Nucleophilic substitution reactions of alcohols with use of montmorillonite catalysts as solid Bronsted acids

Article abstract of DOI:10.1021/jo070416w

(Chemical Equation Presented) We have developed an environmentally benign synthetic approach to nucleophilic substitution reactions of alcohols that minimizes or eliminates the formation of byproducts, resulting in a highly atom-efficient chemical process. Proton- and metal-exchanged montmorillonites (H- and Mⁿ⁺-mont) were prepared easily by treating Na ⁺-mont with an aqueous solution of hydrogen chloride or metal salt, respectively. The H-mont possessed outstanding catalytic activity for nucleophilic substitution reactions of a variety of alcohols with anilines, because the unique acidity of the H-mont catalyst effectively prevents the neutralization by the basic anilines. In addition, amides, indoles, 1,3-dicarbonyl compounds, and allylsilane act as nucleophiles for the H-mont-catalyzed substitutions of alcohols, which allowed efficient formation of various C-N and C-C bonds. The solid H-mont was reusable without any appreciable loss in its catalytic activity and selectivity. Especially, an Al³⁺-mont showed high catalytic activity for the α-benzylation of 1,3-dicarbonyl compounds with primary alcohols due to cooperative catalysis between a protonic acid site and a Lewis acidic Al³⁺ species in its interlayer spaces.

Full text of DOI:10.1021/jo070416w

Nucleophilic Substitution Reactions of Alcohols with Use of
Montmorillonite Catalysts as Solid Brønsted Acids
Ken Motokura,† Nobuaki Nakagiri,† Tomoo Mizugaki,† Kohki Ebitani,† and
Kiyotomi Kaneda*,‡
Department of Materials Engineering Science, Graduate School of Engineering Science and Research
Center for Solar Energy Chemistry, Osaka UniVersity, 1-3 Machikaneyana, Toyonaka,
Osaka 560-8531, Japan
kaneda@cheng.es.osaka-u.ac.jp
ReceiVed March 14, 2007
We have developed an environmentally benign synthetic approach to nucleophilic substitution reactions
of alcohols that minimizes or eliminates the formation of byproducts, resulting in a highly atom-efficient
chemical process. Proton- and metal-exchanged montmorillonites (H- and Mn+-mont) were prepared easily
by treating Na+-mont with an aqueous solution of hydrogen chloride or metal salt, respectively. The
H-mont possessed outstanding catalytic activity for nucleophilic substitution reactions of a variety of
alcohols with anilines, because the unique acidity of the H-mont catalyst effectively prevents the
neutralization by the basic anilines. In addition, amides, indoles, 1,3-dicarbonyl compounds, and allylsilane
act as nucleophiles for the H-mont-catalyzed substitutions of alcohols, which allowed efficient formation
of various C-N and C-C bonds. The solid H-mont was reusable without any appreciable loss in its
catalytic activity and selectivity. Especially, an Al3+-mont showed high catalytic activity for the
R-benzylation of 1,3-dicarbonyl compounds with primary alcohols due to cooperative catalysis between
a protonic acid site and a Lewis acidic Al3+ species in its interlayer spaces.
Introduction
substitution reactions of alcohols with amides,2 1,3-dicarbonyl
compounds,3 and allylsilanes.3d,4 However, these catalysts often
are limited by low catalytic activity and selectivity, can be
difficult to reuse, and require the use of halogenated solvents.
A promising synthetic approach aiming at environmentally
benign chemistry minimizes or eliminates the formation of
byproducts, to afford high atom-efficient chemical process.1
Although the use of alcohols instead of halides and acetate
compounds as electrophiles is an ideal method because it
prevents waste salt formations (Scheme 1), catalytic substitution
of the hydroxyl group in alcohols is difficult due to their poor
leaving ability, which requires equimolar or greater amounts
of reagents. Recently, several homogeneous catalysts, such as
NaAuCl4, InCl3, ZrCl4, La, Yb, Sc, and Hf triflate, B(C6F5)3,
BF3, and p-toluenesulfonic acid have been used for nucleophilic
(2) For substitution with amide compounds: (a) Noji, M.; Ohno, T.; Fuji,
K.; Futaba, N.; Tajima, H.; Ishii, K. J. Org. Chem. 2003, 68, 9340. (b)
Terrasson, V.; Marque, S.; Georgy, M.; Campagne, J.-M.; Prim, D. AdV.
Synth. Catal. 2006, 348, 2063.
(3) For substitution with 1,3-dicarbonyl compounds: (a) Bisaro, F.;
Prestat, G.; Vitale, M.; Poli, G. Synlett 2002, 11, 1823. (b) Gullickson, G.
C.; Lewis, D. E. Aust. J. Chem. 2003, 56, 385. (c) InCl3: Yasuda, M.;
Somyo, T.; Baba, A. Angew. Chem., Int. Ed. 2006, 45, 793. (d) Sanz, R.;
Mart´ınez, A.; Miguel, D.; AÄ lvarez-Gutie´rrez, J. M.; Rodr´ıguez, F. AdV.
Synth. Catal. 2006, 348, 1841.
(4) For substitution with allylsilane: (a) BF3: Cella, J. A. J. Org. Chem.
1982, 47, 2125. (b) HN(SO2F)2: Kaur, G.; Kaushik, M.; Trehan, S.
Tetrahedron Lett. 1997, 38, 2521. (c) BF3‚Et2O: Schmitt, A.; Reiâig, H.-
U. Eur. J. Org. Chem. 2000, 3893. (d) B(C6F5)3: Rubin, M.; Gevorgyan,
V. Org. Lett. 2001, 3, 2705. (e) InCl3: Yasuda, M.; Saito, T.; Ueba, M.;
Baba, A. Angew, Chem., Int. Ed. 2004, 43, 1414. (f) ZrCl4: Sharma, G. V.
M.; Reddy, K. L.; Lakshmi, P. S.; Ravi, R.; Kunwar, A. C. J. Org. Chem.
2006, 71, 3967.
† Graduate School of Engineering Science.
‡ Research Center for Solar Energy Chemistry.
(1) (a) Trost, B. M. Science 1991, 254, 1471. (b) Sheldon, R. A.
CHEMTECH 1994, 38. (c) Sheldon, R. A. Pure Appl. Chem. 2000, 72,
1233.
