Rhenium(I)-Catalyzed Generation of α,β-Unsaturated Carbene Complex Intermediates from Propargyl Ethers for the Preparation of Cycloheptadiene Derivatives

Article abstract of DOI:10.1002/anie.201604371

The rhenium(I)-catalyzed generation of α,β-unsaturated carbene complex intermediates from easily available propargyl ethers was achieved for the concise construction of cycloheptadiene derivatives through the formal [4+3] cycloaddition reaction with silox

Full text of DOI:10.1002/anie.201604371

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International Edition: DOI: 10.1002/anie.201604371
German Edition: DOI: 10.1002/ange.201604371
Cycloaddition Reactions
Rhenium(I)-Catalyzed Generation of a,b-Unsaturated Carbene
Complex Intermediates from Propargyl Ethers for the Preparation of
Cycloheptadiene Derivatives
Hideyuki Sogo and Nobuharu Iwasawa*
Abstract: The rhenium(I)-catalyzed generation of a,b-unsa-
turated carbene complex intermediates from easily available
propargyl ethers was achieved for the concise construction of
cycloheptadiene derivatives through the formal [4+3] cyclo-
addition reaction with siloxydienes.
C
atalytic generation of a,b-unsaturated carbene complex
intermediates through electrophilic activation of alkynes has
attracted much attention as a useful method for the reaction
of novel three-carbon reactive species.[1–4] In these reactions,
the nucleophilic addition of appropriate internal nucleophiles
onto alkynes having a leaving group at the propargylic
position, followed by electron donation from the metal to
release the leaving group, generates a-Nu-substituted a,b-
unsaturated carbene complex intermediates (Scheme 1).
Scheme 2. Generation of a,b-unsaturated carbene complex intermedi-
ates from propargyl ethers.
utilization as a three-carbon unit for the concise preparation
of cycloheptadiene derivatives.
The reaction was examined with various metal catalysts
using the benzyl ether of 1,1-dimethyl-2-propyn-1-ol 1a and
1.5 molar amounts of 4-aryl-2-siloxy-1,3-butadiene 2a as
a carbene trapping reagent expecting the formation of
cycloheptadiene 3a as [4+3]-cycloadduct (Table 1).[4i,j] It
was found that ReX(CO)5 and PtCl2 were the active catalyst
for this reaction, and the desired product 3a was obtained by
carrying out of the reaction in 1,4-dioxane at 1008C along
with a small amount of its olefinic isomerization product
Scheme 1. Generation of a,b-unsaturated carbene complex intermedi-
ates.
We then thought of the possibility of using easily available
propargyl ethers as substrate for catalytic generation of a,b-
unsaturated carbene complex intermediates with the expect-
ation that hydride transfer from the ether moiety would be
promoted by electron donation from the lone pair of the
oxygen atom (Scheme 2).[5–8] For generation of a,b-unsatu-
rated carbene complex intermediates, the reaction necessi-
tates 1,4-hydride transfer onto the p-alkyne complex A, which
is rather rare in such systems,[6,9] and we also thought of
examining the possibility of 1,5-hydride transfer through
vinylidene intermediate B, which has several precedents as
a stoichiometric reaction for preparation of metathesis
catalysts.[10–13] These hydride transfers would generate the
same intermediate C containing an oxonium moiety, which
would work as an efficient leaving group for carbene
generation. Herein, we report our successful realization of
this concept for catalytic generation of simple a,b-unsatu-
rated carbene complexes from propargyl ethers and their
Table 1: Examination of various reaction conditions.
Entry
Metal cat.
Time [h]
3a+4a [%][a]
3a:4a[b]
1
2
3
4
PtCl2
12
12
4
2
4
33
62
84
96
97
75
90
93:7
>95:5
95:5
>95:5
>95:5
61:39
ReCl(CO)5
ReBr(CO)5
ReI(CO)5
ReI(CO)5
ReI(CO)5
ReI(CO)5
5[c]
6[c,d]
7[c,d,e]
4
4
>95:5
[*] H. Sogo, Prof. Dr. N. Iwasawa
Department of Chemistry, Tokyo Institute of Technology
2-12-1, O-okayama, Meguro-ku, Tokyo 152-8551 (Japan)
E-mail: niwasawa@chem.titech.ac.jp
Reaction conditions : 1a (0.10 mmol), 2a (0.15 mmol), and Metal cat.
