Copper-mediated aryloxylation and vinyloxylation of β-C(sp3)-H bond of propionamides with organosilanes

Article abstract of DOI:10.1021/acs.orglett.5b01192

A novel copper-mediated method for the aryloxylation and vinyloxylation of β-C(sp³)-H bonds of propioamides with organosilanes is described. The reaction proceeds with the assistance of an 8-aminoquinolyl auxiliary in a tandem way by the first oxidation of β-C(sp³)-H bonds and subsequent arylation/vinylation to give the aryloxylation/vinyloxylation products. This unusual aryloxy/vinyloxy forming reaction offers a new avenue for the functionalization of unactivated sp³ C-H bonds in organic synthesis.

Full text of DOI:10.1021/acs.orglett.5b01192

Letter
pubs.acs.org/OrgLett
3
Copper-Mediated Aryloxylation and Vinyloxylation of β‑C(sp )−H
Bond of Propionamides with Organosilanes
Jitan Zhang, Hui Chen, Binjie Wang, Zhanxiang Liu, and Yuhong Zhang*
†
†
†
†
,†,‡
†ZJU-NHU United R&D Center, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
‡State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
*
S Supporting Information
3
ABSTRACT: A novel copper-mediated method for the aryloxylation and vinyloxylation of β-C(sp )−H bonds of propioamides
with organosilanes is described. The reaction proceeds with the assistance of an 8-aminoquinolyl auxiliary in a tandem way by the
3
first oxidation of β-C(sp )−H bonds and subsequent arylation/vinylation to give the aryloxylation/vinyloxylation products. This
3
unusual aryloxy/vinyloxy forming reaction offers a new avenue for the functionalization of unactivated sp C−H bonds in organic
synthesis.
he metal-mediated functionalization of C−H bonds has
arylation via C−H activation with the assistance of an identical
T
exerted a huge impact on the bond-disconnection
directing group (Scheme 1). In this approach, the initial metal
strategies for complex molecules through a direct and step-
1
economical manner. Over the past decades, significant
Scheme 1. Strategy of Multistep Reaction Using Identical
Directing Group
progress has been attained for the chelation-assisted direct
functionalization of C−H bonds of arenes, olefins, and
2
−5
alkanes.
A common requirement for these transformations
is the activation of the C−H bond by the formation of five- or
six-membered metallacycles, which facilitates the subsequent
diverse couplings. While a large number of transformations can
be achieved with various coupling partners, the catalyst and
directing group serve a single reaction in most cases. The
sequential multistep reaction via C−H activation by exploiting
an identical directing group would be valuable, expanding the
range of C−H functionalities.
3
mediated oxidation of the sp C−H bond followed by the
arylation in a position-selective mode generates the expected
aryl-alkyl ether derivatives in a tandem way. The challenges for
successful implementation of this strategy include (1) the
requirement of a metal center that is not only reactive for the
3
3
oxidation of unactivated sp C−H bonds but also effective for
The development of site-selective activation of sp C−H
the following arylation; (2) the achievement of reactivity
through both the five-membered metallacycles and relatively
remote coordination; (3) the definite sequence of first
oxidation and subsequent arylation. Recently, a number of
elegant chelation-directing strategies have been successfully
bonds constitutes important transformations in synthetic
chemistry which allows the conversion of the least expensive
6
alkanes to valuable products. However, compared with the
2
functionalization of C(sp )−H bonds, the development of
3
catalytic methods for activating sp C−H bonds is still in its
3
11,12
7
developed for the oxidation of inactive C(sp )−H bonds.
Herein, we disclose a novel method for the synthesis of β-
aryloxylated propionic amides through the copper-mediated
aryloxylation of unactivated sp C−H bonds at the β-position of
propionic amides with a range of organosilanes. Unprecedent-
edly, the two different intermolecular couplings execute serially
through the promotion of copper at different steps with the
assistance of an 8-aminoquinolyl auxiliary.
