Rh(III)-catalyzed C-H activation with allenes to synthesize conjugated olefins

Article abstract of DOI:10.1021/ol403407q

RhIII-catalyzed C-H activation with allenes produces highly unsaturated conjugated olefins. The reaction is applicable to both olefin and arene C(sp2)-H and is compatible with a variety of functional groups. The products can be further transformed into ot

Full text of DOI:10.1021/ol403407q

Letter
pubs.acs.org/OrgLett
Rh(III)-Catalyzed C−H Activation with Allenes To Synthesize
Conjugated Olefins
Tian-Jun Gong, Wei Su, Zhao-Jing Liu, Wan-Min Cheng, Bin Xiao, and Yao Fu*
Department of Chemistry, Joint Laboratory of Green Synthetic Chemistry, University of Science and Technology of China, Hefei
230026, China
S
* Supporting Information
ABSTRACT: RhIII-catalyzed C−H activation with allenes
produces highly unsaturated conjugated olefins. The reaction
is applicable to both olefin and arene C(sp2)−H and is
compatible with a variety of functional groups. The products
can be further transformed into other important skeletons
through Diels−Alder reaction and intramolecular transester-
ification.
llenes are highly valuable synthetic precursors in
preparative organic chemistry. Development of new
reactions by using allenes has been intensively studied in
synthetic organic chemistry.1 Among them, several examples of
transition metal catalyzed C−H with allenes were reported
(Scheme 1),2,3 for directed C−H activation has advantages over
pounds,14 etc.15 were reported. The applications of allenes in
RhIII-catalyzed C−H activation have been reported recently.
Despite these impressive advances, the development of new
types of reactions between C−H and allenes is still highly
desirable.6
A
At the outset of this project, we initially examined the
Rh(III)-catalyzed coupling reaction of phenyl dimethylcarba-
mate with ethyl 4-methylpenta-2,3-dienoate (2a) under the
conditions previously reported for C−H activation oxidative
Heck reaction ([RhCp*Cl2]2/AgSbF6/Cu(OAc)2/THP/110
°C). However, no desired product was observed (without
shown in Table 1). To our delight, the application of 1a as the
substrate resulted in the formation of conjugated olefins 3a in
65% yield. We believed that lowering the reaction temperature
would cause a better yield of the reaction. Next, after reducing
the reaction temperature, an 83% yield of the desired product
was obtained under 80 °C, a much higher yield obtained at 60
°C (86%, entry 3). Under 40 °C, the yield was slightly lower. A
survey of solvents showed that THF, toluene, t-amyl-OH, and
dioxane could also give considerable yields (entries 5−8).
Compared to Cu(OAc)2, Ag2CO3 was also an excellent
oxidation agent for this reaction (75%, entry 9). Comparative
tests showed that [RuCl2(p-cymene)]2 and Pd(OAc)2 were not
effective catalysts for this reaction (entries 10, 11). In the
absence of [RhCp*Cl2]2 the reaction did not take place (entry
12).
