Iron(III)-catalyzed dehydration C(sp2)-C(sp2) coupling of tertiary pro-pargyl alcohols and α-oxo ketene dithioacetals: A new route to gem -bis(alkylthio)-substituted vinylallenes

Article abstract of DOI:10.1055/s-0032-1316855

A new and efficient synthetic approach to [gem-bis(alkylthio)vinyl]allenes has been developed involving iron(III)-catalyzed dehydration C(sp ²)-C(sp²) coupling of tertiary propargyl alcohols and α-oxo ketene dithioacetals, affording a variety of [gem-bis(alkylthio) vinyl]allenes in good to excellent yields. Georg Thieme Verlag Stuttgart. New York.

Full text of DOI:10.1055/s-0032-1316855

PAPER
▌609
2
2
paper
Iron(III)-Catalyzed Dehydration C(sp )–C(sp ) Coupling of Tertiary
Propargyl Alcohols and α-Oxo Ketene Dithioacetals: A New Route to
gem-Bis(alkylthio)-Substituted Vinylallenes
A New Route to gem-Bis(alkylthio)-Substituted Vinylallenes
Qian Li,a Yeming Wang,c Zhongxue Fang,b Peiqiu Liao,b Badru-Deen Barry,b Guangbo Che,*a,c Xihe Bi*b,c,d
a
College of Chemistry and Chemical Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, P. R. of China
b
Department of Chemistry, Northeast Normal University, 5268 Renmin Street, 130024 Changchun, P. R. of China
c
Key Laboratory of Preparation and Applications of Environmental Friendly Materials (Jilin Normal University),
Chinese Ministry of Education, Siping 136000, P. R. of China
d
State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. of China
Fax +86(431)85099759; E-mail: bixh507@nenu.edu.cn; E-mail: guangbochejl@yahoo.com
Received: 09.01.2013; Accepted after revision: 23.01.2013
Recently, [gem-bis(alkylthio)vinyl]allenes, with inherent
features of the ketene dithioacetals8 and allenes,9 were ef-
ficiently synthesized by our group. Based on the regula-
tion effect of the alkylthio group, these intrinsic synthetic
synthons have led our team to establish conceptually new
procedures for the divergent synthesis of fully substituted
pyrrole and thiophene heterocycles.10
Abstract: A new and efficient synthetic approach to [gem-bis(al-
kylthio)vinyl]allenes has been developed involving iron(III)-cata-
lyzed dehydration C(sp2)–C(sp2) coupling of tertiary propargyl
alcohols and α-oxo ketene dithioacetals, affording a variety of
[gem-bis(alkylthio)vinyl]allenes in good to excellent yields.
Key words: iron catalysis, tertiary propargyl alcohols, α-oxo ke-
tene dithioacetals, allenic carbocation, [gem-bis(alkylthio)vinyl]al-
lenes
The introduction of two alkylthio groups to the vinylic ter-
minus of vinylallenes has brought unprecedented synthet-
ic utility, however, in this approach, synthesis of the [gem-
bis(alkylthio)vinyl]allenes involved two principal steps:
(1) the Lewis acid catalyzed formation of gem-bis(alkyl-
thio)penten-4-yne derivatives from α-oxo ketene dithio-
acetals and secondary propargyl alcohols;11 and (2)
transformation of these derivatives into [gem-bis(alkyl-
thio)vinyl]allenes through base-promoted propargyl
isomerization (Scheme 1, path A). Even though construc-
tion of these compounds was efficiently accomplished by
this route, the variation of substituents was limited to the
use of secondary propargyl alcohols. As a result, produc-
tion of multifunctional [gem-bis(alkylthio)vinyl]allenes
Vinylallenes have attracted great interest as building
blocks in organic cyclization reactions. Examples include
Diels–Alder reactions,1 [4+1]-cycloaddition reactions,2
thermal electrocyclic reactions,3 [1,5]-H sigmatropic rear-
rangement,4 and several other tautomerization/isomeriza-
tion reactions.5 Although a good number of dynamic
routes to vinylallenes have been developed over the past
few decades,6 efforts toward the discovery of novel and
more efficient synthetic methods, particularly with atten-
tion to the introduction of novel substitution patterns to
modulate the reactivity of vinylallenes, are still ongoing.7
R1
R2
R1
O
R1
O
OH
R4
R5S
•
R2
R4
R5S
base
acid
+
R2
SR5
path A
SR5
O
R2
R5S
R5S
R4
previous work: stepwise
R1
R3
+
HO
H
+
O
R3
FeBr3
FeBr3
R4
•
R2
path B
R1
R2
R2
R1
R5S
SR5 R1
+
R3
•
R3
this work: one step
Scheme 1 Synthetic strategies for [gem-bis(alkylthio)vinyl]allenes
SYNTHESIS 2013, 45, 0609–0614
Advanced online publication: 06.02.2013
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
DOI: 10.1055/s-0032-1316855; Art ID: SS-2012-H0024-OP
© Georg Thieme Verlag Stuttgart · New York

610
Q. Li et al.
PAPER
Table 1 Optimization of the Conditionsa
via a straightforward and step-economic approach still re-
mains a demanding goal in vinylallene chemistry.
