A facile one-pot transformation of baylis-hillman adducts into unsymmetrical disubstituted maleimide and maleic anhydride frameworks: A facile synthesis of himanimide A

Article abstract of DOI:10.1002/chem.200902887

Unsymmetrical, disubstituted maleimide and maleic anhydride frameworks have been accessed from Baylis-Hillman adducts in an operationally simple three-step (FriedelCrafts reaction, selective hydrolysis and cyclization), one-pot strategy. This strategy has been successfully extended to the synthesis of a representative bioactive compound, himanimide A (see scheme). (Chemical Equation Representation).

Full text of DOI:10.1002/chem.200902887

COMMUNICATION
DOI: 10.1002/chem.200902887
A Facile One-Pot Transformation of Baylis–Hillman Adducts into
Unsymmetrical Disubstituted Maleimide and Maleic Anhydride Frameworks:
A Facile Synthesis of Himanimide A
Deevi Basavaiah,* Badugu Devendar, Kunche Aravindu, and Ainelly Veerendhar[a]
The development of efficient and convenient methodolo-
gies for the synthesis of 3,4-disubstituted maleimide and
maleic anhydride derivatives has been, and continues to be,
an attractive and challenging endeavor in organic and me-
dicinal chemistry.[1,2] The importance of these targets is dem-
onstrated by the presence of such frameworks in a number
of bioactive natural products, such as himanimides A–D,[1g,i]
polycitrins A and B,[1m] arcyriarubin-B,[1o,p] aspergillus
acids A–D,[2a] lindenanolide E,[2f] chaetomellic acids A and
B,[2g] tyromycin A,[2h] and tautomycetin.[2i] Furthermore, de-
rivatives of 3,4-disubstituted maleimide and maleic anhy-
dride have also been known to exhibit various biological ac-
tivities, such as cytotoxicity,[1c] inhibition of cell death,[1d] in-
hibitors of CaMKIId (calmodulin-dependant protein kina-
se),[1a] angiogenesis,[1h] and vascular endothelial cell prolifer-
ation.[1j] In continuation of our ongoing research program in
heterocyclic compounds,[3] we herein report a facile and con-
venient methodology for the synthesis of 3,4-disubstituted
maleimide and maleic anhydride derivatives starting from
the corresponding Baylis–Hillman (B–H) adducts (derived
through the coupling of a-keto esters with acrylonitrile/
methyl acrylate) in an operationally simple one-pot strategy.
This one-pot procedure involves three reactions, that is,
Friedel–Crafts reaction, selective hydrolysis, and cyclization,
and employs methanesulfonic acid as an efficient reagent to
perform all three steps. This strategy has been successfully
extended to the synthesis of himanimide A, an important
bioactive molecule.
classes of densely functionalized molecules.[4,5] Due to the
proximity of functional groups in the products, the B–H ad-
ducts have also become attractive substrates in a number of
reactions, such as Friedel–Crafts, Diels–Alder, Heck, John-
son–Claisen rearrangement, isomerization, and hydrogena-
tion reactions.[4] Although the B–H (secondary) alcohols, de-
rived from aldehydes, have been employed as valuable sub-
strates for the Friedel–Crafts reaction,[6] to the best of our
knowledge the B–H (tertiary) alcohols derived from a-keto
esters have not been properly investigated as substrates in
the Friedel–Crafts reaction.
Therefore, it occurred to us that the B–H adducts, derived
from a-keto esters as electrophiles (and acrylonitrile/methyl
acrylate as activated alkenes), could, in principle, serve as
potential substrates for a Friedel–Crafts reaction with ben-
zene to provide phenylated products, that is, tetrasubstituted
alkenes A (Scheme 1), containing ester and cyano groups
(in the case of adducts derived from acrylonitrile) and B,
containing two ester groups (in the case of adducts derived
from methyl acrylate), for the retrosynthetic strategy, see
Scheme 1.
