Silver(I)-catalyzed hydroazidation of ethynyl carbinols: Synthesis of 2-azidoallyl alcohols

Article abstract of DOI:10.1002/anie.201310264

The hydroazidation of alkynes is the most straightforward pathway to synthetically useful vinyl azides. However, a general hydroazidation of alkynes remains elusive. Herein, a chemo- and regioselective transformation of ethynyl carbinols into vinyl azides is described. This reaction produces a wide variety of 2-azidoallyl alcohols with high efficiency and in good to excellent yields. These compounds constitute a new class of densely functionalized synthetic intermediates. Their synthetic potential has been demonstrated by further transformations into NH aziridines. The mechanistic aspects of the reaction will attract the attention of chemists working on alkyne chemistry and silver catalysis. The findings that are described in this paper represent significant advances in the regioselective hydroelementation of alkynes and open a new reaction manifold for exploitation. Azides and aziridines: The hydroazidation of unactivated alkynes by means of silver catalysis is described. A variety of ethynyl carbinols are capable of reacting with trimethylsilyl azide to produce 2-azidoallyl alcohols in good to excellent yields. The synthetic utility of 2-azidoallyl alcohols was demonstrated by further conversion into NH aziridines.

Full text of DOI:10.1002/anie.201310264

Angewandte
Chemie
DOI: 10.1002/anie.201310264
Hydroazidation
Silver(I)-Catalyzed Hydroazidation of Ethynyl Carbinols: Synthesis of
2-Azidoallyl Alcohols**
Zhenhua Liu, Jianquan Liu, Lin Zhang, Peiqiu Liao, Jinna Song, and Xihe Bi*
Abstract: The hydroazidation of alkynes is the most straight-
forward pathway to synthetically useful vinyl azides. However,
a general hydroazidation of alkynes remains elusive. Herein,
a chemo- and regioselective transformation of ethynyl carbi-
nols into vinyl azides is described. This reaction produces
a wide variety of 2-azidoallyl alcohols with high efficiency and
in good to excellent yields. These compounds constitute a new
class of densely functionalized synthetic intermediates. Their
synthetic potential has been demonstrated by further trans-
formations into NH aziridines. The mechanistic aspects of the
reaction will attract the attention of chemists working on alkyne
chemistry and silver catalysis. The findings that are described
À
Figure 1. Chemoselective reactions of alkynes with TMS N3.
in this paper represent significant advances in the regioselective
hydroelementation of alkynes and open a new reaction
manifold for exploitation.
À
with trimethylsilyl azide (TMS N3) using gold catalysis,
H
ydroelementation of alkynes is a powerful means of
affording tetrazoles (Figure 1b).[6] Inspired by Jiaoꢀs pioneer-
ing work and by our long-standing interest in developing
transition-metal-catalyzed organic reactions,[7] we herein wish
to report an unprecedented chemo- and regioselective hydro-
azidation of ethynyl carbinols. A general and efficient method
to access 2-azidoallyl alcohols has thus been developed
(Figure 1c). The hydroxy group that is close to the alkyne
unit plays a critical role in directing the chemoselectivity.