At the outset of our study, we focused our investigation by
employing propionamide 1a as a model substrate, which
early stage. Few methods are available for selective conversion
of alkanes into more valuable products due to the inertness of
3
the C(sp )−H bond and the challenge of selectivity. It is highly
3
3
desirable to design a new concept based on C(sp )−H
activation for the assembly of diverse complex organic
structures. Aryl-alkyl ethers serve as useful intermediates in
organic synthesis and are found in an impressive number of
8
,9
biologically relevant molecules and natural products.
Although the Ullmann aryl-alkyl ether synthesis has been
widely used, the method requires preactivation of substrates
10
and often suffers from harsh reaction conditions. A powerful
alternative to the synthesis of aryl-alkyl ethers is the use of
metal to promote sequential transformations of oxidation and
Received: April 22, 2015
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.5b01192
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
,
a b
contains a well-behaved aminoquinoline auxiliary discovered by
Daugulis (Table 1; see the Supporting Information). We were
Scheme 2. Substrate Scope of Organosiloxanes
13
a
Table 1. Optimization of Reaction Conditions
b
entry
[Ag]
additive I
additive II
yield (%)
1
2
3
4
5
6
7
8
trace
19
Ag CO3
2
AgOAc
28
Ag O
2
47
Ag O
2
NaOPiv
NaOPiv
NaOPiv
NaOPiv
56
Ag O
2
PC
62
Ag O
2
GBL
50
Ag O
2
(BOC) O
72
2
a
Reactions conditions: 1a (0.1 mmol), 2a (0.5 mmol), Cu(OAc) (0.2
2
mmol), [Ag] (2.0 equiv), CsF (2.0 equiv), additive I (0.3 equiv),
b
additive II (6.0 equiv), DMF (1.5 mL), N , 150 °C, 0.5 h. Isolated
2
yield by flash column chromatography. PC = Propylene carbonate,
GBL = γ-Butyrolactone, (BOC) O = di-tert-Butyl dicanonate, Q =
2
Quinolin-8-yl.
a
pleased to observe the formation of a trace of desired product
Reactions conditions: 1 (0.1 mmol), 2 (0.5 mmol), Cu(OAc) (0.2
2
3
a by the treatment of propioamide 1a and arysiloxane 2a in
mmol), Ag O (2.0 equiv), CsF (2.0 equiv), NaOPiv (0.3 equiv),
2
b
(
BOC) O (6.0 equiv), DMF (1.5 mL), N , 150 °C, 0.5 h. Isolated
the presence of 2.0 equiv of Cu(OAc) at 150 °C for 0.5 h
2
2
2
yield by flash column chromatography. (BOC) O = di-tert-Butyl
(Table 1, entry 1). The reaction was significantly improved by
2
dicanonate, Q = Quinolin-8-yl.
the addition of 2.0 equiv of silver salt as the oxidant, and a
superior outcome was provided by Ag O to give a 47% yield
2
(Table 1, entries 2−4). Despite the low yield, this reaction
shown). Sterically hindered arylsilanes delivered a lower yield
even after the modification of the reaction time (Scheme 2,
3ad). 2-Naphthylsilane could participate in the reaction,
providing the aryloxylation product in 41% yield (Scheme 2,
3ag). In all cases studied, diaryloxylated products were not
observed.
revealed that two different couplings could indeed proceed in
sequence with the copper to promote different product-forming
steps under the assistance of an identical directing group. In
order to increase the yield, we surveyed carboxylate additives
that were reported to be promoters of proton abstraction by
1
4
15
Echavarren and Fagnou. It was found that a catalytic
amount (30 mol %) of sodium pivalate hydrate did accelerate
the C−H aryloxylation to give the desired 3a in 56% yield
Vinyl ethers are highly valuable organic molecules consider-
ing their numerous applications in polymer formulations,
surfactants, drug delivery systems, and general organic
16
(
Table 1, entry 5). This result implicated that a concerted
synthesis. The important utility of the vinyl ether structure
motif has prompted intense research directed at discovering
metalation−deprotonation pathway might be involved in the
C−H oxidation step. Interestingly, esters and carbonic
anhydride dramatically improved the efficiency of the reaction
17
efficient and high-yielding methods for its preparation. It
would be extremely valuable from the synthetic point of view if
vinylsilanes could perform the oxidation/vinylation sequential
transformation via direct C−H cleavage to synthesize vinyl
ethers. To our great delight, we found that trimethoxyvinylsi-
lane indeed was a good substrate for this aryloxylation reaction
and diverse vinyl ethers could be prepared from the
corresponding propionamides readily (Scheme 2, 3ah−3hh).
