Highly selective copper-catalyzed trifunctionalization of alkynyl carboxylic acids: An efficient route to bis-deuterated β-borylated α,β-styrene

Article abstract of DOI:10.1039/c5cc05084g

A copper-catalyzed highly efficient protocol for the synthesis of bis-deuterated β-borylated α,β-styrene derivatives, which can be further transformed to practical isotopically labeled compounds, has been developed. Alkynyl carboxylic acids are employed as alkyne synthons yet demonstrate a sharp discrepancy in reactivity and selectivity compared to terminal alkynes. Meanwhile, this reaction offers a novel and efficient strategy for highly selective trifunctionalization of the carbon-carbon triple bond at ambient temperature.

Full text of DOI:10.1039/c5cc05084g

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Q. Feng, K. Yang
and Q. Song, Chem. Commun., 2015, DOI: 10.1039/C5CC05084G.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/chemcomm

Please do not adjust margins
ChemComm
Page 1 of 4
View Article Online
DOI: 10.1039/C5CC05084G
Chem Commun
COMMUNICATION
Highly Selective Copper-Catalyzed Trifunctionalization of Alkynyl
Carboxylic Acids: An Efficient Route to Bis-Deuterated β-Borylated
α, β-Styrene
Received 00th January 20xx,
Accepted 00th January 20xx
Qiang Fenga, Kai Yanga and Qiuling Songa, b*
DOI: 10.1039/x0xx00000x
www.rsc.org/
Abstract: A copper-catalyzed highly efficient protocol for the
synthesis of bis-deuterated β-borylated α, β-styrene derivatives,
which can be further transformed to practical isotopically labeled
compounds, has been developed. Alkynyl carboxylic acids are
[34]
D
O
B
B2pin2, CuCl, NaOtBu
O
O
(1)
(2)
H
H
Dpephos, MeOD
THF, 24 h, rt
D
[48]
employed as alkyne synthons yet demonstrate
a sharp
[86]
D
discrepancy in reactivity and selectivity from terminal alkynes.
Meanwhile, this reaction offers a novel and efficient strategy to
highly selective trifunctionalization of carbon-carbon triple bond
at ambient temperature.
O
B
micro Copper powder
B2pin2, NaOMe
Dpephos, MeOD
24 h, rt
D
[27]
As part of our ongoing research on the development of highly
efficient and versatile copper-catalyzed decarboxylative reactions,[9]
decarboxylative coupling from alkynyl carboxylic acid also attracted
our great interest. Inspired by the mechanistic investigations on
both the copper-catalyzed decarboxylation from alkynyl carboxylic
acid[10] and the copper-catalyzed hydroborylation reaction[11], we
envisioned that a (E)-alkenyl-bis-copper reactive intermediate E,
which has two reactive positions with two copper atoms on, could
be generated in situ from alkynyl carboxylic acid with diboron
reagent in the presence of copper salt under proper conditions. We
anticipated that if electrophiles, such as D+, were added, the two
active copper atoms would react to afford the (E)-bis-deuterated β-
borylated α, β-styrene with both high regio- and
chemoselectivitives (Scheme 1).
Efficient incorporation of deuterium is a valuable transformation
for the preparation of isotopically labeled compounds that have
wide applications in mechanistic investigations of organic
transformations, spectroscopic analysis, or the monitoring of
metabolism.[1] Alkenylboron compounds are especially versatible
building blocks that are widely employed as vinyl anionic or cationic
synthons in a myriad of coupling reactions,[2] as well as they can be
readily transformed into various vinylic derivatives.[3] Owing to the
versatile application of vinylic derivatives in organic synthesis,
especially in the C-H functionalization of C=C bond,[4] alkenylboron
compounds with deuteration at α, β positions would be increasingly
attractive in organic synthesis for mechanistic study[5]. Over the
past decade, great progress have been achieved on the transition-
metal-catalyzed formations of alkenylboron compounds.[6] Among
them, hydroborylation of C≡C bonds presents a convenient and
important strategy for alkenylboron synthesis.[7] To the best of our
B2pin2
Cu salt
D
O
B
CuL
O
B
D+
(3)
COOH
O
O
D
CO2
CuL
E
knowledge, however, no straightforward and highly efficient Scheme 1. Putative mechanism
approach to alkenylboron compounds with deuteration at α, β
positions under ambient temperature has been reported yet.