O
O
S
Ph
As a continuation of our studies on the exploration of the
potential applicability of vinylallenes in organic synthe-
sis, we sought a more practical protocol to assemble [gem-
bis(alkylthio)vinyl]allenes based upon the synthetic ad-
vantages of the reaction of propargyl tertiary alcohols
with α-oxo ketene dithioacetals as a new approach. Tertia-
ry propargyl alcohols are efficient precursors for allenes
bearing functionalities12 due to the resonance between
propargylic and allenic carbocations.13 The Wang14 and
Chan15 groups and others16 have disclosed the potential
transformation of allenic carbocations into a diverse class
of carbocyclic and heterocyclic compounds via reaction
with suitable nucleophiles under either Lewis acid [such
as BF3·OEt2 and Yb(OTf)3] or Brønsted acid (such as
TfOH and TsOH) catalysis. As part of our efforts to devel-
op non-precious-metal-catalyzed organic transforma-
tions,17 and in continuation of our previously reported
synthesis of gem-bis(alkylthio)penten-4-ynes and their
subsequent synthetic conversion into methyl pent-4-yno-
ates, pyrroles, and thiophenes under varied conditions,10,11
we disclose herein a new and facile iron(III)-catalyzed de-
hydration C(sp2)–C(sp2) coupling reaction route (Scheme
1, path B) of tertiary propargyl alcohols and α-oxo ketene
dithioacetals leading to the synthesis of [gem-bis(alkyl-
thio)vinyl]allenes in a single step.18 This currently rapid
and step-economic procedure is functionally straightfor-
ward and utilizes economically benign, low-cost, and
readily available reagents and catalysts. Under catalysts
by iron(III) salts, tertiary propargyl alcohols reacted expe-
diently with electron-rich α-oxo ketene dithioacetals to
furnish the desired functionalized [gem-bis(alkylthio)vi-
nyl]allenes.
H
S
HO
Ph
•
Ph
[Fe]
r.t.
+
S
S
Ph
1a
2a
3a
Entry
Catalyst
Solvent
Time (min) Yieldb (%)
1
2
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
FeBr3
toluene
MeCN
5
60
85
80
73
trace
0
3
CH2Cl2
1,4-dioxane
DMSO
MeOH
360
360
360
360
5
4
5
6
0
7
toluene
toluene
toluene
toluene
toluene
91
88
0
8
Fe(OTf)3
Fe(acac)3
FeCl2
5
9
360
360
360
10
11
0
Fe
0
a Reaction conditions: 1a (0.55 mmol), 2a (0.5 mmol), [Fe] (20
mol%), solvent (1 mL), r.t.
b Isolated yield.
and 8) whereas those using Fe(acac)3, iron(II) chloride,
and iron failed to initiate any transformation even after
prolonged reaction times (entries 9–11). Thus the best
yields of 3a and shortest reaction times were obtained
with iron(III) chloride, bromide, or triflate as the catalyst
and using nonpolar toluene as the solvent. Of these cata-
lysts, transformation with iron(III) bromide in toluene fur-
nished the best results, thus we selected the conditions in
entry 7 for further use.
In our proposed strategy, tertiary propargyl alcohol 1a and
α-oxo ketene dithioacetal 2a were chosen as model sub-
strates. Investigation of optimal conditions commenced
with the screening for solvent suitability using the reac-
tion of 1a with 2a; the results are summarized in Table 1.
With 20 mol% of either iron(III) chloride, bromide, or tri-
flate catalyst in toluene, transformation to the target 3a
was successfully accomplished in 85%, 91% and 88%
yields, respectively, within five minutes (entries 1, 7, and
8). Although the reaction catalyzed by iron(III) chloride in
both acetonitrile and dichloromethane afforded compara-
bly similar yields of 80% and 73%, respectively, these re-
actions proceeded with much longer reaction times, one
and six hours, respectively (entries 2 and 3). While 1,4-di-
oxane (entry 4) only gave trace amounts of 3a, the reac-
tion did not proceed in solvents like dimethyl sulfoxide
and methanol (entries 5 and 6). The results as outlined in
Table 1 distinctly illustrate the effect that the choice of
solvent has on both the kinetics and yield of 3a. Thus as
toluene has manifestly better solvent activity, it was more
closely scrutinized in the model reaction using different
iron(III) salts. In general, reactions in toluene at room
temperature with iron(III) chloride, bromide, or triflate as
the catalyst promoted the reaction efficiently (entries 1, 7,
With the optimal conditions established, we immediately
explored the scope of our reaction for substrate suitability.
First, functional tertiary propargyl alcohol 1 with varying
substituents (R1 = Et, Ph, Me and R2 = Ph, 2-ClC6H4, 3-
ClC6H4, 1-naphthyl) was subjected to reaction with the
five-membered cyclic α-oxo ketene dithioacetal 2; the re-
sults are summarized in Table 2. Regardless of whether
the substituents are electron-withdrawing or electron-
releasing, the transformations proceeded smoothly pro-
viding the corresponding [gem-bis(alkylthio)vinyl]allenes
3b–f in good to high yields (entries 1–5). Importantly
however, the reaction of 1 with R3 = 4-FC6H4 (entry 6),
afforded a slightly lower yield (79%) compared to the oth-
ers. A similarly easy transformation that afforded 3h in
89% yield was realized when R4 of the ketene dithioacetal
was changed to phenyl (entry 7). Further, alkyl-substitut-
ed propargyl alcohols were also applied in this coupling
reaction with 1a; to our delight, the corresponding vinyl-
allene 3i was obtained 95% yield (entry 8). When using a
Synthesis 2013, 45, 609–614
© Georg Thieme Verlag Stuttgart · New York

PAPER
A New Route to gem-Bis(alkylthio)-Substituted Vinylallenes
611
Table 2 Synthesis of [gem-Bis(alkylthio)vinyl]allenes 3a
tals is greatly influenced by the choice of alkylthio groups,
we decided to explore the nature of this effect on the less
activated six-membered cyclic α-oxo ketene dithioacetal
2′ as substrate (Table 3). Indeed, comparable results to the
five-membered cases were realized with a kinetic range of
10–30 minutes (entries 1–4).
