Successively recycle waste as catalyst: A one-pot wittig/1,4-reduction/paal-knorr sequence for modular synthesis of substituted furans

Article abstract of DOI:10.1021/acs.orglett.5b00442

A one-pot tandem Wittig/conjugate reduction/Paal-Knorr reaction is reported for the synthesis of di- or trisubstituted furans. This novel sequence first demonstrates the possibility of successively recycling waste from upstream steps to catalyze downstream reactions.

Full text of DOI:10.1021/acs.orglett.5b00442

Letter
pubs.acs.org/OrgLett
Successively Recycle Waste as Catalyst: A One-Pot Wittig/1,4-
Reduction/Paal−Knorr Sequence for Modular Synthesis of
Substituted Furans
Long Chen,† Yi Du,‡ Xing-Ping Zeng,† Tao-Da Shi,† Feng Zhou,† and Jian Zhou*,†,§
†Shanghai Key Laboratory of Green Chemistry and Chemical Process, School of Chemistry and Molecular Engineering, East China
Normal University, Shanghai 200062, P. R. China
‡Xinhua Hospital, Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200092, P. R. China
§State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, CAS, Shanghai 200032, P. R. China
S
* Supporting Information
ABSTRACT: A one-pot tandem Wittig/conjugate reduction/
Paal−Knorr reaction is reported for the synthesis of di- or
trisubstituted furans. This novel sequence first demonstrates
the possibility of successively recycling waste from upstream
steps to catalyze downstream reactions.
aste prevention is the central task of green chemistry.1 To
one is Wittig-conjugate reduction reaction reusing Ph3PO to
Wreduce waste generation, an effective strategy attracting activate HSiCl3 for conjugate reduction of enones and the other
is a Wittig-cyanosilylation reaction reclaiming Ph3PO as a
cocatalyst for asymmetric cyanosilyaltion of enones.8a The
tandem Wittig-reduction reaction further enabled the synthesis
of α-CF3 γ-keto esters via chemoselective 1,4-reduction of β-CF3
substituted enones, a task difficult to realize by other methods.8b
Most recently, we reported a tandem substitution−Krapcho
reaction, reusing byproduct metal halide for dealkoxycarbony-
lative synthesis of α-fluorinated esters.8c On the basis of these
results, we considered a one-pot tandem Wittig/conjugate
reduction/Paal−Knorr reaction for modular syntheses of
substituted furans (Scheme 1). A remarkable feature of this
ever-increasing attention is to develop a one-pot tandem
synthesis, which is also able to effectively save time, labor,
energy, and materials and minimize yield losses relating to the
isolation of intermediates as well.2 During the past decade, new
concepts continue to be exploited for the design of tandem
reactions, such as organocatalytic cascade3 and multicatalyst-
promoted tandem reactions.4 In this context, a new type of
tandem reaction emerges, aiming at internal recycling waste
produced in the upstream step as catalyst or cocatalyst for the
downstream steps.5 Such sustainable tandem reactions can
improve atom-utilization of a multistep synthesis for waste
prevention, as the internal reuse of byproduct reduces the use of
extra substance. Since Alaimo first demonstrated the feasibility of
the concept,6a a variety of rationally designed tandem sequences
that internally recycle waste as catalyst or cocatalyst have been
independently developed by the Tian,6b,c Wu,6d Toy,6e,f and
Coeffard and Greck6g groups for efficient and cost-effective
synthesis of value-added products from simple substrates.
Despite ongoing processes, all of the known protocols could
only recycle waste one time, namely the reuse of waste from one
upstream step.5,6 It remains unexplored whether it is possible to
successively recycle waste from two more upstream steps to
catalyze the following reactions within a tandem sequence.
We are engaged in the development of tandem reactions for
the efficient synthesis of interesting targets for chemistry,
biology, and medicinal research.7 In particular, we are interested
in improving the atom-efficiency of synthetically useful reactions
suffering from low atom-economy by coupling them into tandem
reactions to internally recycle the corresponding byproducts to
benefit the downstream step.8 We have developed two tandem
sequences to improve the atom-utilization of the Wittig reaction:
Scheme 1. Working Model
sequence is to recycle waste twice: (i) reuse waste Ph3PO from
the Wittig reaction of phosphorane 1 with 1,2-dicarbonyl
compounds 2 or 3 to catalyze 1,4-reduction of enone
9
intermediate I using HSiCl3 and (ii) reclaim waste HCl
produced from quenching trichlorosilyl intermediate II to
promote the furan synthesis.10 Here, we report our initial
Received: February 11, 2015
Published: March 2, 2015
© 2015 American Chemical Society
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DOI: 10.1021/acs.orglett.5b00442
Org. Lett. 2015, 17, 1557−1560

Organic Letters
Letter
application of this triple sequence for the modular synthesis of di-
and trisubstituted furans.
as it first appeared since the Wittig step worked inefficiently in
halogenated solvents required for the reduction step. After
condition optimization (see Table S1 of the Supporting
Information), it was determined that the initial Wittig step was
run in toluene at 120 °C using a screw-capped pressure tube.
After full consumption of diketone, toluene was removed,
followed by addition of anhydrous DCE and HSiCl3. The rest of
the procedure was similar to that described above. This protocol
allowed various substituted phosphoranes 1a−m to readily react
with symmetric diketones 3 to give trisubstituted furans 5 in
reasonable yield (Table 2). Both aryl and alkyl symmetric
Substituted furans represent a type of prominent structural
motif in bioactive compounds that have attracted considerable
attention.11 While a number of elegant metal-catalyzed12 or
organocatalytic methods13 have been invented, new and efficient
methods for modular synthesis of polysubstituted furans are still
in demand. Because phosphorane, 1,2-dicarbonyl compounds,
and HSiCl3 were readily available, our sequence constituted an
attractive new approach with broad substrate scope. For example,
2,5-disubstituted furans 4, with different alkyl or aryl groups,
were obtained in reasonable yield from phosphorane 1 and
glyoxal derivatives 2 (Table 1).
Table 2. Tandem Reaction to Furans 5a−v
Table 1. Tandem Reaction to Furans 4a−z
b
time
(h)
yield
(%)
a
entry
R1
R2
5
1
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
3a: Ph
48
48
41
17
36
12
18
23
36
24
48
36
36
24
48
48
36
24
2
5a
5b
5c
5d
5e
5f
84
80
57
71
67
59
52
54
71
60
63
70
69
57
64
58
66
47
52
53
45
30
a
b
entry
R1
R2
4
yield (%)
2
3b: 4-MeC6H4
3c: 4-MeOC6H4
3d: 4-ClC6H4
3e: 4-FC6H4
3f: 4-CF3C6H4
3g: 3-FC6H4
3h: 2-naphthyl
3i: 2-thienyl
3j: Me
1
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
1a: Ph
2a: Ph
4a
4b
4c
4d
4e
4f
63
60
69
71
64
65
67
69
63
60
62
49
58
55
57
56
53
64
48
48
32
57
64
59
61
36
3
2
2b: 4-MeOC6H4
2c: 4-MeC6H4
2d: 4-ClC6H4
2e: 4-FC6H4
4
3
5
4
6
5
7
5g
5h
5i
6
2f: 4-BrC6H4
2g: 4-NO2C6H4
2h: 4-CNC6H4
2i: 4-CF3C6H4
2j: 3-ClC6H4
2k: 2-BrC6H4
2l: 2-naphthyl
2m: 2-thienyl
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
2d: 4-ClC6H4
8
7
4g
4h
4i
9
8
10
11
12
13
14
15
16
17
18
19
20
21
22
5j
9
1b: 4-MeOC6H4 3a: Ph
5k
5l
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
4j
1c: 4-ClC6H4
1d: 4-FC6H4
1e: 4-NO2C6H4
1f: 3-MeOC6H4
1g: 2-ClC6H4
1h: 2-naphthyl
1i: 2-thienyl
1j: Me
3a: Ph
3a: Ph
3a: Ph
3a: Ph
3a: Ph
3a: Ph
3a: Ph
3a: Ph
3a: Ph
3a: Ph
4k
4l
5m
5n
5o
5p
5q
5r
5s
5t
4m
4n
4o
4p
4q
4r
1b: 4-MeOC6H4
1c: 4-ClC6H4
1d: 4-FC6H4
1e: 4-NO2C6H4
1f: 3-MeOC6H4
1g: 2-ClC6H4
1h: 2-naphthyl
1i: 2-thienyl
1j: Me
1k: Et
24
24
24
1l: iPr
5u
5v
4s
4t
1m: tBu
3a: Ph
b
4u
4v
4w
4x
4y
4z
a
Run on a 0.25 mmol scale. Isolated yield.
1k: Et
1l: iPr
diketones 3a−j afforded the desired products 5a−j in good yield.
On the other hand, aryl phosphoranes 1b−h provided furans
5k−q in higher yield than heteroaryl or alkyl ones 1i−m, which
afforded the corresponding products 5r−v in moderate yield.
The bulky tert-butyl phosphorane 1m could also work but gave
product 5v in only 30% yield.
1m: tBu
1n: cyclohexyl
a
b
Run on a 0.25 mmol scale. Isolated yield.
Since the Wittig reaction of 1 and 2 worked well in 1,2-
The use of symmetric 1,2-diketones inevitably gave trisub-
stituted furans with two identical substituents, and the synthesis
of those with three different groups from unsymmetric 1,2-
diketone met with problems due to the poor regioselectivity of
Wittig reaction. Helpfully, tandem reactions from α-substituted
phosphorane 1o and glyoxal derivatives 2 fulfilled this task, as
evidenced by the synthesis of trisubstituted furans 5aa−ah in
Table 3.
dichloroethane (DCE) and was suitable for 1,4-reduction, the
one-pot procedure was very simple. The initial Wittig step was
run in a screw-capped pressure tube using DCE as the solvent at
80 °C. At almost full conversion of 1, HSiCl3 was added, and the
conjugate reduction was run at 25 °C until completion, followed
by addition of two drops of MeOH. The resulting mixture was
vigorously stirred to promote the final furan synthesis.
When 1,2-diketones 3 were used for the synthesis of
trisubstituted furans, the reaction development was not as easy
We tried in vain to access tetrasubstituted furans, as the
reaction of α-substituted phosphorane and diketone failed. Only
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DOI: 10.1021/acs.orglett.5b00442
Org. Lett. 2015, 17, 1557−1560

Organic Letters
Letter
To confirm the role of Ph3PO and HCl in 1,4-reduction and
furan synthesis, respectively, we attempted the following
experiments. As the Wittig reaction of glyoxal derivative 2
showed excellent E-selectivity but that of diketone 3 gave poor
selectivity, we examined the performance of Ph3PO in the 1,4-
reduction of (E)-10a and both isomers of enone 10b,
respectively. Without the presence of Ph3PO, the conjugate
reduction of either (E)-10a or (E)-10b by HSiCl3 failed at 25 °C.
However, in the absence of Ph3PO, the reduction of (Z)-10b
using HSiCl3 could reach completion within 9 h; nevertheless,
the addition of Ph3PO accelerated the reduction to finish within 1
h. These results clearly showed the necessity of Ph3PO in the
conjugate reduction. On the other hand, without the presence of
HCl, both diketone 11a and 11b failed to give the desired furans,
as expected. In addition, no cyclization occurred during flash
column chromatography. This confirmed the indispensible role
of waste HCl in furan synthesis.
Table 3. Tandem Reaction to Furans 5aa−ah
a
b
entry
2
R2
5
yield (%)
1
2
3
4
5
6
7
8
2a
2b
2f
Ph
5aa
5ab
5ac
5ad
5ae
5af
58
54
45
59
61
70
56
56
4-MeOC6H4
4-BrC6H4
2i
4-CF3C6H4
4-NO2C6H4
2-naphthyl
2-thienyl
2g
2l
2m
2n
5ag
5ah
3-MeOC6H4
a
b
Run on a 0.25 mmol scale. Isolated yield.
α-deuterated phosphorane [D]-1a (92% labeled) could react
with diketone 3a to give furan [D]-5a in 59% yield, with 72%
deuterium incorporation. This suggested that our sequence
might be used for the synthesis of deuterated furans on
demand.14
Inspired by Toy’s one-pot Wittig-reductive aldol reaction from
bromides and PPh3,6e,f we further developed a more efficient
procedure starting from bromide 6 and Ph3P. The desired
product 5a was obtained in an impressive overall 44% yield, as
this sequence was essentially composed of five distinct steps,
including phosphorous alkylation, phosphonium salt deproto-
nation, Wittig reaction, conjugate reduction, and furan synthesis,
and high yield (average 85%) was achieved for every step.
In conclusion, we have developed a one-pot tandem Wittig/
1,4-reduction/Paal−Knorr reaction for the modular synthesis of
a wide range of 2,5-substituted and trisubstituted furans from
easily available substrates. This not only demonstrates the
possibility of successively recycling the waste from distinct steps
to catalyze two or more downstream steps within a tandem
sequence but also shows the potential of one-pot tandem
sequences that take advantage of the internally generated waste
in the synthesis of value-added products from easily available
starting materials.
ASSOCIATED CONTENT
* Supporting Information
Experimental procedures and characterization data. This material
is available free of charge via the Internet at http://pubs.acs.org.
■
The utility of our sequence was further shown by the facile
synthesis of 2,5-bis(4-nitrophenyl)furan 7, the precursor to
compound 9 that displayed activity versus Mycobacterium
tuberculosis. Previously, furan 7 was obtained by Pd-catalyzed
Stille coupling of 2,5-bis(tri-n-butylstannyl)furan and 4-
bromonitroarene.15 Our metal-free protocol was an attractive
alternative, as the use of expensive Pd catalyst and toxic tin
reagent was avoided.
S
AUTHOR INFORMATION
Corresponding Author
■
*E-mail: jzhou@chem.ecnu.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Financial support from the 973 program (2011CB808600),
NSFC (21222204), the Ministry of Education (NCET-11-0147
and PCSIRT), and the Program of SSCS (13XD1401600) is
appreciated.
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DOI: 10.1021/acs.orglett.5b00442
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Organic Letters
Letter
(12) For a review, see: (a) Moran, W. J.; Rodríguez, A. Org. Prep.
Proced. Int. 2012, 44, 103. For selected examples, see: (b) Zhang, Z.-M.;
Chen, P.; Li, W.; Niu, Y.; Zhao, X. L.; Zhang, J. Angew. Chem., Int. Ed.
2014, 53, 4350. (c) Ma, Y.; Zhang, S.; Yang, S.; Song, F.; You, J. Angew.
Chem., Int. Ed. 2014, 53, 7870. (d) Chen, W.-L.; Fu, X.; Lin, L.-L.; Yuan,
X.; Luo, W.-W.; Feng, J.-H.; Liu, X.-H.; Feng, X.-M. Chem. Commun.
2014, 50, 11480. (e) Lian, Y.; Huber, T.; Hesp, K. D.; Bergman, R. G.;
Ellman, J. A. Angew. Chem., Int. Ed. 2013, 52, 629. (f) Cao, H.; Zhan, H.;
Cen, J.; Lin, J.; Lin, Y.; Zhu, Q.; Fu, M.; Jiang, H. Org. Lett. 2013, 15,
1080. (g) Li, B.-S.; Liu, W.-X.; Zhang, Q.-W.; Wang, S.-H.; Zhang, F.-M.;
REFERENCES
■
(1) Waste prevention is the primary principle of green chemistry; see:
(a) Trost, B. M. Science 1991, 254, 1471. (b) Wender, P. A. Chem. Rev.
1996, 96, 1. (c) Sheldon, R. A. Pure Appl. Chem. 2000, 72, 1233.
(d) Anastas, P.; Eghbali, N. Chem. Soc. Rev. 2010, 39, 301. (e) He, M.;
Sun, Y.; Han, B. Angew. Chem., Int. Ed. 2013, 52, 9620.
(2) (a) Wasilke, J.-C.; Obrey, S. J.; Baker, R. T.; Bazan, G. C. Chem. Rev.
2005, 105, 1001. (b) Gaunt, M. J.; Johansson, C. C. C.; McNally, A.; Vo,
N. T. Drug Discovery Today 2007, 12, 8. (c) Chapman, C. J.; Frost, C. G.
Synthesis 2007, 1. (d) Bernardi, L.; Fochi, M.; Franchini, M. C.; Ricci, A.
Org. Biomol. Chem. 2012, 10, 2911.
(3) Grondal, C.; Jeanty, M.; Enders, D. Nat. Chem. 2010, 2, 167.
(4) (a) Zhou, J. Chem.Asian J. 2010, 5, 422. (b) Rueping, M.;
Koenigs, R. M.; Atodiresei, I. Chem.Eur. J. 2010, 16, 9350. (c) Patil, N.
T.; Shinde, V. S.; Gajula, B. Org. Biomol. Chem. 2012, 10, 211.
(d) Pellissier, H. Tetrahedron 2013, 69, 7171. (e) Wu, X.; Li, M.-L.;
Gong, L.-Z. Acta. Chim. Sin. 2013, 71, 1091.
(5) For a review, see: (a) Zhou, J. Multicatalyst System in Asymmetric
Catalysis; John Wiley & Sons: New York, 2014, Chapter 9. For recycling
waste as promoters, see: (b) Kinoshita, T.; Okada, S.; Park, S.-R.;
Matsunaga, S.; Shibasaki, M. Angew. Chem., Int. Ed. 2003, 42, 4680.
(c) Nishimoto, Y.; Yasuda, M.; Baba, A. Org. Lett. 2007, 9, 4931.
(d) Zhu, Y.-P.; Gao, Q.-H.; Lian, M.; Yuan, J.-J.; Liu, M.-C.; Zhao, Q.;
Yang, Y.; Wu, A.-X. Chem. Commun. 2011, 47, 12700.
(6) (a) Alaimo, P. J.; O’Brien, R., III; Johnson, A. W.; Slauson, S. R.;
O’Brien, J. M.; Tyson, E. L.; Marshall, A.-L.; Ottinger, C. E.; Chacon, J.
G.; Wallace, L.; Paulino, C. Y.; Connell, S. Org. Lett. 2008, 10, 5111.
(b) Yang, B.-L.; Weng, Z.-T.; Yang, S.-J.; Tian, S.-K. Chem.Eur. J.
2010, 16, 718. (c) Li, H.-H.; Dong, D.-J.; Jin, Y.-H.; Tian, S.-K. J. Org.
Chem. 2009, 74, 9501. (d) Gao, M.; Yang, Y.; Wu, Y.-D.; Deng, C.; Shu,
W.-M.; Zhang, D.-X.; Cao, L.-P.; She, N.-F.; Wu, A.-X. Org. Lett. 2010,
12, 4026. (e) Lu, J.; Toy, P. H. Chem.Asian J. 2011, 6, 2251. (f) Teng,
Y.; Lu, J.; Toy, P. H. Chem.Asian J. 2012, 7, 351. (g) Portalier, F.;
Bourdreux, F.; Marrot, J.; Moreau, X.; Coeffard, V.; Greck, C. Org. Lett.
2013, 15, 5642.
(7) (a) Zhu, F.; Zhou, F.; Cao, Z.-Y.; Wang, C.; Zhang, Y.-X.; Wang, C.-
H.; Zhou, J. Synthesis 2012, 44, 3129. (b) Liu, Y.-L.; Zhou, J. Chem.
Commun. 2013, 49, 4421. (c) Ji, C.-B.; Cao, Z.-Y.; Wang, X.; Wu, D.-Y.;
Zhou, J. Chem.Asian J. 2013, 8, 877. (d) Yin, X.-P.; Zeng, X.-P.; Liu,
Y.-L.; Liao, F.-M.; Yu, J.-S.; Zhou, F.; Zhou, J. Angew. Chem., Int. Ed.
2014, 53, 13740.
(8) (a) Cao, J.-J.; Zhou, F.; Zhou, J. Angew. Chem., Int. Ed. 2010, 49,
4976. (b) Chen, L.; Shi, T.-D.; Zhou, J. Chem.Asian J. 2013, 8, 556.
(c) Zhu, F.; Xu, P.-W.; Zhou, F.; Wang, C.-H.; Zhou, J. Org. Lett. 2015,
17, 972.
(9) For the pioneering work on Ph3PO-catalyzed conjugate reduction
of enone using HSiCl3, see: (a) Sugiura, M.; Sato, N.; Kotani, S.;
Nakajima, M. Chem. Commun. 2008, 4309. (b) Sugiura, M.; Sato, N.;
Sonoda, Y.; Kotani, S.; Nakajima, M. Chem.Asian J. 2010, 4, 478.
(10) (a) Paal, C. Ber. Dtsch. Chem. Ges. 1884, 17, 2756. (b) Knorr, L.
Ber. Dtsch. Chem. Ges. 1884, 17, 2863. (c) Minetto, G.; Raveglia, L. F.;
Sega, A.; Taddei, M. Eur. J. Org. Chem. 2005, 5277 and references cited
therein.
Zhang, S.-Y.; Tu, Y.-Q. Chem.Eur. J. 2013, 19, 5246. (h) Gonzal
́
ez, J.;
Gonzalez, J.; Perez-Calleja, C.; Lopez, L. A.; Vicente, R. Angew. Chem.,
́
́
́
Int. Ed. 2013, 52, 5853. (i) Jiang, H.; Zeng, W.; Li, Y.; Wu, W.; Huang, L.;
Fu, W. J. Org. Chem. 2012, 77, 5179. (j) Cui, X.; Xu, X.; Wojtas, L.; Kim,
M. M.; Zhang, X. P. J. Am. Chem. Soc. 2012, 134, 19981. (k) He, C.; Guo,
S.; Ke, J.; Hao, J.; Xu, H.; Chen, H.; Lei, A. J. Am. Chem. Soc. 2012, 134,
5766. (l) Chen, H.; Lei, A. J. Am. Chem. Soc. 2012, 134, 5766. (m) Yi, H.;
Liu, Q.; Liu, J.; Zeng, Z.; Yang, Y.; Lei, A. ChemSusChem 2012, 5, 214.
(n) Nair, D. K.; Mobin, S. M.; Namboothiri, I. N. N. Tetrahedron Lett.
2012, 53, 3349. (o) Zhou, G.; Liu, F.; Zhang, J. Chem.Eur. J. 2011, 17,
3101. (p) Chen, G.; He, G.; Xue, C.; Fu, C.; Ma, S. Tetrahedron Lett.
2011, 52, 196. (q) Allegretti, P. A.; Ferreira, E. M. Org. Lett. 2011, 13,
5924. (r) Dudnik, A.; Xia, Y.; Li, Y.; Gevorgyan, V. J. Am. Chem. Soc.
2010, 132, 7645. (s) Liu, F.; Qian, D.; Li, L.; Zhao, X.; Zhang, J. Angew.
Chem., Int. Ed. 2010, 49, 6669. (t) Egi, M.; Azechi, K.; Akai, S. Org. Lett.
2009, 11, 5002. (u) Barluenga, J.; Riesgo, L.; Vicente, R.; Lopez, L. A.;
Tomas, M. J. Am. Chem. Soc. 2008, 130, 13528. (v) Correa, A.; Marion,
N.; Fensterbank, L.; Malacria, M.; Nolan, S. P.; Cavallo, L. Angew. Chem.,
Int. Ed. 2008, 47, 718. (w) Gu, Z.; Wang, X.; Shu, W.; Ma, S. J. Am. Chem.
Soc. 2007, 129, 10948. (x) Shu, X.-Z.; Liu, X.-Y.; Xiao, H.-Q.; Ji, K.-G.;
Guo, L.-N.; Qi, C.-Q.; Liang, Y.-M. Adv. Synth. Catal. 2007, 349, 2493.
(y) Liu, X.-Y.; Pan, X.-L.; Shu, X.-Z.; Duan, X.-H.; Liang, Y.-M. Synlett
2006, 12, 1962. (z) Minetto, G.; Raveglia, L. F.; Taddel, M. Org. Lett.
2004, 6, 389.
(13) For selected organocatalytic examples, see: (a) Chong, Q.; Xin,
X.; Wang, X.; Wu, F.; Wang, H.; Shi, J.-C.; Wan, B. J. Org. Chem. 2014,
79, 2105. (b) Reddy, C. R.; Reddy, M. D. J. Org. Chem. 2014, 79, 106.
(c) Yang, Y.; Ni, F.; Shu, W.-M.; Wu, A.-X. Tetrahedron 2014, 70, 6733.
(d) Dhiman, S.; Ramasastry, S. S. V. J. Org. Chem. 2013, 78, 10427.
(e) Lee, Y.-T.; Lee, Y.-T.; Lee, X.-J.; Sheu, X.-N.; Lin, B.-Y.; Wang, J.-H.;
Lin, W. Org. Biomol. Chem. 2013, 11, 5156. (f) Zheng, X.; Lu, S.; Li, Z.
Org. Lett. 2013, 15, 5432. (g) Mothe, S. R.; Lauw, S. J. L.;
Kothandaraman, P.; Chan, P. W. H. J. Org. Chem. 2012, 77, 6937.
(h) Nair, D. K.; Mobin, S. M.; Namboothiri, I. N. N. Tetrahedron Lett.
2012, 53, 3349. (i) Chen, G.; He, G.; Xue, C.; Fu, C.; Ma, S. Tetrahedron
Lett. 2011, 52, 196. (j) Kuroda, H.; Hanaki, E.; Izawa, H.; Kano, M.;
Itahashi, H. Tetrahedron 2004, 60, 1913. (k) Kuroda, H.; Hanaki, E.;
Kawakami, M. Tetrahedron Lett. 1999, 40, 3753.
(14) (a) Mothe, S. R.; Lauw, S. J. L.; Kothandaraman, P.; Chan, P. W.
H. J. Org. Chem. 2012, 77, 6937. (b) Iluc, V. M.; Fedorov, A.; Grubbs, R.
H. Organometallics 2012, 31, 39. (c) Sromek, A. W.; Rubina, M.;
Gevorgyan, V. J. Am. Chem. Soc. 2005, 127, 10500.
(15) Stephens, C. E.; Tanious, F.; Kim, S.; Wilson, W. D.; Schell, W. A.;
Perfect, J. R.; Franzblau, S. G.; Boykin, D. W. J. Med. Chem. 2001, 44,
1741.
(11) For selected reviews on furan synthesis, see: (a) Hou, X.-L.;
Cheung, H. Y.; Hon, T. Y.; Kwan, P. L.; Lo, T. H.; Tong, S. Y.; Wong, H.
N. C. Tetrahedron 1998, 54, 1955. (b) Gulevich, A. V.; Dudnik, A. S.;
Chernyak, N.; Gevorgyan, V. Chem. Rev. 2013, 113, 3084. (c) Hou, X.-
L.; Yang, Z.; Yeung, K.-S.; Wong, H. N. C. Prog. Heterocycl. Chem. 2008,
19, 176. (d) Kirsch, S. F. Org. Biomol. Chem. 2006, 4, 2076. (e) Brown, R.
C. D. Angew. Chem., Int. Ed. 2005, 44, 850. (f) Keay, B. A. Chem. Soc. Rev.
1999, 28, 209. For selected examples of reported active furan
compounds, see: (g) Reichstein, A.; Vortherms, S.; Bannwitz, S.;
Tentrop, J.; Prinz, H.; Muller, K. J. Med. Chem. 2012, 55, 7273. (h) Song,
̈
Z.-L.; Fan, C.-A.; Tu, Y.-Q. Chem. Rev. 2011, 111, 7523. (i) Dong, Y.;
Shi, Q.; Liu, Y.; Wang, X.; Bastow, K. F.; Lee, K. J. Med. Chem. 2009, 52,
3586. (j) Mortensen, D. S.; Rodriguez, A. L.; Carlson, K. E.; Sun, J.;
Katzenellenbo-gen, B. S.; Katzenellenbogen, J. J. Med. Chem. 2001, 44,
3838.
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DOI: 10.1021/acs.orglett.5b00442
Org. Lett. 2015, 17, 1557−1560