Unprecedented acceleration of the domino reaction between methyl 4-hydroxyalk-3-ynoates and amines in ionic liquids

Article abstract of DOI:10.1016/j.mencom.2011.03.012

Reaction between methyl 4-hydroxyalk-3-ynoates and amines leading to 4-aminofuran-2(5H)-ones is significantly accelerated in ionic liquids, which can be recycled at least five times.

Full text of DOI:10.1016/j.mencom.2011.03.012

Mendeleev
Communications
Mendeleev Commun., 2011, 21, 94–96
Unprecedented acceleration of the domino reaction between
methyl 4-hydroxyalk-3-ynoates and amines in ionic liquids
Nina I. Simirskaya,a Nikolai V. Ignat’ev,b Michael Schulteb and Sergei G. Zlotin*a
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.
Fax: +7 499 135 5328; e-mail: zlotin@ioc.ac.ru
b Merck KGaA, PC-RL, D-64293 Darmstadt, Germany
DOI: 10.1016/j.mencom.2011.03.012
Reaction between methyl 4-hydroxyalk-3-ynoates and amines leading to 4-aminofuran-2(5H)-ones is significantly accelerated in
ionic liquids, which can be recycled at least five times.
The butenolide [furan-2(5H)-one] fragment is an integral part of
a variety of biologically active compounds and natural products
such as vitamin C, steroids, pheromones, acetogenins, digitoxin
and related cardenolides.1,2 Commonly, it is formed by multi-step
reaction sequences, which require the use of absolute solvents
and/or expensive reagents.3–6 Examples of more efficient one-pot
synthetic procedures are scarce. Among them there is a reaction
of methyl 4-hydroxyalk-3-ynoates 1 with secondary amines 2
that includes aza-Michael addition of amines 2 to activated triple
bond of 1 followed by the lactonisation of thus in situ generated
adducts 3 (Scheme 1).7 This reaction is a convenient protocol for
the synthesis of 4-aminobut-2-en-4-olides 4, which are versatile
intermediates for the preparation of various furan-2(5H)-ones.
However, it runs slowly (1–10 days) in organic solvents (diethyl
ether, alcohols, acetone, dioxane, etc.).
Table 1 Reaction between compounds 1a and 2b.a
O
N
Solvent
OMe
+
NH
O
O
OH
2b
1a
4b
Entry
Solvent
T/°C
t/h
Yield of 4b (%)
1
2
3
4
[bmim][BF4]
[bmim][PF6]
[hmim][PF3(C2F5)3]
[bmpl][TfO]
[bmpl][NTf2]
Et2O
Et2O
neat
neat
20
20
20
20
20
20
20
20
100
1
1
1
1
1
140
140
22
4
85
80
82
73
85
67
64
58
62
5
6b
7c
8
R3
O
R3R4NH
N
O
R1
R2
R4
9b
OMe
2
R1
R2
OMe
aThe reactions were carried out with 1a (1 mmol), 2b (1.5 mmol) and the
indicated solvent (3 mmol for entries 1–5 or 6 ml for entry 6). bData according
to ref. 7(a). cThe reaction was carried out in the presence of HCl (cat.).
OH
OH
3
1
R3
R4
R1
R2
N
1-butyl-3-methylpyrrolidinium triflate [bmpl][TfO] and bis(triflyl)-
amide [bmpl][NTf2] were used as ILs. In all cases 4-aminofuran-
2(5H)-one 4b was formed much faster, at lower temperature and
in improved yield than in Et2O or under solvent-free conditions
(Table 1). This acceleration cannot be caused by acidic impurities
in ILs because they (if any) should be instantly neutralized by
the amine 2b taken in excess. Furthermore, the addition of cata-
lytic amount of HCl did not influence the same reaction in Et2O
(Table 1, entry 7).
Then, the least expensive IL [bmim][BF4], in which butenolide
4b was obtained in high yield (85%), was applied to reactions
between various alkynes 1 and amines 2 (Table 2).† Alkynes
containing cyclohexanol (entries 1–11, 16–19), cyclopentanol
(entries 12, 13), propan-2-ol (entry 14) and butan-2-ol (entry 15)
– MeOH
O
O
4
Scheme 1
Taking into account that reactants 1 and 2 as well as inter-
mediates 3 are polar molecules, we anticipated that the reaction
would run faster in ionic liquids (ILs) that have attracted atten-
tion over the last decade as neoteric solvents and catalysts in the
organic synthesis.8–12 In particular, they promote reactions of
nucleophiles with compounds bearing electron-deficient double
bonds C=C13–20 or C=O,21–24 among them a cascade reaction that
includes a lactonisation stage.24 However, to the best of our
knowledge, ILs have not so far been applied to Michael addi-
tions involving electron-deficient alkynes.
First, we studied a model reaction between alkyne 1a and pipe-
ridine 2b in various ILs and compared the obtained results with
those attained earlier in Et2O and under neat conditions. Commer-
cial 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4]
and hexafluorophosphate [bmim][PF6], 1-hexyl-3-methylimidazo-
lium tris(pentafluoroethyl) trifluorophosphate [hmim][PF3(C2F5)3],
†
Typical procedure. A mixture of alkyne 1 (1.0 mmol), amine 2 (1.5 mmol)
and IL (3 mmol) or organic solvent (6 ml) was stirred under the conditions
specified in Tables 1 and 2 and successively extracted with light petroleum
(40–70°C) (5 ml), the Et2O–light petroleum mixture (1:1) (5 ml) and Et2O
(5 ml). The combined extracts were passed through a silica gel pad, solvents
were evaporated in vacuo (15 Torr) and the residue was crystallized or
purified by column chromatography on silica gel (Acros, 40–60 mm). In
the case of compounds 4j,r,s, reaction mixtures were diluted with water
(3 ml) and precipitated products were filtered off and recrystallized.
© 2011 Mendeleev Communications. All rights reserved.
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Mendeleev Commun., 2011, 21, 94–96
Table 2 Synthesis of 4-aminofuran-2(5H)-one derivatives 4 from compounds 1 and 2 in [bmim][BF4].
Entry
Product
R1
R2
R3
R4
T/°C (lit.)
t/h (lit.)
Yield (%) (lit.)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
4a
4b
4c
4d
4e
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)4–
–(CH2)4–
–(CH2)4–
–(CH2)5–
–(CH2)6–
20 (20a)
1 (48a)
1 (140a, 4b)
1 (48a)
1 (140a)
4 (48a, 7c)
2 (250a)
8 (6c)
6 (140a)
2 (12c)
80 (73a)
85 (67a, 62b)
88 (53a)
85 (72a)
90 (59a, 47c)
87 (82a)
86 (62c)
80 (71a)
20 (20a, 100b)
30 (20a)
–(CH2)2O(CH2)2–
–(CH2)2N(Me)(CH2)2–
–CH(Me)(CH2)4–
–(CH2)2N[C(O)Ph](CH2)2–
–(CH2)2N(CO2Et)(CH2)2–
2 = imidazole
2 = (S)-anabasine
2 = (S)-cytisine
–(CH2)5–
–(CH2)2N(Me)(CH2)2–
–(CH2)4–
20 (20a)
40 (20a, 65c)
20 (20a)
4f
4g
4h
4i
20 (65c)
20 (20a)
60 (65c)
18 + 52d (35 + 8c,d
99 (62c, 74e)
70 (64g)
)
4j
20 (65c, 100e)
20 (20g)
6 (20c, 12e)
8 (150g)
1 (48h)
4kf
4lf
4mf
4nf
4of
4pf
4q
4r
20 (20h)
95 (65h)
20 (20h)
1 (45h)
96 (60h)
Me
Me
Me
Et
20 (20h)
1 (48h)
88 (66h)
–(CH2)4–
Me2CH(CH2)2
20 (20h)
1 (48h)
90 (68h)
–(CH2)5–
–(CH2)5–
–(CH2)5–
–(CH2)5–
Me2CH(CH2)2
Bn
Bn
CH(Me)Ph
20 (20g)
5 (25g)
88 (60g)
Bn
H
H
20 (20a)
4 (250a)
3 (24c, 8e)
8 (12a)
82 (78a)
20 (20c, 100e)
20 (20a)
80 (70c, 67e)
70 (58a)
4s
aSolvent – Et2O, data according to ref. 7(a). bNeat conditions, data according to ref. 7(a). cSolvent – MeOH, data according to ref.7(a). dYield of compound 3i.