Scheme 1. C−H Functionalized with Allenes
traditional protocols based on substrate preactivation.4 In 2009,
the Krische group reported an Ir-catalyzed benzamide directed
C−H with allenes for synthesis of allylarenes.2a In 2010, the
Cramer group reported imine directed C−H tandem
cyclization with allenes. Almost at the same time,2b Kuninobu
and Takai showed that Re could also be utilized in a similar
reaction procedure.2c Recently, Glorius’s,3a Ma’s,3b,d and
Cramer’s3c group reported RhIII-catalyzed C−H activation
with allenes for the synthesis of allylarenes and heteroaromatic
compounds. Despite these impressive advances, little has been
shown to produce an oxidative Heck-type product (conjugated
diene) by using simple C−H and allenes.6 Herein we report an
example of RhIII-catalyzed C−H activation with allenes to
produce highly unsaturated conjugated olefins, while con-
jugated olefins were a very useful building block to the
constrained cyclic skeleton.5,6
With these optimal conditions in hand, different enolate
derivatives were investigated (Table 2). Both electron-with-
drawing and -donating enolate substrates were tested, and all of
them exhibited good reactivities, such as 4-OMe, 3-CF3, and 4-
OBn. Various halogen substituents showed good compatibility,
which made additional functionalization possible at these
positions (3e−3h). A naphthyl-substituted enolate derivative
smoothly survived the process (3i), which was confirmed by X-
RhIII-catalyzed processes proved to be an efficient strategy in
C−H functionalization reactions.7 Examples such as alkenes,8
alkynes,9 imines,10 arenes,11 an electrophilic amination
reagent,12 an electrophilic halogen reagent,13 diazo com-
Received: September 23, 2013
Published: January 3, 2014
© 2014 American Chemical Society
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dx.doi.org/10.1021/ol403407q | Org. Lett. 2014, 16, 330−333

Organic Letters
Letter
a
Table 1. Optimization of the Reaction Conditions
Scheme 2. Crystal Structure of the Product 3i
entry
[O]
solvent
THP
T (°C)
yield (%)
1
2
3
4
5
6
7
8
9
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
Ag2CO3
110
80
60
40
60
60
60
60
60
60
60
60
65
83
86
75
81
36
77
72
75
<5
<2
0
THP
THP
THP
THF
toluene
t-AmylOH
dioxane
THP
Other substituted allenes were also examined. Moderate
yields were obtained for electron-withdrawing allenes (3q−3s).
Intriguingly, when 1,1-dimethylallene was treated with 1a under
a lower temperature (40 °C) by use of Ag2CO3 as an oxidant,
the corresponding product 3t was obtained in 54% yield.
Unfortunately, monosubstituted allenes exhibited poor reac-
tivities in this reaction.
It was interesting to find that, when 1a was reacted with tera-
substituted allene 2b, highly regioselective C−H elimination of
the allene was observed. Only 37% of 3u was observed, but
without product 3u′ (Scheme 3).
b
10
Cu(OAc)2
Cu(OAc)2
Cu(OAc)2
THP
c
11
THP
d
12
THP
a
Conditions: 1a (0.2 mmol), 2a (2 equiv), [RhCp*Cl2]2 (2.5 mol %),
AgSbF6 (10 mol %), Oxidant (2 equiv), solvent (0.5 mL), 24 h, under
Ar, isolated yields (average of two runs). [RuCl2(p-cymene)]2 instead
of [RhCp*Cl2]2. Pd(OAc)2 instead of [RhCp*Cl2]2. Without use
[RhCp*Cl2]2. THP = Tetrahydropyran.
b
c
d
a b
,
Table 2. The Scope of Substrates
Scheme 3. Regioselectivity C−H Elimination of Allene (R =
CONMe2)
To further explore the scope of the process, arenes’ C−H
bonds were tested. We were delighted to find that both
aromatic and heteroaromatic substrates could be successfully
transformed when an amide and ketone were used as directing
groups under 120 °C (Table 3). The amide could be converted
in a moderate yield (4a). Aromatic and heteroaromatic ketones
exhibited good compatibility (4b−e).
a
Table 3. C−H Functionalization of Arenes
a
Conditions: 1 (0.2 mmol), 2 (2 equiv), [RhCp*Cl2]2 (2.5 mol %),
AgSbF6 (10 mol %), Cu(OAc)2 (2 equiv), THP, 60 °C, 24 h, Ar.
b
c
Isolated yields. 2 equiv Ag2CO3 instead of Cu(OAc)2, under 40 °C
for 12h. R = CON(Me)2.
a
Conditions: 1 (0.2 mmol), 2 (2 equiv), [RhCp*Cl2]2 (2.5 mol %),
AgSbF6 (10 mol %), Cu(OAc)2 (2 equiv), dioxane, 120 °C, 24 h, Ar.
ray analysis of the product (Scheme 2).16 The very good
compatibility of a heterocyclic ring structure, such as furan and
thiophene (3j, 3k), was achieved. It was noteworthy that an
allylic ether substituted enolate was compatible with this
reaction (3n, 3o), while previous reports showed that allyl ether
can react with arene C−H bonds under the Rh(III)-catalyst. A
cyclic enol ester could also be transformed but with a much
lower yield (3p, 34%).
In a scaled-up experiment (3 mmol scale, Scheme 4), we
found that the yield of 3a remained satisfactory (83%). A larger
scale reaction (5 mmol scale) was performed, and a 78% yield
of 3a was obtained. Thus the reaction was synthetically useful
because conjugated olefins could be readily converted to
diverse cyclic skeletons. A 2H-pyran-2-one derivative (5) could
be obtained when 3a was treated with BF3·OEt2 under refluxing
331
dx.doi.org/10.1021/ol403407q | Org. Lett. 2014, 16, 330−333

Organic Letters
Letter
Scheme 4. Intramolecular Transesterification
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: fuyao@ustc.edu.cn.
Notes
The authors declare no competing financial interest.
1,4-dioxane (Scheme 4). Furthermore, we were convinced that
the reaction of 3t with dienophiles would be useful for the
synthesis of six-membered carbocycles17 (Scheme 5). First, 3t
ACKNOWLEDGMENTS
■
We thank NSFC (21325208, 21172209, 21361140372), CAS
(KJCX2-EW-J02), FRFCU (WK2060190025), SRFDP
(20123402110051), CPSF (2011M500289, 2012T50078) and
Fok Ying Tung Education Foundation.
Scheme 5. Diels−Alder Reaction with 3t
REFERENCES
■
(1) For reviews on the reactions of allenes, see: (a) Ma, S. Chem. Rev.
2005, 105, 2829. (b) Ma, S. Acc. Chem. Res. 2009, 42, 1679.
(c) Krause, N.; Winter, C. Chem. Rev. 2011, 111, 1994. (d) Hoffmann-
Roder, A.; Krause, N. Angew. Chem., Int. Ed. 2002, 41, 2933.
̈
(e) Modern Allene Chemistry; Krause, N., Hashmi, A. S. K., Eds.; Wiley-
VCH: Weinheim, 2004.
(2) For some recent examples on C−H functionalization involving
allenes, see: (a) Zhang, Y. J.; Skucas, E.; Krische, M. J. Org. Lett. 2009,
12, 4248. (b) Tran, D. N.; Cramer, N. Angew. Chem., Int. Ed. 2010, 49,
8181. (c) Kuninobu, Y.; Yu, P.; Takai, K. Org. Lett. 2010, 12, 4274.
(3) For RhIII-catalyzed C−H functionalization with allenes, see:
(a) Wang, H.; Glorius, F. Angew. Chem., Int. Ed. 2012, 51, 7318.
(b) Zeng, R.; Fu, C.; Ma, S. J. Am. Chem. Soc. 2012, 134, 9597. (c) Ye,
B.; Cramer, N. J. Am. Chem. Soc. 2013, 135, 636. (d) Zeng, R.; Ye, J.;
Fu, C.; Ma, S. Adv. Synth. Catal. 2013, 355, 1963.
was treated with 2 equiv of N-methylmaleimide to afford 6 in
81% yield. Along the same line, the use of diethyl
acetylenedicarboxylate provided the product 7 in 77% yield.
We propose that the mechanism of the reaction is as follows
(Scheme 6): First, the Rh(III) catalyst reacted with the
(4) For reviews: (a) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu,
J.-Q. Chem. Soc. Rev. 2009, 38, 3242. (b) Colby, D. A.; Bergman, R. G.;
Ellman, J. A. Chem. Rev. 2010, 110, 624. (c) Lyons, T. W.; Sanford, M.
S. Chem. Rev. 2010, 110, 1147. (d) Yeung, C. S.; Dong, V. M. Chem.
Rev. 2011, 111, 1215. (e) Sun, C.-L.; Li, B.-J.; Shi, Z.-J. Chem. Rev.
2011, 111, 1293. (f) Ackermann, L. Chem. Rev. 2011, 111, 1315.
(g) McMurray, L.; O’Hara, F.; Gaunt, M. J. Chem. Soc. Rev. 2011, 40,
Scheme 6. Proposed Mechanistic Pathway
1885. (h) Wencel-Delord, J.; Droge, T.; Liu, F.; Glorius, F. Chem. Soc.
̈
Rev. 2011, 40, 4740. (i) Cho, S. H.; Kim, J. Y.; Kwak, J.; Chang, S.
Chem. Soc. Rev. 2011, 40, 5068. (j) Engle, K. M.; Mei, T.-S.; Wasa, M.;
Yu, J.-Q. Acc. Chem. Res. 2012, 45, 788. (k) Shi, Z.-Z.; Zhang, C.; Tang,
C.-H.; Jiao, N. Chem. Soc. Rev. 2012, 41, 3381.
(5) (a) Back, T. G.; Clary, K. N.; Gao, D. Chem. Rev. 2010, 110,
4498. (b) Trost, B. M.; Pinkerton, A. B.; Seidel, M. J. Am. Chem. Soc.
2001, 123, 12466.
(6) During the submission of this manuscript, Glorius et al. reported
[3]Dendralene Synthesis: Rhodium(III)-Catalyzed Alkenyl C−H
Activation and Coupling Reaction with Allenyl Carbinol Carbonate.
see: Wang, H.; Beiring, B.; Yu, D.-G.; Collins, K. D.; Glorius, F. Angew.
Chem., Int. Ed. 2013, 52, 12430.
substrate through a C−H activation step to generate an
intermediate (I). Second, Rh(III) in I was coordinated with
allene followed by insertion of the moiety into the C−Rh(III)
bond to produce complex II or II′. Finally, β-H elimination
occurred to generate the target product. The Rh(III) complex
then went back into the catalytic cycle.
(7) For reviews, see: (a) Satoh, T.; Miura, M. Chem.Eur. J. 2010,
16, 11212. (b) Colby, D. A.; Tsai, A. S.; Bergman, R. G.; Ellman, J. A.
Acc. Chem. Res. 2012, 45, 814. (c) Patureau, F. W.; Wencel-Delord, J.;
Glorius, F. Aldrichimica Acta 2012, 45, 31. (d) Song, G.; Wang, F.; Li,
X. Chem. Soc. Rev. 2012, 41, 3651. (e) Zhu, C.; Wang, R.; Falck, J. R.
Chem.Asian J. 2012, 7, 1502.
In conclusion, an example of Rh(III) catalyzed C−H
activation with allenes to produce highly unsaturated
conjuncted olefins was reported. This reaction features high
regioselectivity, mild reaction conditions, and excellent func-
tional group tolerance. Furthermore, we had demonstrated that
the unsaturated conjugated olefins could be transformed into
other important skeletons through Diels−Alder reaction and
intramolecular transesterification. This transformation provided
a new method to synthesize conjunction olefins. Further
exploration of the synthetic utilities of this chemistry and in-
depth mechanistic study are currently in progress.
(8) For selected recent examples of RhIII-catalyzed C−H
founctionalization with alkenes, see: (a) Ueura, K.; Satoh, T.; Miura,
M. Org. Lett. 2007, 9, 1407. (b) Umeda, N.; Hirano, K.; Satoh, T.;
Miura, M. J. Org. Chem. 2009, 74, 7094. (c) Patureau, F. W.; Glorius,
F. J. Am. Chem. Soc. 2010, 132, 9982. (d) Gong, T.-J.; Xiao, B.; Liu, Z.-
J.; Wan, J.; Xu, J.; Luo, D.-F.; Fu, Y.; Liu, L. Org. Lett. 2011, 13, 3235.
(e) Park, S. H.; Kim, J. Y.; Chang, S. Org. Lett. 2011, 13, 2372.
(f) Feng, C.; Loh, T.-P. Chem. Commun. 2011, 47, 10458. (g) Patureau,
F. W.; Besset, T.; Glorius, F. Angew. Chem., Int. Ed. 2011, 50, 1064.
(h) Rakshit, S.; Grohmann, C.; Besset, T.; Glorius, F. J. Am. Chem. Soc.
2011, 133, 2350. (i) Li, H.; Li, Y.; Zhang, X.-S.; Chen, K.; Wang, X.;
Shi, Z.-J. J. Am. Chem. Soc. 2011, 133, 15244. (j) Ackermann, L.; Wang,
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental details. This material is available free of charge via
the Internet at http://pubs.acs.org.
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L.; Wolfram, R.; Lygin, A. V. Org. Lett. 2012, 14, 728. (k) Graczyk, K.;
Ma, W.; Ackermann, L. Org. Lett. 2012, 14, 4110. (l) Li, G.; Ding, Z.;
Xu, B. Org. Lett. 2012, 14, 5338. (m) Wang, C.; Chen, H.; Wang, Z.;
Chen, J.; Huang, Y. Angew. Chem., Int. Ed. 2012, 51, 7242. (n) Liu, B.;
Fan, Y.; Gao, Y.; Sun, C.; Xu, C.; Zhu, J. J. Am. Chem. Soc. 2013, 135,
Chem., Int. Ed. 2013, 52, 2577. (d) Qi, Z.; Li, X. Angew. Chem., Int. Ed.
2013, 52, 8995. (e) Gong, T.-J.; Xiao, B.; Cheng, W.-M.; Su, W.; Xu,
J.; Liu, Z.-J.; Liu, L.; Fu, Y. J. Am. Chem. Soc. 2013, 135, 10630.
(16) The structure of product 3i was (2E,4Z)-ethyl 5-(dimethyl-
carbamoyloxy)-5-(naphthalen-1-yl)-3-(prop-1-en-2-yl)penta-2,4-dien-
oate.
468. (o) Hyster, T. K.; Knorr, L.; Ward, T. R.; Rovis, T. Science 2012,
̈
(17) Grieco, P. A.; Nunes, J. J.; Gaul, M. D. J. Am. Chem. Soc. 1990,
112, 4595.
338, 500. (p) Ye, B.; Cramer, N. Science 2012, 338, 504. (q) Wencel-
Delord, J.; Nimphius, C.; Patureau, F. W.; Glorius, F. Angew. Chem.,
Int. Ed. 2012, 51, 2247. (r) Wang, C.; Chen, H.; Wang, Z.; Chen, J.;
Huang, Y. Angew. Chem., Int. Ed. 2012, 51, 7242. (s) Zhen, W.; Wang,
F.; Zhao, M.; Du, Z.; Li, X. Angew. Chem., Int. Ed. 2012, 51, 11819.
(t) Wencel-Delord, J.; Nimphius, C.; Wang, H.; Glorius, F. Angew.
Chem., Int. Ed. 2012, 51, 13001. (u) Wang, H.; Schroder, N.; Glorius,
̈
F. Angew. Chem., Int. Ed. 2013, 52, 5386. (v) Shi, Z.; Grohmann, C.;
Glorius, F. Angew. Chem., Int. Ed. 2013, 52, 5393. (w) Neely, J. M.;
Rovis, T. J. Am. Chem. Soc. 2013, 135, 66.
(9) For selected recent examples of RhIII-catalyzed C−H
functionalization with alkynes, see: (a) Stuart, D. R.; Alsabeh, P.;
Kuhn, M.; Fagnou, K. J. Am. Chem. Soc. 2010, 132, 18326.
(b) Guimond, N.; Gorelsky, S. I.; Fagnou, K. J. Am. Chem. Soc.
2011, 133, 6449. (c) Xu, X.; Liu, Y.; Park, C.-M. Angew. Chem., Int. Ed.
2012, 51, 9372. (d) Wang, H.; Grohmann, C.; Nimphius, C.; Glorius,
F. J. Am. Chem. Soc. 2012, 134, 19592. (e) J ayakumar, J .;
Parthasarathy, K.; Cheng, C.-H. Angew. Chem., Int. Ed. 2012, 51, 197.
(f) Wang, D.; Wang, F.; Song, G.; Li, X. Angew. Chem., Int. Ed. 2012,
51, 12348. (g) Shi, Z.; Grohmann, C.; Glorius, F. Angew. Chem., Int.
Ed. 2013, 52, 5393. (h) Zhao, D.; Shi, Z.; Glorius, F. Angew. Chem., Int.
Ed. 2013, 52, 12426.
(10) For selected recent examples of RhIII-catalyzed C−H
functionalization with CO, imines, and aldehydes, see: (a) Hesp, K.
D.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc. 2011, 133, 11430.
(b) Li, Y.; Li, B.-J.; Wang, W.-H.; Huang, W.-P.; Zhang, X.-S.; Chen,
K.; Shi, Z.-J. Angew. Chem., Int. Ed. 2011, 50, 2115. (c) Tauchert, M.
E.; Incarvito, C. D.; Rheingold, A. L.; Bergman, R. G.; Ellman, J. A. J.
Am. Chem. Soc. 2012, 134, 1482. (d) Lian, Y.; Huber, T.; Hesp, K. D.;
Bergman, R. G.; Ellman, J. A. Angew. Chem., Int. Ed. 2013, 52, 629.
(11) For selected recent examples of RhIII-catalyzed C−H arylation,
see: (a) Morimoto, K.; Itoh, M.; Hirano, K.; Satoh, T.; Shibata, Y.;
Tanaka, K.; Miura, M. Angew. Chem., Int. Ed. 2012, 51, 5359. (b) Kuhl,
N.; Hopkinson, M. N.; Glorius, F. Angew. Chem., Int. Ed. 2012, 51,
8230. (c) Dong, J.; Long, Z.; Song, F.; Wu, N.; Guo, Q.; Lan, J.; You, J.
Angew. Chem., Int. Ed. 2013, 52, 580.
(12) For selected recent examples of a RhIII-catalyzed C−H
functionalization with an electrophilic amination reagent, see:
(a) Kim, J. Y.; Park, S. H.; Ryu, J.; Cho, S. H.; Kim, S. H.; Chang,
S. J. Am. Chem. Soc. 2012, 134, 9110. (b) Ryu, J.; Shin, K.; Park, S. H.;
Kim, J. Y.; Chang, S. Angew. Chem., Int. Ed. 2012, 51, 9904. (c) Shin,
K.; Baek, Y.; Chang, S. Angew. Chem., Int. Ed. 2013, 52, 8031. (d) Yu,
D.-G.; Suri, M.; Glorius, F. J. Am. Chem. Soc. 2013, 135, 8802. (e) Lian,
Y.; Hummel, J. R.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc.
2013, 135, 12548. (f) Ng, K.-H.; Zhou, Z.; Yu, W.-Y. Chem. Commun.
2013, 49, 7031. (g) Ng, K.-H.; Zhou, Z.; Yu, W.-Y. Org. Lett. 2012, 14,
272. (h) Grohmann, C.; Wang, H.; Glorius, F. Org. Lett. 2012, 14, 656.
(i) Yu, S.; Wan, B.; Li, X. Org. Lett. 2013, 15, 3706.
(13) For selected recent examples of RhIII-catalyzed C-H
bromination and iodination, see: (a) Schroder, N.; Wencel-Delord,
̈
J.; Glorius, F. J. Am. Chem. Soc. 2012, 134, 8298. (b) Kuhl, N.;
Schroder, N.; Glorius, F. Org. Lett. 2013, 15, 3860.
̈
(14) For selected recent examples of RhIII-catalyzed C−H
functionalization with diazo compounds, see: (a) Chan, W.-W.; Lo,
S.-F.; Zhou, Z.; Yu, W.-Y. J. Am. Chem. Soc. 2012, 134, 13565.
(b) Hyster, T. K.; Ruhl, K. E.; Rovis, T. J. Am. Chem. Soc. 2013, 135,
5364. (c) Shi, Z.; Koester, D. C.; Boultadakis-Arapinis, M.; Glorius, F.
J. Am. Chem. Soc. 2013, 135, 12204. (d) Yu, X.; Yu, S.; Xiao, J.; Wan,
B.; Li, X. J. Org. Chem. 2013, 78, 5444. (e) Cui, S.; Zhang, Y.; Wang,
D.; Wu, Q. Chem. Sci. 2013, 4, 3912.
(15) (a) Hesp, K. D.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc.
2011, 133, 11430. (b) Zhou, B.; Hou, W.; Yang, Y.; Li, Y. Chem.Eur.
J. 2013, 19, 4701. (c) Li, X.; Yu, S.; Wang, F.; Wan, B.; Yu, X. Angew.
333
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