Pd-Catalyzed, Ligand-Enabled Stereoselective 1,2-Iodine(III) Shift/1,1-Carboxyalkynylation of Alkynylbenziodoxoles

Article abstract of DOI:10.1002/chem.201605772

A Pd^II-catalyzed 2:1 coupling reaction of alkynylbenziodoxole with carboxylic acid to afford (alk-1-en-3-ynyl)benziodoxole, which is efficiently promoted by an octahydrophenazine ligand, is reported. The reaction involves a Pd-assisted 1,2-iodine(III) shift of the alkynylbenziodoxole followed by stereoselective introduction of carboxy and alkynyl groups (the latter originating from another molecule of the alkynylbenziodoxole) into the 1-position of the transient Pd-vinylidene species. The product of this 1,1-carboxyalkynylation reaction serves as a new functionalized enyne-type building block for further synthetic transformations.

Full text of DOI:10.1002/chem.201605772

A Journal of
Accepted Article
Title: Pd-Catalyzed, Ligand-Enabled Stereoselective 1,2-Iodine(III)
Shift/1,1-Carboxyalkynylation of Alkynylbenziodoxoles
Authors: Junliang Wu, Kai Xu, Hajime Hirao, and Naohiko Yoshikai
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To be cited as: Chem. Eur. J. 10.1002/chem.201605772
Link to VoR: http://dx.doi.org/10.1002/chem.201605772
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COMMUNICATION
Pd-Catalyzed, Ligand-Enabled Stereoselective 1,2-Iodine(III)
Shift/1,1-Carboxyalkynylation of Alkynylbenziodoxoles**
[
a]
Junliang Wu, Kai Xu, Hajime Hirao,* and Naohiko Yoshikai*
Abstract:
A
palladium(II)-catalyzed 2:1 coupling reaction of
basis of this hypothesis, we have developed an efficient 2:1
coupling reaction between and to afford (alk-1-en-3-
ynyl)benziodoxole 4, which is enabled by Pd(II)–
alkynylbenziodoxole with carboxylic acid to afford (alk-1-en-3-
ynyl)benziodoxole, which is efficiently promoted by an
octahydrophenazine ligand, is reported. The reaction involves
palladium-assisted 1,2-iodine(III) shift of the alkynylbenziodoxole
followed by stereoselective introduction of carboxy and alkynyl
groups, the latter originating from another molecule of the
alkynylbenziodoxole, into the 1-position of the transient Pd–
vinylidene species. The product of this 1,1-carboxyalkynylation
reaction serves as a novel functionalized enyne-type building block
for further synthetic transformations.
1
2
a
octahydrophenazine catalyst (Scheme 1b). In this carboxylative
dimerization, one molecule of 1 undergoes the 1,2-I(III) shift,
while the other transfers the alkynyl group to the former in the
stereoselective 1,1-carboxyalkynylation process. The product 4
serves as a functionalized enyne that is amenable to a series of
further synthetic transformations.
(a) Recent finding: Pd-catalyzed 1,2-I(III) shift/1,1-hydrocarboxylation
[
Pd(2-methylallyl)(OAc)]2
1,5-cyclooctadiene
2
R1
I
R OCO
R1
O
I
2
R CO H (2, 10 equiv)
2
As a part of extensive studies on the use of hypervalent iodine
F
3
C
F C
3
H
[
1]
3
compounds in organic synthesis, alkynyl-λ -iodanes have been
established as reagents for electrophilic alkynyl group transfer to
nucleophiles, offering an array of alkynylation methods
complementary to the conventional alkynylation reactions
CF3
CF3
O
1
3
Pd(OCOR2)2
H+
[
1a-f,2]
involving nucleophilic acetylides.
In particular, cyclic alkynyl-
2
R1
2
1
R OCO
3
[1c-f,3]
Pd(OCOR
)2
R
C
λ -iodanes such as alkynylbenziodoxol(on)es
increased stability and have found growing number of
applications in non-conventional alkynylation reactions involving
feature
2
(
R OCO) Pd
C
2
IIII
R1
IIII
R
2
OCOPd
I
III
a
Int1
Int2
Int3
[
4]
[5]
C–H bond functionalization,
decarboxylation,
or other
[
6]
(b) This work: 1,2-I(III) shift/1,1-carboxyalkynylation
mechanistically intriguing processes.
