Catalytic arylsulfonyl radical-triggered 1,5-enyne-bicyclizations and hydrosulfonylation of α,β-conjugates

Article abstract of DOI:10.1039/c5sc02343b

A catalytic bicyclization reaction of 1,5-enynes anchored by α,β-conjugates with arylsulfonyl radicals generated in situ from sulfonyl hydrazides has been established using TBAI (20 mol%) and Cu(OAc)₂ (5 mol%) as co-catalysts under convenient c

Full text of DOI:10.1039/c5sc02343b

View Article Online
View Journal
Chemical
Science
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: Z. Chen, S. Liu, G.
Xu, S. Wu, J. Miao, B. Jiang, W. Hao, S. Wang, S. Tu and G. Li, Chem. Sci., 2015, DOI:
1
0.1039/C5SC02343B.
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/chemicalscience

View Article Online
Page 1 of 4
Chemical Science
Dynamic Article Links ►
DOI: 10.1039/C5SC02343B
Journal Name
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
Catalytic arylsulfonyl radical-triggered 1,5-enyne-bicyclizations and
hydrosulfonylation of -conjugates
Zhen-Zhen Chen,a,1 Shuai Liu, Wen-Juan Hao, Ge Xu, Shuo Wu, Jiao-Na Miao, Bo Jiang, * Shu-
a,1
a
a
a
a
a,
a
a,
b,c,
Liang Wang, Shu-Jiang Tu, * and Guigen Li
*
5
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
Catalytic bicyclization reaction of 1,5-enynes anchored by
-conjugates with arylsulfonyl radicals generated in situ
from sulfonyl hydrazides has been established by using TBAI
(20 mol %) and Cu(OAc) (5 mol %) as co-catalysts under
convenient conditions. In addition, the use of benzoyl
peroxide (BPO) as the oxidant and pivalic acid (PivOH) as an
efficiencies with high levels of structural complexity with
reduced generation of wastes. So far, two main methods for 1,5-

6
4
5
enyne cyclizations have been developed through metal catalysis
7
or electrophilic cyclization. However, the radical bicyclization of
1
0
2
1
,5-enynes for generating multi-substituted polycycles has not
been documented well. The literature survey revealed that
sulfonyl radicals can be generated from sulfonyl hydrazides and
8
additive was proven to be necessary for this reaction. The 50 utilized in situ for radical sulfonylation of alkenes. Due to the
importance of sulfonyl-containing compounds in photovoltaic
reactions
occurred
through
5-exo-dig/6-endo-trig
materials, nonlinear optics and in general synthetic and medicinal
1
5
bicyclizations and homolytic aromatic substitution (HAS)
cascade mechanism to give benzo[b]fluorens regioselectively.
Similar catalytic process was developed for the synthesis of -
ketosulfones. These reactions feature readily accessible
starting materials and simple one-pot operation.
9
areas, we envisioned that under the suitable catalytic radical
conditions, the in situ generated sulfonyl radicals would be able
to be invovled in cascade bond-forming events with internal C=C
and C≡C bonds of 1,5-enyne conjugate systems, resulting in 5-
exo-dig/6-endo-trig bicyclizations and homolytic aromatic
substitutions (HAS) (Scheme 2). Herein, we would like to report
preliminary results of this endeavour (Scheme 2).
55
2
2
3
3
0
5
0
5
The search for efficient cyclization reactions, particularly for
those in radical cascade processes, has been actively pursued in
past several decades because they are extremely useful for total
1
synthesis of numerous important targets. These reactions enable
the rapid, reliable and straightforward protocols to create
multicyclic ring systems by using readily available starting
materials with features shown by unparalleled efficiencies, high
functional tolerability and convenient conditions. Among these
cyclization reactions, the majority of efforts have been devoted to
conduct radical ene-cyclization cascades, in which terminal
alkenes were utilized for most cases via either metal-free or
transition-metal-mediated radical processes (scheme 1, eq 1).3
However, the use of internal alkenes as radical acceptors has been
6
6
0
5
Scheme 2 Envisaged new reactivity of 1,5-Enynes
At first, 3-(2-(phenylethynyl)phenyl)-1-(p-tolyl)prop-2-en-1-one
1a was selected as benchmark substrate to investigate the
4
highly challenging (Scheme 1, eq 2) owing to their relatively
low reactivity and larger steric hindrance as compared with their
terminal counterparts.
additions by sulfonyl radicals. With 20 mol
tetrabutylammoniumiodide (TBAI) as the catalyst, the reaction of
substrate 1a with tosylhydrazide 2a was performed in CH CN in
the presence of benzoperoxide (BPO) (4.0 equiv.) as an oxidant at
%
3
o
7
0
C
under air conditions, affording the expected
benzo[b]fluorens 3a, albeit with a low yield of 18% (Table 1,
70
entry 1). Other solvents, such as dichloromethane (DCM), 1,4-
3
dioxane and toluene, were also examined, with CH CN showing
the best performance (entries 2-4). Raising the reaction
o
temperature to 100 C slightly ameliorates the yield of 3a (entry
5). A subsequent investigation of other catalysts was conducted in
Scheme 1 Two modes of radical ene-cyclizations
1
,5-Enynes endowed with extra unsaturated moieties are
75 CH
3
CN. As illustrated in entries 6−8, different types of catalysts
including I , KI, and CuI were employed in the model reaction,
and it turned out that I and KI hardly facilitate the reaction
privileged building blocks, and have been widely serving for
direct and selective tandem cyclizations via synergistic additions
across C=C and C≡C bonds in a one-step operation.5 These
cyclizations would enhance both bond formation and annulation
2
4
0
2
(entries 6 and 7), while CuI as a catalyst only led to a poor yield
of 16%. Next, we turned our attention to evaluating different
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 1

View Article Online
DOI: 10.1039/C5SC02343B
Chemical Science
Page 2 of 4
additives (entries 9−11). we found that the addition of PivOH (1.0
equiv) delivered 3a in 35% yield (entry 11). Notably, the reaction
of 1a and 2a in the presence of 2.0 equiv of PivOH gave 3a in
unprecedented pentacyclic indeno[2,1-b]phenanthren-7-ols 3n in
67% chemical yield though sulfonyl radicals triggered 1,5-enyne-
bicyclization. Unfortunately, a bulky ortho-Br substituent and
7
1% yield by using co-catalyst of TBAI (20 mol %) and 40 benzylsulfonyl hydrazide did not work at all (3o and 3p). Besides
5
Cu(OAc) (5 mol %) with complete consumption of the starting the NMR and HR-MS spectroscopic analysis for
2
material 1a (entry 15). Without PivOH, the yield of expected
product 3a decreased remarkably (entry 17). Further screening of
other oxidants, such as TBHP (64% yield), DTBP (very poor
benzo[b]fluorens 3, the X-ray diffraction for this product has
been perfomed as shown in Figure 1.
Scheme 3. Substrate scope of hydrosulfonylation reaction
2 2
yield) and H O (no product) for this transformation showed that
1
0
BPO was the best choice (See supporting information).
a
Table 1 Optimization of the reaction conditions
o
b
Entry Catalyst
mol%)
Additives
(equiv)
Solvent
T ( C) Yield
(%)
(
1
2
3
4
5
6
7
8
9
1
TBAI (20)
TBAI (20)
TBAI (20)
TBAI (20)
TBAI (20)
-
-
-
-
-
-
-
-
MeCN
DCM
1,4-Dioxane 70
Toluene
MeCN
MeCN
MeCN
MeCN
MeCN
70
70
18
10
trace
0
70
100
100
100
100
100
100
100
100
25
I
2
(15)
messy
messy
16
28
33
KI (20)
CuI (20)
TBAI (20)
TBAI (20)
TBAI (20)
TBAI (20)/
CuI (5)
HOAc (1.0)
L-proline (1.0) MeCN
PivOH (1.0)
PivOH (1.0)
0
1
1
MeCN
MeCN
35
49
1
1
1
1
1
2
3
4
5
6
7
TBAI (30)/
PivOH (1.0)
PivOH (1.0)
PivOH (2.0)
PivOH (2.0)
-
MeCN
MeCN
MeCN
MeCN
MeCN
100
100
100
100
100
53
61
71
63
33
Cu(OAc)
TBAI (20)/
Cu(OAc) (5)
TBAI (20)/
Cu(OAc) (5)
TBAI (20)/
Cu(OAc) (10)
TBAI (20)/
Cu(OAc) (5)
2
(5)
2
45
a
Reaction conditions: 1,5-conjugated enyne (1, 0.25 mmol), sulfonyl
2
hydrazide (2, 0.50 mmol), TBAI (0.05 mmol), Cu(OAc) (0.0125 mmol),
2
o
PivOH (0.50 mmol), BPO (1.0 mmol), CH CN (2.5 mL), 100 C, 12 h.
3
b
2
Isolated yields based on 1.
1
2
a
Reaction conditions: 1,5-conjugated enyne (1a, 0.25 mmol),
tosylhydrazide (2a, 0.50 mmol), BPO (1.0 mmol), solvent (2.5 mL), 12
b
h. Isolated yields based on 1.
With the optimized reaction conditions in hand, we examined the
substrate scope of sulfonyl hydrazide 2 by treating them with 1,5-
enynes 1a (Scheme 3). As anticipated, the substituents on the
phenyl ring of arylsulfonyl hydrazide 2 did not hamper the
catalytic process, but affected the reaction efficiency. Reactions
of methyl- or bromo, t-butyl-substituted arylsulfonyl hydrazide 2
with 1a afforded the desired products in moderate to good yields.
Besides, benzenesulfonohydrazide exhibited higher reactivity,
allowing 1,5-enyne-bicyclization cascades toward the formation
of benzo[b]fluorens 3c in 84% yield. 1,5-Enynes bearing an
electron-donating or electron-withdrawing group (methoxy and
1
2
2
5
0
5
5
5
0
5
Figure 1. The ORTEP Drawing of 3f
In view of our success with the synthesis of functional
benzo[b]fluorens 3, we reasoned that in the absence of alkyne
moieties, chalcone 4 would be able to accept sulfonyl radicals via
typical 1,4-additions, which can expand its utility for synthesizing
1
chloro) at the para position of the aromatic ring (Ar ) directly
bound to the C≡C bond gave the corresponding sulfonated
products 3e-f in 55% and 68% yields, respectively. Alternatively,
naphthalen-1-yl substituents linked to the C≡C bond was also
well-tolerated, affording the product 3g in 60% chemical yield.
Similarly, either electron-donating (methyl) or electron-

-ketosulfones. We thus explored this feasibility through a one-
pot reaction of (4-chlorophenyl)-3-phenylprop-2-en-1-one (4a)
with 2a under the conditions described above. The expected -
ketosulfones 5a was obtained but with a lower yield (15%)
intially. After careful optimizations were performed, we found
3
0
1
withdrawing (bromo) group (R ) at para position of phenyl ring
6
0
tethered to enone unit were well-suited for this radical 1,5-enyne-
bicyclizations (3a-3k). 1,5-Enynes 1 carrying electron-neutral
groups was also smoothly converted into the corresponding
sulfonated benzo[b]fluorens 3l-3n in 39%-67% yields. Notably,
that although Cu(OAc)
process, the use of co-oxidants of BPO (2.0 equiv.) and TBHP
1.0 equiv., 70% in water) in the 20 mol% of TBAI proved to be
2
and PivOH did promote this catalytic
(
3
5
suitable for the current hydrosulfonylation, furnishing product 5a
2
-naphthalenylethanone-derived 1,5-enynes furnished the
2
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

View Article Online
DOI: 10.1039/C5SC02343B
Page 3 of 4
Chemical Science
in 77% yield. Subsequently, we further studied the reaction scope
reation did not show the desired product (eq 2). To further
confirm the sulfonylation sequence, subjecting 1,5-enynes 1h to
the standard condition in the absence of 2a failed to generate any
desired benzo[b]fluoren product 5 (eq 3). These controlled
experiments suggest that BPO is essential for the catalytic cycles
and in situ generated sulfonyl radical triggers a 5-exo-dig/6-endo-
trig bicyclization cascades.
by reacting arylsulfonyl hydrazides 2 with various chalcones 4
under this condition (Scheme 4). It turned out that the presence of
various substituents, including methoxyl, methyl, chloro and
bromo groups, on the aryl rings of chalcones all worked well,
giving access to a wide range of -ketosulfones 5a-5o with yields
ranging from 50% to 90%. Alternatively, arylsulfonyl hydrazides
3
4
4
5
5
5
0
5
0
5
5
0
5
2
carrying either electronically neutral or rich groups can be
On the basis of the above observations and those reported in
successfully engaged in this catalysis. Unfortunately, aliphatic
sulfonyl hydrazide (5p) was proven not to be adaptable substrates
for this reaction, which may be ascribed to the relative instability
of the sulfonyl radicals generated in situ from aliphatic sulfonyl
hydrazides. Joining previously reported work,10 this catalytic
radical addition provided a new protocol for the formation of -
ketosulfones, which are important building blocks in organic
synthesis.
8
,11
1
literature,
a mechanism is proposed and shown in Scheme 6.
The first step is to form the sulfonyl radical A from sulfonyl
hydrazides by benzoyloxy radical generated in situ from the I
anion-assisted the decomposition of BPO. The intermolecular
addition of the resulting sulfonyl radical A onto 1,5-conjugated
enynes 1 followed by 5-exo-dig cyclization gives intermediate B,
in which the homolysis of carbon-copper(III) affords vinyl radical
C. Intermediate C is converted into aryl radical D via 6-endo-trig
cyclization. Intermediate D undergoes SET (single electron
transfer) oxidation and subsequent deprotonation to provide
intermediate F. The tautomerization of F leads to the formation
of benzo[b]fluorens 3. Although the generation of sulfonyl
1
Scheme 4 Substrate scope of the synthesis of -ketosulfones
8
radicals triggered by various oxidants has been achieved well,
1
2
the bicyclizations towards fused carbocycles via sulfonyl
radical initiated bifunctionalizations of enynes is very rare in
organic chemistry as mentioned earlier.
a
Reaction conditions: chalcone (4, 0.25 mmol), sulfonyl hydrazide (2,
2
0
0.50 mmol), TBAI (0.05 mmol), BPO (0.50 mmol), TBHP (0.25 mmol,
o
b
7
3
0% in water), CH CN (2.5 mL), 100 C, 6 h. Isolated yields based on 4.
Scheme 6. Proposed mechanism for forming products 3
Conclusions
6
6
7
0
5
0
In summary, we have discovered new 1,5-enyne-bicyclization and
hydrosulfonylation reactions of -conjugates under convenient
co-catalytic conditions. The addition of in situ generated sulfonyl
radicals onto the activated double bond is able to trigger a
cascade 5-exo-dig/6-endo-trig bicyclizations and HAS sequence,
a
Reaction conditions: 1,5-conjugated enyne (1h, 0.25 mmol), sulfonyl
(0.0125 mmol),
hydrazide (2h, 0.50 mmol), TBAI (0.05 mmol), Cu(OAc)
PivOH (0.50 mmol), BPO (1.0 mmol), CH CN (2.5 mL), 100 C, 12 h.
3
2
o
2
5
Scheme 5 Controlling reactions
To understand the mechanism, several control experiments were
conducted. The treatment of 1,5-enynes 1h with tosylhydrazide
2
under standard conditions gave complex mixtures without
observation of desired product 3l, confirming the existence of a
radical mechanism (Scheme 5, eq 1). In the absence of BPO, the
delivering tetracyclic sulfonylated benzo[b]fluorens in
a
successive C−S and C−C bond-forming process. Using chalcones
as replacement for 1,5-conjugated enynes, this reaction enables
hydrosulfonylation of alkenes to form -ketosulfones with good
to excellent yields. These two methods allow easy accesses to
important functional sulfones for potential applications in organic
and medicinal chemistry.
a in the presence of radical scavenger TEMPO (4.0 equiv.)
3
0
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

View Article Online
DOI: 10.1039/C5SC02343B
Chemical Science
Page 4 of 4
2
009, 48, 2534. (g) J. Zhang, D. Wu, X. Chen, Y. Liu and Xu, Z. J.
Acknowledgment
7
0
Org. Chem., 2014, 79, 4799. (h) H. Zheng, R. J. Felix and M. R.
Gagne, Org. Lett., 2014, 16, 2272.
(a) F. Huber and S. F. Kirsch, J. Org. Chem., 2013, 78, 2780. (b) A.
Pradal, A. Nasr, P. Y. Toullec and V. Michelet, Org. Lett., 2010, 12,
We are grateful for financial support from the NSFC (No.
7
8
.
.
2
1232004, 21272095, 21472071 and 21332005), PAPD of
Jiangsu Higher Education Institutions, the Qing Lan Project
(12QLG006), Robert A. Welch Foundation (D-1361, USA) and
NIH (R33DA031860, USA), the Outstanding Youth Fund of
Jiangsu Normal University (YQ2015003), and Natural Science
Foundation of Jiangsu Normal University (14XLR005).
5
222. (c) B. Crone, S. F. Kirsch and K.-D. Umland, Angew. Chem.,
5
75
Int. Ed., 2010, 49, 4661.
For selected sulfonyl radicals generated in situ from sulfonyl
hydrazides, see: (a) X. Li, X. Xu and C. Zhou, Chem. Commun.,
2
012, 48, 12240. (b) J. Zhang, Y. Shao, H. Wang, Q. Luo, J. Chen, D.
Xu and X. Wan, Org. Lett., 2014, 16, 3312. (c) X. Li, Y. Xu, W. Wu,
C. Jiang, C. Qi and H. Jiang, Chem.-Eur. J., 2014, 20, 7911. (d) S.
Tang, Y. Wu, W. Liao, R. Bai, C. Liu and A. Lei, Chem. Commun.,
80
Notes and references
2
014, 50, 4496. (e) W. Wei, C. Liu, D. Yang, J. Wen, J. You, Y. Suo
a
1
1
2
0
5
0
Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional
and H. Wang, Chem. Commun., 2013, 49, 10239. (f) T. Taniguchi, Y.
Sugiura, H. Zaimoku and H. Ishibashi, Angew. Chem., Int. Ed., 2010,
49, 10154. (g) G. Rong, J. Mao, H. Yan, Y. Zheng and G. Zhang, J.
Org. Chem., 2015, 80, 4697.
Materials, Jiangsu Normal University, Xuzhou, 211116, P. R. China; e-
mail: jiangchem@jsnu.edu.cn (B. Jiang); laotu@jsnu.edu.cn (S.-J. Tu);
Tel./fax: +8651683500065; Institute of Chemistry
85
90
b
& BioMedical
Sciences, Collaborative Innovation Center of Chemistry for Life Sciences,
School of Chem. and Chem. Eng., Nanjing University, Nanjing 210093,
9. (a) N. Simpkins, In Sulfones in Organic Synthesis; J. E. Baldwin, P.
D. Magnus , Eds.; Pergamon Press: Oxford, 1993. (b) E. Block,
Reaction of Organosulfur Compounds; Academic Press: New York,
1978. (c) P. D. Magnus, Tetrahedron, 1977, 33, 2019. (d) E. N.
Prilezhaeva, Russ. Chem. Rev., 2000, 69, 367. (e) A. Costa, C.
Najera, J. M. Sansano, J. Org. Chem., 2002, 67, 5216. (f) M. S.
Vedula, A. B. Pulipaka, C. Venna, V. K. Chintakunta, S. Jinnapally,
V. A. Kattuboina, R. K. Vallakati, V. Basetti, V. Akella, S. Rajgopal,
A. K. Reka, S. K. Teepireddy, P. K. Mamnoor, R. Rajagopalan, G.
Bulusu, A. Khandelwal, V. V. Upreti and S. R. Mamidi, Eur. J. Med.
Chem., 2003, 38, 811. (g) S. F. Barbuceanu, G. L. Almajan, I.
Saramet, C. Draghici, A. I. Tarcomnicu and G. Bancescu, Eur. J.
Med. Chem., 2009, 44, 4752. (h) T. M. Williams, T. M. Ciccarone, S.
C. MacTough, C. S. Rooney, S. K. Balani, J. H. Condra, E. A. Emini,
M. E. Goldman, W. J. Greenlee, L. R. Kauffman, J. A. O’Brien, V. V.
Sardana, W. A. Schleif, A. D. Theoharides and P. S. Anderson, J.
Med. Chem., 1993, 36, 1291.
0. (a) N. K. Konduru, S. Dey, M. Sajid, M. Owais and N. Ahmed, Eur.
J. Med. Chem., 2013, 59, 23. (b) Y. Chen, Y. Lam and Y.-H. Lai, Org.
Lett., 2003, 5, 1067. (c) B. Sreedhar, M. A. Reddy, P. S. Reddy,
Synlett, 2008, 1949. (d) H. Gilman and L. F. Cason, J. Am. Chem.
Soc., 1950, 72, 3469. (e) M. Fernandez, U. Uria, L. Orbe, J. L.
Vicario, E. Reyes and L. Carrillo, J. Org. Chem., 2014, 79, 441. (f)
T. A. Kovalchuk, N. M. Kuzmenok and A. M. Zvonok, Chem.
Heterocycl. Comp., 2005, 41, 1237.
c
P. R. China; and Department of Chemistry and Biochemistry, Texas
Tech University, Lubbock, TX 79409-1061, USA; guigen.li@ttu.edu;
1
these authors are equal to this work. Electronic supplementary
information (ESI) available. CCDC 1406678 (3f). For ESI and
crystallographic data in CIF or other electronic format see DOI:
1
0.1039/
95
1
. For selected reviews, see: (a) M. Malacria, Chem. Rev., 1996, 96,
2
89. (b) D. P. Curran, Aldrichimica Acta, 2000, 33, 104. (c) S. Z.
Zard, Radical Reactions in Organic Synthesis; Oxford University
Press: Oxford, UK, 2003. (d) Togo, H. Advanced Free Radical
Reactions for Organic Synthesis; Elsevier: Amsterdam, 2004. (e) B.
B. Snider, Oxidative Free-Radical Cyclizations and Additions with
Mono and β-Dicarbonyl Compounds. In Handbook of C-H
Transformations: Applications in Organic Synthesis; G. Dyker, Ed.;
Wiley-VCH: Weinheim, 2005; Vol. 2, pp 371-377. (f) M. Albert, L.
Fensterbank, E. Lacote and M. Malacria, Topics in Current
Chemistry; Gansꢀuer, A., Ed.; Springer: Berlin, 2006; Vol. 264, p 1.
2
3
3
4
4
5
5
6
6
5
0
5
0
5
0
5
0
5
1
1
1
1
1
1
00
05
10
15
1
(g) P. Renaud and M. P. Sibi, Radicals in Organic Synthesis; Wiley-
VCH: Weinheim, 2008. (h) E. Godineau and Y. Landais, Chem.-Eur.
J., 2009, 15, 3044. (i) S. Hata and M. P. Sibi, Science of Synthesis-
Stereoselective Reactions of C-C double bonds; J. G. de Vries, Ed.;
Georg Thieme Verlag: Stuttgart, 2011; p873.
2
.
For selected examples, see: (a) W. Kong, N. Fuentes, A. Garcia-
Dominguez, E. Merino and C. Nevado, Angew. Chem., Int. Ed.,
2015, 54, 2487. (b) N. Fuentes, W. Kong, L. Fernandez-Sanchez, E.
Merino and C. Nevado, J. Am. Chem. Soc., 2015, 137, 964. (c) W.
Kong, E. Merino and C. Nevado, Angew. Chem., Int. Ed., 2014, 53,
1
1. (a) S. Mondal, B. Gold, R. K. Mohamed, H. Phan and I. V. Alabugin,
J. Org. Chem., 2014, 79, 7491. (b) S. Mondal, R. K. Mohamed, M.
Manoharan, H. Phan and I. V. Alabugin, Org. Lett., 2013, 15, 5650.
(c) G.-B. Deng, Z.-Q. Wang, J.-D. Xia, P.-C. Qian, R.-J. Song, M.
Hu, L.-B. Gong and J.-H. Li, Angew. Chem. Int. Ed., 2013, 52, 1535.
5
078. (d) W. Kong, M. Casimiro, N. Fuentes, E. Merino, and C.
(d) Y. Liu, J.-L. Zhang, M.-B. Zhou, R.-J. Song and J.-H. Li, Chem.
Nevado, Angew. Chem., Int. Ed., 2013, 52, 13086.
Commun., 2014, 50, 14412. (e) Y. Liu, J.-L. Zhang, R.-J. Song, P.-C.
Qian and J.-H. Li, Angew. Chem. Int. Ed., 2014, 53, 9017.
3. For selected examples, see: (a) W.-T. Wei, M.-B. Zhou, J.-H. Fan, W.
Liu, R.-J. Song, Y. Liu, M. Hu, P. Xie and J.-H. Li, Angew. Chem.,
Int. Ed., 2013, 52, 3638; (b) M.-B. Zhou, C.-Y. Wang, R.-J. Song, Y.
Liu, W.-T. Wei and J.-H. Li, Chem. Commun., 2013, 49, 10817; (c)
Y. Meng, L.-N. Guo, H. Wang and X.-H. Duan, Chem. Commun.,
2013, 49, 7540; (d) H. Wang, L.-N. Guo and X.-H. Duan, Chem.
Commun., 2013, 49, 10370; (e) Z. Li, Y. Zhang, L. Zhang and Z.-Q.
Liu, Org. Lett., 2014, 16, 382.
20 12. (a) O. Miyata, A. Nishiguchi, I. Ninomiya, T. Naito, K. Aoe and K.
Okamura, Tetrahedron Lett., 1996, 37, 229. (b) O. Miyata, Y. Ozawa,
I. Ninomiya and T. Naito, Tetrahedron, 2000, 56, 6199. (c) O.
Miyata, Y. Ozawa, I. Ninomiya and T. Naito, Synlett, 1997, 275. (d)
T. Naito, Y. Honda, O. Miyata and I. Ninomiya, J. Chem. Soc.,
25
Perkin Trans. 1, 1995, 19.
4
.
(a) S.-L. Zhou, L.-N. Guo, S. Wang and X.-H. Duan, Chem.
Commun., 2014, 50, 3589. (b) W.-P. Mai, J.-T. Wang, L.-R. Yang, J.-
W. Yuan, Y.-M. Xiao, P. Mao and L.-B. Qu, Org. Lett., 2014, 16,
2
04. (c) W.-P. Mai, G.-C. Sun, J.-T. Wang, G. Song, P. Mao, L.-R.
Yang, J.-W. Yuan, Y.-M. Xiao and L.-B. Qu, J. Org. Chem., 2014, 79,
094.
8
5
6
.
.
L. Zhang, J. Sun and S. A. Kozmin, Adv. Synth. Catal., 2006, 348,
2271.
For selected examples, see: (a) K. Speck, K. Karaghiosoff and T.
Magauer, Org. Lett., 2015, 17, 1982. (b) C. Blaszykowski, Y. Harrak,
M.-H. Goncalves, J.-M. Cloarec, A.-L. Dhimane, L. Fensterbank
and M. Malacria, Org. Lett., 2004, 6, 3771. (c) C.-H. Chen, Y.-C.
Tsai and R.-S. Liu, Angew. Chem., Int. Ed., 2013, 52, 4599. (d) E.
Tudela, J. Gonzalez, R. Vicente, J. Santamaria, M. A. Rodriguez and
A. Ballesteros, Angew. Chem., Int. Ed., 2014, 53, 12097. (f) K.
Fukamizu, Y. Miyake and Y. Nishibayashi, Angew. Chem., Int. Ed.,
4
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]