Synthesis of 1-(2,6-dimethylphenyl)-N-hydroxy-4,4-dialkyl-2,5-dioxo-N-aryl- 3-pyrrolidine-carboxamides from reaction of 2,6-dimethylphenyl isocyanide, alkylidene Meldrum's acids, and arylhydroxylamines

Article abstract of DOI:10.1080/00397910701845365

Alkylidene Meldrum's acids and 2,6-dimethylphenyl isocyanide react smoothly in the presence of arylhydroxylamines at room temperature to produce 2,5-dioxo-pyrrolidines in fairly high yield. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701845365

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Synthesis of
1‐(2,6‐Dimethylphenyl)‐N‐hydroxy‐4,4‐dialkyl‐2,5
from Reaction of 2,6‐Dimethylphenyl
Isocyanide, Alkylidene Meldrum's Acids, and
Arylhydroxylamines
Azizollah Habibi a , Leyla Mousavifar a b , Mohammad R. Yazdanbakhsh b
Issa Yavari c
&
a Faculty of Chemistry , Tarbiat Moallem University , Tehran, Iran
b Chemistry Department , Guilan University , Rasht, Guilan, Iran
c Chemistry Department , Tarbiat Modares University , Tehran, Iran
Published online: 22 Feb 2008.
To cite this article: Azizollah Habibi , Leyla Mousavifar , Mohammad R. Yazdanbakhsh & Issa Yavari (2008)
Synthesis of 1‐(2,6‐Dimethylphenyl)‐N‐hydroxy‐4,4‐dialkyl‐2,5‐dioxo‐N‐aryl‐3‐pyrrolidine‐carboxamides from
Reaction of 2,6‐Dimethylphenyl Isocyanide, Alkylidene Meldrum's Acids, and Arylhydroxylamines, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 38:6,
873-880, DOI: 10.1080/00397910701845365
To link to this article: http://dx.doi.org/10.1080/00397910701845365
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Synthetic Communicationsw, 38: 873–880, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701845365
Synthesis of 1-(2,6-Dimethylphenyl)-N-
hydroxy-4,4-dialkyl-2,5-dioxo-N-aryl-3-
pyrrolidine-carboxamides from Reaction of
2,6-Dimethylphenyl Isocyanide, Alkylidene
Meldrum’s Acids, and Arylhydroxylamines
Azizollah Habibi,1 Leyla Mousavifar,1,2 Mohammad
R. Yazdanbakhsh,2 and Issa Yavari3
1Faculty of Chemistry, Tarbiat Moallem University, Tehran, Iran
2Chemistry Department, Guilan University, Rasht, Guilan, Iran
3Chemistry Department, Tarbiat Modares University, Tehran, Iran
Abstract: Alkylidene Meldrum’s acids and 2,6-dimethylphenyl isocyanide react
smoothly in the presence of arylhydroxylamines at room temperature to produce
2,5-dioxo-pyrrolidines in fairly high yield.
Keywords: alkylidene Meldrum’s acid, 2,5-dioxopyrrolidine, heterocyclic synthesis,
isocyanide, three-component reaction
Multicomponent reactions (MCRs) are special types of useful organic
reactions in which three or more starting materials react to give a
product.[1] MCRs, by virtue of their convergence, productivity, facile
execution, and generally high yields of products, have attracted much
attention. Of pivotal importance in this area are the isocyanide-based MCRs
such as the versatile Ugi and Passerini reactions.[2] The discovery of novel
MCRs has become an increasingly active area of research, yielding novel
Received in Poland July 18, 2007
Address correspondence to Issa Yavari, Chemistry Department, Tarbiat Modares
University, P. O. Box 14115-175, Tehran, Iran. E-mail: yavarisa@modares.ac.ir
873