(0.01 mmol) in 1,4-dioxane (2.0 mL) at 1008C. [a] Yield of isolated
product. [b] Determined by 1H NMR spectroscopy. [c] 0.10m of 1a and
2.5 mol% of ReI(CO)5 were used. [d] 1.0 equiv of 2a was used.
[e] Activated 4ꢀ M.S. were used.
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/anie.201604371.
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4a.[14] Formation of bezaldehyde was noted in these reactions.
Table 3: Examination of various propargyl ethers.
Among several ReX(CO)5, ReI(CO)5 gave the best result
(entries 1–4), and even 2.5 mol% of ReI(CO)5 afforded the
cycloheptadiene 3a in 97% yield (entry 5). Even an equi-
molar amount of propargyl ether 1a and siloxydiene 2a gave
the desired product 3a in good yield by carrying out the
reaction in the presence of activated 4ꢀ M.S.(entries 6 and
7).[15]
Entry
Propargyl ethers
Yield [%]
Generality of the reaction with various 2-siloxydienes 2
was examined using propargyl benzyl ether 1a under the
optimized conditions (Table 2). Various 4-aryl substituted 2-
1[a]
2[b]
R1 =C14H29
R1 =THP
1b
1c
3a
3a
90
59
3
X=CH2
X=NBoc
5a
5b
6a
6b
80
65
4[b]
Table 2: Examination of various siloxydienes.
5[c]
5c
5d
6c
6d
87
69
6[b]
75
7[c]
8[d]
R2 =iPr
R2 =Me
5e
5 f
6e
6 f
(cis/trans 79:21)[e]
69
Entry
1
R1
H
R2
Yield [%]
90
(cis/trans 77:23)[e]
9[d,f]
5g
6g
58[g]
2a
3a
2
3
4
5
6
H
H
H
H
H
Ph
2b
2c
2d
2e
2 f
3b
3c
3d
3e
3 f
86
88
86
92
63
[a] For 6 h. [b] For 12 h. [c] For 8 h. [d] 5 mol% Re catalyst was used.
[e] The ratio was determined by 1H NMR spectroscopy. [f] 1.5 equiv of 2a
was used. [g] Obtained as a mixture with 7g. The yield was determined by
1H NMR spectroscopy.
p-MeOC6H4
p-BrC6H4
2,5-(MeO)2C6H3
2-furyl
7
H
2g
3g
88
acetal, and silyl ether were compatible under the reaction
conditions, and desired products were obtained without
problem (entries 4–6). Secondary propargyl ether gave the
corresponding product with reasonable diastereoselectivity
(entries 7 and 8). More importantly, a simple propargyl ether
itself gave the corresponding product in reasonable yield
(entry 9). In this case, formation of methylene cyclohexane
derivative 7g in 17% yield was also noted.[16]
8
H
2h
3h
82
9
10
H
H
nPr
iPr
2i
2j
3i
3j
77
85
11
H
2k
2l
3k
3l
93
72
12[a]
C2H4OBOM[b]
H
To obtain information on the mechanism of the reaction,
several control experiments were carried out. First, the
reaction of 5c with silyl enol ether 8 was examined under
the standard reaction conditions, and cyclopropane 9 was
obtained in good yield, confirming generation of the a,b-
unsaturated carbene complex intermediate (Scheme 3). Next,
a deuterium labeling experiment was carried out (Scheme 4).
When propargyl ether [D]-1a with the hydrogen atom of the
terminal alkyne deuterated was employed as substrate, the
deuterium was introduced onto C-5 position of the product
[D]-3a. This result clearly showed that the reaction proceeded
through the vinylidene intermediate in which terminal
deuterium transferred to the internal position. Based on
13[c]
2m
3m
91
[a] The reaction was carried out for 12 h. [b] BOM=benzyloxymethyl.
[c] The reaction was carried out for 8 h. [d] That is, R1,R2 =(CH2)4.
siloxy-1,3-dienes such as electron-donating and electron-
withdrawing phenyl, furyl, and indolyl groups underwent
the reaction smoothly to give the products in high yield
(entries 1–7). 4-Alkenyl and 4-alkyl-2-siloxy-1,3-dienes also
gave the corresponding cycloheptadienes 3 in good yield
(entries 8–11). Even 3-alkyl- and 3,4-dialkyl-substituted 2-
siloxy-1,3-dienes were also employable without problem
(entries 12 and 13). All these reactions proceeded by heating
just an equimolar mixture of 1a and 2 to give synthetically
useful cycloheptadiene derivatives 3 in good yield.