Ethynyl carbinols are easily available bifunctional build-
ing blocks. The potential of such compounds to undergo
reactions that are different from those of isolated alkynes
accessing functionalized alkenes.[1] For unsymmetric alkynes,
the control of the chemo- and regioselectivity of such
reactions is a challenging issue. Vinyl azides are a class of
unique functionalized alkenes.[2] They have attracted consid-
erable attention because of their high intrinsic reactivity.[3]
However, the limited access to this kind of compounds has
seriously hampered the wider exploitation of their synthetic
potential. The hydroazidation of alkynes is an ideal route to
vinyl azides.[4] However, known variants of this transforma-
tion are nearly all limited to the addition of an azide species to
electron-deficient alkynes. With regard to unactivated
alkynes, only two isolated examples have been mentioned in
previous reports.[4d,5a] Very recently, Jiao and co-workers
described novel chemoselective transformations of alkynes
into nitriles[5a] and amides[5b] (Figure 1a). Complete chemo-
selectivity was achieved by using suitable catalysts. During
our preparation of this manuscript, Echavarren and Gaydou
reported another chemoselective reaction of terminal alkynes
results from the close proximity of the hydroxy group to the
C C bond. Herein, we focus on the reaction of ethynyl
carbinols with trimethylsilyl azide (TMS N3) under silver-
[8]
ꢀ
À
catalyzed conditions,[9] and a hydroxy-directed regioselective
hydroazidation of terminal alkynes was discovered. Among
the tested silver salts, silver carbonate (Ag2CO3) gave the best
yield (85%) of vinyl azide 2a (Table 1, entries 1–3). Notably,
unlike in Jiaoꢀs work,[5a] 2-hydroxy-2-phenylacetonitrile,
1
a product generated from 2a, was not detected by H NMR
spectroscopy of the reaction mixture. This clearly demon-
strates the unusual ability of the hydroxy group to stabilize
vinyl azides. In contrast to the silver catalysts, other metal
salts, such as Pd(OAc)2 and CuI, were not effective (entries 4
and 5). The solvent also exerted a significant influence on the
reaction. For example, in dimethylformamide (DMF), 2a was
obtained in 69% yield (entry 6). Toluene and methanol
turned out to be ineffective (entries 7 and 8). Sources of
[*] Z. Liu, J. Liu, L. Zhang, Dr. P. Liao, Prof. J. Song, Prof. X. Bi
Department of Chemistry
Northeast Normal University
Changchun 130024 (China)
E-mail: bixh507@nenu.edu.cn
Prof. X. Bi
State Key Laboratory of Elemento-Organic Chemistry
Nankai University
Tianjin 300071 (China)
À
azides other than TMS N3, including sodium and tosyl azide,
[**] This work was supported by the NNSFC (21172029, 21202016,
21372038, 31101010), the Ministry of Education of the People’s
Republic of China (NCET-13-0714), and the Jilin Provincial Research
Foundation for Basic Research (20140519008JH).
were also tested, but only the former afforded a reasonable
À
yield of 2a. Consequently, TMS N3 was used as the azide
source in the studies described below.
After determining the optimized reaction conditions, we
investigated the scope of the reaction for many different
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201310264.
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Table 1: Screening of the reaction conditions.[a]
reaction times were required, which might be due to steric
effects. Aside from these common electron-rich and -deficient
(hetero)aryl and alkyl groups, several highly reactive func-
tional groups, including alkenyl (2k, 2l, 4e), alkynyl (2m, 4k),
and cyclopropyl (4c) moieties, were found to be well
tolerated. The dense arrangement of several functional
groups in one molecular scaffold renders 2-azidoallyl alcohols
highly attractive synthetic intermediates; however, only one
report on their synthesis by Trofimov and co-workers could be
found in the literature; they described a method that proceeds
by the addition of hydrazoic acid to acetylenic hydroxy acid
nitriles.[10] Therefore, we have developed an efficient route to
this kind of compounds with great synthetic potential.
Entry
Catalyst
Solvent
Yield[b] [%]
1
2
3
4
5
6
7
8
AgNO3
AgF
Ag2CO3
Pd(OAc)2
CuI
Ag2CO3
Ag2CO3
Ag2CO3
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
75
62
85
0
0
69
trace
0
toluene
MeOH
To determine the source of hydrogen in the above
hydroazidation, the effect of residual water (H2O) in the
DMSO solvent was investigated (Scheme 2). In dry DMSO,
À
[a] Reactions were carried out with 1a (0.5 mmol) and TMS N3
(0.75 mmol) in the presence of a catalyst (10 mol%) in 2 mL of solvent
at 808C under ambient atmosphere for 2 h. [b] Yields of isolated
products.
ethynyl carbinols (Scheme 1). In general, the substrate scope
is quite broad, and a wide variety of secondary and tertiary
ethynyl carbinols with various substituents can be subjected
to this new silver-catalyzed reaction, giving the corresponding
products (2 and 4) in good to excellent yields. All of the
reactions proceeded smoothly and were completed within
0.5–2 hours; only for 4d (6 h) and 4e (8 h), slightly extended
Scheme 2. The effect of water on the reaction outcome.
a mixture of 2a and O-trimethylsilylated TMS–2a was
1
obtained in a 1:3 ratio, which was determined by H NMR
analysis of the crude product. Once H2O (1.0 equiv) had been
added to the reaction, only 2a was produced, without
TMS–2a. Notably, TMS–2a remained intact in the presence
of H2O (1.0 equiv) and Ag2CO3 (10 mol%) in DMSO at
808C, thus excluding the possibility that TMS–2a was first
formed and then converted into 2a by hydrolysis. Increasing
the amount of H2O up to 1 mL (for 0.5 mmol of 1a) resulted
in a large amount of unreacted substrate 1a in the reaction
mixture.
Ethisterone is the first orally active progestin.[11] The
structural modification of ethisterone is highly interesting
because of its significance for structure–activity relationship
(SAR) studies.[12] However, the site-specific manipulation of
the alkynyl group is challenging because of its close proximity
to the reactive hydroxy group. The present method was
applied to derivatize ethisterone, resulting in a single func-
tional group transformation from alkyne to vinyl azide that
did not change the chiral center (Scheme 3). The structure of
vinyl azide modified ethisterone (VA-ethisterone) was unam-
biguously confirmed by X-ray diffraction.[13] This compound
may be interesting to medicinal chemists.
Furthermore, the practicality of this silver-catalyzed
hydroazidation of ethynyl carbinols was demonstrated by
a gram-scale synthesis (Scheme 4). For example, vinyl azide
2c was directly prepared from piperonyl aldehyde (5) in 72%
yield in a one-pot reaction. The stability of vinyl azide 2c was
confirmed by standard 1H NMR spectroscopy, and compound
2c was found to remain intact in CDCl3 under ambient
conditions for at least one month without any obvious
changes. Their stability and easy availability persuaded us to
Scheme 1. Scope of the reaction. Bn=benzyl.
2
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Furthermore, control experiments were per-
formed to gain insights into the reaction pathway
(Scheme 6). In the absence of Ag2CO3, silver
À
acetylide [Ag]-3a reacted with TMS N3 and
afforded a mixture of vinyl azide 4a and ethynyl
carbinol 3a in a 1.3:1 ratio [Eq. (1)]. When two
equivalents of deuterium oxide (D2O) were
À
added to the reaction of 3a with TMS N3,
Scheme 3. Modification of ethisterone.
Scheme 4. Gram-scale synthesis and further transformations.
exploit synthetic transformations of 2-azidoallyl alcohols.
First, the oxidation of 2c to a-carbonyl vinyl azide 6 in 83%
yield was achieved using pyridinium chlorochromate (PCC)
as the oxidant. More importantly, an unprecedented con-
version of 2c into NH aziridine 7a, which is catalyzed by
potassium phosphate (K3PO4), was discovered.[14] These
results demonstrate the usefulness of 2-azidoallyl alcohols
as synthetic intermediates.
Aziridines are important synthetic building blocks for the
construction of complex nitrogen-containing compounds.[15]
Many methods for constructing aziridine ring systems have
been identified over the past decades.[16] However, most
approaches require a protecting group at the nitrogen atom,
such as a tosyl group. Thus far, approaches to NH aziridines
are much less common.[17] The synthesis of NH aziridine 7a
from 2-azidoallyl alcohols is attractive because of the clean
conversion and the mild reaction conditions. Therefore, the
scope of the reaction was expanded by varying the 2-
azidoallyl alcohol. A variety of NH aziridines (7b–7i) were
prepared in good yields by choosing the appropriate 2-
azidoallyl alcohol (Scheme 5).
Scheme 6. Mechanistic investigations.
a mono-deuterated product [D]-4a was generated with
a deuterium content of 93% under the standard reaction
conditions [Ag2CO3 (10 mol%), DMSO, 808C; Eq. (2)]. This
result implies that a silver intermediate might be generated
during the reaction. The deuterated substrate [D]-3a afforded
[D]-4a in 45% yield with a deuterium content of 56% in dry
DMSO, whereas adding H2O (2.0 equiv) to the reaction only
afforded 4a, without [D]-4a [Eq. (3)]. The reaction of benzyl-
À
protected 8 with TMS N3 generated a mixture of vinyl azide
9a (45%) and cyanide 9b (33%), which implies that the free
hydroxy group plays a role in stabilizing the vinyl azide
products [Eq. (4)]. A terminal alkyne moiety was necessary
Scheme 5. Transformations of 2-azidoallyl alcohols into NH aziridines.
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for the alkyne hydroazidation because the internal alkynyl
carbinol 10 was not converted into the desired product
[Eq. (5)]. The reaction of 1c proceeded well in the presence
of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and afforded
the vinyl azide product 2c in 77% yield, so that a radical
process can be excluded for this reaction.
chemistry and silver catalysis. The findings that are described
in this paper represent significant advances in the regioselec-
tive hydrofunctionalization of alkynes and open a new
reaction manifold for exploitation.
Received: November 26, 2013
Revised: January 18, 2014
The possible mechanism for the transformation of 2-
azidoallyl alcohols into NH aziridines was also studied. First,
the deuterated product [D]-7c was obtained with 81%
deuterium content using [D]-2a as the starting material,
suggesting that the alkenyl hydrogen atom of [D]-2a is not
removed during ring closure [Eq. (6)]. The addition of D2O
(2.0 equiv) to the reaction of 2a produced a deuterated
product [D]-7c’ with a deuterium content of 65% at the a-
carbonyl position [Eq. (7)]. Interestingly, deuterated sub-
strate [D]-2a’ only gave undeuterated product 7c [Eq. (8)].
When we directly analyzed the reaction mixture of [D]-2a’ by
high-resolution mass spectrometry (HRMS), a peak that
corresponds to monodeuterated aziridine was found, imply-
ing that the deuterium atom of [D]-2a’ might migrate to the
Published online: && &&, &&&&
Keywords: aziridines · ethynyl carbinols · hydroazidation ·
.
silver catalysis · vinyl azides
[1] For general reviews on the hydroelementation of alkynes, see:
a) F. Alonso, I. P. Beletskaya, M. Yus, Chem. Rev. 2004, 104,
3079 – 3159; b) X. Zeng, Chem. Rev. 2013, 113, 6864 – 6900.
[2] For a comprehensive review on the synthesis and reactions of
vinyl azides, see: K. Banert in Organic Azides: Syntheses and
Applications (Eds.: S. Brꢁse, K. Banert), Wiley, Chichester, 2010.
[3] For examples, see: a) F. Chen, T. Shen, Y. Cui, N. Jiao, Org. Lett.
2012, 14, 4926 – 4929; b) Y.-F. Wang, K. K. Toh, J.-Y. Lee, S.
Chiba, Angew. Chem. 2011, 123, 6049 – 6053; Angew. Chem. Int.
Ed. 2011, 50, 5927 – 5931; c) Y.-F. Wang, K. K. Toh, E. P. J. Ng, S.
Chiba, J. Am. Chem. Soc. 2011, 133, 6411 – 6421; d) Y.-F. Wang,
S. Chiba, J. Am. Chem. Soc. 2009, 131, 12570 – 12572; e) B. J.
Stokes, H. Dong, B. E. Leslie, A. L. Pumphrey, T. G. Driver, J.
Am. Chem. Soc. 2007, 129, 7500 – 7501; f) B. Hu, Z. Wang, N. Ai,
J. Zheng, X.-H. Liu, S. Shan, Z. Wang, Org. Lett. 2011, 13, 6362 –
6365; g) W. Chen, M. Hu, J. Wu, H. Zou, Y. Yu, Org. Lett. 2010,
12, 3863 – 3865; h) B. J. Stokes, C. V. Vogel, L. K. Urnezis, M.
Pan, T. G. Driver, Org. Lett. 2010, 12, 2884 – 2887; i) S. Chiba, L.
Zhang, G. Y. B. Ang, W.-Q. Hui, Org. Lett. 2010, 12, 2052 – 2055;
j) Y.-F. Wang, K. K. Toh, S. Chiba, K. Narasaka, Org. Lett. 2008,
10, 5019 – 5022; k) S. Chiba, Y.-F. Wang, G. Lapointe, K.
Narasaka, Org. Lett. 2008, 10, 313 – 316; l) H. Dong, M. Shen,
J. E. Redford, B. J. Stokes, A. L. Pumphrey, T. G. Driver, Org.
Lett. 2007, 9, 5191 – 5194.
À
N H position of 7c and then be removed by proton exchange
after work-up.
Following these preliminary mechanistic studies, a plau-
sible reaction mechanism is tentatively proposed. The initial
step involves the formation of silver acetylide intermediate A
from the interaction of reactant 1a with the silver catalyst
(Scheme 7).[18] The subsequent addition reaction takes place
[4] a) I. F. D. Hyatt, M. P. Croatt, Angew. Chem. 2012, 124, 7629 –
7632; Angew. Chem. Int. Ed. 2012, 51, 7511 – 7514; b) F. Palacios,
D. Aparicio, J. M. de Los Santos, I. Perez de Heredia, G.
Rubiales, Org. Prep. Proced. Int. 1995, 27, 171 – 178; c) M.
Haddach, R. Pastor, J. G. Riess, Tetrahedron 1993, 49, 4627 –
4638; d) K. Banert, Chem. Ber. 1989, 122, 1175 – 1178; e) T.
Kitamura, P. J. Stang, Tetrahedron Lett. 1988, 29, 1887 – 1889;
f) M. Ochiai, M. Kunishima, K. Fuji, Y. Nagao, J. Org. Chem.
1988, 53, 6144 – 6145; g) V. G. Ostroverkhov, E. A. Shilov, Ukr.
Khim. Zh. 1957, 23, 615 – 622.
[5] a) T. Shen, T. Wang, C. Qin, N. Jiao, Angew. Chem. 2013, 125,
6809 – 6812; Angew. Chem. Int. Ed. 2013, 52, 6677 – 6680; b) C.
Qin, P. Feng, Y. Ou, T. Shen, T. Wang, N. Jiao, Angew. Chem.
2013, 125, 8004 – 8008; Angew. Chem. Int. Ed. 2013, 52, 7850 –
7854.
Scheme 7. Proposed mechanism.
with hydrazoic acid (HN3) that was generated in situ by silver-
catalyzed hydrolysis of TMS-N3, to give vinyl silver inter-
mediate B.[4] Product 2a was then produced through the
protonation of B with a trace amount of H2O in the DMSO
solvent. For the conversion of vinyl azide 2a into aziridine 7c,
2H-azirine C may first be generated from 2a under thermal
conditions. Following sequential 1,3-proton transfer and keto/
enol tautomerism, the NH aziridine 7c is formed.
In conclusion, a chemo- and regioselective transformation
of ethynyl carbinols into vinyl azides has been described. This
reaction produces a wide variety of 2-azidoallyl alcohols with
high efficiency and in good to excellent yields. These
compounds represent a class of densely functionalized
synthetic intermediates. Their synthetic potential has been
demonstrated by further transformations into NH aziridines.
The mechanistic aspects of this reaction are also interesting
and will attract the attention of chemists working on alkyne
[6] M. Gaydou, A. M. Echavarren, Angew. Chem. 2013, 125, 13710 –
13713; Angew. Chem. Int. Ed. 2013, 52, 13468 – 13471.
[7] a) J. Liu, Z. Fang, Q. Zhang, Q. Liu, X. Bi, Angew. Chem. 2013,
125, 7091 – 7095; Angew. Chem. Int. Ed. 2013, 52, 6953 – 6957;
b) L. Zhang, X. Bi, X. Guan, X. Li, Q. Liu, B.-D. Barry, P. Liao,
Angew. Chem. 2013, 125, 11513 – 11517; Angew. Chem. Int. Ed.
2013, 52, 11303 – 11307; c) Z. Wang, X. Bi, P. Liao, X. Liu, D.
Dong, Chem. Commun. 2013, 49, 1309 – 1311; d) T. Xiong, Y. Li,
X. Bi, Y. Lv, Q. Zhang, Angew. Chem. 2011, 123, 7278 – 7281;
Angew. Chem. Int. Ed. 2011, 50, 7140 – 7143; e) Z. Wang, X. Bi, P.
Liao, R. Zhang, Y. Liang, D. Dong, Chem. Commun. 2012, 48,
7076 – 7078; f) K. Wang, X. Bi, S. Xing, P. Liao, Z. Fang, X. Meng,
Q. Zhang, Q. Liu, Y. Ji, Green Chem. 2011, 13, 562 – 565; g) L.
4
www.angewandte.org
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These are not the final page numbers!

Angewandte
Chemie
Zhang, Z. Liu, H. Li, G. Fang, B.-D. Barry, T. A. Belay, X. Bi, Q.
Liu, Org. Lett. 2011, 13, 6536 – 6539.
