Lewis acid catalyzed synthesis of 1-aryl-1,2-dihydro-naphtho[1,2-e][1,3] oxazin-3-ones under solvent free conditions: A mechanistic approach

Article abstract of DOI:10.1002/jhet.825

Lewis acids catalyzed highly efficient one-pot three component coupling of β-naphthol, benzaldehydes and urea to produce 1-aryl-1,2-dihydro-naphtho[1, 2-e][1,3]oxazin-3-one derivatives under solvent free conditions is described. Mechanistic studies confir

Full text of DOI:10.1002/jhet.825

May 2012
Lewis Acid Catalyzed Synthesis of 1-Aryl-1,2-dihydro-
naphtho[1,2-e][1,3]oxazin-3-ones under Solvent Free
Conditions: A Mechanistic Approach
589
*
Mukul Sharma, Sunny Manohar, and Diwan S. Rawat
Department of Chemistry, University of Delhi, Delhi 110007, India
*
E-mail: dsrawat@chemistry.du.ac.in
Received October 28, 2010
DOI 10.1002/jhet.825
View this article online at wileyonlinelibrary.com.
H
N
HO
O
Ph
O
Ph
O
H2N
NH2
+
O
I2
I2
O
90-100 oC
140-150 oC
Ph
H
No catalyst
No Reaction
Lewis acids catalyzed highly efficient one-pot three component coupling of b-naphthol, benzaldehydes
and urea to produce 1-aryl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-one derivatives under solvent free con-
ditions is described. Mechanistic studies confirmed that product formation is possible only at very high tem-
perature (140–150ꢀC) and at lower temperature (90–100ꢀC) formation of 14-aryl-14H-dibenzo(a,j)xanthenes
was observed. Among the nine Lewis acids screened, iodine, P2O5 and Yb(OTf)3 are found to be most ef-
fective catalyst for this multicomponent reaction.
J. Heterocyclic Chem., 49, 589 (2012).
INTRODUCTION
To our best knowledge, there are only few methods avail-
able for the synthesis of substituted 1-aryl-1,2-dihydro-
naphtho[1,2-e][1,3]oxazin-3-ones, which involves either
toxic chemicals [10–12] or long reaction time [13]. Hence,
there is still scope for the development of milder, safer,
economical, and more efficient synthetic protocols for the
preparation of aromatic-fused oxazinones. The develop-
ment of mild, low cost, high performance acid catalyst,
and replacement of toxic volatile organic solvents as
reaction media with nontoxic solvents or reaction under
solvent free conditions have been the area of active research
in recent years. Inspired by catalytic applications of molec-
ular iodine [14–16], boric acid [17–20], sulfamic acid [21],
FeCl3 [22], SnCl2 [23], InCl3 [24], and Yb(OTf)3 [25] in the
organic transformation, we decided to compare catalytic po-
tential of these Lewis acids in the synthesis of aromatic-fused
1-aryl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-one derivatives
and study their mechanism. Development of a reaction that uses
catalytic amounts of mild, nontoxic and readily available
reagent should greatly contribute to the creation of environmen-
tally benign processes.
Aromatic-fused oxazinone derivatives belong to relatively
small class of heterocycles, but this skeleton has recently
been found to be the central part in several antitumor, allergic
asthma [1] and antibiotic [2] compounds. Linezolide-based
antibiotics and maytansine are important heterocycles that
comprises 1,3-oxazinan-2-ones as active pharmacophore
[3–5]. 1,3-Oxazinan-2-ones derivatives exhibit a variety of
biological activities, and they are being explored as antiinfla-
matory agents and as agents for treating ulcers, allergies,
arthritis, and diabetes [5]. Some 6-phenyl-1,3-oxazinan-2-
ones have phosphodiesterase IV inhibitory effects and have
been shown to be remedies for inflammatory diseases and
antiasthmatics. The six membered 1,3-oxazinan-2-ones are
not used as extensively as homologues of 2-oxazolidinones.
This is probably due to the difficulties in synthesizing chiral
1,3-oxazinan-2-ones. Apart from their medicinal properties
1,3-oxazinan-2-ones and their analogs were also used as ami-
nopropylation agents [6], as intermediates for the preparation
of amino alcohols [7] and as a precursor in the synthesis of
phosphinic ligands for the asymmetric catalysis [8,9]. In spite
of huge potential, there have been very few synthetic methods
reported for their preparation and condensation of amino
alkylnaphthols with phosgene or carbonyl diimidazoles in
presence of triethyl amine have been the most widely used
methods for their preparation.
RESULT AND DISCUSSION
Because of several advantages of molecular iodine as a
catalyst, initially reaction was performed by the condensation
© 2012 HeteroCorporation

590
M. Sharma, S. Manohar, and D. S. Rawat
Vol 49
Scheme 1. Direction of product formation in iodine catalyzed MCRs.
of b-naphthols, benzaldehyde and urea in presence of 10 mol
% iodine on a preheated hot plate at 140–150ꢀC, and the reac-
tion yielded 80% desired product within 5 min. To establish
the role of catalytic amount of iodine, reaction was carried
out in presence of variable amount of iodine, and it was
observed that reaction can be carried out even in presence of
5 mol % of iodine without compromising yield and reaction
time. To reduce the temperature of reaction, we carried out
same reaction using higher catalytic amount of iodine at
90–100ꢀC but interestingly, we observed the formation of
14-phenyl-14H-dibenzo[a,j]xanthene (2d) [25] (Scheme 1)
in low yield. Plausible mechanism for the formation of com-
pounds 1 and 2 is shown in Scheme 2. It is evident by mech-
anism that there are two different key intermediates 3 and 4
that lead the reaction to yield in different products at different
temperature. Formation of 4 over 3 at relatively low tempera-
ture is reasonable because at lower temperature formation of 3
is kinetically not favored. To further confirm the presence of
compound 3 as an intermediate in this reaction, we synthe-
sized compound 3 by literature method [26] (Scheme 3). To
confirm the involvement of intermediate 3, in this transforma-
tion, reaction of compound 3 with one mole of b-naphthol in
presence of catalytic amount of iodine at 140–150ꢀC was
carried out, and desired compound was isolated in very good
yield (Scheme 3). This confirms the involvement of intermedi-
ate 3, which is formed only at 140–150ꢀC and Lewis acid
catalyst is required for this reaction.
Encouraged by this observation, series of benzaldehydes
having electron withdrawing, electron donating and neutral
functionality at different position of the aromatic ring were
reacted with b-naphthols, and urea in presence of catalytic
amount of iodine. In all of the cases, product was isolated
in 50–95% yield and reaction completes within 5 min
(Table 1). When temperature was dropped to 90–100ꢀC,
formation of aryl-14H-dibenzo(a,j)xanthenes was observed
and this class of compounds have been prepared via two
component condensation of b-naphthol and substituted
benzaldehydes at 90–100ꢀC. Existence of intermediate 5
has been reported in this multicomponent synthesis [25].
In the present investigation we believe, urea does not react
with substituted benzaldehydes at 90–100ꢀC due to the fact
that lone pair electrons of nitrogen are not available for
nucleophilic attack at this temperature due to resonance stabi-
lized structure of urea [27], rather substituted benzaldehydes
reacts with b-naphthol which leads to the formation of inter-
mediate 5 via 4 and subsequently leads the formation of com-
pound 2 [25]. This study confirmed the involvement of two
different intermediates (3 and 4) in this reaction resulting in
the formation of two different products at different tempera-
ture. Compound 2 was isolated in very good yield when two
mole of b-naphthol was used instead of one mole.2
Next, we turned our attention to compare catalytic activ-
ity of range of Lewis acids, and reaction was carried out
with selected benzaldehydes. Different Lewis acids such
as boric acid, P2O5, sulfamic acid, FeCl3, SnCl2, InCl3,
Pb(OAc)4 and Yb(OTf)3 were explored and it was found
that iodine, P2O5 and Yb(OTf)3 are the best catalyst in term
of yield of the desired product. It is important to mention
here that this is the best reaction condition for the synthesis
of 1,2-dihydro-1-aryl-naphtho[1,2-e]oxazine-3-ones in term
of yield and reaction time. Under the identical reaction condi-
tions, thiourea instead of urea did not yield any product while
use of aliphatic aldehydes gave poor yield of the products,
possibly due to lower boiling points of aliphatic aldehydes.
EXPERIMENTAL
All of the chemicals used in the synthesis were purchased from
Sigma-Aldrich and were used as such. Progress of reaction was
monitored by pre-coated Merck silica gel TLC 60F254 and the
spots were detected either by UV or by charring in iodine.
Solvents were distilled before use. Melting points were deter-
mined on a melting point apparatus and are uncorrected. IR
(KBr) spectra were recorded using Perkin-Elmer model 2000
FT-IR spectrophotometer and the values are expressed as
nmax cmÀ1. Mass spectral data were recorded on a Jeol (Japan)
JMS-DX303 and micromass LCT, Mass Spectrometer/Data sys-
1
tem. The H NMR spectra were recorded on Bruker Spectrospin
spectrometer at 300 MHz, Jeol Spectrospin spectrometer at 400
MHz and 13C NMR 75.5 MHz, and 100 MHz respectively
using TMS as an internal standard. The chemical shift values
are recorded on d scale and the coupling constants (J) are in Hz.
Experimental procedure.
A mixture of benzaldehyde
(6.02 mmol), b-naphthol (6.02 mmol), and urea (9.03 mmol)
were taken into a 50-mL round bottom flask and stirred at
140–150ꢀC until the reaction mixture became homogeneous, to this
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

May 2012
Lewis Acid Catalyzed Synthesis of 1-Aryl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-ones
under Solvent Free Conditions: A Mechanistic Approach
591
Scheme 2. Proposed mechanism.
reaction mixture iodine (0.3 mmol) was added quickly and the
progress of reaction was monitored by thin layer chromatography
and reaction takes 5 min to complete. After completion, reaction
mixture was allowed to cool at room temperature and quenched by
cold water. The aqueous layer was extracted with chloroform, and
reaction mixture was dried over anhydrous Na2SO4. The crude
product was purified by crystallization to yield the pure compound
and characterized by spectroscopic techniques.
with the data reported in literature. The spectral data for new
compounds are described below.
1-(3-Nitro-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-
one (1b).
Yield: 70%; mp: 260–262ꢀC; IR (Nujol, cmÀ1):
3238, 3136, 1760, 1696, 1532, 1345, 1224, 1177; 1H NMR
(300 MHz, DMSO-d6): 6.45 (d, J = 2.7 Hz, 1H, PhCH), 7.39–7.51
(m, 3H), 7.60–7.66 (m, 2H), 7.94–8.14 (m, 4H), 8.26 (d, J = 6.6
Hz, 1H), 9.00 (s, 1H); 13C NMR (75.5 MHz, DMSO-d6): 52.77,
112.88, 116.89, 121.88, 122.96, 123.07, 125.25, 127.61, 128.69,
130.40, 130.72, 133.44, 144.66, 147.68, 147.93, 149.02; ESI-
HRMS calculated for C18H12N2O4: 320.0797. Found: 320.0796 (M+).
1-(4-Fluoro-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-
The products 1a, 1c, 1d, 1g, and 1i were previously reported
[10] and the spectral data of these products were in agreement
3-one (1e).
Yield: 87%; mp: 200ꢀC; IR (KBr, cmÀ1): 3220,
1
Scheme 3. Involvement of intermediate (3) in the formation of 1.
3134, 2958, 1751, 1603, 1508, 1398, 1224, 743; H NMR (300
MHz, DMSO-d6): 6.21 (d, J = 2.4 Hz, 1H, PhCH), 7.10–7.16
(m, 2H), 7.30–7.49 (m, 4H), 7.76 (d, J = 8.1 Hz, 1H), 7.92–7.99
(m, 2H), 8.28 (s, 1H), 8.83 (s, 1H); 13C NMR (75.5 MHz,
DMSO-d6): 52.94, 113.78, 115.56, 115.85, 116.83, 123.01,
125.06, 127.36, 128.60, 129.01, 129.12, 130.29, 130.38, 139.07,
147.37, 149.20, 159.93, 163.17; ESI-HRMS calculated for
C18H12FNO2: 293.0852. Found: 293.0849 (M+).
Journal of Heterocyclic Chemistry
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M. Sharma, S. Manohar, and D. S. Rawat
Vol 49
Table 1
One-pot iodine-catalyzed synthesis of 1-aryl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-ones.
Entry
Benzaldehyde
Product
Reaction Temp
Yield (%)
80
Mp (ꢀC)
1j
140–150
220–221[10]
1b
1c
1d
1e
1f
140–150
140–150
140–150
140–150
140–150
140–150
140–150
140–150
140–150
140–150
70
93
74
87
95
94
89
88
66
82
260–262
203–208[10]
220–222[10]
200
250–253
188–190[10]
246–248
170[10]
1g
1h
1i
1j
227–230
200
1k
1l
140–150
86
220–223
(Continued)
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Lewis Acid Catalyzed Synthesis of 1-Aryl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-ones
under Solvent Free Conditions: A Mechanistic Approach
593
Table 1
(Continued)
Entry
Benzaldehyde
Product
Reaction Temp
Yield (%)
92
Mp (ꢀC)
256
1m
140–150
1n
1o
140–150
140–150
95
86
241–243
210–213
1p
1q
2a
140–150
140–150
90–100
93
50
69
260–261
250–253
294–296[28,29]
2b
2c
90–100
90–100
77
84
201–204[29,30]
237–240[29,30]
2d
90–100
69
226–228[29,31]
1-(3-Fluoro-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]
oxazin-3-one (1f).
Yield: 95%; mp: 250–253ꢀC; IR (Nujol,
1-(2-Chloro-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]
oxazin-3-one (1h).
Yield: 89%; mp: 246–248ꢀC; IR (Nujol,
cmÀ1): 3134, 1730, 1224, 796; 1H NMR (300 MHz, DMSO-d6):
6.23 (d, J = 2.1 Hz, 1H, PhCH), 7.03–7.49 (m, 7H), 7.79 (d, J =
7.8 Hz, 1H), 7.93–8.00 (m, 2H), 8.90 (s, 1H); 13C NMR
(75.5 MHz, DMSO-d6): 53.12, 113.38, 113.83, 114.12, 114.72,
116.85, 122.82, 123.00, 125.13, 127.46, 128.62, 128.80,
130.37, 131.04, 145.42, 147.50, 149.18, 160.51, 163.75; ESI-
HRMS calculated for C18H12FNO2: 293.0852. Found:
293.0850 (M+).
cmÀ1): 3233, 3139, 1723, 1226, 1123, 761, 747; H NMR (300
MHz, DMSO-d6): 6.42 (d, J = 2.4 Hz, 1H, PhCH), 7.09–7.50
(m, 8H), 7.85–7.94 (m, 2H), 8.72 (s, 1H); ESI-HRMS calculated for
C18H12ClNO2: 309.0557. Found: 309.0551 (M+), 311.3196 (M++2).
1-(3-Chloro-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-
1
one (1j).
Yield: 66%; mp: 227–230ꢀC; IR (KBr, cmÀ1): 3144,
1
2957, 1752, 1224, 1179; H NMR (300 MHz, DMSO-d6): 6.23 (s,
1H, PhCH), 7.14–7.52 (m, 7H), 7.74–781 (m, 1H), 7.93–8.01(m, 2H),
Journal of Heterocyclic Chemistry
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M. Sharma, S. Manohar, and D. S. Rawat
Vol 49
Table 2
1-(2-Trifluoromethyl-phenyl)-1,2-dihydro-naphtho[1,2-e]
[1,3]oxazin-3-one (1p).
Yield: 93%; mp: 260–261ꢀC; IR
Effect of different Lewis acid catalysts on yield.
(KBr, cmÀ1): 3226, 3140, 1723, 1394, 1224, 1118, 754; H NMR
(300 MHz, DMSO-d6): 6.33 (s, 1H, PhCH), 6.77 (d, J = 7.5 Hz,
1H), 7.04 (t, J = 7.2 Hz, 1H), 7.13 (t, J = 7.2 Hz, 1H), 7.24
(d, J = 7.5 Hz, 1H), 7.35–7.42 (m, 4H), 7.91–8.00 (m, 2H),
8.70 (s, 1H); 13C NMR (75.5 MHz, DMSO-d6): 56.04, 118.90,
121.95, 127.92, 130.25, 132.11, 132.27, 132.66, 133.23,
133.88, 134.07, 135.48, 135.66, 136.22, 140.42, 145.76,
153.08, 154.24; ESI-HRMS calculated for C19H15NO2:
343.0820. Found: 343.0819 (M+).
1
Yield (%)
Catalyst
Iodine
Boric acid
Sulphamic
acid
SnCl2
FeCl3
InCl2
Yb(OTf)3
P2O5
Entry 1a
Entry 1b
Entry 1c
Entry 1g
80
59
36
70
48
31
93
31
41
82
41
38
30
34
40
71
82
46
32
25
44
68
75
49
35
32
38
79
89
42
39
30
41
72
86
39
1-(2,4-Dichloro-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]
oxazin- 3-one (1q).
Yield: 50%; mp: 250–253ꢀC; IR (KBr,
1
cmÀ1): 3255, 3246, 3143, 1737, 1392, 1226, 839, 742; H NMR
(300 MHz, DMSO-d6): 6.48 (s, 1H, PhCH), 7.18–7.48 (m, 6H),
7.66 (s, 1H), 7.92–8.01 (m, 2H), 8.89 (s, 1H); ESI-HRMS
calculated for C18H11Cl2NO2: 343.0167. Found: 343.0168 (M+),
345.0174 (M++2), 347.0171 (M++4).
Pb(OAc)4
8.87(s, 1H); ESI-HRMS calculated for C18H12ClNO2: 309.0557.
Found: 309.0554 (M+), 311.0548 (M++2).
Acknowledgments. DSR thanks Department of Science and
Technology (SR/S1/OC-08/2008), New Delhi, India and University
of Delhi, Delhi, India for financial support. MS and SM are
thankful to CSIR for the award of senior research fellowship.
Authors are thankful to CIF-USIC, University of Delhi, Delhi for
NMR spectral data.
1-(3,4-Dimethoxy-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]
oxazin-3-one (1k):.
Yield: 82%; mp: 200ꢀC; IR (Nujol, cmÀ1):
1
3149, 3033, 2924, 2854, 1736, 1516, 1221; H NMR (300 MHz,
DMSO-d6): 3.65 (s, 3H, OCH3), 3.69 (s, 3H, OCH3), 6.10 (d, J =
2.7 Hz, 1H, PhCH), 6.58 (d, J = 8.4 Hz, 1H), 6.80 (d, J = 8.4 Hz,
1H), 7.04 (s, 1H), 7.33–7.49 (m, 3H), 7.78 (d, J = 8.1 Hz, 1H),
7.91–7.98 (m, 2H), 8.73 (s, 1H); 13C NMR (75.5 MHz, DMSO-d6):
53.45, 55.41, 55.45, 111.07, 111.88, 114.03, 116.77, 118.74,
123.20, 124.99, 127.25, 128.53, 128.96, 130.08, 130.33, 135.22,
147.35, 148.38, 148.70, 149.32; ESI-HRMS calculated for
C20H17NO2: 335.3533. Found: 335.3530 (M+).
REFERENCES AND NOTES
[1] Dhar, T. G. M.; Davies, G. Y. P.; Malley, M. F.; Gougoutas,
J. Z.; Wu, D.-R.; Barrish, J. C.; Carter, P. H. Bioorg Med Chem Lett
2009, 19, 96.
[2] Mukhtar, T. A.; Wright, G. T. Chem Rev 2005, 105, 529.
[3] Gormley, G., J.; Chan, Y. Y.; Fried, J. J Org Chem 1980, 45, 1447.
[4] Larson, G. M.; Schaneberg, B. T.; Sneden, A. T. J Nat Prod
1999, 62, 361.
[5] Cassady, J. M.; Chan, K. K.; Floss, H. G.; Leistner, E. Chem
Pharm Bull 2004, 52, 1.
[6] Poindexter, G. S.; Strauss, K. M. Synth Commun 1993, 23, 1329.
[7] Bongini, A.; Cardillo, G.; Orena, M.; Porzi, G.; Sandri, S.
Chem Lett 1988, 87.
[8] Evans, D. A. Aldrichimica Acta 1982, 15, 23.
[9] Saito, T.; Yamada, T.; Miyazaki, S.; Otani, T. Tetrahedron Lett
2004, 45, 9585.
[10] Dabiri, M.; Delbari, A. S.; Bazgir, A. Synlett 2007, 5, 821.
[11] Dabiri, M.; Delbari, A. S.; Bazgir, A. Heterocycles 2007, 71, 543.
[12] Szatmári, I.; Hetényi, A.; Lázár, L.; Fülöp, F. J Heterocycl
Chem 2004, 41, 367.
[13] Mosslemin, M. H.; Nateghi, R. M. Monatsh Chem 2008, 139, 1247.
[14] Togo, H.; Iida, S. Synlett 2006, 14, 2159.
[15] Pasha, M. A.; Jayashankara, V. P. Synth Commun 2006, 36,
1787.
[16] Kumar, N.; Khan, S. I.; Sharma, M.; Atheaya. H.; Rawat D. S.
Bioorg Med Chem Lett 2009, 19, 1675.
1-m-Tolyl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-one
(1l).
Yield: 86%; mp: 220–223ꢀC; IR (KBr, cmÀ1): 3141, 2923,
2854, 1751, 1222, 1181, 993; 1H NMR (300 MHz, DMSO-d6): 2.23
(s, 3H, PhCH3), 6.13 (d, J = 3 Hz, 1H, PhCH), 7.05–7.23 (m, 4H),
7.36–7.51 (m, 3H), 7.79 (d, J = 8.1 Hz, 1H), 7.93–8.00 (m, 2H),
8.81 (s, 1H); ESI-HRMS calculated for C19H15NO2: 289.1103.
Found: 289.1118 (M+).
1-o-Tolyl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-one
(1m).
Yield: 92%; mp: 256ꢀC; IR (Nujol, cmÀ1): 3231, 3140,
1
2924, 1725, 1377, 1224, 1187, 823; H NMR (300 MHz, DMSO-
d6): 2.65 (s, 3H, PhCH3), 6.33 (d, J = 2.4 Hz, 1H, PhCH), 6.75 (d,
J = 7.8 Hz, 1H), 7.02–7.14 (m, 2H), 7.20 (d, J = 7.2 Hz, 1H), 7.35–
7.43 (m, 4H), 7.91–8.00 (m, 2H), 8.70 (s, 1H); ESI-HRMS
calculated for C19H15NO2: 289.1103. Found: 289.1109 (M+).
1-(4-Iso-propyl-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]
oxazin-3-one (1n).
Yield: 95%; mp: 241–243ꢀC; IR (Nujol,
1
cmÀ1): 3135, 2924, 2854, 1730, 1221, 1172, 1110; H NMR (300
MHz, DMSO-d6): 1.10 (d, J = 4.2 Hz, 6H, PhCH(CH3)2), 2.74–
2.80 (m, 1H, PhCH(CH3)2), 6.11 (d, J = 2.7 Hz, 1H, PhCH), 7.15–
7.22 (m, 4H), 7.34–7.47 (m, 3H), 7.79 (d, J = 8.1 Hz, 1H), 7.91–
7.98 (m, 2H), 8.76 (s, 1H); ESI-HRMS calculated for C21H19NO2:
317.1416. Found: 317.1419 (M+).
[17] Houston, T. A.; Wilkinson, B. L.; Blanchfield, J. T. Org Lett
2004, 6, 679.
1-(4-Ethyl-phenyl)-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-
[18] Chaudhuri, M. K.; Hussain, S.; Kantam, M. L.; Neelima, B.
Tetrahedron Lett 2005, 46, 8329.
[19] Nath, J.; Chaudhuri, M. K. Green Chem Lett Rev 2008, 1, 223.
[20] Heravi, M. M., Baghernejad, B., Oskooie, H.A. Curr Org
Chem 2009, 13, 1002.
[21] Yadav, J. S.; Ather, H.; Rao; P. P.; Rao; R. S.; Nagaiah, K.;
Prasad, A.R. Catal Commun 2006, 7, 797.
[22] Gurinot, A.; Serra-Muns, A.; Gnamm, C.; Bensoussan, C.;
Reymond, S.; Cossy, J. Org Lett 2010, 12, 1808.
one (1o). Yield: 86%; mp: 210–213ꢀC; IR (KBr, cmÀ1): 3256,
1
3147, 2964, 2928, 1734, 1516, 1222, 810; H NMR (300 MHz,
DMSO-d6): 1.09 (t, J = 7.5 Hz, 3H, PhCH2CH3), 2.50 (q, J = 7.5
Hz, 2H, PhCH2CH3), 6.14 (d, J = 2.7 Hz, 1H, PhCH), 7.13 (d, J
= 8.1 Hz, 2H), 7.20 (d, J = 8.1 Hz, 2H), 7.36–7.50 (m, 3H), 7.80
(d, J = 8.1 Hz, 1H), 7.92–7.99 (m, 2H), 8.81 (s, 1H); ESI-HRMS
calculated for C20H17NO2: 303.1259. Found: 303.1252 (M+).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

May 2012
Lewis Acid Catalyzed Synthesis of 1-Aryl-1,2-dihydro-naphtho[1,2-e][1,3]oxazin-3-ones
under Solvent Free Conditions: A Mechanistic Approach
595
[23] Nagarapu, L.; Bantu, R.; Puttireddy, R. App Catal A General
2007, 332, 304.
[24] Ranu, B. C.; Jana, U. J Org Chem 1998, 63, 8212.
[28] Saini, A.; Kumar, S.; Sandhu, J. S. Synlett 2006, 1928.
[29] Kumar, R.; Nandi, G. C.; Verma, R. K.; Singh, M. S. Tetrahe-
dron Lett 2010, 51, 442.
[25] Su, W.; Yang, D.; Jin, C.; Zhang, B. Tetrahedron Lett 2008, 49, 3391.
[26] Kito, T.; Yoshinaga, K.; Ohkami, S.; Ikeda, K.; Yamaye, M. J
Org Chem 1985, 50, 4628.
[30] Bhattacharya, A. K.; Rana, K. C. Mendeleev Commun 2007,
17, 247.
[31] Das, B.; Ravikanth, B.; Ramu, R.; Laximinarayana, K.;
Rao, B. V. J Mol Catal A: Chem 2006, 255, 74.
[27] Chiba, T. Bull Chem Soc Jpn 1965, 38, 259.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet