Iron(III) trifluoroacetate [Fe(F3CCO2)3] as an easily available, non-hygroscopic, non-corrosive, highly stable and a reusable Lewis Acid catalyst: Efficient O-silylation of α-hydroxyphosphonates, alcohols and phenols by he

Article abstract of DOI:10.1016/j.jorganchem.2008.05.018

O-Silylation of hydroxyl groups of α-hydroxyphosphonates, primary, secondary tertiary-alcohols and phenols with HMDS was achieved in high to excellent yields using iron(III) trifluoroacetate [Fe(F₃CCO₂)₃] as an easily avai

Full text of DOI:10.1016/j.jorganchem.2008.05.018

Journal of Organometallic Chemistry 693 (2008) 2711–2714
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Iron(III) trifluoroacetate [Fe(F CCO ) ] as an easily available, non-hygroscopic,
3
2 3
non-corrosive, highly stable and a reusable Lewis Acid catalyst: Efficient
O-silylation of -hydroxyphosphonates, alcohols and phenols by
hexamethyldisilazane (HMDS) under solvent-free conditions
a
Habib Firouzabadi a,*, Nasser Iranpoor , Abbas Ali Jafari , Mohammad Reza Jafari c
a,*
b
a
Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
Department of Chemistry, Faculty of Sciences, Yazd University, Yazd 89195-741, Iran
Faculty of Pharmacy, Shiraz Medical Sciences University, Shiraz, Iran
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
O-Silylation of hydroxyl groups of
phenols with HMDS was achieved in high to excellent yields using iron(III) trifluoroacetate [Fe(F
a
-hydroxyphosphonates, primary, secondary tertiary-alcohols and
2 3
CCO ) ]
Received 23 February 2008
Accepted 13 May 2008
Available online 21 May 2008
3
as an easily available and a cost effective, non-hygroscopic, non-corrosive, highly stable and an efficient
catalyst under solvent-free conditions. As a typical reaction, we have scaled up silylation of diphenyl
methanol to 20 mmol of the substrate in order to show that the catalyst is quite effective for scaled up
operation. The catalyst was easily isolated by simple filtration and recycled for silylation of diphenyl
methanol for several runs without loosing its catalytic activity.
Keywords:
Iron(III) trifluoroacetate
Hexamethyldisilazane
Trimethylsilyl ether
Hydroxy compounds
Ó 2008 Elsevier B.V. All rights reserved.
a
-Hydroxyphosphonate
1
. Introduction
Protection of functional groups is an important sequence in mul-
(DEAD)/pyridinium p-toluenesulfonate (PPTS) [8], with allylsilanes
in the presence of catalytic amounts of p-toluenesulfonic acid [9],
iodine [10], trifluoromethanesulfonic acid [11], or Sc(OTf)
3 2 3 5 2
(Me Si) catalyzed by PdCl(g -C H ) /PPh3 [13]. Some of these
3
[12],
3
ti-step syntheses of complex organic molecules. The role of silyl
groups has already been recognized as an important part of organic
chemistry from both analytical and synthetic point of views, espe-
cially as protecting group in many syntheses with reasonable com-
methods suffer from use of expensive silylating agents and cata-
lysts, using hazardous chemicals such as DEAD and also not easily
available reagents or catalysts and highly moisture sensitive
compounds [6–8].
3
plexity [1–3]. Trimethylsilyl group (Me Si) is one of the most
popular and a widely used tool for masking hydroxyl functional
groups. This transformation enhances solubility in non-polar sol-
vents, increases thermal stability and in addition trimethylsilylation
of hydroxyl compounds is used extensively to increase volatility of
the compounds for gas chromatography and mass spectrometry as
well. Several methods have been reported for this aim, including
the reaction of an alcohol with trimethylsilyl halides in the presence
of stoichiometric amount of a tertiary amine [4,5], with trimethyl-
silyl triflate, which is more reactive than the chloride [6], with
Hexamethyldisilazane (HMDS) has been used as a source of
Me Si moiety for protection of hydroxyl groups. HMDS is an inex-
3
pensive and commercially available compound. Its handling does
not require special precautions, and the workup of the reaction
mixture is not a time-consuming process because the by product
of the reaction is ammonia. For these reasons, this compound is
very popular silylating agent and its use for masking functional
groups specially the-OH ones is of interest and demands. The main
problem of using HMDS for the above mentioned transformation is
its slow rate of the reaction. However, varieties of catalysts have
been developed and introduced to promote the rate of the reaction
by this silylating agent [14–25]. Along this line, we have intro-
R
3
Si–H activated by dirhodium(II) perfluorooctanoate [Rh
2 4
(PFO) ]
[
7], with Ph P–SiEt in the presence of diethyl azodicarboxylate
2
3
duced catalysts for the activation of HMDS such as; ZnCl
N-liganded metal chlorides [27], I
tungstophosphoric acid [30] and triflates such as; Al(OTf)
Cu(OTf) [32] and Mg(OTf) [33].
2
[26],
2
[28], metalloporphirins [29],
*
Corresponding authors. Tel.: +711 2284822; fax: +711 2286008.
E-mail addresses: firouzabadi@chem.susc.ac.ir (H. Firouzabadi), iranpoor@chem.
susc.ac.ir (N. Iranpoor).
3
[31],
2
2
0
022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.05.018

2
712
H. Firouzabadi et al. / Journal of Organometallic Chemistry 693 (2008) 2711–2714
HMDS, Fe(F CCO )
product (GC) was isolated in high to excellent yields (90–97%) after
evaporation of the solvent (Tables 2 and 3).
3
2 3
ROH
ROSiMe
3
Solvent-free, rt
2
.2.1. Semi large-scale silylation of diphenyl methanol as a typical
procedure
To a mixture of diphenyl methanol (20 mmol, 3.44 g) and HMDS
14 mmol, 2.26 g), Fe(F CCO was added (0.5 mmol,0.14 g) at
Scheme 1.
(
3
2 3
)
Even though, the silylation ability of HMDS has been promoted
room temperature and the resulting mixture was stirred vigor-
ously by a mechanical stirrer. The progress of the reaction was
monitored by TLC or GC. After completion of the reaction
in the presence of these catalysts, yet some drawbacks such as long
reaction times, drastic reaction conditions and sometimes, accord-
ing to the nature of the catalyst, tedious workup is an obligatory
process. However, in order to eliminate or minimize the existing
problems for this important reaction, introduction of new catalysts
which are cost effective, recyclable, none-corrosive, non-hygro-
scopic with high efficiency is of demand, especially for large-scale
operations.
(
2 2 2
30 min), 20 mL of an organic solvent (CH Cl , Et O or petroleum
ether) was added to the reaction mixture and the catalyst was
filtered and separated for recycling. The organic layer was washed
with water (10 mL) and dried over anhydrous Na SO . Highly pure
2 4
product (GC) was isolated in 95% yield after evaporation of the
solvent (Table 2, entry 10).
3
Iron(III) chloride (FeCl ) has emerged as a potential catalyst in
affecting various organic transformations due to its high catalytic
activity, availability and economic viability [40]. However, serious
3
. Results and discussion
technical problems encountered using FeCl
hygroscopic, and also a highly corrosive material. Therefore,
replacement of FeCl with a non-hygroscopic and a non-corrosive
salt of iron(III) is worthy of attention and is of practical importance.
For this purpose, iron(III) trifluoroacetate [Fe(F CCO ] which is a
3
such as; being high
Due to the current challenges for developing solvent-free and
environmentally less hazardous synthetic methods [35,36], we
have studied the solvent-free reaction of diphenylmethanol as a
model compound with HMDS in the presence of a catalytic amount
3
3
2 3
)
of Fe(CF
3
CO
2
)
3
at room temperature. The optimized molar ratio of
CCO was found to be 1 mmol/
.7 mmol/2.5 mol% in order to complete the reaction within
0 min producing the desired silyl ether in 95% isolated yield
cost effective, stable, efficient, and non-corrosive and a moisture
resistant compound has been prepared to be used as a catalyst in
diphenylmethanol/HMDS/Fe(F
3
2 3
)
0
1
(
organic reaction. Fe(F
yield as a red-break powder by the addition of FeCl
3
CCO
2
)
3
is easily prepared in a quantitative
to the reflux-
3
Table 1, entry 1). The catalyst was easily separated and isolated
by simple filtration after addition of an organic solvent such as
petroleum ether, Et O or CH Cl to the reaction mixture. The iso-
ing trifluoroacetic acid. The handling of this salt is easy and safe
and can be stored in a capped bottle in the laboratory for months
without observable change in its physical and chemical properties.
To the best of our knowledge, the use of this compound as a cata-
2
2
2
lated catalyst was reused for the similar reaction for three runs
without observable loss of its catalytic activity (Table 1, entries
lyst is rare in the literature. However, we have employed Fe(F
3
C-
1
–3). In order to show that the catalyst is also active in solution,
the reaction of diphenylmethanol (1 mmol) with HMDS (0.7 mmol)
in the presence of a catalytic amount (2.5 mol%) of Fe(F CCO in
CH Cl has been studied at room temperature. The reaction pro-
CO as an effective catalyst for the efficient ring opening of
2 3
)
À
À
À
À
À
3
epoxides with ROH, H
philes [34].
2
O, AcOH, Cl , Br , I , SCN , NO
nucleo-
3
2 3
)
2
2
Now in this communication, we report another important cata-
lytic activity of Fe(F CCO for the activation of HMDS for protec-
ceeded well and the desired silyl ether was isolated in 95% yield
within 20 min (Table 1, entry 4). As it is evident from the results,
the reaction rate in solution is rather slower than the similar reac-
tion proceeded in the absence of solvent. In the absence of the cat-
3
2 3
)
tion of different hydroxyl groups as their trimethyl silyl ethers at
room temperature under solvent-free conditions (Scheme 1).
alyst similar reaction did not proceed properly in CH
Table 1, entry 5) even after 24 h (<8% by GC).
However, then we applied similar solvent less conditions to
structurally diverse primary, secondary and tertiary alcohols and
phenols. The reactions proceeded well at room temperature to
yield the desired silyl ethers in excellent yields (Table 2, entries
2 2
Cl solution
2
. Experimental
(
2.1. General remarks
Chemicals were purchased from Merck and Fluka Chemical
Companies. All the products are known and were characterized
by comparison of their physical data with those reported in the lit-
erature. IR spectra were run on a Shimadzu model 8300 FT-IR spec-
trophotometer. NMR spectra were recorded on a Bruker Avance
DPX-250. The purity of the products and the progress of the reac-
tions were accomplished by TLC on silica-gel polygram SILG/UV254
plates or by a Shimadzu Gas Chromatograph GC-14A instrument
with a flame ionization detector.
1
–15).We have learnt that for completion of silylation of substrates
Table 1
Silylation of diphenylmethanol by HMDS catalyzed by Fe(F
ature
3
CCO
2
)
3
at room temper-
OH
HMDS, Fe(F CCO )
OSiMe3
3
2 3
2.2. General procedure for the silylation of hydroxyl group of alcohols,
phenols and -hydroxyphosphonates
a
r.t.
To a mixture of hydroxyl compound (1.0 mmol) and HMDS
0.7–1.5 mmol, 0.113–0.226 g) was added 2.5–5 mol% of Fe(F C-
CO at room temperature and the resulting mixture was stirred
(
3
2
)
3
Entry
Run
Solvent
Time (min)
Yield (%)
by a glass rod. The progress of the reaction was monitored by
TLC or GC. After completion of the reaction, 10 mL of an organic
1
2
3
4
5
1st
2nd
3rd
1st
–
–
–
–
CH
CH
10
12
12
20
95
93
94
95
solvent (CH
tion mixture and filtered. The organic layer was washed with
0 mL of water and dried over anhydrous Na SO . Highly pure
2 2 2
Cl , Et O or petroleum ether) was added to the reac-
2
Cl
Cl
2
2
2
24 h
<8%
1
2
4

H. Firouzabadi et al. / Journal of Organometallic Chemistry 693 (2008) 2711–2714
2713
Table 2
biology, industry and also they are useful precursors for the prep-
aration of organic compounds. -Acidic hydrogen of -trim-
ethylsilyloxyphosphonates can be deprotonated with bases such
as lithium diisopropylamide to generate relatively stable -carban-
ionic species. However, C–P and Si–O bonds present in -trim-
ethylsilyloxyphosphonates are easily hydrolyzed by acids or
bases. Therefore, the in situ generated -carbanionic species
Results of silylation of different –OH groups by HMDS catalyzed by Fe(F
room temperature
3 2 3
CCO ) at
a
a
Entry
1
Product
Time (min)
5
Yield (%)
92
a
a
OSiMe
3
a
become important synthons which are equivalent to acyl anions
and can take part in carbon-carbon bond forming reactions. They
OS iMe
3
2
3
4
5
5
90
95
can react with various acylating agents to produce the
products. These can be easily converted to -hydroxy ketones after
alkaline hydrolysis of Si–O bond followed by elimination of dialkyl
phosphate. b, -Unsaturated ketones, carboxylic acids, and unsym-
a-acylated
MeO
Cl
a
OSiMe
3
c
5
metrical ketones can be prepared by alkylation of this carbocation-
ic species [37–44]. Considering these vast applications, silylation of
a
-hydroxyphosphonates becomes a highly important practical
transformation in organic synthesis. However, we have also con-
sidered silylation of diethyl -hydroxyphosphonates by HMDS
catalyzed by Fe (F CCO at room temperature. The reactions pro-
OSiMe
3
30
10
92
Cl
a
3
2 3
)
OSiMe
3
91a
ceeded well to completion with excellent isolated yields in short
reaction times. We have found that for completion of the reaction
O2N
2 2
of substrate (Table 3, entry 4) the addition of a few drops of CH Cl
OSiMe
3
to the reaction mixture facilitated the reaction to proceed to
completion in a short reaction time.
6
7
12
10
94
93
C–P and Si–O bonds are sensitive towards reaction conditions
and usually undergo cleavage. The almost isolated quantitative
yields (Table 3) of the reactions indicate that C–P and Si–O bonds
tolerate these mild reaction conditions, which are an advantage
of this method. In order to show this advantage, we have compared
CH
3
2
(CH )
6
CH
2
OSiMe
3
OSiMe
3
8
9
45
15
10
90
Table 3
OSiMe
3
Results of silylation of –OH groups of a-hydroxyphosphonates by HMDS catalyzed by
a
96
Fe(F
CCO
)
at room temperature
3
2
3
OH
OSiMe
3
HMDS, Fe(F CCO )
OSiMe
3
3
2 3
P(OEt)
O
2
P(OEt)2
O
95b
Solvent-free,rt
1
0
X
X
Entry
1
Product
Time (min)
10
Isolated yield (%)a
97
93a
1
1
1
2
2.5h
3h
OS iMe
3
OSiMe3
P(OEt)2
90a
OS iMe
3
O
Me
1
1
1
3
4
5
20
20
20
90
95
92
OSiMe3
P(OEt)2
OSiMe
3
2
3
4
10
10
20
10
95
96
95b
95
O
Br
OSiMe3
OSiMe3
P(OEt)2
OSiMe
3
O
Cl
OSiMe3
P(OEt)2
a
The molar ratio of substrate/HMDS/Fe(F
complete the reaction five drops of CH Cl is added to the reaction mixture per
mmol of the substrate.
3 2 3
CCO ) (1/1.5/0.05) and in order to
O
2
2
O N
2
1
b
For easier recycling of the catalyst and also showing that the reaction is suitable
Cl OSiMe3
for the large-scale operations, we have scaled up this reaction to 20 mmol of the
alcohol without observable difficulties.
5
P(OEt)2
O
(
1
Table 2, entries 5, 11, 12) addition of five drops of CH
mmol of the alcohols was required.
-Trimethylsilyloxyphosphonates are fascinating and impor-
tant compounds from different aspects. They are attractive in
2 2
Cl per
a
Conversion of the substrates to the corresponding silyl ethers was quantitative
1
3 2 3
based on H NMR and the molar ratio of substrate/HMDS/Fe(F CCO ) is 1/1.5/0.05.
b
a
In order to complete this reaction five drops of CH Cl2 per 1 mmol of the sub-
2
strate is added to the reaction mixture.

2
714
H. Firouzabadi et al. / Journal of Organometallic Chemistry 693 (2008) 2711–2714
Table 4
Comparison of silylation of
lyzed by Fe(F
free conditions at room temperature in excellent yields. The other
a-hydroxy (phenylmethyl)phosphonite by HMDS cata-
CCO ) and some other Lewis acids [31] at room temperature
3 2 3
strong feature of the method is the simple isolation of the catalyst
and its recycling for several runs without loosing its catalytic
activity.
Entry
Lewis Acid
Fe(F CCO
Al(OTf)
Cu(OTf)
Ce(OTf)
Hg(OTf)
FeCl
AlCl
MgCl
Time (min)
%Conversion based on 1H NMR
1
2
3
4
5
6
7
8
3
2
)
3
10
100
100
60
3
Immediate
270
Acknowledgement
2
4
180
80
2
600
10
Financial support by Iran TWAS Chapter based at ISMO and
Shiraz University Research Council are highly appreciated.
3
90
80
3
270
80
2
390
50
References
[
1] P.G.M. Wuts, T.W. Greene, Green’s Protective Groups in Organic Synthesis, 4th
ed., John Wiley & Sons, Hoboken, NJ, 2007.
HN(TMS)2
[
[
2] M. Lalonde, T.H. Chan, Synthesis (1985) 817.
3] M.A. Brook, Silicon in Organic, Organometallic, and Polymer Chemistry, Wiley,
New York, 2000.
[
4] T. Morita, Y. Okamoto, H. Sakurai, Tetrahedron Lett. 21 (1980) 835.
+
[5] T. Vesoglu, L.A. Mitscher, Tetrahedron Lett. 22 (1981) 1299.
[6] A. Bifiss, E. Castello, M. Zecca, M. Basato, Tetrahedron 57 (2001) 10391.
[7] M. Hayashi, Y. Matsuura, Y. Watanabe, Tetrahedron Lett. 45 (2004) 1409.
[8] A. Hosomi, H. Sakurai, Chem. Lett. 85 (1981) 880.
Fe(F CCO )
HN(TMS)
_
2
3
2 3
Fe(F CCO )
3
2 3
[
9] T. Veysoglu, L.A. Mitscher, Tetrahedron Lett. 22 (1981) 1299.
NH3
[10] A. Hosomi, H. Sakurai, Chem. Lett. (1981) 85.
ROH
[
11] G.A. Olah, A. Husain, B.G.B. Gupta, G.F. Salem, S.C. Narang, J. Org. Chem. 46
1981) 5212.
(
[
[
[
12] T. Suzuki, T. Watahiki, T. Oriyama, Tetrahedron Lett. 41 (2000) 8903.
13] E. Shirakawa, K. Hironaka, H. Otsuka, T. Hayashi, Chem. Commun. (2006) 3927.
14] B. Karimi, B. Golshani, J. Org. Chem. 65 (2000) 7228.
ROTMS
_
+
_
[15] S.H. Langer, S. Connell, J. Wender, J. Org. Chem. 23 (1958) 50.
+
(
TMS)NH -Fe(F CCO )
[16] P. Gauuret, S. El-Ghamarli, A. Legrand, D. Couirier, B. Rigo, Synth. Commun. 26
[
H N-Fe(F CCO ) ]
2
3
2 3
3
3
2 3
(
1996) 707.
[
[
17] Z.H. Zhang, T.S. Li, F. Yang, C.G. Fu, Synth. Commun. 28 (1998) 3105.
18] M.M. Mojtahedi, M.R. Saidi, M. Bolourtchian, M. Heravi, Phosphorus, Sulfur
Silicon Relat. Elem 177 (2002) 289.
[
19] V.H. Tillu, V.H. Jadhav, H.B. Borate, R.D. Wakharkar, Arkivok (2004) 83.
[20] N. Azizi, M.R. Saidi, Organometallics 23 (2004) 1457.
ROTMS
ROH
[
[
21] N. Azizi, R. Yousefi, M.R. Saidi, J. Organomet. Chem. 691 (2006) 817.
22] A. Khazaei, M.A. Zolfigol, Z. Tanbakouchian, M. Shiri, K. Niknam, J. Saien, Catal.
Commun. 8 (2007) 917.
Scheme 2.
[
23] R. Ghorbani-Vaghei, M.A. Zolfigol, M. Chegeny, H. Veisi, Tetrahedron Lett. 47
(
2006) 4505.
silylation of diethyl
, entry 2) by HMDS catalyzed by Fe (F
Lewis acids used for this conversion (Table 4). As it is evident from
the results presented in Table 4, both Fe (F CCO and Al(OTf)
3
show more or less similar effective activities although the other
Lewis acids were sluggish and not suitable for this conversion.
a
-hydroxy (phenylmethyl)phosphonate (Table
[24] A.V. Narsaiah, J. Organomet. Chem. 692 (2007) 3614.
[
[
[
25] D. Zareyeea, B. Karimi, Tetrahedron Lett. 48 (2007) 1277.
26] H. Firouzabadi, B. Karimi, Synth. Commun. 23 (1993) 1633.
27] H. Firouzabadi, A.R. Sardarian, Z. Khayat, B. Karimi, S. Tangestaninezhad, Synth.
Commun. 27 (1997) 2709.
3
3
CCO with some other
2 3
)
3
2
)
3
[28] H. Firouzabadi, N. Iranpoor, S. Sobhani, Tetrahedron Lett. 43 (2002) 3653.
[
[
[
[
[
29] H. Firouzabadi, A.R. Sardarian, Z. Khayat, Iran. J. Chem. Chem. Eng. 15 (1996)
1.
9
Evolution of NH gas in all these reactions was observed. In
2 3
addition, Fe(F CCO ) was easily isolated and recycled without
3
30] H. Firouzabadi, N. Iranpoor, K. Amani, F. Nowrouzi, J. Chem. Soc., Perkin Trans.
1 (2002) 2601.
31] H. Firouzabadi, N. Iranpoor, S. Sobhani, S. Ghassamipour, Synthesis (2005) 595.
and the references cited therein.
32] H. Firouzabadi, N. Iranpoor, S. Sobhani, S. Ghassamipour, Z. Amoozgar,
Tetrahedron Lett. 44 (2003) 891. and the references cited therein.
33] H. Firouzabadi, N. Iranpoor, S. Sobhani, S. Ghassamipour, J. Organomet. Chem.
3
loosing its catalytic activity.By considering these observations,
we have qualitatively proposed a mechanism that is shown in
Scheme 2.
6
89 (2004) 3197. and the references cited therein.
4
. Conclusions
[34] N. Iranpoor, H. Adibi, Bull. Chem. Soc. Jpn. 73 (2000) 675.
35] K. Tanaka, F. Toda, Chem. Rev. 100 (2000) 1025.
36] R.S. Varma, Green Chem. (1999) 43.
37] M.M. Kabachnik, E.V. Synatkova, Z.S. Novikova, G.L. Abramova, N.G. Rozhkova,
E.I. Andreeva, Vesthn. Mosk. Univ. Ser. 2: Khim. 31 (1990) 384.
[38] G.H. Birum, G.A. Richardson, US Patent, 3,113,139 (to Monsanto Chem. Co),
December, 3 (1963); Chem. Abstr. 60 (1964) 5551d.
39] R.E. Koenigkramer, H. Zimmer, Tetrahedron Lett. 21 (1980) 1017.
40] G.A. Olah, A. Wu, J. Org. Chem. 56 (1991) 902.
[41] M. Sekine, M. Nakajima, T. Hata, Bull. Chem. Soc. Jpn. 54 (1982) 218.
42] T. Hata, A. Hashizume, M. Nakajima, M. Sekine, Tetrahedron Lett. 19 (1978) 63.
43] M. Sekine, M. Nakajima, A. Kume, A. Hashizume, Bull. Chem. Soc. Jpn. 55
[
[
[
3 2 3
In this study, we have introduced Fe(F CCO ) as an easily pre-
pared, cost effective, eco-friendly, non-hygroscopic, non-corrosive,
stable and easy handling catalyst for efficient trimethyl silylation
of alcohols and phenols by HMDS. In addition, in the presence of
[
[
this catalyst, diethyl
a-trimethylsilyloxyphosphonates which are
attractive compounds in biology, industry and also they are poten-
tial precursors for the preparation of useful organic compounds,
were prepared in excellent yields without cleavage of C–P bonds.
Except in rather few cases all reactions proceeded under solvent-
[
[
(
1982) 224.
[44] K. Trusedale, J.M. Takacs, Tetrahedron Lett. 29 (1978) 2495.