Copper-catalyzed cascade annulation between α-bromocarbonyls and biaryl or (: Z)-arylvinylacetylenes enabling a direct synthesis of dibenzocycloheptanes and related compounds

Article abstract of DOI:10.1039/c6cc07727g

Copper-catalyzed cascade annulation of γ,δ-unsaturated α-bromocarbonyls with biaryl or (Z)-arylvinylacetylenes is presented, giving an expeditious access to dibenzocycloheptanes and related compounds in moderate to high yields. It provides a novel method for the one-pot synthesis of cycloheptane and cycloheptene-fused polycyclic scaffolds featuring a rare 7-endo-trig radical cyclization.

Full text of DOI:10.1039/c6cc07727g

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: D. Lu, Y. Wan, L.
Kong and G. Zhu, Chem. Commun., 2016, DOI: 10.1039/C6CC07727G.
This is an Accepted Manuscript, which has been through the
Volume 52 Number
1 4 January 2016 Pages 1–216
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
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
author guidelines.
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, outlined
in our author and reviewer resource centre, 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.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
ChemComm
Page 1 of 4
View Article Online
DOI: 10.1039/C6CC07727G
Journal Name
COMMUNICATION
Copper-catalyzed cascade annulation between α-bromocarbonyls
and biaryl or (Z)-arylvinylacetylenes enabling a direct synthesis of
dibenzocycloheptanes and related compounds
Received 00th January 20xx,
Accepted 00th January 20xx
Danyang Lu,a Yimei Wan,a Lichun Kong,a and Gangguo Zhua,*
DOI: 10.1039/x0xx00000x
www.rsc.org/
A copper-catalyzed cascade annulation of γ,δ-unsaturated α- diastereoselective construction of multiply functionalized
bromocarbonyls with biaryl or (Z)-arylvinylacetylenes is presented, dibenzocycloheptanes via an elegant radical cascade reaction of
giving an expeditious access to dibenzocycloheptanes and related ortho-vinylaryl-substituted N-(arylsulfonyl)-acrylamides has been
compounds in moderate to high yields. It provides a novel method accomplished by the group of Nevado (Scheme 2c).5,6 Despite these
for the one-pot synthesis of cycloheptane and cycloheptene-fused impressive advances, the straightforward and general assembly of
polycyclic scaffolds featuring a rare 7-endo-trig radical cyclization.
dibenzocycloheptanes and related compounds is highly desirable in
the fields of both synthetic and medicinal chemistry.
(a) oxidative biaryl coupling3
Seven-membered rings bearing benzoannulated motifs are
extensively distributed in various bioactive molecules, natural
products, and even versatile ligands.1 Among these, colchicine is a
natural tubulin binding agent that can be used for treatment of
familial Mediterranean fever and acute gout. However, the
potential toxicity of colchicine for cancer therapy limits its
pharmaceutical application, therefore posing a highly demand for
the synthesis of structural analogues, such as allocolchicine, N-
acetylcolchinol, and others (Scheme 1).2 As such, access to
dibenzocycloheptane derivatives is of significant importance.
R1
R1
R2
MoCl5/TiCl4,
Tl(OCOCF3)3,
PhI(OCOCF3)2,
or Pb(OAc)4
R3
R3
R2
(b) C-H/C-X biaryl coupling4
R3
R3
R5
R1
R2
R1
PdLn, base
X
R4
R4
R2
R5
(c) Nevado's work5
N3
OMe
OH
Cl
MeO2C
I
MeO
HO
O
H
O
H2N
NC
N
Ar
OH
NHAr
N
S
O
MeO
O
O
O
O
MeO
MeO
H
or AgNO3, HP(O)R2
NHAc
N3/P(O)R2
HO
OH
O2N
OMe
R
OH
(d) this work
allocolchicine (R = CO2Me) metasequirin-B cyclopropylallocolchicinoid antitumor active
Z
Z
Y
N-acetylcolchinol (R = OH)
Cu(MeCN)4PF6
bpy, Na2CO3
Y
E
E
R
+
PhMe, 110 o
C
Br
Scheme 1 Selected examples of dibenzocycloheptane and its analogues.
E
E
R
Y
Y
In this respect, the oxidative coupling3 of 1,3-diaryl propanes or
propenes, mediated by MoCl5/TiCl4,3a,3b Tl(OCOCF3)3,3c Pb(OAc)4,3d
or PhI(OCOCF3)2,3e respectively, has emerged as a straightforward
method for the construction of these skeletons (Scheme 2a).3
However, the utilization of stoichiometric or excess amount of
environmentally unfriendly strong oxidants leaves ample room for
improvement. Alternatively, the Pd-catalyzed intramolecular
C−H/C−X (X = halide) biaryl coupling stands out as an effective
strategy for assembling these motifs (Scheme 2b).4 Recently, a
Y = CH=CH, S; Z = C, N; E = CO2R', Ac
Scheme Representative methods for the one-pot synthesis of
dibenzocycloheptane derivatives.
2
Pursuing our recent interest on the Cu-catalyzed radical
reactions,7 we would like to communicate here a novel, fast, and
modular synthesis of dibenzocycloheptanes and related compounds
via
a
Cu-catalyzed radical cascade annulation between γ,δ-
α-bromocarbonyls8,9
and biaryl or (Z)-
unsaturated
arylvinylacetylenes, in which three C-C bonds and two new rings
can be assembled in a single chemical transformation (Scheme 2d).
a.Department of Chemistry, Zhejiang Normal University, 688 Yingbin Road, Jinhua
321004, P. R. China. E-mail: gangguo@zjnu.cn
It represents
a new advance in the one-pot synthesis of
cycloheptane and cycloheptene-fused polycyclic compounds
featuring a rare regiospecific 7-endo alkyl radical cyclization.10
Electronic Supplementary Information (ESI) available: Experimental details and
spectra of all products. See DOI: 10.1039/x0xx00000x
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/C6CC07727G
COMMUNICATION
Journal Name
We initiated our investigation by evaluating the reaction and a wide range of functional groups such as Me, OMe, F, Cl, Ac,
between biarylacetylene 1a and α-bromocarbonyl 2a. Initially, CuI CO2Me, CF3, and OH were well tolerated. Of note, the electronic
(10 mol%) was utilized as the catalyst with 2,2'-bipyridine (L1, 20 properties of the benzene ring of 1 appeared to have little effect on
mol%) as the supporting ligand and Na2CO3 (2 equiv) as the base. the reaction, as demonstrated by the comparable yields of 3ca and
After refluxing in toluene for 12 h, 3aa was obtained in 45% yield 3fa-3ha. Substitution of the benzene ring of 1 with alkynyl or
(Table 1, entry 1). Encouraged by this promising result, we further alkenyl groups was also accommodated, albeit in somewhat
examined an array of copper reagents, and specifically, reduced efficiency (3ja and 3ka). The steric hindrance seemed to
Cu(MeCN)4PF6 turned out to be the most effective catalyst and have impact on the site selectivity of annulation, as exemplified by
produced 3aa in 82% yield (entries 1-5). As for the ligand, switching the production of a pair of isomers 3la and 3la' in a 2.3:1 ratio.
from L1 to diamines L2 and L3, triamine L4, or tetraamine L5 led to
Table 2. Scope of the alkyne componenta
decreased reaction efficiency (entries 6-9). Furthermore, variation
of the base, solvent and catalyst/ligand ratio had no beneficial
influence on the transformation (entries 10-18). The control
experiments indicated that both 2,2'-bipyridine (L1) and Na2CO3
were crucial for the reaction (entries 19 and 20).
Cu(MeCN)4PF6 (10 mol%)
L1
Z
Y
Z
Y
(20 mol%)
Na2CO3 (2 equiv)
E
2a
E
+
PhMe, 110 o
C
Br
E
E
Y
Y
1
3
Cl
Me
OMe
F
Table 1. Evaluation of reaction conditionsa
E
E
E
E
E
E
E
E
3ea, 73%
3ba, 65%
Ac
3ca, 73%
CO2Me
3da, 71%
CF3
Ph
E
E
E
E
E
E
E
E
3ha, 76%
3ia, 77%
3fa, 70%
Ph
3ga, 70%
Entry
1
[Cu]
Ligand
L1
Base
Solvent
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhMe
PhCF3
MeCN
DMF
Yield (%)
45
Ph
Me
Me
CuI
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
K2CO3
2
CuBr
CuBr2
Cu(OTf)2
L1
42
+
3
L1
48
E
E
E
E
E
E
E
E
4
L1
72
3la
3la'
5
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L2
Cu(MeCN)4PF6 L3
Cu(MeCN)4PF6 L4
Cu(MeCN)4PF6 L5
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
82
77% (3la:3la' = 2.3:1)
3ja, 52%
3ka, 57%
6
31
7
Trace
61
8
9
23
E
E
E
E
3ma, 70%
E
E
E
10
11
12
13
14
15
16
17b
18c
19
20
21d
75
E
EtO2C
Cl
3pa, 80%
3na, 78%
3oa, 77%
Cs2CO3
K3PO4
28
69
N
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
/
51
S
S
42
46
E
E
E
E
E
E
E
E
THF
40
Ac
3qa, 72%
3ta, 81%
3ra, 70%
3sa, 80%
PhMe
PhMe
PhMe
PhMe
PhMe
73
Ph
78
S
Cu(MeCN)4PF6
/
Trace
15
E
E
E
E
E
Cu(MeCN)4PF6 L1
Cu(MeCN)4PF6 L1
E
S
HO
1x
1y
Na2CO3
65
3ua, 42%
3va, 88%
3wa, 74%
a Reaction conditions: 1a (0.25 mmol), 2a (0.30 mmol), [Cu] (10 mol%), ligand (20
a Reaction conditions: 1 (0.25 mmol), 2a (0.30 mmol), Cu(MeCN)4PF6 (10 mol%),
L1 (20 mol%), base (0.50 mmol), PhMe (5 mL), 110 oC, 12 h. Yields of the isolated
products are given. E = CO2Et.
mol%), base (0.50 mmol), solvent (5 mL), 110 oC, 12 h. Yields of the isolated
c
d
products are given. b Ligand (10 mol%) was used. Ligand (30 mol%) was used.
[Cu] (5 mol%) was used.
Interestingly, the Cu-catalyzed cascade annulation of 1m gave
rise to 3ma as the sole product, and the structure was assigned by
Having found the optimized reaction conditions, efforts were
invested in exploring the scope of this reaction with respect to the
alkyne component, and the results are summarized in Table 2. The the single crystal X-ray analysis.11 Formation of a more stable
radical intermediate, caused by the resonance interaction, may be
functional-group compatibility was found to be quite satisfactory,
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/C6CC07727G
Journal Name
COMMUNICATION
responsible for the selective α-alkylation of naphthalene.12 Alkynes
To unveil the reaction pathway, the reaction of 1a and 2a was
bearing heterocycle substituents, such as thiophene (1r and 1u), conducted with the addition of electron-transfer scavenger 1,4-
benzo[b]thiophene (1s), and pyridine (1t), were also explored as dinitrobenzene (2 equiv), and consequently, a significant decrease
coupling partners, affording the desired products 3ra-3ua in of the yield (<10%) was observed (not shown). Furthermore,
moderate to high yields. In addition to biarylacetylenes, it was performing the reaction in the presence of 2 equiv of radical
possible to extend this protocol to include (Z)-arylvinylacetylenes. scavenger butylated hydroxytoluene (BHT), 3aa was not formed and
For instance, an excellent yield was observed for the transformation compound 4 was obtained in 81% yield (eq 1). Replacing BHT with
of 1v (3va). The reaction of 1w, a substrate with free hydroxyl either 2,2,6,6-tetramethylpiperidinooxy (TEMPO) or 1,1-
group, resulted in the production of tricyclic alcohol 3wa in 74% diphenylethylene also inhibited the formation of 3aa (not shown).
yield. In contrast, either but-3-yn-1-ylbenzene (1x) or (E)-1-ethynyl- Hence, a radical reaction pathway has been proposed in Scheme 3
2-styrylbenzene (1y) failed to provide the expected products under using 1a and 2a as representative starting materials. Initially, a
the reaction conditions.
single electron transfer (SET) from Cu(I) species to 2a affords the
Cu(II) complex and radical I, followed by an intermolecular addition
of the C-C triple bond of 1a to produce an alkenyl radical II. Then, a
Table 3. Scope of α-bromocarbonylsa
5-exo-trig cyclization and
a subsequent 7-endo-trig radical
cyclization forms a new carbon radical IV. Indeed, the observation
of by-product 3ac' supports the formation of intermediate III.
Oxidation of IV by Cu(II) species via another SET affords the cationic
intermediate V along with the generation of Cu(I) catalyst for the
next catalytic cycle. Lastly, Na2CO3-assisted deprotonation gives 3aa
as the corresponding product.
a Reaction conditions: 1a (0.25 mmol), 2 (0.30 mmol), Cu(MeCN)4PF6 (10 mol%),
L1 (20 mol%), base (0.50 mmol), PhMe (5 mL), 110 oC, 12 h. Yields of the isolated
products are given. b Cis/trans = 6.7:1 c dr = 1.4:1.
Meanwhile, α-bromocarbonyl compounds were also varied, and
the results are summarized in Table 3. Introduction of a phenyl
group at the C5 position of 2 produced 3ab in 70% yield favoring
the cis-diastereomer (cis/trans = 6.7:1). Substitution of the C-C
double bond of 2 by alkyl groups was not successful, due to the
formation of atom-transfer radical cyclization (ATRC)13 products 3'.
For example, in the case of 2c, the ATRC product 3ac' was isolated
in 72% yield. Installation of a methyl group at the C4 position of 2
had no unfavorable effect on the reaction, leading to a facile
synthesis of quaternary-carbon-containing product 3ad, whose
structure was ascertained by the X-ray crystallography.11 Notably,
alkynyl α-bromocarbonyls were also efficiently transformed,
producing cycloheptene-fused tetracyclic compounds 3ae-3ag in
reasonable yields. Under the standard reaction conditions, both 2i
and 2j proved to be viable substrates to provide 3ai and 3aj in 70%
and 58% yield, respectively. Unfortunately, 2k was incompatible for
this transformation.
Scheme 3 A possible mechanism.
Scheme 4 Synthetic utility of method.
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/C6CC07727G
COMMUNICATION
Journal Name
2007,
Wulff and H.-J. Hansen, J. Org. Chem., 2003, 68, 5826; (d) F.-
D. Boyer, X. L. Goff and I. Hanna, J. Org. Chem., 2008, 73
5163; (e) N. Sitnikov, J. Velder, L. Abodo, N. Cuvelier, J.
Neudörfl, A. Prokop, G. Krause, A. Y. Fedorov and H.-G.
Schmalz, Chem. Eur. J., 2012, 18, 12096; (f) A. A. More and C.
V. Ramana, J. Org. Chem., 2016, 81, 3400.
(a) C. Che, H. Zheng and G. Zhu, Org. Lett., 2015, 17, 1617; (b)
C. Che, Q. Huang, H. Zheng and G. Zhu, Chem. Sci., 2016, 7,
4134; (c) H. Zhu, X. Nie, Q. Huang and G. Zhu, Tetrahedron
Lett., 2016, 57, 2331; (d) C. Cheng, S. Liu, D. Lu and G. Zhu,
Org. Lett., 2016, 18, 2852.
For Cu-catalyzed radical addition of α-bromocarbonyls to
alkynes, see: (a) T. Xu and X. Hu, Angew. Chem., Int. Ed.,
2015, 54, 1307; (b) M.-C. Belhomme, D. Dru, H.-Y. Xiong, D.
Cahard, T. Besset, T. Poisson and X. Pannecoucke, Synthesis,
2014, 1859; for Cu-catalyzed radical addition of α-
bromocarbonyls to alkenes, see: (c) M. Pirtsch, S. Paria, T.
9, 5505; (c) A. V. Vorogushin, A. V. Predeus, W. D.
Afterward, we set about assessing the synthetic utility of this Cu-
catalyzed radical cascade annulation reaction (Scheme 4). As a
result, allylic alcohol 5a was isolated in 70% yield upon treatment of
3aa with 1.1 equiv of NBS in THF/H2O (v/v = 3:1) at ambient
temperature. By using the tetrabutylammonium iodide catalyzed
ester formation protocol, developed by Wan and co-workers,14 the
allylic ester 5b was successfully synthesized in 66% yield. Subjection
of 3aa to the epoxidation conditions (meta-chloroperbenzoic acid,
1.2 equiv) furnished epoxide 5c as the single diastereomer in 85%
yield.11 In addition, the decarbalkoxylation of 3aa provided 3ah in
76% yield with a good diastereoselectivity (dr = 87:13).
,
7
8
In conclusion, a novel Cu-catalyzed cascade annulation between
γ,δ-unsaturated
α-bromocarbonyls
and
biaryl
or
(Z)-
arylvinylacetylenes has been achieved, giving a straightforward and
modular access to dibenzocycloheptanes and related compounds in
satisfactory yields. A broad selection of functional groups including
OMe, OTHP, F, Cl, Ac, CO2Me, CF3, OH, thienyl, pyridyl, alkenyl, and
alkynyl substituents are well compatible for the current reaction.
This reaction constitutes one of the rare examples on the one-pot
synthesis of cycloheptane or cycloheptene-fused polycyclic
scaffolds featuring a 7-endo alkyl radical cyclization.
Matsuno, H. Isobe and O. Reiser, Chem. Eur. J., 2012, 18
7336; (d) M. Knorn, T. Rawner, R. Czerwieniec and O. Reiser,
ACS Catal., 2015, , 5186; (e) T. Nishikata, Y. Noda, R.
Fujimoto and T. Sakashita, J. Am. Chem. Soc., 2013, 135
16372; (f) T. Nishikata, Y. Noda, R. Fujimoto and S. Ishikawa,
Chem. Commun., 2015, 51, 12843; (g) X. Zhang, H. Yi, Z. Liao,
G. Zhang, C. Fan, C. Qin, J. Liu and A. Lei, Org. Biomol. Chem.,
2014, 12, 6790; (h) J. O. Metzger and R. Mahler, Angew.
Chem., Int. Ed., 1995, 34, 902.
,
5
,
9
For other catalytic versions of α-halocarbonyls, see: (a) H.
Yorimitsu, T. Nakamura, H. Shinokubo, K. Oshima, K. Omoto
and H. Fujimoto, J. Am. Chem. Soc., 2000, 122, 11041; (b) Y.
We thank the National Natural Science Foundation of China
(21672191) and Science Technology Department of Zhejiang
Province (2015C31030) for financial support.
Tang and C. Li, Org. Lett., 2004, 6, 3229; (c) J. D. Nguyen, J.
W. Tucker, M. D. Konieczynska and C. R. J. Stephenson, J.
Am. Chem. Soc., 2011, 133, 4160; (d) C.-J. Wallentin, J. D.
Nguyen, P. Finkbeiner and C. R. J. Stephenson, J. Am. Chem.
Soc., 2012, 134, 8875; (e) Q. Liu, H. Yi, J. Liu, Y. Yang, X.
Zhang, Z. Zeng and A. Lei, Chem. Eur. J., 2013, 19, 5120; (f) T.
Xu, C. W. Cheung and X. Hu, Angew. Chem., Int. Ed., 2014,
53, 4910; (g) J.-H. Fan, W.-T. Wei, M.-B. Zhou, R.-J. Song and
J.-H. Li, Angew. Chem., Int. Ed., 2014, 53, 6650; (h) E. Arceo,
E. Montroni and P. Melchiorre, Angew. Chem., Int. Ed., 2014,
53, 12064; (i) B. Hu, H. Chen, Y. Liu, W. Dong, K. Ren, X. Xie,
H. Xu and Z. Zhang, Chem. Commun., 2014, 50, 13547.
Notes and references
1
(a) A.-G. E. Amr, A. M. Mohamed, S. F. Mohamed, N. A.
Abdel-Hafez and A. E.-F. G. Hammam, Bioorg. Med. Chem.,
2006, 14, 5481; (b) Y. Uruma, K. Sakamoto, K. Takumi, M.
Doe, Y. Usuki and H. Iio, Tetrahedron, 2007, 63, 5548; (c) R. J.
Lin, M. J. Cheng, J. C. Huang, W. L. Lo, Y. T. Yeh, C. M. Yen, C.
M. Lu and C. Y. Chen, J. Nat. Prod., 2009, 1816; (d) Y. Sajja, H.
R. Vulupala, R. Bantu, L. Nagarapu, S. B. Vasamsetti, S.
Kotamraju and J. B. Nanubolu, Bioorg. Med. Chem. Lett.,
2016, 26, 858.
10 (a) E. Lee, J. W. Lim, C. H. Yoon, Y.-s. Sung and Y. K. Kim, J.
Am. Chem. Soc., 1997, 119, 8391; (b) J. Justicia, J. L. Oller-
López, A. G. Campaňa, J. E. Oltra, J. M. Cuerva, E. Buňuel and
D. J. Cárdenas, J. Am. Chem. Soc., 2005, 127, 14911; (c) P.
Chen, L. Cao, W. Tian, X. Wang and C. Li, Chem. Commun.,
2010, 46, 8436.
2
3
For selected reviews, see: (a) T. Graening and H.-G. Schmalz,
Angew. Chem., Int. Ed., 2004, 43, 3230; (b) J. Chen, T. Liu, X.
Dong and Y. Hu, Mini-Rev. Med. Chem., 2009, 9, 1174; (c) N.
S. Sitnikov and A. Y. Fedorov, Russ. Chem. Rev., 2013, 82, 393;
(d) S. Larsson and N. Rønsted, Curr. Top. Med. Chem., 2014,
14, 274.
11 CCDC 1498312 (3ma), 1498313 (3ad), and 1498314 (5c
)
contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from the
For MoCl5/TiCl4-mediated oxidative biaryl coupling, see: (a) B.
Kramer and S. R. Waldvogel, Angew. Chem., Int. Ed., 2004, 43
2446; (b) K. Hackeloer, G. Schnakenburg and S. R. Waldvogel,
Org. Lett., 2011, 13, 916; for a thallium(III)-mediated version,
see: (c) J. S. Sawyer and T. Macdonald, Tetrahedron Lett.,
1988, 28, 4839; for Pb(OAc)4-mediated version, see: (d) M. G.
Banwell, J. N. Lambert, M. F. Mackay and R. J. Greenwood, J.
Chem. Soc., Chem. Commun., 1992, 974; for a PhI(OCOCF3)2-
mediated version, see: (e) T. Takada, M. Arisawa, M. Gyoten,
,
Cambridge
www.ccdc.cam.ac.uk/data_request/cif.
12 The selective formation of 3ma is proposed as follows:
Crystallographic
Data
Center
via
R. Hamada, H. Tohma, and Y. Kita, J. Org. Chem., 1998, 63
,
7698.
(a) M. Leblanc and K. Fagnou, Org. Lett., 2005, 7, 2849; (b)
4
P.-S. Wang, X.-L. Zhou and L.-Z. Gong, Org. Lett., 2014, 16
976.
W. Kong, N. Fuentes, A. García-Domínguez, E. Merino and C.
Nevado, Angew. Chem., Int. Ed., 2015, 54, 2487.
For other selected reports, see: (a) G. Besong, K. Jarowicki, P.
J. Kocienski, E. Sliwinski and F. T. Boyle, Org. Biomol. Chem.,
2006, 4, 2193; (b) S. Djurdjevic and J. R. Green, Org. Lett.,
,
13 (a) A. J. Clark, Chem. Soc. Rev., 2002, 31, 1; (b) M. J. W. Taylor,
W. T. Eckenhoff and T. Pintauer, Dalton Trans., 2010, 39,
11475.
14 E. Shi, Y. Shao, S. Chen, H. Hu, Z. Liu, J. Zhang and X. Wan, Org.
Lett., 2012, 14, 3384.
5
6
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins