DOI: 10.1002/chem.201504636
Communication
&
Amination
Thioamination of Alkenes with Hypervalent Iodine Reagents
[
a]
[a]
[a]
[a, b]
and
[
a]
3
a sp -hybridized carbon atom (Scheme 1). The iodine(III)
moiety is an excellent leaving group, several orders of magni-
tude more reactive than triflates or tosylates. This leaving
group can be easily replaced with a second nucleophile to
give 1,2-difunctionalized reaction products. The use of
a second, external nucleophile, such as oxygen or nitrogen,
has already been reported. By introducing sulfur nucleophiles
as thiolates, direct thioaminations are possible.
Abstract: An efficient thioamination of alkenes mediated
by iodine(III) reagents is described. The use of different
sulfur nucleophiles allows the flexible synthesis of 1,2-ami-
nothiols from alkenes. By employing chiral iodine(III) re-
agents, a stereoselective version of the thioamination pro-
tocol has also been developed.
Organic compounds containing sulfur and nitrogen heteroa-
toms are important building blocks for a board range of com-
pounds with applications in biological, pharmaceutical, and
material science. This continuous demand has encouraged the
development of mild, safe, and highly selective procedures for
their synthesis. Hypervalent iodine reagents are effective non-
[
1,2]
metallic reagents
that have found many applications as
[3]
[4]
highly selective oxidants and as electrophilic reagents for
[5]
various reactions, including rearrangements and a-functional-
[
6]
izations of ketones. Taking into consideration our previous
[
7]
work on hypervalent iodine reagents and organocatalysis, we
describe here a stereoselective and efficient procedure for the
oxidative thioamination of alkenes.
Oxidative addition reactions to alkenes have been described
in many publications, but methods involving the simultaneous
addition of two different nucleophiles, such as nitrogen and
sulfur, are rare. Denmark et al. recently developed efficient thi-
oaminations based on sulfur electrophiles using chiral cata-
Scheme 1. Strategies for thioaminations.
Direct thioaminations are very rare, as the alkene-activating
reagent can directly react and oxidize the sulfur nucleophile.
[
8]
[9]
lysts. The activation of the double bond with a hypervalent
iodine reagent as electrophilic reagent is an alternative strat-
egy, and a subsequent reaction with the first nucleophile leads
to an intermediate, where the iodine(III) moiety is attached to
Thiourea moieties have been used as nucleophiles and, more
[
10]
recently, sulfilimines in reactions with alkynes. Even mild oxi-
dants, such as iodine(III) reagents, can react with sulfur deriva-
[
11]
tives. Due to the thiophilic nature of hypervalent iodine re-
agents, different hypervalent reagents had to be screened, as
the reagent should efficiently activate the alkene rather than
react directly with the sulfur nucleophile. In order to evaluate
hypervalent reagents and their reaction conditions for thioami-
nations, the reaction of 2-allyl aniline derivatives 1 with hyper-
valent iodine reagents under different reaction conditions in
the presence of sodium thiophenolate was investigated as
shown in Table 1.
[
a] Dr. P. Mizar, R. Niebuhr, M. Hutchings, Prof. Dr. U. Farooq, Prof. Dr. T. Wirth
School of Chemistry
Cardiff University
Park Place, Main Building, Cardiff CF10 3AT (UK)
Fax: (+44)29-2087-6968
E-mail: wirth@cf.ac.uk
Homepage: http://www.cf.ac.uk/chemy/wirth
[
b] Prof. Dr. U. Farooq
Initially, different hypervalent iodine reagents were screened
using 2-allyl-N-substituted anilines 1 as substrates at tempera-
tures ranging from À75 to 208C in various solvents. With (diac-
etoxyiodo)benzene (Table 1, entry 1) and the Koser reagent
Department of Chemistry
COMSATS Institute of Information Technology
Abbottabad (Pakistan)
(
PhI(OH)OTs; entry 2), the reactions either did not proceed or
ꢀ
2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
the yields were very low, irrespective of the solvent used. How-
ever, the use of [bis(trifluoroacetoxy)iodo]benzene as iodine(III)
reagent yielded the thioaminated product in moderate yield
This is an open access article under the terms of the Creative Commons At-
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medium, provided the original work is properly cited.
Chem. Eur. J. 2016, 22, 1614 – 1617
1614 ꢀ 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim