Catalytic Ester to Stannane Functional Group Interconversion via Decarbonylative Cross-Coupling of Methyl Esters

Article abstract of DOI:10.1021/acs.orglett.7b03669

An unprecedented conversion of methyl esters to stannanes was realized, providing access to a series of arylstannanes via nickel catalysis. Various common esters including ethyl, cyclohexyl, benzyl, and phenyl esters can undergo the newly developed decarbonylative stannylation reaction. The reaction shows broad substrate scope, can differentiate between different types of esters, and if applied in consecutive fashion, allows the transformation of methyl esters into aryl fluorides or biaryls via fluororination or arylation.

Full text of DOI:10.1021/acs.orglett.7b03669

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Catalytic Ester to Stannane Functional Group Interconversion via
Decarbonylative Cross-Coupling of Methyl Esters
Huifeng Yue,‡ Chen Zhu,‡ and Magnus Rueping*,‡,§
‡Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
§King Abdullah University of Science and Technology (KAUST), KAUST Catalysis Center (KCC), Thuwal 23955-6900, Saudi
Arabia
S
* Supporting Information
ABSTRACT: An unprecedented conversion of methyl esters to
stannanes was realized, providing access to a series of arylstannanes via
nickel catalysis. Various common esters including ethyl, cyclohexyl,
benzyl, and phenyl esters can undergo the newly developed decarbon-
ylative stannylation reaction. The reaction shows broad substrate scope,
can differentiate between different types of esters, and if applied in
consecutive fashion, allows the transformation of methyl esters into aryl
fluorides or biaryls via fluororination or arylation.
Scheme 1. Nickel-Catalyzed Reactions of Methyl Esters via
Non-decarbonylative and Decarbonylative Pathways
sters are one of the most ubiquitous classes of organic
Emolecules which exist in a wide range of natural products
and synthetic intermediates.1 Accordingly, the interconversions
between esters and other functional groups are important in
organic synthesis. Recently, increasing attention has been
devoted to cross-coupling reactions using cheap, green, and
readily available esters as coupling partners instead of commonly
used halogenated reagents.2−5 In particular, considerable
progress has been registered for decarbonylative and decarbox-
ylative reactions of esters to form diverse valuable compounds
including organoboron compounds.4,5 Although these methods
showed great advantages over conventional methodologies, the
substrate scope is mainly limited to phenyl esters. Commercially
available and inexpensive methyl esters seemed inefficient in
these transformations, which might be due to the higher bond-
dissociation energy (Figure 1).6
advantages including the widespread use and availability of
methyl esters as well as the formation and removal of methanol
instead of phenols, amides, or imides which have so far been
obtained as byproducts in decarbonylative processes.
Arylstannanes are highly important compounds due to their
application in the mild and versatile Migita−Kosugi−Stille
coupling reaction8 as well as in the synthesis of natural products
and late-stage functionalization of complex molecules.9 More-
over, they are frequently used in the construction of diverse
carbon−heteroatom bonds such as C−N,10 C−F,11 and C−
OCF312 bonds. Traditional methods to access stannanes employ
the reaction of trialkyltin chloride with air-sensitive organo-
metallic reagents, which may suffer from poor functional group
tolerance.13 Alternatively, palladium-14a−c and nickel-cataly-
zed14d−g stannylation of different electrophiles as well as C−H
Figure 1. Bond strength of acyl C−O bonds.
Progress in the activation of methyl esters has been made
recently by Garg, Houk, and co-workers as well as Hu and co-
workers, who described the nickel catalyzed direct amidation of
methyl esters with secondary arylamines and nitroarenes,
respectively (Scheme 1, eqs 1 and 2).7 However, these
transformations both underwent a nondecarbonylative process.
To the best of our knowledge, the decarbonylative reaction of
simple esters such as methyl esters has never been realized. This
is surprising since the use of methyl esters would have several
Received: November 26, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.7b03669
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
bond stannylation14g have been developed. One such endeavor
developed by the Martin group involves nickel-catalyzed
stannylation of phenol derivatives via activation of aryl C−O
bonds using trimethyl(tributylstannyl)silane.14f
Given the great importance of arylstannanes and the limited
number of available synthetic methods, it is highly desirable to
explore novel and practical methods to access these compounds.
As part of our continuing efforts in the activation of inert bonds
we, herein, report an unprecedented decarbonylative stannyla-
tion reaction of simple methyl esters as well as other common
esters such as ethyl, cyclohexyl, benzyl, and phenyl esters
(Scheme 1, eq 3). This transformation represents the first
decarbonylative reaction of methyl esters and features wide
substrate scope and broad functional group tolerance.
We started to explore the decarbonylative stannylation of
methyl esters by choosing methyl 2-naphthoate (1a) as a model
substrate in the reaction with trimethyl(tributylstannyl)silane 2.
After surveying various ligands, bases, nickel catalysts, and
solvents, the optimal reaction conditions were assigned as
follows: Ni(cod)2, dppp as ligand, KF as base, LiCl as additive in
toluene at 170 °C for 48 h (for details, see Table S1).
With the optimized reaction conditions in hand, the scope
with respect to the methyl esters was explored (Scheme 2). A
series of methyl esters could be converted into the
corresponding products smoothly, regardless of the electronic
nature of the substituents on the aromatic ring. Whereas methyl
2-naphthoate (1a) underwent the decarbonylative stannylation
reaction in excellent yield, methyl 1-naphthoate (1b) gave the
corresponding product in only 52% yield, which was presumably
due to steric effects. In contrast to a previous report in which the
substrate scope was largely limited to naphthoic acid methyl
esters,5a our newly developed decarbonylative stannylative
protocol could be applied to simple benzoic acid methyl esters.
For instance, p- and even o-biphenyl carboxylic methyl esters
1c−e could be successfully converted into the corresponding
arylstannanes.
In addition, the reaction showed remarkable chemoselectivity
since a wide range of functional groups such as tert-butyl (1e),
methyl (1f), fluoro (1g and 1h), trifluoromethyl (1i), amide (1j
and 1k), methoxy (1m), and double bond (1n) were well
tolerated. Given the previous reports on nickel-catalyzed C−F,
C−N, and C−O bond activation, these results show great
relevance due to the further functionalization potential of the
untouched inert bonds. Moreover, disubstituted substrate 1m
could also undergo this protocol in high yield. Notably,
pharmaceutically relevant heteroaromatic substrates such as
pyridine-derived carboxylic acid methyl esters 1n and 1o were
also suitable substrates for this transformation and were
converted into the corresponding products in good to excellent
yields.
Furthermore, our catalytic protocol could also be readily
extended to aryl carboxylic acid phenyl esters 4 by using an
inexpensive nickel source NiBr2 as catalyst and Cs2CO3 as base
(Scheme 3). Likewise, both naphthoic acid and benzoic acid
phenyl esters could undergo the present reaction smoothly,
giving the desired products in moderate to high yields. As shown
in Table S2, the reaction of phenyl 2-naphthoate (4a) proceeded
in 82% yield. Most of the biphenyl carboxylic acid phenyl esters
(4b−f) could be converted into the biphenylstannanes in good
yields. Only substrate 4d substituted at the ortho position of the
aromatic ring led to a lower yield. Again, various functional
groups were well tolerated in the new decarbonylative
stannylation reaction, affording the products in good yields. It
is noteworthy that more complex substrates such as estrone-
derived carboxylate 4t also reacted well.
a,b
Scheme 2. Scope of the Methyl Esters
In addition to methyl and phenyl esters, other types of simple
esters were also evaluated. Ethyl, cyclohexyl, and benzyl ester
derivatives 6a−c could all be converted into 3a in good yields,
indicating the advantages of our newly developed decarbon-
ylative stannylation protocol (Scheme 4). To explore whether
this new methodology could efficiently differentiate between
two different types of esters, we subjected substrate 7 bearing
both methyl and phenyl ester groups to the present reaction
conditions. Gratifyingly, substrate 7 underwent this trans-
formation with excellent chemoselectivity, and the phenyl ester
group was selectively stannylized, delivering product 8 bearing
the methyl ester untouched in good yield (Scheme 5, eq 1).
Interestingly, monostannylation of substrate 9 bearing two
methyl ester groups was also realized, affording product 10 in
good yield along with trace amount of the double-stannylated
product. More importantly, further reaction of 10 with
Selectfluor or methyl 4-bromobenzoate gave the monofluorina-
tion or monoarylation product (11 and 12) of bis-methyl ester 9,
thus enabling the challenging interconversion between methyl
esters and other important functional groups (Scheme 5, eq 2).
