Synthesis of fully functionalized iminolactones via an isocyanide-based three-component reaction

Article abstract of DOI:10.1007/s13738-013-0386-2

An efficient method has been developed for the one-pot synthesis of fully functionalized iminolactones containing pyran-furan moiety. The zwitterion formed from an alkyl or an aryl isocyanide and a dialkyl acetylenedicarboxylate reacts with 3-acetyl-6-methyl-3H-pyran-2,4-dione to form 2,5-dihydro-2-(3,4- dihydro-6-methyl-2,4-dioxo-2H-pyran-3-yl)-2-methyl-5-(methylimino)furan-3, 4-dicarboxylates in relatively good yields at room temperature without using any catalyst.

Full text of DOI:10.1007/s13738-013-0386-2

J IRAN CHEM SOC (2014) 11:1183–1187
DOI 10.1007/s13738-013-0386-2
ORIGINAL PAPER
Synthesis of fully functionalized iminolactones
via an isocyanide-based three-component reaction
•
Ahmad Shaabani Mojtaba Mahyari
•
•
Fatemeh Hajishaabanha Hamid Mofakham
Received: 2 November 2013 / Accepted: 21 November 2013 / Published online: 5 December 2013
Ó Iranian Chemical Society 2013
Abstract An efficient method has been developed for the
one-pot synthesis of fully functionalized iminolactones
containing pyran–furan moiety. The zwitterion formed
from an alkyl or an aryl isocyanide and a dialkyl acety-
lenedicarboxylate reacts with 3-acetyl-6-methyl-3H-pyran-
2,4-dione to form 2,5-dihydro-2-(3,4-dihydro-6-methyl-
2,4-dioxo-2H-pyran-3-yl)-2-methyl-5-(methylimino)furan-
3,4-dicarboxylates in relatively good yields at room tem-
perature without using any catalyst.
Furan and pyran rings are important five- and six-
membered O-heterocycles in natural compounds [12–14]
with various industrial applications [15, 16] and biological
activities [17, 18]. They are also used as intermediates in
the synthesis of pharmaceutical compounds [19–21].
Recently, the combinations of annulated heterocyclic
structures for obtaining polycyclic skeletons with diverse
biological properties have attracted much attention.
Investigations on the structure–activity relationship have
confirmed the manoalide I and cacospongionolide B II, as
two naturally isolated marine compounds, containing a
pyrano–furanone moiety which is considered to be a
pharmacophoric group [22–24] (Fig. 1).
Keywords Iminolactone Á Isocyanide Á
Multicomponent reaction Á Heterocycle containing
pyran–furan Á Zwitterion
One-pot multicomponent reactions (MCRs), in which at
least three or more starting materials react to form a
product, are always resource-effective and environmen-
tally acceptable, and thus ‘‘greener’’ as compared to
classical multistep reactions. Recently, MCRs have
evolved from random academic oddities to design
approaches in combinatorial chemistry, natural and com-
plex products synthesis [25, 26]. Because of the unique
properties of the isocyanide group, isocyanide-based
MCRS (IMCRs) are among the most versatile, in terms of
the number and variety of compounds with potential
biological and medicinal activities which can be generated
[27, 28].
Introduction
Iminolactones have been intensively studied in the past,
especially because of their effects as antibacterial agents,
aldosterone inhibitors, and proper precursors for the prep-
aration of a wide spectrum of natural compounds [1].
Iminolactones could be hydrolyzed with aqueous hydro-
chloric acid to produce butenolides [2, 3]. The unique
structural feature of this core skeleton has inspired interest
regarding to their wide range of biological activities such
as: antimicrobial [4], antifungal [5, 6], anti-inflammatory
[7], anticancer [8, 9], and antiviral HIV-1 [10, 11].
In view of our current studies on IMCRs [29–31] and
interest in the synthesis of iminolactones [32–34], herein, we
wish to report the synthesis of highly substituted 2,5-dihy-
dro-2-(3,4-dihydro-6-methyl-2,4-dioxo-2H-pyran-3-yl)-2-
methyl-5-(methylimino)furan-3,4-dicarboxylates 4a-h via a
three-component condesation reaction of an isocyanide 1
with a dialkyl acetylenedicarboxylate 2 and 3-acetyl-6-
methyl-3H-pyran-2,4-dione 3 at room temperature in
methylene chloride without using any catalyst (Scheme 1).
A. Shaabani (&) Á M. Mahyari Á F. Hajishaabanha Á
H. Mofakham
Department of Chemistry, Shahid Beheshti University,
G.C, P.O. Box 19396-4716, Tehran, Iran
e-mail: a-shaabani@sbu.ac.ir
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J IRAN CHEM SOC (2014) 11:1183–1187
The mixture was stirred for 16 h at room temperature. The
solvent was removed under vacuum and the residue crys-
tallized from acetone to afford the pure product as colorless
crystals.
(5Z)-Dimethyl 5-(cyclohexylimino)-2,5-dihydro-2-(3,4-
dihydro-6-methyl-2,4-dioxo-2H-pyran-3-yl)-2-methylfuran-
3,4-dicarboxylate (4a). Colorless crystals. Mp: 143–144 °C.
yield: 75 %. IR (KBr, cm-1): 3,018, 2,997, 2,971, 2,934,
2,856, 1,754, 1,728, 1,670, 1,630, 1,559. 1H-NMR
(300 MHz, DMSO-d6): d (ppm) 1.00–1.85 (m, 5CH2 of
cyclohexyl, 10H), 2.10–2.35 (br s, 2CH3, 6H), 3.47 (m,
CH–N, 1H), 3.77 (s, OCH3, 3H), 3.83 (s, OCH3, 3H), 6.20
(s, CH, 1H), 6.89 (s, CH–CO, 1H). 13C-NMR (75.47 MHz,
DMSO-d6): d (ppm) 20.0, 24.9, 25.8, 30.1, 31.0 (C-cyclo-
hexyl and 2CH3), 53.2, 53.8 (2 OCH3), 60.8 (CH–NH),
106.7, 125.3, 130.0, 140.4, 149.1, 160.9, 163.2, 163.8,
163.9, 164.4, 197.7. MS, m/z 404 (M?-15, 3), 376 (9), 344
(2), 318 (7), 286 (13), 262 (13), 204 (30), 171 (15), 59 (20),
43 (100). Anal. Calcd. for C21H25NO8: C, 60.14; H, 6.01;
N, 3.34 %. Found: C, 60.05; H, 5.92; N, 3.24 %.
Fig. 1 The structure of I and II
(5Z)-Diethyl 5-(cyclohexylimino)-2,5-dihydro-2-(3,4-
dihydro-6-methyl-2,4-dioxo-2H-pyran-3-yl)-2-methylfuran-
3,4-dicarboxylate (4b). Colorless crystal. Mp: 121–122 °C.
yield: 70 %. IR (KBr, cm-1): 3,099, 2,977, 2,959, 2,929,
1
1,721, 1,701, 1,666, 1,634, 1,565 l. H-NMR (300 MHz,
DMSO-d6): d (ppm) 1.00–1.83 (m, 5CH2 of cyclohexyl,
2CH3, 16H), 2.10–2.35 (br s, 2CH3, 6H), 3.44 (m, CH–N,
1H), 4.10–4.30 (m, 2OCH2, 4H), 6.20 (s, CH, 1H), 6.85 (s,
CH–CO, 1H). 13C-NMR (75.47 MHz, DMSO-d6): d (ppm)
14.2, 14.3, 15.6, 20.0, 24.9, 25.2, 25.8, 30.1, 31.9 (C-
cyclohexyl and 4CH3), 60.7, 62.0 (2OCH2), 62.9 (CH–N),
106.5, 125.2, 130.2, 140.8, 149.0, 160.9, 162.7, 163.7,
163.8, 163.9, 197.6. MS, m/z 404 (M?-43, 15), 332 (15),
286 (40), 276 (35), 248 (10), 204 (40), 176 (9), 143 (45),
125 (26), 81 (10), 43 (100). Anal. Calcd. for C23H29NO8: C,
61.73; H, 6.53; N, 3.13 %. Found: C, 61.63; H, 6.43; N,
3.03 %.
Scheme 1 Synthesis of 2,5-dihydro-2-(3,4-dihydro-6-methyl-2,4-
dioxo-2H-pyran-3-yl)-2-methyl-5-(methylimino)furan-3,4-dicarbox-
ylate derivatives 4a-h
Experimental
Melting points were measured on an Electrothermal 9100
apparatus. Mass spectra were recorded on a Shimadzu
GCMS-QP1100EX mass spectrometer operating at an
1
ionization potential of 70 eV. H and 13C NMR spectra
were recorded in DMSO-d6 on a BRUKER DRX-300
AVANCE spectrometer. IR spectra (KBr) were recorded
on a Bomem MB-Series FT-IR spectrophotometer. Ele-
mental analyses were performed on an elementar analy-
sensysteme GmbH VarioEL CHNS mode. All chemicals
used were obtained from Fluka and Merck and were
applied without further purification.
(5Z)-Dimethyl 5-(2,4,4-trimethylpentan-2-ylimino)-2,5-
dihydro-2-(3,4-dihydro-6-methyl-2,4-dioxo-2H-pyran-3-
yl)-2-methylfuran-3,4-dicarboxylate (4c). Colorless crystal.
Mp: 105–106 °C. yield: 70 %. IR (KBr, cm-1): 3,090,
2,985, 2,959, 2,898, 2,863, 1,748, 1,724, 1,649, 1,589,
1,552. 1H-NMR (300 MHz, DMSO-d6): d (ppm) 0.94 (br s,
3CH3, 9H), 1.21–1.70 (m, 2CH3 and CH2, 8H), 2.21–2.26
(br s, 2CH3, 6H), 3.62 (s, OCH3, 3H), 3.70 (s, OCH3, 3H),
6.29 (s, CH, 1H), 6.41 (s, CH–CO, 1H). 13C-NMR
(75.47 MHz, DMSO-d6): d (ppm) 19.9, 20.6, 27.3, 29.1,
29.2, 30.2, 31.9, 52.9, 53.8, 57.2, 58.8, 65.9, 95.6, 99.1,
140.3, 161.5, 162.44, 165.3, 165.9, 169.7, 198.6. MS, m/z
450 (M??1, 2), 338 (10), 294 (12), 263 (20), 236 (27), 197
(50), 165 (30), 85 (15), 62 (85), 43 (100). Anal. Calcd. for
C23H31NO8: C, 61.46; H, 6.95; N, 3.12 %. Found: C,
61.36; H, 6.85; N, 3.02 %.
Typical procedure for the preparation of (5Z)-dimethyl
5-(cyclohexylimino)-2,5-dihydro-2-(3,4-dihydro-6-
methyl-2,4-dioxo-2H-pyran-3-yl)-2-methylfuran-3,4-
dicarboxylate 4a
To a magnetically stirred mixture of 3-acetyl-6-methyl-3H-
pyran-2,4-dione (1 mmol) and dimethyl acetylenedicar-
boxylate (1 mmol) in CH2Cl2 (5 mL), cyclohexyl isocya-
nide (1 mmol) was added dropwise at 0 °C over 10 min.
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(5Z)-Dimethyl
5-(benzylimino)-2,5-dihydro-2-(3,4-
6H), 3.79 (br s, CH-NH, 2H), 6.32 (s, CH, 1H), 6.94 (s,
CH–CO, 1H). 13C-NMR (75.47 MHz, DMSO-d6): d (ppm)
15.1, 15.5, 24.3, 25.2, 25.7, 28.5, 28.7, 31.9, 49.6, 80.6,
81.6, 102.4, 120.5, 133.1, 141.4, 149.8, 161.3, 163.1,
163.9, 164.0, 164.4, 198.7. Anal. Calcd. for C27H37NO8: C,
64.40; H, 7.41; N, 2.78 %. Found: C, 64.42; H, 7.40; N,
2.68 %.
dihydro-6-methyl-2,4-dioxo-2H-pyran-3-yl)-2-methylfuran-
3,4-dicarboxylate (4d). Colorless crystal. Mp: 124–125 °C.
yield: 72 %. IR (KBr, cm-1): 3099, 3042, 2998, 2946,
1
2924, 2889, 2,842, 1,737, 1,709, 1,632, 1,549. H-NMR
(300 MHz, DMSO-d6): d (ppm) 2.22 (s, CH3, 3H), 2.39 (s,
CH3, 3H), 3.75 (s, OCH3, 3H), 3.77 (s, OCH3, 3H), 4.88 (s,
CH2–N, 2H), 6.57 (s, CH, 1H), 6.84 (s, CH–CO, 1H),
7.24–7.46 (m, CH–Ar, 5H). 13C-NMR (75.47 MHz,
DMSO-d6): d (ppm) 20.0, 29.7 (2CH3), 52.6, 53.2 (2OCH3),
53.6 (CH2–N), 102.7, 119.8, 128.2, 128.7, 129.0, 130.0,
135.3, 140.2, 150.6, 161.1, 162.7, 163.9, 164.3, 164.5,
196.6. MS, m/z 384 (M?-43, 3), 352 (4), 326 (3), 294 (5),
256 (2), 171(2), 91 (100), 43 (24). Anal. Calcd. for
C22H21NO8: C, 61.82; H, 4.95; N, 3.28 %. Found: C, 61.72;
H, 4.85; N, 3.18 %.
(Z)-Diethyl 2-methyl-2-(6-methyl-2,4-dioxo-3,4-dihy-
dro-2H-pyran-3-yl)-5-(2,4,4-trimethylpentan-2-ylimino)-2,5-
dihydrofuran-3,4-dicarboxylate (4 h). Colorless crystal. Mp:
114–116 °C. yield: 65 %. IR (KBr, cm-1): 3,011, 2,976,
1
2,945, 2,872, 2,845, 1,753, 1,731, 1,653, 1,573, 1,557. H-
NMR (300 MHz, DMSO-d6): d (ppm) 1.02 (br s, 3CH3, 9H),
1.25–1.63 (m, 2CH3 and CH2, 8H) 2.44–2.48 (br s, 2CH3,
6H), 3.45 (s, OCH3, 3H), 3.64 (s, OCH3, 3H), 4.24–4.34 (m,
2O–CH2, 4H), 6.35 (s, CH, 1H), 6.48 (s, CH–CO, 1H). 13C-
NMR (75.47 MHz, DMSO-d6): d (ppm) 20.2, 20.4, 26.9,
29.9, 30.1, 30.5, 34.0, 53.1, 54.2, 57.5, 60.0, 66.3, 94.2, 99.9,
141.6, 161.9, 162.8, 166.0, 166.1, 169.2, 199.2. MS, m/z 432
(M?-45, 10), 417 (15), 402 (25), 275 (60), 204 (5), 110 (20),
94 (55), 78 (8). Anal. Calcd. for C25H35NO8: C, 62.88; H,
7.39; N, 2.93 %. Found: 62.88; H, 7.39; N, 2.83 %.
(5Z)-Diethyl 5-(benzylimino)-2,5-dihydro-2-(3,4-dihy-
dro-6-methyl-2,4-dioxo-2H-pyran-3-yl)-2-methylfuran-3,4-
dicarboxylate (4e). Colorless crystal. Mp: 106–107 °C.
yield: 65 %. IR (KBr, cm-1): 3103, 3064, 3024, 2990,
2933, 2907, 2,868, 1,709, 1,626, 1,557. 1H-NMR
(300 MHz, DMSO-d6): d (ppm) 1.20–1.27 (m, CH3, 6H)
2.20 (s, CH3, 3H), 2.37 (s, CH3, 3H), 4.16–4.23 (m, OCH2,
4H), 4.88 (s, CH2–N, 2H), 6.56 (s, CH, 1H), 6.80 (s, CH–
CO, 1H), 7.26–7.45 (m, CH–Ar, 5H). 13C-NMR
(75.47 MHz, DMSO-d6): d (ppm) 14.1, 14.3, 19.9, 29.70 (4
CH3), 52.4, 62.1 (2 OCH3), 62.9 (CH2–N), 102.5, 119.6,
128.2, 128.6, 128.9, 130.2, 135.26, 140.2, 149.8, 161.0,
162.2, 163.8, 164.5, 181.0, 196.4. MS, m/z 412 (M?-43,
3), 340 (4), 294 (8), 256 (4), 214 (3), 143 (4), 125 (3), 91
(100), 43 (24). Anal. Calcd. for C24H25NO8: C, 63.29; H,
5.53; N, 3.08 %. Found: C, 63.19; H, 5.43; N, 3.00 %.
(Z)-Dimethyl 5-(tert-butylimino)-2-methyl-2-(6-methyl-
2,4-dioxo-3,4-dihydro-2H-pyran-3-yl)-2,5-dihydrofuran-3,4-
dicarboxylate (4f). Colorless crystal. Mp: 134–136 °C.
yield: 68 %. IR (KBr, cm-1): 2,933, 2,859, 1,751, 1,673,
1,602, 1,446, 1,644, 1,535. 1H-NMR (300 MHz, DMSO-d6):
d (ppm) 1.45 (m, 3CH3, 9H), 2.21–2.43 (br s, 2CH3, 6H),
3.62 (s, OCH3, 3H), 3.70 (s, OCH3, 3H), 6.40 (s, CH, 1H),
6.75 (s, CH–CO, 1H). 13C NMR (75.47 MHz, DMSO-d6): d
(ppm) 20.3, 29.2, 30.2, 52.8, 53.5 (2OCH3), 62.4, 71.4, 72.3,
98.5, 100.2, 147.8, 159.6, 164.6, 165.7, 166.5, 166.4, 199.2.