eSolvent – BuOH, data according to ref. 7(b). fNew compounds. gSolvent – Et2O/MeOH (2:1, v/v). hSolvent – Et2O.
fragments acted as Michael acceptors. Cyclic amines (entries
1–15), in particular alkaloids (entries 10, 11), as well as acyclic
secondary (entries 16, 17) or primary (entries 18, 19) amines
were used as nucleophiles.
organic solvents as well and became convinced that the IL medium
gave much better results in terms of both the product yield and
the reaction rate (Table 2). Positive IL impact may be attributed
to ion–dipole interactions in the IL medium, which facilitate the
charge separation in compounds 1 and/or 3 and promote reactions
(Figure 1).
As a rule, yields of corresponding butenolides 4a–s were
close or higher than those reported in literature. Furthermore,
the reaction time was much shorter in the IL medium than that in
traditional organic solvents (TLC monitoring). The sole exception
was the reaction between alkyne 1a and imidazole (entry 9), in
which furan derivative 4i was formed in only 18% yield and the
major product was enamine 3i.‡ We succeeded in synthesizing
several new compounds in the IL medium, in particular (S)-cytisine-
derived butenolide 4k (entry 11) and compounds 4l–p (entries
12–16).§ For comparison, we synthesized these compounds in
2.6 (s, 1H, H7-cytisine), 3.15 (s, 1H, H9-cytisine), 3.30 (d, 2H, H10-cytisine,
J 12.5 Hz), 3.65–3.95 (m, 3H, NCH2), 4.20 (d, 1H, NCH2, J 12.5 Hz), 4.60
(s, 1H, =CH), 6.07 (d, 1H, H5-cytisine, J 10.4 Hz), 6.46 (d, 1H, H3-cytisine,
J 12.5 Hz), 7.31 (t, 1H, H4-cytisine, J 10.4 Hz). Found (%): C, 70.81;
H, 7.17; N, 8.09. Calc. for C20H24N2O3 (%): C, 70.56; H, 7.11; N, 8.23.
ChiralcelAD-H, eluent hexane–PriOH (1:1), 0.8 ml min–1, 220 nm, reten-
tion time 8.5 min (single); eluent hexane–PriOH (7:3), 0.8 ml min–1, 220 nm,
retention time 16.1 min (single).
4-Piperidino-1-oxaspiro[4.4]non-3-en-2-one 4l: white solid, 0.25 g (95%),
‡
Synthesis of compounds 3i and 4i. A mixture of alkyne 1a (0.18 g,
1
mp 110–111°C. IR (KBr, n/cm–1): 1722 (C=O), 1596 (C=C). H NMR
1.0 mmol), imidazole (0.12 g, 1.5 mmol) and [bmim][BF4] (0.69 g, 3.0 mmol)
was stirred at 60°C for 2 h, cooled to ambient temperature and successively
extracted with light petroleum (5 ml), light petroleum–diethyl ether (1:10)
(5 ml) and light petroleum–benzene (1:1) (5 ml). The combined extracts
were evaporated to a half volume, the precipitated solid was filtered off
and crystallized from the light petroleum–Et2O–EtOAc–CHCl3 (5:5:2:1)
mixture to afford methyl 3-(1-hydroxycyclohexyl)-3-(1H-imidazol-1-yl)-
acrylate 3i, yellowish solid, 0.13 g (52%), mp 110–111°C. IR (KBr,
n/cm–1): 1660, 1732, 3112. 1H NMR (300 MHz, DMSO-d6) d: 0.95–1.75
(m, 10H, CH2, cyclohexyl), 3.50 (s, 3H, OMe), 5.25 (s, 1H, OH), 6.35 (s,
1H, =CH), 6.90, 7.20, 7.45 (3s, 1H each, imidazole). Found (%): C, 62.61;
H, 7.13; N, 10.98. Calc. for C13H18N2O3 (%): C, 62.38; H, 7.25; N,11.19.
Evaporation of mother liquor afforded 4-(1H-imidazol-1-yl)-1-oxaspiro-
[4.5]dec-3-en-2-one 4i, white solid, 40 mg (18%), mp 180–181°C. IR (KBr,
n/cm–1): 1632, 1748, 3148. 1H NMR (300 MHz, DMSO-d6) d: 1.43–1.85
(m, 10H, CH2, cyclohexyl), 6.52 (s, 1H, =CH), 7.21, 7.89, 8.50 (3s, 1H each,
imidazole). Found (%): C, 66.27; H, 6.68; N, 12.57. Calc. for C12H14N2O2
(%): C, 66.04; H, 6.47; N, 12.84.
(300 MHz, CDCl3) d: 1.56–1.90 (m, 4H, CH2), 1.90–2.18 (m, 6H, CH2,
piperidine), 3.19–3.37 (m, 4H, NCH2, piperidine), 4.61 (s, 1H, =CH).
Found (%): C, 70.31; H, 8.79; N, 6.15. Calc. for C13H19NO2 (%): C, 70.55;
H, 8.65; N, 6.33.
4-(4-Methylpiperazin-1-yl)-1-oxaspiro[4.4]non-3-en-2-one 4m: white
solid, 0.23 g (96%), mp 109–110°C. IR (KBr, n/cm–1): 1722 (C=O), 1588
1
(C=O). H NMR (300 MHz, CDCl3) d: 1.69–2.15 (m, 8H, CH2, cyclo-
pentyl), 2.42 (s, 3H, NMe), 2.48, 3.33 (2t, 4H each, NCH2, J 4.6 Hz),
4.63 (s, 1H, =CH). Found (%): C, 66.25; H, 8.61; N, 11.64. Calc. for
C13H20N2O2 (%): C, 66.07; H, 8.53; N, 11.86.
5,5-Dimethyl-4-pyrrolidinofuran-2(5H)-one 4n: yellowish solid, 0.16 g
(88%), mp 105–106°C. IR (KBr, n/cm–1): 1722 (C=O), 1588 (C=C). 1H NMR
(300 MHz, CDCl3) d: 1.6 (s, 6H, Me), 1.92–2.09 (m, 4H, CH2, pyrro-
lidine), 3.38 (br.s, 4H, NCH2), 4.38 (s, 1H, =CH). Found (%): C, 65.92;
H, 8.39; N, 7.58. Calc. for C10H15NO2 (%): C, 66.27; H, 8.34; N, 7.73.
5-Methyl-5-ethyl-4-pyrrolidinofuran-2(5H)-one 4o: white solid, 0.17 g
(90%), mp 65–66°C. IR (KBr, n/cm–1): 1722 (C=O), 1588 (C=C). 1H NMR
(300 MHz, CDCl3) d: 0.8 (t, 3H, CH2Me, J 7.4 Hz), 1.51 (s, 3H, CMe),
1.83 (sept., 2H, CH2Me, J 7.4 Hz), 1.85–2.05 (m, 4H, CH2 cycl.), 3.36 (br.s,
4H, NCH2), 4.37 (s, 1H, =CH). Found (%): C, 67.89; H, 8.64; N, 6.95.
Calc. for C11H17NO2 (%): C, 67.66; H, 8.78; N, 7.17.
4-[Bis(4-methylbutyl)amino]-1-oxaspiro[4.5]dec-3-en-2-one 4p: white
solid, 0.24 g (88%), mp 92–93°C. IR (KBr, n/cm–1): 1720 (C=O), 1590
(C=C). 1H NMR (300 MHz, CDCl3) d: 0.95 (d, 12H, Me, J 6.4 Hz),
1.05–2.00 (m, 14H, CH2), 2.1 (sept., 2H, CH, J 6.5 Hz), 3.1 (d, 4H, NCH2,
J 7.6 Hz), 4.47 (s, 1H, =CH). Found (%): C, 73.88; H, 10.68; N, 4.89.
Calc. for C19H33NO2 (%): C, 74.22; H, 10.81; N, 4.56.
§
4-[(S)-2-(3-Pyridyl)piperidin-1-yl]-1-oxaspiro[4.5]dec-3-en-2-one
4j: white solid, 0.31 g (99%), mp 220.5–222°C (lit.,7(b) 221–222°C),
[a]D20 –169 (c 0.47, CHCl3), Chiralcel AD-H, eluent hexane–PriOH (1:1),
0.8 ml min–1, 254 nm, retention time 8.2 min (single); eluent hexane–
PriOH (7:3), 0.8 ml min–1, 254 nm, retention time 9.9 min (single).
(1R,5S)-3-(2-Oxo-1-oxaspiro[4.5]dec-3-en-4-yl)-1,2,3,4,5,6-hexa-
hydro-8H-1,5-methanopyrido[1,2-a][1,5]diazocin-8-one 4k: white solid,
0.24 g (70%), mp 285–287°C (decomp.), [a]D20 –413 (c 0.45, CHCl3).
IR (KBr, n/cm–1): 1740 (C=O), 1630 (C=C). 1H NMR (300 MHz, CDCl3)
d: 0.98–1.98 (m, 10H, CH2, cyclohexyl), 1.98–2.24 (m, 2H, H8-cytisine),
– 95 –

Mendeleev Commun., 2011, 21, 94–96
3 (a) J. S. Clark, F. Marlin, B. Nay and G. Wilson, Org. Lett., 2003, 5, 89;
R4
N
(b) P. Plastina, B. Gabriele and G. Salerno, Synthesis, 2007, 19, 3083;
(c) Y.-J. Li, G.-M. Ho and P.-Z. Chen, Tetrahedron: Asymmetry, 2009,
20, 1854.
Cat
Cat
O
R3
R1
R1
R2
O
4 (a) W. Jie, J. Xin, C. Ming, G. Zongming, H. Yuefei and H. Hongwen,
J. Chem. Soc., Perkin Trans. 1, 2001, 66; (b) A. Arcadi, M. Alfonsi and
F. Marinelli, Tetrahedron Lett., 2009, 50, 2060.
O
R2
O
H
Me
H
O
OMe
An
5 (a) B. Gabriele, G. Salerno, P. Plastina, M. Costa and A. Crispini, Adv.
Synth. Catal., 2004, 346, 351; (b) Y.-L. Li, P.-T. Lee, C. M. Yang, Y.-K.
Chang, Y.-C. Weng and Y.-H. Liu, Tetrahedron Lett., 2004, 45, 1865.
6 (a) I. Pevet, C. Meyer and J. Cossy, Synlett, 2003, 663; (b) H. Bruyere,
S. Samaritani, A. Tomas and J. Royer, Synlett, 2005, 1421; (c) A. Saabani,
A. Sarvany, S. Keshipour, A. H. Rezayan and R. Ghadani, Tetrahedron,
2010, 66, 1911; (d) H. Bruyere, D. R. Catarina, S. Samaritani, S. Ballereau
and J. Royer, Synthesis, 2006, 10, 1673.
1·IL
An
3·IL
Figure 1 A plausible charge separation in compounds 1 and 3 in the IL
medium.
7 (a) M. V. Mavrov and N. I. Simirskaya, Khim. Geterotsikl. Soedin., 1999,
1330 [Chem. Heterocycl. Compd. (Engl. Transl.), 1999, 35, 1150]; (b) M.V.
Mavrov, N. I. Simirskaya, L. D. Konyushkin and S. G. Zlotin, Izv. Akad.
Nauk, Ser. Khim., 2005, 2761 (Russ. Chem. Bull., Int. Ed., 2005, 54, 2857);
(c) N. Ignatyev, S. G. Zlotin and N. I. Simirskaya, WO 2010/108584A1,
30.09.2010.
According to HPLC (Chiralcel AD-H, eluent n-hexane/PriOH
1:1–7:3) the obtained chiral compounds 4j and 4k were indivi-
dual enantiomers. Their specific optical rotations remained high
{[a]D20 –169 (c 0.47, CHCl3) for 4j and –413 (c 0.45, CHCl3) for
4k} irrespective of the reaction period (6–24 h), the fact testifying
against the racemisation of chiral centers in the IL medium.
The recyclability of IL [bmim][BF4] was demonstrated in
the syntheses of butenolides 4b,l,m. After the extraction of the
products, portions of the reactants 1 and 2 were added to the
remaining IL and the reactions were re-performed. Reaction rates
and product yields remained the same over at least five reaction
cycles (Table 3).
8
Ionic Liquids in Synthesis, 1, eds. P. Wasserscheid and T. Welton, Wiley-
VCH, Weinheim, 2008.
9
Ionic Liquids in Synthesis, 2, eds. P. Wasserscheid and T. Welton, Wiley-
VCH, Weinheim, 2008.
10 I. Parvulescu and C. Hardacre, Chem. Rev., 2007, 107.
11 J. Durand, E. Teuma and M. Gómez, C. R. Chimie, 2007, 10, 152.
12 (a) S. G. Zlotin and N. N. Makhova, Mendeleev Commun., 2010, 20, 63;
(b) S. G. Zlotin and N. N. Makhova, Usp. Khim., 2010, 79, 603 (Russ.
Chem. Rev., 2010, 79, 543).
13 (a) B. C. Ranu and S. Banerjee, Org. Lett., 2005, 7, 3049; (b) J.-M. Xu,
C. Qian, B.-K. Liu, Q. Wu and X.-F. Lin, Tetrahedron, 2007, 63, 986.
14 L. Lin, L.-W. Xu, W. Zhou, L. Li and C.-G. Xia, Tetrahedron Lett., 2006,
47, 7723.
Table 3 Recyclability of the IL in the studied reactions.a
Product
Yield (%) (cycle)
15 N. Karodia, X. Liu, P. Ludley, D. Pletsas and G. Stevenson, Tetrahedron,
4b
4l
4m
85 (1), 87 (2), 90 (3), 90 (4), 90 (5)
95 (1), 96 (2), 94 (3), 95 (4), 95 (5)
96 (1), 96 (2), 97 (3), 96 (4), 95 (5)
2006, 62, 11039.
16 X. Xia, S. Cui and Y. Wang, Lett. Org. Chem., 2006, 3, 414.
17 J. S.Yadav, B. V. S. Reddy, G. Baishya, K. V. Reddy and A. V. Narsaiah,
Tetrahedron, 2005, 61, 9541.
aThe reactions were carried out with 1 (1 mmol), 2 (1.5 mmol) and
[bmim][BF4] (3 mmol) at 20°C for 1 h.
18 W.-J. Li, X.-F. Lin, J. Wang, G.-L. Li and Y.-G. Wang, Synlett, 2005,
2003.
19 M. L. Kantam, V. Neeraja, B. Kavita, B. Neelima, M. K. Chaudhuri and
S. Hussain, Adv. Synth. Catal., 2005, 347, 763.
20 L.-W. Xu, L. Li, C.-G. Xia, S.-L. Zhou and J.-W. Li, Tetrahedron Lett.,
In conclusion, we have discovered that ionic liquids are solvents
of choice for Michael additions of N-nucleophiles to activated
alkynes. Their application allowed the time of the domino reac-
tion between methyl 4-hydroxyalk-3-ynoates and amines afford-
ing 4-aminofuran-2(5H)-ones to become 10–30-fold shorter than
that in traditional organic solvents. Moreover, ionic liquids can
be recovered and reused at least five times without any decrease
in reaction rates and product yields.
2004, 45, 1219.
21 F. Zhang, D.-Q. Xu, S.-P. Luo, B.-Y. Liu, X.-H. Du and Z.-Y. Xu, J. Chem.
Res., 2004, 773.
22 A. Kamal and G. Chouhan, Adv. Synth. Catal., 2004, 346, 579.
23 H.-P. Nguyen, S. Znifeche and M. Baboulene, Synth. Commun., 2004,
34, 2085.
24 D.Villemin, B. Mostefa-Kara, N. Bar, N. Choukchou-Braham, N. Cheikh,
A. Benmeddah, H. Hazimeh and C. Ziani-Cherif, Lett. Org. Chem., 2006,
3, 558.
This work was supported by Merck KGaA, Darmstadt,
Germany.
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Received: 21st October 2010; Com. 10/3614
– 96 –