Furans Accessed through Visible-Light-Mediated Oxidative [3+2] Cycloaddition of Enols and Alkynes

Article abstract of DOI:10.1002/chem.201704519

Visible-light-mediated formation of furans though direct oxidative [3+2] cycloaddition of 1,3-diones and alkynes is described. This protocol provides a simple and mild route to poly-substituted furans in moderate-to-good yields. Preliminary mechanistic studies suggest that this reaction likely follows a radical addition/cyclization pathway.

Full text of DOI:10.1002/chem.201704519

A Journal of
Accepted Article
Title: Visible-Light-Mediated Oxidative [3+2] Cycloaddition of Enol and
Alkynes to Access Furans
Authors: Ailong Shao, Xu Luo, Chien-Wei Chiang, Meng Gao, and
Aiwen Lei
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201704519
Link to VoR: http://dx.doi.org/10.1002/chem.201704519
Supported by

10.1002/chem.201704519
Chemistry - A European Journal
COMMUNICATION
Visible Light-Mediated Oxidative [3+2] Cycloaddition of Enol and
Alkynes to Access Furans
Ailong Shao,[a] Xu Luo,[a] Chien-Wei Chiang,[a] Meng Gao,[b] and Aiwen Lei*[a],[b]
Abstract: Visible light-mediated formation of furans via direct
oxidative [3+2] cycloaddition of 1,3-diones and alkynes has been
described. This protocol provides a simple and mild way to access
poly-substituted furans in moderate to good yields. Besides,
preliminary mechanistic studies suggest that this reaction most likely
undergoes a radical addition/cyclization pathway.
synthetic intermediates in organic synthesis (Scheme 2).5
Because of the remarkable applications of furans, chemists
focused on using carbonyl compounds as starting materials and
spared no effort to develop new routes to synthesize furans
under mild and green conditions. More recently, direct oxidative
α-C(sp3)–H functionalization of carbonyl compounds, most likely
via SET oxidation/radical cyclization, usually requires large
excess of metal oxidants, such as Mn(III) and Ce(IV) salts.6
Meanwhile, certain transition-metal catalytic procedures have
also been reported for the synthesis of furans.7,8 Besides, our
group reported a similar reaction with molecular iodine as the
promoter under oxidative conditions.9 However, this
transformation could only tolerate β-ketoesters and gave the
corresponding products with a relative low yield at a high
temperature of 90 °C. Therefore, developing much greener and
milder methods to construct furan motifs from simple alkynes is
still in urgent demand.
[3+2] cycloaddition has developed to be
a well-known
methodology for the synthesis of five-membered heterocyclic
compounds, such as furans, pyrroles.1 Until now, classical 1,3-
dipolar cycloaddition, as the main strategy for [3+2]
cycloaddition reaction, are still limited to some specific
substrates such as azomethine ylides, azides, nitrones, nitrile
imines and nitrile oxides (Scheme 1a).2 Moreover, the synthesis
of these substrates requires many steps. Thus, direct oxidative
[3+2] cycloaddition with the use of simple substrates is
undoubtedly an urgent way (Scheme 1b). Although important
progress has been made in this field,3 there still remains a great
challenge in optimization of reaction conditions, efficiency and
selectivity.
Scheme 2. Examples of significant furan-containing pharmaceuticals.
Recently, visible-light photoredox catalysis has been utilized
as a powerful tool to construct C-C and C-heteroatom bonds via
a single-electron transfer (SET) pathway, playing an important
role in large-scale renaissance of radical-based methodologies.
Pioneers, such as MacMillian,10 Stephenson,11 Nicewicz,12
Yoon,13 Xiao14 and Wu15 have done lots of excellent work in
cross-coupling reactions and intermolecular cycloadditions.
Nevertheless, only a few cases were reported about the
synthesis of furans through visible-light-mediated [3+2]
cycloaddition, which still utilized halogenated substrates as
reactants.16 From the perspective of sustainable chemistry and
atom-economy, the possibility of direct C−H functionalization,
especially the oxidative coupling between two C−H bonds,
provides a highly attractive strategy for an ideal chemical
Scheme 1. Models of [3+2] cycloaddition.
Poly-substituted furans are found in many natural products,
pharmaceuticals and agrochemicals,4 and also widely utilized as
synthesis. Herein,
a visible light-mediated oxidative [3+2]
cycloaddition of 1,3-diones and alkynes to access furans was
reported, which illustrated an efficient example of constructing
furans in one step under mild conditions.
Our initial efforts were focused on the reaction between ethyl
cyclohexane-1,3-dione 1a and phenylacetylene 2a by using
Ru(bpy)3Cl2 as the photocatalyst and (NH4)2S2O8 as an oxidant
under the irradiation of 3 W blue LEDs at room temperature. As
a result, the desired 2-phenyl-6,7-dihydrobenzofuran-4(5H)-one
product 3a can be obtained in 35% yield (Table 1, entry 1). To
modify this model reaction, photocatalysts such as Ir(ppy)3,
[a]
[b]
A. Shao, X. Luo, C.-W. Chiang, Prof. Dr. A. Lei
The Institute for Advanced Studies (IAS), College of Chemistry
and Molecular Sciences, Wuhan University
Wuhan 430072 Hubei (P. R. China)
E-mail: aiwenlei@whu.edu.cn
Dr. M. Gao, Prof. Dr. A. Lei
National Research Center for Carbohydrate Synthesis, Jiangxi
Normal University
Nanchang 330022 Jiangxi (P. R. China)
Supporting information for this article is given via a link at the end
of the document.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704519
Chemistry - A European Journal
COMMUNICATION
-
eosin Y, Acr+-MesClO4 , rhodamine B and methylene blue will be
standard conditions, although the furan product could be
achieved by the reaction of 1,3-diones 1 and terminal alkynes 2,
the alkyl alkynes could not be tolerated in this reaction (for
details, see the Supporting Information (Figure 2a)). A possible
explain is that the stability of olefinic carbon radicals, which is
generated from the radical addition of α-carbonyl alkyl radicals
to terminate alkynes, has a significant effect on the yield of this
cycloaddition reaction. Besides, the conjugated effect of the
aromatic ring would make the olefinic carbon radical more stable.
Thus, the aromatic ring of terminal alkynes is necessary. On the
other hand, some internal alkynes have also been tested in this
reaction (for details, see the Supporting Information (Figure 2b)).
Yet the steric effect of these substrates made the α-carbonyl
alkyl radical difficult to accomplish the radical addition to internal
alkynes.
firstly alternated and compared (Table 1, entries 2 - 6). When
the methylene blue was employed as the photocatalyst, the yield
of product could increase to 83% (Table 1, entry 6). In addition,
as the oxidant was changed to other peroxodisulfates, such as
Na2S2O8, K2S2O8, the yield dropped significantly (Table 1,
entries 7, 8). The formation of product was corresponding to the
equivalents of diacrbonyls, when 1a reached to 4 equivalents
(0.8 mmol), the desired product was able to obtained in 83%
yield. Continuously increase 1a didn’t improve the yield (for
details, see the Supporting Information (Figure 1)). The control
experiments showed that only trace product could be detected in
the absence of light, photocatalyst or (NH4)2S2O8 (Table 1,
entries 9 - 11).
Table 1. Optimization of conditions for the reaction of
cyclohexane-1,3-dione 1a and phenylacetylene 2a.[a]
Table 2. Substrate scope for visible light-mediated oxidative
[3+2] cycloaddition of 1,3-cyclohexanedione 1a and Alkynes 2.[a]
[a] Conditions: 1a (0.8 mmol), 2 (0.2 mmol), methylene blue (6 mol%) and
(NH4)2S2O8 (2.0 equiv.) in
3 mL CH3CN under a nitrogen atmosphere,
irradiation with 3 W blue LEDs, room temperature, 12 h; isolated yields. [b] 1
mL acetone was added in the system.
The scope of the 1,3-dione components have been explored
as well (Table 3). For instance, 5-phenylcyclohexane-1,3-dione,
5,5-dimethylcyclohexane-1,3-dione, 5-dimethylcyclohexane-1,3-
dione, 4,4-dimethylcyclohexane-1,3-dione and chromane 2,4-
dione could be well tolerated under the reaction conditions
(Table 3, 3r – 3x). Interestingly, 4,4-dimethylcyclohexane-1,3-
dione and chromane-2,4-dione could give two different isomers
in nearly 1/1 ratio (Table 3, 3u, 3x). Five-membered 1,3-dione
could also be tolerated under the reaction conditions, yet it
resulted in a relative low yield compared to the six-membered
1,3-dione (Table 3, 3y). β-Ketoester and acetylacetone were
also tried with our protocol. Some efforts were made to realize
this transformation by using ethylacetoacetate as the model
substrate. Unfortunately, no matter which photocatalysts and
oxidants we have tried, the reaction could not proceed (for
details, see the Supporting Information (Figure 3a and 3b)).
To gain more insight of the reaction mechanism, radical
trapping reagents such as TEMPO, BHT and 1,1-stilbene have
been introduced to the reaction. Interestingly, only 10% of the
desired product was obtained with BHT; TEMPO could totally
[a] Conditions: 1a (0.8 mmol), 2a (0.2 mmol), Photocatalyst (6 mol%) and
Peroxodisulfate (2.0 equiv.) in 3 mL CH3CN under a nitrogen atmosphere,
irradiation with 3 W blue LEDs, room temperature, 12 h. [b] Isolated yields. [c]
Without light.
With the optimized conditions in hand, we firstly focused on
investigating the scope of terminal aryl alkynes (Table 2). The
reaction was readily extended to different aryl-substituted
terminal alkynes. Good substrate tolerance of alkynes could be
achieved with both electron-withdrawing and electron-donating
functional groups, such as H-, CH3-, (CH3)2CH-, C5H11-, Ph-,
CH3O-, naphthyl- (Table 2, 3a, 3b – 3d, 3e, 3f, 3g, 3h, 3o) and
EtOOC-, CF3-, NO2- (Table 2, 3i and Table 3, 3v, 3w). In
addition, halogen substituted groups, regardless of ortho, meta
or para, such as fluoro, chloro and bromo could also give the
corresponding furans in good yields (Table 2, 3j – 3n). Alkynes
with heterocyclic aromatic ring, for example 1,3-benzodioxolyl
and thiophenyl alkyne, could also afford a moderate yield of the
desired products (Table 2, 3p, 3q). Unfortunately, under the
This article is protected by copyright. All rights reserved.

10.1002/chem.201704519
Chemistry - A European Journal
COMMUNICATION
Table 3. Substrate scope for visible light-mediated oxidative
[3+2] cycloaddition of 1,3-Dione 1 and Alkynes 2.[a]
intramolecular radical addition. Finally, the product 3a is
obtained after the oxidation of Int-C by the PC•+ and the
deprotonation procedure.
[a] Conditions: 1 (0.8 mmol), 2 (0.2 mmol), methylene blue (6 mol%) of and
(NH4)2S2O8 (2.0 equiv.) in
3 mL CH3CN under a nitrogen atmosphere,
irradiation with 3 W blue LEDs, room temperature, 12 h; isolated yields. [b]
Increasing the temperature to 80 °C.
Scheme 4. Proposed mechanism.
inhibit the reaction. Additionally, when 1,1-stilbene was added, it
would compete with phenylacetylene and cyclize with 1,3-dione
to generate the 2,2-diphenyl-3,5,6,7-tetrahydroben-zofuran-
4(2H)-one 4a in 70% yield (Scheme 3). In some cases, 1,1-
stilbene can be used as a radical-trapping reagent as well. Thus,
these results suggested that the cyclization reaction probably
proceeds through a radical process.
In summary, we have developed a visible light-mediated
oxidative [3+2] cycloaddition of enol and alkynes to access
furans. The use of cheap and innocuous methylene blue in
combination with (NH4)2S2O8 as a terminal oxidant could well
accomplish these transformations. Synthetically, the present
protocol provides an atom-economic and highly-selective way to
construct the poly-substituted furans in good yields under the
metal free, mild and simple conditions. Mechanistically, the
reaction most likely undergoes a radical addition/cyclization
mechanism.
Experimental Section
1,3-Dione 1 (0.8 mmol, 89.6 mg), methylene blue (0.012 mmol, 3.5 mg)
and (NH4)2S2O8 (0.4 mmol, 91.2 mg) (from glove box) were added in a
clean sealed Schlenk tube equipped with a stir bar. After flushing the
Schlenk tube three times with nitrogen atmosphere, CH3CN (3 mL) and
alkyne 2 (0.2 mmol, 20.4 mg) were injected in the tube through a syringe
in turn. The reaction mixture was irradiated with 3 W blue LEDs and
stirred at room temperature. After completion of the reaction, as indicated
by TLC and GC-MS, the mixture was then purified by column
chromatography on silica gel using petroleum ether and ethyl acetate as
eluent to afford pure product 3.
Scheme 3. Mechanistic studies.
Based on the above results, we proposed
a general
mechanism for this oxidative [3+2] cycloaddition between 1a and
2a (Scheme 4). Firstly, the photocatalyst can be activated to the
excited-state (PC*, methylene blue) by the visible light irradiation
(3 W blue LEDs).17 The oxidant, persulfate (S2O82-), then was
reduced by the PC* to form the sulfate radical anion (SO4•-)18.
Following the hydrogen atom transfer (HAT) between 1a and
Acknowledgements
sulfate radical anion,
a new carbon radical (Int-A) was
generated. Subsequently, radical addition of Int-A to 2a gives an
olefinic carbon radical (Int-B), which further cyclized to the
carbonyl oxygen to form a five-membered ring (Int-C) through
This work was supported by the 973 Program (2011CB808600,
2012CB725302, 2013CB834804), the National Natural Science
Foundation of China (21390400, 21272180, 21302148, 2109343
This article is protected by copyright. All rights reserved.

10.1002/chem.201704519
Chemistry - A European Journal
COMMUNICATION
Hanai, V. P. Sukhatme and L. Sun, Bioorg. Med. Chem. Lett. 2017, 27,
929.
and 21402217), and the Research Fund for the Doctoral
Program of Higher Education of China (20120141130002) and
the Ministry of Science and Technology of China
(2012YQ120060) and the Program for Changjiang Scholars and
Innovative Research Team in University (IRT1030) and the
Fundamental Research Funds for the Central Universities
(213413000050). The Program of Introducing Talents of
Discipline to Universities of China (111 Program) is also
appreciated.
[5]
[6]
a) D. J. Goldsmith, E. Kennedy and R. G. Campbell, J. Org. Chem.
1975, 40, 3571; b) R. P. Singh, B. M. Foxman and L. Deng, J. Am.
Chem. Soc. 2010, 132, 9558.
a) C.-Y. Qian, J.-I. Hirose, H. Nishino and K. Kurosawa, J. Heterocyclic
Chem. 1994, 31, 1219; b) Y. R. Lee, M. W. Byun and B. S. Kim, B. Kor.
Chem. Soc. 1998, 19, 1080; c) O. Alagoz, M. Yılmaz and A. Tarık Pekel,
Synthetic Commun. 2006, 36, 1005; d) A. Deepthi, A. Sivan and V.
Nandialath, Synthesis 2011, 2011, 2466; e) C. Wang, Z. Li, Y. Ju and S.
Koo, Eur. J. Org. Chem. 2012, 2012, 6976; f) P. Li, J. Zhao, C. Xia and
F. Li, Org. Lett. 2014, 16, 5992.
Keywords: furan • visible light-mediated • oxidative [3+2]
[7]
a) C. He, S. Guo, J. Ke, J. Hao, H. Xu, H. Chen and A. Lei, J. Am.
Chem. Soc. 2012, 134, 5766; b) M. H. Suhre, M. Reif and S. F. Kirsch,
Org. Lett. 2005, 7, 3925; c) A. S. Hashmi, Angew. Chem. Int. Ed. 1995,
34, 1581; d) A. S. Hashmi, L. Schwarz, J.-H. Choi and T. M. Frost,
Angew. Chem. Int. Ed. 2000, 39, 2285; e) A. S. Hashmi, L. Schwarz
and M. Bolte, Eur. J. Org. Chem. 2004, 2004, 1923; f) A. S. Hashmi and
P. Sinha, Adv. Synth. Catal. 2004, 346, 432; g) A. S. Hashmi, T.
Häffner, M. Rudolph and F. Rominger, Eur. J. Org. Chem. 2011, 2011,
667; h) T. Wang, S. Shi, M. Rudolph and A. S. Hashmi, Adv. Synth.
Catal. 2014, 356, 2337; i)T. Wang, S. Shi, M. H. Vilhelmsen, T. Zhang,
M. Rudolph, F. Rominger and A. S. Hashmi, Chem. Eur. J. 2013, 19,
12512; j) Y. Ma, S. Zhang, S. Yang, F. Song and J. You, Angew. Chem.
Int. Ed. 2014, 53, 7870; k) X. Cui, X. Xu, L. Wojtas, M. M. Kim and X. P.
Zhang, J. Am. Chem. Soc. 2012, 134, 19981; l) W. Liu, H. Jiang, M.
Zhang and C. Qi, J. Org. Chem. 2010, 75, 966; m) Y. Yang, J. Yao and
Y. Zhang, Org. Lett. 2013, 15, 3206; n) T. Naveen, R. Kancherla and D.
Maiti, Org. Lett. 2014, 16, 5446; o) T. Naveen, A. Deb and D. Maiti,
Angew. Chem. Int. Ed. 2017, 56, 1111; p) J. Lou, Q. Wang, K. Wu, P.
Wu and Z. Yu, Org. Lett. 2017, 19, 3287; q) U. Sharma, T. Naveen, A.
Maji, S. Manna and D. Maiti, Angew. Chem. Int. Ed. 2013, 52, 12669; r)
H. Zhan, X. Lin, Y. Qiu, Z. Du, P. Li, Y. Li and H. Cao, Eur. J. Org.
Chem. 2013, 2013, 2284; s) M. Zheng, L. Huang, W. Wu and H. Jiang,
Org. Lett. 2013, 15, 1838; t) E. P. Gogonas and L. P. Hadjiarapoglou,
Tetrahedron Lett. 2000, 41, 9299; u) H. Li and R. P. Hsung, Org. Lett.
2009, 11, 4462; v) D. Zha, H. Li, S. Li and L. Wang, Adv. Synth. Catal.
2017, 359, 467; w) Y. Zhao, S. Li, X. Zheng, J. Tang, Z. She, G. Gao
and J. You, Angew. Chem. Int. Ed. 2017, 56, 4286; x) V. Cadierno, J.
Gimeno and N. Nebra, Adv. Synth. Catal. 2007, 349, 382; y) V.
Cadierno, J. Diez, J. Gimeno and N. Nebra, J. Org. Chem. 2008, 73,
5852; z) L. Xia and Y. R. Lee, Eur. J. Org. Chem. 2014, 2014, 3430.
a) R. L. Danheiser, E. J. Stoner, H. Koyama, D. S. Yamashita and C. A.
Klade, J. Am. Chem. Soc. 1989, 111, 4407; b) J. A. Marshall and W. J.
DuBay, J. Org. Chem. 1993, 58, 3602; c) L. A. Paquette and P. C.
Astles, J. Org. Chem. 1993, 58, 165.
cycloaddition
[1]
[2]
a) M. E. Welker, Chem. Rev. 1992, 92, 97; b) G. Pandey, P. Banerjee
and S. R. Gadre, Chem. Rev. 2006, 106, 4484; c) M. Meldal and C. W.
Tornoe, Chem. Rev. 2008, 108, 2952; d) A. R. Katritzky,
Comprehensive Heterocyclic Chemistry III, 1st ed; Elsevier: Amsterdam,
2008. e) G. W. Gribble, J. A. Joule, Progress in Heterocyclic Chemistry;
Elsevier: Amsterdam; New York, 2013.
a) R. Huisgen, H. Stangl, H. J. Sturm and H. Wagenhofer, Angew.
Chem. Int. Ed. 1961, 73, 170; b) R. Huisgen, H. Stangl, H. J. Sturm and
H. Wagenhofer, Angew. Chem. Int. Ed. 1962, 1, 50; c) R. Huisgen,
Angew. Chem. Int. Ed. 1963, 2, 565; d) R. Huisgen, Angew. Chem. Int.
Ed. 1963, 2, 633; e) R. Huisgen, L. Möbius, G. Müller, H. Stangl, G.
Szeimies and J. M. Vernon, Chem. Ber. 1965, 98, 3992; f) R. Huisgen,
G. Szeimies and L. Möbius, Chem. Ber. 1967, 100, 2494; g) R. Huisgen,
H. Gotthardt and R. Grashey, Chem. Ber. 1968, 101, 536; h) R.
Heusgen, J. Org. Chem. 1968, 33, 2291; i) R. Huisgen, H. Stangl, H. J.
Sturm, R. Raab and K. Bunge, Chem. Ber. 1972, 105, 1258; j) R.
Huisgen, 1,3-Dipolar Cycloaddition Chemistry; Padwa, A., Ed.; Wiley:
New York, 1984; k) K. V. Gothelf and K. A. Jørgensen, Chem. Rev.
1998, 98, 863; l) I. Coldham and R. Hufton, Chem. Rev. 2005, 105,
2765; m) M. F. Debets, S. S. van Berkel, J. Dommerholt, A. T. Dirks, F.
P. Rutjes and F. L. van Delft, Acc. Chem. Res. 2011, 44, 805; n) G. Qiu,
Y. Kuang and J. Wu, Adv. Synth. Catal. 2014, 356, 3483; o) T.
Hashimoto and K. Maruoka, Chem. Rev. 2015, 115, 5366; p) T. Wang,
A. Shao, H. Feng, S. Yang, M. Gao, J. Tian and A. Lei, Tetrahedron
2015, 71, 4473; q) J. R. Johansson, T. Beke-Somfai, A. Said
Stalsmeden and N. Kann, Chem. Rev. 2016, 116, 14726.
[3]
a) M. Rueping, D. Leonori and T. Poisson, Chem. Commun. 2011, 47,
9615; b) C. Yu, Y. Zhang, S. Zhang, H. Li and W. Wang, Chem.
Commun. 2011, 47, 1036; c) Y. Q. Zou, L. Q. Lu, L. Fu, N. J. Chang, J.
Rong, J. R. Chen and W. J. Xiao, Angew. Chem. Int. Ed. 2011, 50,
7171; d) Y. R. Chen and W. L. Duan, J. Am. Chem. Soc. 2013, 135,
16754; e) S. Guo, H. Zhang, L. Huang, Z. Guo, G. Xiong and J. Zhao,
Chem. Commun. 2013, 49, 8689; f) L. Huang and J. Zhao, Chem.
Commun. 2013, 49, 3751; g) Y. Unoh, K. Hirano, T. Satoh and M. Miura,
Angew. Chem. Int. Ed. 2013, 52, 12975; h) H.-T. Wang and C.-D. Lu,
Tetrahedron Lett. 2013, 54, 3015; i) T. R. Blum, Y. Zhu, S. A. Nordeen
and T. P. Yoon, Angew. Chem. Int. Ed. 2014, 53, 11056; j) C. Vila, J.
Lau and M. Rueping, Beilstein J. Org. Chem. 2014, 10, 1233; k) J.
Xuan, X. D. Xia, T. T. Zeng, Z. J. Feng, J. R. Chen, L. Q. Lu and W. J.
Xiao, Angew. Chem. Int. Ed. 2014, 53, 5653; l) L. Xu, S. Zhang and P.
Li, Org. Chem. Front. 2015, 2, 459; m) T. T. Zeng, J. Xuan, W. Ding, K.
Wang, L. Q. Lu and W. J. Xiao, Org. Lett. 2015, 17, 4070; n) V. Quint, F.
Morlet-Savary, J. F. Lohier, J. Lalevee, A. C. Gaumont and S. Lakhdar,
J. Am. Chem. Soc. 2016, 138, 7436.
[8]
[9]
S. Tang, K. Liu, Y. Long, X. Qi, Y. Lan and A. Lei, Chem. Commun.
2015, 51, 8769.
[10] C. K. Prier, D. A. Rankic and D. W. C. MacMillan, Chem. Rev. 2013,
113, 5322.
[11] J. M. Narayanam and C. R. Stephenson, Chem. Soc. Rev. 2011, 40,
102.
[12] N. A. Romero and D. A. Nicewicz, Chem. Rev. 2016, 116, 10075.
[13] T. P. Yoon, M. A. Ischay and J. Du, Nat. Chem. 2010, 2, 527.
[14] J. R. Chen, X. Q. Hu, L. Q. Lu and W. J. Xiao, Acc. Chem. Res. 2016,
49, 1911.
[15] a) Q. Liu, Y. N. Li, H. H. Zhang, B. Chen, C. H. Tung and L. Z. Wu,
Chem. Eur. J. 2012, 18, 620; b) X.-W. Gao, Q.-Y. Meng, M. Xiang, B.
Chen, K. Feng, C.-H. Tung and L.-Z. Wu, Adv. Synth. Catal. 2013, 355,
2158; c) C. J. Wu, J. J. Zhong, Q. Y. Meng, T. Lei, X. W. Gao, C. H.
Tung and L. Z. Wu, Org. Lett. 2015, 17, 884; d) X. W. Fan, T. Lei, C.
Zhou, Q. Y. Meng, B. Chen, C. H. Tung and L. Z. Wu, J. Org. Chem.
2016, 81, 7127; e) T. Lei, W. Q. Liu, J. Li, M. Y. Huang, B. Yang, Q. Y.
Meng, B. Chen, C. H. Tung and L. Z. Wu, Org. Lett. 2016, 18, 2479; f)
M. Xiang, Q.-Y. Meng, X.-W. Gao, T. Lei, B. Chen, C.-H. Tung and L.-Z.
Wu, Org. Chem. Front. 2016, 3, 486.
[4]
a) B. H. Lipshutz, Chem. Rev. 1986, 86, 795; b) X. L. Hou, H. Y.
Cheung, T. Y. Hon, P. L. Kwan, T. H. Lo, S. Y. Tong and H. N. C. Wong,
Tetrahedron 1998, 54, 1955; c) S. M. Rahmathullah, J. E. Hall, B. C.
Bender, D. R. McCurdy, R. R. Tidwell and D. W. Boykin, J. Med. Chem.
1999, 42, 3994; d) R. C. Brown, Angew. Chem. Int. Ed. 2005, 44, 850;
e) S. F. Kirsch, Org. Biomol. Chem. 2006, 4, 2076; f) W. J. Moran and A.
Rodríguez, Org. Prep. Proced. Int. 2012, 44, 103; g) F. E. Jernigan, J. I.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704519
Chemistry - A European Journal
COMMUNICATION
[16] a) H. Jiang, Y. Cheng, Y. Zhang and S. Yu, Org. Lett. 2013, 15, 4884;
b) Y. Suzuki, Y. Okita, T. Morita and Y. Yoshimi, Tetrahedron Lett. 2014,
55, 3355; c) Z. G. Yuan, Q. Wang, A. Zheng, K. Zhang, L. Q. Lu, Z.
Tang and W. J. Xiao, Chem. Commun. 2016, 52, 5128; d) H. Zhou, X.
Deng, Z. Ma, A. Zhang, Q. Qin, R. X. Tan and S. Yu, Org. Biomol.
Chem. 2016, 14, 6065.
[17] a) D. A. Nicewicz and T. M. Nguyen, ACS Catal. 2013, 4, 355; b) S. P.
Pitre, C. D. McTiernan, H. Ismaili and J. C. Scaiano, J. Am. Chem. Soc.
2013, 135, 13286.
[18] a) L. K. Wan, J. Peng, M. Z. Lin, Y. Muroya, Y. Katsumura and H. Y. Fu,
Radiat. Phys. Chem. 2012, 81, 524; b) J. Jin and D. W. MacMillan,
Angew. Chem. Int. Ed. 2015, 54, 1565; c) L. Francàs, R. Matheu, E.
Pastor, A. Reynal, S. Berardi, X. Sala, A. Llobet and J. R. Durrant, ACS
Catal. 2017, 5142.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704519
Chemistry - A European Journal
COMMUNICATION
COMMUNICATION
Ailong Shao, Xu Luo, Chien-Wei Chiang,
Meng Gao, and Aiwen Lei*
Page No. – Page No.
Visible Light-Mediated Oxidative [3+2]
Cycloaddition of Enol and Alkynes to
Access Furans
We have developed a visible light-mediated oxidative [3+2] cycloaddition of enol
and alkynes to access furans. This protocol provides a simple and mild way to
access poly-substituted furans in moderate to good yields.
This article is protected by copyright. All rights reserved.