One-pot synthesis of acenaphtho[1,2-b]furan derivatives

Article abstract of DOI:10.1016/j.cclet.2011.11.004

New 9-(alkyl or aryl)acenaphtho[1,2-b]furan-8-(alky or aryl)amine compounds has herein been reported by one-pot reaction of (acenaphthylen-1-yloxy) trimethylsilane, alkyl and aryl aldehydes, and aryl and alky isocyanides in refluxing DMF.

Full text of DOI:10.1016/j.cclet.2011.11.004

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 169–172
www.elsevier.com/locate/cclet
One-pot synthesis of acenaphtho[1,2-b]furan derivatives
b,
c
Mohammad Taghi Goldani a, , Reza Sandaroos , Saman Damavandi
*
*
a Department of Chemical Engineering, Islamic Azad University, Birjand Branch, Birjand, Iran
b Department of Chemistry, Faculty of Science, Birjand University, Birjand, Iran
c Department of Chemistry, Sarvestan Branch, Islamic Azad University, Sarvestan, Iran
Received 22 August 2011
Available online 23 December 2011
Abstract
New 9-(alkyl or aryl)acenaphtho[1,2-b]furan-8-(alky or aryl)amine compounds has herein been reported by one-pot reaction of
(acenaphthylen-1-yloxy)trimethylsilane, alkyl and aryl aldehydes, and aryl and alky isocyanides in refluxing DMF.
# 2011 Published by Elsevier B.V. on behalf of Chinese Chemical Society.
Keywords: One-pot reaction; Acenaphtho[1,2-b]furan-8-amine; Isocyanides
Modern industry prefers synthetic approaches with minimum steps along with maximum complexity of
product [1]. A multi-component reaction (MCRs), which makes possible combinatorial reactions between simple
starting materials and producing target product in one-pot operation, is one of the best approaches to fulfill this
aim. MCRs have been associated with advantages, such as simplified purification due to incorporation of all
starting material into the final product, not producing by product, minimizing reaction steps and producing
structurally divers products from starting materials, which all of them are pronounced advantages over traditional
synthetic approaches [2–7].
Designing synthetic plans for Fused furan heteroaromatic compounds [8,9], which abundantly occur in nature,
have recently gained considerable attention because of their pharmacologically and biologically activities and also
because of their applications as efficient intermediate in preparation of other natural products [10,11]. Although
various synthetic approach have ever been introduced for fused furans, isocyanide based MCRs emerged 1990s by
Passerini [12] have predominated because of simplified performance, easy purification and capability of producing
structurally divers furans in one-pot operation [13–19]. To the best our knowledge, there are no published reports
which are devoted to the synthesis of acenaphtho[1,2-b]furan derivatives. With these considerations in mind,
we designed a one-pot synthesis for the preparation of the 9-substituted acenaphtho[1,2-b]furan-8-amine derivatives
7a–r starting from (acenaphthylen-1-yloxy)trimethylsilane, alkyl and aryl aldehydes and aryl (or alkyl) isocyanides
(Table 1).
* Corresponding authors.
E-mail addresses: mt.goldani@yahoo.com (M.T. Goldani), R_Sandaroos@yahoo.com (R. Sandaroos).
1001-8417/$ – see front matter # 2011 Published by Elsevier B.V. on behalf of Chinese Chemical Society.
doi:10.1016/j.cclet.2011.11.004

170
M.T. Goldani et al. / Chinese Chemical Letters 23 (2012) 169–172
Table 1
One-pot three-component synthesis of compounds 7a–r. .
R
NH
TMS
O
R'
O
O
refluxing DMF
18h
+
C
N R
+
R'
H
(2)
(7a-r)
Entry
1
R
R0
Product
Yield (%)a
82
Entry
R
R0
Product
Yield (%)a
72
En
En
7a
10
7j
Q
Q
2
3
4
5
6
7b
7c
7d
7e
7f
86
79
84
81
88
11
12
13
14
15
7k
7l
87
84
82
93
74
PQ4
Dt
Q
En
Q
Q
7m
7n
7o
Dt
En
U
Q
H
Q
Q
7
8
7g
7h
83
75
16
17
7p
7q
70
75
NO2
Q
Q
9
Propyl
7i
82
18
7r
73
Q
Q
Q
a
Refers to purified yield.
1. Results and discussions
Teimouri and Mansouri in 2008s [20] reported catalyst-free synthesis of phenaleno[1,2-b]furan derivatives starting
from aryl and alky aldehydes, alkyl and aryl isocyanides, and 2H-phenalene-1,3-dione in one-pot operation.
Knoevenagel intermediate resulting from condensation of isocyanide-activated 2H-phenalene-1,3-dione with
aldehyde have been established as typical intermediate in this kind of reaction. Accordingly, we envisioned to apply
the same synthetic approach into the preparation of 9-substituted acenaphtho[1,2-b]furan-8-amine using
acenaphthylen-1(2H)-one, benzaldehyde and isocyanocyclohexane as starting components (Fig. 1). Although,
experimental attempts on the preparation of these compounds were failed, and monitoring the reaction by TLC showed
that the starting substrates had remained unchanged even after 36 h as well as even at the presence of DABCO which is
a typical base in this type of reactions [11] It is presumable two hydrogens on the adjacent carbon to the carbonyl group
of acenaphthylen-1(2H)-one are not enough acidic to form corresponding enolate at the presence of relatively weak

M.T. Goldani et al. / Chinese Chemical Letters 23 (2012) 169–172
171
O
O
refluxing DMF
N
C
NR
Ph
H
36 h
DABCO
(1)
Fig. 1. Unsuccessful attempt on the preparation of aminofuran.
TMS
O
O
1) LDA
2) TMSCl
(1)
(2)
Fig. 2. Preparation of (acenaphthylen-1-yloxy)trimethylsilane (2) from acenaphthylen-1(2H)-one (1).
R
N
C
R
R
NH
N
C
N R
OTMS
C
N R
Me3SiC
N R
R'
O
R'
H
O
O
TMS
O
O
R'
O
R'
H
R'CHO
4+1
Cycloaddition
- TMSOH
(2)
(4)
(7a-r)
(6)
(3)
(5)
Fig. 3. Proposed mechanism for one-pot three-component synthesis of compounds 7a–r.
bases such as isocyanocyclohexane or DABCO. To get round the problem, we converted acenaphthylen-1(2H)-one to
the corresponding silyl enol ether (Fig. 2) which afforded desired product (7g) in 83% yield when was refluxed along
with benzaldehyde and 1-isocyanobenzene for 10 h in DMF (Table 1, entry 7).
Effect of temperature was evaluated by carrying out the reaction at the various temperatures. The chemical yields
increased as reaction temperature was raised. Hence, refluxing temperature was chose as optimum temperature and
applied for all the reactions. Various solvents such as CH2Cl2, CHCl3, ethanol, CH3CN and toluene were screened for
the reaction and DMF was found out as the best choice.
To disclose generality and scope of the reaction with respect to aldehyde, we examined various aliphatic aldehydes,
such as a,ß-unsaturated aldehydes and substituted aromatic aldehydes containing electron-withdrawing and electron-
releasing substituent groups, and it was disclosed that all of them were capable of tolerating reaction conditions with
good yields (Table 1, entries 1–12). In addition, we investigated limitations and scope of the reaction with respect to
isocyanide component. We applied aliphatic and aromatic isocyanides, and found out that the reaction efficiently
proceeded even with hindered aliphatic and aromatic isocyanides (Table 1).
We have postulated a mechanism for these reactions which is in agreement with well-known mechanisms which
have recently been reported (Fig. 3) [11,20].
The first step presumably involves nucleophilic attack of isocyanide on silyl enol ether (2), resulting in
disconnection of O-SiMe3 linkage and generation of an active enolate which is present as counter anion in ion pair
complex (3). Aldol adduct (4), which is formed from nucleophilic attack of generated enol on aldehyde, can lose a
molecule of (CH3)3SiOH to afford a,ß-unsaturated keton (5). This is probably followed by [4 + 1] cycloaddition
reaction to give iminolactone intermediate (6). Benefiting from delocalization stability, iminolactone (6) is driven to
undergo isomerization to full conjugated aminofuran heteroaromatic moiety (7).
2. Experimental
All products are new and were characterized by IR, 1HNMR, 13CNMR and elemental micro analyzing. 1HNMR
spectra were recorded on a Bruker AQSAVANCE-400 MHz spectrometer using TMS as an internal standard (CDCl3
solution). 13CNMR spectra were recorded on a Bruker AQSAVANCE-125 MHz spectrometer (CDCl3 solution). IR

172
M.T. Goldani et al. / Chinese Chemical Letters 23 (2012) 169–172
spectra were recorded from KBr disk on the FT-IR Bruker Tensor. Elemental analyses were performed using a Heraeus
CHN-O-Rapid analyzer. Thin layer chromatography (TLC) on commercial aluminum-backed plates of silica gel, 60
F254 was used to monitor the progress of reactions. (Acenaphthylen-1-yloxy)trimethylsilane (2) was prepared
according to the literature [21].
2.1. General procedure for preparation of acenaphtho[1,2-b]furan derivatives 7a–r
To a magnetically stirred mixture of aldehyde (1.0 mmol) and (acenaphthylen-1-yloxy)trimethylsilane (2) in DMF
(40 mL) was dropwisely added a solution of isocyanide (1.0 mmol) in DMF (10 mL) over a 15 min-period at ꢀ78 8C.
Subsequently, the reaction was slowly allowed to warm to room temperature and then refluxed for 18 h. Then, the
reaction mixture was cooled and washed with water (3 ꢁ 20 mL) and extracted with CH2Cl2 (4 ꢁ 15 mL).
Evaporation of volatile form organic layer left a solid which was washed with Et2O and stored as final product.
References
[1] B.M. Trost, Science 254 (1991) 1471.
[2] Y. Dai, B.D. Li, et al. Chin. Chem. Lett. 21 (2010) 31.
[3] Y.B. Jiang, C.X. Kuang, Chin. Chem. Lett. 20 (2009) 545.
[4] Y. Liang, L.M. Tang, et al. Chin. Chem. Lett. 21 (2010) 991.
[5] Y. Yang, H.G. Hu, et al. Chin. Chem. Lett. 20 (2009) 52.
[6] R. Sandaroo, S. Damavandi, A. Nazif, et al. Chin. Chem. Lett. 22 (2011) 213.
[7] A. Kuraitheerthakumaran, S. Pazhamalai, M. Gopalakrishnan, Chin. Chem. Lett. 22 (2011) 1199.
[8] F.M. Dean, Adv. Heterocycl. Chem. 30 (1982) 167.
[9] B.H. Lipshutz, Chem. Rev. (1986) 795.
[10] D.D. Sternbach, D.M. Rossana, Tetrahedron Lett. 23 (1982) 303.
[11] B. Baghernejad, M.M. Heravi, H.A. Oskooie, et al. Mol. Divers. 15 (2011) 245.
[12] M. Passerini, Gazz. Chim. Ital. 52 (1922) 432.
[13] V. Nair, R.S. Menon, A.U. Vinod, S. Viji, Tetrahedron Lett. 43 (2002) 2293.
[14] A. Shaabani, M.B. Teimouri, H.R. Bijanzadeh, Tetrahedron Lett. 43 (2002) 9151.
[15] A. Shaabani, M.B. Teimouri, H.R. Bijanzadeh, Monatsh. Chem. 135 (2004) 441.
[16] A. Shaabani, M.B. Teimouri, H.R. Bijanzadeh, Monatsh. Chem. 135 (2004) 589.
[17] A. Shaabani, M.B. Teimouri, S. Samadi, K. Soleimani, Synth. Commun. 35 (2005) 535.
[18] M.B. Teimouri, R. Bazhrang, Bioorg. Med. Chem. Lett. 16 (2006) 3697.
[19] M.B. Teimouri, H.R. Khavasi, Tetrahedron 63 (2007) 10269.
[20] M.B. Teimouri, F. Mansouri, J. Comb. Chem. 10 (2008) 507.
[21] J.J. Song, Z. Tan, J.T. Reeves, et al. Org. Lett. 10 (2008) 877.