In summary, the functional group interconversion of inert
methyl esters into stannanes was realized for the first time with
the aid of nickel catalysis. A series of methyl esters as well as
other common esters, such as ethyl, cyclohexyl, benzyl and
a
Reaction conditions: 1 (0.2 mmol), 2 (0.3 mmol, 1.5 equiv),
Ni(cod)2 (0.02 mmol, 10 mol %), dppp (0.04 mmol, 20 mol %), KF
(0.4 mmol, 2 equiv), LiCl (0.4 mmol, 2 equiv) in toluene (1 mL) at
b
c
170 °C, 48 h. Yield after purification. Yield for 1 mmol scale
reaction, 60 h. 72 h.
d
B
DOI: 10.1021/acs.orglett.7b03669
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a,b
Scheme 3. Scope of the Phenyl Esters
Scheme 5. (a) Selective Stannylation of Phenyl Ester with
Methyl Ester Untouched. (b) Mono-stannylation/
Fluorination and Arylation of Bis-methyl Esters
phenyl esters, all underwent this decarbonylative stannylation
protocol smoothly, affording diverse arylstannanes which are
important in the construction of C−C and C−heteroatom
bonds. Moreover, this method could efficiently differentiate
between two different types of esters. In addition, the
monostannylation/fluorination and monostannylation/aryla-
tion of bis-methyl esters could be realized, showing its great
practical value. Furthermore, the stannylation protocol shows
good chemoselectivity and functional groups including groups
previously used in cross-couplings remain intact. Given that
arylstannanes are highly valuable products for different
applications, this new ester to stannane interconversion will be
of value and may become a good alternative to aryl halide
stannylation reactions. Efforts to investigate the mechanism and
to broaden the scope further are currently ongoing in our
laboratories and will be reported in due course.
a
Reaction conditions: 4 (0.2 mmol), 2 (0.3 mmol, 1.5 equiv), NiBr2
(0.02 mmol, 10 mol %), dppp (0.04 mmol, 20 mol %), Cs2CO3 (0.4
mmol, 20 mol %), LiCl (0.4 mmol, 20 mol %) in toluene (1 mL) at
b
c
170 °C, 12 h. Yield after purification. Yield for 1 mmol scale
reaction, 60 h.
a,b
Scheme 4. Scope of Other Simple Esters
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.orglett.7b03669.
Detailed experimental procedures, spectral data for all
1
compounds, and H, 13C, 19F, and 119Sn NMR spectra
(PDF)
AUTHOR INFORMATION
■
a
Corresponding Author
*E-mail: magnus.rueping@rwth-aachen.de.
ORCID
Reaction conditions: 6 (0.2 mmol), 2 (0.3 mmol, 1.5 equiv),
Ni(cod)2 (0.02 mmol, 10 mol %), dppp (0.04 mmol, 20 mol %), KF
(0.4 mmol, 2 equiv), LiCl (0.4 mmol, 2 equiv) in toluene (1 mL) at
b
c
170 °C, 48 h. Yield after purification. Reaction conditions as for
phenyl esters were used, 24 h.
Magnus Rueping: 0000-0003-4580-5227
Notes
The authors declare no competing financial interest.
C
DOI: 10.1021/acs.orglett.7b03669
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Chem., Int. Ed. 2017, 56, 3972−3976. (q) Liu, X.; Jia, J.; Rueping, M.
ACS Catal. 2017, 7, 4491−4496. (r) Chatupheeraphat, A.; Liao, H.-H.;
Lee, S.-C.; Rueping, M. Org. Lett. 2017, 19, 4255−4258. (s) Okita, T.;
Kumazawa, K.; Takise, R.; Muto, K.; Itami, K.; Yamaguchi, J. Chem.
Lett. 2017, 46, 218−220. For theoretical studies, see: (t) Hong, X.;
Liang, Y.; Houk, K. J. Am. Chem. Soc. 2014, 136, 2017−2025. (u) Lu,
Q.; Yu, H.; Fu, Y. J. Am. Chem. Soc. 2014, 136, 8252−8260. For a recent
review, see: (v) Takise, R.; Muto, K.; Yamaguchi, J. Chem. Soc. Rev.
2017, 46, 5864−5888.
(5) (a) Fawcett, A.; Pradeilles, J.; Wang, Y.; Mutsuga, T.; Myers, E. L.;
Aggarwal, V. K. Science 2017, 357, 283−286. (b) Li, C.; Wang, J.;
Barton, L. M.; Yu, S.; Tian, M.; Peters, D. S.; Kumar, M.; Yu, A. W.;
Johnson, K. A.; Chatterjee, A. K.; Yan, M.; Baran, P. S. Science 2017,
356, eaam7355. (c) Hu, D.; Wang, L.; Li, P. Org. Lett. 2017, 19, 2770−
2773.
ACKNOWLEDGMENTS
■
H.Y. was supported by the China Scholarship Council.
REFERENCES
■
(1) (a) Trost, B. M.; Fleming, I. Comprehensive Organic Synthesis;
Pergamon Press: New York, 1992; Vol. 6. (b) Larock, R. C.
Comprehensive Organic Transformations, 2 ed.; Wiley-VCH: New
York, 1999. (c) Smith, M. B. In Compendium of Organic Synthetic
Methods; Wiley: New York, 2001; Vol. 9, p 100.
(2) For selected recent examples of aryl C−O bond activation
reactions of esters, see: (a) Quasdorf, K. W.; Tian, X.; Garg, N. K. J. Am.
Chem. Soc. 2008, 130, 14422−14423. (b) Li, B. J.; Li, Y. Z.; Lu, X. Y.;
Liu, J.; Guan, B. T.; Shi, Z. J. Angew. Chem., Int. Ed. 2008, 47, 10124−
10127. (c) Guan, B.-T.; Wang, Y.; Li, B.-J.; Yu, D.-G.; Shi, Z.-J. J. Am.
Chem. Soc. 2008, 130, 14468−14470. (d) Li, B.-J.; Xu, L.; Wu, Z.-H.;
Guan, B.-T.; Sun, C.-L.; Wang, B.-Q.; Shi, Z.-J. J. Am. Chem. Soc. 2009,
131, 14656−14657. (e) Molander, G. A.; Beaumard, F. Org. Lett. 2010,
12, 4022−4025. (f) Shimasaki, T.; Tobisu, M.; Chatani, N. Angew.
Chem., Int. Ed. 2010, 49, 2929−2932. (g) Muto, K.; Yamaguchi, J.;
Itami, K. J. Am. Chem. Soc. 2012, 134, 169−172. (h) Ehle, A. R.; Zhou,
Q.; Watson, M. P. Org. Lett. 2012, 14, 1202−1205. (i) Yang, J.; Chen,
T.; Han, L.-B. J. Am. Chem. Soc. 2015, 137, 1782−1785. (j) Takise, R.;
Muto, K.; Yamaguchi, J.; Itami, K. Angew. Chem., Int. Ed. 2014, 53,
6791−6794. (k) Kinuta, H.; Hasegawa, J.; Tobisu, M.; Chatani, N.
Chem. Lett. 2015, 44, 366−368. (l) Zarate, C.; Martin, R. J. Am. Chem.
(6) Luo, Y.-R. Comprehensive Handbook of Chemical Bond Energies;
CRC Press: Boca Raton, 2007.
(7) (a) Hie, L.; Fine Nathel, N. F.; Hong, X.; Yang, Y. F.; Houk, K. N.;
Garg, N. K. Angew. Chem., Int. Ed. 2016, 55, 2810−2814. (b) Cheung,
C. W.; Ploeger, M. L.; Hu, X. Nat. Commun. 2017, 8, 14878.
(8) (a) Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508−524.
(b) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem.
Rev. 2002, 102, 1359−1470. (c) Espinet, P.; Echavarren, A. M. Angew.
Chem., Int. Ed. 2004, 43, 4704−4734. (d) Johansson Seechurn, C. C.;
Kitching, M. O.; Colacot, T. J.; Snieckus, V. Angew. Chem., Int. Ed. 2012,
51, 5062−5085.
(9) (a) Ragan, J.; Raggon, J.; Hill, P.; Jones, B.; McDermott, R.;
Munchhof, M.; Marx, M.; Casavant, J.; Cooper, B.; Doty, J. Org. Process
Res. Dev. 2003, 7, 676−683. (b) Alonso, E.; Fuwa, H.; Vale, C.; Suga, Y.;
Goto, T.; Konno, Y.; Sasaki, M.; LaFerla, F. M.; Vieytes, M. R.;
́
Soc. 2014, 136, 2236−2239. (m) Correa, A.; Leon, T.; Martin, R. J. Am.
Chem. Soc. 2014, 136, 1062−1069. (n) Correa, A.; Martin, R. J. Am.
Chem. Soc. 2014, 136, 7253−7256. (o) Cornella, J.; Jackson, E. P.;
Martin, R. Angew. Chem., Int. Ed. 2015, 54, 4075−4078. (p) Takise, R.;
Itami, K.; Yamaguchi, J. Org. Lett. 2016, 18, 4428−4431. (q) Guo, L.;
Hsiao, C.-C.; Yue, H.; Liu, X.; Rueping, M. ACS Catal. 2016, 6, 4438−
4442. (r) Yue, H.; Guo, L.; Liu, X.; Rueping, M. Org. Lett. 2017, 19,
1788−1791. For theoretical studies, see: (s) Li, Z.; Zhang, S.-L.; Fu, Y.;
Guo, Q.-X.; Liu, L. J. Am. Chem. Soc. 2009, 131, 8815−8823. (t) Muto,
K.; Yamaguchi, J.; Lei, A.; Itami, K. J. Am. Chem. Soc. 2013, 135, 16384−
16387. (u) Xu, H.; Muto, K.; Yamaguchi, J.; Zhao, C.; Itami, K.;
Musaev, D. G. J. Am. Chem. Soc. 2014, 136, 14834−14844.
́
Gimenez-Llort, L. J. Am. Chem. Soc. 2012, 134, 7467−7479. (c) Valot,
G.; Regens, C. S.; O’Malley, D. P.; Godineau, E.; Takikawa, H.;
Furstner, A. Angew. Chem., Int. Ed. 2013, 52, 9534−9538. (d) Li, J.;
̈
Yang, P.; Yao, M.; Deng, J.; Li, A. J. Am. Chem. Soc. 2014, 136, 16477−
16480. (e) Mailhol, D.; Willwacher, J.; Kausch-Busies, N.; Rubitski, E.
E.; Sobol, Z.; Schuler, M.; Lam, M.-H.; Musto, S.; Loganzo, F.;
Maderna, A.; Furstner, A. J. Am. Chem. Soc. 2014, 136, 15719−15729.
̈
(f) Logan, M. M.; Toma, T.; Thomas-Tran, R.; Du Bois, J. Science 2016,
354, 865−869.
(3) Examples of acyl C−O bond activations of esters via a non-
decarbonylative pathway: (a) Kakino, R.; Shimizu, I.; Yamamoto, A.
Bull. Chem. Soc. Jpn. 2001, 74, 371−376. (b) Tatamidani, H.; Kakiuchi,
F.; Chatani, N. Org. Lett. 2004, 6, 3597−3599. (c) Tatamidani, H.;
Yokota, K.; Kakiuchi, F.; Chatani, N. J. Org. Chem. 2004, 69, 5615−
5621. (d) Ben Halima, T.; Vandavasi, J. K.; Shkoor, M.; Newman, S. G.
ACS Catal. 2017, 7, 2176−2180. (e) Ben Halima, T.; Zhang, W.;
Yalaoui, I.; Hong, X.; Yang, Y.-F.; Houk, K. N.; Newman, S. G. J. Am.
Chem. Soc. 2017, 139, 1311−1318.
(10) Lam, P. Y.; Vincent, G.; Bonne, D.; Clark, C. G. Tetrahedron Lett.
2002, 43, 3091−3094.
(11) (a) Furuya, T.; Strom, A. E.; Ritter, T. J. Am. Chem. Soc. 2009,
131, 1662−1663. (b) Tang, P.; Furuya, T.; Ritter, T. J. Am. Chem. Soc.
2010, 132, 12150−12154. (c) Ye, Y.; Sanford, M. S. J. Am. Chem. Soc.
2013, 135, 4648−4651. (d) Gamache, R. F.; Waldmann, C.; Murphy, J.
M. Org. Lett. 2016, 18, 4522−4525.
(12) Huang, C.; Liang, T.; Harada, S.; Lee, E.; Ritter, T. J. Am. Chem.
Soc. 2011, 133, 13308−13310.
(4) For examples of acyl C−O bond activation reactions of esters via a
decarbonylative pathway, see: (a) Gooßen, L. J.; Paetzold, J. Angew.
