Nucleophilic substitution reaction of Morita-Baylis-Hillman adducts of isatin with X, S, N, and O-nucleophiles: A facile and efficient synthesis of highly functionalized tetrasubstituted alkene appended oxindoles

Article abstract of DOI:10.1016/j.tetlet.2011.11.006

The Morita-Baylis-Hillman adducts derived from isatins and maleimides have undergone a facile and efficient allylic nucleophilic substitution reaction with X, S, N, and O-nucleophiles to afford functionalized tetrasubstituted alkene appended oxindoles in

Full text of DOI:10.1016/j.tetlet.2011.11.006

Tetrahedron Letters 53 (2012) 90–94
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Tetrahedron Letters
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Nucleophilic substitution reaction of Morita–Baylis–Hillman adducts
of isatin with X, S, N, and O-nucleophiles: a facile and efficient synthesis
of highly functionalized tetrasubstituted alkene appended oxindoles
Rajarethinam Solaiselvi a, Asit Baran Mandal b, Ponnusamy Shanmugam a,
⇑
a Organic Chemistry Division, Council of Scientific and Industrial Research (CSIR), Central Leather Research Institute (CLRI), Adyar, Chennai 600 020, India
b Chemical Laboratory, Council of Scientific and Industrial Research (CSIR), Central Leather Research Institute (CLRI), Adyar, Chennai 600 020, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The Morita–Baylis–Hillman adducts derived from isatins and maleimides have undergone a facile and
efficient allylic nucleophilic substitution reaction with X, S, N, and O-nucleophiles to afford functionalized
tetrasubstituted alkene appended oxindoles in very good yield. The MBH adducts and their acetates on
treatment with halides, saturated and unsaturated amines, thiols, and trialkyl orthoformates afforded
allyl halide, allyl amine, allyl thio-ether and allyl ether derivatives of oxindole, respectively.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 11 August 2011
Revised 31 October 2011
Accepted 3 November 2011
Available online 13 November 2011
Keywords:
Isatin
Isomerization
Morita–Baylis–Hillman adduct
Tetrasubstituted alkene
Nucleophiles
Oxindoles
Development of novel methods to functionalize C-3 position of
isatin is vital for the synthesis of 3-spirocarbocycle-2-oxindoles,
3-spiroheterocycle-2-oxindoles, 3-spirolactone-2-oxindoles, and
3-spirocyclicether-2-oxindoles that are elegant synthetic targets
due to their significant biological activities.1–3 The Morita–Baylis–
Hillman (MBH) adducts4 and their acetate derivatives have been
used as synthons for the preparation of diverse and multifunctional
molecules.5 Isomerization of MBH adducts with catalysts such as
H2SO4,6 TFA7 TMSOTf,8 montmorillonite K10 clay,9 and various
nucleophiles provided highly functionalized trisubstituted
alkenes.10 They have also been served as versatile building blocks
in the synthesis of natural products, heterocycles, and bio-active
molecules.11 We have exploited the MBH adduct of isatin for the
synthesis of a number of 3-spiro-oxindole derivatives.12,13 Recently,
analogues synthesis of MBH adduct of isatin with maleimide has
been reported.14 However, except a lone [3+2]-cycloaddition reac-
tion,14,13c no chemistry of this synthetically potential MBH adduct
has been explored. Hence, we were intrigued to study the nucleo-
philic substitution reaction of MBH adducts with X, S, N, and
O-nucleophiles, which in principle provide synthetically challenged,
tetrasubstituted alkene appended oxindoles and to explore their
synthetic use.
Initially, halogen as a nucleophile has been explored (Scheme
1). Thus, slurry prepared from MBH adduct of isatin 3a, SiO2, and
aq HBr was irradiated in a microwave oven for 4 min.
The reaction afforded bromo allylic substituted product 5a in a
43% yield as a major product and an unusual debrominated com-
pound 6a in a 11% yield as a minor product (Table 1, entry 1). In-
crease of irradiation time or 100% power level (PL) favored the
debrominated product 6a (Table 1, entries 2 and 3). Reactions un-
der lower PL (50%), and reduced irradiation time (2 min) afforded
only 5a; however, in low yield (Table 1, entries 4 and 5). The reac-
tion with extended irradiation time (10–15 min) with full 100% PL
provided complex material.
It should be noted that under similar reaction conditions no
debrominated products are formed from MBH adducts of isatin de-
rived from activated alkenes such as acrylonitrile and methyl acry-
late.15 Thus, it is apparent that the debrominated product 6a is
formed from the allylic substituted product 5a. A separate micro-
wave irradiation reaction of bromo derivative 5a with aq HBr/
SiO2 yielded only the eliminated product 6a in a quantitative yield
with the elimination of bromine, strengthening this observation. A
plausible mechanism for the formation of 6a from 5a is shown in
Scheme 2.
In order to increase the yield of 5a, the reaction of 3a in aceto-
nitrile with other reagent system has been carried out, where the
HBr gas has been generated in-situ (2 equiv of LiBr and 2.5 equiv
of H2SO4), for 5 h at room temperature.16 The reaction afforded
⇑
Corresponding author. Tel.: +91 44 24437129; fax: +91 44 24911589.
E-mail address: shanmu196@rediffmail.com (P. Shanmugam).
0040-4039/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2011.11.006

R. Solaiselvi et al. / Tetrahedron Letters 53 (2012) 90–94
91
R1
N
R1
N
(Table 1, entry 7). However, reaction with 2 equiv of LiBr and a cat-
alytic amount of H2SO4, 5a was obtained in a 76% yield (Table 1,
entry 8).
O
O
O
HO
O
AcO
O
O
a
b
R1
The observed moderate yield of 5a under the conditions de-
scribed above is perhaps due to the availability of free 3°-hydroxyl
groups (Table 1, entries 1–8). Hence, to improve the yield, the hy-
droxyl group has been protected as acetate and the nucleophilic
substitution reaction was studied. Thus, MBH adducts 3a and 3b
were acylated using acetyl chloride and K2CO3 to yield protected
adducts 4a and 4b, respectively, in excellent yield. Further nucleo-
philic substitution of acetates 4a and 4b under optimized condition
described above (Table 1, entry 8) furnished bromo allylic substi-
tuted products 5a and 5b in 82% and 80% yields, respectively (Table
2, entry 1).
N
+
O
O
O
N
N
O
N
3a, R1=Me
3b, R1= Ph
1
2a, R1=Me
2b, R1= Ph
4a, R1=Me
4b, R1= Ph
c-e
Table 1
R1
R1
N
R1
N
N
O
O
O
O
O
O
Cl
Br
H
H
+
+
O
O
O
N
N
N
Extending the procedure to chloride as nucleophile, reactions of
4a and 4b with 2 equiv LiCl and catalytic amount of H2SO4 in
CH3CN yielded the chloro derivatives 5c and 5d, respectively, in
excellent yield (Table 2, entry 2). However, attempts to use iodide
as nucleophile with KI and H2SO4 for adducts 3a and 4a failed to
provide desired products (Table 2, entry 3). The structure of the
new compounds was arrived from spectroscopic data analysis
(FTIR, 1H NMR, 13C NMR, DEPT-135, mass spectra, NOESY and sin-
gle crystal X-ray data.). Z-geometry has been assigned for the dou-
ble bond of compound 5c as evidenced from single crystal XRD
data17 as shown in Figure 1. Further, the structure of debrominated
product 7a was confirmed from 1H NMR spectrum as the presence
of two methylene protons at d 3.97 and a negative methylene car-
bon peak at d 35.9 seen in the DEPT-135 spectrum.
Encouraged by the preliminary results, we were interested in
studying the substitution reaction with sulfur nucleophiles
although nucleophilic substitution of MBH adduct with sulfur
nucleophile is less known (Scheme 3). Thus, acetate adduct 4a in
methanol was treated with p-thiocresol at room temperature affor-
ded the allyl thio ether derivative 7a in an 81% yield (Table 3, entry
6a, R1=Me
5c, R1=Me
5d, R1= Ph
5a, R1=Me
5b, R1= Ph
a. DABCO, CH3CN, r.t., 24 h, 80%; b. AcCl, K2CO3, DCM, r.t.,12 h, 80%; c.
aq.HBr, SiO2, mW 70% PL, 4 min.; d. LiBr, H2SO4, CH3CN, 0 oC-r.t.; e. LiCl,
H2SO4,CH3CN, 0 oC-r.t..
Scheme 1. Nucleophilic substitution reaction of MBH adducts 4a/4b with halogen
nucleophiles.
Table 1
Optimization of nucleophilic substitution reaction of 3a with bromide as
a
nucleophile
Entry Condition
Product(s)
(% Yield)
1
2
3
4
5
6
7
8
aq HBr, SiO2,
aq HBr, SiO2,
aq HBr, SiO2,
aq HBr, SiO2,
aq HBr, SiO2,
l
l
l
l
l
W, 70% PL, 4 min
W, 70% PL, 7 min
W, 100% PL, 4 min
W, 50% PL, 4 min
W, 70% PL, 2 min
5a(43), 6a(11)
5a(20), 6a(30)
5a(10), 6a(40)
5a(20)
5a(16)
2 equiv LiBr, 2.5 equiv H2SO4, CH3CN, 0 °C to rt, 5 h 5a(60)
1). Similarly, the a-toluenethiol and cyclohexanethiol with adduct
2 equiv LiBr, CH3CN, 0 °C to rt, 48 h
2 equiv LiBr, cat. H2SO4, CH3CN, 0 °C to rt, 5 h
5a(15)
5a(76)
4b also furnished corresponding thio allylic substituted products
7b and 7c in excellent yields (Table 3, entries 2 and 3). Appreciably,
no catalyst was required for this transformation. The structure of
compound 7a was established from spectroscopic data analysis.
Analysis of NOESY spectrum revealed the stereochemistry of dou-
ble bond which is similar to that of compound 5c.
Table 2
Synthesis of allyl halides 5a–d from MBH adducts 4a/b
To bring in diverse nucleophiles in the substitution reaction,
nitrogen as nucleophile18 was chosen. Therefore, the reaction of
adduct 4a in methanol with aryl amines and unsaturated aliphatic
amine such as propargyl amine has been carried out (Scheme 4).
Significantly, substitution reaction with propargyl amine afforded
highly functionalized substituted N-propargylated secondary
amine product 8a in an 82% yield via an allylic substitution fol-
lowed by 1,3-proton shift (Table 4, entry 1) and such type of allylic
proton shift is facile under basic condition.12c Similarly, aniline and
p-toluidine also acted as good nitrogen nucleophiles toward MBH
adducts 4a and 4b to yield corresponding substituted products
8c/d and 8e/f in excellent yield, respectively (Table 4, entries 2
and 3). It should be noted that here also no catalyst was required
for this transformation.
Entry Substrate Condition
Product Yield
(%)
1
2
3
4a/b
4a/b
3a/4a
2 equiv LiBr, cat. H2SO4, CH3CN, 0 °C 5a/b
to rt, 3 h
2 equiv LiCl, cat. H2SO4, CH3CN, 0 °C
to rt, 3.5 h
KI, H2SO4, CH3CN, rt, 3 h
82/80
82/81
—
5c/d
—
exclusively the bromo allylic substituted product 5a in a 60% yield
(Table 1, entry 6) with remaining charred material. To avoid
charring due to excess of acid, an experiment with LiBr alone
yielded bromo allylic substituted product 5a only in 15% yield
N
N
N
O
N
O
O
O
O
O
H
O
O
Br
Br
Br
H
H
HBr
O
O
O
-Br2
O
N
N
N
N
6a
5a
Scheme 2. Plausible mechanism for the formation of 6a.

92
R. Solaiselvi et al. / Tetrahedron Letters 53 (2012) 90–94
Figure 1. ORTEP diagram of compound 5c.17
Table 4
Synthesis of 8a–f from 4a/4b
N
O
S
O
Entry
Substrate
Reagenta
Time (min)
Product
Yield (%)
R1
N
H
Ph
N
1
2
3
4a/b
4a/b
4a/b
Propargyl amine
Aniline
p-Toluidine
20
30
30
8a/b
8c/d
8e/f
82/81
79/80
79/80
O
O
+
O
AcO
N
O
S
O
7a
a
+
Ph
H
a
RSH
All the reaction were carried out in methanol.
Table 3
O
N
O
N
O
O
N
4a, R1=Me
4b, R1= Ph
R= Ph -4-Me,
-CH2Ph, cyclohexyl
SCH2Ph
7c
The structure of 8a was confirmed using FTIR, 1H NMR, 13C
H
O
N
NMR, DEPT-135, mass spectroscopic data. The geometry of the
product was arrived from NOESY studies and single crystal X-ray
data. From the structure of the allylic substitution product, it is
evident that the product formed via a substitution followed by
1,3-proton shift and not a simple direct substitution product. The
FAB mass spectrum also supported the formation of amino substi-
tuted product 8a (See Supplementary data). Final proof of the
structure 8a and geometry has been arrived from single crystal
XRD data17 as shown in Figure 2.
a. methanol, r.t., 15-30 min. 78-81%
7b
Scheme 3. Nucleophilic substitution reaction of of 4a/4b with sulfur nucleophiles.
Table 3
Synthesis of 7a, 7b and 7c from 4a and 4b
Entry
Substrate
Reagenta
Time (min)
Product
Yield (%)
To strengthen the diversity of nucleophiles in the reaction
described above, we decided to study the reaction with oxygen
nucleophiles (Scheme 5). Thus, microwave irradiation (100% PL)
of adduct 4a with excess trimethyl orthoformate and 100% w/w
montmorillonite K10 clay9 as acid catalyst provided the methoxy
1
2
3
4a
4b
4b
p-Thiocresol
15
30
30
7a
7b
7c
81
80
78
a
-Toluenethiol
Cyclohexanethiol
a
All the reactions were carried out in methanol.
R1
N
O
O
H
R1
N
N
H
R1
N
R1
N
O
N
O
O
O
O
AcO
O
O
H
8a, R1=Me;8b, R1= Ph
H
R
N
a
R1
N
+
RNH2
H
N
H
1,3-proton
shift
+
Table 4
O
O
N
O
N
O
N
O
4a, R1=Me
4b, R1= Ph
H
R= Ph,-Ph -4-Me,
propargyl
8e, R1=Me;8f, R1= Ph
Ph
N
H
O
a. methanol, r.t., 15-30 min. 79-82%
N
8c, R1=Me;8d, R1= Ph
Scheme 4. Nucleophilic substitution reaction of 4a/4b with nitrogen nucleophiles.

R. Solaiselvi et al. / Tetrahedron Letters 53 (2012) 90–94
93
Figure 2. ORTEP diagram of compound 8a.17
0
R1
N
3-proton shift of the SN compound may be due to the higher
basicity of the alkoxy ion compared to halo and thio nucleophiles,
which triggers the 1,3-shift. Experiments with increased irradia-
tion time tend to decompose the products. Similarly, under
optimized condition, with triethyl orthoformate adducts 3a and
3b afforded 1,3-proton shift products 9b and 9c as well as ethoxy
substituted products (SN products) 10b and 10c, respectively in
good yield (Table 5, entry 2). However, to our surprise, reaction
with propargyl alcohol failed to provide expected products and
only unreacted starting material was recovered. The structure of
product 9a was confirmed by spectroscopic data. Analysis of
NOESY spectrum substantiates the formation of allylic substitution
product with 1,3-proton shift and not a direct substitution product.
To demonstrate the synthetic use and chemistry of compound
3a, reduction with NaBH4 was carried out, which afforded product
11a in a 75% yield. Further, compound 3a was treated with 4 equiv
of CAN and propargyl alcohol to afford highly functionalised NC-H
activated product 12a in a 71% yield (Scheme 6). Compounds 11a
and 12a, the potential synthons for the synthesis of oxindole based
alkaloid natural products are being explored.
R1
N
O
O
O
O
O
R1
N
H
+
O
O
O
+
O
HO
O
O
N
N
a
9a
10a
CH(OR)3
O
Table 5
N
R1
R1
N
R= -Me, -Et
N
O
O
3a, R1=Me
3b, R1= Ph
O
Et
O
H
+
Et
O
O
O
N
a. Mont. K10 clay, µW
100% PL, 16 min.
N
9b, R1=Me
9c, R1= Ph
10bR1=Me
10c, R1= Ph
Scheme 5. Nucleophilic substitution reaction of 3a/3b with oxygen nucleophiles.
allylic substitution followed by 1,3-proton shifted product 9a and
the direct methoxy substituted product 10a albeit in low combined
yield (<20%). However, the reaction with unprotected MBH adduct
3a under the condition described above afforded better yield of
both 9a and 10a in 35% and 29% yields, respectively (Table 5, entry
1). Thus, in contrast to other nucleophiles, adduct 3a is a better
substrate than 4a for the oxygen nucleophiles. Here also the 1,
In conclusion, we have demonstrated an efficient synthesis of
highly functionalized, tetrasubstituted alkene appended oxindoles
from maleimide derived MBH adducts of isatin via allylic nucleo-
philic substitution reaction with a range of diverse nucleophiles
such as X, S, N, and O in very good yield. Further studies with
Table 5
Synthesis of allyl ethers from maleimide derived MBH adducts 3a and 3b
Entry
Substrate
Condition
Products (% yield)
1,3-Shift product
Direct SN product
1
2
3
3a
3a/b
3a/4a
CH(OMe)3, mont. K10 clay,
l
Wa, 16 min
Wa, 16 min
Wa
9a (35)
9b/c (33/36)
—
10a (29)
10b/c (30/28)
—
CH(OEt)3, mont. K10 clay,
l
Propargyl alcohol, mont. K10 clay,
l
a
100% PL was used.

94
R. Solaiselvi et al. / Tetrahedron Letters 53 (2012) 90–94
3135; (g) Edmondson, S.; Danishefsky, S. J.; Sepp-Lorenzinol, L.; Rosen, N. J. Am.
N
Chem. Soc. 1999, 121, 2147; (h) Alper, P. B.; Meyers, C.; Lerchner, A.; Siegel, D.
R.; Carreira, E. M. Angew. Chem., Int. Ed. 1999, 38, 3186; (i) Onishi, T.; Sebahar, P.
R.; Williams, R. M. Tetrahedron 2004, 60, 9503.
N
N
O
O
O
O
O
O
HO
HO
HO
NaBH4
4eq. CAN
OH
4. (a) Baylis, A. B.; Hillman M. E. D. German Patent 2155113, 1972. Chem. Abstr.
1972, 77, 34174q.; (b) Morita, K.; Suzuki, Z.; Hirose, H. Bull. Chem. Soc. Jpn. 1968,
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MeOH,
0oC-r.t.,2h
75%
O
O
O
N
N
N
0oC-r.t.,4h
71%
11a
3a
O
5. (a) Basavaiah, D.; Rao, A. J.; Satyanarayana, T. Chem. Rev. 2003, 103, 811–891;
(b) Batra, S.; Singh, V. Tetrahedron 2008, 64, 4511–4574; (c) Declerck, V.;
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Reactions; Paquette, L., Ed.; Wiley: New York, 1997; p 201. Vol. 51; (e) Ma, G.-
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12a
Scheme 6. Synthetic transformation of MBH adduct 3a.
utilization of these allylic substituted products for the synthesis of
natural product cores are underway.
8. (a) Basavaiah, D.; Muthukumaran, K.; Sreenivasulu, B. Synthesis 2000, 545; (b)
Basavaiah, D.; Padmaja, K.; Satyanarayana, T. Synthesis 2000, 1662.
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10. (a) Buchholz, R.; Hoffmann, H. M. R. Helv. Chim. Acta 1991, 74, 1213; (b)
Beltaïef, I.; Hbaïeb, S.; Besbes, R.; Amri, H.; Villiéras, M.; Villiéras, J. Synthesis
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Acknowledgment
R.S. thanks the Council of Scientific and Industrial Research
(CSIR), New Delhi for the award of Junior Research Fellowship
(JRF).
Supplementary data
11. (a) Deng, J.; Hu, X.-P.; Huang, J.-D.; Yu, S.-B.; Wang, D.-Y.; Duan, Z.-C.; Zheng, Z.
J. Org. Chem. 2008, 73, 2015; (b) Bakthadoss, M.; Sivakumar, N.; Sivakumar, G.;
Murugan, G. Tetrahedron Lett. 2008, 49, 829; (c) Rajan, Y. C.; Kanakam, C. C.;
Selvam, S. P.; Murugesan, K. Tetrahedron Lett. 2007, 48, 8562; (d) Lee, K. Y.;
Gowrisankar, S.; Lee, Y. J.; Kim, J. N. Tetrahedron 2006, 62, 8798; (e) Lee, K. Y.;
Kim, S. C.; Kim, J. N. Tetrahedron Lett. 2006, 47, 977.
12. (a) Shanmugam, P.; Vaithiyanathan, V.; Viswambharan, B. Tetrahedron Lett.
2006, 47, 6851–6855; (b) Shanmugam, P.; Vaithiyanathan, V.; Selvakumar, K.
Tetrahedron Lett. 2008, 49, 2119–2123; (c) Vaithiyanathan, V.; Shanmugam, P.;
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Supplementary data (general experimental procedure, com-
plied spectroscopic data of new compounds and scanned copies
of spectra) associated with this article can be found, in the online
version, at doi:10.1016/j.tetlet.2011.11.006.
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CB21EZ,
UK
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