874
A. Habibi et al.
Scheme 1.
chemical scaffolds for drug discovery efforts. As part of our current studies on
the development of new routes to heterocyclic systems,[3,4] we now report the
reaction between 2,6-dimethylphenyl isocyanide (1) and alkylidene Meldrum’s
acids 2 in the presence of arylhydroxylamines 3, which led to 1-(2,6-dimethyl-
phenyl)-N-hydroxy-4,4-dialkyl-2,5-dioxo-N-aryl-3-pyrrolidine-carboxamides 4
in excellent yield (Scheme 1).
The reaction proceeded smoothly and was complete within 8 h. The 1H and
13C NMR spectra of the crude products clearly indicated the formation of 4. The
structures of compounds 4a–f were deduced from their elemental analyses and
1
their IR and H and 13C NMR spectra. The mass spectra of these compounds
displayed molecular ion peaks at the appropriate m/z values. Any initial frag-
mentation involved the loss of the ester and amide moieties.
1
The H NMR spectrum of 4a exhibited four single sharp lines readily
recognized as arising from tert-butyl (d 1.38 ppm), methyl (d 2.92 and
3
3.05 ppm) and methoxy (d 3.71 ppm) protons. Observation of J ¼ 1.7 Hz
for the vicinal methine protons in 4a indicates the presence of the trans
1
isomer (anti arrangement).[5] The H decoupled 13C NMR spectrum of 4a
showed 11 distinct resonances in agreement with the proposed structure.
1
The H and 13C NMR spectra of 4b–f are similar to those of 4a except for
the aryl and alkyl moieties, which exhibited characteristic signals with appro-
priate chemical shifts. In three cases, namely 4a–4c, both cis and trans
isomers (Scheme 2) were observed. The observation of two geometrical
Scheme 2.

2,5-Dioxo-Pyrrolidines
875
Figure 1. X-ray crystal structure of 4a (ORTEP-III plot; arbitrary numbering of
atoms).
isomers for these compounds is attributed to restricted rotation about the
partial double bond of the N-hydroxyamide moiety.[6]
Unambiguous evidence for the structure of 4a was obtained from a single-
crystal X-ray analysis. An ORTEP[7] diagram of 4a is shown in the Fig. 1.
There are four molecules of 4a in the unit cell.
1
3
The H and C NMR spectra of 4b and 4c show similar resonances that
arise from the presence of two rotamers, namely, (Z)-4 and (E)-4 (Scheme 2).
Although the mechanism of reaction between alkylidene Meldrum’s acid
and 2,6-dimethylphenyl isocyanide in the presence of arylhydroxylamines
was not established in an experimental manner, a plausible explanation is
proposed in Scheme 2. On the basis of the well-established chemistry of iso-
cyanides,[8] the reaction starts from [4 þ 1]-cycloaddition of 2 and 1,
producing an iminolactone intermediate 5. Conjugate addition by the hydro-
xylamine on the enone moiety of 5 followed by cleavage of the five-
membered ring gives 6 and hence the ketene 7 by electrocyclic ring
opening of the O-alkylated Meldrum’s acid (Scheme 3). The ketene 7 can
then undergo intermolecular reaction between the nitrogen of the hydroxyla-
mine and ketene moietiy to give product 4.
In conclusion, a convenient route to 1-(2,6-dimethylphenyl)-N-hydroxy-
4,4-diethyl-2,5-dioxo-N-aryl-3-pyrrolidine-carboxamides from
a one-pot
reaction of alkylidene Meldrum’s acids with 2,6-dimethylphenyl isocyanide
in the presence of arylhydroxylamines is described. These products may be
considered as potentially useful synthesis intermediates because they
possess atoms with different oxidation states. The advantage of the present

