Preparation, structure, and versatile reactivity of pseudocyclic benziodoxole triflate, new hypervalent iodine reagent

Article abstract of DOI:10.1039/c5cc02009c

A new pseudocyclic triflate derivative of benziodoxole (IBA-OTf) was prepared and characterized by X-ray analysis. This highly electrophilic reagent readily reacts with various organic substrates to give the corresponding products in good yields. Furthermore, IBA-OTf can be used as a catalyst with m-chloroperoxybenzoic acid as the terminal oxidant. This journal is

Full text of DOI:10.1039/c5cc02009c

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: A. Yoshimura, K.
C. Nguyen, S. Klasen, A. Saito, V. N. Nemykin and V. V. Zhdankin, Chem. Commun., 2015, DOI:
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/chemcomm

Page 1 of 4
ChemComm
View Article Online
DOI: 10.1039/C5CC02009C
Journal Name
RSCPublishing
COMMUNICATION
Preparation, Structure, and Versatile Reactivity of
Pseudocyclic Benziodoxole Triflate, New Hypervalent
Iodine Reagent
Cite this: DOI: 10.1039/x0xx00000x
Akira Yoshimura,*a Khiem C. Nguyen,a Scott C. Klasen,a Akio Saito,b Victor N.
Nemykin,a and Viktor V. Zhdankin*a
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
www.rsc.org/
A new pseudocyclic triflate derivative of benziodoxole (IBA- is known that a coordinating substituent in the ortho-position of
OTf) was prepared and characterized by X-ray analysis. This organohypervalent iodine(III) reagents has a strong effect on
highly electrophilic reagent readily reacts with various physical properties and reactivity.6 In a ground-breaking
organic substrates to give the corresponding products in good research, Protasiewicz and co-workers have developed the
yields. Furthermore, IBA-OTf can be used as a catalyst with stable and soluble ortho-sulfonyl substituted iodosylbenzenes
m-chloroperoxybenzoic acid as the terminal oxidant.
and iminoiodanes, which possess improved reactivity toward
organic substrates.6a-c Recently, our group and other groups
have also reported the preparation and reactivity of ortho-
alkoxy substituted iodine(III) derivatives.6e-h Several examples
of hydroxy(aryl)iodonium species stabilized by inter- or
intramolecular interactions are known as useful electrophilic
oxidative reagents.7,8 In particular, Ochiai and co-workers
reported the complexes of hydroxy(phenyl)iodonium and
aqua(hydroxy)(phenyl)iodonium ions with 18C6 crown ether,
which reacted with nucleophiles to give the corresponding
products in good yields.7 Several hydroxy(aryliodonium)
derivatives with intramolecular interactions are also known.7
Wirth and co-workers have reported a-tosyloxylation reactions
In recent years, organohypervalent iodine compounds have
emerged as environmentally friendly and efficient reagents for
various synthetically useful oxidative transformations.1
Particularly important hypervalent iodine(III) reagents are
represented by 2-iodosylbenzoic acid (IBA)2a-e and
iodosylbenzene,2f-h which are commonly used as selective
oxidants. However, despite their importance, IBA and
iodosylbenzene are not perfect reagents and have a serious
drawback: they have low reactivity and are insoluble in
common organic solvents. The reactivity and solubility of these
reagents in principle can be improved by combining them with
a strong acid,3 and [hydroxy(tosyloxy)iodo]benzene (HTBI,
Koser’s reagent)4 is a particularly important example of an acid-
activated iodosylbenzene, PhIO•TsOH. Among these acid-
activated hypervalent iodine reagents, derivatives of triflic acid
(e.g., species 1-3, Scheme 1) have the highest reactivity;
however, these species in general cannot be isolated as
individual compounds and their practical application is limited
by low thermal stability and sensitivity to moisture.5
using
the
ortho
methoxymethyl-substituted
chiral
hydroxy(aryiodonium) tosylate.8a-c Legault and co-workers have
also described the α-tosyloxylation reaction using the ortho
substituted amido-substituted tosylates.8d
OTf
HO
I
OTf
I
O
TfO
I
I OTf
Previously,
Kitamura
and
co-workers
described
O
Ph Ph
[hydroxy(trifluoromethanesufonyloxy)]iodobenzene,
O
PhI(OH)OTf 1, generated from iodosylbenzene and
trifluoromethanesulfonic acid as an air sensitive and
hydroscopic compound, which readily self-condensed at room
temperature to give an iodonium salt because of the high
electrophilic reactivity.5a-d The other known triflic acid
derivatives, 2 (Zefirov’s reagent)5e-h and benziodoxole 3
(Scheme 1),5i-l are also known to be thermally unstable and
highly hydroscopic compounds.
In a search for a readily available and stable triflic acid-
activated hypervalent iodine reagent, we decided to investigate
the pseudocyclic ortho-substituted aryliodine(III) compounds. It
1
2
3
Scheme 1. Trifluoromethanesulfonic acid-activated hypervalent iodine reagents.
Herein, we report the first preparation, structural
investigation,
[hydroxy(trifluoromethanesufonyloxy)]iodobenzoic acid (IBA-
OTf), which is the first example of stable activated
hydroxy(aryiodonium) triflate species generated from 2-
iodosylbenzoic acid and trifluoromethanesulfonic acid.
and
versatile
reactivity
of
2-
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 1

ChemComm
Page 2 of 4
View Article Online
COMMUNICATION
Journal Name
DOI: 10.1039/C5CC02009C
2-[Hydroxy(trifluoromethanesufonyloxy)]iodobenzoic acid
was synthesized in good yield by treatment of 2-
4
iodosylbenzoic acid (1 equiv) with trifluoromethanesulfonic
acid (1.05 equiv) in methylene chloride for 2 hours at 0 °C
(Scheme 2).† The desired product was obtained as a white solid
after repeated decantation with hexane and diethyl ether at 0
°C. The triflate is soluble in methanol, and moderately soluble
in acetonitrile and acetone. No decomposition was detected
when triflate 4 was left standing at ambient temperature for one
week. The prepared product
4 was recrystallized from
acetonitrile-diethyl ether and characterized by single crystal X-
ray crystallography (Figure 1, see Supporting Information for
details).
OH
OH
_
Figure 2. Intermolecular interactions in X-ray crystal structure of compound 4.
+
I
I
OTf
0 °C, 2 h
CH2Cl2
+
TfOH
O
O
Structure of compound 4 in solution was supported by
electrospray ionization mass-spectrometry. The ESI-MS taken
in positive mode in methanol has demonstrated the presence of
molecular ion [ArIOH]+ at m/z 265 and the corresponding
ligand exchange ion [ArIOMe]+ at m/z 279 (see Supporting
Information for details).
The exceptional reactivity of IBA-OTf 4 as versatile
oxidizing reagent is summarized in Scheme 3. These reactions
illustrate the broad range of potential synthetic applications. In
general, the reactions of all organic nucleophiles with reagent 4
proceed at room temperature affording corresponding products
in moderate to good yields (Scheme 3).
The oxidation of sulfides or p-methyl phenol with 4
produced sulfoxides 5 and 6 in high yield or p-quinol 7 in
moderate yield, respectively. The oxidative rearrangement of a-
methyl styrene and chalcone afforded corresponding
compounds 8 and 9 in moderate yields. IBA-OTf 4 is an
efficient reagent for the preparation of heterocyclic compounds.
The reactions of aldoximes with IBA-OTf 4 in different nitrile
solvents at room temperature gave corresponding 1,2,4-
oxadiazoles 10-13 in good yields. The oxidative dimerization of
thiobenzamide using reagent 4 afforded the 3,5-diphenyl-1,2,4-
thiadiazole 14 in high yield. In the reaction with mesitylene,
diaryliodonuim triflate salt 15 was obtained in 89%. The
reaction of hexynyl trimethylsilane with 4 in the presence of
trifluoromethanesulfonic acid (1 equiv) led to vinyl iodonium
salt 16 in moderate yield. All these reactions proceeded
smoothly and did not require any further activation of reagent 4
by adding external acids. For comparison, in the reaction of
thioanisole or benzaldoxime with unactivated IBA under same
conditions, the desired products could not be detected and only
starting materials were recovered from reaction mixtures. All
reactions of IBA-OTf 4 (Scheme 3) give similar products as the
previously reported reagents,10 but proceed under milder
conditions.
O
OH
4, 93%
(1 equiv)
(1.05 equiv)
Scheme 2. Preparation of benziodoxole-based pseudo-cyclic triflate salt 4.
X-ray crystal data of triflate 4 (Figure 1) demonstrates the
presence of one short (~1.92 Å) iodine-oxygen covalent bond
and two relatively long (~2.34 and ~2.89 Å) dative contacts
between carboxylate O(2) and triflate O(4) oxygen atoms and
the iodine(III) center. Such molecular motif is close to the other
reported
hypervalent
iodine(III)
reagents.8a,c,9
The
intramolecular geometry around the iodine(III) center of
hydroxy(aryl)iodonium ion in 4 can be described as distorted T-
shaped with observed O(1)-I(1)-O(2) angle of ~167o. In the
solid state, this geometry, however, is augmented by an
additional intermolecular I(1)-O(4) ~2.89 Å contact, and thus it
can be considered as a pseudo square-planar coordination of the
I(III) center. The relatively weak intermolecular I(1)-O(4)
interaction is further stabilized by two intermolecular hydrogen
bonds. One of these bonds was observed between carboxylic
O(3)-H group of the parent ion 4 and O(6) atom of triflate and
is very strong (~1.8 Å, Figure 2). The second rather unusual
hydrogen bond was observed between hydroxyl O(1)-H group
and F(1) atom of triflate and is relatively weak (~2.5 Å, Figure
2). Both of these intermolecular contacts are responsible for
increased thermal stability of the compound 4, similarly with
the
hydrogen
bond
stabilization
observed
in
aqua(hydroxy)(phenyl)iodonium triflate.7b,c
In contrast to the common, iodobenzene-based hypervalent
iodine reagents, IBA-OTf 4 can be efficiently recovered from
the reaction mixture and recycled. The reduced form of IBA-
OTf, 2-iodobenzoic acid, can be easily recovered from the
reaction mixture in 97% yield by a simple acid-base liquid-
liquid biphasic protocol (see Supporting Information for
details). The recovered 2-iodobenzoic acid can be reoxidized to
2-iodosylbenzoic acid (IBA) using known procedures and then
IBA can be converted to IBA-OTf 4 by the treatment with
trifluoromethanesulfonic acid.
Figure 1. X-ray crystal structure of compound 4. Selected bond lengths and
angles: I(1)-O(2) 2.340(13); I(1)-C(1) 2.069(19); I(1)-O(1) 1.921(12); O(2)-C(7)
1.23(2); C(7)-O(3) 1.30(2); O(2)-I(1)-O(1) 166.8(5); O(2)-I(1)-C(1) 75.3(6); C(1)-I(1)-
O(1) 92.2(6).
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 3 of 4
Journal Name
ChemComm
View Article Online
COMMUNICATION
DOI: 10.1039/C5CC02009C
O
S
acid at room temperature for 24 hours, the desired product 10
was obtained in 83% (Scheme 4). For comparison, a similar
reaction catalyzed by iodobenzene instead of 2-iodobenzoic
acid under same condition, afforded product 10 in only 67%
yield. Reactions of several other aldoximes 17 selectively gave
corresponding oxadiazoles 19 under these conditions. It is
noteworthy that the reaction of cinnamaldehyde oxime under
these conditions afforded product 11 without cleavage of the
internal double bond. Reaction of propionitrile or benzonitrile
gave corresponding products 22 and 12 in moderate yields.
4 (1.2 equiv)
S
Ph
Me
MeCN, rt, 10 min
Ph
Me
(1 equiv)
5, 83 %
O
S
4 (1.2 equiv)
Me
OH
S
Me
O
MeCN, rt, 10 min
Cl
Cl
(1 equiv)
6, 91 %
Me
4 (1.2 equiv)
Me
MeCN-H2O (20:1),
0 °C to rt, 24 h
HO
7, 50 %
Me
(1 equiv)
Me
2-IC6H4CO2H (5 mol %)
TfOH (1.2 equiv), m-CPBA (1.2 equiv)
N
O
OH
+
R2CN
R1
N
4 (1.2 equiv)
rt, 24 h
R1
R2
Ph
N
Ph
O
MeOH-H2O (20:1),
rt, 24 h
17
18
19 (62-84%)
8, 59 %
(1 equiv)
N
O
O
OMe
N
O
N
O
O
4 (1.2 equiv)
Me
Me
Ph
Ph
Me
N
Ph
OMe
N
N
MeOH, rt, 24 h
Ph
Ph
Me
Cl
Ph
9, 62 %
10, 83%
20, 84%
21, 78%
(1 equiv)
N
O
4 (1.2 equiv)
N
O
N
O
N
O
OH
R1
N
R1
Me
MeCN, rt, 1 h
N
Me
Ph
N
Ph
Ph
Et
N
N
(1 equiv)
10, R1 =Ph, 90 %
11, 62%
22, 70%
12, 63%
11, R1
=
, 70 %
Ph
Scheme 4. Oxidative cyclization of aldoximes using catalytic IBA-OTf system.
N
O
4 (1.2 equiv)
OH
Ph
N
R2CN, rt, 1 h
Ph
R2
N
(1 equiv)
S
12, R2 = Ph, 86 %
13, R2 = CCl3, 67 %
Conclusions
In summary, we have prepared and characterized by single
crystal X-ray diffraction new benziodoxole triflate (IBA-OTf
N
S
4 (1.6 equiv)
Ph
Ph
Ph
NH2
MeCN, rt, 4 h
N
4),
the
first
example
of
a
stable,
activated
14, 80 %
(1 equiv)
Me
hydroxy(aryiodonium) triflate species generated from 2-
iodosylbenzoic acid and trifluoromethanesulfonic acid. This
highly electrophilic hypervalent iodine reagent readily reacts
with various nucleophilic organic substrates to give the
corresponding products of oxidation or iodonium salts in
moderate to good yields. Reagent 4 can be efficiently recycled
from reaction mixtures by a simple acid-base liquid-liquid
biphasic protocol followed by re-oxidation and treatment with
trifluoromethanesulfonic acid. Furthermore, IBA-OTf can be
used as an effective catalyst in oxidation reactions with m-
chloroperoxybenzoic acid as the terminal oxidant.
CO2H Me
+
4 (1 equiv)
I
-
OTf
TFE, rt, 24 h
Me
Me
Me
Me
(1 equiv)
15, 89 %
-
TfO
H
OTf
4 (1 equiv)
TfOH (1 equiv)
O
+
n-C4H9
I
OH
n-C4H9
TMS
CH2Cl2, rt, 24 h
(1 equiv)
16, 62 %
Scheme 3. Reactions of IBA-OTf 4 with organic nucleophiles.
Furthermore, IBA-OTf can be efficiently regenerated in situ Acknowledgements
from 2-iodobenzoic acid and terminal oxidant in the presence
This work was supported by a research grant from the National
of trifluoromethanesulfonic acid and thus used as a catalyst. In
particular, we were pleased to find that the oxidative
cycloaddition reaction of benzaldoxime with acetonitrile in the
presence of catalytic amounts of 2-iodobenzoic acid and
stoichiometric m-chloroperoxybenzoic acid (mCPBA) and
trifluoromethanesulfonic acid proceeds at room temperature
affording corresponding 1,2,4-oxadiazole 10 in good yield.
In a search for optimized conditions of the IBA-OTf-
catalyzed reactions of aldoximes 17 with nitriles 18 (Scheme
4), we performed several control experiments (see Supporting
Information for details). In the absence of 2-iodobenzoic acid or
trifluoromethanesulfonic acid, only trace amounts of 1,2,4-
oxadiazoles 19 were detected in the reaction mixture. However,
when benzaldoxime in acetonitrile solution was treated with
catalytic 2-iodobenzoic acid (5 mol %) and stoichiometric
mCPBA (1.2 equiv) in the presence of trifluoromethanesulfonic
Science Foundation (CHE-1262479).
Notes and references
a Department of Chemistry and Biochemistry, University of Minnesota
Duluth, Duluth, MN 55812, USA
Fax: +218-726-7394
E-mail: vzhdanki@d.umn.edu, ayoshimu@d.umn.edu
b Division of Applied Chemistry, Institute of Engineering, Tokyo
University of Agriculture and Technology
2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan
†
Electronic Supplementary Information (ESI) available: Detail
synthetic procedures, characterization data, NMR spectra, and
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 3

ChemComm
Page 4 of 4
View Article Online
COMMUNICATION
Journal Name
DOI: 10.1039/C5CC02009C
crystallographic data for compound
DOI: 10.1039/c000000x/
4
(CCDC-1047273). See
Hembre, C. P. Scott and J. R. Norton, J. Org. Chem., 1987, 52, 3650-
3654; g) J. Gallos, A. Varvoglis and N. W. Alcock, J. Chem. Soc.,
Perkin Trans. 1, 1985, 757-763; h) E. Kunst, F. Gallier, G. Dujardin
and A. Kirschning, Org. Biomol. Chem., 2008, 6, 893-898; i) V. V.
Zhdankin, C. J. Kuehl, J. T. Bolz, M. S. Formaneck and A. J.
Simonsen, Tetrahedron Lett., 1994, 35, 7323-7326; j) V. V.
Zhdankin, C. J. Kuehl, A. P. Krasutsky, J. T. Bolz and A. J.
Simonsen, J. Org. Chem., 1996, 61, 6547-6551; k) E. A. Merritt and
B. Olofsson, Eur. J. Org. Chem., 2011, 3690-3694; l) J. P. Brand, C.
Chevalley, R. Scopelliti and J. Waser, Chem.--Eur. J., 2012, 18,
5655-5666.
1
a) V. V. Zhdankin, in Hypervalent Iodine Chemistry: Preparation,
Structure and Synthetic Application of Polyvalent Iodine Compounds,
John Wiley & Sons Ltd, 2013, pp. i-viii; b) T. Wirth and Ed.,
Hypervalent Iodine Chemistry: Modern Developments in Organic
Synthesis. [In: Top. Curr. Chem., 2003; 224], 2003; c) F. V. Singh
and T. Wirth, Chem. - Asian J., 2014, 9, 950-971; d) M. Brown, U.
Farid and T. Wirth, Synlett, 2013, 24, 424-431; e) J. P. Brand and J.
Waser, Chem. Soc. Rev., 2012, 41, 4165-4179; f) M. S. Yusubov and
V. V. Zhdankin, Curr. Org. Synth., 2012, 9, 247-272; g) R. Samanta,
K. Matcha and A. P. Antonchick, Eur. J. Org. Chem., 2013, 5769-
5804; h) A. Parra and S. Reboredo, Chem. - Eur. J., 2013, 19, 17244-
17260; i) T. Dohi and Y. Kita, Chem. Commun., 2009, 2073-2085; j)
M. Uyanik and K. Ishihara, Chem. Commun., 2009, 2086-2099; k) R.
M. Romero, T. H. Woeste and K. Muniz, Chem. - Asian J., 2014, 9,
972-983; l) J. Charpentier, N. Fruh and A. Togni, Chem. Rev. 2015,
115, 650-682.
6
a) D. Macikenas, E. Skrzypczak-Jankun and J. D. Protasiewicz, J.
Am. Chem. Soc., 1999, 121, 7164-7165; b) D. Macikenas, E.
Skrzypczak-Jankun and J. D. Protasiewicz, Angew. Chem., Int. Ed.,
2000, 39, 2007-2010; c) B. V. Meprathu and J. D. Protasiewicz,
Tetrahedron, 2010, 66, 5768-5774; d) V. V. Zhdankin and J. D.
Protasiewicz, Coord. Chem. Rev., 2014, 275, 54-62; e) A.
Yoshimura, V. N. Nemykin and V. V. Zhdankin, Chem.--Eur. J.,
2011, 17, 10538-10541; f) C. Zhu, A. Yoshimura, L. Ji, Y. Wei, V.
N. Nemykin and V. V. Zhdankin, Org. Lett., 2012, 14, 3170-3173; g)
C. Zhu, A. Yoshimura, P. Solntsev, L. Ji, Y. Wei, V. N. Nemykin and
V. V. Zhdankin, Chem. Commun., 2012, 48, 10108-10110; h) D. J.
Hamnett and W. J. Moran, Org. Biomol. Chem., 2014, 12, 4156-
4162.
2
a) T. Kitamura, K. Nagata and H. Taniguchi, Tetrahedron Lett., 1995,
36, 1081-1084; b) T. Kitamura, T. Fukuoka and Y. Fujiwara, Synlett,
1996, 659-660; c) H. Huang, G. Zhang, L. Gong, S. Zhang and Y.
Chen, J. Am. Chem. Soc., 2014, 136, 2280-2283; d) M. Ochiai, A.
Nakanishi and T. Suefuji, Org. Lett., 2000, 2, 2923-2926; e) M. Xia
and Z. Chen, Synth. Commun., 2000, 30, 63-68; f) A. Saito, A.
Taniguchi, Y. Kambara and Y. Hanzawa, Org. Lett., 2013, 15, 2672-
2675; g) X. Liu, R. Cheng, F. Zhao, D. Zhang-Negrerie, Y. Du and
K. Zhao, Org. Lett., 2012, 14, 5480-5483; h) N. Havare and D. A.
Plattner, Org. Lett., 2012, 14, 5078-5081.
7
a) M. Ochiai, K. Miyamoto, M. Shiro, T. Ozawa and K. Yamaguchi,
J. Am. Chem. Soc., 2003, 125, 13006-13007; b) M. Ochiai, K.
Miyamoto, Y. Yokota, T. Suefuji and M. Shiro, Angew. Chem., Int.
Ed., 2005, 44, 75-78; c) M. Ochiai, Coord. Chem. Rev., 2006, 250,
2771-2781; d) K. Miyamoto, N. Tada and M. Ochiai, J. Am. Chem.
Soc., 2007, 129, 2772-2773; e) K. Miyamoto, M. Hirobe, M. Saito,
M. Shiro and M. Ochiai, Org. Lett., 2007, 9, 1995-1998; f) M. Saito,
K. Miyamoto and M. Ochiai, Chem. Commun., 2011, 47, 3410-3412;
g) K. Miyamoto, Y. Sei, K. Yamaguchi and M. Ochiai, J. Am. Chem.
Soc., 2009, 131, 1382-1383; h) K. Miyamoto, Y. Yokota, T. Suefuji,
K. Yamaguchi, T. Ozawa and M. Ochiai, Chem. - Eur. J., 2014, 20,
5447-5453.
3
a) V. V. Zhdankin, R. Tykwinski, M. Mullikin, B. Berglund, R.
Caple, N. S. Zefirov and A. S. Koz'min, J. Org. Chem., 1989, 54,
2605-2608; b) V. V. Zhdankin, R. Tykwinski, R. Caple, B. Berglund,
A. S. Koz'min and N. S. Zefirov, Tetrahedron Lett., 1988, 29, 3703-
3704; c) V. V. Zhdankin, R. Tykwinski, R. Caple, B. Berglund, A. S.
Koz'min and S. Zefirov, Tetrahedron Lett., 1988, 29, 3717-3720; d)
A. Saito, N. Hyodo and Y. Hanzawa, Molecules, 2012, 17, 11046-
11055; e) L. Mao, Y. Li, T. Xiong, K. Sun and Q. Zhang, J. Org.
Chem., 2013, 78, 733-737; f) T. Kitamura, S. Kuriki, K. Muta, M. H.
Morshed, K. Muta, K. Gondo, Y. Hori and M. Miyazaki, Synthesis,
2013, 45, 3125-3130; g) P. Gao, J. Liu and Y. Wei, Org. Lett., 2013,
15, 2872-2875; h) T. Kitamura, S. Kuriki, M. H. Morshed and Y.
Hori, Org. Lett., 2011, 13, 2392-2394.
8
a) U. H. Hirt, M. F. H. Schuster, A. N. French, O. G. Wiest and T.
Wirth, Eur. J. Org. Chem., 2001, 1569-1579; b) S. M. Altermann, R.
D. Richardson, T. K. Page, R. K. Schmidt, E. Holland, U.
Mohammed, S. M. Paradine, A. N. French, C. Richter, A. M. Bahar,
B. Witulski and T. Wirth, Eur. J. Org. Chem., 2008, 5315-5328; c) R.
D. Richardson, T. K. Page, S. Altermann, S. M. Paradine, A. N.
French and T. Wirth, Synlett, 2007, 538-542; d) A.-A. Guilbault and
C. Y. Legault, ACS Catal., 2012, 2, 219-222.
4
5
a) G. F. Koser, Aldrichimica Acta, 2001, 34, 89-102; b) G. F. Koser,
Adv. Heterocycl. Chem., 2004, 86, 225-292; c) H. Ghosh, A.
Baneerjee, S. K. Rout and B. K. Patel, ARKIVOC, 2011, 209-216; d)
L. Fra, A. Millan, J. A. Souto and K. Muniz, Angew. Chem., Int. Ed.,
2014, 53, 7349-7353; e) L. F. Silva, Jr., R. S. Vasconcelos and M. A.
Nogueira, Org. Lett., 2008, 10, 1017-1020.
9
a) G. F. Koser, R. H. Wettach, J. M. Troup and B. A. Frenz, J. Org.
Chem., 1976, 41, 3609-3611; b) A. Y. Koposov, D. N. Litvinov, V.
V. Zhdankin, M. J. Ferguson, R. McDonald and R. R. Tykwinski,
Eur. J. Org. Chem., 2006, 4791-4795; c) G. C. Geary, E. G. Hope, K.
Singh and A. M. Stuart, Chem. Commun, 2013, 49, 9263-9265.
a) T. Kitamura, K. Nagata, T. Nakamura, R. Furuki and H.
Taniguchi, Tetrahedron, 1995, 51, 6229-6236; b) T. Kitamura, L.
Zheng, T. Fukuoka, Y. Fujiwara, H. Taniguchi, M. Sakurai and R. 10 a) A.-u.-H. A. Shah, Z. A. Khan, N. Choudhary, C. Loholter, S.
Tanaka, J. Chem. Soc., Perkin Trans. 2, 1997, 1511-1515; c) T.
Kitamura, Yuki Gosei Kagaku Kyokaishi, 1995, 53, 893-905; d) T.
Kitamura, R. Furuki, H. Taniguchi and P. J. Stang, Tetrahedron,
1992, 48, 7149-7156; e) N. S. Zefirov, V. V. Zhdankin, Y. V.
Dan'kov, V. D. Sorokin, V. N. Semerikov, A. S. Koz'min, R. Caple
and B. A. Berglund, Tetrahedron Lett., 1986, 27, 3971-3974; f) R. T.
Schafer, G. P. L. Marie, U. Farooq, B. Witulski and T. Wirth, Org.
Lett., 2009, 11, 3578-3581; b) T. Dohi, M. Ito, K. Morimoto, Y.
Minamitsuji, N. Takenaga and Y. Kita, Chem. Commun., 2007, 4152-
4154; c) M. Bielawski and B. Olofsson, Chem. Commun., 2007,
2521-2523; d) M. J. Bouma and B. Olofsson, Chem. - Eur. J., 2012,
18, 14242-14245.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012