10.1021/jo070416w CCC: $37.00 © 2007 American Chemical Society
Published on Web 07/13/2007
6006
J. Org. Chem. 2007, 72, 6006-6015

Nucleophilic Substitution Reactions of Alcohols
SCHEME 1. (A) Catalytic Substitution of Alcohols without Salt Formation and (B) Stoichiometric Substitution of Halides
SCHEME 2. Montmorillonites-Catalyzed Substitution of
Nitrogen Compounds, 1,3-Dicarbonyls, and Allylsilane
Results and Discussion
Preparation and Characterization of Proton- and Metal-
Exchanged Montmorillontes. The H-mont was prepared from
a sodium-exchanged montmorillonite (Na+-mont; Na 2.69%,
Al 11.8%, Fe 1.46%, Mg 1.97%), using an aqueous solution of
hydrogen chloride. X-ray diffraction (XRD) verified retention
of a layered structure. The exchange degree of sodium cations
in the H-mont was 98.9%, and the absence of chlorine atom
was confirmed by EDX analysis. The specific surface area of
the H-mont was 138 m2 g-1 as determined by the BET-plot
based on the nitrogen adsorption isotherms. The presence of
Brønsted acid sites in the H-mont was confirmed by adsorption
of pyridine: the IR spectrum of the H-mont upon pyridine
treatment showed a peak at 1543 cm-1 due to protonated
pyridine (Figure 1), while the treatment of the Na+-mont with
pyridine gave no peaks at 1543 cm-1.8 The IR peaks near 1445
cm-1 ascribed to pyridine adsorbed on a Lewis acid site were
not observed.8 Temperature-programmed desorption of ammonia
(NH3-TPD) analysis revealed that the quantity and the strength
(∆H)9 of acid sites in the H-mont were 0.86 mmol g-1 and 111
As an alternative strategy for homogeneous acid-catalyzed
reactions, we have focused on heterogeneous Brønsted and
Lewis acid catalysts based on montmorillonites (monts).5,6
Monts are hydrophilic clays with a layered structure and have
been investigated as environmentally friendly and reusable
catalysts. The ion-exchangeable ability of their interlayer spaces
allows the introduction of various metals between the layers.
In the course of our studies on the metal-cation-exchanged
montmorillonite catalysts (Mn+-monts), two types of metal ion
species with unique structures within the interlayers of the monts
have been defined: a chain-like metal species and monomeric
aqua complexes.6a,d These Mn+-monts exhibited high catalytic
activities for various organic transformations. In addition, we
have recently found that a simple proton-exchanged montmo-
rillonite (H-mont) showed excellent catalytic performance for
nucleophilic addition of 1,3-dicarbonyls and nitrogen compounds
to unactivated alkenes.7
kJ mol-1 7a
, respectively.
The mont-enwrapped metal cations, Al3+, Fe3+, Ti4+, and
Cu2+, were prepared by treating the Na+-mont with an aqueous
solution of the appropriate metal chloride or nitrate. Among
the Mn+-monts, the catalytic behavior of the Al3+-mont was
particularly useful.10 From XRD analysis, the layered structure
was maintained during the above treatment with a basal spacing
of 3.9 Å. Elemental analysis showed that the degree of exchange
of sodium cations in the Al3+-mont was 96.7%; Al atom content
increased from 11.8 to 12.9 wt %. The absence of chlorine atom
was confirmed by EDX analysis. BET-plot produced a value
of 48 m2 g-1 for the surface area of the Al3+-mont. The Al3+
-
Here, we present the nucleophilic substitution of hydroxyl
groups in alcohols using proton- and metal-exchanged mont-
morillonite (H- and Mn+-mont) catalysts (Scheme 2), in which
a variety of nucleophiles readily reacted with alcohols to form
C-N and C-C bonds. These mont catalysts showed high
catalytic activities and selectivities, and then were reusable
without any appreciable loss of catalytic performance. This is
the first heterogeneous catalyst system for nucleophilic substitu-
tion reactions of alcohols with anilines, amides, 1,3-dicarbonyl
compounds, and allylsilane.
mont possessed both Brønsted and Lewis acid sites: the IR
spectrum of the Al3+-mont showed peaks at 1543 cm-1 upon
treatment with pyridine due to protonated pyridine, while a peak
at 1445 cm-1 was assigned to pyridine adsorbed on the Lewis
acid sites (Figure 1).8 NH3-TPD revealed that the quantity and
the strength (∆H) of acid sites in the Al3+-mont were 0.75 mmol
g-1 and 132 kJ mol-1 11
, respectively. The acid strength of the
Al3+-mont was large compared to that of the H-mont, which
may originate from the Lewis acid site on the Al species in the
interlayer. The 29Si MAS NMR spectra of the Al3+-mont
indicated the presence of tetrahedron SiO4 species, assignable
(5) Mont-catalyzed organic synthesis: (a) Pinnavaia, T. J. Science 1983,
220, 365. (b) Laszlo, P. Acc. Chem. Res. 1986, 19, 121. (c) Izumi, Y.;
Onaka, M. AdV. Catal. 1992, 38, 245.
(6) Brønsted acid catalysis: (a) Ebitani, K.; Kawabata, T.; Nagashima,
K.; Mizugaki, T.; Kaneda, K. Green Chem. 2000, 2, 157. (b) Motokura,
K.; Fujita, N.; Mori, K.; Mizugaki, T.; Ebitani, K.; Kaneda, K. J. Am. Chem.
Soc. 2005, 127, 9674. Lewis acid catalysis: (c) Kawabata, T.; Mizugaki,
T.; Ebitani, K.; Kaneda, K. J. Am. Chem. Soc. 2003, 125, 10486. (d)
Kawabata, T.; Kato, M.; Mizugaki, T.; Ebitani, K.; Kaneda, K. Chem. Eur.
J. 2005, 11, 288.
(7) (a) Motokura, K.; Fujita, N.; Mori, K.; Mizugaki, T.; Ebitani, K.;
Kaneda, K. Angew. Chem., Int. Ed. 2006, 45, 2605. (b) Motokura, K.;
Nakagiri, N.; Mori, K.; Mizugaki, T.; Ebitani, K.; Jitsukawa, K.; Kaneda,
K. Org. Lett. 2006, 8, 4617.
(8) (a) Daniell, W.; Topsøe, N.-Y.; Kno¨zinger, H. Langmuir 2001, 17,
6233. (b) Parry, E. P. J. Catal. 1963, 2, 371.
(9) (a) Niwa, M.; Katada, N.; Sawa, M.; Murakami, Y. J. Phys. Chem.
1995, 99, 8812. (b) Nakao, R.; Kubota, Y.; Katada, N.; Nishiyama, N.;
Kunimori, K.; Tomishige, K. Appl. Catal., A 2004, 273, 63.
(10) For organic syntheses with Al3+-exchanged montmorillonites, see:
(a) Kikuchi, E.; Matsuda, T.; Ueda, J.; Morita, Y. Appl. Catal. 1985, 16,
401. (b) Matsuda, T.; Matsukata, M.; Kikuchi, E.; Morita, Y. Appl. Catal.
1986, 21, 297. (c) Tateiwa, J.; Horiuchi, H.; Hashimoto, K.; Yamauchi, T.;
Uemura, S. J. Org. Chem. 1994, 59, 5901. (d) Tateiwa, J.; Hayama, E.;
Nishimura, T.; Uemura, S. J. Chem. Soc., Perkin Trans. 1997, 1923.
(11) The strength of the Al3+-mont was determined by the method of
Niwa and Katada, see ref 9.
J. Org. Chem, Vol. 72, No. 16, 2007 6007

Motokura et al.
effect. In 2005, the hydroamination of alkenes with anilines
using homogeneous Brønsted acid catalysts was demonstrated
by Bergman and co-workers,17 but Brønsted acid-catalyzed
substitution of hydroxyl groups of alcohols with anilines has
never been reported.18 Here, we present the first report on acid-
catalyzed nucleophilic substitution reactions of hydroxyl groups
of allylic and benzylic alcohols with anilines using the H-mont
catalyst.
The H-mont catalyst was used without any pretreatment such
as calcinations, which induces decreasing catalytic activity. XRD
and TPD analyses revealed the destruction of layered structure
and a decrease of the acid amount in the H-mont after
calcination. Substitution of a hydroxyl group in 2-cyclohexen-
1-ol (2a) with aniline (1a) was examined with use of hetero-
geneous and homogeneous acids, as shown in Table 1. The
H-mont showed the highest catalytic activity and possessed
excellent selectivity toward N-(2-cyclohexen-1-yl)aniline (3a)
together with aromatic-substituted byproducts (4a and 5a) (entry
1). H-beta, H-USY, and Al3+-mont also were effective catalysts
for this substitution reaction (entries 2-4), while H-mordenite
was less active despite its strong acidity (entry 5). Reaction with
H-ZSM-5 zeolite barely proceeded due to its restricted pore size
(entry 6). Notably, for homogeneous strong acids, such as H2SO4
and p-toluenesulfonic acid, neutralization of acids with basic
aniline gave inactive salts without the desired N-allylated product
(entries 7 and 8).
Next, substitution reactions of a variety of allylic alcohols
with aniline derivatives were investigated, as shown in Table
2. Electron-withdrawing groups at the para position of anilines
enhanced both reaction rate and selectivity toward N-allylated
products (entries 2-4), while the methoxy of an electron-
donating substituent favored an ortho adduct (entry 5). To extend
the scope of the allylic alcohols, both aliphatic and aromatic
allylic alcohols were examined as potential substrates in the
reaction of 1a (entries 6-9). The substitution of a hydroxyl
group of cinnamyl alcohol (2d) with 1a afforded ortho and para
adducts (entry 8), while an N-allylated product was formed
selectively with 4-nitroaniline (1c) (entry 9). Notably, the
reactions of both 1-methyl-2-propen-1-ol (2e) and 1-buten-3-
ol (2f) with 1a afforded the same N-(2-butenyl)aniline as the
major product (eqs 1 and 2).
FIGURE 1. The IR spectra of pyridine adsorbed on the Al3+-mont
(s) and H-mont (---): (O) pyridinium ion on the mont and (×) pyridine
coordinated to Lewis acid site.
to the montmorillonite structure (chemical shift of δ -94 ppm,
Figure 2S, Supporting Information).12 In addition, a signal
assignable to a SiO4 site connecting two Al sites in the second
coordination sphere of the Si-O framework also was observed
(-86 ppm, Figure 2S, Supporting Information).12 Theses results
indicate that the Al species introduced into the mont interlayer
by ion exchange are located onto the silicate surface.
Substitution with Nitrogen Compounds. N-Allyl and -benz-
yl anilines are very important synthetic intermediates for a
variety of biologically active compounds.13 As one of the most
common methodologies for the synthesis of N-allyl anilines,
palladium-catalyzed allylic substitution usually requires large
amounts of activators and expensive Pd catalysts.14 In addition,
the use of allylic alcohols as allyl sources15 has been investigated
for environmentally benign syntheses;1 however, most catalytic
systems require allylic halides, acetates, or carbonates due to
the poor leaving ability of the hydroxyl groups. Few reports
exist on the direct catalytic synthesis of N-benzylated anilines
from anilines and benzylic alcohols because benzylic species
are not suitable for transition-metal-catalyzed reactions based
on π-allyl chemistry.16 In general, anilines are unsuccessful for
acid-catalyzed nucleophilic reactions due to their buffering
(12) Thompson, J. G. Clay Miner. 1984, 19, 229.
(13) (a) Zbinden, K. G.; Banner, D. W.; Ackermann, J.; D’Arcy, A.;
Kirchhofer, D.; Ji, Y.-H.; Tschopp, T. B.; Wallbaum, S.; Weber, L. Bioorg.
Med. Chem. 2005, 15, 817. (b) Kvœrnø, L.; Ritter, T.; Werder, M.; Hauser,
H.; Carreira, E. M. Angew. Chem., Int. Ed. 2004, 43, 4635. (c) Molteni,
V.; Penzotti, J.; Wilson, D. M.; Termin, A. P.; Mao, L.; Crane, C. M.;
Hassman, F.; Wang, T.; Wong, H.; Miller, K. J.; Grossman, S.; Grootenhuis,
P. D. J. J. Med. Chem. 2004, 47, 2426. (d) Minutolo, F.; Bertini, S.; Betti,
L.; Di Bussolo, V.; Giannaccini, G.; Placanica, G.; Rapposelli, S.;
Spielmann, H. P.; Macchia, M. Il Farmaco 2003, 58, 1277.
(14) (a) Tsuji, J. Transition Metal Reagents and Catalysts; Wiley: New
York, 2000. (b) Trost, B. M.; Keinan, E. J. Am. Chem. Soc. 1978, 100,
7779. (c) Lu, X.; Jiang, X.; Tao, X. J. Organomet. Chem. 1988, 344, 109.
(d) Giambastiani, G.; Poli, G. J. Org. Chem. 1998, 63, 9608. (e) Ozawa,
F.; Okamoto, H.; Kawagishi, S.; Yamamoto, S.; Minami, T.; Yoshifuji, M.
J. Am. Chem. Soc. 2002, 124, 10968. (f) Akiyama, R.; Kobayashi, S. J.
Am. Chem. Soc. 2003, 125, 3412.
(15) For reaction of allylic alcohols as allylating reagents, see: (a) Ozawa,
F.; Okamoto, H.; Kawagishi, S.; Yamamoto, S.; Minami, T.; Yoshifuji, M.
J. Am. Chem. Soc. 2002, 124, 10968. (b) Manabe, K.; Kobayashi, S. Org.
Lett. 2003, 5, 3241. (c) Kinoshita, H.; Shinokubo, H.; Oshima, K. Org.
Lett. 2004, 6, 4085. (d) Kimura, M.; Mukai, R.; Tanigawa, N.; Yanaka, S.;
Tamaru, Y. Tetrahedron 2003, 59, 7767. (e) Kayaki, Y.; Koda, T.; Ikariya,
T. J. Org. Chem. 2004, 69, 2595.
Because the H-mont catalyst exhibited high catalytic activity
in the allylic substitution of alcohols with aniline derivatives,
the substitution of a hydroxyl group in benzylic alcohols with
anilines also was examined and afforded N-benzyl anilines.
Results with various benzylic alcohols and anilines are shown
in Table 3. Reactions of para-substituted anilines with benzhy-
drol (2g) gave N-benzylated products exclusively (entries 2-6).
(16) For transition metal-catalyzed N-alkylation of anilines with alcohols
via tandem oxidation-condensation-hydrogenation, see: (a) Fujita, K.-i.;
Li, Z.; Ozeki, N.; Yamaguchi, R. Tetrahedron Lett. 2003, 44, 2687. (b)
Gelman, F.; Blum, J.; Avnir, D. New J. Chem. 2003, 27, 205.
(17) Anderson, L. L.; Arnold, J.; Bergman, R. G. J. Am. Chem. Soc.
2005, 127, 14542.
(18) During preparation of this manuscript, substitution of benzylic
alcohols with only p-niroaniline was reported, see refs 2b and 3d.
6008 J. Org. Chem., Vol. 72, No. 16, 2007

Nucleophilic Substitution Reactions of Alcohols
TABLE 1. Substitution of Alcohol 2a with Aniline 1a with Use of Various Acid Catalystsa
acid amount
(mmol/g)b
acid strength
(kJ/mol)b
pore size
(Å)
yield
(%)c
entry
catalyst
H-mont
3a:4a:5ac
1
2
3
4
5
6
7
8
9
0.86
0.51
0.53
0.75
1.07
0.87
111
126
122
132
160
130
88
80
77
72
12
10
86:10:4
83:7:10
75:16:9
88:8:4
77:10:13
91:6:3
H-beta
7.6 × 6.4
7.4 × 7.4
H-USY
Al3+-mont
H-mordenite
H-ZSM-5
6.5 × 7.0
5.1 × 5.5
d
H2SO4
tracee
tracee
n.r.
p-TsOH‚H2Od
none
a 1a (2 mmol), 2a (1 mmol), catalyst (0.1 g), n-heptane (2 mL), 80 °C, 24 h. b Determined by NH3-TPD. c Combined yield, determined by GC. d 0.1
mmol. e Inactive salt was formed by the neutralization of acid with 1a.
TABLE 2. Substitution of Allylic Alcohols with Anilines with Use
of the H-mont Catalysta
TABLE 3. Substitution of Benzylic Alcohols with Anilines with
Use of the H-mont Catalysta
entry
aniline
1a
4-Cl 1b
4-NO2 1c
3,5-CF3 1d
4-OMe 1e
1a
alcohol t (h)/T (°C) yield (%)b
3:4:5
1
2a
2a
2a
2a
2a
2b
2c
2d
2d
24/80
2/80
1/80
88
95 (76c)
81c
86:10:4
95:5:0
100:0:0
100:0:0
7:93:0
2
3d
4
isolated
yield (%)
2/80
75
entry
aniline
1a
1b
1c
1c
4-Me 1f
1e
1c
1a
alcohol
t (h)/T (°C)
3:4:5b
5
24/150
24/40
24/150
3/150
1/100
59c
1
2
3
4
5
6
7
8
9
2g
2g
2g
2g
2g
2g
2h
2l
1/150
3/120
1/100
1/100
7/150
30/150
1/100
15/125
1/100
30/100
1/100
96
83
97
98c
66
39
93
93b
77
99b
93
51:0:49
100:0:0
100:0:0
100:0:0
100:0:0
100:0:0
100:0:0
54:28:18
100:0:0
82:9:9
6
70
92:4:4
7e
8
1a
1a
1c
29
100:0:0
0:65:35
100:0:0
73f
9d
78c,f
a Aniline (2 mmol), alcohol (1 mmol), H-mont (0.1 g), n-heptane (2 mL),
24 h. b Determined by GC. c Isolated yield. d 1,4-Dioxane (2 mL) was used
as a solvent. e Aniline (1 mmol), alcohol (2 mmol). f Only (E)-product was
detected.
1c
1a
1c
2l
2n
2n
10
11
100:0:0
Similar to the above allylic substitution reaction, an electron-
withdrawing group at the para position of anilines enhanced
their reactivity (entries 2 and 3). Other secondary alcohols of
1-phenylethanol (2l) and 1-(2-naphthyl)ethanol (2n) functioned
as good substrates (entries 8-11). This is the first report of
successful direct N-benzylation of anilines with alcohols. In the
reactions of both allylic and benzylic alcohols with 1a, para-
and ortho-alkylated products were formed (Table 2, entries 1,
6, and 8; Table 3, entries 1, 8, and 10). These aromatic allylated
and benzylated products became the major product at longer
reaction times and higher temperatures, which indicates that
N-adducts undergo a Hofmann-Martius rearrangement.17,19,20
a Aniline (2 mmol), alcohol (1 mmol), 1,4-dioxane (2 mL), H-mont (0.1
g). b Determined by GC. c Third reuse experiment.
The use of indoles instead of anilines gave 3-benzylated and
-allylated indoles in this H-mont catalyst system with alcohols
(Table 4). Both indole (6a) and N-methylindole (6b) readily
reacted with 2g, affording the corresponding 3-benzylated
indoles. An allylic alcohol of 2a also was a good electrophile.
No N-alkylated product was detected for any of these indoles.
N-Benzylation and allylation of various amide compounds
also were examined in the presence of the H-mont catalyst, as
summarized in Table 5. For example, the reaction of p-
toluenesulfonamide (7a) with 2g proceeded smoothly to afford
a 94% isolated yield of N-(diphenylmethyl)-p-toluenesulfona-
(19) March, J. AdVanced Organic Chemistry: Reactions, Mechanism,
and Structure, 4th ed; John Wiley & Sons: New York, 1992; p 560.
(20) After reaction of 2a with 1a under the reaction conditions of Table
1, entry 1 (88% combined yield, N:ortho:para adducts ) 86:10:4), further
treatment of the reaction mixture at 150 °C for 24 h afforded a 59% yield
of the ortho adduct as a major product (75% combined yield, N:ortho:para
) 9:79:12).
(21) (a) O’Brien, P.; Childs, A. C.; Ensor, G. J.; Hill, C. L.; Kirby, J. P.;
Dearden, M. J.; Oxenford, S. J.; Rosser, C. M. Org. Lett. 2003, 5, 4955.
(b) Lee, E. E.; Batey, R. A. Angew. Chem., Int. Ed. 2004, 43, 1865.
J. Org. Chem, Vol. 72, No. 16, 2007 6009

Motokura et al.
CHART 1
TABLE 4. Substitution of Alcohol with Indoles with Use of the
H-mont Catalystsa
TABLE 6. r-Benzylation and Allylation of Various 1,3-Dicarbonyl
Compounds with Alcohols with Use of the H-mont Catalysta
isolated
entry
indole
alcohol
yield (%)
1
2
3
4
5
X ) Y ) H (6a)
2g
2g
2g
2l
99
90
70
77
66
isolated
X ) Me, Y ) H (6b)
entry
1,3-dicarbonyl
alcohol
T (°C)
yield (%)b
X ) H, Y ) Me (6c)
6a
6a
1
2
8a
8a
8a
8a
8a
8a
8b
8c
8d
8f
2l
2l
100
100
150
150
100
90
100
150
100
100
90
90
91c
80
2a
3
2m
2n
2g
2a
2l
2l
2l
2l
2a
a Indole (2 mmol), alcohol (1 mmol), n-heptane (2 mL), H-mont (0.1
g), 100 °C, 12 h.
4d
5
72
91
6
80e
86g
86g
88g
51g
48g
7f
8d
9
TABLE 5. N-Benzylation and Allylation of Amides by Treatment
with Alcohols with Use of the H-monta
10
11
8d
a Alcohol (1 mmol), 1,3-dicarbonyl compound (1.5 mmol), catalyst (0.15
g), n-heptane (2 mL), 1 h, 100 °C. b Based on alcohol. c Fifth reuse
experiment. d 0.5 h. e GC yield. f 1,3-Dicarbonyl (1 mmol). g 1:1 diastereo-
isomers were formed (1H NMR).
be excellent nucleophiles (entries 8 and 9). In these H-mont-
catalyzed N-C bond formations with anilines and amide
compounds, the used solid catalysts were recoVered easily from
the reaction mixture and could be reused at least three times
without any appreciable loss of its actiVities and selectiVities
(Table 3, entry 4; Table 5, entry 2).
Substitution with 1,3-Dicarbonyls. The R-benzylation and
allylation of 1,3-dicarbonyl compounds are common procedures
in organic synthesis. The traditional method for benzylation of
1,3-dicarbonyls is a stoichiometric reaction with benzyl halides
in the presence of an equimolar amount of strong bases.22 The
high catalytic activity of solid Brønsted acids for the above
substitutions using nitrogen compounds encouraged us to
explore the nucleophilic substitution of hydroxyl groups in
benzylic and allylic alcohols with 1,3-dicarbonyl compounds,
which afforded R-benzylated and allylated 1,3-dicarbonyls.
The reactions of various 1,3-dicarbonyl compounds with
secondary alcohols are summarized in Table 6. The R-benzyl-
isolated
entry
amide
alcohol
yield (%)b
1
2
3
4
7a
7a
7a
7a
7a
7a
7a
7b
7c
2g
2g
2h
2l
2a
2o
2p
2g
2g
94
95c
97
60
5d
6f
7g
8
50e
97
39e
87
9g
90
a Alcohol (1.0 mmol), amide (1.5 mmol), H-mont (0.1 g), 1,4-dioxane
(2 mL), 100 °C, 2 h. b Based on the alcohol. c Third reuse experiment.
d Amide (5 mmol) was used. Alcohol was added in portions. e GC yield.
f Alcohol (1.5 mmol), 1b (1 mmol). Yield was based on 1b. g 20 h.
mide (entry 1). Notably, the reaction of 2a with 7a gave
N-cyclohex-2-enyl-p-toluenesulfonamide (entry 5), which is
usually synthesized through a tedious multistep procedures.21
Reactions of aliphatic alcohols, such as exo-2-norborneol (2o)
and cyclohexanol (2p), also proceeded (entries 6 and 7).
Furthermore, inactive aliphatic sulfonamide and carboxamide,
methanesulfonamide (7b), and benzamide (7c) were found to
(22) (a) Ranu, B. C.; Bhar, S. J. Chem. Soc., Prekin Trans. 1 1992, 365.
(b) Arumugam, S.; McLeod, D.; Verkade, J. G. J. Org. Chem. 1998, 63,
3677.
6010 J. Org. Chem., Vol. 72, No. 16, 2007

Nucleophilic Substitution Reactions of Alcohols
ation of acetylacetone (8a) with 2l proceeded in the presence
of the H-mont catalyst to give a 90% yield of 3-(1-phenylethyl)-
2,4-pentanedione (entry 1). Catalytic activity of the Al3+-mont
was slightly lower than that of the H-mont. For other zeolite
catalysts, such as H-beta, H-mordenite, and H-ZSM-5, the above
substitution reaction scarcely occurred. Sterically hindered
alcohols of 2n and 2g also reacted to afford the corresponding
diones in 72% and 91% yields, respectively (entries 4 and 5).
Notably, not only aliphatic, aromatic, and cyclic 1,3-diketones,
but also 1,3-ketoesters, underwent benzylation reaction with 2l
to give the excellent yields of the desired products (entries 1
and 7-10). Furthermore, an allylic alcohol of 2a could act as
a good substrate (entries 6 and 11).23 This H-mont catalyst
system also was applicable to aliphatic alcohols: reaction of
2o with 1,3-diketones readily proceeded to afford quantitative
yields of the corresponding products (eq 3), while 2p possessed
conducted (Table 1S, Supporting Information). The selectivity
to 9a could be improved by using the Al3+-mont catalyst instead
of the H-mont in nitromethane solvent, to afford the desired
product (yield: 51%). Yield and selectivity increased signifi-
cantly by stepwise addition of 2q (83%) (eq 5). Use of other
solvents, such as n-heptane (24%) and 1,4-dioxane (trace),
resulted in decrease of the product selectivity: no reaction
occurred with DMF and THF as solvents. Using Fe3+ (42%)-,
Ti4+ (33%)-, Cu2+ (22%)-, and H+ (43%)-exchanged montmo-
rillonites resulted in lower yields than that of the Al3+-mont.
Commercially available zeolites, such as H-beta (17%), H-USY
(trace), H-mordenite (trace), and H-ZSM-5 (trace), were less
active for this benzylation reaction. Furthermore, the homoge-
neous H2SO4-catalyzed reaction did not result in high yield
(39%).
Notably, this Al3+-mont catalyst system was applicable to
other 1,3-dicarbonyls and primary alcohols. The reaction of
benzoylacetone (8b) with 2q proceeded readily to give a 65%
yield of R-benzylated benzoylacetone (eq 6). A heteroaromatic
alcohol of 2-thiophenemethanol (2r) also reacted to afford the
corresponding R-substituted acetylacetone in good yield (eq 7).
This catalytic R-alkylation of 1,3-dicarbonyl compounds with
primary aromatic and heteroaromatic alcohols has not been
demonstrated before.
low reactivity in the substitution reaction (eq 4). In the
substitution reaction of alcohols with 1,3-dicarbonyls, only
benzylic and allylic alcohols have been used.3 The substitutions
of aliphatic alcohols were achieVed as the first example with
the H-mont catalyst. Unfortunately, reaction with diethyl
malonate as a 1,3-diester, which has a high pKa value of the
R-proton, did not occur. It should be noted that after the
substitution reaction of 2l with 8a, the used H-mont catalyst
was separated easily from the reaction mixture, and the spent
catalyst could be reused at least five times without an ap-
preciable loss of its activity and selectivity (entry 2). Initial
reaction rates did not change significantly during these recycling
experiments. To confirm whether the substitution of alcohols
occurred on the solid surface, the H-mont catalyst was removed
by filtration after ca. 50% conversion of alcohol. ICP analysis
of the filtrate of the H-mont-catalyzed reaction showed 0.03%
leaching of Al and Fe species; however, further treatment of
the filtrate under the identical reaction conditions did not afford
any product. These results strongly suggest that the substitution
reactions of alcohols proceeded on the solid mont catalyst.
To extend the scope of the alcohols used in the H-mont-
catalyzed nucleophilic addition of 1,3-dicarbonyl compounds,
a primary alcohol, benzyl alcohol (2q), was investigated as a
potential substrate. However, the H-mont-catalyzed reaction of
2q with 8a showed low selectivity toword production of the
desired R-benzylated acetylacetone (9a), accompanied by a large
amount of dibenzyl ether (10a) under the standard conditions
employed for secondary alcohols (n-heptane, 100 °C). For
development of an effective heterogeneous catalyst system, the
R-benzylation reaction of 8a with 2q as a model substrate was
Allylation with Allylsilane. Although nucleophilic allylation
of carbonyl compounds and acetals with allylsilanes is well-
known as the Sakurai-Hosomi reaction,24 a transformation that
uses alcohols as electrophiles has been rarely investigated.
