Rhodium-catalyzed three-component cross-addition of silylacetylenes, alkynyl esters, and electron-deficient alkenes or isocyanates

Article abstract of DOI:10.1002/anie.201204646

'Rh'oad crossing: A cationic Rh^I/(cod)₂ complex catalyzes the chemo-, regio-, and stereoselective title reaction with electron-deficient alkenes leading to substituted 1,3-dienes. The analogous three-component cross-addition involving isocyanates instead of alkenes has also been developed.

Full text of DOI:10.1002/anie.201204646

Angewandte
Chemie
DOI: 10.1002/anie.201204646
Multicomponent Reactions
Rhodium-Catalyzed Three-Component Cross-Addition of
Silylacetylenes, Alkynyl Esters, and Electron-Deficient Alkenes or
Isocyanates**
Yuki Hoshino, Yu Shibata, and Ken Tanaka*
The transition-metal-catalyzed hydroalkynylation of unsatu-
rated compounds with terminal alkynes has been extensively
studied for the atom-economical synthesis of functionalized
alkynes.[1] Although a number of the hydroalkynylation
reactions of alkynes,[2] allenes,[3] and alkenes[4] with terminal
alkynes has been reported, the cross-addition reactions of
terminal alkynes and two unsaturated compounds through
the formation of two C C bonds are rare.[5] In particular, the
ꢀ
reactions of terminal alkynes and two different unsaturated
compounds are difficult as a result of the challenge in
controlling the chemoselectivity.[6,7] Ogata, Fukuzawa, and
co-workers realized such challenging transformations by
using bulky triisopropylsilylacetylene as a terminal alkyne
and nickel(0)/phosphine complexes as catalysts.[6,7] In 2009,
Scheme 1. Transition-metal-catalyzed three-component cross-addition
of silylacetylenes, alkynes, and alkenes.
they reported the nickel-catalyzed three-component cross-
addition of triisopropylsilylacetylene and two different inter-
nal alkynes (R1, R2, R4 ¼ H, R3 = CH2OR5) by controlling the
chemoselective addition between two different internal
alkynes (Scheme 1a).[6a] In 2011, they realized the more
difficult cross-addition of two different terminal alkynes
[triisopropylsilylacetylene and terminal alkynes (R1 = alkyl,
R2 = H)] and internal alkynes (R3, R4 = Ar) by controlling the
Our research group previously reported that a cationic
rhodium(I)/(cod)2 (cod = 1,5-cyclooctadiene) complex is
a highly effective catalyst for the [2+2+1] cross-cyclotrime-
rization of silylacetylenes and two alkynyl esters, thus leading
to substituted silylfulvenes.[10,11] For example, triisopropyl-
silylacetylene (1a) reacted with two ethyl 2-butynoates (2a)
to give the corresponding silylfulvene 5aa in high yield
(Scheme 2).[10] Interestingly, the use of the sterically demand-
ꢀ
chemoselective C H bond activation between two different
terminal alkynes as well as the chemoselective addition
between the terminal and internal alkynes (Scheme 1a).[6b] In
2010, they also reported that norbornene is able to participate
in this three-component cross-addition to give the corre-
sponding 1,5-enynes (Scheme 1a).[7] However, the available
alkenes were unfortunately strictly limited to norbornene
derivatives. Herein, we report the unprecedented transition-
metal-catalyzed chemo-, regio-, and stereoselective three-
component cross-addition of silylacetylenes, alkynes, and
alkenes, thus leading to substituted 1,3-dienes (Scheme 1b)
by using cationic rhodium(I) complexes as catalysts.[8] The
analogous unprecedented three-component cross-addition
involving isocyanates in place of alkenes is also disclosed.[9]
Scheme 2. Rhodium-catalyzed reactions of triisopropylsilylacetylene
(1a) and alkynyl esters 2.
[*] Y. Hoshino, Y. Shibata, Prof. Dr. K. Tanaka
Department of Applied Chemistry, Graduate School of Engineering
Tokyo University of Agriculture and Technology
Koganei, Tokyo 184-8588 (Japan)
E-mail: tanaka-k@cc.tuat.ac.jp
Homepage: http://www.tuat.ac.jp/~tanaka-k/
[**] This work was supported partly by Grants-in-Aid for Scientific
Research (Nos. 23105512, 20675002, and 21·906) from the MEXT
(Japan). We thank Umicore for generous support in supplying
rhodium complexes.
ing methyl 4,4-dimethyl-2-butynoate (2b) in place of 2a did
not afford the cross-cyclotimerization product 5aa, but
instead delivered the cross-dimerization product 3ab[2g] as
a major product along with the linear cross-trimerization
product 4ab,[5k] which was generated from 2b and two units of
1a, as a minor product (Scheme 2).
We anticipated that when adding an excess of an electron-
deficient alkene, this alkene would be incorporated into the
product as a third component in place of 1a. Pleasingly, the
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201204646.
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binaphthyl] and [{RhCl(cod)}2] failed to catalyze the reaction
(entries 11 and 12). Interestingly, changing the counter anion
from ꢀBF4 to ꢀOTf (entry 13) or ꢀSbF6 (entry 14) completely
suppressed the formation of 8aba, and the use of [Rh-
(cod)2]SbF6 furnished 7aba in the highest yield (entry 14).
However, the use of BArF as the counter anion significantly
suppressed the substrate conversion (entry 15). Increasing the
amount of 6a improved the selectivity of 7aba over 3ab, but
the reaction rate decreased (entry 16). Elevating the reaction
temperature to 808C increased the reaction rate and further
improved the yield of 7aba (entry 17).
Scheme 3. Rhodium-catalyzed reactions of triisopropylsilylacetylene
(1a), the alkynyl ester 2b, and acrylate 6a.
The scope of this rhodium(I)-catalyzed three-component
cross-addition was examined as shown in Scheme 4.[12] With
respect to electron-deficient alkenes, various acrylates (6a–c)
and methyl vinyl ketone (6d) were suitable substrates for this
process, while the use of N,N-dimethylacrylamide (6e)
lowered the yield of the corresponding three-component
cross-addition product. With respect to the silylacetylenes,
not only triisopropylsilylacetylene (1a) but also tert-butyldi-
phenyl- and tert-butyldimethylsilylacetylenes (1b and 1c,
respectively) could be employed, although excess 6d
(20 equiv) was required. With respect to the alkynyl esters,
tertiary-alkyl- (2b), secondary-alkyl- (2c,d), primary-alkyl-
(2e–g), and aryl-substituted (2h,i) alkynyl esters could react
with 1a and excess 6d (20 equiv) to give the corresponding
three-component cross-addition products in moderate to
good yields. Importantly, these reactions proceeded with
complete regio- and stereoselectivity. Interestingly, the reac-
tions of propargyl acetates 2j,k proceeded at room temper-
ature to give the corresponding three-component cross-
addition products in good yields, although that of benzoate
2l required an elevated temperature. The use of the less
Lewis-acidic [Rh(cod)2]BF4 in place of [Rh(cod)2]SbF6 was
necessary to avoid the undesired elimination of carboxylic
acids. In these reactions, stereoselectivities were opposite to
those using 2b–i.
reaction of 1a, 2b, and butyl acrylate (6a, 2 equiv; Scheme 3)
at 608C afforded the expected three-component cross-addi-
tion product 7aba along with the corresponding dehydro-
genated product 8aba, however, the major product was the
cross-dimerization product 3ab.
To improve the yield of 7aba, the effect of the solvents
was first examined (entries 1–6, Table 1). Ether solvents were
Table 1: Effect of catalysts and solvents on reaction of 1a, 2b, and 6a.[a]
Entry Catalyst
Solvent
Yield [%][b]
7aba 8aba 3ab
1
2
3
4
5
6
7
8
[Rh(cod)2]BF4
[Rh(cod)2]BF4
[Rh(cod)2]BF4
[Rh(cod)2]BF4
[Rh(cod)2]BF4
[Rh(cod)2]BF4
[{RhCl(cod)}2]/2AgBF4
[{IrCl(cod)}2]/2AgBF4
[Rh(nbd)2]BF4
[{RhOAc(cod)}2]
[Rh(cod)2]BF4/rac-binap
[{RhCl(cod)}2]
[Rh(cod)2]OTf
[Rh(cod)2]SbF6
[{RhCl(cod)}2]/2NaBArF
[Rh(cod)2]SbF6
1,4-dioxane 20
11
14
6
0
3
0
7
0
6
8
0
0
0
0
2
0
0
43
26
49
48
39
0
24
49
58
41
0
THF
32
16
0
0
0
DME
(CH2Cl)2
toluene
CH3CN
THF
30
0
THF
9
THF
0
10
11
12
13
14
15
16[d]
THF
7
THF
0
THF
0
0
THF
THF
THF
31
46
0
14
31
0
10
16
As the third addition component, isocyanates could be
employed in place of electron-deficient alkenes by using the
less Lewis-acidic [Rh(cod)2]BF4 as a catalyst (Scheme 5).[13]
The primary and secondary alkyl isocyanates 8a,b reacted
with 1a and 2b to give the corresponding enyne amides 9, and
the use of the arylisocyanates 8c–e improved the product
yields. Although the product yield decreased, tert-butyldiphe-
nylsilylacetylene (1b) could also be employed.
[c]
THF
THF
62
74
17[d,e] [Rh(cod)2]SbF6
[a] Reactions were conducted using the catalyst (0.010 mmol of metal),
1a (0.11 mmol), 2b (0.10 mmol), 6a (0.20 mmol), and solvent (2.0 mL)
1
at 608C for 16 h. [b] Determined by H NMR spectroscopy.
[c] NaBArF =sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.
[d] 6a: 5 equiv. [e] At 808C. DME=1,2-dimethoxyethane, THF=tetra-
hydrofuran.
A mechanistic proposal for this rhodium(I)-catalyzed
three-component cross-addition reaction is shown in
Scheme 6. Carborhodation of the alkynyl ester 2 with the
rhodium acetylide A, generated by the reaction of the
silylacetylene 1[14] and the cationic rhodium(I) complex,
affords the (alkenyl)rhodium B, which reacts with electron-
deficient alkene 6 to generate the intermediate C. Protona-
tion of C affords the 1,3-enyne 7 and regenerates the
rhodium(I) catalyst. The isocyanete 8 is also able to react
with the (alkenyl)rhodium B to give the intermediate D, the
protonation of which affords the enyne amide 9. In contrast,
the reaction of the rhodium acetylide A with the propargyl
ester 2 [R1 = CR5R6(OCOR7)] affords the (alkenyl)rhodium
E, in which the carbonyl oxygen atom coordinates to
rhodium, through E/Z isomerization of B.[15] This intermedi-
effective for this transformation (entries 1–3) and the use of
THF furnished 7aba in the highest yield (entry 2). However,
less-coordinating solvents (entries 4 and 5) and a highly
coordinating solvent (entry 6) did not furnish 7aba at all.
Next, the effect of catalysts was examined (entries 7–14). An
in situ generated cationic rhodium(I)/cod complex catalyzed
the formation of 7aba as well as a significant amount of the
oligomerization products from 1a (entry 7). The use of
a cationic iridium(I)/cod complex, [Rh(nbd)2]BF4, and [{Rh-
(cod)OAc}2] predominantly furnished the cross-dimerization
product 3ab (entries 8–10). The use of a cationic rhodium(I)/
rac-binap complex [binap = 2,2’-bis(diphenylphosphino)-1,1’-
2
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Scheme 5. Three-component cross-addition of silylacetylenes 1a,b,
alkynyl ester 2b, and isocyanates 8a–e. Reaction conditions: [Rh-
(cod)2]BF4 (0.010 mmol), 1a,b (0.22 mmol), 2b (0.20 mmol), 8a–
e (1.0 mmol), and THF (2.0 mL) were used. Reported yields are of
those of the isolated products.
Scheme 4. Three-component cross-addition of silylacetylenes 1a–c,
alkynyl esters 2b–l, and electron-deficient alkenes 6a–e. Reaction
conditions: [Rh(cod)2]SbF6 (0.010 mmol), 1a–c (0.22 mmol), 2b–
l (0.20 mmol), 6a–e (1.0–4.0 mmol), and THF (2.0 mL) were used.
Cited yields are of isolated products. [a] [Rh(cod)2]BF4 (0.010 mmol)
was used. Bz=benzoyl.
ate E reacts with 6 to give the intermediate F, subsequent
protonation of which affords the 1,3-enyne 7’.
Scheme 6. Proposed reaction mechanism.
Transformations of the present three-component cross-
addition products were briefly examined as shown in
Scheme 7. Treatment of the 1,3-enynes 7abd and 7aed with
TBAF (tetra-n-butylammonium fluoride) furnished the ter-
minal alkynes 10a and 10b, respectively, in good to high
yields. The palladium-catalyzed Sonogashira cross-coupling
of 10a with iodobenzene furnished the phenylacetylene
derivative 11 in high yield. Alternatively, the rhodium(I)/H8-
binap
[2,2’-bis(diphenylphospino)-5,5’,6,6’,7,7’,8,8’-octahy-
dro-1,1’-binaphthyl] complex catalyzed [2+2+2] cycloaddi-
tion of 10b with the 1,6-diyne 12 to furnish the densely
substituted benzene 13 in good yield. In contrast, treatment of
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l) N. Matsuyama, K. Hirano, T. Satoh, M. Miura, J. Org. Chem.
2009, 74, 3576.
[3] a) B. M. Trost, G. Kottirsch, J. Am. Chem. Soc. 1990, 112, 2816;
b) M. Yamaguchi, K. Omata, M. Hirama, Tetrahedron Lett. 1994,
35, 5689; c) M. Yamaguchi, Y. Kido, K. Omata, M. Hirama,
Synlett 1995, 1181; d) D. Bruyere, R. Grigg, J. Hinsley, R. K.
Hussain, S. Korn, C. O. De La Cierva, V. Sridharan, J. Wang,
Tetrahedron Lett. 2003, 44, 8669; e) M. Rubin, J. Markov, S.
Chuprakov, D. J. Wink, V. Gevorgyan, J. Org. Chem. 2003, 68,
6251; f) T. Nishimura, X.-X. Guo, T. Hayashi, Chem. Asian J.
2008, 3, 1505; g) X.-X. Guo, T. Sawano, T. Nishimura, T.
Hayashi, Tetrahedron: Asymmetry 2010, 21, 1730.
[4] a) G. I. Nikishin, I. P. Kovalev, Tetrahedron Lett. 1990, 31, 7063;
b) R. V. Lerum, J. D. Chisholm, Tetrahedron Lett. 2008, 49, 1505;
c) A. Tenaglia, L. Giordano, G. Buono, Org. Lett. 2006, 8, 4315;
d) J. Yin, J. D. Chisholm, Chem. Commun. 2006, 632; e) T.
Nishimura, X.-X. Guo, N. Uchiyama, T. Katoh, T. Hayashi, J.
Am. Chem. Soc. 2008, 130, 1576; f) M. Shirakura, M. Suginome,
J. Am. Chem. Soc. 2008, 130, 5410; g) M. Shirakura, M.
Suginome, Org. Lett. 2009, 11, 523; h) K. Kohno, K. Nakagawa,
T. Yahagi, J.-C. Choi, H. Yasuda, T. Sakakura, J. Am. Chem. Soc.
2009, 131, 2784; i) M. Shirakura, M. Suginome, J. Am. Chem.
Soc. 2009, 131, 5060; j) E. Fillion, A. K. Zorzitto, J. Am. Chem.
Soc. 2009, 131, 14608; k) T. Nishimura, T. Sawano, T. Hayashi,
Angew. Chem. 2009, 121, 8201; Angew. Chem. Int. Ed. 2009, 48,
8057; l) T. Nishimura, T. Sawano, S. Tokuji, T. Hayashi, Chem.
Commun. 2010, 46, 6837; m) T. Nishimura, T. Sawano, K. Ou, T.
Hayashi, Chem. Commun. 2011, 47, 10142.
[5] a) M. Ishikawa, J. Ohshita, Y. Ito, A. Minato, J. Chem. Soc.
Chem. Commun. 1988, 804; b) H.-F. Klein, M. Mager, Organo-
metallics 1992, 11, 3174; c) H. Matsuzaka, Y. Takagi, Y. Ishii, M.
