Facile and convenient synthesis of functionalized aryl-containing isoindigo derivatives via substituted indolin-2-one carbene dimerization

Article abstract of DOI:10.1080/00397911.2011.558232

The reaction of substituted benzyl-, aroylmethyl-, or 1-phenetylisatins with hexaethyltriaminophosphine has been shown to lead to the formation of a library of 3,3-biindolinylidene-2,2-diones with functionalized benzyl-, aroylmethyl-, and 1-phenetyl fragm

Full text of DOI:10.1080/00397911.2011.558232

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Facile and Convenient Synthesis of
Functionalized Aryl-Containing Isoindigo
Derivatives via Substituted Indolin-2-one
Carbene Dimerization
Andrei V. Bogdanov a , Vladimir F. Mironov a , Lenar I. Musin a ,
Rashid Z. Musin a , Dmitry B. Krivolapov a & Igor A. Litvinov a
a A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan
Research Center, Russian Academy of Sciences, Kazan, Russia
Accepted author version posted online: 15 Dec 2011.Version of
record first published: 14 May 2012.
To cite this article: Andrei V. Bogdanov, Vladimir F. Mironov, Lenar I. Musin, Rashid Z. Musin, Dmitry
B. Krivolapov & Igor A. Litvinov (2012): Facile and Convenient Synthesis of Functionalized Aryl-
Containing Isoindigo Derivatives via Substituted Indolin-2-one Carbene Dimerization, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
42:16, 2388-2395
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Synthetic Communications1, 42: 2388–2395, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.558232
FACILE AND CONVENIENT SYNTHESIS OF
FUNCTIONALIZED ARYL-CONTAINING ISOINDIGO
DERIVATIVES VIA SUBSTITUTED INDOLIN-2-ONE
CARBENE DIMERIZATION
Andrei V. Bogdanov, Vladimir F. Mironov, Lenar I. Musin,
Rashid Z. Musin, Dmitry B. Krivolapov, and Igor A. Litvinov
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Research
Center, Russian Academy of Sciences, Kazan, Russia
GRAPHICAL ABSTRACT
Abstract The reaction of substituted benzyl-, aroylmethyl-, or 1-phenetylisatins with hex-
aethyltriaminophosphine has been shown to lead to the formation of a library of
3,30-biindolinylidene-2,20-diones with functionalized benzyl-, aroylmethyl-, and 1-phenetyl
fragments at the nitrogen atom.
Keywords Carbenes; deoxygenation reaction; isatin; isoindigo; phosphorus
INTRODUCTION
Isoindigo (3,30-biindolinyliden-2,20-dione) and its nitrogen-functionalized deri-
vatives have recently attracted a great deal of attention as intermediates in the syn-
thesis of some polyindoline alkaloids[1–6] and as substances that possess a wide range
of biological activity.[7–11] Recently, two patents[12,13] described a method for the
treatment of cancer with the use of 1-(b-D-O-triacetylxylopyranosyl)-isoindigo
(Natura) or 1-methylisoindigo (Meisoindigo). In addition, 1-(b-D-glucopyranosyl)-
isoindigo was found to be an effective antileukemia drug.[14,15] Recently, synthesis
of isoindigo-based oligothiophenes and their utilization as electron donors in mol-
ecular bulk-heterojunction solar cells have also been reported.[16] It should be noted
that at this time there are only a few publications[17–19] concerning the synthesis of
isoindigos containing aryl substituents at the nitrogen atom. As part of our ongoing
Received November 22, 2010.
Address correspondence to Andrei V. Bogdanov, A. E. Arbuzov Institute of Organic and Physical
Chemistry, Kazan Research Center, Russian Academy of Sciences, Arbuzow str. 8, Kazan 420088, Russia.
E-mail: bogdanov@iopc.ru
2388

