Nickel-catalysed denitrogenative alkyne insertion reactions of N-sulfonyl-1,2,3-triazoles

Article abstract of DOI:10.1039/b819162j

N-Sulfonyl-1,2,3-triazoles reacted with alkynes in the presence of a nickel(0)/phosphine catalyst to give substituted pyrroles, with the extrusion of molecular nitrogen; the triazole moiety isomerised to an α-imino diazo species, and the denitrogenative a

Full text of DOI:10.1039/b819162j

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Chemical Communications
www.rsc.org/chemcomm
Number 12 | 28 March 2009 | Pages 1421–1584
ISSN 1359-7345
FEATURE ARTICLE
COMMUNICATION
Masahiro Murakami et al.
Lynne B. McCusker and
Christian Baerlocher
Nickel-catalysed denitrogenative
alkyne insertion reactions of
N-sulfonyl-1,2,3-triazoles
Using electron microscopy to
complement X-ray powder diffraction
data to solve complex crystal structures
1359-7345(2009)12;1-4

COMMUNICATION
www.rsc.org/chemcomm | ChemComm
Nickel-catalysed denitrogenative alkyne insertion reactions
of N-sulfonyl-1,2,3-triazolesw
Tomoya Miura, Motoshi Yamauchi and Masahiro Murakami*
Received (in Cambridge, UK) 28th October 2008, Accepted 24th November 2008
First published as an Advance Article on the web 6th January 2009
DOI: 10.1039/b819162j
N-Sulfonyl-1,2,3-triazoles reacted with alkynes in the presence
of a nickel(0)/phosphine catalyst to give substituted pyrroles,
with the extrusion of molecular nitrogen; the triazole moiety
isomerised to an a-imino diazo species, and the denitrogenative
addition to nickel(0) was followed by the insertion of alkynes and
reductive elimination.
Table 1 Optimisation study of the formation of pyrrole 3aa
The development of efficient methods for the synthesis of
heterocyclic compounds is highly valuable,1 particularly in
the field of medicinal chemistry, because most biologically
active compounds contain heterocyclic cores. Recently, transi-
tion metal-catalysed denitrogenative reactions of triazole
derivatives, forming new heterocyclic systems, have been
reported, in which diazo compounds were generated in situ
by ring–chain tautomerisation, and subsequently converted
Yield
(%)a
Entry
Ligand
Lewis acid
1
2
3
4
5
6
7
8
PMe3
PCy3
P(t-Bu)3
P(n-Bu)Ad2
P(n-Bu)Ad2
P(n-Bu)Ad2
P(n-Bu)Ad2
P(n-Bu)Ad2
—
—
—
—
BPh3
ZnPh2
AlMe3
AlPh3
2
8
13
51
49
62
38
to
a reactive metal-carbenoid species. 7-Halo-substituted
pyridotriazoles2 and N-sulfonyl-1,2,3-triazoles3 react with alkynes
and nitriles in the presence of a rhodium catalyst, forming
indolizines, imidazopyridines and imidazoles, respectively. Benzo-
triazoles have also been utilised in palladium-catalysed reactions
with alkynes to provide indoles.4 On the other hand, we have
found that nickel-catalysed denitrogenative alkyne insertion reac-
tions of 1,2,3-benzotriazin-4(3H)-ones give a wide range of sub-
stituted 1(2H)-isoquinolines in high yields.5 We then envisaged
that an analogous denitrogenative reaction of N-sulfonyl-1,2,3-
triazoles with alkynes could be feasible, if the diazo tautomers
could add to nickel(0) with extrusion of molecular nitrogen,
providing a reactive nickel-carbenoid species.6 We report herein
nickel-catalysed denitrogenative alkyne insertion reactions of
N-sulfonyl-1,2,3-triazoles, which present a new approach to the
preparation of substituted pyrroles.7
81 (73)
Determined by 1H NMR using CHCl2CHCl2 as an internal
standard. Isolated yields are given in parentheses.
a
A possible reaction pathway for the production of 3aa from
1a and 2a is depicted in Scheme 1. Initially, a ring–chain
tautomerisation of N-sulfonyl-1,2,3-triazole 1a occurs to
generate a-imino diazo compound 1a0,10 although the equili-
brium lies far to the left. Diazo compound 1a0 adds to
nickel(0), with release of molecular nitrogen, to give nickel-
carbenoid A, which then cyclises to form azanickelacycle A0.
Subsequent insertion of alkyne 2a into the Ni–C bond leads to
six-membered ring nickelacycle B. Finally, reductive elimina-
tion affords 3aa, regenerating the nickel(0) catalyst. Possible
effects of the LA catalysts may be (1) promoting the formation
of a-imino diazo species 1a0, and/or (2) accelerating the
reductive elimination,11 although we have no experimental
results to support either of these postulates.
The starting materials, 4-substituted 1-(N-tosyl)-1,2,3-triazoles,
could be readily prepared by a copper-catalysed azide/alkyne
cycloaddition.8 When 4-phenyl-1-(N-tosyl)-1,2,3-triazole (1a) was
treated with dec-5-yne (2a, 2 equiv.), Ni(cod)2 (10 mol%) and
PMe3 (20 mol%) in toluene at 100 1C for 12 h, only a trace
of the desired pyrrole, 3aa, was obtained (Table 1, entry 1).
However, the use of sterically-hindered phosphine ligands
increased the yield up to 51% (Table 1, entries 2–4). Next, the
effect of Lewis acid (LA) catalysts as additives was examined
(Table 1, entries 5–8).9 It was found that the reaction in the
presence of AlPh3 (5 mol%) gave 3aa in 73% isolated yield.
Under optimised reaction conditions,
a variety of
N-sulfonyltriazoles, 1b–j, reacted with 2a to furnish substituted
Department of Synthetic Chemistry and Biological Chemistry,
Kyoto University, Katsura, Kyoto 615-8510, Japan.
E-mail: murakami@sbchem.kyoto-u.ac.jp; Fax: +81 75 383 2748;
Tel: +81 75 383 2747
w Electronic supplementary information (ESI) available: General
experimental information and spectral data. See DOI: 10.1039/b819162j
Scheme 1 Proposed reaction pathway.
ꢀc
This journal is The Royal Society of Chemistry 2009
1470 | Chem. Commun., 2009, 1470–1471