Nishio, M. Hidai, Organometallics 1995, 14, 2153; d) B. M. Trost,
M. T. Sorum, C. Chan, A. E. Harms, G. Rꢁhter, J. Am. Chem.
Soc. 1997, 119, 698; e) A. Haskel, T. Straub, A. K. Dash, M. S.
Eisen, J. Am. Chem. Soc. 1999, 121, 3014; f) A. Haskel, J. Q.
Wang, T. Straub, T. G. Neyrond, M. S. Eisen, J. Am. Chem. Soc.
1999, 121, 3025; g) A. K. Dash, I. Gourevich, J. Q. Wang, J.
Wang, M. Kapon, M. S. Eisen, Organometallics 2001, 20, 5084;
h) S.-i. Yoshimitsu, S. Hikichi, M. Akita, Organometallics 2002,
21, 3762; i) J. Q. Wang, M. S. Eisen, J. Organomet. Chem. 2003,
670, 97; j) M. V. Jimꢂnez, E. Sola, F. J. Lahoz, L. A. Oro,
Organometallics 2005, 24, 2722; k) N. Matsuyama, H. Tsurugi, T.
Satoh, M. Miura, Adv. Synth. Catal. 2008, 350, 2274; l) K. Ogata,
H. Murayama, J. Sugasawa, N. Suzuki, S.-i. Fukuzawa, J. Am.
Chem. Soc. 2009, 131, 3176.
Scheme 7. Transformations of three-component cross-addition prod-
ucts. Ts=4-toluenesulfonyl.
the enyne amide 9abc with TBAF furnished the desilylated
cyclization product 14 in high yield.
In conclusion, we have developed an unprecedented
rhodium-catalyzed chemo-, regio-, and stereoselective three-
component cross-addition of a silylacetylene, alkynyl ester,
and electron-deficient alkene, thereby leading to substituted
1,3-dienes. In addition, the analogous and unprecedented
three-component cross-addition involving isocyanates in
place of electron-deficient alkenes has also been developed.
Future work will focus on further exploitation of the catalytic
three-component cross-addition reactions by using the cat-
ionic rhodium(I) complexes as catalysts.
Received: June 14, 2012
Published online: && &&, &&&&
Keywords: alkenes · alkynes · multicomponent reactions ·
.
rhodium · synthetic methods
[6] a) K. Ogata, J. Sugasawa, S.-i. Fukuzawa, Angew. Chem. 2009,
121, 6194; Angew. Chem. Int. Ed. 2009, 48, 6078; b) K. Ogata, Y.
Atsuumi, S.-i. Fukuzawa, Org. Lett. 2011, 13, 122.
[7] K. Ogata, J. Sugasawa, Y. Atsuumi, S.-i. Fukuzawa, Org. Lett.
2010, 12, 148.
[1] For reviews, see: a) B. M. Trost, A. H. Weiss, Adv. Synth. Catal.
2009, 351, 963; b) S. Fujimori, T. F. Knçpfel, P. Zarotti, T.
Ichikawa, D. Boyall, E. M. Carreira, Bull. Chem. Soc. Jpn. 2007,
80, 1635; c) L. Zani, C. Bolm, Chem. Commun. 2006, 4263;
d) P. G. Cozzi, R. Hilgraf, N. Zimmermann, Eur. J. Org. Chem.
2004, 4095; e) C. Wei, Z. Li, C.-J. Li, Synlett 2004, 1472; f) L. Pu,
Tetrahedron 2003, 59, 9873; g) D. E. Frantz, R. Fꢀssler, C. S.
Tomooka, E. M. Carreira, Acc. Chem. Res. 2000, 33, 373.
[2] a) B. M. Trost, M. C. McIntosh, J. Am. Chem. Soc. 1995, 117,
7255; b) B. M. Trost, A. J. Frontier, J. Am. Chem. Soc. 2000, 122,
11727; c) L. Chen, C. Li, Tetrahedron Lett. 2004, 45, 2771; d) T.
Hirabayashi, S. Sakaguchi, Y. Ishii, Adv. Synth. Catal. 2005, 347,
872; e) H. Katayama, H. Yari, M. Tanaka, F. Ozawa, Chem.
Commun. 2005, 4336; f) J.-i. Ito, M. Kitase, H. Nishiyama,
Organometallics 2007, 26, 6417; g) T. Nishimura, X.-X. Guo, K.
Ohnishi, T. Hayashi, Adv. Synth. Catal. 2007, 349, 2669; h) T.
Katagiri, H. Tsurugi, A. Funayama, T. Satoh, M. Miura, Chem.
Lett. 2007, 36, 830; i) N. Tsukada, S. Ninomiya, Y. Aoyama, Y.
Inoue, Org. Lett. 2007, 9, 2919; j) T. Katagiri, H. Tsurugi, T.
Satoh, M. Miura, Chem. Commun. 2008, 3405; k) K. Ogata, O.
Oka, A. Toyota, N. Suzuki, S.-i. Fukuzawa, Synlett 2008, 2663;
[8] For precedented examples of the transition-metal-catalyzed
intermolecular reactions involving successive insertion of inter-
nal alkynes and alkenes, see: a) K. Shibata, T. Satoh, M. Miura,
Org. Lett. 2005, 7, 1781; b) T. Kurahashi, H. Shinokubo, A.
Osuka, Angew. Chem. 2006, 118, 6484; Angew. Chem. Int. Ed.
2006, 45, 6336; c) H, Horiguchi, K. Hirano, T. Satoh, M. Miura,
Adv. Synth. Catal. 2009, 351, 1431.
[9] For precedented examples of the transition-metal-catalyzed
intermolecular reactions involving the arylmetalation of isocya-
nates, see: a) T. Koike, M. Takahashi, N. Arai, A. Mori, Chem.
Lett. 2004, 33, 1364; b) T. Miura, Y. Takahashi, M. Murakami,
Chem. Commun. 2007, 3577; c) Y. Kuninobu, K. Kikuchi, Y.
Tokunaga, Y. Nishina, K. Takai, Tetrahedron 2008, 64, 5974;
d) K. D. Hesp, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc.
2011, 133, 11430.
[10] Y. Shibata, K. Tanaka, Angew. Chem. 2011, 123, 11109; Angew.
Chem. Int. Ed. 2011, 50, 10917.
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[11] Our research group reported the rhodium(I)-catalyzed cross-
trimerization of propargyl esters and two arylacetylenes leading
to substituted dihydropentalenes, a reaction initiated by the
hydroalkynylation of propargyl esters with arylacetylenes. See:
Y. Shibata, K. Noguchi, K. Tanaka, Org. Lett. 2010, 12, 5596.
[12] When the yields of the desired products 7 were low, the following
cross-dimerization products 3 or cross-timerization products 5
were generated as major by-products: 7abe (3ab: 71%), 7cbd
(3cb: 33%), 7add (5ad: 35%), 7afd (5af: 31%), 7agd (5ag:
46%), 7aid (5ai: 14%), 7ald (5al: 21%).
[13] The following cross-dimerization products 3 and cross-time-
rization products 4 were generated as major by-products: 9aba
(3ab: 14% and 4ab: 11%), 9abb (3ab: 28% and 4ab: 40%),
9abc (3ab: 35% and 4ab: 9%), 9abd (3ab: 22% and 4ab:
12%), 9abe (3ab: 44% and 4ab: 7%), 9bbc (3bb: 24% and
4bb: 40%).
[14] For examples of the formation of rhodium acetylides from
silylacetylenes, see: Ref. [2g].
[15] We believed that this isomerization step from the intermediate B
to intermediate E might be irreversible.
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Communications
Multicomponent Reactions
Y. Hoshino, Y. Shibata,
K. Tanaka*
&&&& — &&&&
Rhodium-Catalyzed Three-Component
Cross-Addition of Silylacetylenes, Alkynyl
Esters, and Electron-Deficient Alkenes or
Isocyanates
’Rh’oad crossing: A cationic RhI/(cod)2
complex catalyzes the chemo-, regio-, and
stereoselective title reaction with elec-
tron-deficient alkenes leading to substi-
tuted 1,3-dienes. The analogous three-
component cross-addition involving iso-
cyanates instead of alkenes has also been
developed.
6
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