Highly chemoselective condensation of-naphthol, aldehyde, and urea catalyzed by thiamine hydrochloride

Article abstract of DOI:10.1080/00397911.2010.518278

A three-component condensation reaction involving-naphthol, aldehyde, and urea in the presence of 10mol% thiamine hydrochloride (VB1) as a catalyst is described. Aromatic aldehydes bearing different functional groups exhibited different behavior than-naph

Full text of DOI:10.1080/00397911.2010.518278

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Highly Chemoselective Condensation
of β-Naphthol, Aldehyde, and Urea
Catalyzed by Thiamine Hydrochloride
Min Lei a , Lei Ma a & Lihong Hu a b
a School of Pharmacy, East China University of Science and
Technology, Shanghai, China
b Shanghai Institute of Materia Medica, Chinese Academy of
Sciences, Shanghai, China
Version of record first published: 26 Jul 2011.
To cite this article: Min Lei, Lei Ma & Lihong Hu (2011): Highly Chemoselective Condensation of β-
Naphthol, Aldehyde, and Urea Catalyzed by Thiamine Hydrochloride, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 41:22, 3424-3432
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Synthetic Communications1, 41: 3424–3432, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.518278
HIGHLY CHEMOSELECTIVE CONDENSATION OF
b-NAPHTHOL, ALDEHYDE, AND UREA CATALYZED
BY THIAMINE HYDROCHLORIDE
Min Lei,1 Lei Ma,1 and Lihong Hu1,2
1School of Pharmacy, East China University of Science and Technology,
Shanghai, China
2Shanghai Institute of Materia Medica, Chinese Academy of Sciences,
Shanghai, China
GRAPHICAL ABSTRACT
Abstract A three-component condensation reaction involving b-naphthol, aldehyde, and
urea in the presence of 10 mol% thiamine hydrochloride (VB1) as a catalyst is described.
Aromatic aldehydes bearing different functional groups exhibited different behavior than
b-naphthol and urea under similar reaction conditions. A possible mechanism to account
for the reaction is proposed.
Keywords Catalysis; chemoselective; multicomponent reactions (MCRs); b-naphthol;
thiamine hydrochloride (VB1)
INTRODUCTION
Multicomponent reactions (MCRs) are of considerable importance in organic
and medicinal chemistry because they have proved to be remarkably successful in
generating molecular complexity in a single synthetic operation.[1] Bigenelli,[2]
Ugi,[3] Mannich,[4] and Hantzsch[5] reactions are some examples of classical MCRs.
However, great efforts have been and still are being made to find and develop new
MCRs.
At the beginning of the new century, green chemistry has become a major driv-
ing force for organic chemists to develop environmentally benign routes to a myriad
of materials.[6] Hence, organo-catalysts have received considerable attention in
Received April 8, 2010.
Address correspondence to Lei Ma, School of Pharmacy, East China University of Science and
Technology, 130 Meilong Road, Shanghai 200237, P. R. China and Lihong Hu, Shanghai Institute of
Materia Medica, Chinese Academy of Sciences, Shanghai 201203, P. R. China. E-mail: malei@
ecust.edu.cn; simmhulh@mail.shcnc.ac.cn
3424

NAPHTHOL [1,2-e] [1,3] OXAZINE-3-ONES
3425
Figure 1. Thiamine hydrochloride.
Scheme 1. Three-component condensation of b-naphthol, aldehyde, and urea.
organic synthesis because they have greater efficiency and less toxicity, inexpensive,
they are and metal ions are not retained in the product.
It is well known that thiamine hydrochloride (VB1) is inexpensive, nontoxic,
stable, and recoverable. The structure of VB1 contains a pyrimidine ring and a
thiazole ring linked by a methylene bridge (Fig. 1).
It is reported that the three-component condensation reaction of b-naphthol,
aryl aldehydes, and urea in the presence of Lewis or Brøsted acid catalysts[7] synthe-
sizes [(2-hydroxynaphthalen-1-yl)(aryl)methyl]urea (Scheme 1). As a part of our
program aiming at developing selective and enviromentally friendly methodologies
for MCRs, and in continuation of our interests in VB1- catalyzed organic reactions,
we highlight our findings about highly chemoselective three-component conden-
sation of b-naphthol, aryl aldehydes, and urea. The aim of our work was to extend
the scope of the three-component condensation using VB1 as the catalyst.
RESULTS AND DISCUSSION
Very recently, we reported a simple, efficient, and practical procedure for the
synthesis of amidoalkyl naphthols by a three-component condensation of b-naphthol,
aromatic aldehydes, and amides or urea 3 by using VB1 as a catalyst in alcohol.[8] The
literature revealed that the three-component condensation reaction could take place
under solvent-free conditions (Scheme 1).[7] Therefore, we began to explore the
reaction of b-naphthol 1 (5 mmol), benzaldehyde 2a (5 mmol), and urea 3 (7.5 mmol)
under solvent-free conditions at 150 ꢀC in the presence of 10 mol%
VB1 to determine the efficiency of the catalyst (Scheme 1). Curiously, the product
1,2-dihydro-1-phenylnaphth[1,2-e][1,3]oxazine-3-one 5a, shown in Fig. 2 and con-
firmed by NMR measurements, was obtained in 92% yield, while in contrast the
desired product [(2-hydroxynaphthalen-1-yl)(phenyl)methyl]urea 4a was not obtained
(Scheme 2).
To study the generality of this procedure, a series of aldehydes were selected to
undergo the condensation reaction under solvent-free conditions at 150 ꢀC in the

3426
M. LEI, L. MA, AND L. HU
Figure 2. Structure of 5a.
Scheme 2. The condensation of b-naphthol, aldehyde, and urea.
presence of 10 mol% VB1 (Table 1). As shown in Table 1, in all of the studied exam-
ples, the aromatic aldehydes bearing functional groups, such as -H, -CH3, -OCH3,
and -Cl, could react smoothly to give the corresponding products 5a–5d in excellent
yields (85–94%). However, we obtained the products 6e–6h in good yields (83–92%)
when using the aromatic aldehydes bearing strong electron-withdrawing substituents,
such as -NO2, -CN, and -Cl2, as the starting materials (Scheme 3, Table 1).
The results in Table 1 clearly indicate that the functional groups of the alde-
hydes had significant effects on the reaction products. Based on these observations,
the mixture of b-naphthol 1, urea 3, and 4-methylbenzaldehyde 2b or 4-nitrobenzal-
dehyde 2f was chosen as the model reaction to study the reaction behavior under
different reaction conditions (Table 2). To determine the catalyst’s effects, the
three-component condensation was carried out with other commercially catalysts,
such as TsOH, NH2SO3H, FeCl3, ZnCl2, and MgCl2, which have been applied in
Table 1. Condensation of b-naphthol 1, aryl aldehydes 2, and urea 3a
Entry
Aldehyde 2
Product
Yield (%)b
1
2
3
4
5
6
7
8
C6H5CHO 2a
5a
5b
5c
5d
6e
6f
92
94
88
85
92
90
91
83
4-CH3C6H4CHO 2b
4-CH3OC6H4CHO 2c
4-ClC6H4CHO 2d
3-NO2C6H4CHO 2e
4-NO2C6H4CHO 2f
4-CNC6H4CHO 2g
2,4-Cl2C6H3CHO 2h
6g
6h
aConditions: b-naphthol 1a (5 mmol), aldehyde
(7.5 mmol), VB1 (0.5 mmol), 150 ꢀC for 30 min.
bIsolated yield.
2 (5 mmol), urea 3

NAPHTHOL [1,2-e] [1,3] OXAZINE-3-ONES
3427
Scheme 3. The condensation of b-naphthol, aldehyde, and urea.
related condensations.[7,9] The results summerized in Table 2 indicate that the reac-
tion time was shortest and the yields were greatest when using VB1 as the catalyst.
Moreover, the results indicated that the reaction could afford the product 5b with
different catalysts when using 4-methylbenzaldehyde 2b as the starting material,
whereas only compound 6f was obtained under similar reaction conditions when
using 4-nitrobenzaldehyde 2f as the starting material.
The results summarized in Tables 1 and 2 also revealed that VB1 could catalyze
the reaction of b-naphthol and aromatic aldehydes to synthesize of aryl-14-H-diben-
zo[a,j]xanthenes 6. Hence, several aromatic aldehydes were examined at 150 ꢀC using
10 mol % VB1 as the catalyst to synthesize compound 6 (Table 3).
In all cases studied, the condensation of b-naphthol 1 and aromatic aldehydes 2
proceeded smoothly to give the corresponding dibenzoxanthenes 6 in good yields.
However, the condensation reaction could not take place as indicated by thin-layer
Table 2. Condensation of b-naphthol 1, aldehydes 2b or 2f, and urea 3 under different conditionsa
Entry
Aldehyde 2
Cat. (mol %)
Temp. (ꢀC)
Time
Product
Yield (%)b
1
2
4-CH3C6H4CHO 2b
4-CH3C6H4CHO 2b
4-CH3C6H4CHO 2b
4-CH3C6H4CHO 2b
4-CH3C6H4CHO 2b
4-CH3C6H4CHO 2b
4-NO2C6H4CHO 2f
4-NO2C6H4CHO 2f
4-NO2C6H4CHO 2f
4-NO2C6H4CHO 2f
4-NO2C6H4CHO 2f
4-NO2C6H4CHO 2f
VB1 (10)
TsOH (30)[10]
NH2SO3H (10)
FeCl3 (20)
150
160
150
150
160
160
150
150
150
150
150
150
30 min
1.5 h
1 h
5b
5b
5b
5b
5b
5b
6f
92
60
80
45
35
30
88
76
73
50
30
20
3
4
3 h
5 h
5
ZnCl2 (50)
MgCl2 (50)
VB1 (10)
6
5 h
7
30 min
1.5 h
1 h
8
TsOH (30)
NH2SO3H (10)
FeCl3 (20)
6f
9
6f
10
11
12
3 h
5 h
6f
ZnCl2 (50)
MgCl2 (50)
6f
5 h
6f
aConditions: b-naphthol 1 (5 mmol), aldehyde 2b or 2f (5 mmol), and urea 3 (7.5 mmol).
bIsolated yields.

