Oxidative diamination promoted by dinuclear iodine(III) reagents

Article abstract of DOI:10.1021/ol3034884

New dinuclear iodine(III) reagents for the intermolecular diamination of alkenes are reported. These are accessible through protolytic aminolysis events, which generate defined imido-iodine(III) groups.

Full text of DOI:10.1021/ol3034884

ORGANIC
LETTERS
2013
Vol. 15, No. 5
1008–1011
Oxidative Diamination Promoted
by Dinuclear Iodine(III) Reagents
†
Caren Roben, Jose A. Souto, Eduardo C. Escudero-Adan, and Kilian Muniz*
†
†
,†,‡
€
ꢀ
ꢀ
~
ICIQ - Institute of Chemical Research of Catalonia, Av. Paısos Catalans 16, 43007
¨
Tarragona, Spain, and ICREA - Catalan Institution for Research and Advanced Studies,
´
Pg. Lluıs Companys 23, 08010 Barcelona, Spain
kmuniz@iciq.es
Received December 20, 2012
ABSTRACT
New dinuclear iodine(III) reagents for the intermolecular diamination of alkenes are reported. These are accessible through protolytic aminolysis
events, which generate defined imido-iodine(III) groups.
The development of suitable hypervalent organoiodine-
(III) reactivity1 has recently greatly enhanced the area of
metal-free amination reactions. Several reports have detailed
electrophilic, radical, or nucleophilic amination reactions
based on these reagents.2ꢀ6 Within this context, we have
reported the synthesis, isolation, and structural character-
ization of defined reagents of the type ArI[N(SO2R)2]2 A
that show unprecedented reactivity in a series of different
† ICIQ.
(3) (a) Cho, S. H.; Yoon, J.; Chang, S. J. Am. Chem. Soc. 2011, 133,
5996. (b) Antonchick, A. P.; Samanta, R.; Kulikov, K.; Lategahn, J.
Angew. Chem., Int. Ed. 2011, 50, 8605. (c) Kim, H. J.; Kim, J.; Cho, S. H.;
Chang, S. J. Am. Chem. Soc. 2011, 133, 16382. (d) Kantak, A. A.;
Potavathri, S.; Barham, R. A.; Romano, K. M.; de-Boef, B. J. Am.
Chem. Soc. 2011, 133, 19960.
‡ ICREA.
(1) For recent reviews on iodine(III) chemistry, see: (a) Zhdankin,
V. V.; Stang, P. J. Chem. Rev. 2008, 108, 5299. (b) Zhdankin, V. V.;
Stang, P. J. Chem. Rev. 2002, 102, 2523. (c) Stang, P. J.; Zhdankin, V. V.
Chem. Rev. 1996, 96, 1123. (d) Dohi, T.; Kita, Y. Chem. Commun. 2009,
2073. (e) Uyanik, M.; Ishihara, K. Chem. Commun. 2009, 2086. (f)
Ngatimin, M.; Lupton, D. W. Aust. J. Chem. 2010, 63, 653. (g)
Zhdankin, V. V. ARKIVOC 2009, 1, 1. (h) Ciufolini, M. A.; Braun,
N. A.; Canesi, S.; Ousmer, M.; Chang, J.; Chai, D. Synthesis 2007, 3759.
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Maskaev, A. V.; Zhdankin, V. V. ARKIVOC 2011, 1, 370. (l) Zhdankin,
V. V.; Stang, P. J. Tetrahedron 1998, 54, 10927.
€
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Muniz, K. Angew. Chem., Int. Ed. 2011, 50, 9478. (b) Souto, J. A.;
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Gonzalez, Y.; Iglesias, A.; Zian, D.; Lishchynskyi, A.; Muniz, K.
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Chem.;Asian J. 2012, 7, 1103. (c) Lishchynskyi, A.; Muniz, K.
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Chem.;Eur. J. 2012, 18, 2213. (d) Souto, J. A.; Zian, D.; Muniz, K.
J. Am. Chem. Soc. 2012, 134, 7242. (e) Souto, J. A.; Becker, P.; Iglesias,
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A.; Muniz, K. J. Am. Chem. Soc. 2012, 134, 15505.
(5) Other iodine(III)-mediated intermolecular amination reactions of
alkenes: (a) Karina, D.; Dodd, R. H. Curr. Org. Synth. 2011, 15, 1507.
(b) Yoshimura, A.; Nemykin, V. N.; Zhdankin, V. V. Chem.;Eur. J.
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K.; Kaneaki, T.; Hayashi, S.; Nakanishi, W. Science 2011, 332, 448. (b)
Ochiai, M.; Kaneaki, T.; Tada, N.; Miyamoto, K.; Chuman, H.; Shiro,
M.; Hayashi, S.; Nakanishi, W. J. Am. Chem. Soc. 2007, 129, 12938.
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r
10.1021/ol3034884
Published on Web 02/12/2013
2013 American Chemical Society

oxidative amination reactions.7 These compounds all derive
from the general aryl iodine(III) theme. While this chemistry
now appears to be well-understood, future developments
require more diversification in structure. For example, a
recent report on the CꢀH amination of arenes by Antonchick
postulated the in situ formation of an IꢀN bond in the
dinuclear reagent B (Figure 1).8
Scheme 1. Synthesis of New Imido-Iodine(III) Compoundsa
Figure 1. Hypervalent iodine reagents.
a (a) (1) nBuLi, Et2O, ꢀ78 °C; (2) I2, ꢀ78 °C to rt (91% over both
steps). (b) Selectfluor, AcOH/CH3CN, rt (90%). (c) HNTs2 (2 equiv),
C6H5Cl/CHCl3, 50 °C (99%). (d) HNTs2 (2 equiv), C6H5Cl/CHCl3, rt
(99%). (e) HNTs2 (4 equiv), C6H5Cl/CHCl3, rt (99%).
We here describe two new hypervalent iodine reagents
based on the 2,20-diiodo biaryl core that provide an efficient
entry into metal-free diamination reactions.9ꢀ12 Starting
from 2,20-dibromo biphenyl 1, a halide exchange provides
2,20-diiodo biphenyl 2, which can be oxidized to the known
μ-oxo bridged bisiodone(III) compound 3 (Scheme 1).13
This compound serves as the source for selective trans-
formation into defined hypervalent imidoiodine(III) deriv-
atives with IꢀN single bonds. For example, in the presence
of 2 equiv of bistosylimide, 3 generates the new μ-oxo
bridged symmetric bisimido compound 4. The synthesis
of 4 within a direct aminolysis of precursor 3 under preserv-
ation of the μ-oxo group is unprecedented. It confirms
that the formation of postulated intermediates such as B
from their respective oxygenated precursors is indeed a
feasible process. The solid state structure of 4 is depicted in
Figure 2.14
Aminolysis with a 4-fold excess of imine directly gen-
erates the deoxygenated compound 5 displaying two in-
dividual bisimidoiodine(III) groups. The same product is
accessible through aminolysis of 4. The isolation of 5 with
its two bisimidoiodine(III) groups ArI(NTs2)2 confirms
the general implication of the latter as the reactive reagents
in metal-free oxidative diamination reactions.
~
´
(7) Souto, J. A.; Martınez, C.; Velilla, I.; Muniz, K. Angew. Chem.,
Int. Ed. 2013, 52, 1324.
(8) Samanta, R.; Bauer, J. O.; Strohmann, C.; Antonchick, A. P. Org.
Lett. 2012, 14, 5518.
(9) Reviews: (a) De Jong, S.; Nosal, D. G.; Wardrop, D. J. Tetra-
hedron 2012, 68, 4067. (b) de Figueiredo, R. M. Angew. Chem., Int. Ed.
2009, 48, 1190. (c) Cardona, F.; Goti, A. Nat. Chem. 2009, 1, 269. (d)
~
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Muniz, K.; Hovelmann, C. H.; Streuff, J.; Campos-Gomez, E. Pure
Appl. Chem. 2008, 80, 1089.
(10) For Pd-catalyzed diamination of alkenes under entirely inter-
ꢀ
~
molecular control: (a) Iglesias, A.; Perez, E. G.; Muniz, K. Angew.
~
Chem., Int. Ed. 2010, 49, 8109. (b) Martınez, C.; Muniz, K. Angew.
´
~
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Chem., Int. Ed. 2012, 51, 7031. (c) Muniz, K.; Kirsch, J.; Chavez, P. Adv.
Synth. Catal. 2011, 353, 689.
(11) For a Br-catalyzed diamination: Chavez, P.; Kirsch, J.;
€
ꢀ
Hovelmann, C. H.; Streuff, J.; Martınez-Belmonte, M.; Escudero-Adan,
´
~
E. C.; Martin, E.; Muniz, K. Chem. Sci. 2012, 3, 2375.
(12) For stoichiometric intramolecular diamination with iodine-
based oxidants: (a) Lavilla, R.; Kumar, R.; Coll, O.; Masdeu, C.; Bosch,
J. Chem. Commun. 1998, 2715. (b) Lavilla, R.; Kumar, R.; Coll, O.;
Masdeu, C.; Spada, A.; Bosch, J.; Espinosa, E.; Mollins, E. Chem.;Eur.
J. 2000, 6, 1763. (c) Kumar, V.; Ramesh, N. G. Chem. Commun. 2006,
Figure 2. Solid state structure of 4. Selected bond lengths (A) and
angles (deg): N1ꢀI1, 2.421(3); N2ꢀI2, 2.365(3); O1ꢀI2ꢀN2,
176.41(10); O1ꢀI1ꢀN1, 173.93(10).
~
€
ꢀ
4952. (d) Muniz, K.; Hovelmann, C. H.; Campos-Gomez, E.; Barluenga,
ꢀ
J.; Gonzalez, J. M.; Streuff, J.; Nieger, M. Chem.;Asian J. 2008, 3, 776.
(e) Farid, U.; Wirth, T. Angew. Chem., Int. Ed. 2012, 51, 3462.
(f) Kim, H. J.; Cho, S. H.; Chang, S. Org. Lett. 2012, 14, 1424. (g)
€
€
Muller, C. H.; Frohlich, R.; Daniliuc, C. G.; Hennecke, U. Org. Lett.
2012, 14, 5944.
(13) Kita, Y.; Dohi, T. Jpn. Kokai Tokkyo Koho (2012), JP
2012051846 A 20120315.
(14) See Supporting Information for details on the structural
elucidation.
Org. Lett., Vol. 15, No. 5, 2013
1009