The result of the examination of the generality of the
propargyl ethers is shown in Table 3. Various ethers such as
alkyl and THP ethers were also employable to give the
product 3a in good yield (entries 1 and 2). A propargyl ether
containing cyclohexane moiety gave a spirocyclic product in
good yield (entry 3). Functional groups such as carbamate,
Scheme 3. Cyclopropanation of silyl enol ether.
2
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with Customized Scaffolding” (No. 15H05800) from the
Ministry of Education, Culture, Sports, Science, and Tech-
nology of Japan. H.S. thanks JSPS for a fellowship.
Keywords: cycloaddition reactions · propargyl ether · rhenium ·
unsaturated carbene complex · vinylidene
[1] For recent reviews of generation of a-acyloxy-a,b-unsaturated
carbene complexes by transition-metal-catalyzed 1,2-acyloxy
migration, see: a) K. Miki, S. Uemura, K. Ohe, Chem. Lett. 2005,
34, 1068 – 1073; b) N. Marion, G. Lemiꢁre, A. Correa, C.
Costabile, R. S. Ramꢂn, X. Moreau, P. Frꢃmont, R. Dahmane,
A. Hours, D. Lesage, J.-C. Tabet, J.-P. Goddard, V. Gandon, L.
Cavallo, L. Fensterbank, M. Malacria, S. P. Nolan, Chem. Eur. J.
2009, 15, 3243 – 3260; c) X.-Z. Shu, D. Shu, C. M. Schienebeck,
W. Tang, Chem. Soc. Rev. 2012, 41, 7698 – 7711; d) L. Fenster-
bank, M. Malacria, Acc. Chem. Res. 2014, 47, 953 – 965.
[2] For other examples for generation of a,b-unsaturated carbene
complexes based on electrophilic activation of alkynes using
metal catalysts, see: a) L. Peng, X. Zhang, S. Zhang, J. Wang, J.
Org. Chem. 2007, 72, 1192 – 1197; b) G. Zhang, L. Zhang, J. Am.
Chem. Soc. 2008, 130, 12598– 12599; c) R. Sanz, D. Miguel, M.
Gohain, P. Garcꢄa-Garcꢄa, M. A. Fernꢅndez-Rodrꢄguez, A.
Gonzꢅlez-Pꢃrez, O. Nieto-Faza, ꢆ. R. de Lera, F. Rodrꢄguez,
Chem. Eur. J. 2010, 16, 9818 – 9828; d) K. Saito, H. Sogou, T.
Suga, H. Kusama, N. Iwasawa, J. Am. Chem. Soc. 2011, 133, 689 –
691; e) P. A. Allegretti, E. M. Ferreira, Org. Lett. 2011, 13, 5924 –
5927; f) P. A. Allegretti, E. M. Ferreira, Chem. Sci. 2013, 4,
1053 – 1058; g) Y. Kwon, I. Kim, S. Kim, Org. Lett. 2014, 16,
4936 – 4939; h) X. Li, H. Li, W. Song, P.-S. Tseng, L. Liu, I. A.
Guzei, W. Tang, Angew. Chem. Int. Ed. 2015, 54, 12905 – 12908;
Angew. Chem. 2015, 127, 13097 – 13100.
[3] For representative examples of cyclopropanation reaction by
using unsaturated carbene complexes, see Ref. [1] and the
following: a) D. Qian, J. Zhang, Chem. Soc. Rev. 2015, 44,
677 – 698; b) V. Rautenstrauch, J. Org. Chem. 1984, 49, 950 – 952;
c) E. Mainetti, V. Mouriꢁs, L. Fensterbank, M. Malacria, J.
Marco-Contelles, Angew. Chem. Int. Ed. 2002, 41, 2132 – 2135;
Angew. Chem. 2002, 114, 2236 – 2239; d) Y.-W. Sun, X.-Y. Tang,
M. Shi, Chem. Commun. 2015, 51, 13937 – 13940.
Scheme 4. Deuterium labeling experiments.
these results, the total mechanism of the reaction was shown
in Scheme 4. Thus, one or two of the carbonyl ligands of
ReX(CO)5 are liberated by heating and vinylidene inter-
mediate D is generated by the reaction with propargyl
ether.[17] Then 1,5-hydride transfer of the benzylic hydrogen
onto the vinylidene carbon followed by elimination of
benzaldehyde generates a,b-unsaturated carbene complex
intermediate E.[18] This intermediate reacts with siloxydiene
to give divinylcyclopropane F, which undergoes Cope rear-
rangement to give the product.[19]
In conclusion, a very concise and practical method for
generation of simple a,b-unsaturated carbene complex inter-
mediates is realized by the reaction of easily available
propargyl ethers with a catalytic amount of ReI(CO)5.