R3
O
O
HO R2
R1
H
S
FeBr3 (20 mol%)
R4
R4
•
R2
+
toluene, r.t.
5–30 min
R1
R3
S
S
S
Table 3 Synthesis of [gem-Bis(alkylthio)vinyl]allenes 3′a
1
2
3
Entry R1
R2
R3
R4
Product Yieldb
(%)
O
S
R3
O
S
HO R2
R1
H
S
•
R2
FeBr3 (20 mol%)
+
1
2
3
4
5
6
7
8
9
Et
Ph
Ph
Ph
Ph
Ph
Ph
Me
Me
Me
Me
Me
3b
3c
3d
3e
3f
84
92
90
88
85
79
89
95
S
R1
toluene, r.t.
10–30 min
R3
Ph
1
2'
3'
Me
Me
Me
Me
Me
Me
2-ClC6H4
3-ClC6H4
Entry
R1
R2
Ph
R3
Ph
3′
Yieldb (%)
1-naphthyl Ph
1
2
3
4
Me
Me
Ph
3a′
3b′
3c′
3d′
87
89
88
89
Ph
Ph
Ph
4-FC6H4 Me
3g
3h
3i
2-ClC6H4
Ph
Ph
Ph
Ph
Ph
Pr
Ph
Me
Me
4-ClC6H4
4-ClC6H4
c
a Reaction conditions: 1 (0.55 mmol), 2′ (0.5 mmol), FeBr3 (20
mol%), toluene (1 mL), r.t.
(CH2)5
Ph
3j
–
a Reaction conditions: 1 (0.55 mmol), 2 (0.5 mmol), FeBr3 (20 mol%),
toluene (1 mL), r.t.
b Isolated yield.
c No reaction.
b Isolated yield.
To demonstrate the synthetic potential of the method, the
reaction of tertiary propargyl alcohol 1d and ketene di-
thioacetal 2a was carried out on a gram scale (Scheme 3).
Gratifyingly, the corresponding product 3d was isolated
in 87% yield.
tertiary propargyl alcohol prepared from cyclohexanone,
no reaction took place (entry 9). These results demonstrat-
ed the limitation and scope of tertiary propargyl alcohols.
Furthermore, other α-functionalized ketene dithioacetals
were examined in the dehydration coupling reaction with
tertiary propargyl alcohol 1a (Scheme 2). Unexpectedly,
the reaction of α-cyano ketene dithioacetal 2c with 1a af-
forded 1,1-bis(alkylthio)penten-4-yne 4 in 93% yield. No-
tably, no corresponding [gem-bis(alkylthio)vinyl]allene
product was formed. The reaction using α-aminoacyl ke-
tene dithioacetal 2d resulted in an unidentified mixture.
S
S
FeBr3 (20 mol%)
toluene, r.t., 0.5 h
•
1d
+
2a
Cl
Ph
O
3d
2.0 g, 87%
Scheme 3 Gram-scale experiment
Ph
S
NC
S
CN
2c
A plausible mechanism for the reaction is tentatively pro-
posed and depicted in Scheme 4. The polarity of the OH
group in 1 was enhanced by the interaction between the
ferric ion (Fe3+) and the hydroxy group leading to the for-
mation of the complex A, which was subsequently con-
verted into propargylic carbocation B with the loss of
[Fe3+]OH species.15a A resonance exists between propar-
gylic carbocation B and allenic carbocation C, and here
the later is preferably attacked by the electron-rich α-car-
bon of α-oxo ketene dithioacetal 2, leading to the target
[gem-bis(alkylthio)vinyl]allenes 3. The released H+ was
picked up by [Fe3+]OH species to furnish side product
H2O and ferric ion, hence preparing the latter for the next
catalytic cycle.
S
Ph
S
OH
FeBr3, 20 (mol%)
toluene, r.t.
Ph
4 93%
Ph
1a
unidentified mixture
S
O
2d
S
NH2
Scheme 2
Based on our previous observations11 and the findings of
Okuyama19 that the reactivity of α-oxo ketene dithioace-
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 609–614

612
Q. Li et al.
PAPER
MS (ESI): m/z = 365 [M + H]+.
[Fe3+
]
HRMS (ESI): m/z [M + H] calcd for C22H21OS2: 365.1034; found:
365.1022.
HO R2
R1
HO R2
R1
R1
R2
+
R3
[Fe3+
]
3-(1,3-Dithiolan-2-ylidene)-4,6-diphenylocta-4,5-dien-2-one
(3b)
White solid; yield: 160 mg (84%); mp 154–155 °C.
IR (KBr): 1625, 1453, 1279, 754, 690 cm–1.
1H NMR (500 MHz, CDCl3): δ = 1.27 (t, J = 7.0 Hz, 3 H), 2.15 (s,
3 H), 2.61–2.66 (m, 1 H), 2.74–2.79 (m, 1 H), 3.22 (q, J = 7.0 Hz, 2
H), 3.42–3.44 (m, 2 H), 7.24–7.25 (m, 2 H), 7.26–7.33 (m, 4 H),
7.33–7.39 (m, 2 H), 7.40–7.45 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = 13.4, 24.0, 35.4, 39.4, 109.5,
111.5, 119.9, 125.6, 126.7, 127.2, 127.3, 128.3, 128.8, 134.8, 135.4,
165.7, 193.9, 205.9.
R3
R3
+
1
A
B
[Fe3+]OH
H+
H2O
O
R3
S
R1
R2
+
R4
•
R1
•
R3
R2
S
S
2
H
S
MS (ESI): m/z = 379 [M + H]+.
C
R4
HRMS (ESI): m/z [M + H] calcd for C23H23OS2: 379.1190; found:
379.1190.
3
O
3-(1,3-Dithiolan-2-ylidene)-4,6,6-triphenylhexa-4,5-dien-2-one
Scheme 4 A plausible reaction mechanism
(3c)
White solid; yield: 195 mg (92%); mp 164–165 °C.
IR (KBr): 1637, 1462, 1267, 759, 672 cm–1.
In summary, we have described a straightforward and
step-economic method for the potent synthesis of [gem-
bis(alkylthio)vinyl]allenes utilizing readily available
starting materials and environmentally benign iron cata-
lyst as the catalyst. This procedure constitutes a direct and
practical route to fully substituted vinylallenes, which
would find synthetic utility in cyclization reactions. To-
ward this end, the exploration of the intrinsically embed-
ded features of these vinylallenes products is ongoing in
our laboratory, and will be reported in due course.
1H NMR (500 MHz, CDCl3): δ = 2.03 (s, 3 H), 3.21 (t, J = 6.0 Hz,
2 H), 3.45 (t, J = 6.0 Hz, 2 H), 7.25–7.29 (m, 1 H), 7.30–7.32 (m, 2
H), 7.35 (m, 6 H), 7.40–7.42 (m, 6 H).
13C NMR (125 MHz, CDCl3): δ = 27.8, 35.6, 39.5, 109.5, 113.3,
119.0, 125.9, 127.6, 127.7, 128.3, 128.5, 128.8, 128.9, 134.1, 135.4,
166.3, 193.8, 207.4.
MS (ESI): m/z = 427 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C27H23OS2: 427.1190; found:
427.1182.
6-(2-Chlorophenyl)-3-(1,3-dithiolan-2-ylidene)-4-phenylhepta-
4,5-dien-2-one (3d)
All reagents were purchased from commercial sources and used
without further treatment, unless otherwise indicated. The products
White solid; yield: 179 mg (90%); mp 135–136 °C.
were purified by column chromatography over silica gel. 1H and 13
C
IR (KBr): 1655, 1472, 1280, 772, 683 cm–1.
NMR spectra were recorded at 25 °C at 500 MHz and 125 Hz, re-
spectively, with TMS as internal standard. Mass spectra were re-
corded on Bruker AutoflexIII Smartbeam MS spectrometer. HRMS
were recorded on Bruck microTof by using ESI method. IR spectra
(KBr) were recorded on FTIR spectrophotometer in the range of
400–4000 cm–1.
1H NMR (500 MHz, CDCl3): δ = 2.03 (s, 3 H), 2.26 (s, 3 H), 3.15–
3.25 (m, 2 H), 3.43–3.47 (m, 2 H), 7.18–7.25 (m, 3 H), 7.32–7.35
(m, 3 H), 7.38–7.40 (m, 3 H).
13C NMR (125 MHz, CDCl3): δ = 18.7, 27.6, 35.4, 39.5, 102.5,
106.6, 119.8, 126.2, 126.6, 127.2, 128.4, 128.6, 129.8, 129.9, 132.6,
134.6, 136.1, 165.5, 193.9, 204.3.
3-(1,3-Dithiolan-2-ylidene)-4,6-diphenylhepta-4,5-dien-2-one
(3a); Typical Procedure
MS (ESI): m/z = 399 [M + H]+.
To a soln of 1a (122 mg, 0.55 mmol) in toluene (1.0 mL) at r.t., 2a
(80 mg, 0.5 mmol) and FeBr3 (30 mg, 0.10 mmol) were added in
succession and the mixture stirred for 5 min at r.t. (20 °C) without
exclusion of air. After the reaction was complete (monitored by
TLC), the mixture was diluted with CH2Cl2 (10 mL) and aq NaCl
soln (10 mL). The mixture was stirred for an additional 30 min and
the two layers separated. The aqueous layer was extracted with
CH2Cl2 (3 × 5 mL). The combined organic layers were dried
(MgSO4) and filtered, and the solvent was removed by rotary evap-
oration. The residue was purified by column chromatography (silica
gel, PE–EtOAc,10:1) to afford 3a as a white solid; yield: 166 mg
(91%); mp 144–145 °C.
HRMS (ESI): m/z [M + H] calcd for C22H20ClOS2: 399.0644;
found: 399.0387.