Table 1. Diamination of Styrene with Iodine(III) Reagents 3, 4,
and 5: Optimizationa
Table 2. Diamination of Alkenes with Iodine(III) Reagents
4/2HNTs2 or 5a
entry
reagent combination
yield [%]b
1
2
3
4
5
6
7
8
9
3 (0.6 equiv) þ HNTs2 (1.2 equiv)
3 (1.2 equiv) þ HNTs2 (2.4 equiv)
3 (0.6 equiv) þ HNTs2 (2.4 equiv)
4 (0.6 equiv)
20c
43c
32c
54
4 (1.2 equiv)
88
4 (0.6 equiv) þ HNTs2 (1.2 equiv)
4 (0.6 equiv) þ HNTs2 (2.4 equiv)
5 (0.6 equiv)
74
74
77
5 (1.0 equiv)
92
a Reactions were performed on a 0.2ꢀ0.5 mmol scale. b Isolated yield
of product after purification on silica gel. c Major amounts of unreacted
styrene according to analysis by 1H NMR of the crude reaction.
The new compounds are active reagents for the intermo-
lecular diamination of alkenes or suitable precursors to these
reagents. As demonstrated for the diamination of styrene,
both an in situ reagent formation from 3 or 4 as well as use of
preformed 4 or 5 lead to chemoselective diamination in all
cases (Table 1). For example, treatment of styrene in dichlor-
omethane solution with 0.6 equiv of reagent 3 (1.2 equiv of
I(III)) and 1.2 equiv of bistosylimide already leads to forma-
tion of 20% diamination product 7a (entry 1). Doubling the
reagent amount to 1.2 equiv gives a 43% isolated yield (entry
2), while doubling the relative amount of imide provides an
increase in yield to 32% (entry 3). Use of preformed imido
compounds resulted in superior performances. For example,
a diamination with 0.6 equiv of 4led to a yield of 54% (out of
a maximum 60% yield, entry 4), while an excess of iodine(III)
in the same reaction provided an 88% yield (entry 5). These
observations demonstrate that efficient diamination can
already be accomplished with reagent 4. We rationalize this
behavior by the assumption of an intramolecular rearrange-
ment of 4. Upon dissociation of bistosylimide, the resulting
cationic intermediate 40 undergoes opening of the μ-oxo
bridge to form a iodoso group and the reactive ArI(NTs2)2
unit7 that initiates the diamination reaction (Scheme 2).
a Reaction conditions: alkene (0.5 mmol), oxidant 5 (0.6 mmol), or
combinations of reagents 3 or 4 as indicated, CH2Cl2, rt, 18 h. b Isolated
yield of product after purification on silica gel. c Reaction at 50 °C.
that treatment of 4 with an additional amount of bistosyli-
mide results in formation of 7a in 74% yield (Table 1, entry
6), while further addition of imide does not affect the yield
(entry 7). The results from entries 3 and 6 suggest compound
5 as the reactive reagent in the diamination of styrene, and
indeed, oxidation with preformed reagent 5gives diamine 7a
in 77% isolated yield (entry 8). This yield can be increased to
an excellent 92% using an excess of reagent 5 (entry 9).
Inspection of the reaction progress over time for a di-
amination of styrene with 5 as the reagent reveals a signifi-
cant decrease in relative rate taking place after around 50%
conversion, which was estimated to be in the range of a
6-fold overall drop.14 This rate decrease suggests that the
reaction is faster for oxidation with 5 than for the resulting
intermediate mixed species bearing an iodine(I) and an
iodine(III) group, which may be the result of a diminished
Scheme 2. Proposed Formation of ArI(NTs2)2 Reagent 400 from 4
That an ArI(NTs2)2 moiety indeed constitutes the reac-
tive iodine(III) reagent was concluded from the observation
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Org. Lett., Vol. 15, No. 5, 2013