Next, we investigated the compatibility of the reaction with
amide derivatives as summarized in Scheme 3. Pivalamide was
an excellent substrate to give the aryloxylation product in 72%
yield (3aa). Replacement of one methyl group in the α-carbon
of pivalamide with other alkyl groups, such as ethyl, propyl and
butyl, afforded the corresponding products in good yields
(3ba−3da). The reaction showed high selectivity to give only
the monoaryloxylation product, and the diaryloxylation product
was not detected. The substrate bearing one methyl group such
as 2-ethyl-2-methyl-N-(quinolin-8-yl)pentanamide could par-
ticipate in the reaction smoothly to deliver the desired product
in good yield (3ea). It should be noted that a variety of aryl
containing carboxamides selectively gave the sole aryloxylation
(
(
Table 1, entries 6−8), and di-tert-butyl dicanonate
(BOC) O) gave the best yield (72%) (Table 1, entry 8).
2
No reaction was observed in the absence of a copper promoter.
With the optimized conditions in hand, we explored the
scope of organosiloxanes with the substrate 1 as summarized in
Scheme 2. Initially, the ability of different arysilane precursors
to participate in the reaction was probed. Several commercially
available arylsilanes, such as dimethoxydiphenylsilane,
trimethoxy(phenyl)silane, and triethoxyl(phenyl)silane, were
examined. Trimethoxy(phenyl)silane and triethoxyl(phenyl)-
silane were identified to be the superior arylation reagents that
provided the desired aryloxylation product in high efficiency,
albeit dimethoxydiphenylsilane was much less reactive (Scheme
2, 3aa). The electronic properties of aryl group in the
arylsilanes exerted a dramatic effect on the reaction. The
electron-rich arylsilanes showed very good reactivity to afford
the β-aryloxylated products in good yields (Scheme 2, 3ab−
3
af). However, the aryloxylation of electron-deficient arylsilanes
took place sluggishly to give a trace of the product (data not
B
DOI: 10.1021/acs.orglett.5b01192
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
,
ab
Scheme 3. Substrate Scope of Amides
see the Supporting Information). These results revealed that
Cu(OAc)2 served as the source of the oxygen in the
aryloxylation product.
5i−k
Based on an earlier precedent
and our own preliminary
studies above, a plausible reaction pathway was proposed as
shown in Scheme 5. Coordination of a substrate to a copper(II)
Scheme 5. Mechanistic Hypothesis
a
Reactions conditions: 1 (0.1 mmol), 2a (0.5 mmol), Cu(OAc) (0.2
2
mmol), Ag O (2.0 equiv), CsF (2.0 equiv), NaOPiv (0.3 equiv),
2
b
(
BOC) O (6.0 equiv), DMF (1.5 mL), N , 150 °C, 0.5 h. Isolated
yield by flash column chromatography. (BOC) O = di-tert-Butyl
species and the subsequent C−H activation and disproportio-
nation generate an organocopper(III) intermediate A, which
undergoes reductive elimination to generate the acetoxylated
product and form the copper(I) species B. The oxidation of B
2
2
2
dicanonate, Q = Quinolin-8-yl.
products at the methyl group without the formation of any
by Ag O produces the copper(II) species C, which reacts with
1
8
2
byproduct at the active benzyl position (3fa−3ja).
methanol liberated from organosiloxanes under the reaction
conditions to give rise to intermediate D. The disproportiona-
tion and subsequent transmetalation of intermediate E with aryl
or alkenyl silicate generate the organocopper(III) intermediate
F, which undergoes the reductive elimination and protonation
to give the final aryloxylation product.