6-(3-Chlorophenyl)-3-(1,3-dithiolan-2-ylidene)-4-phenylhepta-
4,5-dien-2-one (3e)
White solid; yield: 175 mg (88%); mp 144–145 °C.
IR (KBr): 1643, 1475, 1266, 780, 687 cm–1.
1H NMR (500 MHz, CDCl3): δ = 2.20 (s, 3 H), 2.25 (s, 3 H), 3.24–
3.28 (m, 2 H), 3.43–3.46 (m, 2 H), 7.20–7.22 (m, 1 H), 7.24–7.28
(m, 2 H), 7.34–7.37 (m, 5 H), 7.48 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 15.6, 27.7, 35.5, 39.6, 103.6,
109.1, 119.6, 124.2, 125.9, 126.3, 127.2, 127.6, 128.9, 129.6, 134.4,
134.4, 138.1, 165.9, 193.5, 206.5.
IR (KBr): 1643, 1481, 1270, 767, 691 cm–1.
1H NMR (500 MHz, CDCl3): δ = 2.20 (s, 3 H), 2.28 (s, 3 H), 3.23–
3.29 (m, 2 H), 3.44–3.47 (m, 2 H), 7.24–7.27 (m, 2 H), 7.25–7.36
(m, 6 H), 7.49 (m, 2 H).
MS (ESI): m/z = 399 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C22H20ClOS2: 399.0644;
13C NMR (125 MHz, CDCl3): δ = 15.7, 27.9, 35.5, 39.6, 104.5,
108.6, 120.0, 125.9, 126.1, 127.3, 127.4, 128.5, 128.8, 134.9, 136.0,
165.6, 193.8, 206.5.
found: 399.0646.
Synthesis 2013, 45, 609–614
© Georg Thieme Verlag Stuttgart · New York

PAPER
A New Route to gem-Bis(alkylthio)-Substituted Vinylallenes
613
3-(1,3-Dithiolan-2-ylidene)-6-(naphthalen-1-yl)-4-phenylhepta-
4,5-dien-2-one (3f)
IR (KBr): 1635, 1465, 1262, 763, 691 cm–1.
1H NMR (500 MHz, CDCl3): δ = 2.17–2.18 (m, 2 H), 2.19 (s, 3 H),
2.29 (s, 3 H), 2.86–2.96 (m, 4 H), 7.23–7.28 (m, 2 H), 7.31–7.38 (m,
6 H), 7.51–7.53 (m, 2 H).
White solid; yield: 175 mg (85%); mp 166–167 °C.
IR (KBr): 1632, 1462, 1274, 812, 683 cm–1.
1H NMR (500 MHz, CDCl3): δ = 1.89 (s, 3 H), 2.36 (s, 3 H), 3.04–
3.13 (m, 2 H), 3.36–3.38 (m, 2 H), 7.19–7.22 (m, 1 H), 7.29–7.32
(m, 2 H), 7.35–7.43 (m, 5 H), 7.45–7.49 (m, 1 H), 7.73–7.75 (m, 1
H), 7.79–7.81 (m, 1 H), 8.13–8.15 (m, 1 H).
13C NMR (125 MHz, CDCl3): δ = 19.9, 27.6, 35.2, 39.5, 102.3,
106.0, 119.9, 125.1, 125.2, 125.3, 125.6, 125.9, 126.0, 127.1, 127.6,
128.2, 128.6, 130.8, 133.6, 135.1, 135.3, 165.6, 193.9, 204.4.
13C NMR (125 MHz, CDCl3): δ = 15.7, 23.8, 29.0, 29.2, 29.8,
104.2, 106.9, 125.8, 126.2, 127.3, 127.4, 128.2, 128.4, 128.8, 135.1,
136.1, 161.6, 194.5, 207.2.
MS (ESI): m/z = 379 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C23H23OS2: 379.1190; found:
379.1214.
MS (ESI): m/z = 415 [M + H]+.
6-(2-Chlorophenyl)-3-(1,3-dithian-2-ylidene)-4-phenylhepta-
4,5-dien-2-one (3b′)
HRMS (ESI): m/z [M + H] calcd for C26H23OS2: 415.1190; found:
415.1185.
White solid; yield: 183 mg (89%); mp 150–151 °C.
IR (KBr): 1637, 1462, 1267, 761, 677 cm–1.
3-(1,3-Dithiolan-2-ylidene)-4-(4-fluorophenyl)-6-phenylhepta-
4,5-dien-2-one (3g)
1H NMR (500 MHz, CDCl3): δ = 2.01 (s, 3 H), 2.14–2.19 (m, 2 H),
2.26 (s, 3 H), 2.83–2.85 (m, 2 H), 2.86–2.89 (m, 1 H), 2.95–2.96 (m,
1 H), 7.17–7.27 (m, 3 H), 7.31–7.37 (m, 3 H), 7.38–7.40 (m, 3 H).
13C NMR (125 MHz, CDCl3): δ = 18.7, 23.8, 28.8, 29.0, 29.6,
102.4, 105.0, 126.2, 126.6, 127.2, 128.2, 128.4, 128.6, 129.9, 132.6,
134.9, 136.3, 161.2, 176.2, 194.5, 204.9.
White solid; yield: 150 mg (79%); mp 164–165 °C.
IR (KBr): 1637, 1468, 1270, 1242, 840, 585 cm–1.
1H NMR (500 MHz, CDCl3): δ = 2.19 (s, 3 H), 2.28 (s, 3 H), 3.27–
3.28 (m, 2 H), 3.46 (t, J = 6.5 Hz, 2 H), 7.00–7.04 (m, 2 H), 7.23–
7.29 (m, 1 H), 7.30–7.39 (m, 4 H), 7.47–7.49 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = 15.7, 27.8, 35.5, 39.6, 104.7,
107.7, 115.7, 115.9, 126.1, 127.4, 127.4, 127.5, 128.5, 130.8, 130.8,
135.8, 161.2, 163.2, 165.9, 193.5, 206.1.
MS (ESI): m/z = 413 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C23H22ClOS2: 413.0801;
found: 413.0797.
MS (ESI): m/z = 383 [M + H]+.
3-(1,3-Dithian-2-ylidene)-4,6,6-triphenylhexa-4,5-dien-2-one
(3c′)
HRMS (ESI): m/z [M + H] calcd for C22H20FOS2: 383.0940; found:
383.0940.
White solid; yield: 193 mg (88%); mp 153–154 °C.
IR (KBr): 1635, 1440, 1270, 770, 696 cm–1.
2-(1,3-Dithiolan-2-ylidene)-1,3,5-triphenylhexa-3,4-dien-1-one
(3h)
1H NMR (500 MHz, CDCl3): δ = 2.01 (s, 3 H), 2.15–2.18 (m, 2 H),
2.85 (t, J = 7.0 Hz, 2 H), 2.91 (t, J = 7.0 Hz, 2 H), 7.25–7.27 (m, 1
H), 7.30–7.33 (m, 2 H), 7.33–7.38 (m, 6 H), 7.40–7.44 (m, 6 H).
13C NMR (125 MHz, CDCl3): δ = 23.7, 29.0, 29.1, 29.7, 108.2,
113.2, 125.8, 127.3, 127.6, 127.7, 128.3, 128.9, 128.9, 134.5, 135.5,
162.5, 194.5, 207.8.
Yellow solid; yield: 189 mg (89%); mp 122–123 °C.
IR (KBr): 1634, 1467, 1269, 720, 694 cm–1.
1H NMR (500 MHz, CDCl3): δ = 1.80 (s, 3 H), 3.31–3.34 (m, 2 H),
3.44–3.49 (m, 2 H), 7.19–7.25 (m, 8 H), 7.30 (t, J = 7.5 Hz, 2 H),
7.33–7.38 (m, 3 H), 7.52 (d, J = 7.5 Hz, 2 H).
13C NMR (125 MHz, CDCl3): δ = 15.0, 36.1, 39.2, 104.6, 109.3,
119.4, 126.1, 126.3, 127.1, 127.1, 127.6, 127.9, 128.3, 128.7, 130.3,
135.5, 135.8, 139.9, 168.8, 191.1, 207.3.
MS (ESI): m/z = 441 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C28H25OS2: 441.1347; found:
441.1365.
MS (ESI): m/z = 427 [M + H]+.
6,6-Bis(4-chlorophenyl)-3-(1,3-dithian-2-ylidene)-4-phenyl-
hexa-4,5-dien-2-one (3d′)
HRMS (ESI): m/z [M + H] calcd for C27H23OS2: 427.1190; found:
427.1231.
White solid; yield: 226 mg (89%); mp 162–163 °C.
IR (KBr): 1641, 1481, 1267, 1089, 838, 556 cm–1.
3-(1,3-Dithiolan-2-ylidene)-6-phenyl-4-propylhepta-4,5-dien-2-
one (3i)
1H NMR (500 MHz, CDCl3): δ = 2.01 (s, 3 H), 2.17–2.20 (m, 2 H),
2.86 (t, J = 7.0 Hz, 2 H), 2.92 (t, J = 7.0 Hz, 2 H), 7.26–7.30 (m, 2
H), 7.31–7.33 (m, 6 H), 7.33–7.35 (m, 1 H), 7.35–7.36 (m, 4 H).
13C NMR (125 MHz, CDCl3): δ = 23.7, 23.8, 29.0, 29.8, 108.9,
111.3, 125.9, 126.8, 127.8, 127.9, 128.7, 128.8, 129.1, 129.2, 130.0,
133.7, 133.7, 133.9, 162.9, 194.1, 207.7.
Yellow liquid; yield: 157 mg (95%).
IR (KBr): 1604, 1445, 1278, 762, 693 cm–1.
1H NMR (500 MHz, CDCl3): δ = 7.44 (dd, J = 1.5, 8.0 Hz, 2 H),
7.32 (t, J = 8.0 Hz, 2 H), 7.20 (t, J = 7.5 Hz, 1 H), 3.36 (t, J = 6.5
Hz, 2 H), 3.30–3.21 (m, 2 H), 2.39–2.29 (m, 4 H), 2.26–2.18 (m, 1
H), 2.15 (s, 3 H), 1.59 (q, J = 7.5, 15.0 Hz, 2 H), 0.99 (t, J = 7.5 Hz,
3 H).
MS (ESI): m/z = 509 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C28H23Cl2OS2: 509.0567;
found: 509.0552.
13C NMR (125 MHz, CDCl3): δ = 203.1, 193.1, 163.1, 136.9, 128.1,
126.5, 125.8, 122.8, 106.7, 101.8, 39.2, 35.3, 34.9, 27.5, 20.9, 15.9,
13.8.
2-(1,3-Dithiolan-2-ylidene)-3-methyl-3,5-diphenylpent-4-yneni-
trile (4)
Yellow solid; yield: 161 mg (93%); mp 186–187 °C.
IR (KBr): 1611, 1250, 1113, 889, 721, 507 cm–1.
MS (ESI): m/z = 331 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C19H23OS2: 331.1190; found:
1H NMR (500 MHz, CDCl3): δ = 7.60 (d, J = 8.5 Hz, 2 H), 7.54–
7.49 (m, 2 H), 7.38–7.31 (m, 5 H), 7.28 (t, J = 7.5 Hz, 1 H), 3.47–
3.40 (m, 1 H), 3.40–3.36 (m, 2 H), 3.35–3.29 (m, 1 H), 1.96 (s, 3 H).
331.1191.
3-(1,3-Dithian-2-ylidene)-4,6-diphenylhepta-4,5-dien-2-one
(3a′)
White solid; yield: 164 mg (87%); mp 165–166 °C.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 609–614

614
Q. Li et al.
PAPER
13C NMR (125 MHz, CDCl3): δ = 165.3, 143.4, 131.6, 128.37,
128.3, 128.2, 127.1, 126.4, 122.9, 118.6, 101.4, 90.2, 85.6, 42.9,
41.4, 37.0, 33.2.
Weinheim, 2004. (b) Ma, S. Chem. Rev. 2005, 105, 2829.
(c) Sydnes, L. K. Chem. Rev. 2003, 103, 1133.
(10) Fang, Z.; Yuan, H.; Liu, Y.; Tong, Z.; Li, H.; Yang, J.; Barry,
B.; Liu, J.; Liao, P.; Zhang, J.; Liu, Q.; Bi, X. Chem.
Commun. 2012, 48, 8802.
MS (ESI): m/z = 348 [M + H]+.
HRMS (ESI): m/z [M + H] calcd for C21H18NS2: 348.0881; found:
348.0883.
(11) Song, J.; Fang, Z.; Liu, Y.; Li, R.; Xu, L.; Barry, B.; Liu, Q.;
Bi, X. Synlett 2011, 2551.
(12) Yoshida, M.; Gotou, T.; Ihara, M. Tetrahedron Lett. 2004,
45, 5573.
(13) (a) Swaminathan, S.; Narayanan, K. V. Chem. Rev. 1971,
71, 429. (b) Edens, M.; Boerner, D.; Chase, C. R.; Nass, D.;
Schiavelli, M. D. J. Org. Chem. 1977, 42, 3403.
(14) (a) Wang, S.; Zhu, Y.; Wang, Y.; Lu, P. Org. Lett. 2009, 11,
2615. (b) Zhu, Y.; Yin, G.; Hong, D.; Lu, P.; Wang, Y. Org.
Lett. 2011, 13, 1024. (c) Yin, G.; Zhu, Y.; Lu, P.; Wang, Y.
J. Org. Chem. 2011, 76, 8922. (d) Zhu, Y.; Wen, S.; Yin, G.;
Hong, D.; Lu, P.; Wang, Y. Org. Lett. 2011, 13, 3553.
(e) Yin, G.; Zhu, Y.; Zhang, L.; Lu, P.; Wang, Y. Org. Lett.
2011, 13, 940. (f) Chen, X.; Wang, H.; Jin, X.; Feng, J.;
Wang, Y.; Lu, P. Chem. Commun. 2011, 47, 2628.
(g) Zhang, L.; Zhu, Y.; Yin, G.; Lu, P.; Wang, Y. J. Org.
Chem. 2012, 77, 9510.
Acknowledgment
This work was supported by NSFC (21172029, 21202016,
31101010), Fundamental Research Funds for the Central Universi-
ties (11CXPY005), Research Fund for the Doctoral Program of
Higher Education of China (RFDP 20100043120008) and China
Postdoctoral Science Foundation (2012M51854).
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnuIomprifgtooatrinSugpIoi
nnfomartit
References
(15) (a) Zhang, X.; Teo, W. T.; Chan, P. W. H. Org. Lett. 2009,
11, 4990. (b) Zhang, X.; Teo, W. T.; Chan, P. W. H. J. Org.
Chem. 2010, 75, 6290. (c) Rao, W.; Chan, P. W. H. Org.
Biomol. Chem. 2010, 8, 4016. (d) Kothandaraman, P.;
Mothe, S. R.; Toh, S. S. M.; Chan, P. W. H. J. Org. Chem.
2011, 76, 7633. (e) Mothe, S. R.; Lauw, S. J. L.;
Kothandaraman, P.; Chan, P. W. H. J. Org. Chem. 2012, 77,
6937. (f) Susanti, D.; Koh, F.; Kusuma, J. A.;
(1) (a) Robinson, J. M.; Sakai, T.; Okano, K.; Kitawaki, T.;
Danheiser, R. L. J. Am. Chem. Soc. 2010, 132, 11039.
(b) Regás, D.; Ruiz, J. M.; Afonso, M. M.; Palenzuela, J. A.
J. Org. Chem. 2006, 71, 9153. (c) Ruiz, J. M.; Regás, D.;
Afonso, M. M.; Palenzuela, J. A. J. Org. Chem. 2008, 73,
7246.