Further intermolecular addition reaction with siloxydienes
efficiently gives synthetically useful silyloxycycloheptadienes
in high yields.
[4] For representative examples of other cycloaddition reactions of
unsaturated carbene complexes generated from alkyne sub-
strates using electrophilic metal catalysts, see: a) N. D. Shapiro,
F. D. Toste, J. Am. Chem. Soc. 2008, 130, 9244 – 9245; b) N. D.
Shapiro, Y. Shi, F. D. Toste, J. Am. Chem. Soc. 2009, 131, 11654 –
11655; c) H. Zheng, J. Zheng, B. Yu, Q. Chen, X. Wang, Y. He, Z.
Yang, X. She, J. Am. Chem. Soc. 2010, 132, 1788 – 1789; d) V. V.
Pagar, A. M. Jadhav, R.-S. Liu, J. Am. Chem. Soc. 2011, 133,
20728 – 20731; e) D. Garayalde, K. Krꢇger, C. Nevado, Angew.
Chem. Int. Ed. 2011, 50, 911 – 915; Angew. Chem. 2011, 123, 941 –
945; f) R. C. Conyers, B. W. Gung, Chem. Eur. J. 2013, 19, 654 –
664; g) N. Iqbal, C. A. Sperger, A. Fiksdahl, Eur. J. Org. Chem.
2013, 907 – 914; h) C. Zhao, X. Xie, S. Duan, H. Li, R. Fang, X.
She, Angew. Chem. Int. Ed. 2014, 53, 10789 – 10793; Angew.
Chem. 2014, 126, 10965 – 10969; i) M. E. Muratore, A. Homs, C.
Obradors, A. M. Echavarren, Chem. Asian J. 2014, 9, 3066 –
3082; j) D. Shu, W. Song, X. Li, W. Tang, Angew. Chem. Int.
Ed. 2013, 52, 3237 – 3240; Angew. Chem. 2013, 125, 3319 – 3322;
k) H. Kusama, H. Sogo, K. Saito, T. Suga, N. Iwasawa, Synlett
2013, 24, 1364 – 1370; l) W. Yang, T. Wang, Y. Yu, S. Shi, T.
Zhang, A. S. K. Hashmi, Adv. Synth. Catal. 2013, 355, 1523 –
1528.
Experimental Section
General procedure: 4ꢀ M.S. (150 mg) were placed in a test tube and
was activated by heating at 2308C for 8 h under reduced pressure (ca.
0.30 mmHg). The test tube was cooled to room temperature under
reduced pressure. ReI(CO)5 (1.7 mg, 3.8 mmol, 2.5 mol%), propargyl
ether (0.15 mmol, 1.0 equiv), and siloxydiene (0.15 mmol, 1.0 equiv)
were dissolved in 1,4-dioxane (1.5 mL) under argon atmosphere and
the resulting mixture was transferred to the test tube. The test tube
was closed and the mixture was stirred at 1008C for 4 h. The reaction
was quenched by addition of TMEDA (0.2 mL). After filtration to
remove the 4ꢀ M.S., the filtrate was concentrated under reduced
pressure in vacuo. The crude product was purified by preparative
TLC to give the [4+3] addition product.
Acknowledgements
This research was supported by a Grant-in-Aid for Scientific
Research on Innovative Areas “Precisely Designed Catalysts
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[5] For recent reviews on hydride transfer in organic synthesis, see:
a) B. Peng, N. Maulide, Chem. Eur. J. 2013, 19, 13274 – 13287;
b) M. C. Haibach, D. Seidel, Angew. Chem. Int. Ed. 2014, 53,
5010 – 5036; Angew. Chem. 2014, 126, 5110 – 5137; c) L. Wang, J.
Xiao, Adv. Synth. Catal. 2014, 356, 1137 – 1171.
[6] Gagosz et al. reported gold-catalyzed 1,5-hydride transfer of
propargyl ethers to give allenes: B. Bolte, Y. Odabachian, F.
Gagosz, J. Am. Chem. Soc. 2010, 132, 7294 – 7296.
[7] For representative examples of reactions utilizing hydride
transfer onto p-alkyne complexes of other substrates, see:
a) D. Shikanai, H. Murase, T. Hata, H. Urabe, J. Am. Chem.
Soc. 2009, 131, 3166 – 3167; b) I. D. Jurberg, Y. Odabachian, F.
Gagosz, J. Am. Chem. Soc. 2010, 132, 3543 – 3552; c) J. Kuang, S.
Ma, J. Am. Chem. Soc. 2010, 132, 1786 – 1787; d) S. Bhunia, S.
Ghorpade, D. B. Huple, R.-S. Liu, Angew. Chem. Int. Ed. 2012,
51, 2939 – 2942; Angew. Chem. 2012, 124, 2993 – 2996; e) T.
Sugiishi, H. Nakamura, J. Am. Chem. Soc. 2012, 134, 2504 – 2507;
f) X. Wu, S.-S. Chen, Y. Hu, L.-Z. Gong, Org. Lett. 2014, 16,
3820 – 3823, and references therein.
Angew. Chem. Int. Ed. 2012, 51, 723 – 727; Angew. Chem. 2012,
124, 747 – 751.
[13] For preparation of dienes from propargyl ethers utilizing metal-
catalyzed hydride transfer, see: K.-L. Yeh, B. Liu, C.-Y. Lo, H.-L.
Huang, R.-S. Liu, J. Am. Chem. Soc. 2002, 124, 6510 – 6511.
[14] Cycloheptadiene 3a easily isomerized to isomer 4a by acid
catalysis.
[15] Activation of 4ꢀ M.S. was carried out by heating at 2308C for
8 h under reduced pressure (ca. 0.30 mmHgÀ1).
[16] Methylene cyclohexane derivative 7g was produced via formal
[4+2] cycloaddition reaction of unsaturated carbene complex
intermediate with siloxydiene. For a similar reaction, see: W. D.
Wulff, W. E. Bauta, R. W. Kaesler, P. J. Lankford, R. A. Miller,
C. K. Murray, D. C. Yang, J. Am. Chem. Soc. 1990, 112, 3642 –
3659.
[8] For examples of reactions utilizing alkoxy migration of propargyl
ethers, see: a) E. Jimꢃnez-NfflÇez, M. Raducan, T. Lauterbach,
K. Molawi, C. R. Solorio, A. M. Echavarren, Angew. Chem. Int.
Ed. 2009, 48, 6152 – 6155; Angew. Chem. 2009, 121, 6268 – 6271;
b) J. Carreras, M. Livendahl, P. R. McGonigal, A. M. Echavar-
ren, Angew. Chem. Int. Ed. 2014, 53, 4896 – 4899; Angew. Chem.
2014, 126, 4996 – 4999.
[9] For a rare example of 1,4-hydride transfer onto electrophilically
activated alkynes, see: S. Yang, Z. Li, X. Jian, C. He, Angew.
Chem. Int. Ed. 2009, 48, 3999 – 4001; Angew. Chem. 2009, 121,
4059 – 4061.
[10] For reviews of vinylidene complexes, see: a) M. I. Bruce, Chem.
Rev. 1991, 91, 197 – 257; b) C. Bruneau, P. H. Dixneuf, Acc.
Chem. Res. 1999, 32, 311 – 323; c) “Preparation and stoichio-
metric reactivity of mononuclear metal vinylidene complexes”:
M. I. Bruce in Metal Vinylidenes and Allenylidenes in Catalysis
(Eds.: C. Bruneau, P.-H. Dixneuf), Wiley-VCH, Weinheim,
2008; d) B. M. Trost, A. McClory, Chem. Asian J. 2008, 3, 164 –
194; e) J. M. Lynam, Chem. Eur. J. 2010, 16, 8238 – 8247.
[11] To our knowledge, there is no report on catalytic reactions
incorporating this 1,5-hydride transfer of vinylidene intermedi-
ates derived from propargyl ethers. a) J. Ipaktschi, J. Mohsseni-
Ala, A. Dꢇlmer, C. Loschen, G. Frenking, Organometallics 2005,
24, 977 – 989; b) R. Castarlenas, M. Eckert, P. H. Dixneuf,
Angew. Chem. Int. Ed. 2005, 44, 2576 – 2579; Angew. Chem.
2005, 117, 2632 – 2635; c) T. BolaÇo, R. Castarlenas, M. A.
Esteruelas, E. OÇate, J. Am. Chem. Soc. 2007, 129, 8850 – 8859;
d) C.-P. Chung, C.-C. Chen, Y.-C. Lin, Y.-H. Liu, Y. Wang, J. Am.
Chem. Soc. 2009, 131, 18366 – 18375; e) I. Hyder, M. Jimꢃnez-
Tenorio, M. C. Puerta, P. Valerga, Organometallics 2011, 30,
726 – 737.
[17] For recent examples of rhenium vinylidene complexes, see: a) Y.
Kuninobu, K. Takai, Chem. Rev. 2011, 111, 1938 – 1953; b) D. R.
Senn, A. Wong, A. T. Patton, M. Marsi, C. E. Strouse, J. A.
Gladysz, J. Am. Chem. Soc. 1988, 110, 6096 – 6109; c) C. Kelley,
L. A. Mercando, M. R. Terry, N. Lugan, G. L. Geoffroy, Z. Xu,
A. L. Rheingold, Angew. Chem. Int. Ed. Engl. 1992, 31, 1053 –
1055; Angew. Chem. 1992, 104, 1066 – 1068; d) C. Bianchini, N.
Mantovani, A. Marchi, L. Marvelli, D. Masi, M. Peruzzini, R.
Rossi, A. Romerosa, Organometallics 1999, 18, 4501 – 4508;
e) D. A. Valyaev, O. V. Semeikin, M. G. Peterleitner, Y. A.
Borisov, V. N. Khrustalev, A. M. Mazhuga, E. V. Kremer, N. A.
Ustynyuk, J. Organomet. Chem. 2004, 689, 3837 – 3846; f) J.
Garcꢄa-ꢆlvarez, J. Dꢄez, J. Gimeno, C. M. Seifried, C. Vidal,
Inorg. Chem. 2013, 52, 5428 – 5437; g) D. Xia, Y. Wang, Z. Du,
Q.-Y. Zheng, C. Wang, Org. Lett. 2012, 14, 588 – 591; h) S. Hori,
M. Murai, K. Takai, J. Am. Chem. Soc. 2015, 137, 1452 – 1457.
[18] Generation of rhenium vinylidene complexes by the reaction of
alkynylrhenium species with imines, followed by hydride trans-
fer to give allylamine derivatives, was reported: Y. Fukumoto,
M. Daijo, N. Chatani, J. Am. Chem. Soc. 2012, 134, 8762 – 8765.
[19] For review of divinylcyclopropane rearrangement, see: a) P.
Tang, Y. Qin, Synthesis 2012, 44, 2969 – 2984; b) S. Krꢇger, T.
Gaich, Beilstein J. Org. Chem. 2014, 10, 163 – 193; c) A. C. Jones,
J. A. May, R. Sarpong, B. M. Stoltz, Angew. Chem. Int. Ed. 2014,
53, 2556 – 2591; Angew. Chem. 2014, 126, 2590 – 2628; divinylcy-
clopropane rearrangement could proceed with analogous trans
divinylcyclopropane by heating at 908C; see: d) W. D. Wulff,
D. C. Yang, C. K. Murray, J. Am. Chem. Soc. 1988, 110, 2653 –
2655.
[12] For representative examples of reactions utilizing hydride
transfer onto vinylidene complexes derived from other sub-
strates, see: a) G. B. Bajracharya, N. K. Pahadi, I. D. Gridnev, Y.
Yamamoto, J. Org. Chem. 2006, 71, 6204 – 6210; b) A. Odedra, S.
Datta, R.-S. Liu, J. Org. Chem. 2007, 72, 3289 – 3292; c) M.
Tobisu, H. Nakai, N. Chatani, J. Org. Chem. 2009, 74, 5471 –
5475; for an example of hydride transfer onto carbene com-
plexes, see: d) F. Cambeiro, S. Lꢂpez, J. A. Varela, C. Saꢅ,
Received: May 5, 2016
Published online: && &&, &&&&
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Cycloaddition Reactions
H. Sogo, N. Iwasawa*
&&&& — &&&&
Rhenium(I)-Catalyzed Generation of a,b-
Unsaturated Carbene Complex
Intermediates from Propargyl Ethers for
the Preparation of Cycloheptadiene
Derivatives
The rhenium(I)-catalyzed generation of
a,b-unsaturated carbene complex inter-
mediates from easily available propargyl
ethers was achieved for the concise
construction of cycloheptadiene deriva-
tives through the formal [4+3] cycload-
dition reaction with siloxydienes.
Angew. Chem. Int. Ed. 2016, 55, 1 – 5
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
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