Tunable and chemoselective syntheses of dihydroisobenzofurans and indanones via rhodium-catalyzed tandem reactions of 2-triazole-benzaldehydes and 2-triazole-alkylaryl ketones

Article abstract of DOI:10.1021/ol502617m

Two novel rhodium(II)-catalyzed tandem reactions were developed for the synthesis of dihydroisobenzofuran and indanone derivatives from 2-triazole-benzaldehydes and 2-triazole-alkylaryl ketones. Dihydroisobenzofuran derivatives were obtained in good yield

Full text of DOI:10.1021/ol502617m

Letter
pubs.acs.org/OrgLett
Tunable and Chemoselective Syntheses of Dihydroisobenzofurans
and Indanones via Rhodium-Catalyzed Tandem Reactions of
2‑Triazole-benzaldehydes and 2‑Triazole-alkylaryl Ketones
Hongjuan Shen,† Junkai Fu,† Jianxian Gong,*,† and Zhen Yang*,†,‡,§
†Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School,
Shenzhen 518055, China
‡Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education and Beijing National Laboratory for
Molecular Science (BNLMS), and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
§Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy, Ocean University of China, 5
Yushan Road, Qingdao 266003, China
S
* Supporting Information
ABSTRACT: Two novel rhodium(II)-catalyzed tandem
reactions were developed for the synthesis of dihydroisobenzo-
furan and indanone derivatives from 2-triazole-benzaldehydes
and 2-triazole-alkylaryl ketones. Dihydroisobenzofuran deriv-
atives were obtained in good yields with high regioselectivities
when alcohols were used as nuclophiles in these reactions, whereas the replacement of the alcohol with water resulted in the
diastereoselective formation of highly functionalized indanone derivatives.
nnulation reactions involving the addition of heteroatoms
Ato multiple C−C bonds represent an important method
for the synthesis of heterocyclic compounds,1 and reactions of
these types tend to proceed with high levels of atom economy,
operational simplicity, and variability. 1,3-Dihydroisobenzo-
furans and indanones are privileged scaffolds2 which can be
found in a broad range of natural products and biologically
active compounds,3 and various methods have been developed
to synthesize these compounds.4 In this context, the cyclization
of 2-alkynylbenzyl alcohols to give 1,3-dihydroisobenzofurans is
particularly attractive5 because 2-alkynylbenzyl alcohol can be
readily prepared from the corresponding 2-alkynyl-benzalde-
hydes. Cyclization reactions of this type, however, can be
challenging because 2-alkynylbenzyl alcohols can undergo both
6-endo-dig and 5-exo-dig cyclization reactions which compete
with each other,6 and the regioselectivities of these reactions
must therefore be strictly controlled to avoid the formation of
intractable mixtures of five- and six-membered rings. In the case
of the 5-exo-dig process, it is also necessary to control the
nature of the addition to the triple bond (i.e. anti- versus syn-
addition) to avoid the formation of a mixture of Z- and E-
isomeric isobenzofurans.5
Recently, Fokin, Gevorgyan and co-workers7 disclosed that
Figure 1. Synthetic analysis.
N-sulfonyl 1,2,3-triazoles A existed in equilibrium with
diazoimine tautomer B,8 which can be efficiently intercepted
reactions.14 As illustrated in Figure 1, 3-sulfonyl-4-oxazolines
by transition-metal catalysts to give rise to highly reactive
rhodium(II) azavinyl carbenes C9 (eq 1, Figure 1). This
(D), α-amino ketones (E), and alkoxy enamines (F) could be
made by the reactions of N-sulfonyl 1,2,3-triazoles with
reactive intermediate has been applied to a range of intriguing
transformations, including cyclopropanation,10 transannula-
tion,11 C−H bond insertion,12 and dehydrogenative rearrange-
ment,13 as well as other novel rhodium carbene based
Received: September 4, 2014
© XXXX American Chemical Society
A
dx.doi.org/10.1021/ol502617m | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
aldehydes,11b water,14a and alcohols,14g respectively. In this
aspect, we have reported the synthesis of oxaspirocycles via a
Rh(II)-catalyzed annulation of 1-tosyl-1,2,3-triazole-based allyl
ethers.15
To further evaluate the effect of the nucleophilic alcohol on
the outcome of this reaction, twelve different alcohols were
selected. As expected, all the reactions proceeded smoothly to
give the corresponding products in good yields (Table 2).
As part of our ongoing work toward the development of
novel carbenoid transformations, we herein reported two new
reactions for the synthesis of dihydroisobenzofurans and
indanones dihydroisobenzofurans (H) and indanones (I) via
the Rh(II)-catalyzed tandem reaction of N-sulfonyl 1,2,3-
triazoles (G) with alcohols and water, respectively (eq 2, Figure
1).
Table 2. Rh(II)-Catalyzed Tandem Reactions of 2-Triazole-
benzaldehyde 1a with Diverse Alcohols
a
In our previous investigation, we identified that Rh2(Oct)4
was an efficient catalyst15 to mediate the equilibrium between A
and B (Figure 1). We envisaged that when substrate G (Figure
1) had an ortho-carbonyl group, the formed electrophilic
carbene C might be trapped by this carbonyl group, and the
resultant intermediate might lead to a novel type of reaction.
To explore this feasibility, we first made triazole 1a according to
the published protocol16 and then treated it with Rh2(Oct)4 (5
mol %) in the presence of MeOH in CHCl3 at 120 °C in a
sealed tube (Table 1); to our delight, benzofuran 2a was
Table 1. Substitutional Effects on the Rh(II)-Catalyzed
Tandem Reactions of 2-Triazole-benzaldehydes and 2-
a
Triazole-alkylaryl Ketones
a
Isolated yield.
To expand the application of this reaction, we investigated
the replacement of alcohol with water as the nucleophile. For
model substrate 1a, the use of water did not result in the
expected product 2′ and, instead, led to the formation of highly
functionalized 2-amino-3-hydroxyl-indanone 4a, which was
isolated as a single isomer in 90% yield when Sc(OTf)3 (2
mol %) was added (Table 3). The relative configuration of 4a
was established by NOESY experiments (see Supporting
Information for details).
2-Amino-3-hydroxyl-indanone is the core structure of nature
product spirobenzylisoquinolines,18 as well as many other
Table 3. Rh(II)-Catalyzed Tandem Reactions of 2-Triazole-
a
benzaldehyde with Water
a
Isolated yield.
obtained in 85% yield under optimal reaction conditions (see
Supporting Information). The structure of 2a was unambigu-
ously established by X-ray crystallographic analysis of its
derivative.17
The scope of N-sulfonyl 1,2,3-triazoles bearing electron-
donating or -withdrawing groups on their aryl rings was
investigated as shown in Table 1.
Pleasingly, all of the substrates reacted smoothly under the
optimized conditions to give the corresponding products in
satisfactory yields. According to the results, we can make the
following observations: (1) both electron-rich (2b−2e) and
electron-deficient (2f−2i) 2-triazole-benzaldehydes are good
substrates; (2) 2-triazole-benzoketones can form benzofurans
bearing quaternary carbon centers (2j−2l) in a regioselective
manner; (3) when triazole based phenylpropan-2-one is
selected as a substrate, the six-membered carbocycle 2m can
be obtained in good yield.
a
Isolated yield.
B
dx.doi.org/10.1021/ol502617m | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
biologically active molecules.19 Therefore, the development of a
stereoselective method20 for their synthesis remains highly
desirable. With this in mind, we conducted an investigation of
our newly discovered reaction, with the aim of developing a
robust and stereoselective process for the synthesis of 2,3-
disubstituted indanones. The scope of this annulation reaction
was evaluated using a broad range of 2-triazole-benzaldehydes
bearing electron-donating or -withdrawing groups on their
phenyl rings (Table 3). The results of these scoping reactions
revealed that substrates bearing electron-donating groups gave
the corresponding indanones (4b−4e) in good yield, whereas
substrates bearing electron-withdrawing groups (F− or Cl−)
gave lower yields (4f−4h). Furthermore, the application of the
optimized reaction conditions to 2-triazole-alkylaryl ketone
failed to provide any of the desired product 4i, with the
substrate undergoing decomposition.
rhodium(II)-catalyzed tandem reaction of 2-triazole-benzalde-
hydes and 2-triazole-alkylaryl ketones by using alcohols and
water as nucleophiles, respectively. Mechanistic studies suggest
that a Rh-associated oxonium intermediate is involved in the
stereoselective reaction. Despite the prevalence of rhodium(II)
azavinyl carbene (C in Figure 1) in the rhodium-catalyzed
reactions of N-sulfonyl 1,2,3-triazoles, these reactions demon-
strate the potential of this organometallic species in the
construction of scaffolds which are important in biomedical
research and drug discovery.
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures, spectral and other characterization
data. This material is available free of charge via the Internet at
http://pubs.acs.org.
Based on the results described above, we proposed a
mechanism for these catalytic reactions (Figure 2). The initial
AUTHOR INFORMATION
Corresponding Authors
■
*E-mail: gongjx@pku.edu.cn.
*E-mail: zyang@pku.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the NSF of China (Grant No.
21372016), 973 Program (2012CB722602), National 863
Program (2013AA090203), and NSFC-Shandong Joint Fund
for Marine Science Research Centers (U1406402).
REFERENCES
■
(1) (a) Chemler, S. R.; Fuller, P. H. Chem. Soc. Rev. 2007, 36, 1153.
(b) Molteni, V.; Ellis, D. A. Curr. Org. Synth. 2005, 2, 333. (c) Wolfe, J.
P.; Thomas, J. S. Curr. Org. Chem. 2005, 9, 625.
(2) Evans, B. E.; Rittle, K. E.; Bock, M. G.; DiPrado, R. M.;
Freidinger, R. M.; Whitterm, W. L.; Lundell, G. F.; Veber, D. F.;
Anderson, P. S.; Chang, R. S. L.; Lotti, V. J.; Cerino, D. J.; Chen, T. B.;
Kling, P. J.; Kunkel, K. A.; Springer, J. P.; Hirshfield, M. J. Med. Chem.
1998, 31, 2235.
(3) (a) Duarte, C. D.; Barreiro, E. J.; Fraga, C. A. Mini-Rev. Med.
Chem. 2007, 7, 1108. (b) Fugmann, B.; Lang-Fugmann, S.; Steglich,
W.; Adam, G. Rompp Encyclopedia of Natural Products; Thieme: New
York, 2000.
(4) For selected examples of synthesis of dihydroisobenzofurans, see:
(a) Godet, T.; Vaxelaire, C.; Michel, C.; Milet, A.; Belmont, P.
Chem.Eur. J. 2007, 13, 5632. (b) Godet, T.; Bosson, J.; Belmont, P.
Synlett 2005, 2786. (c) Wang, F.; Wang, Y.; Cai, L.; Miao, Z.; Chen, R.
Adv. Synth. Catal. 2008, 350, 2733. (d) Cikotiene, I.; Morkunas, M.;
Motiejaitis, D.; Brukstus, A. Synlett 2008, 1693. (e) Dell’Acqua, M.;
Facoetti, D.; Abbiati, G.; Rossi, E. Synthesis 2010, 2367. (f) Dell’Acqua,
M.; Facoetti, D.; Abbiati, G.; Rossi, E. Tetrahedron 2011, 67, 1552.
(g) Chai, Z.; Xie, Z.-F.; Liu, X.-Y.; Zhao, G.; Wang, J.-D. J. Org. Chem.
2008, 73, 2947. (h) Pawar, S. K.; Wang, C.-D.; Bhunia, S.; Jadhav, A.
M.; Liu, R.-S. Angew. Chem., Int. Ed. 2007, 52, 7559. Selected
examples for the synthesis of indanones, see: (i) Sun, F.-g.; Ye, S. Org.
Biomol. Chem. 2011, 9, 3632. (j) Fallion, E.; Fishlock, D. J. Am. Chem.
Soc. 2005, 127, 13144. (k) Snyder, S. A.; Zografos, A. L.; Lin, Y. Angew.
Chem., Int. Ed. 2007, 46, 8186. (l) Snyder, S. A.; Breazzano, S. P.; Ross,
A. G.; Lin, Y.; Zografos, A. L. J. Am. Chem. Soc. 2009, 131, 1753.
(m) Jeffrey, J. L.; Sarpong, R. Org. Lett. 2009, 11, 5450. (n) Yang, Y.;
Dean, P.; Pan, S. J. Org. Chem. 2011, 76, 1902. (o) Yu, Y.-N.; Xu, M.-
H. J. Org. Chem. 2013, 78, 2736. (p) Wang, J.; Zhou, Y.; Zhang, L.; Li,
Z.; Chen, X.; Liu, H. Org. Lett. 2013, 15, 1508. (q) Zi, W.; Toste, F. D.
J. Am. Chem. Soc. 2013, 135, 12600.
Figure 2. Proposed reaction mechanisms for the formation of
dihydroisobenzofurans and 2-amino-3-hydroxyl indanones.
Rh(II)-catalyzed denitrogenation of the N-sulfonyl 1,2,3-
triazole 1a would give the rhodium(II) azavinyl carbene 5,
which was then subjected to a nucleophilic addition of the
oxygen atom of the carbonyl group21 to form the key oxonium
intermediate 6. The nucleophilic addition of MeOH or water6e
to the intermediate 6 would result in the formation of
intermediate 7 by path 1 or intermediate 8 by path 2,
respectively. Finally, decoordination of rhodium from 7 and 8
would liberate the corresponding products and regenerate the
catalyst.
To support the existence of the oxonium intermediate 6 as a
key intermediate in these reactions, we conducted a single
reaction where compound 1a was initially treated with a
catalytic amount22 of Rh2(Oct)4 in CHCl3 at 120 °C. After 2 h,
the substrate 1a was consumed, and methanol, water, and a
catalytic amount of Sc(OTf)3 were then added, respectively,
followed by reaction for an additional 2 and 10 h. As a result,
products 2a and 4a were obtained in 80% and 82% yield,
respectively. These results suggested that the oxonium
intermediate 6 was initially formed via a nucleophilic addition
of its carbonyl group, which trigged the downstream reactions.
In summary, a regio- and stereoselective synthesis of
structurally diverse dihydroisobenzofurans and 2-amino-3-
hydroxyl indanones has been achieved via a novel type of
C
dx.doi.org/10.1021/ol502617m | Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
(5) (a) Padwa, A.; Krumpe, K. E.; Weingarten, M. D. J. Org. Chem.
1995, 60, 5595. (b) Hiroya, K.; Jouka, R.; Kameda, M.; Yasuhara, A.;
Sakamoto, T. Tetrahedron 2001, 57, 9697. (c) Gabriele, B.; Salerno,
G.; Fazio, A. Tetrahedron 2003, 59, 6251. (d) Hashmi, A. S. K.;
Schafer, S.; Wolfle, M.; Gil, C. D.; Fischer, P.; Laguna, A.; Blanco, M.
C.; Gimeno, M. C. Angew. Chem., Int. Ed. 2007, 46, 6184. (e) Chai, Z.;
Xie, Z.-F.; Liu, X.-Y.; Zhao, G.; Wang, J.-D. J. Org. Chem. 2008, 73,
2947.
(17) CCDC 1011641 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/datarequest/cif.
(18) (a) Colton, M. D.; Guinaudeau, H.; Shamma, M. J. Nat. Prod.
1985, 48, 846. (b) Preisner, R. M.; Shamma, M. J. Nat. Prod. 1980, 43,
305. (c) Iwasa, K.; Kamigauchi, M.; Takao, N. J. Nat. Prod. 1988, 51,
1232. (d) Hussain, S. F.; Minard, R. D.; Freyer, A. J.; Shamma, M. J.
Nat. Prod. 1981, 44, 169. (e) Kim, D.-K.; Shin, T.-Y. Arch Pharm. Res.
2000, 23, 459. (f) Nagle, D. G.; Zhou, Y.-D.; Park, P. U.; Paul, V. J.;
Rajbhandari, I.; Duncan, C. J. G.; Pasco, D. S. J. Nat. Prod. 2000, 63,
1431.
(19) (a) Askin, D.; Wallace, M. A.; Vacca, J. P.; Reamer, R. A.;
Volante, R. P.; Shinkai, I. J. Org. Chem. 1992, 57, 2771. (b) Arefalk, A.;
Wannberg, J.; Larhed, M.; Hallberg, A. J. Org. Chem. 2006, 71, 1265.
(c) Silva, L. F., Jr.; Siqueira, F. A.; Pedrozo, E. C.; Vieira, F. Y. M.;
Doriguetto, A. C. Org. Lett. 2007, 9, 1433. (d) Gomtsyan, A.; Bayburt,
E. K.; Schidt, R. C.; Surowy, C. S.; Honore, P.; Marsh, K. C.; Hannick,
S. N.; McDonald, H. A.; Wetter, J. M.; Sullivan, J. P.; Jarvis, M. F.;
Faltynek, C. R.; Lee, C.-H. J. Med. Chem. 2008, 51, 392. (e) Kim, S. H.;
Kwon, S. H.; Park, S.-H.; Lee, J. K.; Bang, H.-S.; Nam, S. J.; Kwon, H.
C.; Shin, J.; Oh, D.-C. Org. Lett. 2013, 15, 1834.
(20) (a) McLean, S.; Dime, D. Can. J. Chem. 1976, 55, 924.
(b) Nalliah, B. C.; MacLean, D. B.; Holland, H. L.; Rodrigo, R. Can. J.
Chem. 1979, 57, 1545. (c) Dime, D.; McLean, S. Can. J. Chem. 1979,
57, 1569. (d) Hanaoka, M.; Kim, S. K.; Sakurai, S.-I.; Sato, Y.; Mukai,
C. Chem. Pharm. Bull. 1987, 35, 3155. (e) Hanaoka, M.; Kohzu, M.;
Yasuda, S. Chem. Pharm. Bull. 1988, 36, 4248.
(6) (a) Jong, T.-T.; Leu, S.-J. J. Chem. Soc., Perkin Trans. 1 1990, 423.
(b) Gulias, M.; Rodriguez, J. R.; Castedo, L.; Mascarenas, J. L. Org.
Lett. 2003, 5, 1975. (c) Patil, N. T.; Yamamoto, Y. J. Org. Chem. 2004,
69, 5139. (d) Gelin, E.; Toullec, P. Y.; Antoniotti, S.; Brancour, C.;
Genet, J.-P.; Michelet, V. J. Am. Chem. Soc. 2006, 128, 3112.
(e) Godet, T.; Vaxelaire, C.; Michel, C.; Milet, A.; Belmont, P.
Chem.Eur. J. 2007, 13, 5632.
(7) Horneff, T.; Chuprakov, S.; Chernyak, N.; Gevorgyan, V.; Fokin,
V. V. J. Am. Chem. Soc. 2008, 130, 14972.
(8) For earlier reports on the ring-opening of N-sulfonyl 1,2,3-
triazoles, see: (a) Harmon, R. E.; Stanley, F.; Gupta, S. K.; Johnson, J.
J. Org. Chem. 1970, 35, 3444. (b) Himbert, G.; Regitz, M. Chem. Ber.
1972, 105, 2963. (c) Himbert, G.; Regitz, M. Synthesis 1972, 571.
(9) For reviews, see: (a) Chattopadhyay, B.; Gevorgyan, V. Angew.
Chem., Int. Ed. 2012, 51, 862. (b) Gulevich, A. V.; Gevorgyan, V.
Angew. Chem., Int. Ed. 2013, 52, 1371. (c) Davies, H. M.; Alford, J. S.
Chem. Soc. Rev. 2014, 43, 5151.
(10) (a) Grimster, N.; Zhang, L.; Fokin, V. V. J. Am. Chem. Soc. 2010,
132, 2510. (b) Chuprakov, S.; Kwok, S. W.; Zhang, L.; Lercher, L.;
Fokin, V. V. J. Am. Chem. Soc. 2009, 131, 18034.
(21) Selected examples: (a) Padwa, A. Chem. Soc. Rev. 2009, 38,
3072. (b) Muthusamy, S.; Gnanaprakasam, B.; Suresh, S. Org. Lett.
2005, 7, 4577. (c) Asao, N.; Takahashi, K.; Lee, S.; Kasahara, T.;
Yamamoto, Y. J. Am. Chem. Soc. 2002, 124, 12650. (d) Barluenga, J.;
Vasquez-Villa, H.; Ballesteros, A.; Gonzalez, J. M. J. Am. Chem. Soc.
2003, 125, 9028. (e) Yue, D.; Ca, N. D.; Larock, R. C. Org. Lett. 2004,
6, 1581. (f) Asao, N.; Chan, C. S.; Takahashi, K.; Yamamoto, Y.
Tetrahedron 2005, 61, 11322.
(11) (a) Chattopadhyay, B.; Gevorgyan, V. Org. Lett. 2011, 13, 3746.
(b) Zibinsky, M.; Fokin, V. V. Angew. Chem., Int. Ed. 2013, 52, 1507.
(c) Chuprakov, S.; Kwok, S. W.; Fokin, V. V. J. Am. Chem. Soc. 2013,
135, 4652. (d) Schultz, E. E.; Sarpong, R. J. Am. Chem. Soc. 2013, 135,
4696. (e) Parr, B. T.; Green, S. A.; Davies, H. M. L. J. Am. Chem. Soc.
2013, 135, 4716. (f) Spangler, J. E.; Davies, H. M. L. J. Am. Chem. Soc.
2013, 135, 6802. (g) Alford, J. S.; Spangler, J. E.; Davies, H. M. L. J.
Am. Chem. Soc. 2013, 135, 11712. (h) Miura, T.; Tanaka, T.; Hiraga,
K.; Stewart, S. G.; Murakami, M. J. Am. Chem. Soc. 2013, 135, 13652.
(i) Miura, T.; Funakoshi, Y.; Murakami, M. J. Am. Chem. Soc. 2014,
136, 2272. (j) Kwok, S. W.; Zhang, L.; Grimster, N. P.; Fokin, V. V.
Angew. Chem., Int. Ed. 2014, 53, 3452. (k) Kim, C.-E.; Park, S.; Eom,
D.; Seo, B.; Lee, P. H. Org. Lett. 2014, 16, 1900. (l) Yang, J.-M.; Zhu,
C.-Z.; Tang, X.-Y.; Shi, M. Angew. Chem., Int. Ed. 2014, 53, 5142.
(m) Shang, H.; Wang, Y.-H.; Tian, Y.; Feng, J.; Tang, Y.-F. Angew.
Chem., Int. Ed. 2014, 53, 5662.
(22) Hodgson, D. M.; Pierard, F. Y. T. M.; Stupple, P. A. Chem. Soc.
Rev. 2001, 30, 50.
(12) Chuprakov, S.; Malik, J. A.; Zibinsky, M.; Fokin, V. V. J. Am.
Chem. Soc. 2011, 133, 10352.
(13) (a) Miura, T.; Funakoshi, Y.; Morimoto, M.; Biyajima, T.;
Murakami, M. J. Am. Chem. Soc. 2012, 134, 17440. (b) Selander, N.;
Worrell, B. T.; Fokin, V. V. Angew. Chem., Int. Ed. 2012, 51, 13054.
(14) (a) Miura, T.; Biyajima, T.; Fujii, T.; Murakami, M. J. Am. Chem.
Soc. 2012, 134, 194. (b) Selander, N.; Fokin, V. V. J. Am. Chem. Soc.
2012, 134, 2477. (c) Alford, J. S.; Davies, H. M. L. Org. Lett. 2012, 14,
6020. (d) Miura, T.; Tanaka, T.; Biyajima, T.; Yada, A.; Murakami, M.
Angew. Chem., Int. Ed. 2013, 52, 3883. (e) Selander, N.; Worrell, B. T.;
Chuprakov, S.; Velaparthi, S.; Fokin, V. V. J. Am. Chem. Soc. 2012, 134,
14670. (f) Parr, B. T.; Davies, H. M. L. Angew. Chem., Int. Ed. 2013, 52,
10044. (g) Chuprakov, S.; Worrell, B. T.; Selander, N.; Sit, R. K.;
Fokin, V. V. J. Am. Chem. Soc. 2014, 136, 195. (h) Jung, D. J.; Jeon, H.
J.; Kim, J. H.; Kim, Y.; Lee, S. Org. Lett. 2014, 16, 2208. (i) Miura, T.;
Funakoshi, Y.; Tanaka, T.; Murakami, M. Org. Lett. 2014, 16, 2760.
(j) Xing, Y.; Sheng, G.; Wang, J.; Lu, P.; Wang, Y. Org. Lett. 2014, 16,
1244. (k) Boyer, A. Org. Lett. 2014, 16, 1660. (l) Chen, K.; Zhu, Z.-Z.;
Zhang, Y.-S.; Tang, X.-Y.; Shi, M. Angew. Chem., Int. Ed. 2014, 53,
8492.
(15) Fu, J.-K.; Shen, H.-J.; Chang, Y.-Y.; Li, C.-C.; Gong, J.-X.; Yang,
Z. Chem.Eur. J. 2014, 20, 12881.
(16) The references for the synthesis of triazole 1: (a) Raushel, J.;
Fokin, V. V. Org. Lett. 2010, 12, 4952. (b) Liu, Y.; Wang, X.; Xu, J.;
Zhang, Q.; Zhao, Y.; Hu, Y. Tetrahedron 2011, 67, 6294.
D
dx.doi.org/10.1021/ol502617m | Org. Lett. XXXX, XXX, XXX−XXX