ARYL DERIVATIVES OF ISOINDIGO
2389
studies concerning the preparation of novel isoindigo derivatives with potent biolo-
gically active properties,[20–22] we herein report the synthesis of isoindigo derivatives
containing the arene moiety in the substituent at the nitrogen atom.
In a general case, treatment of benzylisatin 1a (2.64 mmol) with hexaethyl-
triaminophosphine 2 (2.64 mmol) in dichloromethane at ꢀ60 ꢁC for 10 min furnished
corresponding 1,10-dibenzyl-3,30-biindolinyliden-2,20-dione 3a in 81% yield
(Scheme 1). Using infrared (IR) and 13C NMR spectroscopic data, we have estab-
lished the regiochemistry of deoxygenation of isatin derivatives 1a–f. It should be
noted that synthesis of N-aryl indigo derivatives, which are the structural isomers
of isoindigo, conclude in the reaction of corresponding aryl iodides or bromide with
indigo in o-dichlorobenzene under strict conditions.[23]
Thus, comparing the IR spectra of starting arylmethylisatins 1a–f and reaction
products shows that a band at 1740–1730 cmꢀ1, corresponding to ‘‘pure’’ carbonyl
group, disappears while the amide carbonyl band at 1682–1693 cmꢀ1 is retained.
In addition, the 13C NMR spectrum of compound 3f displayed only one low-field
signal at 167.7 ppm corresponding to a carbonyl C2 atom. The signal of olephinic
3
C3 appears at 133.4 ppm as a doublet with JHCCC 1.1 Hz, which in this case is less
3
than the usual JHH aromatic spin–spin coupling constant, due to the geometry of
the molecule. Generally, interpretation of 13C NMR spectra of all compounds
3a–f are in good accordance with those published for 1,10-dimethylisoindigo.[24]
The structure of 3a was confirmed by x-ray crystallographic analysis (Fig. 1). The
molecule is in the general position of the asymmetrical part of the crystal of
compound 3a. Indole cycles C1C2N3C3aC4C5C6C7C7a and C1bC2bN3bC4cC4bC5b-
C6bC7bC7c are planar to within 0.014(3) and 0.061(3) A respectively. It should be
˚
noted that the whole molecule is nonplanar and the angle of turn of indole fragments
at the C1–C1b double bond is 16.62(10)o. Benzyl substituents at the nitrogen atoms
Scheme 1. Synthesis of 3a–f by reaction of isatins with hexaethyltriaminophosphine.

2390
A. V. BOGDANOV ET AL.
Figure 1. ORTEP diagram of 1,10-dibenzyl-3,30-biindolinylidene-2,20-dione 3a. Thermal ellipsoids are
drawn at 50% probability.
are located almost perpendicular to the indole fragments [torsion angles C3A–N3–C8–
C9 and C3C–N3C–C8B–C9B are ꢀ77.5(3)ꢁ and 90.2(3)o respectively]. The distribution
of bond lengths in the five-membered cycles indicates conjugation of the benzene frag-
ment with the lone pair of nitrogen atom N1 (N1b) and C2 ¼ O2 (C2b ¼ O2b) double
3
2
bond [bonds lengths are N3–C3A 1.399(3) A, N –C 1.365 (4) A, N3C–C2B 1.364(4)
˚
˚
A, N3C–C3C 1.394(3) A].
˚
˚
A probable mechanism of this reaction is proposed in Scheme 2. The first stage
of the reaction may involve a one-electron transfer from phosphorus to the hetero-
cyclic system to form an ion-radical pair followed by P-O bond formation. Then,
plausible phosphonium salt may eliminate hexaethyltriaminophosphine oxide to give
indolin-2-one carbene, which in the reaction medium undergoes dimerization to
form the final products.
In conclusion, a facile and convenient synthesis of aryl-containing iso-
indigo derivatives was achieved. The key step for the synthesis of a library of novel
Scheme 2. Probable mechanism of the reaction.