[10] B. A. Trofimov, A. G. Malꢀkina, R. N. Kudyakova, Zh. Org.
Khim. 1993, 29, 1942 – 1946.
[11] For a review, see: A. B. Forinash, S. L. Evans, Pharmacotherapy
2003, 23, 1573 – 1591.
[12] P. M. Levine, K. Imberg, M. J. Garabedian, K. Kirshenbaum, J.
Am. Chem. Soc. 2012, 134, 6912 – 6915.
[8] For selected examples of transition-metal-catalyzed reactions of
alkynyl carbinols, see: a) Z. Li, V. Boyarskikh, J. H. Hansen, J.
Autschbach, D. G. Musaev, H. M. L. Davies, J. Am. Chem. Soc.
2012, 134, 15497 – 15504; b) B. S. L. Collins, M. G. Suero, M. J.
Gaunt, Angew. Chem. 2013, 125, 5911 – 5914; Angew. Chem. Int.
Ed. 2013, 52, 5799 – 5802; c) G. Cera, S. Piscitelli, M. Chiarucci,
G. Fabrizi, A. Goggiamani, R. S. Ramꢂn, S. P. Nolan, M.
Bandini, Angew. Chem. 2012, 124, 10029 – 10033; Angew.
Chem. Int. Ed. 2012, 51, 9891 – 9895; d) T. Kimura, K. Kamata,
N. Mizuno, Angew. Chem. 2012, 124, 6804 – 6807; Angew. Chem.
Int. Ed. 2012, 51, 6700 – 6703; e) P. Lenden, D. A. Entwistle,
M. C. Willis, Angew. Chem. 2011, 123, 10845 – 10848; Angew.
Chem. Int. Ed. 2011, 50, 10657 – 10660; f) N. Chinkov, A. Warm,
E. M. Carreira, Angew. Chem. 2011, 123, 3014 – 3018; Angew.
Chem. Int. Ed. 2011, 50, 2957 – 2961; g) M. Ikeda, Y. Miyake, Y.
Nishibayashi, Angew. Chem. 2010, 122, 7447 – 7451; Angew.
Chem. Int. Ed. 2010, 49, 7289 – 7293; h) S. Minakata, I. Sasaki, T.
Ide, Angew. Chem. 2010, 122, 1331 – 1333; Angew. Chem. Int. Ed.
2010, 49, 1309 – 1311; i) R. Shintani, K. Takatsu, T. Katoh, T.
Nishimura, T. Hayashi, Angew. Chem. 2008, 120, 1469 – 1471;
Angew. Chem. Int. Ed. 2008, 47, 1447 – 1449; j) H. Jiang, C. Qiao,
W. Liu, Chem. Eur. J. 2010, 16, 10968 – 10970; k) T. Miura, Y.
Funakoshi, M. Morimoto, T. Biyajima, M. Murakami, J. Am.
Chem. Soc. 2012, 134, 17440 – 17443; l) L. Ye, W. He, L. Zhang, J.
Am. Chem. Soc. 2010, 132, 8550 – 8551; m) S. Yoshida, K. Fukui,
S. Kikuchi, T. Yamada, J. Am. Chem. Soc. 2010, 132, 4072 – 4073;
n) B. M. Trost, R. C. Livingston, J. Am. Chem. Soc. 2008, 130,
11970 – 11978; o) X. Pu, J. M. Ready, J. Am. Chem. Soc. 2008,
130, 10874 – 10875; p) D. K. Friel, M. L. Snapper, A. H. Hov-
eyda, J. Am. Chem. Soc. 2008, 130, 9942 – 9951; q) Y. Sugawara,
W. Yamada, S. Yoshida, T. Ikeno, T. Yamada, J. Am. Chem. Soc.
2007, 129, 12902 – 12903; r) D. Zhang, J. M. Ready, J. Am. Chem.
Soc. 2007, 129, 12088 – 12089; s) Y. Yamauchi, G. Onodera, K.
Sakata, M. Yuki, Y. Miyake, S. Uemura, Y. Nishibayashi, J. Am.
Chem. Soc. 2007, 129, 5175 – 5179; t) Y. Yamamoto, J.-i. Ishii, H.
Nishiyama, K. Itoh, J. Am. Chem. Soc. 2005, 127, 9625 – 9631.