MS, m/z 394 (M??1, 10), 370 (50), 306 (75), 278 (50), 236
(80), 171 (50), 138 (75); 84 (25). Anal. Calcd. for
C19H23NO8: C, 58.01; H, 5.89; N, 3.56 %. Found: C, 58.10;
H, 6.85; N, 3.43 %.
Results and discussion
In a pilot experiment, the treatment of cyclohexyl isocya-
nide 1a, dimethyl acetylenedicarboxylate 2a and 3-acetyl-
6-methyl-3H-pyran-2,4-dione 3 afforded (5Z)-dimethyl-5-
(cyclohexylimino)-2,5-dihydro-2-(3,4-dihydro-6-methyl-
2,4-dioxo-2H-pyran-3-yl)-2-methylfuran-3,4-dicarboxylate
4a in 75 % yield. To explore the scope and limitations of
this reaction, we extended the procedure to various alkyl,
aryl and alicyclic isocyanides and various dialkyl acety-
lenedicarboxylates with 3-acetyl-6-methyl-3H-pyran-2,4-
dione. As indicated in Fig. 2, the reactions proceed very
efficiently and led to the formation of corresponding 2,5-
dihydro-2-(3,4-dihydro-6-methyl-2,4-dioxo-2H-pyran-3-
yl)-2-methyl-5-(methylimino)furan-3,4-dicarboxylates 4a-
h in good yields at room temperature without any unde-
sirable by-products.
The structures of the products were deduced from their
IR, mass, 1H NMR, and 13C NMR spectra. The mass
spectra of these compounds displayed molecular ion peaks
1
at the appropriate m/z values. The H NMR spectrum of
(4a) consisted of a multiplet for the cyclohexyl ring
(d = 1.00–1.85 ppm), two broad singlet for methyl groups
(d = 2.10 and 2.35 ppm), a multiplet for the N–CH
cyclohexyl proton (d = 3.47 ppm), two singlet for the
methoxy groups (d = 3.77 and 3.83 ppm), a singlet for the
C=C–H group (d = 6.20 ppm), and a singlet for the OC–
CH–CO proton (d = 6.89 ppm). The 1H decoupled 13C
NMR spectrum of 4a showed 19 distinct resonances, partial
(Z)-Di-tert-butyl 5-(cyclohexylimino)-2-methyl-2-(6-
methyl-2,4-dioxo-3,4-dihydro-2H-pyran-3-yl)-2,5-dihydro-
furan-3,4-dicarboxylate (4 g). Colorless crystal. Mp:
138–141 °C. yield: 72 %. IR (KBr, cm-1): 3,102, 2,981,
1
2,933, 2,859, 1,732, 1,709, 1,673, 1,652, 1,574. H-NMR
(300 MHz, DMSO-d6): d (ppm) 1.20–1.93 (m, 5CH2 of
cyclohexyl and 2OC(CH3)3, 28H), 2.09–2.28 (br s, 2CH3,
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J IRAN CHEM SOC (2014) 11:1183–1187
dioxo-2H-pyran-3-yl)-2-methyl-5-(methylimino)furan-3,4-
dicarboxylates 4a-h.
In conclusion, we have explored an efficient three-
component reaction strategy for the synthesis of fully
functionalized iminolactones which contains pyran–furan
moiety from readily available isocyanides, dialkyl acety-
lenedicarboxilates and 3-acetyl-6-methyl-3H-pyran-2,4-
dione in absence of catalyst. Scope and limitation of the
reaction are described. The reaction has been shown to
display relatively good functional group tolerance, good
yields, and product isolation is very straightforward. We
hope that this approach may be of value to others seeking
novel synthetic fragments with unique properties for
medicinal chemistry.
Acknowledgments We gratefully acknowledge financial support
from the Research Council of Shahid Beheshti University and from
the Iran National Science Foundation (INSF).
References
Product
4a 4b 4c 4d 4e 4f 4g 4h
Yield (%)
75 70 70 72 65 68 72 65
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