A versatile metal-free intermolecular aminochlorination of alkenes

Article abstract of DOI:10.1002/adsc.201300880

New reaction conditions for the rapid and productive intermolecular aminochlorination reaction of alkenes using a combination of chloramine-T and a Br?nstedt acid are described. Upon simple protonation of chloramine-T, conditions for a mild and selective aminochlorination are obtained. In addition, the reaction can proceed to form either of the two possible regioisomers, depending on whether a stoichiometric amount of such an acid activator or acetic acid is used as solvent. The reaction is operative for all different classes of alkenes. A total of over 50 examples is presented to illustrate this concept.

Full text of DOI:10.1002/adsc.201300880

FULL PAPERS
DOI: 10.1002/adsc.201300880
AVersatile Metal-Free Intermolecular Aminochlorination of
Alkenes
Claudio Martꢀneza and Kilian MuÇiza,b,*
a
Institute of Chemical Research of Catalonia (ICIQ), Av. Paꢁsos Catalans 16, 43007 Tarragona, Spain
Fax : (+34)-977-920-224; phone: (+34)-977-920-200; e-mail: kmuniz@iciq.es
Catalan Institution for Research and Advanced Studies (ICREA), Pg. Lluꢀs Companys 23, 08010 Barcelona, Spain
b
Received: September 30, 2013; Published online: January 10, 2014
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300880.
Abstract: New reaction conditions for the rapid and a stoichiometric amount of such an acid activator or
productive intermolecular aminochlorination reac- acetic acid is used as solvent. The reaction is opera-
tion of alkenes using a combination of chloramine-T tive for all different classes of alkenes. A total of
and a Brønstedt acid are described. Upon simple over 50 examples is presented to illustrate this con-
protonation of chloramine-T, conditions for a mild cept.
and selective aminochlorination are obtained. In ad-
dition, the reaction can proceed to form either of the Keywords: alkenes; aminochlorination; Brønstedt
two possible regioisomers, depending on whether acids; chloramine-T; oxidation
Introduction
kata and Kumada. Different conditions were report-
ed, which include the use of supercritical CO2,[12] or
The vicinal difunctionalization of alkenes under inter- hypervalent iodine reagents[13] as well as w-iodo-
molecular reaction control constitutes a veritable
challenge in oxidation. At the same time, it represents (Scheme 1).[14]
an important synthetic approach in order to accom- In general, aminohalogenation reactions have re-
A
for
oxidative
pyrrolidine
formation
plish selective transformation of bulk materials into ceived wide attention due to the importance of the vi-
building blocks of higher complexity for subsequent cinal chloramine products as building blocks in organ-
diversification. Few truly general reactions have been ic synthesis.[11] These reactions have been widely de-
developed so far.[1] Arguably, the most prominent ex- veloped using metal promoters to effect activation of
ample continues to be the osmium-catalyzed dihy- the respective N-chloroamines prior to alkene oxida-
droxylation reaction.[2] Additional metal-catalyzed di- tion. Among several other examples, the metal-cata-
functionalization reactions are available,[1,3] and lyzed aminochlorination with chloramine-T has been
recent progress has also centered on metal-free reac- explored.[15,16]
tivity.[4–6]
We here show that transition metal activation can
Commercially available chloramine-T (1)[7] is a par- be replaced by protonation of chloramine-T with
ticularly useful oxidant that has found broader appli-
cation in organic synthesis. For example, it serves as
a suitable nitrene precursor and has found significant
application in various alkene oxidation reactions such
as the osmium-catalyzed aminohydroxylation[1,3a,8] and
metal-catalyzed aziridination reactions.[9] Certain con-
ditions were described for chloramine-T promoting
the direct aziridination of alkenes without the re-
quirement of a metal promoter.[10]
À
In addition, the N Cl functionality in chloramine-T
should be attractive for metal-free aminohalogenation
reactions.[11] For the realization of such vicinal oxida-
Scheme 1. Representative metal-free aminohalogenation re-
tion reactions, significant work was achieved by Mina- actions based on chloramine-T.
Adv. Synth. Catal. 2014, 356, 205 – 211
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
205

FULL PAPERS
Claudio Martꢀnez and Kilian MuÇiz
Table 1. Aminochlorination of styrene: optimization of con-
ditions.
Brønstedt acids, which gives rise to an unexpected
direct aminochlorination of alkenes under mild condi-
tions. The reaction has an unprecedentedly broad sub-
strate scope as it proceeds with all classes of alkenes.
In addition, the regioselectivity of the reaction can be
tuned according to the reaction conditions.
Results and Discussion
We started the screening for styrene as substrate
(Table 1). As expected, no reaction takes place in the
sole presence of 1.2 equivalents of chloramine-T even
at elevated temperatures (entry 1). However, a clean
aminochlorination is induced by the addition of an
equimolar amount of pivalic acid (entry 2). Lowering
the amount of acid activator decreases the yield in
a proportional manner, while no reaction proceeds at
lower temperature (entries 3 and 4). Among alterna-
tive proton sources, benzoic acid gives a comparable
aminochlorination, while ammonium fluorides lead to
reduced yields (entries 5–7). Interestingly, the regio-
Table 2. Aminochlorination of terminal alkenes.[a]
ACHTUNGTRENNUNGisomeric product 4a was formed when the reaction
was carried out in acetic acid as solvent (entry 8).[17]
Under the conditions of activation with pivalic acid
the reaction performs well for a series of monosubsti-
tuted alkenes (Table 2).
These include all kinds of styrenes bearing para-
meta- and ortho-substituents as well as three allylben-
zenes. The robustness of the reaction was further
demonstrated by a reaction of 2a on 95-mmol scale
providing 27 g of the corresponding aminochlorinated
product 3a within a single reaction.[18] Aliphatic sub-
stituents are equally tolerated and products 3k–3n
were isolated as single regioisomers. For the latter ex-
ample of 3n from 5-hexenenitrile the structure was
unambiguously secured by X-ray analysis.[19] Forma-
tion of 3n underlines the selectivity of the amino-
chlorination reaction as no potentially competing
Ritter-type reaction product was observed.[20]
Interestingly, for styrenes bearing electron-donating
substituents, aminochlorination proceeds with inver-
sion of regioselectivity as determined for products 4a–
d, 4g and 4i–k (Table 3). As observed during the
screening process, such an inverted regioselectivity is
observed as the general outcome from reactions in
acetic acid as solvent, regardless of the nature of the
substituent. This is illustrated for the cases of 4-
bromo- and 4-chlorostyrene as well as 3-fluorostyrene
[a]
Yields refer to isolated product after purification.
95-mmol scale.
[b]
and 1-octene. In these cases products 4e, 4f and 4h 5e), while the reaction in acetic acid furnishes the cor-
are formed as regioisomers of 3b, 3c and 3g, respec- responding oxidation products 6a–6f from terminal
tively. Only for 1-octene was the product formed in chlorination. The complete change in regioselectivity
a 3:1-mixture in favor of the expected regioisomer 4l. is best illustrated by comparison of the products 5a
The same trend is observed for geminally disubsti- and 6a and 5e and 6f, respectively.
tuted alkenes (Table 4). In the presence of pivalic
The general features are also maintained for the
acid as activator, selective aminochlorination in favor aminochlorination of 1,2-disubstituted alkenes
of the terminal amination is obtained (products 5a– (Table 5). Here, with pivalic acid both isomers 7a and
206
asc.wiley-vch.de
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2014, 356, 205 – 211

FULL PAPERS
A Versatile Metal-Free Intermolecular Aminochlorination of Alkenes
Table 3. Aminochlorination of monosubstituted alkenes: in-
Table 5. Aminochlorination of 1,1-disubstituted alkenes.
version of regioselectivity.[a]
[a]
Yields refer to isolated product after purification.
3:1 regioisomeric mixture.
[b]
Table 4. Aminochlorination of 1,1-disubstituted alkenes.[a]
[a]
Isolated yield after purification.
For acetic acid, the corresponding regioisomers of 8b/
8b’ in a 4–7:1 diastereomeric ratio are formed (en-
tries 3 and 4). For the cinnamic esters 7c and 7d the
regioselective aminochlorination provides the two
1,2,3-trisubstituted products 8c/8c’ in 5:1 dr (entries 5
and 6). Stilbenes 7e and 7f provide the corresponding
products in high yields, although with diminished dr
(entries 7 and 8), while aminochlorination of indene
again proceeds with the expected full regioselectivity
(entry 9). Finally, two aliphatic substrates, cyclopen-
[a]
Yields refer to isolated product after purification.
7b of b-methylstyrene undergo regioselective amino- tene 7h and 1,5-cyclooctadiene 7i provide amino-
chlorination to a comparable product formation of 8a/ chlorination products 8g and 8h as single diastereoiso-
8a’ in a 4–5:1 diastereomeric ratio (entries 1 and 2). mers.
Adv. Synth. Catal. 2014, 356, 205 – 211
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
207

FULL PAPERS
Claudio Martꢀnez and Kilian MuÇiz
Table 6. Aminochlorination of tri- and tetrasubstituted
alkenes.
Scheme 2. Aminochlorination reaction of phenanthrene.
In addition to isolated alkenes, the aminochlorina-
tion of phenanthrene gave the expected oxidation at
C-9 and C-10 (Scheme 2). The corresponding product
8i is formed as a single diastereomer in 51% yield.
Treatment of the aminochlorination product with
base provides the expected re-aromatization to give
9-tosylamidophenanthrene 9 in quantitative yield. The
reaction can also be conducted as a one-pot sequence,
À
thereby formally resembling an aromatic C H amina-
tion reacion.
While higher substituted alkenes usually constitute
a challenge for vicinal oxidation of alkenes, the pres-
ent protocols tolerates both tri- and tetrasubstituted
alkenes (Table 6). Here, a single regioisomer 11a was
formed under both reaction conditions A and B in
the oxidation of b,b-dimethylstyrene (entries 1 and 2).
Again independent of the conditions, a single regio-
isomer is obtained as a 1:1-diastereomeric mixture in
[a]
Isolated yield after purification.
Yields in brackets based on re-isolated starting material.
[b]
Based on control experiments (Scheme 3), the
the case of the aminochlorination of a,b-dimethylstyr- Brønstedt acid-mediated aminochlorination is sug-
ene (entries 3–5), and consequently, 1-phenylcyclo- gested to be an ionic process. The involvement of rad-
hexene gives a single product 11c (entry 6). Alkene ical intermediates is ruled out on the basis of the a-
10e bearing three alkyl substituents again provides cyclopropylstyrene 2v, which forms a single product 4l
a single isomer, albeit with low overall yield (entry 7). without degradation of the cyclopropyl substituent.
Finally, the two tetrasubstituted alkenes 10f and 10g Aminochlorination of the monodeuterated styrene
form single regio- and diastereomeric products 11e 2a-d1 reveals the formation of an equimolar mixture
and 11f in 60 and 80% isolated yields, respectively of diastereomers. This loss of diastereoselectivity is
(entries 8 and 9), and the expected relative configura- the consequence of the involvement of a cationic in-
tion was confirmed from an X-ray analysis of 11f.[19]
termediate, which leads to diastereomeric equilibra-
These entries demonstrate that with the successful tion at the benzylic position. For the observed cases
examples of aminochlorination on monosubstituted, of internal alkenes, the independence of the product
(E)- and (Z)-disubstituted, 1,1’-disubstituted, (E)- and configuration from the alkene geometry and the for-
(Z)-trisubstituted and tetrasubstituted alkenes, all the mation of diastereomers are the consequences of such
seven different alkene classes are within the substrate intermediates.
scope. This is a particularly broad scope, which is only
Such stereochemical infidelity was also observed
common to the dihydroxylation of alkenes[1,2] and when an attempt toward enantioselective amino-
which should promote reliable applications in organic chlorination[21] was carried out in the presence of
synthesis.
10 mol% of (DHQD)2PHAL. Although a four-fold
208
asc.wiley-vch.de
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2014, 356, 205 – 211

FULL PAPERS
A Versatile Metal-Free Intermolecular Aminochlorination of Alkenes
Scheme 4. Aminochlorination reaction of styrene using an
activation through N-alkylation.
the chlorine anion results in regioselective amino-
chlorination product.
For more reactive and sterically more demanding
alkenes, the more accessible chlorine of TsNHCl will
serve as the electrophilie in the initial alkene attack.
The same should happen in acetic acid; with acetic
acid as reaction medium, partial protonation of the
nitrogen in N-chlorotosylamide through the acid net-
work should enhance the electrophilicity of the at-
tached chlorine atom. These reactions involve
a chloronium intermediate[11] and will ultimately un-
Scheme 3. Control experiments.
À
dergo Markovnikov-type C N bond formation.
Alternative to protonation, the electrophilic activa-
rate enhancement was observed for the transforma- tion of chloramines-T also proceeds through alkyla-
tion of 2a into 3a, the latter one was isolated only in tion. For example, treatment of chloramine-T with
racemic form.
Meerwein salt 14 followed by reaction with styrene
Although the exact mechanistic context must await leads to a clean process of aminochlorination in 55%
further studies, we suggest the following two reaction yield (Scheme 4). The formation of N-chloro-N-meth-
pathways to be involved (Figure 1). First, for simple yltosylamide as the reactive reagent was confirmed by
acid activation the neutral species TsNHCl will be its independent isolation after step 1.[22]
generated that provides an electrophilic nitrogen for
subsequent attack from a neutral, sterically non-hin-
dered alkene. This attack generates an aziridinium in- Conclusions
termediate[11] with certain stereochemical lability in
the case of the benzylic position. Recombination with In summary, we have described conditions for an un-
precedented metal-free aminochlorination reaction of
alkenes, which is of experimental ease and can be
conveniently upscaled. The reaction is based on Brøn-
stedt acid activation of chloramine-T and provides an
unparalleled substrate scope, and its regioselectivity
can be switched according to the reaction condi-
tions.[23] It is a rare example of an alkene oxidation re-
action that is operative for all seven classes of alkenes
as substrates.
Experimental Section
Typical Procedures
Conditions A: A Pyrex tube equipped with a stirrer bar was
charged with 142 mg chloramine-T (0.50 mmol, 1.2 equiv.),
51 mg pivalic acid (0.50 mmol, 1.2 equiv.) and the alkene
(0.42 mmol, 1 equiv.) in 0.6 mL of absolute dichloroethane.
The solution was stirred at 508C for 20 h. After cooling
down to room temperature, CH2Cl2 was added and the resi-
due was washed with a saturated aqueous solution of
Figure 1. Mechanistic proposal.
NaHCO3. The solvent was evaporated under reduced pres-
Adv. Synth. Catal. 2014, 356, 205 – 211
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
209

FULL PAPERS
Claudio Martꢀnez and Kilian MuÇiz
sure and the crude product was purified by chromatography
(silica gel, n-hexane/ethyl acetate, 4/1, v/v) to give the pure
aminochlorinated product.
Zian, A. Lishchynskyi, K. MuÇiz, Chem. Asian J. 2012,
7, 1103; i) J. A. Souto, C. Martꢀnez, I. Velilla, K. MuÇiz,
Angew. Chem. 2013, 125, 1363; Angew. Chem. Int. Ed.
2013, 52, 1324.
Conditions B: A Pyrex tube equipped with a stirrer bar
was charged with 240 mg chloramine-T (0.84 mmol,
2.0 equiv.) and the alkene (0.42 mmol, 1 equiv.) in 0.6 mL of
AcOH. The solution was stirred at 508C for 20 h. After
cooling down to room temperature, CH2Cl2 was added and
the residue was washed with a saturated aqueous solution of
NaHCO3. The combined organic layers were extracted with
CH2Cl2 (3ꢃ) and dried with Na2SO4. The solvent was re-
moved under reduced pressure and the crude mixture was
purified by chromatography (silica gel, n-hexane/ethyl ace-
tate, 4/1, v/v) to obtain the pure aminochlorinated product.
[5] Selected examples of intermolecular alkene oxidation
using halide catalysis: a) M. Uyanik, K. Ishihara,
ChemCatChem 2012, 4, 177; b) Q. Xue, J. Xie, P. Xu,
K. Hu, Y. Cheng, C. Zhu, ACS Catal. 2013, 3, 1365.
[6] Selected examples of intermolecular alkene oxidation
using radical reactivity: a) Y. Li, A. Studer, Angew.
Chem. 2012, 124, 8345; Angew. Chem. Int. Ed. 2012, 51,
8221; b) B. C. Giglio, V. A. Schmidt, E. J. Alexanian, J.
Am. Chem. Soc. 2011, 133, 11402; c) J. C. Griffith,
K. M. Jones, S. Picon, M. J. Rawling, B. M. Kariuki, M.
Campbell, N. C. Tomkinson, J. Am. Chem. Soc. 2011,
133, 14409; d) Q. Lu, J. Zhang, F. Wei, Y. Qi, H. Wang,
Z. Liu, A. Lei, Angew. Chem. Int. Ed. 2013, 52, 7156.
[7] a) R. R. Goehring, Encyclopedia of Reagents for Or-
ganic Chemistry, (Ed.: L. A. Paquette), Wiley, New
York, 1995, Vol. 2, pp 1054–1056; b) M. M. Campbell,
G. Johnson, Chem. Rev. 1978, 78, 65.
Acknowledgements
The authors thank Fundaciꢀn ICIQ and the Spanish Minis-
terio de Economꢁa (CTQ2011-25027) for financial support,
and Dr. Eduardo Escudero, Dr. Marta Bahamonte and Dr.
Eddy Martin from ICIQꢂs X-Ray Department for the solid
state structures.
[8] C. Bolm, J. P. Hildebrand, K. MuÇiz, in: Transition
Metal for Organic Synthesis, (Ed.: I. Ojima), Wiley-
VCH, Weinheim, 2000, p 299.
[9] a) T. Ando, S. Minakata, I. Ryu, M. Komatsu, Tetrahe-
dron Lett. 1998, 39, 309; b) S. Minakata, D. Kano, R.
Fukuoka, Y. Oderaotoshi, M. Komatsu, Heterocycles
2003, 60, 289; c) S. Chiba, K. Narasaka, in: Amino
Group Chemistry, (Ed.: A. Ricci), Wiley-VCH, Wein-
heim, 2008, pp 1–54.
[10] a) J. U. Jeong, B. Tao, I. Sagasser, H. Henniges, K. B.
Sharpless, J. Am. Chem. Soc. 1998, 120, 6844; b) T.
Ando, D. Kano, S. Minakata, I. Ryu, M. Komatsu, Tet-
rahedron 1998, 54, 13485. For other halide-catalyzed
alkene aziridination with chloramine-T, see: c) S. C.
Coote, P. O’Brian, A. C. Whitwood, Org. Biomol.
Chem. 2008, 6, 4299; d) S. L. Jain, B. Sain, Green
Chem. 2006, 8, 943; e) H. J. Wu, L. W. Xu, C. G. Xia, J.
Ge, L. Yang, Synth. Commun. 2005, 35, 1413; f) V. V.
Thakus, A. Sudalai, Tetrahedron Lett. 2003, 44, 989;
g) P. Dauban, R. H. Dodd, Tetrahedron Lett. 2001, 42,
1037; h) S. Minakata, D. Kano, Y. Oderaotoshi, M. Ko-
matsu, Angew. Chem. 2004, 116, 81; Angew. Chem. Int.
Ed. 2004, 43, 79.
References
[1] K. MuÇiz, in: Stereoselective Synthesis Oxidation, (Ed.:
H. de Vries), Science of Synthesis, Georg Thieme
Verlag, Stuttgart, 2011, pp 1–67.
[2] H. C. Kolb, M. S. VanNieuwenhze, K. B. Sharpless,
Chem. Rev. 1994, 94, 2483.
[3] Diboration: a) L. T. Kliman, S. N. Mlynarski, J. P.
Morken, J. Am. Chem. Soc. 2009, 131, 13210; b) J.
Ramꢀrez, A. M. Segarra, E. Fernꢄndez, Tetrahedron:
Asymmetry 2005, 16, 1289; dihydroxylation: c) B.
Plietker, Synthesis 2005, 2453; aminohydroxylation:
d) K. MuÇiz, Chem. Soc. Rev. 2004, 33, 166; aminoacet-
ACHTUNGTRENNUNGoxylation: e) G. Liu, S. S. Stahl, J. Am. Chem. Soc.
2006, 128, 7179; f) C. Martinez, Y. Wu, A. B. Weinstein,
S. S. Stahl, G. Liu, K. MuÇiz, J. Org. Chem. 2013, 78,
6309; dibromination: g) A. K. El-Qisairi, H. A. Qaseer,
G. Katsigras, P. Lorenzi, U. Trivedi, S. Tracz, A. Hart-
man, J. A. Miller, P. M. Henry, Org. Lett. 2003, 5, 439;
diamination: h) A. Iglesias, E. G. Pꢅrez, K. MuÇiz,
Angew. Chem. 2010, 122, 8286; Angew. Chem. Int. Ed.
2010, 49, 8109; i) C. Martꢀnez, K. MuÇiz, Angew. Chem.
2012, 124, 7138; Angew. Chem. Int. Ed. 2012, 51, 7031.
[4] Selected examples of intermolecular alkene oxidation
with hypervalent iodine reagents: a) G. F. Koser, Top.
Curr. Chem. 2000, 208, 137; b) K. C. Nicolaou, N. L.
Simmons, Y. Ying, P. M. Heretsch, J. S. Chen, J. Am.
Chem. Soc. 2011, 133, 8134; c) M. Fujita, W. Wakita, T.
Sugimura, Chem. Commun. 2011, 47, 3983; d) Y.-B.
Kang, L. H. Gade, J. Am. Chem. Soc. 2011, 133, 3658;
e) U. H. Hirt, B. Spingler, T. Wirth, J. Org. Chem. 1998,
63, 7674; f) R. Chung, E. Yu, C. D. Incarvito, D. J.
Austin, Org. Lett. 2004, 6, 3881; g) C. Rçben, J. A.
Souto, Y. Gonzꢄlez, A. Lishchynskyi, K. MuÇiz,
Angew. Chem. 2011, 123, 9650; Angew. Chem. Int. Ed.
2011, 50, 9478; h) J. Souto, Y. Gonzꢄlez, A. Iglesias, D.
[11] For recent reviews on catalytic aminohalogenation of
alkenes: a) S. R. Chemler, M. T. Bovino, ACS Catal.
2013, 3, 1076; b) G. Li, S. R. S. S. Kotti, C. Timmons,
Eur. J. Org. Chem. 2007, 2745; c) S. Minakata, Acc.
Chem. Res. 2009, 42, 1172.
[12] S. Minakata, Y. Yoneda, Y. Oderaotoshi, M. Komatsu,
Org. Lett. 2006, 8, 967.
[13] a) G.-W. Wang, X.-L. Wu, Adv. Synth. Catal. 2007, 349,
1977; b) X.-L. Wu, G.-W. Wang, J. Org. Chem. 2007, 72,
9398. For the corresponding aminobrominations, see
also: c) X.-L. Wu, G.-W. Wang, Tetrahedron 2009, 65,
8802; d) J.-J. Xia, X.-L. Wu, G.-W. Wang, Arkivoc 2008,
xvi, 22.