R1
While alkynylbenziodoxol(on)es have been primarily
designed and explored as reagents for alkynylation, notable
examples of their transformations beyond simple alkynyl group
transfer have been reported, including furan-forming
O
I
Pd(OAc)
R CO H (2)
2
2
2
R1
R OCO
2
F C
3
F C
3
I
N
CF3
CF3
R1
O
1
(2.4 equiv)
[
7]
N
4
condensation by us, oxy-alkynylation of diazo compounds by
octahydrophenazine
[
8]
Waser, and α-vinylidenation and α-vinylidenation/γ-alkynylation
[
9]
of aldehydes by Huang. As one of such examples, we have
recently disclosed palladium-catalyzed reaction between
alkynylbenziodoxole 1 and carboxylic acid 2 that proceeds via
,2-iodine(III) shift/1,1-hydrocarboxylation processes, affording
synthetically versatile β-oxyalkenylbenziodoxole in
The reaction can be
rationalized by a sequence of 1,2-shift of the benziodoxole
Scheme 1. Pd-catalyzed 1,2-I(III) shift/1,1-carboxyfunctionalization of
alkynylbenziodoxole.
a
1
3
a
Table 1 summarizes the screening process that led to the
identification of octahydrophenazine as the optimum ligand for
[
7c,10]
stereocontrolled manner (Scheme 1a).
the
alkynylbenziodoxole 1a (2.4 equiv) and benzoic acid (2a) to
Pd(OAc) alone (10 mol %) resulted in complete
present
1,1-carboxyalkynylation.
Exposure
of
[
11,12]
moiety of Pd(II)-coordinated alkynylbenziodoxole (Int1),
migratory insertion of the transient vinylidene–Pd(II) species
Int2), and protonation of the resulting β-iodo(III)alkenyl–Pd(II)
2
a
(
decomposition of 1a to a complex mixture of products, with an
observation of the decomposition of the Pd(II) catalyst to Pd
black (entry 1). The addition of pyridine (L1, 1 equiv) had a
dramatic effect on the reaction outcome, affording the enyne
species (Int3). We hypothesized that interception of the putative
intermediate Int3 with an electrophile rather than a proton would
lead to a tetrasubstituted alkenylbenziodoxole derivative. On the
[
13]
product 4a in 40% yield (entry 2).
In contrast, the use of a
catalytic amount of pyridine (15 mol %) resulted in
a
predominance of the decomposition of 1a and a diminished yield
of 4a (entry 3). The same trend was observed for a series of
pyridine-based and related ligands, including 2,6-diethylpyridine
[a]
Dr. J. Wu, K. Xu, Prof. H. Hirao, Prof. N. Yoshikai
Division of Chemistry and Biological Chemistry, School of Physical
and Mathematical Sciences
Nanyang Technological University
Singapore 637371, Singapore
(
L2) and 2,3-diethylquinoxaline (L3) (entries 4–7). However, two
effective ligands, tetrahydrophenazine (L4) and
E-mail: hirao@ntu.edu.sg, nyoshikai@ntu.edu.sg
octahydrophenazine (L5), were identified upon further screening.
L4 afforded 4a in good yields, with both stoichiometric and
catalytic loading (entries 8 and 9). Conversely, the stoichiometric
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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COMMUNICATION
use of L5 slowed the reaction, albeit under retention of an
excellent mass balance (entry 10). Using a catalytic amount of
L5, the reaction rate was restored and 4a was obtained in
almost quantitative yield (entry 11). Note that the
hydrocarboxylation product (Scheme 1a) was not observed in
these optimization experiments. On the other hand, the
optimized catalytic system for the hydrocarboxylation only
afforded 4a or 4b, respectively, without significant decrease in
the yield. Benziodoxoles derived from alkylacetylenes, enynes,
and diynes were also amenable to the 1,1-carboxyalkynylation,
and afforded the desired alkenylbenziodoxole products including
those containing novel oligoenyne moieties (4m–4p). Apart from
benzoic acid and acetic acid, a series of aryl- and alkylcarboxylic
acids could also be employed as reaction partners for 1a, which
afforded the corresponding 1,1-carboxyalkynylation products
(4q–4v) in good to excellent yields (75–96%).
produced
a
mixture of the hydrocarboxylation and the
carboxyalkynylation products when an excess amount of 1a was
used.
[a]
Table 2. Scope of 1,2-I(III) shift/1,1-carboxyalkynylation
Table 1. Effect of reaction conditions on addition of N-H imine 1a
2
R1
I
[
a]
Pd(OAc)2 (10 mol%)
R OCO
vinyltrimethylsilane.
O
I
R1
L5 (15 mol%)
F3C
F3C
R CO2H (2)
2
Pd(OAc)2 (10 mol%)
ligand
BzO
Ph
I
CF3
O
I
Ph
toluene, rt, 24 h
R1
O
PhCO2H (2a)
CF3
F3C
F3C
1
4
toluene, rt, 24 h
CF3
CF3
R1
Ph
O
1
a
4a
R2
O
N
N
R
R
N
O
a (R1 = H, R2 = Ph), 89%[b]
4
4
4
b (R1 = H, R2 = Me), 98%, 95%[b]
IIII
R
N
R
N
c (R1 = Cl, R2 = Ph), 95%
L1 (R = H)
L2 (R = Et)
L3 (R = Et)
L5
4d (R1 = CO Et, R2 = Me), 97%
4e (R1 = CN, R2 = Ph), 92%
2
L4 (R, R = -(CH2)4-)
4
f (R1 = COMe, R2 = Me), 93%
[
b]
R1
Entry
Ligand (mol%)
None
Conv. of 1a [%]
Yield [%]
0
4g (R1 = Me, R2 = Ph), 74%
4
a (X-ray)
1
2
3
4
5
6
7
8
9
1
1
100
100
100
100
100
100
100
100
100
51
CF3
AcO
OMe
BzO
BzO
L1 (100)
L1 (15)
40
F
IIII
IIII
IIII
F
< 5
F3C
MeO
L2 (100)
L2 (15)
60
4
h, 94%
4i, 75%
4j, 48%
< 10
40
BzO
Me
BzO
OBn
BzO
L3 (100)
L3 (15)
IIII
IIII
IIII
< 5
Me
BnO
4
k, 80%
4l, 85%
4m, 77%
L4 (100)
L4 (15)
85
SiMe3
Bu
Ph
70
BzO
AcO
AcO
0
1
L5 (100)
L5 (15)
48
IIII
IIII
IIII
100
98 (95)
Me3Si
Bu
Ph
[
2
a] Conditions: 1a (0.24 mmol), 2a (0.1 mmol), Pd(OAc) (10 mol%), ligand,
19
4
n, 78%
4o, 82%
4p, 72%
toluene (0.067 M), room temperature, 24 h. [b] Determined by F NMR
spectroscopy using 1,4-bis(trifluoromethyl)benzene as an internal standard.
Isolated yield shown in parentheses.
R
NHBoc
O
S
Having identified L5 as the optimal ligand, we explored the
scope of the 1,2-I(III) shift/1,1-carboxyalkynylation, which is
summarized in Table 2. A variety of aryl(alkynyl)benziodoxoles,
especially those bearing electron-withdrawing groups, reacted
smoothly with 2a or acetic acid (2b) to afford the desired (alk-1-
en-3-ynyl)benziodoxoles 4a–4j in moderate to excellent yields.
In contrast, as was also the case with the 1,1-
O
Ph
O
Ph
O
Ph
IIII
Ph
O
O
O
O
IIII
IIII
IIII
Ph
Ph
4t, 95%
Ph
Ph
4v, 75%
4
4
q (R = 4-Cl), 96%
r (R = 4-MeO), 83%
4u, 84%
4s (R = 2-Me), 85%
[
7c]
[b]
hydrocarboxylation,
electron-rich
4-
[a] The reaction was performed under the conditions in Table 1, entry 11.
