Efficient synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3- dihydroisoindolinone derivatives via a simple and convenient MCR in aqueous micellar system

Article abstract of DOI:10.1016/j.tetlet.2013.05.151

An environmentally benign and operationally simple methodology was developed for the synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3- dihydroisoindolinones via multicomponent one-pot reaction involving 2-iodo-N-phenylbenzamides, terminal alkyne, and substituted indoles in aqueous micellar medium. It involves copper-mediated domino Sonogashira-5-exo-dig- cyclization followed by regioselective nucleophilic addition of indoles, all in one-pot, using CuI as catalyst and 2,2′-(1E,1′E)-(1R,2R)- cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)diphenol as ligand under aerobic condition.

Full text of DOI:10.1016/j.tetlet.2013.05.151

Accepted Manuscript
Efficient synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-dihydroisoindoli‐
nones derivatives via a simple and convenient MCR in aqueous micellar system
Swarbhanu Sarkar, Rammyani Pal, Asish Kumar Sen
PII:
S0040-4039(13)00943-X
DOI:
http://dx.doi.org/10.1016/j.tetlet.2013.05.151
TETL 43052
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
26 April 2013
29 May 2013
31 May 2013
Please cite this article as: Sarkar, S., Pal, R., Sen, A.K., Efficient synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-
dihydroisoindolinones derivatives via a simple and convenient MCR in aqueous micellar system, Tetrahedron
Letters (2013), doi: http://dx.doi.org/10.1016/j.tetlet.2013.05.151
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GRAPHICAL ABSTRACT:
Efficient synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-
dihydroisoindolinones derivatives via a simple and convenient
MCR in aqueous micellar system
Swarbhanu Sarkar, Rammyani Pal, Asish Kumar Sen*

Efficient synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-dihydroisoindolino-
nes derivatives via a simple and convenient MCR in aqueous micellar system
Swarbhanu Sarkar, Rammyani Pal, Asish Kumar Sen*
Chemistry Division, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road,
Jadavpur, Kolkata-700 032, India.
*Corresponding author. Fax: +91 33 24735197; Tel: +91 33 24995720.
E-Mail: asishksen@yahoo.com; aksen@iicb.res.in (A. K. Sen)
Abstract: An environmentally benign and operationally simple methodology was developed for
the synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-dihydroisoindolinones via multicomponent
one-pot reaction involving 2-iodo-N-phenylbenzamides, terminal alkyne and substituted indoles
in aqueous micellar medium. It involves copper-mediated domino Sonogashira-5-exo-dig-
cyclization followed by regioselective nucleophilic addition of indoles, all in one-pot, using CuI
as catalyst and 2,2'-(1E,1'E)-(1R,2R)-cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-
yl-1-ylidene)diphenol as ligand under aerobic condition.
Keywords: Cu-mediated Sonogashira; 5-Exo-dig cyclization; Regioselective addition; Indole;
Micelle; Ligand; Reaction in water.
Recent challenges in organic synthesis encompass the development of environmentally
benign chemical processes that afford products of greater structural complexity from relatively
simple starting materials with fewer synthetic steps but ensuring high yield.1 In this respect
tandem reactions,2 where multiple transformations could be performed in one-pot, have emerged
as an efficient tool. Significant developments in this area have been made over past few decades
and a number synthetic methodologies are reported in the literature.2 However, for growing
environmental concern it would be more pertinent that concerted efforts should be made for
establishing organic reactions under non hazardous eco-friendly conditions. Towards this
endeavour, reactions in aqueous medium may be a suitable alternative.3 But, limited solubility of
organic compounds in water actually prevents the execution of reactions in aqueous media.
However, this may be overcome to some extent through the introduction of aqueous surfactant in
the form of a micelle. In micellar catalysis, the surfactant micelles accumulate reacting
molecules within its small internal cavity with different orientations, which may influence the

reaction mechanism, resulting in remarkable differences in product formation compared to
homogeneous catalysis.4
Substituted indole and oxindole scaffolds show important pharmacological properties like
anti-hypertensive, anti-viral, anti-leukemic or anti-inflammatory activity.5 These scaffolds may
often serve as templates and guide to new molecules.
Transition metal catalyzed selective C-H and C-C bond functionalization is an attractive
strategy to the cross-coupling reaction and have provided a plethora of structurally unique
compounds.6 Normally, expensive palladium-, rhodium-, and ruthenium-salts having bidentate
N,P- or N,N-ligands are used widely in such a reaction.7 However, recently immense progress
has been made with inexpensive and low-toxic copper catalysts and it exhibits wide applicability
and good functional group tolerance.8 Palladium-free, copper mediated Sonogashira-type
coupling reactions are one promising improvement of this variant.9 However, it should be
remembered that the use of copper often introduces Glaser-type homocoupling products.10 The
scope of copper catalyzed reactions in domino Sonogashira-5-exo-dig-cyclization-regioselective
nucleophilic addition under one-pot condition has not been investigated thoroughly.
Generally these reactions are conducted in high-boiling, polar solvents like DMF at
relatively higher temperature.11 It is well established that the presence of ancillary ligand which
chelates the metal center often increases the efficiency of the metal-catalyst possibly by
increasing its solubility, stability and/or by preventing the it‟s aggregation. So, introduction of
appropriate ligand12 with high binding propensity often improves the efficiency of metal-
catalyzed cross-coupling reaction. We explored a convenient, simple and green methodology for
the synthesis of 3-benzyl-3-(indol-3-yl)-2-phenyl-2,3-dihydroisoindolinones in aqueous miceller
environment using salen-type ligand 1g (Figure 1). The method allows palladium-free domino
Sonogashira-cyclization of o-bromo or o-iodo-N-phenylbenzamides with terminal alkyne
followed by regioselective addition of indole, all in one-pot. The method excludes the use of
palladium, organic solvents, phosphine ligands, or the presence of any additional activator. A
library of indolyl isoindolinones could thus be obtained in high yield and in short reaction time.
The uniqueness of the protocol lies in its eco-friendly operation, generation of structurally unique
molecules and excellent yield.

OH
N
OH
N
OH
N
OH
N
OH
OH
OH
N
MeO
NEt2
1b
1d
1c
1a
N
N
N
N
N
N
OH HO
N
N
OH HO
1e
1f
1g
Figure 1. Ligands used in the study.
At the outset, we opted 2-iodo-N-phenylbenzamide (2a), phenylethyne (3) and indole (4a)
as model reactants and investigated the feasibility of a palladium-free copper catalyzed
„Sonogashira coupling-cycloisomerization-regioselective nucleophilic addition‟ domino strategy
to produce indolyl isoindolinone (5a) in aqueous medium (Scheme 1). Initially, to determine the
optimal reaction conditions several commercially available amphiphiles, including Triton X-114,
CTAB (cetyltrimethylammonium bromide) and SDS (sodium dodecylsulfate) were tested (Table
1). Also included were PTS (polyoxyethanyl--tocopheryl sebacate), PSS (vitamin E subsection
of PTS replaced with -sitosterol form “PSS”) and TPGS (α-tocopherol polyethylene glycol
succinate).13 The effect of different ligands was also examined using PTS in water at 80 °C in
presence of Et3N as base for 2 h. These include various salicylaldoxime (1a-1d) and salen-type
ligands (1e-1g). Better yield was observed in case of 1f (81%) or 1g (87%), with one extra
phenol or pyridine type-binding site, compared to 1e (60%). This is probably because of the
restricted rotation of C-C bond due to the fused ring type structure, which increases its binding
efficiency. This type of ligands may also stabilize active copper(I) species by favoring the
formation of tetrahedral structure rater than square planar structure that are found to be more
common with copper(II) species.14 Use of salicylaldoxime ligands (1a-1d) was not found as
effective (gave poor to moderate yield in repetitive experiments). It is worth mentioning that in
the absence of supporting ligand the reaction did not produce reasonable amount of indolyl

isoindolinones, rather 1,4-diphenylbuta-1,3-diyne was formed as a major product due to the
homocoupling of 3 through Glaser-type reaction, mentioned earlier.
O
Cu (I)
O
I
N
Ph
Surfactant, Base
N
N
H
H
H2O, Ligand
80 oC
N
H
3
4a
2a
5a
Scheme 1. Synthesis of 5a in aqueous micellar medium.
Several control reactions were then performed to highlight the role of surfactants. The strategy
was most successfully carried out when performed using PTS (15 wt%) and Et3N as base (Table
1, entry 1) at 80 °C. However, lowering its concentration below 15 wt% led to reduced product
formation (Table 1, entry 2). Reactions were also performed using PTS/H2O+pH 10 buffer
(Table 1, entry 3) but gave low yield suggesting that aqueous basic medium was not suitable.
Use of other neutral or ionic surfactants also resulted a decrease in the product formation. TPGS,
PSS and Triton X-114 gave the products in 72, 68 and 67 % yield respectively (Table 1, entry 4,
5 & 6), whereas, ionic surfactants such as SDS (54%, Table 1, entry 7) and TTAB (58%, Table
1, entry 8) gave significant lower yield.
The effect of different organic and inorganic bases, viz. Et3N, DABCO, TMEDA, DBU, K2CO3
and Cs2CO3 was investigated (Table 2). Et3N appeared to be the most effective when employed
in 2.0 molar equiv. and afforded the product in maximum yield (Table 2, entry 7). The results
concluded that organic bases worked well in comparison to inorganic bases.

Table 1. Effect of the different surfactants on the yield of 5a
Entrya
Surfactant
PTS
Concentration
15 wt%
5 wt%
Yieldb (%)
1
2
3
4
5
6
7
8
76
22
17
72
68
67
54
58
PTS
PTS+pH-10 buffer
TPGS
15 wt%
15 wt%
15 wt%
80 mM
PSS
Triton X-114
SDS
80 mM
TTAB
80 mM
aAll reactions were performed using 2a (1 mmol), 3 (1.5 mmol) and 4a (1.5 mmol) in water at 80
°C for 2 h under aerobic condition.
bYield of isolated pure product; catalyst used CuI (10 mol%), ligand 1g (25 mol%), Et3N (2.0
mmol). Some loses during isolation is unavoidable in certain cases.
Table 2. Effect of the different bases on the yield of 5a
Entrya
Base
Cs2CO3
K2CO3
DBU
Amount (mmol) Time (h) Yieldb (%)
1
2
3
4
5
6
7
8
1.0
1.0
1.0
1.0
1.0
1.0
2.0
2.5
1
1
1
1
1
1
1
1
34
32
62
59
64
68
76
76
DABCO
TMEDA
Et3N
Et3N
Et3N
aAll reactions were performed using 2a (1 mmol), 3 (1.5 mmol) and 4a (1.5 mmol) in water at 80
°C for 2 h under aerobic condition in presence of PTS (15 wt%), CuI (10 mol%) and ligand 1g
(25 mol%).
bYield of isolated pure product; some loses during isolation is unavoidable in certain cases.
To explore the scope and generality of this methodology, the protocol was then applied to a
variety of N-substituted benzamides and indoles (Table 3). All the reactions yielded only indolyl-
dihydro-isoindolinones as major product and the structures of all the products were confirmed by
IR, NMR and MS spectroscopy. With unsubstituted or N-substituted indoles, reactions were

found to occur at C-3. However, it is interesting to note that with 3-substituted indoles, reaction
occurred at C-2 in good yield (Table 3, entry 8). It is notable that, corresponding aryl bromide
2d, gave low yield under our reaction condition (Table 3, entry 9).
Table 3. Reactions of 2-iodo-N-phenylbenzamide (2a-d), phenyl acetylene (3) and indoles (4a-
4f) leading to indolyl-dihydroisoindolinones (5a-i) in aqueous micellar medium
Entrya
Amide
Indole
Product
Yieldb (%)
R1
O
N
R1
R2
O
R2
Ph
N
H
N
R3
I
N
R3
1
2
3
4
5
6
2a: R1 = H
4a: R2 = H; R3 = H
4b: R2 = OMe; R3 = H 5b: R1 = H; R2 = OMe; R3 = H
4c: R2 = NO2; R3 = H
4d: R2 = H; R3 = Me
5a: R1 = H; R2 = H; R3 = H
76
72
80
78
67
63
2a
5c: R1 = H; R2 = NO2; R3 = H
5d: R1 = H; R2 = H; R3 = Me
5e: R1 = F; R2 = H; R3 = H
2a
2a
2b: R1 = F
2c: R1 = OMe
4a
4a
5f: R1 = OMe; R2 = H; R3 = H
O
N
CH3
N
H
7
79
2a
Ph
CH3
N
H
4e
5g
O
CH3
N
H3C
8
9
71
32
2a
N
H
Ph
NH
4f
5h
5a
O
N
H
4a
Br
2d