[9] Silver in Organic Chemistry (Ed.: M. Harmata), Wiley, Hobo-
ken, 2010.
[13] For details, see the Supporting Information.
[14] Thermolysis of vinyl azides generally produces unsaturated 2H-
azirines; for examples, see: a) A. Padwa, A. Ku, H. Ku, A.
Mazzu, J. Org. Chem. 1978, 43, 66 – 72; b) M. Komatsu, S.
Ichijima, Y. Ohshiro, T. Agawa, J. Org. Chem. 1973, 38, 4341 –
4342; c) A. Hassner, E. S. Ferdinandi, R. J. Isbister, J. Am.
Chem. Soc. 1970, 92, 1672 – 1675; d) K. Isomura, M. Okada, H.
Taniguchi, Tetrahedron Lett. 1969, 10, 4073 – 4076; e) G. LꢀAbbꢃ,
A. Hassner, Angew. Chem. 1971, 83, 103 – 109; Angew. Chem.
Int. Ed. Engl. 1971, 10, 98 – 104.
[15] For selected reviews, see: a) S. Florio, R. Luisi, Chem. Rev. 2010,
´
110, 5128 – 5157; b) S. Stankovic, M. Dꢀhooghe, S. Catak, H.
Eum, M. Waroquier, V. Van Speybroeck, N. De Kimpe, H.-J. Ha,
Chem. Soc. Rev. 2012, 41, 643 – 665; c) A. L. Cardoso, T. M. V. D.
Pinho e Melo, Eur. J. Org. Chem. 2012, 6479 – 6501.
[16] a) I. D. G. Watson, L. Yu, A. K. Yudin, Acc. Chem. Res. 2006, 39,
194 – 206; b) T. Ibuka, Chem. Soc. Rev. 1998, 27, 145 – 154.
[17] For examples of the synthesis and reactions of NH aziridines,
see: a) B. R. Buckley, A. P. Patel, K. G. U. Wijayantha, J. Org.
Chem. 2013, 78, 1289 – 1292; b) F. von Kieseritzkya, J. Lind-
strçma, Tetrahedron Lett. 2011, 52, 4558 – 4561; c) S. Bakthara-
man, N. Afagh, A. Vandersteen, A. K. Yudin, Org. Lett. 2010, 12,
240 – 243; d) A. B. Pulipaka, S. C. Bergmeier, J. Org. Chem.
2008, 73, 1462 – 1467; e) D. M. Hodgson, P. G. Humphreys, S. M.
Miles, C. A. J. Brierley, J. W. Ward, J. Org. Chem. 2007, 72,
10009 – 10021; f) D. L. Warner, A. M. Hibberd, M. Kalman, A.
Klapars, E. Vedejs, J. Org. Chem. 2007, 72, 8519 – 8522; g) Z. Lu,
Y. Zhang, W. D. Wulff, J. Am. Chem. Soc. 2007, 129, 7185 – 7194;
h) M. Sasaki, S. Dalili, A. K. Yudin, J. Org. Chem. 2003, 68,
2045 – 2047; i) B. Olofsson, R. Wijtmans, P. Somfai, Tetrahedron
2002, 58, 5979 – 5982; j) S. C. Bergmeier, P. P. Seth, Tetrahedron
Lett. 1999, 40, 6181 – 6184; k) A. Koohang, C. L. Stanchina,
R. M. Coates, Tetrahedron 1999, 55, 9669 – 9686.
[18] U. Lꢃtinois-Halbes, P. Pale, S. Berger, J. Org. Chem. 2005, 70,
9185 – 9190.
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
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.
Angewandte
Communications
Communications
Hydroazidation
Azides and aziridines: The hydroazidation
of unactivated alkynes by means of silver
catalysis is described. A variety of ethynyl
carbinols are capable of reacting with
trimethylsilyl azide to produce 2-azi-
doallyl alcohols in good to excellent
yields. The synthetic utility of 2-azidoallyl
alcohols was demonstrated by further
conversion into NH aziridines.
Z. Liu, J. Liu, L. Zhang, P. Liao, J. Song,
X. Bi*
&&&& — &&&&
Silver(I)-Catalyzed Hydroazidation of
Ethynyl Carbinols: Synthesis of 2-
Azidoallyl Alcohols
6
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!