Angewandte
Communications
Chemie
Oxidation
Structurally Defined Molecular Hypervalent Iodine Catalysts for
Intermolecular Enantioselective Reactions
Stefan Haubenreisser, Thorsten H. Wçste, Claudio Martínez, Kazuaki Ishihara, and
Kilian MuÇiz*
Abstract: Molecular structures of the most prominent chiral
non-racemic hypervalent iodine(III) reagents to date have been
elucidated for the first time. The formation of a chirally
induced supramolecular scaffold based on a selective hydro-
gen-bonding arrangement provides an explanation for the
consistently high asymmetric induction with these reagents. As
an exploratory example, their scope as chiral catalysts was
extended to the enantioselective dioxygenation of alkenes. A
series of terminal styrenes are converted into the corresponding
vicinal diacetoxylation products under mild conditions and
provide the proof of principle for a truly intermolecular
asymmetric alkene oxidation under iodine(I/III) catalysis.
of these compounds is notably missing. A definite under-
standing of the mode of action of chiral hypervalent iodine
reagents can form the basis to enlarge the differentiation of
prochiral face recognition from the established intramolecu-
lar reaction control to more challenging topics, such as the
asymmetric oxidation of prochiral substrates by intermolec-
ular reaction control, and particularly in terms of catalysis.
Within this context, no definite mechanistic investigation has
so far been reported for the parent iodine(III) reagents 1 and
2a bearing lactic esters and amides as chiral entities
(Figure 1).[11,12] Regarding the important iodine 2a, structural
E
nantioselective catalysis has been recognized as a core
technology toward the supply of chiral molecular entities with
defined absolute configuration. Different methods have been
devised over past decades and synthetic molecular catalysts
based on transition-metal complexes[1] or small organic
compounds[2] represent the most advanced concepts in the
field.[3] Within the context of small organic catalysts, chiral
hypervalent iodine reagents have enabled the development of
significant advances in catalytic oxidation reactions that do
not rely on common transition metals.[4,5] Examples include
the ester derivative 1[6,7] and the amide derivative 2a,[8,9]
which has been identified as a particularly successful reagent.
In contrast to the rapidly growing number of successful
examples of chiral molecular iodine(I/III) catalysts,[5,6,10]
defined structural information on the accurate enantiocontrol
Figure 1. Representative chiral iodine reagents 1 and 2a and success-
ful enantioselective intramolecular reactions with 2a.
information could now be obtained for the derivatives 2b and
2c, which contain sterically enlarged anilide groups. As
unambiguously determined by X-ray analyses (Figure 2) for
both compounds, the amide NH groups engage in hydrogen
bonding with the acetoxy groups located at the iodine
center.[13a] These hydrogen bonds have the expected values
for NH–O contacts of 2.201 and 2.243 , and for N-H-O bond
angles of 163.3 and 160.08,[13a] and generate two nine-
membered rings.[14,15]
[*] Dr. S. Haubenreisser, Dr. T. H. Wçste, Dr. C. Martínez,
Prof. Dr. K. MuÇiz
Institute of Chemical Research of Catalonia (ICIQ)
The Barcelona Institute of Science and Technology
Av. Països Catalans 16, 43007 Tarragona (Spain)
E-mail: kmuniz@iciq.es
Prof. Dr. K. Ishihara
Graduate School of Engineering, Nagoya University
B2-3(611), Furo-cho, Chikusa, Nagoya 464-8603 (Japan)
Prof. Dr. K. MuÇiz
Catalan Institution for Research and Advanced Studies (ICREA)
Pg. Lluís Companys 23, 08010 Barcelona (Spain)
Supporting information and ORCID(s) from the author(s) for this
ꢀ 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co.
KGaA. This is an open access article under the terms of the Creative
Commons Attribution Non-Commercial NoDerivs License, which
permits use and distribution in any medium, provided the original
work is properly cited, the use is non-commercial and no modifica-
tions or adaptations are made.
Figure 2. Intramolecular hydrogen-bonding properties of chiral hyper-
valent iodine compounds 2b (Ar=2,4,6-iPr3C6H2) and 2c (Ar=2,6-
iPr2C6H3). All hydrogen atoms except the N-H groups are omitted for
clarity.
Angew. Chem. Int. Ed. 2016, 55, 413 –417
ꢀ 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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