(2) (a) Souto, J. A.; López, C. S.; Faza, O. N.; Alvarez, R.; de
Lera, A. R. Org. Lett. 2005, 7, 1565. (b) Murakami, M.;
Itami, K.; Ito, Y. Angew. Chem., Int. Ed. Engl. 1995, 34,
2691.
Kothandaraman, P.; Chan, P. W. H. J. Org. Chem. 2012, 77,
7166.
(16) (a) Yao, L.-F.; Tan, D.; Miao, X.; Huang, K.-W. RSC Adv.
2012, 2, 7594. (b) Guo, L.-N.; Duan, X.-H.; Liang, Y.-M.
Acc. Chem. Res. 2011, 44, 111. (c) Zhu, H.-T.; Ji, K.-G.;
Yang, F.; Wang, L.-J.; Zhao, S.-C.; Ali, S.; Liu, X.-Y.;
Liang, Y.-M. Org. Lett. 2011, 13, 684. (d) Wang, T.; Chen,
X.; Chen, L.; Zhan, Z. Org. Lett. 2011, 13, 3324. (e) Pan, Y.;
Zhao, S.; Ji, W.; Zhan, Z. J. Comb. Chem. 2009, 11, 103.
(17) (a) Wang, Y.; Li, W.; Che, G.; Bi, X.; Liao, P.; Zhang, Q.;
Liu, Q. Chem. Commun. 2010, 46, 6843. (b) Wang, Y.; Bi,
X.; Li, D.; Liao, P.; Wang, Y.; Yang, J.; Zhang, Q.; Liu, Q.
Chem. Commun. 2011, 47, 809. (c) Xiong, T.; Li, Y.; Bi, X.;
Lv, Y.; Zhang, Q. Angew. Chem. Int. Ed. 2011, 50, 7140.
(d) Wang, Y.; Bi, X.; Li, W.; Li, D.; Zhang, Q.; Liu, Q.;
Ondon, B. S. Org. Lett. 2011, 13, 1722. (e) Hu, Y.; Fu, X.;
Barry, B.-D.; Bi, X.; Dong, D. Chem. Commun. 2012, 48,
690. (f) Wang, Z.; Bi, X.; Liao, P.; Zhang, R.; Liang, Y.;
Dong, D. Chem. Commun. 2012, 48, 7076. (g) Xiang, D.; Bi,
X.; Liao, P.; Fang, G.; Wang, Z.; Xin, X.; Dong, D. RSC
Adv. 2013, 3, 386. (h) Wang, Z.; Bi, X.; Liao, P.; Lin, X.;
Dong, D. Chem. Commun. 2013, 49, 1309.
(3) Delas, C.; Urabe, H.; Sato, F. J. Am. Chem. Soc. 2001, 123,
7937.
(4) (a) Faza, O. N.; López, C. S.; de Lera, A. R. J. Org. Chem.
2007, 72, 2617. (b) Knudsen, C. G.; Carey, S. C.; Okamura,
W. H. J. Am. Chem. Soc. 1980, 102, 6355.
(5) (a) Wu, Y.; West, F. G. J. Org. Chem. 2010, 75, 5410.
(b) Funami, H.; Kusama, H.; Iwasawa, N. Angew. Chem. Int.
Ed. 2007, 46, 909. (c) Lee, J. H.; Toste, F. D. Angew. Chem.
Int. Ed. 2007, 46, 912. (d) Cergol, K. M.; Newton, C. G.;
Lawrence, A. L.; Willis, A. C.; Paddon-Row, M. N.;
Sherburn, M. S. Angew. Chem. Int. Ed. 2011, 50, 10425.
(6) (a) Krause, N.; Purpura, M. Angew. Chem. Int. Ed. 2000, 39,
4355. (b) Purpura, M.; Krause, N. Eur. J. Org. Chem. 1999,
267. (c) Dulcere, J.-P.; Grimaldi, J.; Santelli, M.
Tetrahedron Lett. 1981, 22, 3179. (d) Dulcere, J. P.;
Roumestant, M. L.; Gore, J. Tetrahedron Lett. 1972, 13,
4465.
(7) For examples of the substituent-regulated reactivity of
vinylallenes, see: (a) Murakami, M.; Amii, H.; Itami, K.; Ito,
Y. Angew. Chem., Int. Ed. Engl. 1995, 34, 1476.
(b) Murakami, M.; Ashida, S.; Matsuda, T. J. Am. Chem.
Soc. 2004, 126, 10838.
(18) For reviews on the iron-catalyzed organic reactions, see:
Iron Catalysis in Organic Chemistry: Reactions and
Applications; Plietker, B., Ed.; Wiley-VCH: Weinheim,
2008.
(19) (a) Okuyama, T. Acc. Chem. Res. 1986, 19, 370.
(b) Okuyama, T. J. Am. Chem. Soc. 1984, 106, 7134.
(8) For a recent review on the chemistry of ketene dithioacetals,
see: Pan, L.; Bi, X.; Liu, Q. Chem. Soc. Rev. 2013, 42, 1251.
(9) For selected reviews of allenes, see: (a) Modern Allene
Chemistry; Krause, N.; Hashmi, A. S. K., Eds.; Wiley-VCH:
Synthesis 2013, 45, 609–614
© Georg Thieme Verlag Stuttgart · New York