Herein, we reported a copper-catalyzed straightforward and
Existing methods for accessing the (E)-bis-deuterated β-borylated α, highly efficient protocol for the synthesis of (E)-bis-deuterated β-
β-styrene suffer from low deuteration at α, β positions [Eqs. (1)- borylated α, β-styrene derivatives from alkynyl acids with
(2)].[7c], [8] It remains a big challenge to selectively synthesize bis- bis(pinacolato)diboron by employing readily available and cheap
deuterated β-borylated α, β-styrene as one single isomer with high D2O as a deuterium source under mild reaction conditions. In this
deuterium incorporation.
protocol, alkynyl acids serve as alkyne synthons yet demonstrate
superior reactivity and regio- and chemo-selectivities in comparison
to phenylacetylenes [Eqs. (4)-(5)]. Comparative studies with
phenylacetylenes and bis(pinacolato)diboron based on precedent
methods [Eqs. (1)-(2)] further emphasize the significance, essential
and superiority of alkynyl carboxylic acids in this protocol.
Moreover, this protocol might provide a general strategy to highly
selective trifunctionalization of C≡C bond at mild conditions, which
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 4
View Article Online
DOI: 10.1039/C5CC05084G
COMMUNICATION
Journal Name
hopefully will attract more organic chemists working on this Table1. Optimization of the reaction parameters.[a]
appealing field.
Our initial efforts towards the copper-catalyzed synthesis of (E)-
bis-deuterated β-borylated α, β-styrene derivatives commenced
with the treatment of phenylpropiolic acid 1a (0.5 mmol) and
bis(pinacolato)diboron 2 (1.2 equiv., 0.6 mmol) with copper salts
(10 mol%) as catalysts, D2O (6 equiv., 3 mmol) as deuterium source
in the presence of bases and solvents (1 mL) at various temperature
under 1 atm N2 (SI, Table 1). According to the previous reports,
most of transition-metal catalyzed additions of diboron to C≡C
bonds were performed successfully with essential bases.
Surprisingly, in our process of condition screening, (E)-bis-
deuterated β-borylated α, β-styrene (3a) was obtained in 37% yield
(Table 1, entry 2) in the absence of base. This result inspired us and
then we attempted to conduct the reaction under base-free
conditions (SI, Table 2). To our delight, when the reaction was
conducted with Cu2O (10 mol%) at 80 oC, (E)-bis-deuterated β-
borylated α, β-styrene (3a) was obtained in a 76% yield (entry 3),
which was similar to the optimal reaction conditions with base
3k–3m, 3n–3p), with ortho-substitution usually giving lower yields
of desired products when compared to meta- and para-
(entry 1). Further solvents screening demonstrated that 1, 4-
dioxane was the best solvent (entries 3-8). Most remarkably, (E)-
bis-deuterated β-borylated α, β-styrene (3a) was obtained in 96%
substitution, probably as
a result of steric hindrance. It is
o
noteworthy that halo-substituted aryl groups survived well in this
transformation, leading to halo-substituted aromatic bis-deterated
β-borylated α, β-styrene which could be used for further structural
manipulations. In addition, 1-naphthyl, para-phenyl substituted
phenylpropiolic acid (3s–3t) were also transformed well into
corresponding desired products in excellent yields, and
heteroaromatic propiolic acid, for instance 3-(thiophen-2-yl)
propiolic acid (3u) was competent in this transformation as well and
afforded the desired product in a moderate yield. Significantly, base
sensitive functional groups, such as alchohol, ketone and ester
groups were also compatible in this transformation and readily
turned into corresponding bis-deuterated β-borylated α, β-styrene
in this protocol (3v–3x). Finally, aliphatic alkynyl carboxylic acids
(3y–3z) were also proven to be good candidates in this general
protocol, further emphasizing the wide scope of this transformation.
