Benzylation and allylation of naphthols using amberlyst-15

Article abstract of DOI:10.1080/00397910802621715

A simple and efficient method has been developed for benzylation and allylation of naphthols by treatment of the compounds with benzylic and allylic alcohols, respectively, in the presence of amberlyst-15. Several heterogeneous catalysts were screened for

Full text of DOI:10.1080/00397910802621715

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Benzylation and Allylation of
Naphthols Using Amberlyst-15
Biswanath Das a , Boyapati Veeranjaneyulu a ,
Maddeboina Krishnaiah a & P. Balasubramanyam a
a Organic Chemistry Division I , Indian Institute of
Chemical Technology , Hyderabad, India
Published online: 27 Apr 2009.
To cite this article: Biswanath Das , Boyapati Veeranjaneyulu , Maddeboina
Krishnaiah & P. Balasubramanyam (2009) Benzylation and Allylation of Naphthols
Using Amberlyst-15, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 39:11, 1929-1935, DOI:
10.1080/00397910802621715
To link to this article: http://dx.doi.org/10.1080/00397910802621715
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Synthetic Communications1, 39: 1929–1935, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802621715
Benzylation and Allylation of Naphthols
Using Amberlyst-15
Biswanath Das, Boyapati Veeranjaneyulu,
Maddeboina Krishnaiah, and P. Balasubramanyam
Organic Chemistry Division I, Indian Institute of
Chemical Technology, Hyderabad, India
Abstract: A simple and efficient method has been developed for benzylation and
allylation of naphthols by treatment of the compounds with benzylic and allylic
alcohols, respectively, in the presence of amberlyst-15. Several heterogeneous
catalysts were screened for the reaction, and amberlyst-15 was found to be most
effective.
Keywords: Allylation, amberlyst-15, benzylation, heterogeneous catalyst,
naphthols
INTRODUCTION
Naphthol derivatives are important for their interesting biological
properties, including antitubercular activity[1] and inhibitory effects
on cyclooxygenase I and II.[2] Several naphthol compounds are useful
intermediates in organic synthesis.[3,4] In continuation of our work[5]
on development of useful methodologies for synthesis of bioactive
compounds, here we report an efficient method for benzylation and
allylation of naphthols using amberlyst-15 as a heterogeneous catalyst
(Scheme 1).
Received September 17, 2008.
Part 173 in the series, ‘‘Studies on Novel Synthetic Methodologies.’’
Address correspondence to Biswanath Das, Organic Chemistry Division I,
Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007,
Andra Pradesh, India. E-mail: biswanathdas@yahoo.com
1929

1930
B. Das et al.
Scheme 1. Benzylation and allylation of 2-naphthol with amberlyst-15.
RESULTS AND DISCUSSION
Heterogeneous catalysts have gained much attention in recent years as a
result of their interesting activity, low cost, reusability, and ecofriendly
nature. Initially we attempted the benzylation of 2-naphthol with 1-
phenylethanol using various heterogeneous catalysts in 1,2-dichloroethane
under reflux (Table 1).
All the catalysts, except Rh-SiO2 (entry 4), afforded the desired
benzylation product, but amberlyst-15 was found to be most effective.
The reaction was also carried out in different solvents such as MeCN, tet-
rahydrofuran (THF), 1,2-dichloroethane, cyclohexane, and n-heptane,
but considering the reaction time and yield, 1,2-dichloroethane was pre-
ferred. However, at room temperature, the reaction afforded a trace
amount of product even after 24 h. Adjusting the reaction conditions
properly (Scheme 1), a series of benzyl naphthols starting from both
1- and 2-naphthols have been prepared (Table 2).
Table 1. Reaction of 2-naphthol with 1-phenylethanol in the presence of various
catalystsa
Isolated
yield (%)
Entry
Catalyst
NaHSO4-SiO2
HClO4-SiO2
Sulfonic acid functionalized SiO2
Rh-SiO2
BF3-SiO2
1
2
3
4
5
6
7
51
60
63
0
72
76
52
Amberlyst-15
Montmorillonite clay
aA mixture of 2-naphthol (1.2 mmol), 1-phenylethanol (1.0 mmol), and catalyst
(50 mg) was heated under reflux in 1,2-dichloroethane (DCE) for 1 h.

Benzylation and Allylation of Naphthols
1931
Table 2. Benzylation and allylation of naphtholsa
Isolated
yield (%)
Entry
a
Naphthol (1)
Alcohol (2)
Product (3)
76
92
69
82
b
c
d
e
f
79
79
g
72
63
h
i
81
(Continued )

1932
B. Das et al.
Table 2. Continued
Isolated
yield (%)
Entry
j
Naphthol (1)
Alcohol (2)
Product (3)
74
k
79
l
78
1
aThe structures of the products were settled from their spectral (IR, H NMR,
13C NMR, and MS) data.
Cyclic and noncyclic benzylic alcohols have been used for prepara-
tion of these compounds. The yields were high, and conversion was
complete within 1 h. In each case, only the monobenzylation product
was formed. With 1-naphthol, benzylation occurred at C-2, whereas with
2-naphthol if occurred at C-1. The conversion was highly selective as no
O-alkylation product was obtained.
The present method was extended for allylation of both 1- and
2-naphthols (Table 2). In each case, the rearranged allylic compound
was formed. The conversion was complete within 1 h to afford the
derivatives in high yields. The products were characterized from their
1
spectral (IR, H NMR, 13C NMR, and MS) data.
The catalyst, amberlyst-15, works under heterogeneous conditions. It
is less expensive and commercially available. It can be easily recovered
and reused. In the present conversion, the recovered catalyst was used
three times with a minimum variation of the yields of the products.
CONCLUSION
In conclusion, we have developed a convenient and efficient method
for the synthesis of benzyl and allyl naphthols using amberlyst-15 as a

Benzylation and Allylation of Naphthols
1933
reusable heterogeneous catalyst. The method is a simple access for the
preparation of various naphthol derivatives of biological importance.
EXPERIMENTAL
General Procedure for the Synthesis of Benzyl and Allyl Naphthols
A mixture of naphthol (1.2 mmol), benzylic=allylic alcohol (1.0 mmol),
and amberlyst-15 (50 mg) was taken in 1,2-dichloroethane (2 ml) and
heated under reflux. After completion of the reaction (monitored by
thin-layer chromatography, TLC), the solvent was evaporated, and the
reaction mass was diluted with EtOAc. The catalyst was separated by
filtration and washed with EtOAc. The filtrate was evaporated, and the
crude product was subjected to column chromatography (silica gel,
hexane–EtOAc) to obtain the pure product.
The recovered catalyst was subsequently used three times for the
same reaction with little variation of the yields of the products. For exam-
ple, in the reaction of 2-naphthol with 1-phenylethanol (Table 2, entry a)
the yields of the corresponding benzylic naphthol 3a for four consecutive
cycles with the same catalyst were 76, 74, 71, and 68%.
1
The spectroscopic (IR, H NMR, 13C NMR, and MS) data of the
selected compounds are given next.
Spectral Data for Selected Compounds
Compound 3a
1
IR (KBr): 3440, 1645, 1460, 1384 cmꢀ1; H NMR (200 MHz, CDCl3):
d ¼ 8.01 (d, 1H, J ¼ 8.0 Hz), 7.75 (d, 1H, J ¼ 8.0 Hz), 7.61 (d, 1H,
J ¼ 8.0 Hz), 7.46–7.21 (m, 7H), 6.96 (d, 1H, J ¼ 8.0 Hz), 5.12 (q, 1H,
J ¼ 7.0 Hz), 4.72 (s, 1H), 1.74 (d, 3H, J ¼ 7.0 Hz); 13C NMR (50 MHz,
CDCl3): d ¼ 152.6, 140.1, 137.2, 132.8, 132.0, 130.2, 129.3, 128.9, 123.2,
122.8, 119.9, 33.7, 17.8; ESIMS: Mþ1, m=z 249.
Compound 3f
1
IR (KBr): 3470, 1606, 1498, 1255 cmꢀ1; H NMR (200 MHz, CDCl3):
d ¼ 8.06 (d, 1H, J ¼ 8.0 Hz), 7.77 (d, 1H, J ¼ 8.0 Hz), 7.65 (d, 1H,
J ¼ 8.0 Hz), 7.48 (t, 1H, J ¼ 8.0 Hz), 7.31 (t, 1H, J ¼ 8.0 Hz), 6.99 (d,
1H, J ¼ 8.0 Hz), 6.94 (d, 1H, J ¼ 8.0 Hz), 6.71 (d, 1H, J ¼ 2.0 Hz), 6.61

1934
B. Das et al.
(dd, 1H, J ¼ 8.0 Hz & 2.0 Hz), 4.95 (t, 1H, J ¼ 7.0 Hz), 4.78 (s, 1H), 3.72
(s, 3H), 3.06–2.81 (m, 2H), 2.24–1.81 (m, 4H); 13C NMR (50 MHz,
CDCl3): d ¼ 158.9, 152.0, 139.4, 133.3, 130.1, 129.8, 129.0, 128.8, 128.6,
126.8, 123.2, 122.1, 120.0, 114.8, 113.9, 55.2, 36.6, 30.3, 30.1, 22.9;
ESIMS: Mþ1, m=z 305.
Compound 3g
IR (KBr): 3510, 1655, 1600, 1493, 1388 cmꢀ1 1H NMR (200 MHz,
;
CDCl3): d ¼ 8.04 (dd, 1H, J ¼ 8.0 Hz & 2.0 Hz), 7.71 (dd, 1H, J ¼ 8.0 Hz
& 2.0 Hz), 7.48–7.19 (m, 9H), 4.99 (s, 1H), 4.42 (q, 1H, J ¼ 7.0 Hz), 1.72
(d, 3H, J ¼ 7.0 Hz); 13C NMR (50 MHz, CDCl3): d ¼ 148.4, 144.9, 133.6,
129.0, 128.1, 127.5, 127.1, 126.2, 125.8, 125.2, 125.1, 121.2, 120.8, 39.1,
21.1; ESIMS: Mþ1, m=z 249.
Compound 3j
IR (KBr): 3444, 1659, 1598, 1508, 1445, 1382 cmꢀ1; 1H NMR (200 MHz,
CDCl3): d ¼ 8.10 (dd, 1H, J ¼ 8.0 Hz & 2.0 Hz), 7.69 (dd, 1H, J ¼ 8.0 Hz
& 2.0 Hz), 7.48–7.28 (m, 3H), 7.12 (d, 1H, J ¼ 8.0 Hz), 5.62 (s, 1H), 5.39
(t, 1H, J ¼ 7.0 Hz), 3.48 (d, 2H, J ¼ 7.0 Hz), 1.85 (s, 3H), 1.81 (s, 3H); 13
C
NMR (50 MHz, CDCl3): d ¼ 149.9, 135.9, 133.8, 128.2, 128.1, 127.9,
125.1, 125.0, 124.9, 122.0, 121.9, 121.4, 120.0, 119.5, 30.5, 25.8, 18.1;
ESIMS: Mþ1, m=z 213.
Compound 3k
IR (KBr): 3420, 1628, 1514, 1464, 1262 cmꢀ1 1H NMR (200 MHz,
;
CDCl3): d ¼ 7.84 (d, 1H, J ¼ 8.0 Hz), 7.71 (d, 1H, J ¼ 8.0 Hz), 7.58 (d,
1H, J ¼ 8.0 Hz), 7.41 (t, 1H, J ¼ 8.0 Hz), 7.24 (t, 1H, J ¼ 8.0 Hz), 6.99
(d, 1H, J ¼ 8.0 Hz), 5.31–5.18 (m, 2H), 3.71 (d, 2H, J ¼ 7.0 Hz), 1.90 (s,
3H), 1.72 (s, 3H); 13C NMR (50 MHz, CDCl3): d ¼ 151.2, 133.8, 133.2,
129.7, 128.9, 128.2, 126.5, 123.2, 122.3, 119.0, 118.1, 25.8, 24.2, 18.1;
ESIMS: Mþ1, m=z 213.
ACKNOWLEDGMENTS
The authors thank the Council of Scientific and Industrial Research and
the University Grants Commission, New Delhi for financial assistance.

Benzylation and Allylation of Naphthols
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