Upon selective hydrolysis and cyclization, these tetrasub-
stituted alkenes, A and B, would, respectively, provide di-
AHCTUNGTREGsNNUN ubstituted maleimide and maleic anhydride derivatives. It
In the last twenty years, the B–H reaction has grown ex-
ponentially and, in fact, has become a very popular carbon–
carbon bond-forming reaction because it provides valuable
[a] Prof. D. Basavaiah, B. Devendar, K. Aravindu, A. Veerendhar
School of Chemistry, University of Hyderabad
Hyderabad-500 046 (India)
Fax : (+91)40-23012460
E-mail: dbsc@uohyd.ernet.in
Scheme 1. Retrosynthetic strategy for the synthesis of 3,4-disubstituted
maleimide and maleic anhydride frameworks. EWG=electron-withdraw-
ing group.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200902887.
Chem. Eur. J. 2010, 16, 2031 – 2035
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2031

also occurred to us that it would be useful if all three steps
could be performed in one pot and by a single reagent.
Accordingly, we first selected the B–H adduct 3-ethoxy-
carbonyl-3-hydroxy-3-phenyl-2-methylenepropanenitrile
(1a),[7] obtained by the reaction of ethyl benzoylformate
with acrylonitrile, as a substrate for treatment with benzene
under the influence of various acids (Table 1). The best re-
steps (i.e., Friedel–Crafts reaction, selective hydrolysis, and
cyclization) in one pot.
Encouraged by this promising result, we transformed rep-
resentative B–H alcohols (1b–j), obtained from aromatic a-
keto esters and acrylonitrile, into the desired 3,4-disubstitut-
ed maleimides (2b–j) in 54–76% yield by treatment with
benzene in the presence of CH3SO3H at reflux for 4 h
(Table 2, entries 2–10). We also obtained single crystals for
compounds 2a and 2e and further confirmed the structures
by single-crystal X-ray data (Figure 1).[10]
With a view to understand the generality of this method-
ology, we employed the B–H alcohols (1k–m), obtained by
the coupling of aliphatic a-keto esters and acrylonitrile, as
substrates, which provided the desired 3,4-disubstituted mal-
eimides (2k–m) in 58–66% yield (Table 2, entries 11–13).
We obtained a single crystal for 2k and further established
its structure by single-crystal X-ray data (Figure 2).[10]
We successfully extended this strategy to the synthesis of
himanimide A (3),[11] an important biologically active mole-
cule, in 11.28% overall (unoptimized) yield in three steps
starting from the a-keto ester 4 (Scheme 2).[12] Although the
Table 1. Optimization of reaction conditions: reaction of B–H alcohol
(1a, 1 mmol) with benzene (6 mL) under the influence of acid (3 mmol)
at reflux.
Entry
Acid
t [h]
Yield[a] [%]
1
2
3
4
5
6
concd H2SO4
CF3CO2H (TFA)
p-TsOH
CH3SO3H
CF3SO3H
TiCl4
4
4
4
4
4
4
32
–
62
79
58
–
[a] Yield of the isolated product.
sults were obtained when 1a was treated with benzene in
the presence of methanesulfonic acid at reflux for 4 h, thus,
providing the desired 3-benzyl-4-phenyl-1H-pyrrole-2,5-
dione (2a) in 79% yield after purification by column chro-
matography (Table 1, entry 4). We were pleased to note that
methanesulfonic acid had successfully performed all three
Table 2. Synthesis of 3,4-disubstituted maleimides.[a]
Entry
B–H alcohol
R
Product[b]
Yield [%][c]
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1 f
1g
1h
1i
C6H5
2a[d]
2b
2c
2d
2e[d]
2 f
2g
2h
2i
79
65
57
76
55
70
63
54
65
61
66
62
58
2-MeC6H4
2-MeOC6H4
3-MeC6H4
3-MeOC6H4
4-MeC6H4
4-MeOC6H4
4-EtOC6H4
4-BrC6H4
4-ClC6H4
methyl
9
10
11
12
13
1j
1k
1l
2j
2k[d]
2l
ethyl
n-propyl
1m
2m
[a] All of the reactions were carried out on a 1 mmol scale of the B–H al-
cohols (1a–m) with methanesulfonic acid (3 mmol) in benzene (6 mL) at
reflux for 4 h.[7–9] [b] All of the compounds (2a–m)[8] were fully character-
ized (see the Supporting Information). [c] Yields of the isolated pure
products based on the B–H alcohols.[9] [d] Structures of these molecules
were also established from the single-crystal X-ray data (see the Support-
ing Information).[10]
Figure 1. ORTEP diagrams of compounds 2a and 2e. Ellipsoids at 50%
probability.