Protocols for this reaction usually require stoichiometric amounts
of reagents, and few examples on catalytic allylation of alcohols
with allylsilanes have been reported.4 For the development of
a “green” allylation procedure, herein, we applied this mont-
morillonite catalyst system for the heterogeneous allylation
reaction of alcohols with allyltrimethylsilane.
The H-mont showed high catalytic activity for direct substitu-
tion of a hydroxyl group in 2g with allyltrimethylsilane (11a)
to afford allyldiphenylmethane (12a) in 96% yield (Table 2S,
Supporting Information). The Al3+-mont (74%) and mont K10
(72%) also were effective catalysts. The reaction scarcely
2-
occurred in the presence of other solid acids, such as SO4
/
ZrO2, H-USY, H-mordenite, H-ZSM-5, or the precursor Na+-
(24) (a) Sakurai, H. Pure Appl. Chem. 1982, 54, 1. (b) Sakurai, H. Pure
Appl. Chem. 1989, 57, 1759. (c) Hosomi, A. Acc. Chem. Res. 1988, 21,
200. (d) Yamamoto, Y.; Asao, N. Chem. ReV. 1993, 93, 2207. (e) Marshall,
J. A. Chem. ReV. 1996, 96, 31.
(23) Allylation of 1,3-dicarbonyls with allyl alcohols is usually catalyzed
by Pd catalysts, see ref 13.
J. Org. Chem, Vol. 72, No. 16, 2007 6011

Motokura et al.
TABLE 7. Allylation of Various Alcohols with 11a with Use of the
H-mont Catalysta
mont. Interestingly, homogeneous acids of H2SO4 and p-tolu-
enesulfonic acid gave bis(diphenylmethyl) ether (10b) as the
main product without the desired 12a.
Allylation of various alcohols with 11a is shown in Table 7.
The reaction of both electron-donating and -withdrawing groups
at the para position of benzhydrol proceeded readily, affording
the corresponding allylated products in excellent yields (entries
1-4). For reaction of 4,4′-dimethoxy benzhydrol (2k), 1,4-
dioxane was a better solvent than n-heptane because of the
greater solubility of 2k (entry 5). Several 1-arylethanol deriva-
tives reacted with 11a to afford good to moderate yields of the
allylated products (entries 6-8). Notably, reaction of an allylic
alcohol of 2a also proceeded readily to give an 88% yield of
the 1,5-diene derivative (entry 9), which is an important
precursor for various heterocyclic compounds.25 During these
allylations, isomerization of the olefinic double bonds of the
products did not occur. Treatment of the recovered H-mont with
aqueous hydrogen chloride allowed regeneration of a high
catalytic activity: an 87% yield of 12a was obtained in the
recycling experiment. The desired products were not formed
selectively when other silyl nucleophiles such as propargyl- and
alkenylsilanes were used, due to side reactions (i.e., oligomer-
ization and hydration of the silanes). The reaction of triphenyl-
methanol (2s) did not proceed efficently (entry 10) and the
reaction of the primary alcohol 2q with 12a afforded benzyl-
oxytrimethylsilane without formation of an allylation product.
The high performance of the H-mont-catalyzed reaction was
highlighted by the reaction of 10 mmol of 2g with 1.5 equiv of
11a, which proceeded successfully in the presence of 0.05 g of
the H-mont (eq 8). After the reaction, the used catalyst was
isolated
entry
alcohol
t (h)
yield (%)b
1
2
3
2g
2h
2i
2j
2k
2l
2m
2n
2a
2s
1
1
1
1
1
2
2
2
1
1
96
86
98
97
96
66
54
4c
5d,e
6c
7d
8c
9d
10
58
88f
trace
a Alcohol (1 mmol), 9a (1.5 mmol), H-mont (0.02 g), n-heptane (2 mL),
60 °C. b Based on alcohol. c 9a (2 mmol). d 9a (3 mmol). e 1,4-Dioxane (2
mL) was used as a solvent. f GC yield.
of a proton to give the allylated or benzylated product. In
general, the proton of an ammonium cation shows higher acidity
than that of the componential neutral nitrogen compound,27
therefore, proton elimination from the amine may occur
smoothly after the formation of the ammonium cation interme-
diate. Anilines with an electron-withdrawing group showed
higher reactivity than anilines with an electron-donating group,
and the reaction rate decreased with the increase of the aniline
concentration (see Figure 4S, Supporting Information). These
results indicate that an alcohol protonation might be depressed
by interaction between the acid site in the H-mont and a basic
aniline. Solid acid catalysts with weak acidity (∆H) such as
the H-mont (∆H ) 111 kJ mol-1) exhibited higher activity in
substitution reactions compared to H-mordenite having strong
acid sites (∆H ) 160 kJ mol-1). A suitable strength of the
Brønsted acid sites is required for the efficient substitution
reaction of alcohols, and prevents the neutralization by the basic
aniline,28 when compared with other heterogeneous and homo-
geneous strong acids. Furthermore, for the reactions of neutral
nitrogen compounds, amides and indoles, the two-dimensional
silicate sheets of the H-mont provide wide spaces for the
catalytic reaction, and effectively act as the macro counter anions
to decrease their anion coordination ability toward the H+ site,17
leading to high activity for generation of the allyl and benzyl
cation intermediates.6d
separated easily from the reaction mixture by a simple filtration,
and distillation of the filtrate at 200 °C under 15 mmHg gave
the desired product 12a (1.90 g; 91% isolated yield). In this
reaction, the turnover number (TON) and turnover frequency
(TOF) based on acid site of the H-mont reached 210 and 210
h-1, respectively. These values were higher than those reported
for other catalyst systems, such as ZrCl4 (TON and TOF, 49
and 196 h-1),4f InCl3 (20, 6.7 h-1),4e B(C6F5)3 (16),4d,26 and HN-
(SO2F)2 (9.6, 1.9 h-1).4b
Reaction Pathways for the Mont-Catalyzed Nucleophilic
Substitutions. (I) Nitrogen Compounds. The addition of
pyridine significantly decreased the catalytic activity of the
H-mont. Upon treatment with pyridine, the IR spectrum of the
H-mont showed a new peak at 1543 cm-1 due to a protonated
pyridine. Reactions of 2e and 2f with 1a both produced the same
product, N-(2-butenyl)aniline (eqs 1 and 2). These results suggest
that the active species for the nucleophilic substitution reaction
is a Brønsted acid site, and a plausible reaction path involving
a carbocation intermediate is illustrated in Scheme 3 and
proceeds as follows: (i) protonation of an alcohol by H+ site
and formation of an allyl or benzyl cation intermediate, (ii)
attack of a nitrogen nucleophile, followed by (iii) elimination
(II) 1,3-Dicarbonyl Compounds. Upon treatment of the
H-mont with 8a, both the keto and enol forms of 8a were
detected (Figure 2),7a therefore, a proposed reaction path might
involve the dual activation of alcohols and 1,3-dicarbonyls as
shown in Scheme 4A: (i) formation of a carbocation intermedi-
ate from an alcohol and coordination of a 1,3-dicarbonyl onto
neighboring H+ sites,29 (ii) formation of an activated enol
intermediate, and (iii) nucleophilic attack of the enol. Presum-
ably, concentrated protonic acid sites in the interlayer space
would provide higher activity of the H-mont.30
(27) For example, the pKa value of protonated aniline (3.6) is much lower
than that of aniline (30.6); see: Fu, Y.; Li, R.-Q.; Liu, R.; Guo, Q.-X. J.