ARYL DERIVATIVES OF ISOINDIGO
2391
isoindigos is an intermediate formation of indolin-2-one carbenes. Moderate to good
yields and easy workup procedure are the advantages of this approach.
EXPERIMENTAL
Commercially available isatin and alkyl bromides for the preparation of
N-substituted isatins were used. All melting points are uncorrected. Mass spectra
were recorded on a DFS Thermo Electron Corporation (USA) mass spectrometer
operating at an ionization potential of 70 eV. IR spectra were measured with a
1
Bruker Vector-22 spectrometer as suspension in nujol. H and 13C NMR spectra
were recorded on a Bruker Avance-400 spectrometer at 400 and 100.6 MHz, respect-
1
ively. H and 13C NMR spectra were obtained in solution in deuterated dimethyl-
sulfoxide (DMSO-d6) or deuterated chloroform (CDCl3). The x-ray diffraction
data for the 3a were collected on a Bruker Smart Apex II CCD diffractometer using
graphite monochromated Mo Ka (0.71073) radiation.
General Procedure
A solution of hexaethyltriaminophosphine (0.69 ml, 2.64 mmol) in dichloro-
methane (3 ml) was added dropwise to a solution of appropriate 1-alkylisatin
(2.64 mmol) in the same solvent (10 ml) at ꢀ60 ꢁC with bubbling of dry argon for
2 min. The reaction mixture was then allowed to warm to room temperature. The
solid was filtered, washed with dry hexane, and dried in vacuo (12 Torr) to give
the pure product. If this procedure does not give any solids, the reaction mixture
is evaporated in vacuo (12 Torr) to dryness. The residue is treated with 10 ml of
dry hexane to give a precipitate, which was separated as described previously.
1,1’-Dibenzyl-3,3’-biindolinylidene-2,2’-dione (3’)
1
Dark red crystals; mp 234 ꢁC (lit.[1] 228–229 ꢁC). Assignment of signals in H
and 13C NMR spectra was made on the basis of signal multiplicities and is in good
agreement with published data.[1]
1,1’-Bis-(4-methylbenzyl)-3,3’-biindolinylidene-2,2’-dione (3b)
Red powder; mp 261 ꢁC. TLC: Rf 0.91 (n-hexane–acetone, 1:1). IR (nujol)
(nmax, cmꢀ1): 1682 (C O), 1603 (C C), 1455, 1228. Because of the very low solu-
bility of this compound in a wide range of organic solvents, 1H and 13C NMR spec-
tra were not recorded. Calcd. for C32H26N2O2: C, 81.68; H, 5.57; N, 5.95. Found: C,
81.55; H, 5.37; N, 5.87. MS (m=z, %): 470 [Mþ, 13].
=
=
1,1’-Bis-(3,5-dimethylbenzyl)-3,3’-biindolinylidene-2,2’-dione (3c)
Dark red powder; mp 246–248 ꢁC. TLC: Rf 0.79 (n-hexane–EtOAc, 3:1). IR
(nujol) (nmax, cmꢀ1): 1691 (C ¼ O), 1607 (C ¼ C), 1465, 1434, 1223. Calcd. for
C34H30N2O2: C, 81.90; H, 6.06; N, 5.62. Found: C, 81.69; H, 5.99; N, 5.41. MS
1
(m=z, %): 498 [Mþ, 35]. H NMR (400 MHz, CDCl3) d 2.28 (6H, s, CH3), 4.94

2392
A. V. BOGDANOV ET AL.
(2H, s, CH2), 6.72 (1H, dd, J ¼ 7.9, J ¼ 0.6, aromatic), 6.89 (1H, m, aromatic), 6.94
(1H, m, aromatic), 7.05 (m, 1H), 7.28 (1H, m), 9.24 (1H, dd, J¼ 8.0, J ¼ 1.0). 13C
1
1
NMR (100.6 MHz, CDCl3) d 21.3 (q, JHC ¼ 126 Hz, CH3), 43.7 (tm, JHC ¼ 139 Hz,
1
3
3
CH2), 108.7 (dd, JHC ¼ 162 Hz, JHC ¼ 8 Hz, C7), 121.7 (d, JHC ¼ 7Hz, C3a), 122.4
(dd, JHC ¼ 161 Hz, JHC ¼ 7Hz, C5), 124.9 (dm, Cortho), 129.3 (dm, JHC ¼ 155 Hz,
1
3
1
3JHC ¼ 9Hz, Cpara), 129.9 (dm, C4), 132.5 (dd, JHC ¼ 160 Hz, JHC ¼ 6 Hz, C6),
1
3
133.6 (m, C3), 135.6 (m, Cipso), 138.4 (m, Cmeta), 144.7 (m, C ), 168.1 (m, C O).
7a
=
1,1’-Bis-(4-methoxycarbonylbenzyl)-3,3’-biindolinylidene-2,2’-dione (3d)
Dark pink powder; mp 296–298ꢁC. TLC: Rf 0.49 (n-hexane–acetone, 2:1). IR
(nujol) (nmax, cmꢀ1): 1722 (C ¼ O), 1692 (C O), 1608 (C ¼ C), 1577, 1286. Calcd.
=
for C34H26N2O6: C, 73.11; H, 4.69; N, 5.02. Found: C, 72.99; H, 4.48; N, 4.89.
MS (m=z, %): 558 [Mþ, 100]. 1H NMR (400 MHz, d6-DMSO) d 3.89 (3H, s,
CH3), 5.07 (2H, s, CH2), 6.66 (1H, d, J ¼ 7.8, aromatic), 7.06 (1H, m, aromatic),
7.28 (1H, m, aromatic), 7.40 (2H, d, J ¼ 8.2, aromatic), 7.40 (2H, d, J ¼ 8.0, aro-
matic), 9.22 (1H, d, J ¼ 8.1, aromatic). 13C NMR (100.6 MHz, d6-DMSO) d 43.5
1
1
1
(tm, JHC ¼ 139 Hz, CH2), 52.1 (q, JHC ¼ 147 Hz, CH3), 108.5 (dd, JHC ¼ 161 Hz,
3JHC ¼ 8 Hz, C7), 121.7 (m, C3a), 122.8 (dd, JHC ¼ 161 Hz, JHC ¼ 6 Hz, C5), 127.1
1
3
(dm, Cortho), 129.7 (t, JHC ¼ 7 Hz, Cpara), 130.1 (dd, JHC ¼ 164 Hz, JHC ¼ 6 Hz,
3
1
3
Cmeta), 130.2 (dm, C4), 132.6 (dm, C6), 133.5 (m, C3), 140.9 (t, JHC ¼ 4 Hz, Cipso),
3
144.2 (m, C7a), 166.7 (m, C ¼ O), 168.1 (m, C ¼ O).
1,1’-Bis-(2-(4-diethylaminophenyl)-2-oxo-ethyl)-
3,3’-biindolinylidene-2,2’-dione (3e)
Crimson powder, mp 222–224ꢁC. TLC: Rf 0.42 (n-hexane–EtOAc, 3:2). IR
(nujol) (nmax, cmꢀ1): 1731 (C ¼ O), 1672 (C O), 1592 (C ¼ C), 1354, 1251. Calcd.
=
for C40H40N4O4: C, 74.98; H, 6.29; N, 8.74. Found: C, 74.77; H, 6.01; N, 8.69.
1
MS (m=z, %): 643 [Mþ, 22]. H NMR (400 MHz, CDCl3) d 1.21 (6H, t, J ¼ 7.0,
CH3), 3.43 (4H, q, J ¼ 7.0, CH2), 5.11 (2H, s, CH2), 6.64–6.67 (3H, m, aromatic),
7.02 (1H, m, aromatic), 7.27 (1H, m, aromatic), 7.93 (2H, d, J ¼ 8.9, aromatic),
9.19 (1H, d, J ¼ 8.0, aromatic). 13C NMR (100.6 MHz, CDCl3) d 12.5, 44.6,
45.8, 108.3, 110.4, 121.8, 121.9, 122.3, 129.9, 130.8, 132.3, 133.4, 144.8, 151.7,
168.1, 189.5.
1,1’-Bis(2-phenylethyl)-3,3’-biindolinylidene-2,2’-dione (3f)
Red powder, mp 195–197ꢁC. TLC: Rf 0.67 (n-hexane–EtOAc, 3:1). IR (nujol)
(nmax, cmꢀ1): 1693 (C ¼ O), 1608 (C ¼ C), 1353, 1253. Calcd. for C32H26N2O2: C,
81.68; H, 5.57; N, 5.95. Found: C, 81.47; H, 5.42; N, 5.69. MS (m=z, %): 470
1
[Mþ, 45]. H NMR (400 MHz, CDCl3) d 3.02 (2H, m, CH2), 4.02 (2H, m, CH2),
6.75 (1HSS, d, J ¼ 7.8, aromatic), 7.07 (1H, ddd, J ¼ 7.6, J ¼ 7.9, J ¼ 1.0, aromatic),
7.23–7.33 (5H, m, aromatic), 7.35 (1H, dt, J ¼ 7.7, J ¼ 1.1, aromatic), 9.17 (1H, d,
1
J ¼ 8.0, aromatic). 13C NMR (100.6 MHz, CDCl3) d 33.8 (t, JHC ¼ 129 Hz,
1
3
1
NCH2), 41.7 (tt, JHC ¼ 140 Hz, JHC ¼ 5 Hz, CH2-Ph), 107.7 (dd, JHC ¼ 161 Hz,
3JHC ¼ 8 Hz, C7), 121.7 (m, C3a), 122.2 (dd, JHC ¼ 162 Hz, JHC ¼ 7 Hz, C5), 126.7
1
3