Chem., Int. Ed. 2002, 41, 1237−1241. (b) Gribkov, D. V.; Pastine, S. J.;
(13) (a) Soderquist, J. A.; Hassner, A. J. Am. Chem. Soc. 1980, 102,
1577−1583. (b) Knochel, P.; Singer, R. D. Chem. Rev. 1993, 93, 2117−
́
2188. (c) Gosmini, C.; Perichon, J. Org. Biomol. Chem. 2005, 3, 216−
Schnurch, M.; Sames, D. J. Am. Chem. Soc. 2007, 129, 11750−11755.
̈
217.
(c) Amaike, K.; Muto, K.; Yamaguchi, J.; Itami, K. J. Am. Chem. Soc.
2012, 134, 13573−13576. (d) Meng, L.; Kamada, Y.; Muto, K.;
Yamaguchi, J.; Itami, K. Angew. Chem., Int. Ed. 2013, 52, 10048−10051.
(e) Muto, K.; Yamaguchi, J.; Musaev, D. G.; Itami, K. Nat. Commun.
2015, 6, 7508. (f) LaBerge, N. A.; Love, J. A. Eur. J. Org. Chem. 2015,
2015, 5546−5553. (g) Desnoyer, A. N.; Friese, F. W.; Chiu, W.; Drover,
M. W.; Patrick, B. O.; Love, J. A. Chem. - Eur. J. 2016, 22, 4070−4077.
(h) Guo, L.; Chatupheeraphat, A.; Rueping, M. Angew. Chem., Int. Ed.
2016, 55, 11810−11813. (i) Guo, L.; Rueping, M. Chem. - Eur. J. 2016,
22, 16787−16790. (j) Pu, X.; Hu, J.; Zhao, Y.; Shi, Z. ACS Catal. 2016,
6, 6692−6698. (k) Amaike, K.; Itami, K.; Yamaguchi, J. Chem. - Eur. J.
2016, 22, 4384−4388. (l) Muto, K.; Hatakeyama, T.; Itami, K.;
Yamaguchi, J. Org. Lett. 2016, 18, 5106−5109. (m) Isshiki, R.; Takise,
R.; Itami, K.; Muto, K.; Yamaguchi, J. Synlett 2017, 28, 2599−2603.
(n) Takise, R.; Isshiki, R.; Muto, K.; Itami, K.; Yamaguchi, J. J. Am.
Chem. Soc. 2017, 139, 3340−3343. (o) Yue, H.; Guo, L.; Liao, H. H.;
Cai, Y.; Zhu, C.; Rueping, M. Angew. Chem., Int. Ed. 2017, 56, 4282−
4285. (p) Yue, H.; Guo, L.; Lee, S. C.; Liu, X.; Rueping, M. Angew.
(14) (a) Azizian, H.; Eaborn, C.; Pidcock, A. J. Organomet. Chem.
1981, 215, 49−58. (b) Corcoran, E. B.; Williams, A. B.; Hanson, R. N.
Org. Lett. 2012, 14, 4630−4633. (c) Wulff, W. D.; Peterson, G. A.;
Bauta, W. E.; Chan, K.-S.; Faron, K. L.; Gilbertson, S. R.; Kaesler, R. W.;
Yang, D. C.; Murray, C. K. J. Org. Chem. 1986, 51, 277−279.
(d) Komeyama, K.; Asakura, R.; Takaki, K. Org. Biomol. Chem. 2015,
13, 8713−8716. (e) Shirakawa, E.; Nakao, Y.; Yoshida, H.; Hiyama, T.
J. Am. Chem. Soc. 2000, 122, 9030−9031. (f) Gu, Y.; Martín, R. Angew.
Chem., Int. Ed. 2017, 56, 3187−3190. (g) Doster, M. E.; Hatnean, J. A.;
Jeftic, T.; Modi, S.; Johnson, S. A. J. Am. Chem. Soc. 2010, 132, 11923−
11925. (h) Qiu, D.; Meng, H.; Jin, L.; Wang, S.; Tang, S.; Wang, X.; Mo,
F.; Zhang, Y.; Wang, J. Angew. Chem., Int. Ed. 2013, 52, 11581−11584.
D
DOI: 10.1021/acs.orglett.7b03669
Org. Lett. XXXX, XXX, XXX−XXX