N
DOI: 10.1039/D0CC05070A
Me
CO2Et
CO2Et
S
DPPE 10 mol%
CS2, rt
Ar
CO2Bn
O
N
Ph
+
•
2a
+
•
DPPE 10 mol%
CS2, rt
CO2Bn
S
S
CO2Et
1a
O
56% yield
S
10 equiv.
Ar
3
Me
10
10% yield
4
Me
t-Bu
DPPE
b)
Ph
CO2Et
CO2Et
2a
R3P
S
CO2Et
CO2Et
CO2Et
CO2Et
S
S
1a
CO2Bn
SH
1a
S
S
S
BnO2C
R3P
CO2Bn
S
CO2Bn
R3P
Ph
4a
S
S
Me
O
S
Me
S
Me
, 69% yield
E/Z > 19:1
S
C
t-Bu
Me
Me
D
F
S
4b
, 88% yield
E/Z > 19:1
E
4c,
61% yield
E/Z > 19:1
A
Ph
N
O
OMe
F
PR3
CO2Bn
R3P
Me
CO2Bn
S
CO2Et
CO2Et
S
S
CO2Et
CO2Et
S
CO2Et
CO2Et
S
10
S
S
Me
S
S
S
B
C
MeO
Scheme 5 Control experiment and proposed mechanism.
F
4d
, 41% yield
E/Z = 12:1
4f
, 54% yield
E/Z > 19:1
4e
, 40% yield
E/Z > 19:1
Ph
synthesis of MK0507 (Scheme 4c). The attempt of asymmetric
catalysis hydrogenation of 7 to 8 failed when Noyori catalyst
was employed, so compound 9 was obtained only in racemate.
To further understand the mechanism of this novel
phosphine catalyzed tandem reaction, control experiment was
carried out. 10 equivalent of N-phenyl Maleimide was treated
by DPPE with allonate 1a under standard conditions,
compound 10 was isolated in 10% yield along with product 2a
(scheme 5a). Based on previous studies and results of our
experiments, a plausible mechanism was exhibited in scheme
5b. Firstly, nucleophilic phosphine attacked the activated
allenoate to form zwitterionic intermediate A, followed by the
addition of CS2 to result in intermediate B. After
intramolecular Michael addition of intermediate B,
intermediate C was generated and underwent 1,2-protone
shift to form intermediate D. Subsequently, catalyst was
recycled and compound E was released, which isomerized to
thiophene-2-thiol F. Michael addition took place of F to
another allenoate or N-phenyl Maleimide to provide products
2a or 10. The high E-selectivity of product 2 or 4 was attributed
to the steric hindrance of thiophene-2-thiol F during the
Michael addition of another allenoate.
O
O
O
CO2Et
CO2Et
CO2Et
S
S
S
CO2Et
CO2Et
S
S
CO2Et
S
O
Ph
O
O
4g
, 77% yield
E/Z = 14:1
4h
, 63% yield
E/Z > 19:1
4i
, 51% yield
E/Z > 19:1
Scheme 3 substrate scope of -aryl substituted allenoates a, b
a
Condition:. allenoate 3 (0.4 mmol), DPPE (0.04 mmol) in
2 mL CS2 at room
temperature. b. isolated yield.
What’s more, this DPPE-catalyzed tandem reaction was
easily executed in gram scale for 2l with the yield maintained
(Scheme 4a). In addition, 2l could take place metathesis with
benzyne to form phenyl sulfide 5 (Scheme 4b). Notably, 2l
could underwent Dieckmann condensation in the presence of
LHMDS to provide bicyclic compound 6, followed by oxidation
of sulfide, hydrogenation of alkene and decarboxylation to
afforded keto sulfone 9 18, which is a key intermediate for the
a)
EtO2C
In conclusion,we have developed a novel tandem reaction
involving phosphine catalyzed [3+2] annulation between -
substituted allenoates and CS2, followed by Michael addition
of another molecular of allenoate. A wide variety of alkyl and
aryl substituted allenoates could be employed to deliver 2-
thienyl vinyl sulfide in moderate to good yield with high
stereoselectivity. Furthermore, it was easily converted to anti-
glaucoma agent.
We gratefully acknowledge the National Natural Science
Foundation of China (Grant 21702185), the Natural Science
Foundation of Zhejiang Province (Grant LY20B020012) and the
Science Foundation of Zhejiang Sci-Tech University (Grant
16062189-Y) for the financial support of this work.
CO2Et
DPPE 10 mol%
CS2, rt
•
CO2Et
S
1l
S
2l
2.44g, 21.8 mmol
1.80 g, 55% yield
b)
EtO2C
TMS
CsF(1.2 equiv. )
2l
+
MeCN, 100 oC, 12h
PhS
S
OTf
5
43% yield
O
S
c)
O
EtO2C
EtO2C
mCPBA
CH2Cl2, rt, 1h
LHMDS (1.1 equiv.)
2l
THF, -78 o
C
S
Me
S
Me
S
O
O
6 78% yield
7
91% yield
ref.
O
O
NHCH2CH2 HCl
SO2NH2
EtO2C
LiCl (1.0 equiv.)
DMSO, 100 oC, 6h
Pd/C, H2
MeOH, rt
S
Me
S
S
Me
S
O
O
S
O
O
Me
S
9, 63% yield in two steps
MK-0507
8
Scheme 4 Gram scale synthesis of 2l and its transformations.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
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Journal Name
9
(a) N. Wang, P. Saidhareddy and X. Jiang, Nat. Prod.
Conflicts of interest
There are no conflicts to declare.
View Article Online
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DOI: 10.1039/D0CC05070A
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