Furthermore, the ether group, which contains the active C−
1
9
H bond adjacent to oxygen, tolerated the reaction conditions
to give the target product 3ka in 63% yield. Gratifyingly, the
five- and four-membered cyclic carboxamides showed good
reactivity to give the corresponding aryloaylation products that
are not easy to synthesize by known methods. Interestingly, the
corresponding cyclohexanecarboxamide failed to give the
aryloxylation product but underwent the intramolecular
In conclusion, a new copper-mediated aryloxylation/vinyl-
3
oxylation of the C(sp )−H bond with organosiloxane reagents
was developed through a sequential oxidation and arylation/
vinylation process with the assistance of an 8-aminoquinolyl
auxiliary. This reaction pattern allows the efficient synthesis of
aryl-alkyl ethers from readily available starting materials and
provides a new avenue for direct C−H bond functionalizations.
The preliminary studies on the reaction mechanism indicate
3
C(sp )−H bond amidation to afford the spiro compound 3na
in 61% yield.
To gain some insights into this copper-promoted novel
process in terms of generality and mechanism, we performed a
series of preliminary studies (Scheme 4). No desired product
that Cu(OAc) performs as both the promoter and the source
2
Scheme 4. Control Experiments
of oxygen. Efforts to further understand the reaction parameters
and to extend this approach to other synthesis of valuable
compounds are currently underway in our laboratory.
ASSOCIATED CONTENT
Supporting Information
■
*
S
1
Experimental details, spectral and analytical data, copies of H
and 13C NMR spectra for new compounds. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.orglett.5b01192.
AUTHOR INFORMATION
Corresponding Author
■
was observed when phenol was employed in the standard
*
E-mail: yhzhang@zju.edu.cn
conditions (Scheme 4, eq a). This result excluded the C−O
3
Notes
coupling of the C(sp )−H bond with phenol which might
18
The authors declare no competing financial interest.
generate from trimethoxy(phenyl)silane. Furthermore, the O -
1
8
labeling experiment using a mixture of Cu(O Ac) and
2
18
ACKNOWLEDGMENTS
Cu(OAc) resulted in a sharp increase in the scale of O -
■
2
labeling product 3ha′ (Scheme 4, eq b; see the Supporting
Funding from NSFC (No. 21272205, 21472165) and NBRPC
(No. 2011CB936003), the Program for Zhejiang Leading Team
of S&T Innovation (2011R50007) is acknowledged.
1
8
Information). In contrast, only a trace of O -labeling product
18
3
ha′ was observed in the presence of H O (Scheme 4, eq c;
2
C
DOI: 10.1021/acs.orglett.5b01192
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
(
b) Godula, K.; Sames, D. Science 2006, 312, 67. (c) Davies, H. M. L.;
REFERENCES
■
Manning, J. R. Nature 2008, 451, 417. (d) Chaumontet, M.; Piccardi,
R.; Baudoin, O. Angew. Chem., Int. Ed. 2009, 48, 179. (e) Stang, E. M.;
White, M. C. Angew. Chem., Int. Ed. 2011, 50, 2094.
(
1) For selected reviews of C−H functionalizations: (a) Giri, R.; Shi,
B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem. Soc. Rev. 2009, 38,
3
(
242. (b) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147.
c) Chen, X.; Engle, K. M.; Wang, D.-H.; Yu, J.-Q. Angew. Chem., Int.
Ed. 2009, 48, 5094. (d) McMurray, L.; O’Hara, F.; Gaunt, M. J. Chem.
Soc. Rev. 2011, 40, 1885. (e) Wencel-Delord, J.; Droge, T.; Liu, F.;
Glorius, F. Chem. Soc. Rev. 2011, 40, 4740.
2) For selected examples of C(sp )−H bonds functionalization, see:
a) Colby, D. A.; Bergman, R. G.; Ellman, J. A. Chem. Rev. 2010, 110,
24. (b) Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147.
c) Rouquet, G.; Chatani, N. Angew. Chem., Int. Ed. 2013, 52, 2.
d) Ackermann, L. Acc. Chem. Res. 2014, 47, 281. (e) Wang, D.-H.;
Engle, K. M.; Shi, B.-F.; Yu, J.-Q. Science 2010, 327, 315. (f) Xiao, B.;
Gong, T.-J.; Xu, J.; Liu, Z.-J.; Liu, L. J. Am. Chem. Soc. 2011, 133, 1466.
g) Kwak, J.; Ohk, Y.; Jung, Y.; Chang, S. J. Am. Chem. Soc. 2012, 134,
7778. (h) Li, G.; Leow, D.; Wan, L.; Yu, J.-Q. Angew. Chem., Int. Ed.
013, 52, 1245. (i) Liu, B.; Fan, Y.; Gao, Y.; Sun, C.; Xu, C.; Zhu, J. J.
Am. Chem. Soc. 2013, 135, 468. (j) He, R.; Huang, Z.-T.; Zheng, Q.-Y.;
Wang, C. Angew. Chem., Int. Ed. 2014, 53, 4950. (k) Grigorjeva, L.;
Daugulis, O. Angew. Chem., Int. Ed. 2014, 53, 10209. (l) Shang, M.;
Sun, S. Z.; Wang, H. L.; Laforteza, B. N.; Dai, H. X.; Yu, J. Q. Angew.
(7) (a) Jazzar, R.; Hitce, J.; Renaudat, A.; Sofack-Kreutzer, J.;
Baudoin, O. Chem.Eur. J. 2010, 16, 2654. (b) Li, H.; Li, B. J.; Shi, Z.
J. Catal. Sci. Technol. 2011, 1, 191.
̈
(8) (a) Wang, S.; Beck, R.; Blench, T.; Burd, A.; Buxton, S.; Malic,
M.; Ayele, T.; Shaikh, S.; Chahwala, S.; Chander, C.; Holland, R.;
Merette, S.; Zhao, L.; Blackney, M.; Watts, A. J. Med. Chem. 2010, 53,
2
(
(
6
(
(
1
465. (b) Stewart, G. W.; Shevlin, M.; Yamagata, A. D. G.; Gibson, A.
W.; Keen, S. P.; Scott, J. P. Org. Lett. 2012, 14, 5440.
9) (a) Enthaler, S.; Company, A. Chem. Soc. Rev. 2011, 40, 4912.
b) Taoues Temal-Laíb, J. C.; Zhu, J. J. Am. Chem. Soc. 2002, 124, 583.
c) Jiang, H.; Leger, J.-M.; Huc, I. J. Am. Chem. Soc. 2003, 125, 3448.
d) Roughley, S. D.; Jordan, A. M. J. Med. Chem. 2011, 54, 3451. (e) El
(
(
(
(
́
(
1
2
Khatib, M.; Molander, G. A. Org. Lett. 2014, 16, 4944.
10) (a) Ullmann, F. Chem. Ber. 1904, 37, 853. (b) General review:
Lindley, J. Tetrahedron 1984, 40, 1433.
(
3
(
11) For examples of C(sp )−H acetoxylation, see: (a) Dick, A. R.;
Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004, 126, 2300.
(
(
b) Chen, M. S.; White, M. C. J. Am. Chem. Soc. 2004, 126, 1346.
c) Desai, L. V.; Hull, K. L.; Sanford, M. S. J. Am. Chem. Soc. 2004,
Chem., Int. Ed. 2014, 53, 10439.
1
3
26, 9542. (d) Wang, D.-H.; Wu, D.-F.; Yu, J.-Q. Org. Lett. 2006, 8,
387. (e) Giri, R.; Liang, J.; Lei, J.-G.; Lei, J.-J.; Wang, D.-H.; Chen, X.;
2
(
3) For selected examales of vinyl C(sp )−H bonds functionalization,
see: (a) Zhang, Y.-H.; Shi, B.-F.; Yu, J.-Q. J. Am. Chem. Soc. 2009, 131,
072. (b) Zhou, H.; Xu, Y.-H.; Chung, W.-J.; Loh, T.-P. Angew. Chem.,
Naggar, I. C.; Guo, C.; Foxman, B. M.; Yu, J.-Q. Angew. Chem., Int. Ed.
