Three-component reaction between alkyl(aryl) isocyanides and dialkyl acetylenedicarboxylates in the presence of ethyl trifluoroacetate

Article abstract of DOI:10.3184/174751911X13025338429293

The 1:1 intermediate generated by the addition of alkyl(aryl) isocyanides to dialkyl acetylenedicarboxylates is trapped by ethyl trifluoroacetate in the absence of a catalyst to form highly functionalized dialkyl 5-[alkyl(aryl)imino] -2-ethoxy-2-(trifluor

Full text of DOI:10.3184/174751911X13025338429293

JOURNAL OF CHEMICAL RESEARCH 2011
RESEARCH PAPER 231
APRIL, 231–233
Three-component reaction between alkyl(aryl) isocyanides and dialkyl
acetylenedicarboxylates in the presence of ethyl trifluoroacetate
Khatereh Khandan–Barani, Malek Taher Maghsoodlou*, Sayyed Mostafa Habibi-Khorasani,
Nourallah Hazeri and Seyyed Sajad Sajadikhah
Department of Chemistry, University of Sistan and Baluchestan, PO Box 98135-674, Zahedan, Iran
The 1:1 intermediate generated by the addition of alkyl(aryl) isocyanides to dialkyl acetylenedicarboxylates is trapped
by ethyl trifluoroacetate in the absence of a catalyst to form highly functionalized dialkyl 5-[alkyl(aryl)imino]-2-
ethoxy-2-(trifluoromethyl)-2,5-dihydrofuran–3,4-dicarboxylates in good yields.
Keywords: ethyl trifluoroacetate, furan derivatives, isocyanide, multicomponent reaction
The development of new syntheses of useful organic com-
pounds from readily available reagents is one of the major
aims of organic synthesis.1 At the same time, the increasing
environmental awareness of the chemical community has led
to the search for more efficient methods of chemical synthe-
sis.2,3 Multicomponent reactions (MCRs), by virtue of their
convergence, productivity, facile execution and generally
high yields of products, have attracted attention in synthetic
chemistry.4,5
Results and discussion
The one-pot three-component condensation reaction was car-
ried out at 38 °C and completed after 24 h to afford dialkyl
5-[alkyl(aryl)imino]-2-ethoxy-2-(trifluoromethyl)-2,5-dihy-
drofuran–3,4-dicarboxylate 4 in good yields in the absence of
a catalyst (Scheme 1).
The structure of compounds 4a–j was deduced from their
IR, 1H NMR, 13C NMR, 19F NMR, mass spectral data and ele-
mental analysis. The mass spectra of these compounds 4a–j
displayed M+ or M++1 peaks at the appropriate m/z values. The
1H NMR spectrum of compound 4a exhibited a triplet for the
methyl group at δ = 1.29 ppm (3J = 7.0 Hz), a multiplet for the
cyclohexyl ring δ = 1.21–1.75 ppm, a multiplet for the N–CH
cyclohexyl proton δ = 3.55 ppm, a quartet for the O–CH2 group
δ = 3.62 ppm, (3J = 7.0 Hz) and two singlets for the methoxy
groups δ = 3.86 and 3.91 ppm.
The development of new MCRs is an interesting research
topic in chemistry.6–8 In particular, isocyanide-based multi-
component reactions have been applied to the synthesis of
various furan and furan derivatives.9–13 Polyfunctionalised
furan derivatives are versatile synthetic starting materials
for the preparation of a variety of heterocyclic and acyclic
compounds,14–19 such as iminolactones which can be easily
hydrolysed to spirolactones, a structural motif, present in a
number of biologically active natural products.20,21 There are a
number of reports of iminolactones synthesis.22–24
The 13C NMR spectrum of each compound displayed reso-
nances in agreement with proposed structure. The 19F NMR
spectrum of 4a exhibited a single sharp line at δ = 80.52 ppm.
Partial assignments of these resonances are given in the exper-
imental data. The IR spectra of 4a showed strong absorptions
at 1744 and 1697 cm−1 due to the ester carbonyls. The 1H NMR,
13C NMR and 19F NMR spectra of 4b–j are similar to 4a. These
data are given in the experimental section.