[14] a) S. Minakata, D. Kano, Y. Oderaotoshi, M. Komatsu,
Org. Lett. 2002, 4, 2097; b) For the related reaction
with TsNCl2: M. Qi, L. Shai, M. Shi, Chinese J. Chem.
2011, 29, 2739.
210
asc.wiley-vch.de
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2014, 356, 205 – 211

FULL PAPERS
A Versatile Metal-Free Intermolecular Aminochlorination of Alkenes
[15] a) O. O. Orazi, R. A. Corral, J. Zinczuk, H. Schutten-
berg, Tetrahedron Lett. 1982, 23, 293; b) M. D. Jonson,
G. M. Lampman, R. W. Koops, B. Das Gupta, J. Orga-
nomet. Chem. 1987, 326, 281; c) X.-Y. Liu, P. Gao, Y.-
W. Shen, Y.-M. Liang, Org. Lett. 2011, 13, 4196; d) X.-
Y. Liu, P. Gao, Y.-W. Shen, Y.-M. Liang, Adv. Synth.
Catal. 2011, 353, 3157.
[16] In addition to chloramine-T, related aminohalogenation
reactions with ArSO2NX2 (X=Cl, Br) were investigat-
ed extensively. Although related in product formation,
these reagents are less attractive from an economic
an NBS/TsNH2 reagent combination: V. V. Thakur,
S. K. Talluri, A. Sudalai, Org. Lett. 2003, 5, 861; b) For
a related titanium catalysis: T. M. Shaikh, P. U. Kara-
bal, G. Suryavanshi, A. Sudalai, Tetrahedron Lett. 2009,
50, 2815.
[18] See the Supporting Information for details.
[19] CCDC 947016 (8c), CCDC 947018 (11f), CCDC
947019 (8c’), CCDC 947020 (3n), CCDC 947021 (4m),
and CCDC 947022 (8i) contain the supplementary crys-
tallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
[20] For Ritter reactions as the dominating process in
alkene oxidation with TsNCl2 and related compounds,
see refs.[11,16]
[21] S. E. Denmark, W. E. Kuester, M. T. Burk, Angew.
Chem. 2012, 124, 11098; Angew. Chem. Int. Ed. 2012,
51, 10938.
[22] O. O. Orazi, R. A. Corral, H. Schuttenberg, Tetrahe-
dron 1969, 25, 2639.
[23] It is a unique feature in alkene difunctionalization, that
a simple change between neutral to acidic medium
leads to inversion of regioselectivity. For example, for
the largely explored aminohydroxylation, the context is
significantly more complicated.[8].
À
point of view as only one of the N X bonds is required
for the alkene oxidation. See ref.[11] and a) J.-L. Han,
S.-J. Zhi, L.-Y. Wang, Y. Pan, G.-G. Li, Eur. J. Org.
Chem. 2007, 1332 and references cited therein; b) A.
Sniwinska, A. Zwierzak, Tetrahedron 2003, 59, 5927;
c) Y.-N. Wang, B.-K. Ni, A. D. Headley, G.-G. Li, Adv.
Synth. Catal. 2007, 349, 319; d) G. Li, H.-X. Wei, S. H.
Kim, M. D. Carducci, Angew. Chem. 2001, 113, 4407;
Angew. Chem. Int. Ed. 2001, 40, 4277; e) C. Timmons,
L. M. Mcpherson, D. Chen, H.-X. Wei, G. Li, J. Pept.
Res. 2005, 66, 249; f) for the in situ formation of TsNI2
leading to aziridination: K. Kiyokawa, T. Kosaka, S.
Minakata, Org. Lett. 2013, 15, 4858.
[17] a) A related reversal of regioselectivity was previously
observed for copper-catalyzed aminobromination using
Adv. Synth. Catal. 2014, 356, 205 – 211
ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
211