O
N
OMe
O
I
R2
Ph
N
OMe
H
10
67
4a
N
R3
2e
5i: R2 = H; R3 = H
aAll reactions were performed using 2 (1 equiv.), 3 (1.5 equiv.) and 4 (1.5 equiv.) in water at 80
°C for 2 h under aerobic condition in presence of PTS (15 wt%), CuI (10 mol%), Et3N (2 equiv.)
and ligand 1g (25 mol%).
bYield of isolated pure product; some loses during isolation is unavoidable in certain cases.
The above catalytic system was found to be inefficient when aryl chlorides (2f) were used as
coupling partners. Use of copper catalyst up to 20 mol%, did not give satisfactory yield even
after prolong heating at elevated temperature. However, by changing the ligand (6, 25 mol%),
compound 5a (Scheme 2) was formed in moderate yield (42%). Use of the ligand (>25 mol%) or
the catalyst (>10 mol%) did not improve the yield.
O
P(Cy)
O
2
N
Pri-O
O-iPr
Ph
Ph
N
H
N
Cu-catalysis (10 mol%)
PTS, Et3N
Cl
iPr
Ligand 6 (25mol%)
H
N
H
80 oC, 2h
5a
4a
2f
Scheme 2. Synthesis of indolyl-dihydro-isoindolinones with aryl chlorides
A mechanism for the synthesis of indolylisoindolinones was assumed that copper-mediated
domino Sonogashira coupling-5-exo-dig cyclization of aryl iodides with phenylethyne may have
first generated corresponding isoindolinones which was followed by nucleophilic attack by
indoles in presence of copper(I), acting as Lewis acid in the second step.
In conclusion, we have demonstrated an efficient, economical and environmentally benign
process for the synthesis of indolyl-dihydro-isoindolinones,15-16 in aqueous miceller medium
under aerobic condition. We also established that, 2,2'-(1E,1'E)-(1R,2R)-cyclohexane-1,2-
diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)diphenol was a useful ligand for this
protocol. This novel catalytic system is cheap, tolerant, versatile and significantly less expensive
than other heavy metal catalyzed reactions.

Acknowledgment
The authors express their gratitude to the Director, IICB for laboratory facilities, the Council of
Scientific and Industrial Research (CSIR) for providing the funding and fellowships to S.S and
R.P.
Supplementary data
Supplementary data (1H and 13C NMR spectra of all new compounds) associated with this article
can be found in the online version, at doi…..
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15. General reaction procedure for the synthesis of 3-Benzyl-3-(indol-3-yl)-2-phenylisoindolin-
1-one (5a-5i): In a open round-bottomed flask filled with 25 mL of PTS aqueous solution
(15 wt%), benzamides (2a-e, 1.0 equiv.), phenyl acetylene (3, 1.5 equiv.), indoles (4a-f, 1.5
equiv.), CuI (10 mol%), ligand 1g (25 mol%), Et3N (2.0 equiv.) was added stirred
vigorously under sonication for 2 h at 80 °C. When TLC indicated completion of the
reaction, the mixture was extracted with ethyl acetate (3 x 30 mL) and the organic layer was
washed thoroughly with water. Column chromatography produced pure product (5a-i).
1
16. Spectral data of 3-Benzyl-3-(5-nitro-1-H-indol-3-yl)-2-phenylisoindolin-1-one (5c): H
NMR (CDCl3, 300 MHz):  3.82 (d, J = 13.5 Hz, 1H; -CH2Ph), 3.94 (d, J = 13.5 Hz, 1H; -
CH2Ph), 6.55 (d, J = 7.8 Hz, 2H), 6.99 (t, J = 7.2 Hz, 3H), 7.07-7.09 (m, 4H), 7.14-7.23 (m,
2H), 7.39 (d, J = 9.0 Hz, 1H), 7.50-7.53 (m, 2H), 7.55-7.60 (m, 2H), 7.91-7.94 (m, 1H),
13
8.01-8.05 (m, 1H), 8.84 (brs, 1H); C NMR (CD3OD, 75 MHz): 42.91, 71.95, 113.41,
117.41, 118.78, 119.63, 124.82, 125.00, 127.22, 127.98, 128.33, 128.88, 129.44, 129.86,
130.36, 131.94, 132.94, 134.36, 135.62, 138.35, 142.98, 150.69, 170.67; HRMS (ESI): m/z
calcd for C29H21O3N3 [M+H]+ 460.1661; found: 460.1667.