DOI: 10.1002/chem.201102265
o-Alkoxyphenyliminoiodanes: Highly Efficient Reagents for the Catalytic
Aziridination of Alkenes and the Metal-Free Amination of Organic
Substrates
Akira Yoshimura, Victor N. Nemykin,* and Viktor V. Zhdankin*[a]
Within the rapidly growing field of hypervalent iodine
chemistry,[1] iminoiodanes occupy a special and important
place. N-Tosyliminoiodanes, ArINTs, have found a broad
range of synthetic applications as useful nitrene precursors
under thermal or catalytic conditions in the aziridination of
alkenes and the amidation reactions of various organic sub-
strates.[1d,e,2] Representative recent examples of the synthetic
use of PhINTs include the highly efficient RuII- or CuI-cata-
trene precursors 3, which are derived from ortho-alkoxyio-
dobenzenes. The choice of this structural motif is based on
our previous observation that the presence of an ortho-
alkoxy group in iodine(V) derivatives leads to the replace-
ment of the intermolecular I···O secondary bonds with intra-
molecular I···O bonds and results in a significant improve-
ment in the solubility of iodylarenes, ArIO2.[5]
o-Alkoxyphenyliminoiodanes 3a–d were synthesized in
two simple steps starting from readily available 2-iodophe-
nol ethers 1a–d (Scheme 1). In the first step, iodides 1 were
oxidized by peracetic acid to form diacetoxyiodo derivatives
2; the structures of products 2a and d were established by
X-ray analysis.[6] In the second step, diacetates 2 were con-
verted to iminoiodanes 3 by treatment with tosylamide
under basic conditions, in methanol.
[2a,b]
À
lyzed C H-bond amidation of aldehydes,
the gold-cata-
[2c,d]
À
lyzed nitrene transfer and C H insertion reactions,
the
À
silver-catalyzed C H insertion and aziridination reaction-
s,[2e,f] and numerous asymmetric aziridinations of alkenes by
using copper catalysts with chiral dinitrogen ligands.[2g–l]
However, despite its importance, PhINTs is not a perfect re-
agent and has a serious drawback: it is insoluble in most or-
ganic solvents due to its strong intermolecular secondary
bonding that creates a three-dimensional polymeric structur-
e.[1d,e,3a–c] Several research groups have tried to improve the
synthetic potential of iminoiodanes by developing new re-
agents or reagent combinations.[1e,3d–h] A particularly fruitful
approach to soluble iminoiodanes is based on the placement
of an ortho-tert-butylsulfonyl group onto the iodobenzene
ring of the parent PhINTs.[3d–f] Thus, several ArINTs (Ar=
2-tBuSO2C6H4, 2-tBuSO2-5-tBuC6H3, and 2-tBuSO2-4-
CF3C6H3) have been synthesized and utilized as soluble ni-
trene precursors, the reactivity of which is similar to the
parent PhINTs. The solubility of these reagents is explained
by the presence of intramolecular I···O secondary bonds due
to the ortho-sulfonyl substituent, which redirects the inter-
molecular I···O and I···N secondary bonds responsible for
the polymeric structure of PhINTs.[3d–f] These soluble nitrene
precursors have proved to be useful reagents;[3d–f,4] however,
their preparation requires four to seven synthetic steps and
their reactivity does not show any improvement relative to
PhINTs.
Scheme 1. Preparation of o-alkoxyphenyliminoiodanes 3a–d (Ts=tosyl).
Products 3 precipitated from the reaction mixture and
were isolated in good yields in analytically pure form as
yellow microcrystalline solids by filtration followed by wash-
ing with hexane and drying in a vacuum. Compounds 3 are
relatively stable at room temperature and can be stored for
several weeks in a refrigerator. Products 3a–d have good
solubility in dichloromethane, chloroform, and acetonitrile
(e.g., the solubility of 3b in dichloromethane is 0.25 gmLÀ1).
All products were identified by NMR spectroscopy and ele-
mental analysis, and the structures of 3a and c were charac-
terized by single crystal X-ray crystallography.[6]
Herein, we report the preparation, structural investiga-
tion, and reactivity of new highly soluble and reactive ni-
The X-ray crystal structure of 3a, showing intra- and in-
termolecular interactions with the hypervalent iodine
center, is given in Figure 1a. Similar to the structure of
PhINTs (Figure 1b),[3b] molecules of 3a have a polymeric,
asymmetrically bridged structure with a T-shaped geometry
around the iodine centers formed by two iodine–nitrogen
bonds and one iodine–carbon bond. However, in contrast to
PhINTs, compound 3a has two additional weak intra- and
[a] Dr. A. Yoshimura, Prof. Dr. V. N. Nemykin, Prof. Dr. V. V. Zhdankin
Department of Chemistry and Biochemistry
University of Minnesota Duluth, Duluth, MN 55812 (USA)
Fax : (+1)218-726-7394
Supporting information for this article is available on the WWW
10538
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Chem. Eur. J. 2011, 17, 10538 – 10541