Table 2 The Nickel(0)-catalysed alkyne insertion reactions of 1 with
2a
This work was supported in part by the Mitsubishi Chemical
Corporation Fund, the Sumitomo Foundation and the Ministry
of Education, Culture, Sports, Science and Technology of Japan
(Grant-in-Aid for Scientific Research (A) (no. 19205013)).
M. Y. acknowledges financial support by the Global COE
Program ‘‘Integrated Materials Science’’ (no. B-09).
Notes and references
z General procedure: In a glove box, 1 (0.20 mmol) and AlPh3 (2.6 mg,
10 mmol) were charged into an oven-dried 4 mL vial equipped with a
stirring bar. A solution of Ni(cod)2 (5.5 mg, 20 mmol) and P(n-Bu)Ad2
(14.3 mg, 40 mmol) in toluene (2 mL), and 2 (0.40 mmol), were added.
The vial was then capped with a Teflon film and removed from the
glove box. The reaction mixture was heated at 100 1C for 12 h. After
this time, the reaction mixture was cooled to room temperature and
stirred in open air for 30 min. The resulting mixture was passed
through a pad of Florisil and eluted with ethyl acetate. The filtrate
was concentrated under reduced pressure. The residue was purified by
preparative thin layer chromatography (hexane/dichloromethane) to
give product 3.
Entry
1
R1
R2
3
Yield (%)a
1
2
3
4
5
6
7
8
9
10
1b
1c
1d
1e
1f
1g
1h
1i
Ph
Ph
Ph
Ph
Ph
3ba
3ca
3da
3ea
3fa
3ga
3ha
3ia
65
46
56b
58b
64
64c
59b
54
58
5
4-F-C6H4
4-MeO-C6H4
2-Naphthyl
Tol
Tol
Tol
Tol
Tol
Tol
Tol
4-CF3-C6H4
4-MeO-C6H4
4-Ph-C6H4
2-Naphthyl
n-Hexyl
1j
1k
3ja
3ka
1 For recent reviews, see: (a) D. M. D’Souza and T. J. J. Muller,
´
¨
Chem. Soc. Rev., 2007, 36, 1095; (b) M. Alvarez-Corral,
a
b
Isolated yield. Ni(cod)2 (15 mol%) and P(n-Bu)Ad2 (30 mol%)
c
were used. 110 1C.
M. Munoz-Dorado and I. Rodrıguez-Garcıa, Chem. Rev., 2008,
´ ´
108, 3174; (c) N. T. Patil and Y. Yamamoto, Chem. Rev., 2008,
108, 3395.
2 (a) S. Chuprakov, F. W. Hwang and V. Gevorgyan, Angew. Chem.,
Int. Ed., 2007, 46, 4757; (b) For the related rhodium-catalysed
cyclopropanation of pyridotriazoles, see: S. Chuprakov and
V. Gevorgyan, Org. Lett., 2007, 9, 4463.
Table 3 Denitrogenative alkyne insertion reactions of 1a with 2
3 T. Horneff, S. Chuprakov, N. Chernyak, V. Gevorgyan and
V. V. Fokin, J. Am. Chem. Soc., 2008, 130, 14972.
4 N. Shiraiwa, T. Nemoto, I. Nakamura and M. Terada, in The 55th
Symposium on Organometallic Chemistry, The Kinki Chemical
Society (Osaka, Japan), Osaka, Japan, September 28–30, 2008,
P3A-11.
5 T. Miura, M. Yamauchi and M. Murakami, Org. Lett., 2008, 10,
3085.
Entry
2
R1
R2
3
Yield (%)a
6 For reactions of diazoalkanes with a nickel(0) catalyst, see:
(a) A. Nakamura, T. Yoshida, M. Cowie, S. Otsuka and
J. A. Ibers, J. Am. Chem. Soc., 1977, 99, 2108;
(b) D. J. Mindiola and G. L. Hillhouse, J. Am. Chem. Soc.,
2002, 124, 9976.
1
2
3
4
5
2b
2c
2d
2e
2f
n-Pr
Ph
Me
Me
n-Pr
Ph
i-Pr
SiMe3
n-Bu
3ab
3ac
3ad
3ae
3af
68
31
68 (50 : 50)
48 (58 : 42)b
37 (57 : 43)b
7 For recent reports on the synthesis of substituted pyrroles, see:
(a) M. R. Rivero and S. L. Buchwald, Org. Lett., 2007, 9, 973;
(b) M. Shindo, Y. Yoshimura, M. Hayashi, H. Soejima,
T. Yoshikawa, K. Matsumoto and K. Shishido, Org. Lett., 2007,
9, 1963; (c) H. Dong, M. Shen, J. E. Redford, B. J. Stokes,
A. L. Pumphrey and T. G. Driver, Org. Lett., 2007, 9, 5191;
(d) C. V. Galliford and K. A. Scheidt, J. Org. Chem., 2007, 72,
1811; (e) V. Cadierno, J. Gimeno and N. Nebra, Chem.–Eur. J.,
2007, 13, 9973; (f) S. Chiba, Y.-F. Wang, G. Lapointe and
K. Narasaka, Org. Lett., 2008, 10, 313; (g) S. Cacchi, G. Fabrizi
and E. Filisti, Org. Lett., 2008, 10, 2629; (h) Y. Lu and
B. A. Arndtsen, Angew. Chem., Int. Ed., 2008, 47, 5430.
8 E. J. Yoo, M. Ahlquist, S. H. Kim, I. Bae, V. V. Fokin,
K. B. Sharpless and S. Chang, Angew. Chem., Int. Ed., 2007, 46,
1730.
Bpin
a
Isolated yield. The ratio of the regioisomers is shown in parentheses.
Ni(cod)2 (15 mol%) and P(n-Bu)Ad2 (30 mol%) were used.
b
pyrroles 3ba–ja in yields ranging from 46 to 65% (Table 2,
entries 1–9z). However, the reaction of alkyl-substituted
triazole 1k proceeded sluggishly to form the desired product,
3ka, in only 5% yield (Table 2, entry 10).
Various alkynes, 2, were subjected to the denitrogenative
insertion reaction with 1a (Table 3). Symmetrical alkynes such
as 4-octyne (2b) and diphenylethyne (2c) reacted to give 3ab and
3ac in 68 and 31% yields, respectively (Table 3, entries 1 and 2).
The reaction of unsymmetrical alkynes gave a mixture of
regioisomers (Table 3, entries 3–5). Terminal alkynes such as
oct-1-yne and phenylethyne failed to participate in the reaction,
presumably due to a rapid self-oligomerisation reaction.
In summary, we have demonstrated that the nickel-catalysed
denitrogenative alkyne insertion reactions of N-sulfonyltriazoles
provide a new synthetic route to substituted pyrroles from readily
available starting materials. In these reactions, the triazole moiety
is effectively activated by the combined use of nickel and a LA
catalyst.
9 For LA-accelerated reactions involving nickel(0) species, see:
(a) N. M. Brunkan, D. M. Brestensky and W. D. Jones, J. Am.
Chem. Soc., 2004, 126, 3627; (b) H. P. Hratchian,
S. K. Chowdhury, V. M. Gutierrez-Garcıa, K. K.
´ ´
D. Amarasinghe, M. J. Heeg, H. B. Schlegel and
J. Montgomery, Organometallics, 2004, 23, 4636; (c) S. Ogoshi,
M. Ueta, T. Arai and H. Kurosawa, J. Am. Chem. Soc., 2005, 127,
12810; (d) Y. Nakao, A. Yada, S. Ebata and T. Hiyama, J. Am.
Chem. Soc., 2007, 129, 2428.
10 (a) P. Grunanger and P. V. Finzi, Tetrahedron Lett., 1963, 4, 1839;
¨
(b) R. E. Harmon, F. Stanley, Jr, S. K. Gupta and J. Johnson,
J. Org. Chem., 1970, 35, 3444; (c) G. Himbert, D. Frank and
M. Regit, Chem. Ber., 1976, 109, 370.
11 Q. Shen and J. F. Hartwig, J. Am. Chem. Soc., 2007, 129, 7734.
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This journal is The Royal Society of Chemistry 2009
Chem. Commun., 2009, 1470–1471 | 1471