005, 44, 7420. (f) Ju, L.; Yao, J.; Wu, Z.; Liu, Z.; Zhang, Y. J. Org.
Chem. 2013, 78, 10821.
12) For examples of C(sp )−H alkyoxylation, see: (a) Zhang, S. Y.;
He, G.; Zhao, Y.; Wright, K.; Nack, W. A.; Chen, G. J. Am. Chem. Soc.
012, 134, 7313. (b) Chen, F.-J.; Zhao, S.; Hu, F.; Chen, K.; Zhang,
5
2
Int. Ed. 2009, 48, 5355. (c) Xu, Y.-H.; Chok, Y. K.; Loh, T.-P. Chem.
Sci. 2011, 2, 1822. (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) Pankajakshan,
S.; Xu, Y.-H.; Cheng, J. K.; Low, M. T.; Loh, T.-P. Angew. Chem., Int.
Ed. 2012, 51, 5701. (f) Chen, M.; Ren, Z.-H.; Wang, Y.-Y.; Guan, Z.-
H. Angew. Chem., Int. Ed. 2013, 52, 14196. (g) Matsubara, T.; Asako,
S.; Ilies, L.; Nakamura, E. J. Am. Chem. Soc. 2014, 136, 646. (h) Yu, W.;
Chen, J.; Gao, K.; Liu, Z.; Zhang, Y. Org. Lett. 2014, 16, 4870. (i) Lin,
C.; Li, D.; Wang, B.; Yao, J.; Zhang, Y. Org. Lett. 2015, 17, 1328.
4) For selected examples on transition-metal catalyzed C(sp )−H
transformation, see: (a) Gutekunst, W. R.; Baran, P. S. Chem. Soc. Rev.
011, 40, 1976. (b) Zhang, C.; Tang, C.; Jiao, N. Chem. Soc. Rev. 2012,
1, 3464. (c) He, J.; Wasa, M.; Chan, K. S. L.; Yu, J.-Q. J. Am. Chem.
Soc. 2013, 135, 3387. (d) Ammann, S. E.; Rice, G. T.; White, M. C. J.
Am. Chem. Soc. 2014, 136, 10834. (e) Liu, B.; Zhou, T.; Li, B.; Xu, S.;
Song, H.; Wang, B. Angew. Chem., Int. Ed. 2014, 53, 4191. (f) Li, S.;
Chen, G.; Feng, C.-G.; Gong, W.; Yu, J.-Q. J. Am. Chem. Soc. 2014,
36, 5267. (g) Gong, W.; Zhang, G.; Liu, T.; Giri, R.; Yu, J.-Q. J. Am.
Chem. Soc. 2014, 136, 16940. (h) Cho, S. H.; Hartwig, J. F. Chem. Sci.
014, 5, 694.
5) For recent examples of C(sp )−H bonds functionalization by
using bidentate directing groups, see: (a) He, G.; Zhang, S. Y.; Nack,
W. A.; Li, Q.; Chen, G. Angew. Chem., Int. Ed. 2013, 52, 11124.
b) Zhang, Q.; Chen, K.; Rao, W.; Zhang, Y.; Chen, F. J.; Shi, B. F.
3
(
2
Q.; Zhang, S.-Q.; Shi, B.-F. Chem. Sci. 2013, 4, 4187. (c) Shan, G.;
Yang, X.; Zong, Y.; Rao, Y. Angew. Chem., Int. Ed. 2013, 52, 13606.
(13) For leading references, see: (a) Zaitsev, V. G.; Shabashov, D.;
Daugulis, O. J. Am. Chem. Soc. 2005, 127, 13154. (b) Daugulis, O.; Do,
H.-Q.; Shabashov, D. Acc. Chem. Res. 2009, 42, 1074.
3
(
(14) (a) García-Cuadrado, D.; Braga, A. A. C.; Maseras, F.;
Echavarren, A. M. J. Am. Chem. Soc. 2006, 128, 1066. (b) García-
Cuadrado, D.; Mendoza, P.; Braga, A. A. C.; Maseras, F.; Echavarren,
A. M. J. Am. Chem. Soc. 2007, 129, 6880.
2
4
(
(
15) Lafrance, M.; Fagnou, K. J. Am. Chem. Soc. 2006, 128, 16496.
16) (a) Sangermano, M.; Malucelli, G.; Bongiovanni, R.; Pirola, A.;
Annby, U.; Rehnberg, N. Eur. Polym. J. 2002, 38, 655. (b) Harmata,
M.; Lee, D. R.; Barnes, C. L. Org. Lett. 2005, 7, 1881.
1
(17) (a) Okimoto, Y.; Sakaguchi, S.; Ishii, Y. J. Am. Chem. Soc. 2002,
1
1
24, 1590. (b) Nordmann, G.; Buchwald, S. L. J. Am. Chem. Soc. 2003,
25, 4978. (c) Shade, R. E.; Hyde, A. M.; Olsen, J.-C.; Merlic, C. A. J.
2
(
3
Am. Chem. Soc. 2010, 132, 1202. (d) Zhang, L. B.; Hao, X. Q.; Zhang,
S. K.; Liu, Z. J.; Zheng, X. X.; Gong, J. F.; Niu, J. L.; Song, M. P. Angew.
Chem., Int. Ed. 2015, 54, 272.
(
(
18) Ammann, S. E.; Rice, G. T.; White, M. C. J. Am. Chem. Soc.
014, 136, 10834 and refs 11f, 17a and b.
19) Li, C.-J. Acc. Chem. Res. 2008, 42, 335.
Angew. Chem., Int. Ed. 2013, 52, 13588. (c) Li, M.; Dong, J.; Huang,
X.; Li, K.; Wu, Q.; Song, F.; You, J. Chem. Commun. 2014, 50, 3944.
d) Gu, Q.; Al Mamari, H. H.; Graczyk, K.; Diers, E.; Ackermann, L.
2
(
(
Angew. Chem., Int. Ed. 2014, 53, 3868. (e) Aihara, Y.; Chatani, N. J.
Am. Chem. Soc. 2014, 136, 898. (f) Wu, X.; Zhao, Y.; Ge, H. J. Am.
Chem. Soc. 2014, 136, 1789. (g) Wu, X.; Zhao, Y.; Ge, H. Chem.Eur.
J. 2014, 20, 1. (h) Wang, C.; Chen, C.; Zhang, J.; Han, J.; Wang, Q.;
Guo, K.; Liu, P.; Guan, M.; Yao, Y.; Zhao, Y. Angew. Chem., Int. Ed.
2
014, 53, 9884. (i) Wang, Z.; Ni, J.; Kuninobu, Y.; Kanai, M. Angew.
Chem., Int. Ed. 2014, 53, 3496. (j) Wu, X.; Zhao, Y.; Zhang, G.; Ge, H.
Angew. Chem., Int. Ed. 2014, 53, 3706. (k) Wang, Z.; Kuninobu, Y.;
Kanai, M. Org. Lett. 2014, 16, 4790. (l) Shang, M.; Sun, S.-Z.; Wang,
H.-L.; Laforteza, B. N.; Dai, H.-X.; Yu, J.-Q. Angew. Chem., Int. Ed.
2
014, 53, 10439. (m) Li, X.; Liu, Y.-H.; Gu, W.-J.; Li, B.; Chen, F.-J.;
Shi, B.-F. Org. Lett. 2014, 16, 3904. (n) Zhang, S. Y.; Li, Q.; He, G.;
Nack, W. A.; Chen, G. J. Am. Chem. Soc. 2015, 137, 531. (o) Lin, C.;
Yu, W.; Yao, J.; Wang, B.; Liu, Z.; Zhang, Y. Org. Lett. 2015, 17, 1340.
3
(
6) For C(sp )−H functionalization in organic synthesis, see:
(
a) Hinman, A.; Du Bois, J. J. Am. Chem. Soc. 2003, 125, 11510.
D
DOI: 10.1021/acs.orglett.5b01192
Org. Lett. XXXX, XXX, XXX−XXX