ARYL DERIVATIVES OF ISOINDIGO
2393
Table 1. Crystal data and structure refinement for 3a
Parameter
Value
Formula
Mw
C
30H22N2O2
442.50
Red
Crystal color
Crystal size (mm3)
Crystal system
Space group
0.3 ꢂ .0.2 ꢂ 0.2
Monoclinic
P 21=c
˚
a (A)
11.525 (11)
8.370 (8)
23.26 (2)
90
˚
b (A)
˚
c (A)
a (o)
b (o)
c (o)
101.389 (12)
90
3
˚
V=A
2200 (3)
4
1.336
Z
Dc (g cmꢀ3
m(Mo-Ka) (mmꢀ1
No. of unique data
No. parameters refined
No. refl. in refinement
R
)
)
0.084
4323
395
4323; I ꢃ 2r:2228
0.0560 [F2 > 2rF2]
0.1134
WR
Goodness of fit
˚
Residual Fourier e. (A
0.956
ꢀ0.154; 0.140
ꢀ3
)
w ¼ 1=[nr2(Fo2) þ (0.0561P)2 þ 0.0000P] where P ¼ (Fo2 þ 2Fc2)=3.
1
3
1
3
(dd, JHC ¼ 162 Hz, JHC ¼ 7 Hz, Cpara), 128.7 (dd, JHC ¼ 160 Hz, JHC ¼ 7 Hz,
Cmeta), 128.8 (dm, Cortho), 129.9 (dd, JHC ¼ 167 Hz, JHC ¼ 7 Hz, Cpara), 132.3
7a
1
3
1
3
3
(dd, JHC ¼ 167 Hz, JHC ¼ 7 Hz, C6), 133.4 (d, JHC ¼ 1 Hz, C3), 138.3 (t, Cipso),
=
144.4 (m, C ), 167.7 (m, C O).
X-Ray Crystallography
CCDC-800822 for 3a contains the supplementary crystallographic data for this
article. It can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrie-
ving.html [or from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax (internat.): 44-1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk]. A summary of the crystal data, data collection, and refinements
is given in Table 1.
ACKNOWLEDGMENTS
Financial support by the Council on Grants of the President of the Russian
Federation (Grant MK-1670.2010.3) and by the Russian Foundation for Basic
Research (Grant 09-03-00933) is gratefully acknowledged.

2394
A. V. BOGDANOV ET AL.
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