Am. Chem. Soc. 2004, 126, 814.
(28) In the reaction of neutral nitrogen nucleophile of amides, this
deactivation of H+ site might not occur.
(29) Enolization of ketone is promoted by Brønsted acid, see ref 5a
and: Han, X.; Wang, X.; Pei, T.; Widenhoefer, R. A. Chem. Eur. J. 2004,
10, 6333.
(25) J. Kurth, M.; Rodriguez, M. J. Tetrahedron, 1989, 45, 6963.
(26) Reaction time was not reported.
6012 J. Org. Chem., Vol. 72, No. 16, 2007

Nucleophilic Substitution Reactions of Alcohols
SCHEME 3. A Proposed Reaction Pathway for Substitution of Alcohols with Anilines
pathway might involve the dual activation of alcohols and 1,3-
dicarbonyls by the H+ and Al3+ site, respectively (Scheme
4B): a 1,3-dicarbonyl coordinates onto the Lewis acidic Al site,
giving an activated enol intermediate that readily attacks a
protonated alcohol. Li and co-workers also reported activation
of both 1,3-dicarbonyls and alkenes using Ga(TfO)3 and TfOH
for the addition reaction.33,34 Since primary alcohols, such as
benzyl alcohol, easily undergo ether formation under acidic
conditions relative to secondary alcohols, the selective formation
of C-C coupling products requires stepwise addition of primary
alcohols into the reaction mixture, accompanied by activation
of the 1,3-dicarbonyl compounds. Effective activation of 1,3-
dicarbonyls by Lewis acidic Al sites would depress formation
of the ether, which promotes higher selectivity toward the
benzylation product compared to other catalysts.
(III) Allylsilane. Among various solid acids, reactions with
only mont clays with a layered structure achieved high yields
of 12a (Table 2S, Supporting Information). The low activity of
zeolites, such as H-USY, H-mordenite, and H-ZSM-5, is due
to their restricted small pore size that does not accommodate
the relatively large molecular size of the alcohol 2g. The addition
of pyridine significantly decreased the catalytic activity of the
H-mont, similar to that in the above reactions of nitrogen
compounds. An ether of 10b was observed during allylation of
2g with 11a with use of the H-mont. These results indicate that
the active species for these nucleophilic additions seems to be
a Brønsted acid site, and a plausible reaction path involving a
carbocation intermediate is illustrated as Scheme 5 and could
proceed as follows: (i) protonation of an alcohol by the H+
site to give a carbocation intermediate, (ii) reversible formation
of an ether, (iii) attack of an allylsilane followed by (iv)
formation of an allylated product, and (v) regeneration of the
H+ active site by hydration.35 The reaction of 10b with 11a in
the presence of water afforded the allylation product 12a in
excellent yield, while a slow reaction rate was observed in the
absence of water (eq 9). Water can promote the hydration step
(v), then the strong hydrophilic ability of the H-mont interlayers
provides the high activity for the allylation reaction, compared
with those of homogeneous acids (see Table 2S, Supporting
Information).
FIGURE 2. The IR spectra of 8a adsorbed on the Al3+-mont (s) and
H-mont (---): enol (O) and keto (×) form of adsorbed 8a.
Both Al3+- and H-mont-catalyzed reactions of 8a with the
ether 10a afforded low yields, ca. 30%, of the benzylated
product 9a for 6 h at 100 °C in the presence of water, in sharp
contrast to the reaction of 8a with 10b.31 These results indicate
that the main reaction path might be direct R-alkylation of a
1,3-dicarbonyl compound with a primary alcohol, which does
not occur via an ether intermediate. Upon treatment with
pyridine, the IR spectrum of the Al3+-mont showed peaks due
to a protonated pyridine and to pyridine adsorbed on the Lewis
acid site. After the treatment of the Al3+-mont with 8a, IR
absorptions assignable to both keto and enol forms of 8a also
were detected (Figure 2).32
Since the peaks due to enol form were stronger relative to
those of the H-mont, the Al site in the Al3+-mont interlayer is
effective at producing the active enol of 8a. A proposed reaction
(30) The concentration of the acid sites on the H-mont surface (6.3 ×
10-3 mmol/m2) is much lager than that on zeolite catalysts such as H-beta
(0.95 × 10-3 mmol/m2) and H-USY (0.75 × 10-3 mmol/m2). These values
were calculated as follows: (concentration of acid site [mmol/m2]) )
(amount of acid site [mmol/g])/(specific surface area [m2/g]).
(31) The H-mont-catalyzed reaction of 8a with ether 10b from the
secondary alcohol of 2g afforded quantitative yield of the R-benzhydryl
acetylacetone.
(32) Alexander, S. M.; Bibby, D. M.; Howe, R. F.; Meinhold, R. H.
Zeolite 1993, 13, 441.
J. Org. Chem, Vol. 72, No. 16, 2007 6013

Motokura et al.
SCHEME 4. Proposed Reaction Pathways for Substitution of Alcohols with 1,3-Dicarbonyl Compounds via Dual Activation by
(A) Brønsted Acid-Brønsted Acid (H-mont) and (B) Brønsted Acid-Lewis Acid (Al3+-mont)
SCHEME 5. A Proposed Reaction Pathway for Allylation of Alcohols with Allylsilane
Conclusions
shown. Use of alcohols instead of halides, acetates, and
carbonates as alkylating reagents eliminated waste byproducts
because it led only to the formation of water. This H-mont as
a heterogeneous catalyst realized easy separation of the catalyst
from the reaction mixture and was recycled without an ap-
preciable loss of activity and selectivity. For the substitution
reaction of primary alcohols with 1,3-dicarbonyl compounds,
the Al3+-exchanged montmorillonite showed high product
selectivity derived from cooperative catalysis of the Lewis and
Brønsted acid sites. The unique acid properties of the monts
with delocalized counter anions of two-dimensional silicate
sheets will allow the development of methods for a variety of
organic transformations.
The Brønsted acid-catalyzed substitution reactions of the
hydroxyl groups of allylic and benzylic alcohols with basic
aniline nucleophiles were demonstrated for the first time.
Interestingly, the H+ site in the H-mont was not neutralized by
the basic nucleophiles because of their weak acid strength.
Furthermore, nucleophilic substitution of alcohols with amides,
indoles, 1,3-dicarbonyl compounds, and allylsilane also was
(33) Nguyen, R.-V.; Li, C.-J. J. Am. Chem. Soc. 2005, 127, 17184.
(34) For activation of 1,3-dicarbonyls by Lewis acidic metal centers,
see: (a) Sasai, H.; Arai, T.; Shibasaki, M. J. Am. Chem. Soc. 1994, 116,
1571. (b) Christoffers, J. Eur. J. Org. Chem. 1998, 1259. (c) Mori, K.;
Oshiba, M.; Hara, T.; Mizugaki, T.; Ebitani, K.; Kaneda, K. Tetrahedron
Lett. 2005, 46, 4283. (d) Mori, K.; Oshiba, M.; Hara, T.; Mizugaki, T.;
Ebitani, K.; Kaneda, K. New J. Chem. 2006, 30, 44.
Experimental Section
1
General. H and 13C NMR spectra were obtained on a JEOL
(35) Formation of triisopropylsilanol was detected by GC-MS analysis
together with 12a in the reaction of 2g and triisopropylallylsilane.
GSX-270 or a JNM-AL400 spectrometer at 270 or 400 MHz in
6014 J. Org. Chem., Vol. 72, No. 16, 2007

Nucleophilic Substitution Reactions of Alcohols
CDCl3 with TMS as an internal standard. Solid state 29Si MAS
NMR spectra (MAS rate ) 6 kHz) were recorded with a
Chemagnetics CMX-300 spectrometer operating at 59.7 MHz.
Repetition time was 20 s (29Si). Polydimethylsilane (29Si: -34.2
ppm) was used as an external standard for the calibration of
chemical shifts. Infrared spectra were obtained with a JASCO FTIR-
410. Analytical GLC and GLC-mass were performed by using a
Shimadzu GC-8A PF with a flame ionization detector equipped
with KOCL 3000T, Silicon SE-30, and OV-17 columns, and a
Shimadzu GCMS QP5000 equipped with ULBON HR-1 column.
Powder X-ray diffraction patterns were recorded with a Philips
X′Pert-MPD with Cu KR radiation. NH3-TPD of the samples was
conducted in a flow-type fixed bed reactor with a Japan BEL TPD-
77 instrument. BET surface area of the catalysts was determined
by N2 adsorption-desorption measurements with a BELSORP
18PLUS-SP analyzer. The identities of products were confirmed
placed Al3+-mont (0.1 g), nitromethane (2 mL), and 8a (3 mmol).
The resulting mixture was stirred vigorously at 60 °C. Then, 2q (2
mmol) was added dropwise into the reaction mixture over 5.5 h.
After 30 min, the catalyst was separated by filtration and GC
analysis of the filtrate showed an 83% yield of 3-(phenylmethyl)-
2,4-pentanedione.
A Typical H-mont-Catalyzed Allylation Reaction of Alcohols
with Allylsilane. Into a reactor were placed H-mont (0.02 g),
n-heptane (2 mL), 11a (1.5 mmol), and 2g (1.0 mmol). The resulting
mixture was stirred vigorously at 60 °C. After 1 h, the catalyst
was separated by filtration and GC analysis of the filtrate showed
a 96% yield of 1,1-diphenyl-3-butene. The recovered H-mont was
washed with ethyl acetate and dried under vacuum, followed by
treatment of the catalyst with aqueous HCl (1.1 wt %) for 10 h at
room temperature. The HCl-treated catalyst was dried under vacuum
before the reuse experiment.
IR Measurement of Pyridine-Adsorbed mont Catalysts. Into
a reactor were placed mont catalyst (0.1 g) and pyridine (1 mmol).
The resulting mixture was stirred at room temperature for 3 h. After
the adsorption of pyridine, the excess pyridine was removed by
evacuating the samples at 150 °C for 12 h. The IR spectra of the
strongly adsorbed pyridine were obtained with use of self-supporting
wafers containing 12 mg of the sample.
1
by comparison with reported IR, MS, and H and 13C NMR data.
Preparation of the H-mont Catalyst. A mixture of parent Na+-
mont (3.0 g) and 200 mL of aqueous HCl (1.1 wt %) was stirred
at 90 °C for 24 h. The slurry obtained was filtered and washed
with 1 L of distilled water to remove chlorine, followed by drying
at 110 °C in air to afford the H-mont as a whitish gray powder.
Elemental analysis: Na, 0.03; Al, 10.1; Fe, 1.34; Mg, 1.73.
Preparation of the Al3+-mont Catalyst. A mixture of parent
Na+-mont (4.2 g) and 200 mL of aqueous AlCl3‚6H2O (3.3 × 10-2
M) was stirred at 50 °C for 24 h. The slurry obtained was filtered
and washed with 1 L of distilled water, followed by drying at 110
°C in air to afford the Al3+-mont as a whitish gray powder.
Elemental analysis: Na, 0.06; Al, 12.9; Fe, 1.50; Mg, 2.04.
A Typical H-mont-Catalyzed Substitution Reaction of Alco-
hols with Anilines. H-mont (0.1 g), n-heptane (2 mL), 1a (1 mmol),
and 2a (2 mmol) were placed into a reactor. The resulting mixture
was stirred vigorously at 80 °C. After 24 h, the catalyst was
separated by filtration and GC analysis of the filtrate showed an
88% combined yield of allylated products, N-(2-cyclohexen-1-yl)-
aniline (3a), 2-(2-cyclohexen-1-yl)aniline (4a), and 4-(2-cyclohexen-
1-yl)aniline (5a). GC analysis revealed a product ratio of 86:10:4.
The filtrate was evaporated and the crude product purified by
column chromatography with use of silica (n-hexane/ethyl acetate
) 9:1) to afford pure products.
Acknowledgment. This investigation was supported by a
Grant-in-Aid for Scientific Research from the Ministry of
Education, Culture, Sports, Science, and Technology of Japan
(16206078, 18360389). This work was also supported by Grant-
in-Aid for Scientific Research on Priority Areas (No.18065016,
“Chemistry of Concerto Catalysis”) from Ministry of Education,
Culture, Sports, Science and Technology, Japan. We are grateful
to Prof. Dr. S. Namba (Teikyo University) for catalyst prepara-
tion and Dr. K. Mori, Dr. Y. Senga, Dr. S. Yamakita (Bel Japan),
Dr. A. Ueda, and Dr. Y. Yamada (AIST) for the TPD
measurements, Dr. M. Doi (Graduate School of Science, Osaka
University) for solid-state NMR studies, and M. Morishita
(Graduate School of Engineering Science, Osaka University)
for the BET measurements. We thank the Center of Excellence
(21COE; program “Creation of Integrated EcoChemistry”,
Osaka University) and the Department of Materials Engineering
Science, Graduate School of Engineering Science, Osaka
University, for scientific support with the gas-hydrate analyzing
system (GHAS). K. Motokura thanks JSPS Research Fellowship
for Young Scientists.
A Typical H-mont-Catalyzed Addition Reaction of 1,3-
Dicarbonyl Compounds to Alcohols. Into a pressure tube were
placed H-mont (0.15 g), n-heptane (2 mL), 8a (1.5 mmol), and 2l
(1.0 mmol). The resulting mixture was stirred vigorously at 100
°C. After 1 h, the catalyst was separated by filtration. Then, the
filtrate was evaporated and the crude product was purified by
column chromatography with use of silica (n-hexane/ethyl acetate
) 9:1) to afford pure 3-(1-phenylethyl)-2,4-pentanedione in 90%
isolated yield. The recovered catalyst was washed with ethyl acetate
and dried under vacuum before the reuse experiment.
Supporting Information Available: Details of experimental
procedures. This material is available free of charge via the Internet
at http://pubs.acs.org.
A Typical Al3+-mont-Catalyzed Addition Reaction of 1,3-
Dicarbonyl Compounds to Primary Alcohols. Into a reactor were
JO070416W
J. Org. Chem, Vol. 72, No. 16, 2007 6015