2
mmol scale with respect to 2.
methoxyphenyl(ethynyl)benziodoxole decomposed under the
applied conditions, not affording the desired product. The
scalability of the present reaction was demonstrated by a gram-
scale reaction of 1a (2 mmol, 2.26 g) with 2a or 2b, which
13
13
The reaction of C-labeled alkynylbenziodoxole 1a- C with
a under the present reaction conditions afforded the product
2
4
13
13
2
a- C , whose C NMR spectrum confirmed the presence of
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COMMUNICATION
1
3
two adjacent C atoms in the middle of the enyne chain with a
large JC–C coupling constant of 116 Hz (Scheme 2). This
observation corroborates the notion of 1,2-I(III) shift and also
demonstrates that the incorporation of the phenylethynyl group
occurs without migration of the phenyl group.
BzO
Ph
13C1
O
I
13C
Ph
PhCO2H (2a)
F3C
F3C
13C2
I
optimized
conditions
CF3
CF3
O
Ph
1
a-13
C
a-13C2, 93%
4
δ (C1) = 138.6, δ (C2) = 84.3
JC1–C2 = 116 Hz
1
3
Scheme 2. C-Labeling experiment.
[
7c]
As previously done for the 1,1-hydrocarboxylation,
the
Pd(II)-assisted 1,2-I(III) shift and the subsequent vinylidene
insertion into the Pd–carboxylate bond in the presence of L5
were probed by density functional theory (DFT) calculations
(
Figure 1). Pd(OAc)
2
, L5, and propynylbenziodoxole 1j form a π-
complex Int1. Though endergonic, Int1 undergoes 1,2-I(III) shift
–
1
via TS1 with a relatively small activation energy of 8.4 kcal mol
to generate a vinylidene–Pd(II) species Int2. While Int2 may
‡
–1
easily revert back to Int1 (ΔG = 1.7 kcal mol ), it can also
undergo vinylidene insertion into the Pd–OAc moiety via a five-
‡
–1
membered cyclic TS2 (ΔG = 4.4 kcal mol ) to give a more
stable β-iodo(III)alkenyl–Pd intermediate Int3. One of the distinct
structural features of the present reaction pathway can be found
in the "vinylidene" species Int2, where the I(III) center is almost
equally distant from the α- and β-carbons (2.6–2.7 Å). Thus, Int2
may also be regarded as an alkynyl–Pd species coordinated by
a cationic I(III) moiety, as pointed out in Ariafard's computational
Figure 1. (a) Energy profile of the 1,2-I(III) shift and the migratory insertion. (b)
DFT-optimized molecular structures. Color code: grey = C; white = H; purple =
I; blue = N; red = O; turquoise = Pd. Substituents of the benziodoxole moiety
are omitted for clarity (see the SI for computational details).
[
11,14]
Further DFT studies allowed us to identify a viable pathway
study on related systems.
for the conversion of Int3 into the carboxyalkynylation product
(
Scheme 3). The early stage of the pathway is mechanistically
analogous to the pathway for the conversion of Pd(L5)(OAc)
2
and 1j to Int3. Thus, a π-complex between Int3 and another
molecule of 1j (Int4) undergoes 1,2-I(III) shift to give a new
vinylidene/alkenyl–Pd species Int5, followed by insertion of the
vinylidene moiety into the Pd–alkenyl bond. The resulting
intermediate Int6, upon isomerization and incorporation of one
molecule of AcOH, gives a tetracoordinate 1,4-diiodo(III)dien-2-
yl–Pd species Int8, which then undergoes stepwise β-
elimination. Thus, the AcOH molecule initially assists cleavage
of the I–O bond of the benziodoxole moiety, and subsequent
cleavages of the C–I and C–Pd bonds affords the product
complex Int10, which comprises the 1,1-carboxyalkynylation
product,
Pd(L5)(OAc)
2
,
and
1,1,1,3,3,3-hexafluoro-2-(2-
iodophenyl)propan-2-ol. In addition to this reaction pathway, we
conceived two alternative pathways of alkynyl group transfer to
Int3, one involving oxidative addition of 1j to Int3 and the other
involving migratory insertion of 1j into the alkenyl–Pd bond of
Int3 (see the Supporting Information for detail). However, these
alternatives are considered less likely because of the high
instability of the putative Pd(IV) intermediate (for the former
1
3
pathway) or in light of the C-labeling experiment (Scheme 2,
for the latter pathway).
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Chemistry - A European Journal
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COMMUNICATION
IIII
BzO
Ph
AcO
Ph
Me
IIII
AcO
Me
OAc Me
ΔG‡ = 4.2
Int3 + 1j
IIII
a
b
c
IIII
Pd
Pd
Me
1,2-I(III)
shift
OAc
(0.0)
L5
OAc
L5
Ph
Ph
SiMe3
Ph
5, 82%
7, 95%
Int4 (–1.6)
Int5 (–2.2)
ΔG‡ = 10.1
vinylidene
insertion
AcO
Ph
RO
Ph
IIII
AcO
Ph
Me
Me
d
IIII
IIII
AcO
Me
Me
OAc
Me
OAc
L5
Me
Ph
Ph
OAc
IIII
Ph
+
AcOH
IIII
L5
OMe
Ph
IIII
Pd
IIII
8, 62%
Pd
L5 OAc
6, 90%
4a (R = Bz)
or 4b (R = Ac)
Pd
O
O
O
OAc
f
OH
Ph
HO
Me
Me
Int7 (–29.2)
e
Int6 (–26.9)
Ph
Int8 (–33.4)
AcO
Ph
(
R = Bz)
S
ΔG‡ = 12.5 I–O cleavage
9, 92%
IIII Me
OAc
Ph
10, 90%
Me
OMe
IIII
Me
I+
OAc
ΔG‡ = 6.9
Me
L5
L5
Scheme 4. Selected product transformations. Reaction conditions: (a)
PdCl (PhCN) , (CH =CH)SnBu , DMF, rt, 12 h; (b) Pd(OAc) , P(t-Bu) , 4-
MeOC B(OH) , LiOH, DME/H O, rt, 12 h; (c) PdCl (PPh , CuI, Et N,
trimethylsilylacetylene, DMF, rt, 12 h; (d) Pd(acac) , Zn, THF, 50 °C, 24 h; (e)
Na S•9H O, DMF/H O, rt, 2 h; (f) Ph PAuCl, AgSbF , CH Cl , rt, 20 min.
Pd
Pd–
β-elimination
O
2
2
2
3
2
3
I
OAc
OAc
O
H
)
6
4
2
2
2
3
2
3
O
O
Me
F3C
O
2
H
O
Me
H
CF3
F3C
CF3
2
2
2
3
6
2
2
Int9 (–21.7)
Int10 (–46.5)
Scheme
3.
Calculated
pathway
for
the
conversion
of
β-
In summary, we have developed a palladium-catalyzed 2:1
iodo(III)alkenylpalladium species Int3 into the carboxyalkynylation product.
coupling reaction between alkynylbenziodoxole and carboxylic
acid, which features a mechanistically unique 1,2-I(III) shift/1,1-
carboxyalkynylation sequence and affords a novel (alk-1-en-3-
ynyl)benziodoxole. Regardless of the high propensity of the
alkynylbenziodoxole toward decomposition in the presence of
(
Relative) free energies shown in the parentheses and above the arrows are
–1
given in kcal mol
.
The functionalized enyne products obtained by the present
reaction could be used as versatile building blocks for further
transformations, as demonstrated by selected follow-up
reactions of 4a and 4b (Scheme 4). Even in the sterically
demanding tetrasubstituted environment, the benziodoxole
moiety served as an excellent leaving group in Pd-catalyzed
Pd(II),
the
reaction
is
achieved
efficiently
using
octahydrophenazine as the supporting ligand. The origin of the
ligand effect on the reaction efficacy and the chemoselectivity
(
vs. 1,1-hydrocarboxylation) remains unclear and warrants
further experimental and theoretical studies. The alkynyl group
transfer initiated by 1,2-I(III) shift (Scheme 3) may deserve to be
considered as a mechanistic possibility in other transition metal-
[
15]
Stille, Suzuki–Miyaura, and Sonogashira couplings,
afforded stereochemically well-defined multisubstituted dienyne
, enyne 6, and endiyne 7, respectively, in high yields. Pd
which
catalyzed
alkynylations
employing
5
[
6a,11]
alkynylbenziodoxol(on)es.
Further application of the present
catalysis also allowed reductive homocoupling of 4b using Zn as
a reductant, affording dienediyne 8 in 62% yield. In addition,
exposure of 4a to sodium sulfide caused a thiolative cyclization,
iodo(III)enyne products to the synthesis of novel π-conjugated
compounds is also under investigation.
with
concomitant
debenzoylation,
to
produce
3-
hydroxythiophene derivative 9 in 92% yield. The Suzuki–Miyaura
[
16]
product 6 was amenable to gold-catalyzed cycloisomerization,
cleanly furnishing a benzofulvene derivative 10.
Acknowledgements
This work was funded by the Singapore Ministry of Education
(
Singapore) and Nanyang Technological University (RG 3/15).
We thank Drs. Rakesh Ganguly and Yongxin Li for their
assistance with the X-ray crystallography. H.H. thanks the High-
Performance Computing Centre of NTU for computer resources.
Keywords: hypervalent iodine • palladium • carboxylic acid •
alkynylation • cross-coupling
[
1]
a) A. Yoshimura, V. V. Zhdankin, Chem. Rev. 2016, 116, 3328-3435; b)
V. V. Zhdankin, P. J. Stang, Chem. Rev. 2008, 108, 5299-5358; c) Y. Li,
D. P. Hari, M. V. Vita, J. Waser, Angew. Chem. Int. Ed. 2016, 55, 4436-
4
454; d) J. Waser, Top. Curr. Chem. 2016, 373, 187-222; e) J. Waser,
Synlett 2016, 27, 2761-2773; f) J. P. Brand, D. F. Gonzalez, S. Nicolai,
This article is protected by copyright. All rights reserved.

Chemistry - A European Journal
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COMMUNICATION
J. Waser, Chem. Commun. 2011, 47, 102-115; g) L. F. Silva, B.
Olofsson, Nat. Prod. Rep. 2011, 28, 1722-1754; h) E. A. Merritt, B.
Olofsson, Angew. Chem. Int. Ed. 2009, 48, 9052-9070; i) T. Wirth,
Angew. Chem. Int. Ed. 2005, 44, 3656-3665.
[
2]
a) J. P. Brand, J. Waser, Chem. Soc. Rev. 2012, 41, 4165-4179; b) V.
V. Zhdankin, P. J. Stang, Tetrahedron 1998, 54, 10927-10966.
J. Kaschel, D. B. Werz, Angew. Chem. Int. Ed. 2015, 54, 8876-8878.
a) J. P. Brand, J. Charpentier, J. Waser, Angew. Chem. Int. Ed. 2009,
[
[
3]
4]
4
4
8, 9346-9349; b) J. P. Brand, J. Waser, Angew. Chem. Int. Ed. 2010,
9, 7304-7307; c) G. L. Tolnai, S. Ganss, J. P. Brand, J. Waser, Org.
Lett. 2013, 15, 112-115; d) K. D. Collins, F. Lied, F. Glorius, Chem.
Commun. 2014, 50, 4459-4461; e) C. Feng, T.-P. Loh, Angew. Chem.
Int. Ed. 2014, 53, 2722-2726; f) C. Feng, D. Feng, T.-P. Loh, Chem.
Commun. 2014, 50, 9865-9868; g) C. Feng, D. Feng, Y. Luo, T.-P. Loh,
Org. Lett. 2014, 16, 5956-5959; h) F. Xie, Z. Qi, S. Yu, X. Li, J. Am.
Chem. Soc. 2014, 136, 4780-4787; i) X. Zhang, Z. Qi, J. Gao, X. Li, Org.
Biomol. Chem. 2014, 12, 9329-9332; j) P. Finkbeiner, U. Kloeckner, B.
J. Nachtsheim, Angew. Chem. Int. Ed. 2015, 54, 4949-4952; k) H.
Wang, F. Xie, Z. S. Qi, X. Li, Org. Lett. 2015, 17, 920-923; l) Z.-Z.
Zhang, B. Liu, C.-Y. Wang, B.-F. Shi, Org. Lett. 2015, 17, 4094-4097.
a) X. Liu, Z. Wang, X. Cheng, C. Li, J. Am. Chem. Soc. 2012, 134,
[
5]
1
4330-14333; b) H. Huang, G. Zhang, L. Gong, S. Zhang, Y. Chen, J.
Am. Chem. Soc. 2014, 136, 2280-2283; c) H. Huang, G. Zhang, Y.
Chen, Angew. Chem. Int. Ed. 2015, 54, 7872-7876; d) F. Le Vaillant, T.
Courant, J. Waser, Angew. Chem. Int. Ed. 2015, 54, 11200-11204; e) H.
Wang, L.-N. Guo, S. Wang, X.-H. Duan, Org. Lett. 2015, 17, 3054-
3
057; f) Q.-Q. Zhou, W. Guo, W. Ding, X. Wu, X. Chen, L.-Q. Lu, W.-J.
Xiao, Angew. Chem. Int. Ed. 2015, 54, 11196-11199.
[
6]
a) S. Nicolai, S. Erard, D. F. Gonzalez, J. Waser, Org. Lett. 2010, 12,
3
1
84-387; b) Z. Wang, L. Li, Y. Huang, J. Am. Chem. Soc. 2014, 136,
2233-12236; c) D. F. Gonzalez, J. P. Brand, R. Mondiere, J. Waser,
Adv. Synth. Catal. 2013, 355, 1631-1639; d) X. Wu, S. Shirakawa, K.
Maruoka, Org. Biomol. Chem. 2014, 12, 5388-5392; e) R. Frei, M. D.
Wodrich, D. P. Hari, P. A. Bonin, C. Chauvier, J. Waser, J. Am. Chem.
Soc. 2014, 136, 16563-16573; f) M. D. Wodrich, P. Caramenti, J.
Waser, Org. Lett. 2016, 18, 60-63; g) Y. Li, J. Waser, Angew. Chem. Int.
Ed. 2015, 54, 5438-5442.
[
7]
a) B. Lu, J. Wu, N. Yoshikai, J. Am. Chem. Soc. 2014, 136, 11598-
1
1
2
1601; b) J. Wu, N. Yoshikai, Angew. Chem. Int. Ed. 2015, 54, 11107-
1111; c) J. Wu, X. Deng, H. Hirao, N. Yoshikai, J. Am. Chem. Soc.
016, 138, 9105-9108.
[
[
8]
9]
D. P. Hari, J. Waser, J. Am. Chem. Soc. 2016, 138, 2190-2193.
Z. Wang, X. Li, Y. Huang, Angew. Chem. Int. Ed. 2013, 52, 14219-
1
4223.
[
10] For a recent report on the synthesis of related alkenylbenziodoxolones,
see: Stridfeldt, E.; Seemann, A.; Bouma, M. J.; Dey, C.; Ertan, A.;
Olofsson, B. Chem. Eur. J. 2016, 22, 16066-16070.
[
[
[
11] A. Ariafard, Organometallics 2014, 33, 7318-7324.
12] T. Miura, N. Iwasawa, J. Am. Chem. Soc. 2002, 124, 518-519.
13] CCDC 1057849 (4a) and 1521973 (10) contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif.
[
[
[
14] A. Ariafard, ACS Catal. 2014, 4, 2896-2907.
15] N. R. Deprez, M. S. Sanford, Inorg. Chem. 2007, 46, 1924-1935.
16] V. Mamane, P. Hannen, A. Fürstner, Chem. Eur. J. 2004, 10, 4556-
4
575.
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Chemistry - A European Journal
10.1002/chem.201605772
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Junliang Wu, Kai Xu, Hajime Hirao,*
Naohiko Yoshikai*
Page No. – Page No.
Pd-Catalyzed, Ligand-Enabled
Stereoselective 1,2-Iodine(III)
Shift/1,1-Carboxyalkynylation of
Alkynylbenziodoxoles
A Pd(II)–octahydrophenazine catalyst promotes 2:1 coupling of alkynylbenziodoxole
with carboxylic acid. The reaction involves Pd(II)-assisted 1,2-iodine(III) shift of the
alkynylbenziodoxole followed by stereoselective introduction of carboxy and alkynyl
groups into the 1-position of the transient Pd–vinylidene species. The product of
this 1,1-carboxyalkynylation reaction serves as a novel functionalized enyne-type
building block for further synthetic transformations.
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