To demonstrate the synthetic utility of the (E)-bis-deuterated β-
borylated α, β-styrene derivatives obtained by the present method,
Suzuki–Miyaura cross-coupling reaction[12] was first conducted with
the in situ generated 3a, and (E)-bis-deuterated diphenylethene 4
was obtained in 78% overall yield via the two-step one-pot
sequence [(Eq. (6)].
GC yield (entry 10) at room temperature vs. 31% GC yield at 80 C
when PPh3 was employed (10 mol%) as ligand, probably due to an
enormous ligand effect on the reactivity of copper complex.
Encouraged by this result, further ligand screenings suggested that
Xantphos is the superior one over PCy3, DPPE, Dpephos, 1,10-Phen,
P(n-Bu)3 and NHC in this transformation, yet PPh3, DPPB might be
alternatives for this reaction (entries 17–23). Among copper
catalysts, Cu(OAc)2 also exhibited a good reactivity (85% GC yield)
(entry 21), yet no reaction was detected in the presence of CuCl, CuI,
and CuO (entries 12, 14, 15).
Eventually, the optimal reaction conditions emerged as
phenylpropiolic acid (1a) (0.5 mmol), bis(pinacolato)diboron (2) (1.2
equiv., 0.6 mmol), Cu2O (10 mol%), Xantphos (10 mol%), D2O (6
equiv., 3 mmol), 1,4-dioxane (1 mL) at ambient temperature.
Notably, (E)-β-vinylboronate was detected as the single product,
and no other isomers such as α-vinylbonate and (Z)-β-vinylboronate
which are either products or by-products in the previous reports
were ever detected.
After establishing the optimized reaction conditions, a variety of
alkynyl carboxylic acids were subjected to the optimized conditions
to evaluate the scope of copper-catalyzed formation of bis-
deuterated β-borylated α, β-styrene derivatives. As shown in
Scheme 2, arylpropiolic acids with electron-rich groups on the
aromatic ring (3b–3g) could be smoothly converted into the desired
products in excellent yields. Arylpropiolic acids bearing electron-
deficient substituents (3h–3p, 3q–3r) were less effective with the
formation of the desired products in moderate to good yields, yet
the deuterium incorporation was >95%. The position of the
substitutes on the aromatic rings had great effect on yields (3h–3j,
Moreover, the usefulness of these novel bis-deuterated styrene
derivatives was further emphasized by transformation of the boron
substituent into various functional groups (Scheme 3). (E)-Bis-
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 3 of 4
View Article Online
DOI: 10.1039/C5CC05084G
Journal Name
COMMUNICATION
acetate.[4c] As vinyl azides are useful intermediates in the synthesis
of various heterocyclic compounds and transition metal complexes,
as well as important components in many functional materials like
the photo-affinity labeling agents for proteins, (E)-(2-azidovinyl-1,2-
d2)benzene 8 were prepared from (E)-bis-deuterated β-borylated α,
β-styrene with sodium azide in 83% yield.[4d] In addition, some other
important molecules such as cinnamic-2,3-d2 acid 9, (E)-(2-phenyl-
vinyl-1,2-d2)boronic acid 10, (E)-2-(1-morpholino-3-phenylallyl-2,3-
d2)phenol 11, (E)-(2-fluorovinyl-1,2-d2)benzene 12 could also be
prepared under mild conditions according to the reported
literature.[4e-4h]
B2pin2,D2O
Cu2O, N2
D
O
B
R
COOH
O
R
Xantphos
1,4-dioxane
rt, 18 h
D
1
3
D
O
D
O
B
D
O
B
B
O
O
O
D
D
D
O
3a, 90%, 57%[b]
3b, 87%
3c, 88%
D
O
B
D
O
B
D
O
B
O
O
O
D
D
D
3d
, 87%
3e
3f, 90%
, 80%
D
O
B
D
O
B
D
O
B
O
O
O
D
D
D
F
F
3g
, 82%
3h
, 63%
3i, 75%
D
O
B
D
O
D
O
B
B
O
O
O
D
D
D
F
Cl
Cl
3j
, 73%
3k, 35%
3l, 84%
D
O
B
D
O
D
O
B
B
O
O
O
D
D
3m, 87%
D
Cl
Br
Br
3o, 74%
3n, 34%
D
O
B
D
O
D
O
B
B
O
O
O
D
D
F3C
D
NC
Br
3r, 59%
3p
, 77%
3q, 70%
D
O
D
O
B
D
O
B
B
S
Scheme 3. Synthetic transformations from (E)-bis-deuterated β-borylated α,
O
O
O
D
β-styrene 3a.
D
D
Ph
3s, 93%
3t, 80%
3u
, 54%
In order to investigate the reaction mechanism,
(phenylethynyl)copper[13] 13 was employed under the standard
condition. However, the starting material was remained and no
desired product (E)-bis-deuterated β-borylated α, β-styrene 3a was
detected. Probably, the very low solubility of (phenylethynyl)copper
in 1,4-dixoane leads to inactivity of this reaction. Thus, we
employed catalytic amount of (phenylethynyl)copper as the catalyst
under the standard conditions. To our delight, (E)-bis-deuterated β-
borylated α,β-styrene was afforded in 78% yield [(Eq. (8)]. This
result suggested that this transformation might proceed through a
(phenylethynyl)copper intermediate, following by the formation of
(E)-alkenyl-bis-copper reactive intermediate E in Scheme 1.
B2pin2, D2O
Xantphos
D
O
B
Scheme 2. Copper-catalyzed formation of (E)-bis-deuterated β-borylated α,
β-styrene derivatives from various alkynyl carboxylic acids.[a]
Cu
O
(7)
1,4-dioxane
N2, rt, 18 h
D
13
deuterated potassium alkenyltrifluoroborate 5 and vinyl iodide 6,
which have been designated as one of the most important coupling
partners in transition-metal-catalyzed syntheses, were prepared
from (E)-bis-deuterated β-borylated α, β-styrene over two steps in
84%[4a] and 84%[4b] yields respectively. Furthermore, (E)-(2-
(allyloxy)vinyl-1,2-d2)benzene 7, one of valuable enol ethers which
have been considered as synthetic intermediates in various organic
reactions such as in the [2+2]-cycloaddition and Claisen
rearrangement, was obtained in 89% yield from (E)-bis-deuterated
β-borylated α, β-styrene with allyl achohol in the presence of cupric
3a
, with Cu2O, 0%
without Cu2O, 0%
Ph
(10 mol%)
Cu
D
O
B
Xantphos
O
(8)
COOH
D
B2pin2, D2O
1,4-dioxane
N2, rt, 18 h
1a 0.5 mmol
3a
, yiled: 78%
To evaluate the influence of active hydrogen from the alkynyl
acids on both yield and degree of deuterium incorporation,
potassium 3-phenylpropiolate 14, which was prepared according
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 4
View Article Online
DOI: 10.1039/C5CC05084G
COMMUNICATION
Journal Name
the reported literature[14], was utilized as the alkyne synthon under
the standard condition. Significantly, little discrepancy was detected
on the degree of deuterium incorporation of (E)-bis-deuterated β-
borylated α, β-styrene 3a, even though the yield declined to 51%,
probably as a result of low solubility of carboxylate 14 [(Eq. (9)].
This result demonstrated that active hydrogen from the alkynyl
acids almost has no influence on the degree of deuterium
incorporation.
S. Lu; S. Telu, F. I. Aigbirhio and V. W. Pike, Angew. Chem. Int.
Ed., 2012, 51, 2698-2702; f) T. E. Pennington, C. Kardiman and
C. A. Hutton, Tetrahedron Lett. 2004, 45, 6657-6660; g) N. R.
Candeias, F. Montalbano, P. M. S. D. Cal and P. M. P. Gois,
Chem. Rev 2010, 110, 6169-6193; h) M. Tredwell, S. M.
Preshlock, N. J. Taylor, S. Gruber, M. Huiban, J. Passchier, J.
Mercier, C. Génicot and V. Gouverneur, Angew. Chem. Int. Ed.,
2014, 53, 7751-7755.
a) H. He, W.-B. Liu, L.-X. Dai and S.-L. You, J. Am. Chem. Soc.,
2009, 131, 8346-8347; b) L. Ilies, S. Asako and E. Nakamura, J.