3428
M. LEI, L. MA, AND L. HU
Table 3. Condensation of b-naphthol 1 and aryl aldehydes 2a
Entry
Aldehyde 2
Product
Yield (%)b
1
2
3
4
5
6
7
8
C6H5CHO 2a
6a
6b
6c
6d
6e
6f
90
90
84
88
92
90
91
83
4-CH3C6H4CHO 2b
4-CH3OC6H4CHO 2c
4-ClC6H4CHO 2d
3-NO2C6H4CHO 2e
4-NO2C6H4CHO 2f
4-CNC6H4CHO 2 g
2,4-Cl2C6H3CHO 2 h
6g
6h
aConditions: b-naphthol 1a (10 mmol), aldehyde 2 (5 mmol), VB1
(0.5 mmol), 150 ꢀC for 30 min.
bIsolated yields.
chromatography (TLC) in EtOH or other sovents, such as MeOH, tetrahydrofuran
(THF), and 1,2-dichloroethane under reflux conditions (Scheme 4).
On the basis of all our experimental results, together with literature
reports,[7,8,10] we have proposed the mechanistic pathway shown in Scheme 5 to
account for the process. Initially, this condensation may proceed via intermediate 7,
formed by the reaction of aldehyde 2 and urea 3 at the action of the proton of VB1.
Then Michael addition of b-naphthol on intermediate 7 leads to the formation of 4,
which eliminates to form products 5. A possible mechanism for the formation of
dibenzoxanthenes 6 also has been proposed in Scheme 5. The reaction of b-naphthol
1 and aromatic aldehydes 2 were reacted in the presence of VB1 to gave ortho-quinone
methides 8. Then conjugate addition between ortho-quinone methides 8 and
b-naphthol 1 furnished the intermediate 9, which upon intermolecular cyclization
and dehydration gave products 6.
In conclusion, we have demonstrated the multicomponent reaction of
b-naphthol, aromatic aldehydes, and urea in the presence of VB1 and have also
studied the condensation of b-naphthol and aromatic aldehydes under similar con-
ditions. Aromatic aldehydes bearing eletron-withdrawing groups exhibited different
behavior than aromatic aldehydes bearing electron-donating groups. Undoubtedly,
these reactions should be useful to design a simple workup procedure for the
synthesis of [(2-hydroxynaphthalen-1-yl)(aryl)methyl]urea 4, 1,2-dihydro-1-aryl-
naphth[1,2-e][1,3]oxazine-3-ones 5, as well as aryl-14-H-dibenzo[a,j]xanthenes 6.
Scheme 4. The condensation of b-naphthol and aldehyde.

NAPHTHOL [1,2-e] [1,3] OXAZINE-3-ONES
3429
Scheme 5. A possible mechanism for the reaction catalyzed by VB1.
EXPERIMENTAL
Reagents and all solvents were analytically pure and were used without further
purification.1H and 13C NMR spectra were recorded on a Varian 400-MHz spec-
trometer at 400 MHz and 100 MHz, respectively with tetramethylsilane (TMS) as
internal standard. Chemical shifts (d) are given in parts per million (ppm) relative
to TMS, with coupling constants (J) in hertz (Hz). Melting points were determined
with a an X-4 apparatus and are uncorrected. Mass spectra were measured with a
Thermo Finnigan LCQ-Advantage instrument.
Compounds 5a–5d
A mixture of b-naphthol 1 (5 mmol), aromatic aldehyde 2a–2d (5 mmol), urea 3
(7.5 mmol), and VB1 (0.5 mmol) was heated to 150 ꢀC under stirring for 30 min. After
cooling, the reaction mixture was washed with cold water and then recrystallized
from EtOAc–hexane (1:3) to afford the pure product 5a–5d.
Compound 5a.[11] White solid, mp 214–216 ꢀC; 1H NMR (400 MHz,
DMSO-d6) d 8.92 (brs, 1H), 7.33–8.00 (m, 11H), 6.22 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) d 149.7, 147.8, 143.1, 130.5, 130.4, 129.1, 129.0, 128.8, 128.1, 127.4,
127.1, 125.4, 123.3, 117.1, 114.2, 54.2; MS (ESI) m=z: 298 ([M þ Na]þ).
Compound 5b.[10] White solid, mp 163–165 ꢀC; 1H NMR (400 MHz,
DMSO-d6) d 8.82 (brs, 1H), 7.11–8.01 (m, 10H), 6.14 (s, 1H), 2.20 (s, 3H); 13C
NMR (100 MHz, DMSO-d6) d 149.8, 147.8, 140.5, 137.8, 130.9, 130.6, 129.9,

3430
M. LEI, L. MA, AND L. HU
129.4, 129.1, 127.8, 127.3, 125.5, 123.6, 117.3, 114.6, 54.0, 21.1; MS (ESI) m=z: 312
([M þ Na]þ).
Compound 5c.[10] White solid, mp 184–186 ꢀC; 1H NMR (400 MHz, CDCl3)
d 7.77–7.85 (m, 2H), 7.49–7.56 (m, 1H), 7.35–7.41 (m, 2H), 7.30 (d, J ¼ 8.8 Hz, 1H),
7.16 (d, J ¼ 8.4 Hz, 2H), 6.78 (d, J ¼ 8.4 Hz, 2H), 6.62 (brs, 1H), 6.01 (brs, 1H), 3.70
(s, 3H); 13C NMR (100 MHz, CDCl3) d 154.9, 145.6, 142.8, 129.3, 126.3, 125.7,
124.6, 124.0, 123.5, 122.6, 120.4, 118.1, 112.3, 109.9, 108.0, 50.8, 50.5; MS (ESI)
m=z: 328 ([M þ Na]þ).
Compound 5d.[11] White solid, mp 203–206 ꢀC; 1H NMR (400 MHz,
DMSO-d6) d 8.90 (brs, 1H), 7.35–8.05 (m, 10H), 6.24 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) d 149.7, 147.9, 142.1, 133.0, 130.6, 129.3, 129.2, 129.1, 129.0, 128.0,
127.7, 125.6, 123.3, 117.2, 114.0, 53.4; MS (ESI) m=z: 332, 334 ([M þ Na]þ).
Compounds 6a–6h
A mixture of b-naphthol 1 (10 mmol), aromatic aldehyde 2a–2h (5 mmol), and
VB1 (0.5 mmol) was heated to 150 ꢀC under stirring for 30 min. After cooling, the
reaction mixture was washed with cold water and then recrystallized from EtOH
to afford the pure product 6a–6 h.
Compound 6a.[12] White solid, mp 182–184 ꢀC; 1H NMR (400 MHz, CDCl3)
d 8.35 (d, J ¼ 8.4 Hz, 2H), 7.73–7.80 (m, 4H), 7.33–7.60 (m, 8H), 7.10 (t, J ¼ 7.2 Hz,
2H), 6.94 (t, J ¼ 7.2 Hz, 1H), 6.44 (s, 1H); 13C NMR (100 MHz, CDCl3) d 148.8,
145.1, 131.4, 131.1, 128.9, 128.8, 128.5, 128.3, 126.8, 126.4, 124.2, 123.0, 122.6,
118.1, 117.3, 38.1; MS (EI) m=z: 358 (Mþ).
Compound 6b.[12] White solid, mp 227–229 ꢀC; 1H NMR (400 MHz, CDCl3)
d 8.35 (d, J ¼ 8.4 Hz, 2H), 7.45–7.80 (m, 4H), 7.25–7.35 (m, 8H), 6.94 (d, J ¼ 7.8 Hz,
2H), 6.44 (s, 1H), 2.11 (s, 3H); 13C NMR (100 MHz, CDCl3) d 148.8, 141.2, 135.9,
131.6, 131.1, 129.3, 128.8, 128.2, 126.9, 124.3, 122.7, 118.0, 117.4, 109.5, 37.6,
21.0; MS (EI) m=z: 372 (Mþ).
Compound 6c.[12] White solid, mp 202–204 ꢀC; 1H NMR (400 MHz, CDCl3)
d 8.35 (d, J ¼ 8.4 Hz, 2H), 7.70–7.80 (m, 4H), 7.31–7.55 (m, 8H), 6.62 (d, J ¼ 8.4 Hz,
2H), 6.41 (s, 1H), 3.57 (s, 3H); 13C NMR (100 MHz, CDCl3) d 157.8, 148.7, 137.3,
131.4, 131.1, 129.2, 128.8, 128.7, 126.8, 124.2, 122.7, 117.9, 117.4, 113.8, 55.1,
37.0; MS (EI) m=z: 388 (Mþ).
Compound 6d.[12] White solid, mp 286–289 ꢀC; 1H NMR (400 MHz, CDCl3)
d 8.34 (d, J ¼ 8.4 Hz, 2H), 7.75–7.85 (m, 4H), 7.42–7.61 (m, 8H), 7.14 (d, J ¼ 8.0 Hz,
2H), 6.65 (s, 1H); 13C NMR (100 MHz, CDCl3) d 148.4, 144.9, 131.3, 131.2, 131.1,
130.1, 129.6, 129.1, 128.7, 127.4, 125.0, 123.7, 118.1, 117.3, 39.7; MS (EI) m=z: 392
(Mþ).
Compound 6e.[12] Yellow solid, mp 207–211 ꢀC; 1H NMR (400 MHz,
CDCl3) d 8.40 (s, 1H), 8.27 (d, J ¼ 8.4 Hz, 2H), 7.76–7.83 (m, 6H), 7.57 (t, J ¼ 7.6 Hz,
Hz, 2H), 7.48 (d, J ¼ 8.4 Hz, 2H), 7.41 (t, J ¼ 7.2 Hz, 2H), 7.22 (t, J ¼ 7.6 Hz, 1H),
6.55 (s, 1H); 13C NMR (100 MHz, CDCl3) d 149.0, 148.3, 147.2, 134.3, 131.3,

NAPHTHOL [1,2-e] [1,3] OXAZINE-3-ONES
3431
131.2, 129.8, 129.6, 129.2, 127.4, 124.8, 123.0, 122.1, 121.8, 118.3, 116.2, 37.7; MS
(EI) m=z: 403 (Mþ).
Compound 6f.[12] Yellow solid, mp > 300 ꢀC; 1H NMR (400 MHz, CDCl3) d
8.71 (s, 1H), 7.96–8.10 (m, 8H), 7.45–7.70 (m, 6H), 6.92 (s, 1H); 13C NMR
(100 MHz, CDCl3) d 152.5, 148.0, 145.8, 130.7, 130.5, 129.5, 128.6, 128.7, 127.1,
124.5, 123.5, 123.0, 117.6, 116.1, 36.3; MS (EI) m=z: 403 (Mþ).
1
Compound 6g.[13] White solid, mp > 300 ꢀC; H NMR (400 MHz, CDCl3) d
8.27 (d, J ¼ 8.8 Hz, 2H), 7.40–7.80 (m, 14H), 6.53 (s, 1H);13C NMR (100 MHz,
CDCl3) d 150.1, 148.8, 132.5, 131.1, 129.6, 129.2, 123.0, 127.3, 124.6, 122.2, 122.1,
118.1, 116.0, 110.4, 38.1; MS (EI) m=z: 383 (Mþ).
Compound 6h.[13] White solid, mp 248–250 ꢀC; 1H NMR (400 MHz, CDCl3)
d 8.63 (d, J ¼ 8.4 Hz, 2H), 7.80 (d, J ¼ 8.4 Hz, 2H), 7.76 (d, J ¼ 8.8 Hz, 2H), 7.60 (t,
J ¼ 7.0 Hz, 2H), 7.38–7.47 (m, 4H), 7.22–7.27 (m, 2H), 6.87 (d, J ¼ 8.4 Hz, 1H), 6.74
(s, 1H); 13C NMR (100 MHz, CDCl3) d 148.9, 142.3, 132.8, 132.7, 131.6, 130.8,
130.5, 129.3, 129.1, 128.7, 128.3, 126.9, 124.4, 123.0, 118.0, 117.4, 34.2; MS (EI)
m=z: 426 (Mþ).
ACKNOWLEDGMENTS
This work was supported by the Chinese National Science and Technology
Major Project ‘‘Key New Drug Creation and Manufacturing Program’’ (Grants
2009ZX09301-001 and 2009ZX09102), the Chinese National High-Tech Research
and Developed Program (Grant 2007AA02Z147), the National Natural Science
Foundation of China (Grants 90713046, 30772638, and 30925040), and the CAS
Foundation (Grant KSCX2-YW-R-179).
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