2032
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2031 – 2035

One-Pot Transformation of Baylis–Hillman Adducts
COMMUNICATION
(Scheme 3). However, when toluene was used for the Frie-
del–Crafts reaction with 1a, we obtained the corresponding
maleimide derivative as a mixture of ortho and para prod-
ucts in 51% yield.
Scheme 3. Synthesis of 3,4-disubstituted maleimide derivatives by the re-
action of 1a with 1,4-dimethoxybenzene.
After developing a simple one-pot methodology for the
synthesis of unsymmetrical 3,4-disubstituted maleimide de-
rivatives, we directed our attention towards the synthesis of
3,4-disubstituted maleic anhydride derivatives, 7a–e.[8] We
first selected methyl 3-ethoxycarbonyl-3-hydroxy-3-phenyl-
2-methylenepropanoate (6a), the B–H alcohol obtained by
the coupling of ethyl benzoylformate with methyl acrylate,
as a substrate. The best results were obtained when 6a was
treated with benzene in the presence of methanesulfonic
acid at reflux for 4 h, providing the required 3-benzyl-4-phe-
nylmaleic anhydride (7a) in 52% yield. Notably, compound
7a is a natural product isolated from Aspergillus nidulans.[2l]
To understand the generality of this reaction strategy, we
subjected four more B–H alcohols, 6b–e, to the reaction
conditions to provide 3,4-disubstituted maleic anhydride de-
rivatives (7b–e) in 40–56% yield (Table 3).[13] Although the
Figure 2. ORTEP diagrams of compounds 2k and 7a. Ellipsoids at 50%
probability.
Table 3. Synthesis of 3,4-disubstituted maleic anhydrides.[a]
Entry
B–H alcohol
R
Product[b]
Yield [%][c]
1
2
3
4
5
6a
6b
6c
6d
6e
C6H5
7a[d]
7b
52
45
40
56
49
4-MeC6H4
4-MeOC6H4
4-BrC6H4
4-ClC6H4
7c[15]
7d
7e
[a] All of the reactions were carried out on a 1 mmol scale of the B–H al-
cohols (6a–e) with methanesulfonic acid (3 mmol) in benzene (6 mL) at
reflux for 4 h.[7–9] [b] All of the compounds (7a–e) were obtained as col-
orless solids and fully characterized (see the Supporting Information).
[c] Yields of the isolated pure products based on the B–H alcohols.[13]
[d] The structure of this molecule was also established from single-crystal
X-ray data (see the Supporting Information).[10,14]
Scheme 2. Simple route for the synthesis of 3.[11] DABCO=1,4-
diazabicycloACHTUNGTRENNUNG[2.2.2]octane, TBDMS=tert-butyldimethylsilyl.
yields are inferior when compared to the corresponding
yields are not high, this synthesis demonstrates the potential
of the maleimide strategy in the synthesis of bioactive mole-
cules.
We also used 1,4-dimethoxybenzene for a Friedel–Crafts
reaction with 1a in the place of benzene and obtained the
corresponding maleimide derivative (2o) in 60% yield
maleACHTNGUTERNNUiG mides, this reaction is still interesting in the sense that
this methodology offers a simple procedure for the synthesis
of 3,4-disubsitituted maleic anhydride derivatives, yet anoth-
er important structural motif. We obtained a single crystal
for 7a and further established its structure by single-crystal
X-ray data (for the ORTEP diagram, see Figure 2).[10]
Chem. Eur. J. 2010, 16, 2031 – 2035
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2033

D. Basavaiah et al.
A plausible mechanism for the formation of the male-
Experimental Section
ACHTUNGTRENNUNG
General experimental procedure: Methanesulfonic acid (3 mmol, 0.288 g,
0.2 mL) was added to a stirred solution of 3-ethoxycarbonyl-3-hydroxy-3-
phenyl-2-methylenepropanenitrile (1 mmol, 0.231 g) in benzene (6 mL)
at RT and heated at reflux for 4 h.
Then the reaction mixture was allowed
to cool to RT and diluted with water
(10 mL). Aqueous NaHCO3 solution
was added slowly to neutralize the
acid and then it was extracted with di-
ethyl ether (3ꢁ15 mL). The combined
organic layers were dried over anhy-
drous Na2SO4. The solvent was evapo-
rated and the residue, thus obtained,
was purified by column chromatogra-
phy (silica gel, 5% EtOAc in hexanes)
to furnish the compound 2a as a color-
less solid (0.208 g, 79%).
All the experimental details, spectral
data, 1H and 13C NMR spectra for all
the compounds are available in the
Supporting Information.
Acknowledgements
We thank the DST (New Delhi) for
funding this project. B.D. K.A. & A.V.
thank the CSIR (New Delhi) for their
fellowships. We thank the UGC (New
Delhi) for support and for providing
some instrumental facilities. We thank
the National Single-Crystal X-ray fa-
cility funded by the DST. We also
thank Professor S. Pal, School of
Scheme 4. A plausible mechanism for the formation of 3,4-disubstituted maleimides and maleic anhydride
frameworks.
Chemistry, University of Hyderabad,
for helpful discussions regarding X-ray
data analysis.
Keywords: Friedel–Crafts reaction
himanimide A · natural products · synthetic methods
·
heterocycles
·
(acid) generated in situ should have predominantly Z ste-
reochemistry (Scheme 4, paths I & II). Whatever the course
of the reaction may be, the products isolated clearly indicate
that the transient intermediate before the cyclization step
had Z stereochemistry. In the case of 3,4-disubstituted
maleic anhydrides, we noticed that substantial amounts (15–
25%) of starting material remain intact, as evidenced by
TLC analysis of the reaction mixture (Scheme 4).[9,13] Hence,
the resulting products were obtained in low yields. However,
the results are still encouraging because the important 3,4-
disubstituted maleic anhydride derivatives are synthesized in
a one-pot operation from the B–H adducts in reasonably
good yields. Studies are underway to understand the stereo-
chemical course of the reaction.
In conclusion, we have developed a convenient, opera-
tionally simple, one-pot procedure for the synthesis of un-
symmetrical 3,4-disubstituted maleimide and maleic anhy-
dride derivatives from B–H alcohols derived from a-keto
esters (as electrophiles). This strategy has been successfully
employed to the synthesis of 3, an important bioactive mole-
cule.
[1] a) D. E. Levy, D.-X. Wang, Q. Lu, Z. Chen, J. Perumattam, Y.-j. Xu,
A. Liclican, J. Higaki, H. Dong, M. Laney, B. Mavunkel, S. Dugar,
Bioorg. Med. Chem. Lett. 2008, 18, 2390–2394; b) Y. Li, H. Zou, J.
Gong, J. Xiang, T. Luo, J. Quan, G. Wang, Z. Yang, Org. Lett. 2007,
9, 4057–4060; c) G.-Q. Xu, P. Guo, C. Zhang, Q.-J. He, B. Yang, Y.-
Z. Hu, Chem. Pharm. Bull. 2007, 55, 1302–1307; d) M. Katoh, K.
Dodo, M. Fujita, M. Sodeoka, Bioorg. Med. Chem. Lett. 2005, 15,
3109–3113; e) S. Roy, S. Roy, G. W. Gribble, Org. Lett. 2006, 8,
4975–4977; f) A. Alizadeh, F. Movahedi, A. A. Esmaili, Tetrahedron
Lett. 2006, 47, 4469–4471; g) P. Selles, Org. Lett. 2005, 7, 605–608;
h) C. Peifer, T. Stoiber, E. Unger, F. Totzke, C. Schachtele, D.
Marme, R. Brenk, G. Klebe, D. Schollmeyer, G. Dannhardt, J. Med.
Chem. 2006, 49, 1271–1281; i) P. Aqueveque, T. Anke, O. Sterner, Z.
Naturforsch. 2002, 57c, 257–262; j) M. F. Brana, L. Anorbe, G. Tar-
rason, F. Mitjans, J. Piulats, Bioorg. Med. Chem. Lett. 2001, 11,
2701–2703; k) A. Rudi, T. Evan, M. Aknin, Y. Kashman, J. Nat.
Prod. 2000, 63, 832–833; l) M. M. Faul, L. L. Winneroski, C. A.
Krumrich, Tetrahedron Lett. 1999, 40, 1109–1112; m) A. Rudi, I.
Goldberg, Z. Stein, F. Frolow, Y. Benayahu, M. Schleyer, Y. Kash-
man, J. Org. Chem. 1994, 59, 999–1003; n) P. D. Davis, R. A. Bit,
Tetrahedron Lett. 1990, 31, 5201–5204; o) M. Brenner, H. Rexhau-
2034
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2031 – 2035

One-Pot Transformation of Baylis–Hillman Adducts
COMMUNICATION
sen, B. Steffan, W. Steglich, Tetrahedron 1988, 44, 2887–2892; p) W.
Steglich, B. Steffan, L. Kopanski, G. Eckhardt, Angew. Chem. 1980,
92, 463–464; Angew. Chem. Int. Ed. Engl. 1980, 19, 459–460.
Chem. Soc. 2006, 128, 4174–4175; m) M. M. Vasbinder, J. E. Imbri-
glio, S. J. Miller, Tetrahedron 2006, 62, 11450–11459; n) F. Coelho,
G. Diaz, C. A. M. Abella, W. P. Almeida, Synlett 2006, 435–439;
o) L. Navarre, S. Darses, J.-P. Genet, Adv. Synth. Catal. 2006, 348,
317–322; p) T. Kataoka, H. Kinoshita, Eur. J. Org. Chem. 2005, 45–
58; q) T. Turki, J. Villieras, H. Amri, Tetrahedron Lett. 2005, 46,
3071–3072; r) S. Luo, X. Mi, H. Xu, P. G. Wang, J.-P. Cheng, J. Org.
Chem. 2004, 69, 8413–8422; s) L Navarre, S. Darses, J-P. Genet
Chem. Commun. 2004, 1108–1109; t) K.-S. Yang, W.-D. Lee, J.-F.
Pan, K. Chen, J. Org. Chem. 2003, 68, 915–919; u) W. Pei, H.-X.
Wei, G. Li, Chem. Commun. 2002, 1856–1857; v) D. Basavaiah, K.
Muthukumaran, B. Sreenivasulu, Synthesis 2000, 545–548; w) D. Ba-
savaiah, R. S. Hyma, K. Padmaja, M. Krishnamacharyulu, Tetrahe-
dron 1999, 55, 6971–6976; x) D. Basavaiah, V. V. L. Gowriswari,
P. K. S. Sarma, P. D. Rao, Tetrahedron Lett. 1990, 31, 1621–1624.
[6] For leading references on Friedel–Crafts reactions with B–H ad-
ducts/derivatives, see: a) C. G. Lee, K. Y. Lee, S. Lee, J. N. Kim, Tet-
rahedron 2005, 61, 1493–1499; b) S. G. Shankar, K. Y. Lee, C. G.
Lee, J. N. Kim, Tetrahedron Lett. 2004, 45, 6141–6146; c) D. Basa-
vaiah, R. Mallikarjuna Reddy, Tetrahedron Lett. 2001, 42, 3025–
3027; d) D. Basavaiah, M. Bakthadoss, G. Jayapal Reddy, Synthesis
2001, 919–923; e) H. J. Lee, M. R. Seong, J. N. Kim, Tetrahedron
Lett. 1998, 39, 6223–6226; f) D. Basavaiah, M. Krishnamacharyulu,
R. S. Hyma, S. Pandiaraju, Tetrahedron Lett. 1997, 38, 2141–2144;
g) D. Basavaiah, S. Pandiaraju, K. Padmaja, Synlett 1996, 393–395.
[7] The B–H alcohols 1a–m, 5, and 6a–e were prepared following the
known procedure, see: D. Basavaiah, T. K. Bharathi, V. V. L. Gow-
riswari, Tetrahedron Lett. 1987, 28, 4351–4352.
[2] a) S. Easwar, N. P. Argade, Synthesis 2006, 831–838; b) N. Kishore-
babu, M. Periasamy, Tetrahedron Lett. 2006, 47, 2107–2109; c) M.
Denancꢂ, E. Banaszak, M. Samadi, Tetrahedron Lett. 2006, 47,
7409–7411; d) A. C. B. Burtoloso, A. L. L. Garcia, K. C. Miranda,
C. R. D. Correia, Synlett 2006, 3145–3149; e) A. Kar, N. P. Argade,
Tetrahedron 2003, 59, 2991–2998; f) C.-F. Zhang, N. Nakamura, S.
Tewtrakul, M. Hattori, Q.-S. Sun, Z.-T. Wang, T. Fujiwara, Chem.
Pharm. Bull. 2002, 50, 1195–1200; g) S. B. Singh, D. L. Zink, J. M.
Liesch, M. A. Goetz, R. G. Jenkins, M. N. Omstead, K. C. Silverman,
G. F. Bills, R. T. Mosley, J. B. Gibbs, G. A. Schonberg, R. B. Ling-
ham, Tetrahedron 1993, 49, 5917–5926; h) W. Weber, M. Semar, T.
Anke, M. Bross, W. Steglich, Planta Med. 1992, 58, 56–59; i) X.-C.
Cheng, M. Ubukata, K. Isono, J. Antibiot. 1990, 43, 890–896; j) P. D.
Davis, R. A. Bit, S. A. Hurst, Tetrahedron Lett. 1990, 31, 2353–2356;
k) E. K. Fields, S. J. Behrend, J. Org. Chem. 1990, 55, 5165–5170;
l) T. Hamasaki, H. Nakajima, T. Yokota, Y. Kimura, Agric. Biol.
Chem. 1983, 47, 891–892; m) G. Assante, L. Camarda, L. Merlini,
G. Nasini, Gazz. Chim. Ital. 1979, 109, 151–153.
[3] a) D. Basavaiah, B. Devendar, D. V. Lenin, T. Satyanarayana, Synlett
2009, 411–416; b) D. Basavaiah, D. V. Lenin, B. Devendar, Tetrahe-
dron Lett. 2009, 50, 3538–3542; c) D. Basavaiah, S. Roy, Org. Lett.
2008, 10, 1819–1822; d) D. Basavaiah, R. J. Reddy, Org. Biomol.
Chem. 2008, 6, 1034–1039; e) D. Basavaiah, K. Aravindu, Org. Lett.
2007, 9, 2453–2456; f) D. Basavaiah, K. R. Reddy, Org. Lett. 2007, 9,
57–60; g) D. Basavaiah, R. J. Reddy, J. S. Rao, Tetrahedron Lett.
2006, 47, 73–77; h) D. Basavaiah, J. S. Rao, R. J. Reddy, A. J. Rao,
Chem. Commun. 2005, 2621–2623; i) D. Basavaiah, J. S. Rao, R. J.
Reddy, J. Org. Chem. 2004, 69, 7379–7382; j) D. Basavaiah, T. Sa-
tyanarayana, Chem. Commun. 2004, 32–33; k) D. Basavaiah, D. S.
Sharada, A. Veerendhar, Tetrahedron Lett. 2004, 45, 3081–3083;
l) D. Basavaiah, N. Kumaragurubaran, D. S. Sharada, R. M. Reddy,
Tetrahedron 2001, 57, 8167–8172; m) D. Basavaiah, B. Sreenivasulu,
J. S. Rao, Tetrahedron Lett. 2001, 42, 1147–1149; n) D. Basavaiah, T.
Satyanarayana, Org. Lett. 2001, 3, 3619–3622.
[8] These derivatives are named as 3,4-disubstituted maleimide and
maleic anhydride derivatives according to the following numbering:
[9] We cannot completely rule out the formation of minor amounts of
fumaric acid derivatives in these reactions, since the yields of male-
[4] For leading reviews on the B–H reaction, see: a) V. Declerck, J.
Martinez, F. Lamaty, Chem. Rev. 2009, 109, 1–48; b) V. Singh, S.
Batra, Tetrahedron 2008, 64, 4511–4574; c) D. Basavaiah, K. V. Rao,
R. J. Reddy, Chem. Soc. Rev. 2007, 36, 1581–1588; d) G. Masson, C.
Housseman, J. Zhu, Angew. Chem. 2007, 119, 4698–4712; Angew.
Chem. Int. Ed. 2007, 46, 4614–4628; e) Y-L Shi, M. Shi, Eur. J. Org.
Chem. 2007, 2905–2916; f) D. Basavaiah, A. J. Rao, T. Satyanaraya-
na, Chem. Rev. 2003, 103, 811–891; g) E. Ciganek in Organic Reac-
tions, Vol. 51 (Ed.: L. A. Paquette), Wiley, New York, 1997,
pp. 201–350; h) D. Basavaiah, P. D. Rao, R. S. Hyma, Tetrahedron
1996, 52, 8001–8062; i) S. E. Drewes, G. H. P. Roos, Tetrahedron
1988, 44, 4653–4670.
[5] a) M. Bakthadoss, G. Sivakumar, D. Kannan, Org. Lett. 2009, 11,
4466–4469; b) A. Trofimov, V. Gevorgyan, Org. Lett. 2009, 11, 253–
255; c) X.-Y. Guan, Y. Wei, M. Shi, J. Org. Chem. 2009, 74, 6343–
6346; d) M. Shi, X.-G. Liu, Org. Lett. 2008, 10, 1043–1046; e) Y.
Zhang, Y.-K. Liu, T.-R. Kang, Z.-K. Hu, Y.-C. Chen, J. Am. Chem.
Soc. 2008, 130, 2456–2457; f) P. Shanmugam, V. Vaithiyanathan, K.
Selvakumar, Tetrahedron Lett. 2008, 49, 2119–2123; g) Z. Shafiq, L.
Liu, Z. Liu, D. Wang, Y.-J. Chen, Org. Lett. 2007, 9, 2525–2528;
h) F. C. Pigge, R. Dhanya, E. R. Hoefgen, Angew. Chem. 2007, 119,
2945–2948; Angew. Chem. Int. Ed. 2007, 46, 2887–2890; i) E. L.
Myers, C. P. Butts, V. K. Aggarwal, Chem. Commun. 2006, 4434–
4436; j) J. S. Rao, J.-F. Briere, P. Metzner, D. Basavaiah, Tetrahedron
Lett. 2006, 47, 3553–3556; k) M. Dadwal, R. Mohan, D. Panda,
S. M. Mobin, I. N. N. Namboothiri, Chem. Commun. 2006, 338–340;
l) M. E. Krafft, T. F. N. Haxell, K. A. Seibert, K. A. Abboud, J. Am.
AHCTUNGERTGiNNUN mide are not quantitative and also the yields of maleic anhydride
derivatives are low.
[10] Detailed X-ray crystallographic data for compounds 2a (CCDC-
687372), 2e (CCDC-687373), 2k (CCDC-687374), 7a (CCDC-
687375) can be obtained free of charge from The Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[11] Himanimide A is known in the literature; 1H and 13C NMR spectral
data are reported. Our data is in agreement with that of the litera-
ture data.[1i] This compound was isolated as a liquid.[1i] We obtained
this compound 3 as a solid (m.p. 108–1108C decomp).
[12] During the course of the Friedel–Crafts reaction, the t-butyldime-
thylsilyl protecting group was cleaved to provide the corresponding
phenol derivative (2n).
[13] We also noticed that longer reaction times gave a mixture of prod-
ucts as evidenced by TLC examination.
[14] This compound is known in the literature (it was isolated from As-
pergillus nidulans and its melting point, 1H and 13C NMR spectral
data are reported. Our data is in agreement with that of the litera-
ture data).[2l]
[15] This compound is known in the literature, the synthesis (by a non-
B–H route), 1H and 13C NMR spectral data of which are reported.
Our spectral data is in agreement with that of the literature data.[1g]
Received: October 19, 2009
Published online: January 20, 2010
Chem. Eur. J. 2010, 16, 2031 – 2035
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2035