Am. Chem. Soc., 2011, 133, 7672-7675; c) Y.-H. Xu, Y. K. Chok
and T.-P. Loh, Chem. Sci., 2011, 2, 1822-1825; d) C. Feng and
T.-P. Loh, Angew. Chem. Int. Ed., 2013, 52, 12414-12417; e) N.
Kuhl, N. Schröder and F. Glorius, Org. Lett., 2013, 15, 3860-
3863; f) B. Li and P. H. Dixneuf, Chem. Soc. Rev., 2013, 42,
5744-5767; g) X. Shang and Z.-Q. Liu, Chem. Soc. Rev., 2013,
42, 3253-3260; h) A. Seoane, N. Casanova, N. Quiñones, J. L.
Mascareñas and M. Gulías, J. Am. Chem. Soc., 2014, 136, 834-
837; i) K. D. Collins, F. Lied and F. Glorius, Chem. Commun.,
2014, 50, 4459-4461; j) T. Piou and T. Rovis, J. Am. Chem. Soc.,
2014, 136, 11292-11295; k) L.-B. Zhang, X.-Q. Hao, S.-K. Zhang,
Z.-J. Liu, X.-X. Zheng, J.-F. Gong, J.-L. Niu and M.-P. Song,
Angew. Chem. Int. Ed., 2015, 54, 272-275.
a) T. Besset, N. Kuhl, F. W. Patureau, and F. Glorius, Chem. Eur.
J. 2011, 17, 7167-7171; b) A.Grabulosa, G. Muller, J. I. Ordinas,
A. Mezzetti, M. A. a) M. J. Burk, J. G. Allen, W. F. Kiesman, J.
Am. Chem. Soc. 1998, 120, 657-663; c) M. J. Burk, J. G. Allen,
W. F. Kiesman, K. M. Stoffan, Tetrahedron Lett. 1997, 38,
1309-1312; d) X.-H. Hu, J. Zhang, X.-F. Yang, Y.-H. Xu, and
Teck-Peng Loh, J. Am. Chem. Soc. 2015, 137, 3169−3172
a) G. J. Irvine, M. J. G. Lesley, T. B. Marder, N. C. Norman, C. R.
Rice, E. G. Robins, W. R. Roper, G. R. Whittell and L. J. Wright,
Chem. Rev., 1998, 98, 2685-2722; b) I. Beletskaya and C.
Moberg, Chem. Rev., 2006, 106, 2320-2354.
a) J. Yun, Asian J. Org. Chem., 2013, 2, 1016-1025; b) Y. D.
Bidal; F. Lazreg; C. S. J. Cazin, ACS Catal., 2014, 4, 1564-1569;
c) J. Zhao, Z. Niu, H. Fu and Y. Li, Chem. Commun., 2014, 50,
2058-2060; d) C. Gunanathan, M. Hölscher, F. Pan and W.
Leitner, J. Am. Chem. Soc., 2012, 134, 14349-14352; e) M.
Haberberger and S. Enthaler, Chem. Asian J., 2013, 8, 50-54.
J.-E. Lee, J. Kwon and J. Yun, Chem. Commun., 2008, (6), 733-
734.
4
In addition, the reactions between phenylacetylene and
bis(pinacolato)diboron were also performed according to the
precedent literatures [Eqs. (1)-(2)] and under the present conditions
[Eqs. (3)]. It is clearly demonstrated that alkynyl carboxylic acids
play indispensible roles on the success of this transformation.
Conclusions
5
In conclusion, we have developed a copper-catalyzed highly
efficient protocol for the synthesis of bis-deuterated β-borylated α,
β-styrene derivatives from alkynyl acids with bis(pinacolato)diboron
at ambient temperature. Readily available and cheap D2O was
employed as the deuterium source, and alkynyl acids play a pivotal
role in this protocol. Owing to potential applications of bis-
deuterated β-borylated α, β-styrene derivatives in organic
chemistry, this protocol has potential in the development of
preparation of isotopically labeled compounds. Moreover, this
reaction offers an efficient strategy to highly selective
trifunctionalization of carbon-carbon triple bond at ambient
temperature, which may open a door for organic chemists to
explore further trifunctionalization of carbon-carbon triple bonds.
