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N. Mameda et al. / Catalysis Communications 61 (2015) 41–43
carbinolamides using zeolites in aqueous media. However, to the best of
our knowledge, hitherto there have been no reports for the synthesis of
N,N′-methylenebisamides and carbinolamides using zeolites in aqueous
media.
get the highest yield for this reaction are 2:1 mole ratio of benzamide
to formaldehyde in water (10 ml) at reflux temperature (100 °C) over
Hβ catalyst (150 mg).
To explore the scope of the present system under the optimized con-
ditions, a variety of aromatic amides reacted with formaldehyde in the
presence of Hβ zeolite, afforded low to excellent yields of the corre-
sponding N,N′-methylenebisamide products (Table 2). In order to de-
termine the influence of substitution on the aromatic ring of
benzamide with this reagent system, we have carried out the reaction
with different substituted benzamides. Highly activating or moderately
activating groups present on aromatic ring of benzamide gave excellent
yields of the respective N,N′-methylenebisamides (Table 2, entries 2–6).
Deactivating groups present on aromatic ring of benzamides also ren-
dered high yields (in exception nitro substituted benzamide) (Table 2,
entries 7–11). However, nitro substituted benzamide provided
lower yields (Table 2, entries 12 and 13). Five-membered heteroaryl
amide i.e. thiophene-2-carboxamide yielded the respective N,N′-
methylenebisamide product with 90% yield (Table 2, entry 14).
Cinnamamide also reacted smoothly and gave the corresponding N,N′-
methylenebisamide in 87% yield (Table 2, entry 15).
Interestingly, N-(hydroxymethyl)benzamide product was obtained
selectively when the reaction was performed in the presence of NaY ze-
olite. Stimulated by the affirmative preliminary results, we considered
to develop a simple methodology for the synthesis of carbinolamides.
Next, our efforts were focused on achieving the highest yield, then we
investigated the reaction of benzamide (1a) (2 mmol) with different
mole ratios of formaldehyde using NaY zeolite (100 mg) in water at
100 °C for 6 h (Table 3) and observed that 10 mmol of formaldehyde
provided the highest yield (Table 3, entry 6). While increasing the
amount of catalyst (150 mg) the yield of the desired product was in-
creased from 86% to 96% and the reaction time was also reduced
(Table 3, entry 7). In the absence of a catalyst yield the desired product
was only 16% (Table 3, entry 8) and this observation clearly indicates
the influence of the catalyst on the reaction. The above-presented
results show that the optimized reaction conditions to get the
highest yield for this reaction are 1:5 mole ratio of benzamide to form-
aldehyde in water (10 ml) at 100 °C over NaY zeolite (150 mg) (Table 1,
entry 7).
Initially, we investigated the reaction of benzamide (2 mmol) (1a)
with formaldehyde (1 mmol) as a model system to optimize the
different parameters of the reaction (Table 1). In order to choose the
best catalyst first, the reaction was carried out over various zeolites,
MCM-41 and montmorillonite K10 in water at 100 °C for 12 h and the
results are summarized in Table 1. Among the catalysts examined, Hβ
zeolite has exhibited the best catalytic activity due to its higher
acidity and large pore size, which furnished the corresponding
methylenebisbenzamide in excellent yield (Table 1, entry 8). Under
the similar reaction conditions, HY, H-mordenite and HZSM-5 (40) pro-
vided the corresponding methylenebisbenamides in b40% yield, along
with substantial amounts of the N-(hydroxymethyl)benzamides
(b40% yield) (Table 1, entries 1, 3 and 7). MCM-41 and montmorillonite
K10 produced the N-(hydroxymethyl)benzamide as a major product
(b40%) (Table 1, entries 4 and 5), along with small amounts of the re-
spective methylenebisbenzamide (b10%). Whereas, NaY has given se-
lectively N-(hydroxymethyl)benzamide product in 46% yield (Table 1,
entry 2).
Once Hβ catalyst was found as the best catalyst for the formation of
N,N′-methylenebisbenzamide, further we have studied the effect of
mole ratio of benzamide to formaldehyde from 2:1 to 2:2 under the sim-
ilar reaction conditions and it did not have any significant effect on the
product yield (Table 1, entries 9 and 10). The present reaction was also
conducted with different amounts of catalyst and it was found that both
150 mg and 200 mg of catalyst gave the best results within 6 h (Table 1,
entries 12 and 13). Next, the reaction was carried out over Hβ with dif-
ferent Si/Al ratios and observed that there was no considerable effect on
the product yield (Table 1, entries 14 and 15). In the absence of catalyst
desired product (N,N′-methylenebisbenzamide) was not observed, but
N-(hydroxymethyl)benzamide obtained in 29% yield. As can be seen
from the above obtained results, the optimized reaction conditions to
Table 1
Optimization for synthesis of N,N′-methylenebisbenzamide.
Table 2
Synthesis of N,N′-methylenebisamides using Hβ zeolite.
Entry
Catalyst
Yield (%)a
2a
2b
1
2
3
4
5
6
7
8
HY
NaY
28
46
34
38
20
32
37
4
4
4
29
–
35
–
Entry
R
Yielda (%)
H-Mordenite
Montmorillonite K10
HMCM-41
24
6
2
1
2
3
4
5
6
7
8
Ph
96b
83
91
79
94
93
94
93
90
82
96
23
10
90
87
3-MeOC6H4
4-MeOC6H4
2-MeC6H4
3-MeC6H4
4-MeC6H4
2-FC6H4
2-ClC6H4
4-BrC6H4
3-CF3C6H4
4-CF3C6H4
3-NO2C6H4
4-NO2C6H4
2-C4H3S
HZSM-5 (300)
HZSM-5 (40)
Hβ (Si/Al = 19)
Hβ (Si/Al = 19)
Hβ (Si/Al = 19)
Absence of catalyst
Hβ (Si/Al = 19)
Hβ (Si/Al = 19)
Hβ (Si/Al = 15)
Hβ (Si/Al = 20)
16
37
94
94b
94c
–
96d
96e
96d
94d
9
10
11
12
13
14
15
9
–
10
11
12
13
14
15
Reaction conditions: 1a (2 mmol), aqueous formaldehyde (37%, 1 mmol), catalyst (100 mg),
H2O (10 ml), 100 °C, 12 h.
PhCH = CH
a
Isolated yields.
Aqueous formaldehyde (37%, 1.5 mmol).
Aqueous formaldehyde (37%, 2 mmol).
Hβ (150 mg), 6 h.
b
Reaction conditions: Amide (2 mmol), aqueous formaldehyde (37%, 1 mmol), Hβ zeolite
c
(150 mg), H2O (10 ml), 100 °C, 24 h.
d
a
Isolated yields.
6 h.
e
b
Hβ (200 mg), 6 h.