876
A. Habibi et al.
Scheme 3.
procedure is that the reaction is performed under neutral conditions by simple
mixing of the starting materials.
EXPERIMENTAL
Compounds 1 and 3 were obtained from Fluka and were used without further
purification. Compound 2 were prepared according to a known procedure.[2]
Melting points were determined with an Electrothermal 9100 apparatus, IR
1
spectra, Shimadzu IR-460 spectrometer; H and 13CNMR spectra, Bruker
DRX-300 Avance instrument in CDCl3 at 300 and 75 MHz, respectively,
with d in parts per million and J in hertz, EI-MS (70 eV), Finnigan-MAT-
8430 mass spectrometer in m/z; elemental analyses (C, H, N), Heraeus
CHN-O-Rapid analyzer.
General Procedure for the Preparation of Compounds 4
To a stirred solution of 2 (0.36 g, 2 mmol) and 3 (2 mmol) in anh. CH2Cl2
(10 ml), a mixture of 1 (2 mmol) in CH2Cl2 (5 ml) was added dropwise at
–58C, over 10 min. The mixture was then allowed to warm to rt and stirred
for 24 h. The solvent was removed under reduced pressure, and the residue
was purified by silica gel (SiO2; hexane/AcOEt 3:2) to afford the pure title
compounds.
Compound 4a
Colorless crystals, mp 157–1598C; IR (KBr), ¯v¼ 3190 (OH), 1711, 1719 and
1793 (3 C ¼ O) cm21. MS: m/z (%): 366 (Mþ, 4), 119 (26), 108 (40), 91 (59),

2,5-Dioxo-Pyrrolidines
877
83 (100), 78 (82), 56 (78). Anal. calcd. for C21H22N2O4 (366.41): C, 68.78; H,
6.0; N, 7.64%. Found: C, 67.92; H, 5.82; N, 7.52%. NMR data for the major
1
isomer (70%); H NMR: d ¼ 1.24 and 1.43 (6H, 2 s, CMe2), 1.93 and 2.28
(6H, 2 s, Me2Ar), 3.76 (1H, s, CH), 7.10–7.34 (8 CH, m, 2 Ar), 8.86 (1H,
s, OH) ppm. 13C NMR: d ¼ 17.4 and 19.8 (CMe2), 27.6 and 27.8 (Me2Ph),
44.6 (CMe2), 55.4 (CH), 121.1, 126.6, 128.3, 129.6, 130.0 (CH, Ph), 130.3,
(Cipso-N, phenyl), 135.3, (Cipso-N, Me2Ar), 162.5, 171.3, 182.4 (3 C55O)
1
ppm. NMR data for the minor isomer (30%); H NMR: d ¼ 1.31 and 1.59
(6H, 2 s, CMe2), 2.05 and 2.22 (6H, 2 s, Me2Ar), 4.51 (1H, 1s, CH), 7.10–
7.34 (8 CH, m, 2 Ph), 8.86 (1H, s, OH) ppm. 13C NMR: d ¼ 17.7 and 20.0
(CMe2), 27.6 and 31.2 (Me2Ph), 44.6 (CMe2), 57.2 (CH), 121.5, 126. 6,
128.3, 129.6, 130.0 (5 CH, Ph) 130.3, (Cipso-N, Ph) 135.3, (Cipso-N,
Me2Ph), 165.2, 174.7, 183.0 (3 C55O) ppm.
X-ray Crystal Structure of the Major Isomer of 4a
Structure determination and refinement of data: formula (C21H22N2O4),
˚
˚
Fw ¼ 364.41, monoclinic, Z ¼ 4, a ¼ 7.4991 (6) A, b ¼ 13.3360 (11) A,
3
˚
˚
c ¼ 19.3906 A, a ¼ 908, b ¼ 99.7168, g ¼ 908, V ¼ 3725.7 (4) A ,
Dcalcd ¼ 1.266 g cm23, R ¼ 0.0548, Rw ¼ 0.1089, 29ꢀ h ꢀ 9; 217 ꢀ k ꢀ
˚
14; 225 ꢀ l ꢀ 258; Mo (l ¼ 0.71073 A), T ¼ 120 (2) K. The crystallographic
data of 4a have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication number CCDC615090. Copies of the
data can be obtained, free of charge, via the Internet (http:// www.ccdc.cam.
ac.uk/data_request/cif), e-mail (data_request@ccdc.cam.ac.uk), or fax
(þ44-1223-336033).
Compound 4b
White powder, mp 150–1528C. IR (KBr), ¯v ¼ 3163 (OH), 1711, 1719 and
1793 (3 C55O) cm21. MS: m/z (%) ¼ 381 (Mþ, 4), 380 (Mþ 2 1, 30), 258
(38), 123 (72), 58 (71), 44 (76), 83 (100). Anal. calcd. for C22H24N2O4
(380.44): C, 69.39; H, 6.31; N, 7.36; Found: C, 68.57; H, 6.15; N, 7.15%.
1
NMR data for the major isomer (65%); H NMR: d ¼ 1.31 and 1.59 (6H, 2
s, CMe2), 2.05 and 2.22 (6H, 2 s, Me2Ar), 4.51 (1H, 1 s, CH), 7.10–7.34 (8
CH, m, 2 Ph), 8.86 (1H, s, OH) ppm. 13C NMR: d ¼ 17.7 and 20.0 (CMe2),
27.6 and 31.2 (Me2Ph), 44.6 (CMe2), 57.2 (CH), 121.5, 126.6, 128.3, 129.6,
130.0 (5 CH, Ph), 130.3 (Cipso-N, Ph), 135.3 (Cipso-N, Me2Ph), 165.2,
1
174.7, 183.0 (3 C55O) ppm. NMR data for the minor isomer (35%); H
NMR: d ¼ 1.26 and 1.47 (6H, 2 s, CMe2), 1.96 and 2.2 (6H, 2 s, Me2Ph),
2.39 (3H, 2 s, PhMe), 3.76 (1H, s, CH), 7.1–7.43 (8 CH, m, Ph), 8.6 (1H, s,
OH) ppm; 13C NMR: d ¼ 17.4 and 19.8 (CMe2), 21.0, and 27.6 (Me2Ph),
31.2 (p-MePh), 44.0 (CMe2), 55.3 (CH), 121.8, 127.6, 128.2, 128.8, 129.2,
129.5 and 130.6 (7 CH, 2 ph), 134.3 (Cipso, Me2Ph), 135.3 (Cipso, p-MePh),

878
A. Habibi et al.
136.6 (Cipso-N, Ph), 136.9 (Cipso-N, PhMe2), 161.8, 172.8, and 182.1 (3 C55O)
ppm.
Compound 4c
White powder, mp 1858C; IR (KBr), v¯ ¼ 3299 (OH), 1759, 1792 (3 C55O)
cm21. Anal. calcd. for C21H21BrN2O4 (445.31): C, 54.59; H, 4.72; N, 6.29.
Found: C, 54.25; H, 4.55; N, 6.10%. NMR data for the major isomer
1
(60%): H NMR: d ¼ 1.21 and 1.54 (6H, 2 s, CMe2), 1.92 and 2.21 (6H, 2
s, Me2Ph), 3.76 (1H, 1s, CH), 7.1–7.51 (7H, m, 2 Ph) 9.08 (1H, s, OH)
ppm; 13C NMR: d ¼ 17.4 and 19.8 (CMe2), 27.4 (Me2-Ph), 44.0 (CMe2),
55.6 (CH), 121.1, 126.5, 127.6, 128.4, 128.7, 130.2 and 130.4 (7 CH, 2 Ph),
135.3 (Cipso, Me2Ph), 136.5 (Cipso-Br, Ph), 136.8 (Cipso-N, p-BrPh), 137.5
(Cipso-N, Me2Ph), 161.8, 172.8 and, 182.1 (3 C55O) ppm. NMR data for the
1
minor isomer (40%): H NMR: d ¼ 1.42 and 1.55 (6H, 2 s, CMe2), 2.05
and 2.24 (6H, 2s, Me2Ph), 4.51 (1H, 1 s, CH), 7.1–7.51 (7H, m, Ph); 9.08
(1H, s, OH) ppm; 13C NMR: d ¼ 17.7 and 20.0 (CMe2), 27.7 (Me2Ph), 44.0
(CMe2), 57.2 (CH), 121.1, 126.5, 127.6, 128.4, 128.7, 130.0 and 130.5 (7
CH, Ph), 135.3 (Cipso, Me2Ph), 136.5 (Cipso-Br), 136.8 (Cipso-N, p-BrPh),
137.5 (Cipso-N, Me2Ph), 167.0, 174.7 and 183.0 (3 C55O) ppm.
Compound 4d
White powder; mp 145–1478C, IR (KBr), v¯ ¼ 3420 (OH), 1724, 1742, 1772
(3 C55O) cm21; MS: m/z (%) ¼ 416 (Mþ, 4), 186 (12), 159 (99), 130 (30), 83
(100), 55 (46), 57 (44). Anal. calcd. for C25H24N2O4 (416.47): C, 72.04; H,
1
5.76; N, 6.72, Found: C, 71.75; H, 5.45; N, 6.50%. H NMR: d ¼1.64, 1.76
(6H, 2 s, CMe2), 2.06, 2.07 (6H, 2 s, Me2Ph), 4.13 (1H, 1 s, CH), 7.1 (3H,
s, C6H3), 7.34–9.05 (7H, m, naphthyl), 11.02 (1H, s, OH) ppm; 13C NMR:
d ¼17.7 (CMe2), 30.7 (Me2-Ar). 43.3 (CMe2), 51.2 (CH), 120.0, 122.2,
123.0, 126.6, 126.6, 126.9, 127.1, 127.2, 127.6, 128.1 and 131.3 (11 CH,
phenyl and naphthyl), 135.1 (Cipso-N, naphthyl), 135.8 (C2-naphthyl), 140.9
(Cipso-N, PhMe2), 164.4, 164.9 and 174.9 (3 C55O) ppm.
Compound 4e
White powder; mp 195–1978C. IR (KBr): v¯ ¼ 3289 (OH), 1715 and 1771,
(C55O) cm21. MS: m/z (%) ¼ 470 (Mþ, 12), 264 (12), 183 (58), 182 (56),
159 (38), 143 (78), 120 (100), 115 (54). Anal. calcd. for C29H30N2O4
(470.57): C, 73.95; H, 6.38; N, 5.95%. Found: C, 73.5; H, 6.15; N, 5.74%.
1H NMR: d ¼ 1.41–1.96 (10H, m, C6H10), 2.07 (6H, 1 s, Me2Ph), 4.13 (1H,
1 s, CH), 7.01 (3H, s, C6H3), 7.62–9.10 (7H, m, naphthyl), 11.26 (1H, s,
OH) ppm. 13C NMR: d ¼ 17.7 (CMe2), 30.7 (Me2Ph), 43.3 (CMe2), 51.2
(CH), 120.0, 122.2, 123, 126. 6, 126.6, 126.9, 127.1, 127.2, 127.6, 128.1 and

2,5-Dioxo-Pyrrolidines
879
131.3 (11 CH, phenyl and naphthyl), 135.1 (Cipso-N, naphthyl), 135.8 (C2-
naphthyl), 140.9 (Cipso-N, PhMe2), 164.4, 164.9 and 174.9 (3 C55O) ppm.
Compound 4f
White powder; mp 205–2078C. IR (KBr): v¯ ¼ 3381 (OH), 1700 and 1715
(C ¼ O) cm21. MS: m/z (%) ¼ 499 (Mþ, 9), 298 (14), 159 (100), 143 (48),
123 (46), 83 (62), 57 (82), 55 (100). Anal. calcd. for C25H27BrN2O4
(499.40): C, 60.07; H, 5.41; N, 5.61%. Found: C, 59.5; H, 5.30; N, 5.40%.
1H NMR: d ¼ 1.60–2.10 (10H, m, C6H10), 2.0, (6H, 1 s, Me2Ph), 4.78 (1H,
1 s, CH), 7.03–7.85 (7H, m, 2 Ph), 11.61 (1H, s, OH) ppm. 13C NMR:
d ¼ 17.7 (CMe2), 32.2 (Me2Ph), 48.3 (CMe2), 53.5 (CH), 121.2, 126.7,
126.9 128.6, 129.6, 130.1 and 131.4 (7 CH, 2 phenyl), 131.4 (Cipso, Me2Ph),
135.1 (Cipso-N, p-BrPh), 135.8 (Cipso-Br, Ph), 140.9 (Cipso-N, PhMe2),
166.4, 167.9 and 174.1 (3 C55O) ppm.
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