Acknowledgement
Financial support from the National Natural Science Foundation of
China (21202049), the Recruitment Program of Global Experts
(1000 Talents Plan), Fujian Hundred Talents Program and Program
of Innovative Research Team of Huaqiao University (Z14X0047) are
grateful acknowledged. We also thank Prof. Zhenhua Gu from USTC
(University of Science and Technology of China) for generous
instrumental (HRMS) support.
6
7
8
9
a) Q. Song, Q. Feng and M. Zhou, Org Lett., 2013, 15, 5990-
5993; b) Q. Song; Q. Feng and K. Yang, Org. Lett., 2014, 16,
624-627; c) Q. Feng and Q. Song, Adv. Synth. Catal., 2014, 356,
1697-1702; (d) Q. Feng and Q. Song, J. Org. Chem., 2014, 79,
1867-1871.
10 a) D. Zhao, C. Gao, X. Su, Y. He, J. You and Y. Xue, Chem.
Commun., 2010, 46, 9049-9051; b) W. Jia and N. Jiao, Org.
Lett., 2010, 12, 2000-2003; c) D. L. Priebbenow, P. Becker and
C. Bolm, Org. Lett., 2013, 15, 6155-6157; d) X. Li, F. Yang, Y.
Wu and Y. Wu, Org. Lett., 2014, 16, 992-995.
11 a) K. Takahashi, T. Ishiyama and N. Miyaura, J. Organomet.
Chem. 2001, 625, 47-53; b) H. Ito, C. Kawakami and M.
Sawamura, J. Am. Chem. Soc. 2005, 127, 16034-16035; c) D. S.
Laitar, P. Müller and J. P. Sadighi, J. Am. Chem. Soc., 2005, 127,
17196-17197; d) D. S. Laitar, E. Y. Tsui and J. P. Sadighi,
Organometallics, 2006, 25, 2405-2408; e) S. Mun, J.-E. Lee and
J. Yun, Org. Lett., 2006, 8, 4887-4889.
12 L. Zhang, J. Cheng, B. Carry and Z. Hou, J. Am. Chem. Soc.,
2012, 134, 14314-14317.
13 K. Jouvin, J. Heimburger and G. Evano, Chem. Sci., 2012, 3,
756-760.
14 R. Shang, Z. Huang, L. Chu, Y. Fu and L. Liu, Org. Lett., 2011, 13,
4240-4243.
Notes and references
1
a) J. M. Brown and D. Parker, Organometallics, 1982, 1, 950-
956; b) W. Leitner, J. M. Brown and H. Brunner, J. Am. Chem.
Soc., 1993, 115, 152-159; c) G. C. Lloyd-Jones, S. W. Krska, D. L.
Hughes, L. Gouriou, V. D. Bonnet, K. Jack, Y. Sun and R. A.
Reamer, J. Am. Chem. Soc., 2004, 126, 702-703; d) L. A. Evans,
N. Fey, G. C. Lloyd-Jones, M. P. Muñoz and P. A. Slatford,
Angew. Chem. Int. Ed., 2009, 48, 6262-6265; e) R. E. McKinney
Brooner and R. A. Widenhoefer, Chem. Eur. J., 2011, 17, 6170-
6178.
2
3
a) B. Carboni and L. Monnier, Tetrahedron 1999, 55, 1197-
1248. b) Suzuki, A. Rev. Heteroatom Chem., 1997, 17, 271−314.
a) G. A. Molander and N. M. Ellis, J. Org. Chem., 2008, 73,
6841-6844; b) H. C. Brown, T. Hamaoka and N. Ravindran, J.
Am. Chem. Soc., 1973, 95, 5786-5788; c) R. E. Shade, A. M.
Hyde, J.-C. Olsen and C. A. Merlic, J. Am. Chem. Soc., 2010,
132, 1202-1203; d) C.-Z. Tao, X. Cui, J. Li, A.-X. Liu, L. Liu and
Q.-X. Guo, Tetrahedron Lett., 2007, 48, 3525-3529; e) P. J. Riss,
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins