Vilsmeier-type reaction of dimethylaminoalkenoyl cyclopropanes: One-pot access to 2,3-dihydrofuro [3,2- c ]pyridin-4(5 H)-ones

Article abstract of DOI:10.1021/ol203124f

A domino reaction of readily available 1-carbamoyl-1- dimethylaminoalkenoylcyclopropanes in the presence of triflic anhydride (Tf ₂O) in N,N-dimethylformamide (DMF) is described, which provides a facile one-pot access to 2,3-dihydrofuro[3,2-c]p

Full text of DOI:10.1021/ol203124f

ORGANIC
LETTERS
2012
Vol. 14, No. 1
370–373
Vilsmeier-Type Reaction of
Dimethylaminoalkenoyl Cyclopropanes:
One-Pot Access to 2,3-Dihydrofuro
[3,2-c]pyridin-4(5H)-ones
Peng Huang, Ning Zhang,* Rui Zhang, and Dewen Dong*
Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun,
130022, China
*zhangningtum@gmail.com; dwdong@ciac.jl.cn
Received November 22, 2011
ABSTRACT
A domino reaction of readily available 1-carbamoyl-1-dimethylaminoalkenoylcyclopropanes in the presence of triflic anhydride (Tf2O) in N,
N-dimethylformamide (DMF) is described, which provides a facile one-pot access to 2,3-dihydrofuro[3,2-c]pyridin-4(5H)-ones via tandem
formylation (Vilsmeier-type reaction), intramolecular cyclization, and ring-enlargement sequences.
2,3-Dihydrofuro[3,2-c]pyridin-4(5H)-ones constitute
the core structure of many natural products and synthetic
compounds along with a broad range of bioactivities.1,2
Additionally, 2,3-dihydrofuro[3,2-c]pyridin-4(5H)-ones
can be used as versatile intermediates in organic trans-
formations to furo[3,2-c]pyridin-4(5H)-ones and other
heterocyclic systems.3 Their pharmacological and syn-
thetic importance has intrigued researchers in search of
novel furopyridones from natural products or synthetic
approaches for the construction of the skeleton of this type
of heterocycle.4 Sakemi et al. isolated many furopyridones,
e.g. CJ-16,170, from the fermentatiom broth of fungus
Cladobotryum varium CL12284, as a new type of antibio-
tics (Figure 1).5 Fukuda et al. reporteda series of citridones
A, B, B0, and C, isolated from the culture broth of
Penicillium sp. FKI-1938, which potentiate miconazole
activity against C. albicans (wide type).6 Very recently,
Liang et al. reported the synthesis of dihydrofuro[3,2-
c]pyridines from 1-carbamoyl-1-propenoyl cyclopropanes
(1) (a) Maffrand, J.-P. (Parcor) GB 2023599, 1980. (b) Surman, M. D.;
Freeman, E. E.; Grabowski, J. F.; Hadden, M.; Henderson, A. J.; Jiang, G.;
Jiang, X.; Luche, M.; Khmelnitsky, Y.; Vickers, S.; Viggers, J.; Cheetham, S.;
Guzzo, P. R. Bioorg. Med. Chem. Lett. 2010, 20, 7015–7019. (c) Xiao, D.;
Zhu, L.; Wang, S.; Liang, Z.; Hu,W. (Chemizon (BeiJing), LTD.) WO
2010/145197 A1, 2010.
(2) (a) Naito, T.; Miyata, O.; Kida, N.; Namoto, K.; Ninomiya, I.
Chem. Pharm. Bull. 1990, 38, 2419–2423. (b) New, J. S.; Christopher,
W. L.; Yevich, J. P.; Butler, R.; Schlemmer, R. F., Jr.; VanderMaelen,
C. P.; Cipollina, J. A. J. Med. Chem. 1989, 32, 1147–1156. (c) Miyazaki,
Y.; Nakano, M.; Sato, H.; Truesdale, A. T.; Stuart, J. D.; Nartey, E. N.;
Hightower, K. E.; Kane-Carson, L. Bioorg. Med. Chem. Lett. 2007
(4) (a) Conreaux, D.; Belot, S.; Desbordes, P.; Monteiro, N.; Balme, G.
J. Org. Chem. 2008, 73, 8619–8622. (b) Hyster, T. K.; Rovis, T. J. Am.
Chem. Soc. 2010, 132, 10565–10569. (c) Miyagawa, T.; Nagai, K.; Yamada,
A.; Sugihara, Y.; Fukuda, T.; Fukuda, T.; Uchida, R.; Tomoda, H.;
Omura, S.; Nagamitsu, T. Org. Lett. 2011, 13, 1158–1161. (d) Clive,
D. L. J.; Huang, X. Tetrahedron 2002, 58, 10243–10250. (c) Clive,
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Che, Q. Org. Lett. 2004, 6, 2877–2880.
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H.; Inagaki, T.; Kim, Y.-J.; Kojima, N.; Sims, J. C.; Sugie, Y.; Sugiura,
A.; Sutcliffe, J. A.; Tachikawa, K.; Truesdell, S. J.; Wong, J. W.;
Yoshikawa, N.; Kojima, Y. J. Antibiot. 2002, 55, 6–18. (b) Sugie, Y.;
Truesdell, S. J.; Wong, J. W.; Yoshikawa, N.; Sugiura, A. (Pfizer, US).
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r
10.1021/ol203124f
Published on Web 12/14/2011
2011 American Chemical Society

via a non-Brook rearrangement and halonium-initiated
cascade process, respectively.7
dehydroxylation of activated aromatic compounds or
carbonyl compounds.10,11 In our recent work, we have
demonstrated the utilization of VilsmeierꢀHaack reaction
in the synthesis of functionalized pyridin-2(1H)-ones, 1H-
pyrazoles, quinolines, and pyrimidin-4(3H)-ones.12 In the
present work, the reaction between 1-aminopropenoyl-1-
carbamoylcyclopropane 1a and a Vilsmeier reagent, POCl3/
DMF, was first attempted at rt, in which 4-chloro-3-(2-
chloroethyl)-1-phenylpyridin-2(1H)-one was obtained as
the main product. Yet, a complex mixture was formed
when the reaction was performed at elevated temperature,
e.g. 100 °C. Of note was that when 1a was treated with
another Vilsmeier reagent, i.e. triflic anhydride (Tf2O)/
DMF, at 70 °C,13 a product was obtained and character-
ized as 7-formyl-5-phenyl-2,3-dihydrofuro[3,2-c]pyridin-
4(5H)-one 2a (Scheme 1).
Figure 1. Structures of selected natural products.
During the course of our studies on β-oxo amide deri-
vatives in the synthesis of carbo- and heterocycles, we
developed convenient syntheses of substituted phenols,
cyclohexenones, 2,3-dihydro-4-pyridones, pyrrolin-4-ones,
pyrazolin-5-ones, 2H-pyrans, 4H-pyrans, and pyridin-
2(1H)-ones.8 In our recent work, we achieved the divergent
synthesis of dihydrofurans and halogenated pyridin-2(1H)-
ones from 1-aminopropenoyl-1-carbamoylcyclopropanes
derived from β-oxo amides.9
Scheme 1. Reaction of Aminopropenoyl Cyclopropane 1a with
Tf2O/DMF
In connection with these studies and following with our
interest in the synthesis of highly valuable heterocycles, we
envisioned that under appropriate conditions a tandem
ring enlargement and intramolecular cyclization of 1-ami-
noalkenoyl-1-carbamoylcyclopropanes may be realized.
Thus, the reactions of 1-carbamoyl-1-dimethylaminoalk-
enoyl cyclopropanes with Vilsmeier reagents were investi-
gated. As a result of these studies, we developed a facile
one-pot synthesis of 2,3-dihydrofuro[3,2-c]pyridin-4(5H)-
ones. Herein, we wish to report our experimental results
and a proposed mechanism involved in the domino re-
actions.
The results encouraged us to investigate the domino
reaction of 1a with other anhydrides in DMF. No reaction
was observed by subjecting 1a to acetic anhydride in DMF
at 100 °C, whereas a complex mixture was formed when
trifluoroacetic anhydride was employed as indicated by
TLC. The reaction of 1a with phosphorus(V) oxide did
proceed, but the conversion to 2a was very low. A series of
experiments revealed that the optimal results were ob-
tained when the reaction of 1a and 1.5 equiv of Tf2O was
performed in anhydrous DMF at 100 °C for 0.5 h, whereby
the yield of 2a reached 88% (Table 1, entry 1).
The VilsmeierꢀHaack reaction, due to its mild reaction
conditions, commercial viability of reagents, and the im-
proved understanding of its reaction mechanism, has been
widely used for the formylation, halogenation, and
Under the optimal conditions as in the case for 2a in
Table 1, a range of reactions of substrates 1 were carried
(7) (a) Wei, Y.; Lin, S.; Zhang, J.; Niu, Z.; Fu, Q.; Liang, F. Chem.
Commun. 2011, 47, 12394–12396. (b) Liang, F.; Lin, S.; Wei, Y. J. Am.
Chem. Soc. 2011, 133, 1781–1783.
ꢁ
(11) For selected examples, see: (a) Sayah, B.; Pelloux-Leon, N.;
ꢁ
Milet, A.; Pardillos-Guindet, J.; Vallee, Y. J. Org. Chem. 2001, 66, 2522–
2525. (b) Liu, Y.; Dong, D.; Liu, Q.; Qi, Y.; Wang, Z. Org. Biomol.
Chem. 2004, 2, 28–30. (c) Sun, S.; Liu, Y.; Liu, Q.; Zhao, Y.; Dong, D.
Synlett 2004, 1731–1734. (d) Ptaszek, M.; McDowell, B. E.; Lindsey,
J. S. J. Org. Chem. 2006, 71, 4328–4331. (e) Pinkerton, D. M.; Banwell,
M. G.; Willis, A. C. Org. Lett. 2007, 9, 5127–5130.
(12) (a) Pan, W.; Dong, D.; Wang, K.; Zhang, J.; Wu, R.; Xiang, D.;
Liu, Q. Org. Lett. 2007, 9, 2421–2423. (b) Xiang, D.; Wang, K.; Liang,
Y.; Zhou, G.; Dong, D. Org. Lett. 2008, 10, 345–348. (c) Wang, K.;
Xiang, D.; Liu, J.; Pan, W.; Dong, D. Org. Lett. 2008, 10, 1691–1694.
(d) Zhang, R.; Zhang, D.; Guo, Y.; Zhou, G.; Jiang, Z.; Dong, D. J. Org.
Chem. 2008, 73, 9504–9507. (e) Wang, Y.; Xin, X.; Liang, Y.; Lin, Y.;
Zhang, R.; Dong, D. Eur. J. Org. Chem. 2009, 4165–4169. (f) Zhang, R.;
Zhang, D.; Liang, Y.; Zhou, G.; Dong, D. J. Org. Chem. 2011, 76, 2880–
2883.
(13) Treatment of Tf2O with a secondary amide can generate imi-
nium triflate, which can be regarded as a Vilsmeier-type reagent. See:
(a) Martinez, A. G.; Alvarez, R. M.; Barcina, J. O.; Cerero, S. M.; Vilar,
E. T.; Fraile, A. G.; Hanack, M.; Subramanian, L. R. J. Chem. Soc.,
Chem. Commun. 1990, 1571–1572. (b) Nenajdenko, V. G.; Baraznenok,
I. L.; Balenkova, E. S. Tetrahedron Lett. 1996, 37, 4199–4202.
(c) Kobayashi, Y.; Nakatani, T.; Tanaka, R.; Okada, M.; Torii, E.;
Harayama, T.; Kimachi, T. Tetrahedron 2011, 67, 3457–3463.
(8) (a) Bi, X.; Dong, D.; Liu, Q.; Pan, W.; Zhao, L.; Li, B. J. Am.
Chem. Soc. 2005, 127, 4578–4579. (b) Dong, D.; Bi, X.; Liu, Q.; Cong, F.
Chem. Commun. 2005, 3580–3582. (c) Bi, X.; Dong, D.; Li, Y.; Liu, Q.;
Zhang, Q. J. Org. Chem. 2005, 70, 10886–10889. (d) Huang, J.; Liang,
Y.; Pan., W.; Yang, Y.; Dong, D. Org. Lett. 2007, 9, 5345–5348.
(e) Wang, K.; Fu, X.; Liu, J.; Liang, Y.; Dong, D. Org. Lett. 2009, 11,
1015–1018. (f) Wang, Y.; Xin, X.; Liang, Y.; Lin, Y.; Duan, H.; Dong,
D. Adv. Synth. Catal. 2009, 351, 2217–2223.
(9) (a) Zhang, R.; Liang, Y.; Zhou, G.; Wang, K.; Dong, D. J. Org.
Chem. 2008, 73, 8089–8092. (b) Zhang, R.; Zhou, Y.; Liang, Y.; Jiang,
Z.; Dong, D. Synthesis 2009, 2497–2500.
(10) For reviews, see: (a) Jones, G.; Stanforth, S. P. The Vilsmeier
Reaction of Fully Conjugated Carbocycles and Heterocycles. In Organic
Reactions; Paquette, L. A., Ed.; John Wiley: New York, 1997; Vol. 49, pp
1ꢀ330. (b) Marson, C. M.; Giles, P. R. Synthesis Using Vilsmeier
Reagents; CRC Press: Boca Raton, FL, 1994; pp 1ꢀ247. (c) Marson,
C. M. Tetrahedron 1992, 48, 3659–3726.
Org. Lett., Vol. 14, No. 1, 2012
371

characterized as 7-azaspiro[4.5]dec-8-ene-6,10-dione 3a
(Table 2, entry 1). In the same fashion, a range of reactions
of 1-aminopropenoyl-1-carbamoylcyclopentanes 1 bear-
ing variable N-aryl and alkyl groups were carried out, and
the corresponding 7-azaspiro[4.5]dec-8-ene-6,10-diones
3bꢀg were obtained in high yields (Table 2, entries 2ꢀ7).
In the cases of substrates 5-amino-2,2-dialkyl-3-oxo-pent-
4-enamides 1t and 1u, pyridine-2,4(1H,3H)-diones 3h and
3i were obtained, respectively (Table 2, entries 8 and 9).
These results suggested that the cyclization of 1mꢀu
might proceed in the same manner as 1-alkenoyl-1-carba-
moylcyclopropanes 1aꢀl did in the presence of Tf2O in
DMF.
Table 1. Synthesis of 2,3-Dihydrofuro[3,2-c]pyridin-4(5H)-ones
2 from 1a
entry
1
R1
R2
R3
2
yield (%)b
1
1a
1b
1c
1d
1e
1f
Ph
H
H
H
H
H
H
H
H
H
H
Ph
H
H
H
H
H
H
H
H
H
H
H
H
Me
2a
2b
2c
2d
2e
2f
88
86
90
85
90
92
85
87
82
83
85
71
2
2-MeC6H4
4-MeC6H4
2,4-Me2C6H3
2-MeOC6H4
4-MeOC6H4
2-ClC6H4
4-ClC6H4
4-CF3C6H4
Bn
3
4
5
Table 2. Synthesis of Pyridine-2,4(1H,3H)-diones 3a
6
7
1g
1h
1i
2g
2h
2i
8
9
10
11
12
1j
2j
1k
1l
4-MeC6H4
Ph
2k
2l
entry
1
R1
R (or R.....R)
3
yield (%)b
a Reagents and conditions: 1 (1.0 mmol), Tf2O (1.5 mmol), DMF
(anhydrous, 5.0 mL), 100 °C, 0.5ꢀ1.0 h. b Isolated yields.
1
2
3
4
5
6
7
8
9
1m
1n
1o
1p
1q
1r
Ph
(CH2)4
(CH2)4
(CH2)4
(CH2)4
(CH2)4
(CH2)4
(CH2)4
Me
3a
3b
3c
3d
3e
3f
91
87
90
86
83
87
82
85
84
2-MeC6H4
4-MeC6H4
2-MeOC6H4
2-ClC6H4
4-ClC6H4
Bn
out aiming to determine the scope of the furo[3,
2-c]pyridin-4(5H)-one synthesis, and some of the results
are summarized in Table 1. It was found that the reactions
of 1bꢀj bearing variable aryl and alkyl amide groups
could proceed efficiently to afford the corresponding 2,
3-dihydrofuro[3,2-c]pyridin-4(5H)-ones 2bꢀj in high yields
(Table 1, entries 2ꢀ10). In the case of substrate 1k with a
phenyl group on its cyclopropane ring, the reaction furni-
shed the corresponding 2,3-dihydrofuro[3,2-c]pyridin-
4(5H)-one 2k as a single regioisomer, which suggested that
the ring enlargement of the cyclopropyl moiety occurred in
a high regioselective manner (Table 1, entry 11). The
versatility of this furo[3,2-c]pyridin-4(5H)-one synthesis
was further evaluated by performing the reaction of
1-aminobutenoyl-1-carbamoyl cyclopropane 1l under the
identical conditions (Table 1, entry 12). It was worth
noting that 2,3-dihydrofuro[3,2-c]pyridin-4(5H)-one 2l
with an acetyl group on the pyridone ring rather than a
formylgroup was exclusivelyobtained ingood yield, which
also gave a piece of evidence for the mechanism of the
domino reaction. The results shown above have demon-
strated the efficiency and interest of the cyclization reac-
tion for the synthesis of 2,3-dihydrofuro[3,2-c]pyridin-
4(5H)-ones 2 with respect to substrates 1 bearing variable
substituted groups, i.e. R1, R2, and R3. Therefore, we have
provided a facile synthesis of substituted furo[3,2-c]pyridin-
4(5H)-one of type 2.
1s
3g
3h
3i
1t
Ph
1u
Ph
Et
a Reagents and conditions: 1 (1.0 mmol), DMF (anhydrous, 5.0 mL),
Tf2O (1.5 mmol), 100 °C, 0.5ꢀ1.0 h. b Isolated yields.
To gain insight into the mechanism of the furo[3,2-c]
pyridin-4(5H)-one synthesis from 1-aminoalkenoyl-1-car-
bamoylcyclopropanes, a separatedreaction of1aand Tf2O
(1.5 equiv) was conducted in DMF-d7 at 100 °C,14 and
deuterated product 2a-D and 2a were obtained in a 86%
yield with a molar ratio of 9:1 (Scheme 2; see Supporting
Information). The structure of 2a-D was established by
comparison of its NMR spectra with those of 2a. In the 1H
NMR spectrum, 2a displayed two single peaks at 9.81 and
8.02 ppm, which were assigned to formyl-H and 6-H from
the furo[3,2-c]pyridin-4(5H)-one ring, respectively. With
respect to 2a-D, the peak at 8.02 ppm for 6-H disappeared,
indicating the formylation should occur on the N-atom of
the amide moiety. In the 13C NMR spectrum, the formyl-C
and 6-C of 2a were indicated at 184.6 and 145.6 ppm,
respectively. As for 2a-D, there was almost no change on
the chemical shifts of these two peaks, but the intensity of
the peak at 145.6 became weaker, which is consistent with
1
The above findings inspired us to examine the reaction
behavior of analogous 1-aminopropenoyl-1-carbamoyl
cyclopentanes 1 under identical conditions. Thus, carba-
moylcyclopentane 1m and Tf2O (1.5 equiv) were subjected
to anhydrous DMF at 100 °C. To our delight, the reaction
proceeded smoothly and furnished a product, which was
the above H NMR results. The fact that 2a appeared
within this system might be attributed to the small amount
of nondeuterated DMF in the reaction medium.
(14) Reagents and conditions: 1a (0.5 mmol), Tf2O (0.75 mmol),
DMF-d7 (99.5%, 1.0 mL), 100 °C, 0.5 h.
372
Org. Lett., Vol. 14, No. 1, 2012

Scheme 2. Reaction of Aminopropenoyl Cyclopropane 1a with
Tf2O/DMF-d7
Scheme 3. Plausible Mechanism for the Domino Reaction of 1
with Tf2O/DMF
On the basis of the above experimental results together
with some literature reports, a plausible mechanism for the
synthesis of 2,3-dihydrofuro[3,2-c]pyridin-4(5H)-ones 2 is
proposed as depicted in Scheme 3 (with the reaction of 1a
in DMF-d7 as an example). The secondary amide DMF-d7
is activated with Tf2O to generate a very reactive iminium
triflate I,15ꢀ17 which can be regarded as a Vilsmeier-type
reagent. Mediated by I, substrate 1a undergoes formyla-
tion to afford iminium salt II. Followed by a tandem
intramolecular cyclization reaction10,12a,12b and ring-
enlargement reaction,18 II sheds dimethylamine to give rise
to iminium intermediate V, which is finally converted into
2,3-dihydrofuro[3,2-c]pyridin-4(5H)-one 2a-D upon
treatment with water.
In summary, a facile and efficient access to substituted
2,3-dihydrofuro[3,2-c]pyridin-4(5H)-ones 2 is developed via a
domino reaction of readily available 1-aminoalkenoyl-1-car-
bamoylcyclopropanes in the presence of Tf2O in DMF. The
Vilsmeier-type reaction was further utilized for the synthesis
of spiro or substituted pyridine-2,4(1H,3H)-diones 3 from
1-aminoalkenoyl-1-carbamoylcyclopentanes and 5-ami-
no-2,2-alkyl-3-oxo-pent-4-enamides, respectively. The
one-pot protocol is associated with readily available sub-
strates, mild conditions, high yields, and a wide range
of products with synthetic potential. Further work on
the reaction mechanism and extension of the scope of
the present protocol is currently underway in our
laboratory.
(15) For pioneering studies on iminium triflate, see: (a) Falmagne,
J. B.; Escudero, J.; Taleb-Saharaoui, S.; Ghosez, L. Angew. Chem., Int.
Ed. Engl. 1981, 20, 879–880. (b) Barbaro, G.; Battaglia, A.; Bruno, C.;
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Chem. Soc. 1929, 51, 1174–1187. (b) Wong, H. N. C.; Hon, M. Y.; Tse,
C. W.; Yip, Y. C. Chem. Rev. 1989, 89, 165–198. (c) Yadav, V. K.;
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Acknowledgment. Financial support of this research
by the National Natural Science Foundation of China
(20872136 and 21172211) is greatly acknowledged.
Supporting Information Available. Experimental de-
tails, full characterization data, and copies of NMR
spectra for compounds 2 and 3. This materials are avail-
able free of charge via the Internet at http://pubs.acs.org.
Org. Lett., Vol. 14, No. 1, 2012
373