In addition to diamination with 3/4HNTs2, a diamina-
tion starting from the related binaphthyl derivative 8
allowed for the exploration of the present type of reagents
in enantioselective diamination of styrene (Scheme 3).4a
Hence, in situ protolytic aminolysis of 8 by 4 equiv of
bissulfonimide generates an active reagent that has so far
escaped isolation but is considered to be the analogue of 5.
This chiral reagent is capable of inducing enantioselectivity
in the diamination of styrene. Values of 14 and 32% ee were
observed depending on the respective nitrogen source.
Although the obtained enantioselectivities are not yet high,
the reaction nevertheless demonstrates that the axially chiral
binaphthyl scaffold is capable of inducing enantioselectivity.
In summary, we have described the synthesis of new
dinuclear iodine(III) compounds with a defined structure
and have explored their reactivity in intermolecular di-
amination reactions of alkenes. The reactivity of these new
reagents is high and should result in the development of
new efficient amination reactions. It bears significant
potential for the development of enantioselective transfor-
mations as well.
Scheme 3. Enantioselective Diamination of Styrenea
aIsolated yield of product after purification on silica gel. bValue
determined by HPLC on a chiral stationary phase.
electrophilic character for the remaining iodine(III) group.
Still, the reaction with 0.6 equiv of 5 reaches yields that are
comparable to diamination with stoichiometric amounts of
the so far best reagent PhI(NTs2)2.7 However, it must be
noted that significantly longer reaction times are required in
the present cases.
Acknowledgment. C.R. gratefully acknowledges the
Alexander von Humboldt Foundation for a postdoctoral
fellowship (2010/2011). This work was supported by the
´
ICIQ Foundation and by the Spanish Ministerio de Economıa
y Competitividad (CTQ2011-25027).
Diamination reactions of alkenes using reagents 4 and
5 proceed with excellent results for a variety of different
alkenes. Table 2 shows representative examples. These in-
clude styrenes as the priviledged substrates in such oxidations
(entries 1, 2).4a,b In contrast to para- and meta-substitution,
ortho-substituents such as methyl or fluoro were found to be
incompatible with the present protocol. This is probably the
consequence of the enhanced size of reagent 5. Internal
alkenes such as β-methyl styrene and stilbene work well
(entries 3, 4) as do aliphatic alkenes such as 1- and 2-octene
(entries 5, 6).4b New reagent 5 also promotes diamination of
1-phenyl butadiene (entry 7),4c while cyclohexene gives
selective allylic amination (62% isolated yield).4d
Supporting Information Available. Experimental pro-
cedures and characterization data including CIF file on
the X-ray crystallographic analysis of compound 4. This
material is available free of charge via the Internet at
http://pubs.acs.org.
The authors declare no competing financial interest.
Org. Lett., Vol. 15, No. 5, 2013
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