In continuation of our previous works on IMCRs,25–33 we
now report the result of our investigation of the reaction
between alkyl(aryl) isocyanides 1 and dialkyl acetylenedicar-
boxylates 2 in the presence of ethyl trifluoroacetate 3 in
refluxing CH2Cl2.
Scheme 1 Synthesis of compounds 4a–j.
* Correspondent. E-mail: mt_maghsoodlou@yahoo.com

232 JOURNAL OF CHEMICAL RESEARCH 2011
Scheme 2 proposed mechanism for the formation of compound 4.
2OCH3); 13C NMR (75.5 MHz, CDCl3): δC 14.7 (CH3), 24.4, 24.5,
25.8, 33.0 and 33.2 (5CH2 of cyclohexyl), 53.1 and 53.2 (2OMe),
57.2 (N–CH), 60.9 (OCH2), 105.7 (q, 2J = 35.2 Hz, CCF3), 120.5
(q, 1J = 286.1 Hz, CF3), 136.5 and 141.1 (Colefin), 149.6 (Cimine), 159.9
and 160.6 (2C=O); 19F NMR (282.4 MHz, CDCl3): δF 80.52; MS
(m⁄z, %): 394 (M++1, 7), 393 (M+, 9), 361 (89), 347 (45), 334 (49), 252
(36), 236 (100), 97 (38), 55 (95), 41 (80). Anal. Calcd for C17H22F3NO6
(393.35): C, 51.91; H, 5.64; N, 3.56. Found: C, 52.35; H, 5.75;
N, 3.88%.
On the basis of the well established chemistry of isocya-
nides,34,35 it is reasonable to assume that compounds 4 result
from initial addition of alkyl(aryl) isocyanides 1 to the dialkyl
acetylenedicarboxylates 2 and concomitant addition to ethyl
trifluoroacetate 3 leading to iminolactones 4 (Scheme 2).
In conclusion, we have described a convenient and efficient
synthesis of functionalised dialkyl 5-[alkyl(aryl)imino]-2-
ethoxy-2-(trifluoromethyl)-2,5-dihydrofuran–3,4-dicarboxyl-
ates from alkyl(aryl) isocyanides and dialkyl acetylenedicar-
boxylates in the presence of ethyl trifluoroacetate. The present
procedure has the advantage that not only the reaction is per-
formed under neutral conditions but also the reactants can be
mixed without any activation or modification.
Diethyl 5-(cyclohexylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-dihy-
drofuran–3,4-dicarboxylate (4b): Orange oil (0.396 g, 94%); IR (KBr)
1
(νmax, cm−1): 2985, 2935, 1741 and 1698 (2C=O), 1659 (C=N); H
3
NMR (300.1 MHz, CDCl3): δH 1.26 (3H, t, J = 7.0 Hz, CH3), 1.17–
1.74 (10H, m, 5CH2), 1.30 and 1.36 (6H, 2t, 3J = 7.1 Hz, 2CH3), 3.61)
2H, q, 3J = 7.1 Hz, OCH2(, 3.64 (1H, m, N–CH), 4.30 and 4.38 (4H,
3
2q, J = 7.1 Hz, 2OCH2); 13C NMR (75.5 MHz, CDCl3): δC 13.8 and
Experimental
13.9 (2CH3), 14.7 (CH3), 24.4, 25.0, 25.6, 33.0 and 33.2 (5CH2
of cyclohexyl), 57.0 (N–CH), 60.8 (OCH2), 62.3 and 62.5 (2 OCH2),
Tert-butyl, benzyl, 2,6-dimethylphenyl and cyclohexyl isocyanides
were purchased from Fluka. Dialkyl acetylenedicarboxylates and
ethyl trifluoroacetate were obtained from Merck and Fluka. All of the
compounds were used without further purification. Melting points and
IR spectra were measured on an Electrothermal 9100 apparatus and
2
1
105.7 (q, J = 35.2 Hz, CCF3), 120.6 (q, J = 286.1 Hz, CF3), 136.4
and 140.9 (Colefin), 149.8 (Cimine), 159.5 and 160.2 (2C=O); 19F NMR
(282.4 MHz, CDCl3): δF 80.21; MS (m⁄z, %): 422 (M++1, 96), 380
(100), 352 (6), 334 (435), 267 (12), 97 (18), 83 (17), 41 (35). Anal.
Calcd for C19H26F3NO6 (421.41): C, 54.15; H, 6.22; N, 3.32. Found:
C, 54.15; H, 6.45; N, 3.54%.
1
a Shimadzu IR–470 spectrometer respectively. The H, 13C and 19F
NMR spectra were recorded on a Bruker DRX–300 Avance instru-
ment with CDCl3 as solvent at 300.1, 75.5 and 282.4 MHz, respec-
tively. The mass spectra were recorded on a Shimadzu GC/MS QP
1100 EX mass spectrometer operating at an ionization potential of
70 eV. Elemental analyses for C, H and N using a Heraeus CHN–
O-Rapid analyzer were carried out at the research laboratory of
Tarbiat Moallem University of Tehran.
Di-tert-butyl 5-(cyclohexylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-
dihydrofuran–3,4-dicarboxylate (4c): Orange oil (0.405 g, 85%); IR
(KBr) (νmax, cm−1): 2981, 2933, 1733 and 1699 (2C=O), 1657 (C=N);
3
1H NMR (300.1 MHz, CDCl3): δH 1.29 (3H, t, J = 7.0 Hz, CH3),
1.31–1.75 (10H, m, 5CH2), 1.52 and 1.55 (18H, 2s, 2C(CH3)3), 3.59
3
(2H, q, J = 7.0 Hz, OCH2), 3.69 (1H, m, N–CH); 13C NMR (75.5
MHz, CDCl3): δC 14.7 (CH3), 24.1, 24.2, 25.7, 33.1 and 33.3 (5CH2 of
cyclohexyl), 28.0 and 28.1 (2C(CH3)3), 56.4 (N–CH), 60.5 (OCH2),
84.1 and 84.2 (2O-C(Me)3), 105.7 (q, 2J = 34.6 Hz, CCF3), 120.7 (q,
1J = 285.6 Hz, CF3), 136.8 and 140.3(Colefin), 149.8 (Cimine), 158.9 and
159.4 (2C=O); 19F NMR (282.4 MHz, CDCl3): δF 80.11; MS (m⁄z, %):
478 (M++1, 83), 461 (2), 422 (47), 347 (50), 319 (30), 301 (11), 275
(4), 98 (21), 57 (100), 41 (39). Anal. Calcd for C23H34F3NO6 (477.51):
C, 57.85; H, 7.18; N, 2.93. Found: C, 58.33; H, 7.74; N, 3.38%.
Dimethyl 5-(tert-butylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-dihy-
drofuran–3,4-dicarboxylate (4d): Orange oil (0.330 g, 90%); IR (KBr)
General procedure
The process for the preparation of dimethyl 5-(cyclohexylimino)-2-
ethoxy-2-(trifluoromethyl)-2,5-dihydrofuran–3,4-dicarboxylates 4a
is described as an example. The solution of cyclohexyl isocyanide
(0.11 g or 1 mmol) in CH2Cl2 3 mL solvent was slowly added drop-
wise to a mixture of ethyl trifluoroacetate (0.14 g or 1mmol) and
dimethyl acetylenedicarboxylate (0.14 g or 1 mmol) in CH2Cl2 20 mL
solvent over 3 min at room temperature. After the addition, the solu-
tion was refluxed at 38 °C for 24 h. Then the solvent was removed
under reduced pressure, and the residue was washed with mixture of
cold diethyl ether and N–hexane with 1: 3 ratio (2×3 mL) to afford the
pure product.
1
(νmax, cm−1): 2973, 2907, 1745 and 1693 (2C=O), 1659 (C=N); H
3
NMR (300.1 MHz, CDCl3): δH 1.26 (3H, t, J = 7.1 Hz, CH3), 1.29
3
(9H, s, C(CH3)3), 3.56 (2H, q, J = 7.1 Hz, OCH2), 3.83 and 3.88
Dimethyl 5-(cyclohexylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-
dihydrofuran–3,4-dicarboxylate (4a): Dark orange powder (0.350 g,
89%); m.p. 61–63 °C; IR (KBr) (νmax, cm−1): 2933, 2858, 1744 and
(6H, 2s, 2OCH3); 13C NMR (75.5 MHz, CDCl3): δC 14.7 (CH3), 29.6
(C(CH3)3), 53.0 and 53.1 (2OMe), 55.8 (N–C(Me)3), 60.9 (OCH2),
2
1
106.0 (q, J = 35.1 Hz, CCF3), 120.5 (q, J = 286.1 Hz, CF3), 135.0
and 142.9 (Colefin), 147.7 (Cimine), 159.8 and 160.9 (2C=O); 19F NMR
(282.4 MHz, CDCl3): δF 80.61; MS (m⁄z, %): 368 (M++1, 94), 352
(100), 306 (34), 274 (23), 84 (14), 57 (56).Anal. Calcd for C15H20F3NO6
1
1697 (2C=O), 1647 (C=N); H NMR (300.1 MHz, CDCl3): δH 1.29
(3H, t, 3J = 7.0 Hz, CH3), 1.21–1.75 (10H, m, 5CH2), 3.62 (2H,
3
q, J = 7.0 Hz, OCH2), 3.66 (1H, m, N–CH), 3.86 and 3.91 (6H, 2s,

JOURNAL OF CHEMICAL RESEARCH 2011 233
(367.32): C, 49.05; H, 5.49; N, 3.81. Found: C, 48.46; H, 5.64;
N, 3.90%.
Dimethyl 5-(benzylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-dihy-
drofuran–3,4-dicarboxylates (4j): Dark orange powder (0.369 g,
92%); m.p. 78–80 °C; IR (KBr) (νmax, cm−1): 2963, 2889, 1749 and
Diethyl 5-(tert-butylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-dihy-
drofuran–3,4-dicarboxylate (4e): Orange oil (0.363 g, 92%); IR (KBr)
(νmax, cm−1): 2983, 2940, 1740 and 1698 (2C=O), 1656 (C=N);
1H NMR (300.1 MHz, CDCl3): δH 1.26 (3H, t, 3J=7.0 Hz, CH3), 1.29
(9H, s, C(CH3)3), 1.31 and 1.34 (6H, 2t, 3J = 7.1 Hz, 2CH3), 3.57 (2H,
1
1695 (2C=O), 1654 (C=N); H NMR (300.1 MHz, CDCl3): δH 1.28
3
3
(3H, t, J = 7.0 Hz, CH3), 3.60 (2H, q, J = 7.0 Hz, OCH2), 3.89 and
3.93 (6H, 2s, 2OCH3), 4.74 (2H, s, N–CH2), 7.26–7.35 (5H, m, Ar-H);
13C NMR (75.5 MHz, CDCl3): δC 14.7 (CH3), 52.3 (NCH2), 53.3 and
2
3
3
53.4 (2OMe), 61.2 (OCH2), 105.7 (q, J = 35.1 Hz, CCF3), 120.3 (q,
q, J = 7.1 Hz, OCH2), 4.26 and 4.35 (4H, 2q, J = 7.1 Hz, 2OCH2);
13C NMR (75.5 MHz, CDCl3): δC 13.7 and 13.9 (2CH3), 14.7 (CH3),
29.4 (C(CH3)3), 55.7 (N–C(Me)3), 60.8 (OCH2), 62.3 and 62.4
1J = 276.6 Hz, CF3), 127.0, 127.7, 128.4, 138.0 (Carom), 138.5 and
140.2 (Colefin), 152.2 (Cimine), 159.8 and 160.4 (2C=O); 19F NMR (282.4
MHz, CDCl3): δF 80.37; MS (m⁄z, %): 402 (M++1, 6), 401 (M+, 9), 369
(12), 355 (67), 340 (11), 296 (26), 236 (100), 132 (14), 105 (8), 91
(89), 77 (7), 59 (20). Anal. Calcd for C18H18F3NO6 (401.33): C, 53.87;
H, 4.52; N, 3.49. Found: C, 54.26; H, 4.55; N, 3.65%.
2
1
(2OCH2), 106.5 (q, J = 35.2 Hz, CCF3), 120.6 (q, J = 286.2 Hz,
CF3), 135.0 and 142.6 (Colefin), 147.7 (Cimine), 159.4 and 160.5 (2C=O);
19F NMR (282.4 MHz, CDCl3): δF 80.40; MS (m⁄z, %): 396 (M++1,
71), 380 (100), 334 (39), 306(3), 260 (16), 84 (8), 57 (31). Anal. Calcd
for C17H24F3NO6 (395.37): C, 51.64; H, 6.12; N, 3.54. Found:
C, 51.52; H, 6.31; N, 3.59%.
We gratefully acknowledge financial support from the Research
Council of University of Sistan and Baluchestan.
Di-tert-butyl 5-(tert-butylimino)-2-ethoxy-2-(trifluoromethyl)-2,5-
dihydrofuran–3,4-dicarboxylate (4f): Pale orange oil (0.401 g, 89%);
IR (KBr) (νmax, cm−1): 2981, 2936, 1726 and 1701 (2C=O), 1661
1
3
Received 15 December 2010; accepted 25 March 2011
Paper 1000494 doi: 10.3184/174751911X13025338429293
Published online: 3 May 2011
(C=N); H NMR (300.1 MHz, CDCl3): δH 1.28 (3H, t, J = 7.1 Hz,
CH3), 1.29 (9H, s, N–C(CH3)3), 1.49 and 1.54 (18H, 2s, 2OC(CH3)3),
3
3.56 (2H, q, J = 7.1 Hz, OCH2); 13C NMR (75.5 MHz, CDCl3): δC
14.7 (CH3), 27.8 and 28.0 (2C(CH3)3), 29.5 (C(CH3)3), 55.3 (N–
C(Me)3), 60.5 (OCH2), 83.9 and 84.1 (2O-C(Me)3), 106.0 (q, 2J = 34.9
References
1
Hz, CCF3), 120.8 (q, J = 286.1 Hz, CF3), 135.2 and 142.2 (Colefin),
1
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324 (41), 278 (5), 84 (4), 57 (85). Anal. Calcd for C21H32F3NO6
(451.48): C, 55.87; H, 7.14; N, 3.10. Found: C, 56.27; H, 7.63;
N, 2.88%.
2
3
4
5
6
7
Dimethyl 5-(2,6-dimethylphenylimino)-2-ethoxy-2-(trifluoromethyl)-
2,5-dihydrofuran–3,4-dicarboxylates (4g): Dark orange powder
(0.373 g, 90%); m.p. 70–72 °C; IR (KBr) (νmax, cm−1): 2926, 2855,
1764 and 1703 (2C=O), 1655 (C=N); 1H NMR (300.1 MHz, CDCl3):
δH 1.27 (3H, t, 3J = 7.0 Hz, CH3), 2.10 (6H, s, 2CH3), 3.64 (2H,
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3
q, J = 7.0 Hz, OCH2), 3.92 and 3.99 (6H, 2s, 2OCH3), 6.93–7.10
(3H, m, Ar-H); 13C NMR (75.5 MHz, CDCl3): δC 14.6 (CH3), 17.8
(2CH3), 53.4 and 53.5 (2OCH3), 61.3 (OCH2), 105.6 (q, 2J = 35.1 Hz,
CCF3), 120.8 (q, 1J = 286.5 Hz, CF3), 127.6, 129.0, 132.6, 134.0
(Carom), 138.9 and 142.9 (Colefin), 149.4 (Cimine), 159.7 and 160.3
(2C=O); 19F NMR (282.4 MHz, CDCl3): δF 80.13; MS (m⁄z, %): 416
(M++1, 29), 415 (M+, 100), 400 (2), 386 (18), 370 (6), 354(14), 296
(22), 146 (11), 118 (10), 91 (11), 77 (13), 59 (9). Anal. Calcd for
C19H20F3NO6 (415.36): C, 54.94; H, 4.85; N, 3.37. Found: C, 55.23;
H, 4.89; N, 3.31%.
Diethyl 5-(2,6-dimethylphenylimino)-2-ethoxy-2-(trifluoromethyl)-
2,5-dihydrofuran–3,4-dicarboxylates (4h): Dark orange (0.416 g,
94%); IR (KBr) (νmax, cm−1): 2985, 2941, 1740 and 1709 (2C=O),
1
3
1661 (C=N); H NMR (300.1 MHz, CDCl3): δH 1.27 (3H, t, J = 7.1
3
Hz, CH3), 1.33 and 1.40 (6H, 2t, J = 7.1 Hz, 2CH3), 2.11 (6H, s,
2CH3), 3.65 (2H, q, 3J = 7.1 Hz, OCH2), 4.37 and 4.46 (4H, 2q, 3J = 7.1
Hz, 2OCH2), 6.93–7.05 (3H, m, Ar-H); 13C NMR (75.5 MHz, CDCl3):
δC 13.8 and 14.0 (2CH3), 14.6 (CH3), 17.8 (2CH3), 61.3 (OCH2), 62.7
and 62.9 (2OCH2), 61.3 (OCH2), 108.7 (q, 2J = 28.5 Hz, CCF3), 120.3
(q, 1J = 286.4 Hz, CF3), 127.4, 127.6, 128.8, 130.9 (Carom), 138.6 and
143.0 (Colefin), 149.9 (Cimine), 159.2 and 159.9 (2C=O); 19F NMR (282.4
MHz, CDCl3): δF 80.08; MS (m⁄z, %): 444 (M++1, 82), 443 (M+, 100),
414 (10), 370 (16), 340(9), 282 (12), 149 (5), 103 (6), 77 (6). Anal.
Calcd for C21H24F3NO6 (443.41): C, 56.88; H, 5.46; N, 3.16. Found:
C, 57.32; H, 5.79; N, 3.23%.
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33 N. Hazeri, M.T. Maghsoodlou, S.M. Habibi-Khorassani and G. Marandi.
ARKIVOC, 2008, 14, 282.
34 I. Ugi, Isonitrile chemistry, Academic press, London, 1971.
35 I. Ugi, Angew. Chem., Int. Ed. Engl. 1982, 21, 810.
Di-tert-butyl 5-(2,6-dimethylphenylimino)-2-ethoxy-2-(trifluoromethyl)-
2,5-dihydrofuran–3,4-dicarboxylates (4i): Orange powder (0.439 g,
88%); m.p. 72–74 °C; IR (KBr) (νmax, cm−1): 2982, 2935, 1729 and
1
1702 (2C=O), 1655 (C=N); H NMR (300.1 MHz, CDCl3): δH 1.26
3
(3H, t, J = 7.0 Hz, CH3), 1.55 and 1.60 (18H, 2s, 2C(CH3)3), 2.09
3
(6H, s, 2CH3), 3.64 (2H, q, J = 7.0 Hz, OCH2), 6.94–7.04 (3H, m,
Ar-H); 13C NMR (75.5 MHz, CDCl3): δC 14.6 (CH3), 17.9 (2CH3),
27.9 and 28.1 (2C(CH3)3), 60.9 (OCH2), 84.7 and 84.8 (2OC(Me)3),
2
1
105.7 (q, J = 35.2 Hz, CCF3), 125.5 (q, J = 230.0 Hz, CF3), 127.0,
127.5, 132.1, 133.5 (Carom), 139.0 and 144.6 (Colefin), 151.9 (Cimine),
159.4 and 159.9 (2C=O); 19F NMR (282.4 MHz, CDCl3): δF 80.13;
MS (m⁄z, %): 500 (M++1, 7), 499 (M+, 18), 443 (59), 414 (8), 387
(100), 370 (27), 250 (31), 149 (34), 105 (15), 57 (84). Anal. Calcd for
C25H32F3NO6 (499.52): C, 60.11; H, 6.46; N, 2.80. Found: C, 60.54;
H, 7.04; N, 3.34%.

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