Synthesis and characterization of oxadisilole-fused-3,4-dihydro-2H- naphtho[2,1-e]-1,3-oxazines and 3,4-dihydro-2H-anthra[2,1-e]-1,3-oxazines

Article abstract of DOI:10.1016/j.tet.2013.05.052

Oxadisilole-fused-3,4-dihydro-2H-naphtho[2,1-e]-1,3-oxazines and 3,4-dihydro-2H-anthra[2,1-e]-1,3-oxazines were synthesized through an eco-friendly Mannich type condensation-cyclization reaction of oxadisilole-fused-1-naphthalenol or 1-anthracenol with fo

Full text of DOI:10.1016/j.tet.2013.05.052

Tetrahedron 69 (2013) 6144e6149
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and characterization of oxadisilole-fused-3,4-dihydro-2H-
naphtho[2,1-e]-1,3-oxazines and 3,4-dihydro-2H-anthra[2,1-e]-1,3-
oxazines
,
,
,
a
a
a
Di Xu a y, Yibei Lin a y, Yali Chen a , Jie Zhang , Weiguo Cao , Jie Chen ,
*
Man Shing Wong b
,
*
a Department of Chemistry, Shanghai University, Shanghai 200444, PR China
b Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Oxadisilole-fused-3,4-dihydro-2H-naphtho[2,1-e]-1,3-oxazines and 3,4-dihydro-2H-anthra[2,1-e]-1,3-
oxazines were synthesized through an eco-friendly Mannich type condensationecyclization reaction
of oxadisilole-fused-1-naphthalenol or 1-anthracenol with formaldehyde and primary amines at ambi-
ent temperature in high to excellent yields. The photophysical, electrochemical, and thermal properties
of these 3,4-dihydro-2H-anthra[2,1-e]-1,3-oxazine derivatives were also studied.
Received 1 March 2013
Received in revised form 6 May 2013
Accepted 15 May 2013
Available online 18 May 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Naphthalenol
Anthracenol
Mannich condensation
Dihydro-2H-naphtho[2,1-e]-1,3-oxazine
Dihydro-2H-anthra[2,1-e]-1,3-oxazine
1. Introduction
ring-opening polymerizations show excellent physical properties,
such as high mechanical strength, thermal stability, and durability
The Mannich-type reaction has been widely used1 as a conve-
nient strategy to prepare a variety of 1,3-oxazine derivatives. It is
also an efficient reaction with high atom-economy. Dihydrobenzo/
naphtho[e]-1,3-oxazines, synthesized from phenols or naph-
thalenols, formaldehyde, and primary amines via the Mannich
reaction, are known to exhibit a wide range of valuable pharma-
cological properties, such as antitumor,2 antibacterial,3 anti-HIV,4
and antimicrobial agents5 and antimalarial agents6 as well as
for their versatility as synthetic intermediates.7 In addition,
6-arylbenzoxazines have been examined as progesterone receptor
or modulators and reported as potent nonsteroidal progesterone
receptor agonists.8 Naphthoxazine derivatives have also exhibited
therapeutic potential for the treatment of Parkinson’s disease.9
On the other hand, benzoxazines have received considerable
attention because the benzoxazine-based polymers derived from
under a humid environment.10 These molecules are very useful
building blocks for making phenol-type polymers, such as poly-
benzoxazines, offering lucrative mechanical, and electrical prop-
erties.11 Although several methods for the preparation of
dihydrobenzo/naphtho[e]-1,3-oxazine derivatives have previously
been documented,5b,c,12 however, dihydroanthra[e]-1,3-oxazines
have not been reported yet. In this contribution, we report our
findings on the synthesis of oxadisilole-fused-3,4-dihydro-2H-
naphtho[2,1-e]-1,3-oxazines 6aeg and 3,4-dihydro-2H-anthra
[2,1-e]-1,3-oxazines 11aef using oxadisilole-fused-1-naphthalenol
4 or 1-anthracenol 10, formaldehyde, and primary amines 5aeg
as substrates for the Mannich reaction at room temperature. Oxa-
disilole-fused-1-naphthalenol 4 or 1-anthracenol 10 was synthe-
sized from aromatization of oxabicyclic alkenes 3 or 9. The
oxabicyclic alkenes 3 and 9 are the furan cycloadducts of benzyne
2 and naphthyne 8 generated from benzobis(oxadisilole) 1 and
2,3-naphthoxadisilole 7, respectively (Schemes 1 and 2).13 The
previously unknown compounds, 11aee were also characterized,
11bee show potential as deep-blue emitters for OLED applications
because of high fluorescence quantum yields.
* Corresponding authors. Tel./fax: þ86 21 66132797; e-mail address: ylchen@
staff.shu.edu.cn (Y. Chen).
y
These authors contributed equally to this work.
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.05.052

D. Xu et al. / Tetrahedron 69 (2013) 6144e6149
6145
Table 1
O
Si
Si
Si
Si
Si
Si
Optimization of the reaction conditions for the synthesis of 6c from 4, formaldehyde,
Si
Si
and 5ca
O
N
O
O
O
O
1
2
3
OH
NH2
R
O
N
O
OH
Si
Si
Solvent
r.t.
Si
Si
R-NH2
Si
Si
Si
Si
HCHO,
HCl, THF
O
+
+
HCHO
5a-g
O
O
O
8 0 o
C
EtOH/H2O
r.t.
5c
4
6c
6a-g
4
a: R = 4-OCH3C6H4; e: R = -C10H7;
Entry
Solvent
Time (h)
Yieldb of 6c (%)
b: R = 4-CH3C6H4; f: R = n-C8H17
;
c: R = C6H5;
d: R = 4-ClC6H4;
g: R = n-C3H7
1
2
3
4
5
6
7
8
H2O
EtOH
EtOH/H2O (1:1)
o-Xylene
DME
CH2Cl2
CH3CN
DMF
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
EtOH/H2O (1:1)
3
3
3
3
3
3
3
3
1
2
4
6
16
73
64
84
86
50
80
75
d
Scheme 1. Synthesis of oxadisilole-fused 3,4-dihydro-2H-naphtho[2,1-e]-1,3-oxazine
derivatives 6aeg.
O
Si
9
66
73
71
56
53
O
O
10
11
12
13
Si
7
9
8
R
N
OH
O
a
R-NH2
Reaction conditions: 1.5 mmol of 4, 3.0 mmol of formaldehyde, and 1.5 mmol
HCHO,
HCl, THF
5a-g
of 5c.
b
Yield of isolated product.
8 0 o
C
o-Xylene
r.t.
10
11a-f
To probe the effect of primary amine on the Mannich reaction of
a: R = 4-OCH3C6H4;
b: R = 4-CH3C6H4;
c: R = C6H5;
d: R = 4-ClC6H4;
e: R = -C10H7;
oxadisilole-fused-1-naphthalenol 4 with formaldehyde (Scheme 1),
various primary aryl and alkyl amines 5aeg (1:2:1) in EtOH/H2O
(1:1) at room temperature for 3 h were studied. The results are
summarized in Table 2 (Entries 1e7). As shown from the results, the
Mannich reaction of 4 with formaldehyde is quite susceptible to the
electronic nature (X¼OCH3, CH3, H, Cl) of the substituent on the aryl
amines 5aed (Table 2, Entries 1e4). It was shown that the electron-
rich aromatic primary amines afforded a higher yield than the
electron-deficient counterparts. The stronger the electron-donating
property of the substituent (X¼OCH3) (Table 2, Entry 1), the higher
the isolated yield was. In addition, the short aliphatic primary amine
5g gave a higher yield than the longer counterparts 5f (Table 2,
f: R = n-C8H17
;
Scheme 2. Synthesis of 3,4-dihydro-2H-anthra[2,1-e]-1,3-oxazine derivatives 11aef.
2. Results and discussion
The syntheses of oxadisilole-fused 3,4-dihydro-2H-naphtho-
[2,1-e]-1,3-oxazines 6aeg or 3,4-dihydro-2H-anthra[2,1-e]-1,3-
oxazines 11aef through an eco-friendly Mannich type con-
densationecyclization reaction of oxadisilole-fused 1-naphthalenol 4
or 1-anthracenol 10 with formaldehyde and primary amines 5aeg at
room temperature in high to excellent yields are reported. Acidic
Entries 6e7). On the other hand, a-naphthylamine, afforded the poor
yield (Table 2, Entry 5).
treatment of oxadisilole-fused benzo-oxabicyclic alkene
3 or
naphtho-oxabicyclic alkene 9 inTHFat 80 ꢀC gave 92% or 95% yields of
oxadisilole-fused-1-naphthalenol 4 or 1-anthracenol 10, respectively.
The oxabicyclic alkene 3 or 9 was prepared in 88% or 54% yield by
means of the DielseAlder cycloaddition of arynes (2 or 8) generated
from benzobis(oxadisilole) 1 or 2,3-naphthoxadisilole 7 with furan,
respectively, via our previously reported phenyliodination/fluoride-
induced desilylation protocol (Schemes 1 and 2).13
Initially, an one-pot, three components reaction of oxadisilole-
fused 1-naphthalenol 4, formaldehyde, and aniline 5c (1:2:1) was
conducted in water (H2O) at room temperature for 3 h afforded
oxadisilole-fused-3,4-dihydro-2H-naphtho[2,1-e]-1,3-oxazine 6c in
73% isolated yield (Scheme 1, Table 1, Entry 1). The effect of various
solvents, such as EtOH, EtOH/H2O (1:1), o-xylene, DME, CH2Cl2,
CH3CN, and DMF on this reaction was also studied and the results
are tabulated in Table 1 (Table 1, Entries 2e8). The use of EtOH/H2O
and o-xylene as solvent afforded a higher yield (84% or 86%) of 6c
for 3 h without Lewis acid catalyst (Table 1, Entries 3e4). Certainly,
EtOH/H2O (1:1) is a more environment-friendly solvent for prac-
tical use. Varying the reaction time at 1 h, 2 h, 4 h, 6 h or 16 h at
room temperature in EtOH/H2O gave 53e73% yield (Table 1, Entries
9e13). The optimal conditions were obtained when the reaction of
oxadisilole-fused 1-naphthalenol 4, formaldehyde, and aniline 5c
(1:2:1) in EtOH/H2O (1:1) was carried out at room temperature for
3 h (Table 1, Entry 3).
Table 2
Synthesis of 6aeg or 11aef from 4 or 10, formaldehyde, and 5aega via Schemes 1
and 2
Entry
Primary amine
R
Phenol
Product
Yieldb (%)
1
2
3
4
5
6
7
8
5a
5b
5c
5d
5e
5f
5g
5a
5b
5c
5d
5e
5f
4-OCH3C6H4
4-CH3C6H4
C6H5
4
4
4
4
4
4
4
10
10
10
10
10
10
6a
6b
6c
6d
6e
6f
6g
11a
11b
11c
11d
11e
11f
90
80
84
73
55
40
76
65
43
62
60
42
62
4-ClC6H4
a
-C10H7
n-C8H17
n-C3H7
4-OCH3C6H4
4-CH3C6H4
C6H5
9
10
11
12
13
4-ClC6H4
a
-C10H7
n-C8H17
a
Reaction conditions: 1.5 mmol of 4 or 10, 3.0 mmol of formaldehyde, and
1.5 mmol of 5aeg.
b
Yields of isolated product.
Our attention then turned to use 1-anthracenol 10 as a substrate
for the Mannich reactions with formaldehyde and various primary
amines 5aef (1:2:1) at room temperature for 3 h in o-xylene. The
use of o-xylene as a solvent in this three-component Mannich

6146
D. Xu et al. / Tetrahedron 69 (2013) 6144e6149
reaction is due to the poor solubility of 1-anthracenol 10 in EtOH/
H2O (1:1). To our delight, both the electron rich and the electron
deficient aryl amines successfully participated in Mannich reaction,
affording the desired products of 3,4-dihydro-2H-anthra[2,1-e]-1,3-
oxazine derivatives 11aef in 42e65% isolated yields (Scheme 2,
Table 2, Entries 8e13).
The structures of compounds 6aeg and 11aef were established
by 1H and 13C NMR spectroscopy, IR spectroscopy, elemental
analysis, and high-resolution (HR) MS, which are in good agree-
ment with the expected structures.
11a
11b
11c
11d
11e
1.0
0.8
0.6
0.4
0.2
0.0
The absorption spectra of 11aee were measured in CH2Cl2 and
the spectra data are summarized in Table 3. As seen in the ab-
sorption spectra shown in Fig. 1, all of 11aee possess the charac-
teristic of strong b-band absorption at approximately 260 nm for
11aee, while the long wavelength absorption bands are located
between 389 and 390 nm for 11aee. The substituent effect was also
observed for 11aee in which the electron-withdrawing or electron-
donating groups (X¼OCH3, CH3 or NO2) result in a slightly red shift
in absorption with respect to 11c (X¼H). The photoluminescence
spectra of 11aee in CH2Cl2 are shown in Fig. 2, in which they emit in
the range of 434e442 as shown in Table 3. A similar substituent
effect was also found for the emission maximum for 11aee, that is,
the emission maximum shifts to a longer wavelength for de-
rivatives substituted with an electron-donating or an electron-
withdrawing group (i.e., X¼OCH3, CH3 or NO2) relative to that of
11c (X¼H), which provides a mean to tune the color emission of this
350
400
450
500
550
600
Fig. 2. Emission spectra of 11aee in CH2Cl2.
11a, showed lower fluorescence quantum yield than anthracene
(quantum yield is 0.36).14 This result clearly showed that the FFL
value dropped sharply with decreasing oxidation potential, and
finally reached FFL¼0.004 in the case where the benzene moiety
was 4-dimethoxybenzene (Table 4).15 Thus, molecules 11bee show
potential as deep-blue emitters for organic light emitting diode
(OLED) applications. In addition, the thermal properties of the
11aee were determined by DSC and TGA analyses with the de-
composition temperature in the range of 148e244 ꢀC.
series. The fluorescence quantum yields (F) measured in CH2Cl2
using norharman as the reference for 11aee are in the range of
30e68% for the 11bee (except 11a). As shown in Table 3, compound
Table 3
Summary of optical measurements and thermal properties of 11aee
abs
a
em
c
d
Compd
l
[nm] [εmax
l
a,b [nm]
FFL
Tm [ꢀC]
Tdec [ꢀC]
max
max
103/Mꢁ1 cmꢁ1
]
Table 4
11a
11b
11c
11d
11e
390 (2.05)
390 (3.19)
389 (2.87)
389 (2.55)
390 (2.64)
442
436
434
434
436
0.004
0.301
0.670
0.680
0.661
119
142
225
245
244
190
148
155
245
244
Summary of oxidation potential, HOMO, and LUMO energy levels of 11aee
Compd
Eoxa, V
HOMOb, eV
Band gapc, eV
LUMOd, eV
11a
11b
11c
11d
11e
0.85
0.89
0.92
0.95
0.95
ꢁ5.17
ꢁ5.21
ꢁ5.24
ꢁ5.27
ꢁ5.27
3.05
3.05
3.06
3.07
3.06
ꢁ2.12
ꢁ2.16
ꢁ2.18
ꢁ2.20
ꢁ2.21
a
Measured in CH2Cl2.
b
c
Excited at the absorption maximum.
Using norharman in 0.1 M H2SO4
F330w390¼0.58) as a standard for the 11aee.
Determined by thermal gravimetric analyzer with a heating rate of 10 ꢀC minꢁ1
(
d
a
Eox estimated by CV method in CH2Cl2 using a platinum disk electrode as
a working electrode, platinum wire as a counter electrode, and SCE as a reference
electrode with an agar salt bridge connecting to compound solution, and ferrocene
was used as an external standard, E1/2 (Fc/Fcþ)¼0.49 V versus SCE and calculated
with ferrocene (4.8 eV vs vacuum).
under N2.
b
HOMO¼Eoxꢁ[E1/2 (Fc/Fcþ)]þ4.8.
c
Estimated from the absorption edge in CH2Cl2.
d
LUMO¼HOMOþOptical band gap.
The redox properties as well as the HOMO (highest occupied
molecular orbital) and LUMO (lowest unoccupied molecular
orbital) energy levels of the 11aee are tabulated in Table 4. The
redox properties of the 11aee series were studied by cyclic vol-
tammetry, which was carried out in a three-electrode cell setup
with 0.1 M of Bu4NPF6 as a supporting electrolyte in CH2Cl2. All of
the potentials reported are referenced to Fc/Fcþ standard. In
contrast to the optical properties, the substituent group on the aryl
ring has insignificant effect on the oxidation potential (Eox), which
occurs between 0.85 and 0.95 V for 11aee. The HOMO energy
values were calculated according to the equation reported by
Schmidt et al. and the LUMO energy level is obtained by sub-
traction of the optical band gap from the HOMO.16 Molecules
11aee show similar HOMO levels. It is also noted that their band
gaps are also very similar.
Fig. 1. Absorption spectra of 11aee in CH2Cl2.

D. Xu et al. / Tetrahedron 69 (2013) 6144e6149
6147
3. Conclusion
4.1.2. General procedure for the synthesis of the oxasdisilole-fused-
3,4-dihydro-2H-naphtho[2,1-e]-1,3-oxazines 6aeg. The primary
amines 5aeg (3.0 mmol) and formalin (37%, w/v, 1.5 mmol) was
added by means of a syringe to a stirred mixture of the oxsdisilole-
fused-1-naphthalenol 4 (411 mg, 1.5 mmol) in EtOH/H2O (1:1,
15 mL) at room temperature under N2 for 3 h. The resulting mixture
was extracted with CH2Cl2. The organic extract was dried over
anhydrous MgSO4, filtered, and concentrated under reduced pres-
sure to give the crude product, which was purified by flash chro-
matography on silica gel using a gradient of 5e10% EtOAc in PE
(60e80 ꢀC) as the eluent to afford the compounds 6aeg.
Two previously unprecedented oxadisilole-fused-3,4-dihydro-
2H-naphtho[2,1-e]-1,3-oxazines 6aeg or 3,4-dihydro-2H-anthra
[2,1-e]-1,3-oxazines 11aef derivatives were synthesized through an
eco-friendly Mannich type condensationecyclization reaction of
oxadisilole-fused-1-naphthalenol
4 or 1-anthracenol 10 with
formaldehyde and primary amines 5aeg under mild conditions.
The photophysical, redox, and thermal properties of 3,4-dihydro-
2H-anthra[2,1-e]-1,3-oxazines 11aee were also characterized.
Molecules 11bee show potential as deep-blue emitters for OLED
applications because of high fluorescence quantum yields.
4.1.2.1. 3-(4-Methoxyphenyl)-3,4-dihydro-2H-8,9-oxadisilole-
4. Experimental section
4.1. General methods
fused-naphtho[2,1-e]-1,3-oxazine (6a). Yield: 568 mg, 90%; White
solid; mp 175e176 ꢀC; 1H NMR (500 MHz, CDCl3):
d 0.43 (6H, s,
SiMe), 0.44 (6H, s, SiMe), 3.74 (3H, s, OMe), 4.67 (2H, s, AreCH2eN),
5.48 (2H, s, OeCH2eN), 6.80 (2H, d, J¼8.5 Hz, AreH), 7.12e7.15 (3H,
m, AreH), 7.42 (1H, d, J¼8.5 Hz, AreH), 8.00 (1H, s, AreH), 8.39 (1H,
Purification was conducted on silica gel column chromatogra-
phy (200e300 mesh silica gel) using mixtures of reagent-grade
EtOAc/petroleum ether (PE, 60e80 ꢀC) as the eluents. NMR spec-
tra were recorded at 500 MHz for 1H and 125 MHz for 13C with
CDCl3 as the solvent by using a Bruker DRX-500 NMR spectrometer.
s, AreH); 13C NMR (125 MHz, CDCl3):
d 1.3, 1.4, 51.3, 55.6, 81.6, 114.6,
115.4, 120.7, 121.4, 124.5, 125.2, 125.4, 131.0, 133.6, 142.7, 143.5,
144.0, 150.0, 155.3; IR (KBr, cmꢁ1) 2958, 2898, 1617, 1565, 1524,
1251, 1094, 841; MS (EI): m/z (%)¼421 (11, Mþ), 135 (100); HRMS
(EI): Mþ, found: 421.1530. C23H27NO2Si3 requires 421.1532.
Chemical shifts are reported in parts per million on the
relative to the residual resonance of CHCl3 (
d scale
d
¼7.26 ppm for 1H, and
77.16 ppm for the central peak of the triplet in 13C). Coupling
constants (J) are reported in Hertz. IR spectra were recorded with
an FTIR spectrometer and expressed in cmꢁ1 (KBr disc). Low-
resolution mass spectra were obtained with an Agilent spectrom-
eter in EI or API-ES mode and are reported as m/z values. High-
resolution mass spectra were recorded with a Waters Micromass
GCT instrument. Element analyses were performed at the Shanghai
University. The fluorescence quantum yields in solution were de-
termined by dilution method using norharman (F330w390¼0.58) as
a standard. Thermal stabilities were determineꢁd1by thermal gravi-
metric analyzer with heating rate of 10 ꢀC min under N2.
4.1.2.2. 3-(4-Methylphenyl)-3,4-dihydro-2H-8,9-oxadisilole-
fused-naphtho[2,1-e]-1,3-oxazine (6b). Yield: 490 mg, 80%; White
solid; mp 200e201 ꢀC; 1H NMR (500 MHz, CDCl3):
d 0.45 (6H, s,
SiMe), 0.46 (6H, s, SiMe), 2.28 (3H, s, Me), 4.72 (2H, s, AreCH2eN),
5.55 (2H, s, OeCH2eN), 7.06 (2H, d, J¼9.0 Hz, AreH), 7.10 (2H, d,
J¼9.0 Hz, AreH), 7.16 (1H, d, J¼8.5 Hz, AreH), 7.43 (1H, d, J¼8.5 Hz,
AreH), 7.97 (1H, s, AreH), 8.38 (1H, s, AreH); 13C NMR (125 MHz,
CDCl3):
d 1.3, 1.4, 20.7, 50.8, 80.8, 115.4, 119.2, 120.7, 124.5, 125.2,
125.4, 129.9, 130.9, 131.5, 133.6, 143.4, 144.0, 146.5, 150.0; IR (KBr,
cmꢁ1) 2958, 2898, 1617, 1565, 1524, 1251, 1094, 841; MS (EI): m/z
(%)¼405 (9, Mþ), 57 (100); Anal. Found: C, 67.89; H, 6.62; N, 3.43.
C23H27NO2Si2 requires C, 68.10; H, 6.71; N, 3.45.
4.1.1. General procedure for the synthesis of 6,7-oxasdisilole-fused-1-
naphthalenol (4) and 1-anthracenol (10). A mixture of oxabicyclic
alkenes 3 or 9 (1 mmol) and 36% concentrated HCl (0.4 mL) in THF
(2 mL) was stirred at 85 ꢀC for 4 h. The reaction mixture was cooled
to room temperature. Water was added and the resulting mixture
was extracted with CH2Cl2, The organic extract was dried over
anhydrous MgSO4, filtered, and concentrated under reduced pres-
sure to give the crude product, which was further purified by flash
chromatography on silica gel using a gradient of 2e5% EtOAc in PE
(60e80 ꢀC) as the eluent to afford the compound 4 or 10.
4.1.2.3. 3-Phenyl-3,4-dihydro-2H-8,9-oxadisilole-fused-naphtho
[2,1-e]-1,3-oxazine (6c). Yield: 493 mg, 84%; White solid; mp
177e179 ꢀC; 1H NMR (500 MHz, CDCl3):
d 0.44 (6H, s, SiMe), 0.45
(6H, s, SiMe), 4.76 (2H, s, AreCH2eN), 5.57 (2H, s, OeCH2eN),
6.94e6.97 (2H, m, AreH), 7.16e7.19 (3H, m, AreH), 7.27e7.30 (2H,
m, AreH), 7.43 (1H, d, J¼8.0 Hz, AreH), 8.00 (1H, s, AreH), 8.40 (1H,
s, AreH); 13C NMR (125 MHz, CDCl3): (125 MHz, CDCl3):
d 1.3, 1.4,
50.6, 80.3, 115.4, 118.8, 120.8, 121.8, 124.4, 125.2, 125.4, 129.4, 131.0,
133.6, 143.5, 144.1, 148.7, 150.0; IR (KBr) 3402, 2923, 1599, 1465,
1442, 1279, 737, 700 cmꢁ1; MS m/z (%) (EI): 391 (31, Mþ), 271 (100);
Anal. Found: C, 67.11; H, 6.56; N, 3.61. C22H25NO2Si2 requires C,
67.47; H, 6.43; N, 3.58.
4.1.1.1. 6,7-Oxasdisilole-fused-1-naphthalenol (4). Yield: 252 mg,
92%; White solid; mp 188e189 ꢀC; 1H NMR (500 MHz, CDCl3):
d
0.459 (6H, s, SiMe), 0.461 (6H, s, SiMe), 5.83 (1H, s, OH), 6.85e6.87
(1H, m, AreH), 7.33e7.36 (1H, t, J¼8.0 Hz, AreH), 7.47 (1H, d,
4.1.2.4. 3-(4-Chlorophenyl)-3,4-dihydro-2H-8,9-oxadisilole-
J¼8.0 Hz, AreH), 8.06 (1H, s, AreH), 8.46 (1H, s, AreH); 13C NMR
fused-naphtho[2,1-e]-1,3-oxazine (6d). Yield: 467 mg, 73%; White
(125 MHz, CDCl3):
d
1.35, 1.43, 109.3, 121.1, 124.85, 124.91, 126.6,
solid; mp 195e196 ꢀC; 1H NMR (500 MHz, CDCl3):
d 0.46 (6H, s,
131.1, 135.0, 143.1, 144.4, 151.9; IR (KBr, cmꢁ1) 3504, 2951, 2895,
1621, 1561, 1449, 1252, 1097; MS (EI): m/z (%)¼274 (37, Mþ), 259
(100); HRMS (EI): Mþ, found: 274.0845. C14H18O2Si2 requires
274.0842.
SiMe), 0.47 (6H, s, SiMe), 4.71 (2H, s, AreCH2eN), 5.52 (2H, s,
OeCH2eN), 7.10 (2H, d, J¼9.0 Hz, AreH), 7.15 (1H, d, J¼8.0 Hz,
AreH), 7.22 (2H, d, J¼9.0 Hz, AreH), 7.46 (1H, d, J¼8.0 Hz, AreH),
8.02 (1H, s, AreH), 8.41 (1H, s, AreH); 13C NMR (125 MHz, CDCl3):
d
1.3, 1.4, 50.8, 80.1, 115.0, 120.0, 121.0, 124.4, 125.0, 125.3, 126.8,
4.1.1.2. 1-Anthracenol (10). Yield: 184 mg, 95%; White solid; mp
151e152 ꢀC (lit.16 mp 151e152 ꢀC); 1H NMR (500 MHz, CDCl3):
129.3, 131.0, 133.6, 143.7, 144.3, 147.4, 149.9; IR (KBr, cmꢁ1) 2955,
2871, 1597, 1564, 1502, 1253, 1096, 841; MS (EI): m/z (%)¼426
(5, Mþ), 271 (100); Anal. Found: C, 61.98; H, 5.60; N, 3.35.
C22H24ClNO2Si2 requires C, 62.02; H, 5.68; N, 3.29.
d
5.70 (1H, s, AreOH), 6.77 (1H, d, J¼7.0 Hz, AreH), 7.29e7.32 (1H,
m, AreH), 7.47e7.50 (2H, m, AreH), 7.63 (1H, d, J¼8.5 Hz, AreH),
7.99e8.01 (1H, m, AreH), 8.05e8.07 (1H, m, AreH), 8.40 (1H, s,
AreH), 8.80 (1H, s, AreH); 13C NMR (125 MHz, CDCl3):
d
106.5,
4.1.2.5. 3-(
naphtho[2,1-e]-1,3-oxazine (6e). Yield: 364 mg, 55%; Yellow solid;
mp 197e199 ꢀC; 1H NMR (500 MHz, CDCl3):
0.47 (6H, s, SiMe),
a-Naphthyl)-3,4-dihydro-2H-8,9-oxadisilole-fused-
120.8, 121.1, 124.1, 125.3, 125.4, 125.9, 126.1, 128.1, 128.8, 131.4, 132.1,
132.9, 151.5.
d

6148
D. Xu et al. / Tetrahedron 69 (2013) 6144e6149
0.48 (6H, s, SiMe), 4.82 (2H, s, AreCH2eN), 5.62 (2H, s, OeCH2eN),
7.11 (1H, d, J¼8.5 Hz, AreH), 7.28e7.31 (1H, m, AreH), 7.43e7.47
(2H, m, AreH), 7.52e7.56 (1H, m, AreH), 7.59e7.62 (2H, m, AreH),
7.87 (1H, d, J¼8.0 Hz, AreH), 8.04 (1H, s, AreH), 8.30 (1H, d,
J¼8.5 Hz, AreH), 8.49 (1H, s, AreH); 13C NMR (125 MHz, CDCl3):
124.4, 124.5, 125.4, 125.6, 126.0, 128.1, 128.8, 129.9, 131.3, 131.5,
131.6, 131.8, 146.6, 149.5; IR (KBr, cmꢁ1) 2916, 2856, 1640, 1620,
1519, 1267, 1070, 843; MS (EI): m/z (%)¼325 (21, Mþ), 206 (100);
HRMS (EI): Mþ, found: 325.1467. C23H19NO requires 325.1464.
d
1.3, 1.4, 52.3, 82.2, 115.5, 118.0, 120.8, 123.6, 124.6, 124.8, 125.3,
4.1.3.3. 3-Phenyl-3,4-dihydro-2H-anthra[2,1-e]-1,3-oxazine
125.5, 126.01, 126.04, 126.1, 128.7, 129.1, 131.0, 133.7, 134.9, 143.6,
144.1, 146.2, 149.6; IR (KBr, cmꢁ1) 2955, 2897, 1626, 1560, 1464,
1252, 1096, 839; MS (EI): m/z (%)¼441 (10, Mþ), 57 (100); Anal.
Found: C, 70.48; H, 6.23; N, 3.14. C24H37NO2Si2 requires C, 70.70; H,
6.16; N, 3.17.
(11c). Yield: 289 mg, 62%; Yellow solid; mp 224e226 ꢀC; 1H NMR
(500 MHz, CDCl3):
d 4.75 (2H, s, AreCH2eN), 5.62 (2H, s,
OeCH2eN), 6.96e6.99 (1H, m, AreH), 7.10 (1H, d, J¼8.5, AreH),
7.23e7.25 (2H, m, AreH), 7.30e7.33 (2H, m, AreH), 7.48e7.50 (2H,
m, AreH), 7.57 (1H, d, J¼8.5 Hz, AreH), 7.98e8.00 (1H, m, AreH),
8.05e8.07 (1H, m, AreH), 8.34 (1H, s, AreH), 8.76 (1H, s, AreH); 13C
4.1.2.6. 3-Octyl-3,4-dihydro-2H-8,9-oxadisilole-fused-naphtho-
NMR (125 MHz, CDCl3): d 50.8, 80.0, 112.8, 118.5, 120.2, 120.8, 121.7,
[2,1-e]-1,3-oxazine (6f). Yield: 256 mg, 40%; Yellow oil; 1H NMR
124.4, 124.5, 125.4, 125.6, 126.0, 128.1, 128.8, 129.4, 131.5, 131.6,
131.9, 148.8, 149.6; IR (KBr, cmꢁ1) 2880, 2786, 1640, 1596, 1553,
1269, 1069, 838; MS (EI): m/z (%)¼311 (18, Mþ), 206 (100); HRMS
(EI): Mþ, found: 311.1310. C22H17NO: 311.1313.
(500 MHz, CDCl3): d 0.55 (6H, s, SiMe), 0.56 (6H, s, SiMe), 1.00 (3H, t,
J¼7.0 Hz, CH2eCH3), 1.39e1.42 (12H, m, CH2), 2.90 (2H, t, J¼7.0 Hz,
NeCH2eCH2), 4.19 (2H, s, AreCH2eN), 5.16 (2H, s, OeCH2eN), 7.15
(2H, d,J¼8.5Hz,AreH),7.47(1H,d,J¼8.5Hz, AreH), 8.10(1H, s,AreH),
8.55(1H, s,AreH);13CNMR(125MHz, CDCl3):
d
1.3, 1.4, 14.2, 22.7, 27.4,
4.1.3.4. 3-(4-Chlorophenyl)-3,4-dihydro-2H-anthra[2,1-e]-1,3-
28.3, 29.4, 29.6, 31.9, 50.5, 51.8, 83.0, 114.6, 120.2, 124.4, 125.1, 126.0,
130.9, 133.6, 143.2, 143.7, 149.6; IR (KBr, cmꢁ1) 2955, 2927,1626,1562,
1425, 1252, 1096, 841; MS (EI): m/z (%) 427 (1, Mþ), 273 (100); HRMS
(EI): Mþ, found: 427.2363. C24H37NO2Si2 requires 427.2361.
oxazine (11d). Yield: 311 mg, 60%; Yellow solid; mp 235e236 ꢀC; 1H
NMR (500 MHz, CDCl3):
d 4.69 (2H, s, AreCH2eN), 5.55 (2H, s,
OeCH2eN), 7.06e7.14 (3H, m, AreH), 7.21e7.24 (2H, m, AreH),
7.45e7.49 (2H, m, AreH), 7.57 (1H, d, J¼8.5 Hz, AreH), 7.97e8.04
(2H, m, AreH), 8.33 (1H, s, AreH), 8.71 (1H, s, AreH); 13C NMR
4.1.2.7. 3-Propyl-3,4-dihydro-2H-8,9-oxadisilole-fused naphtha-
(125 MHz, CDCl3): d 51.0, 79.9, 112.5, 119.9, 120.2, 121.0, 124.2, 124.4,
[2,1-e]-1,3-oxazine (6g). Yield: 407 mg, 76%; Yellow oil; 1H NMR
125.6, 125.8, 126.1, 126.7, 128.1, 128.8, 129.3, 131.55, 131.61, 131.9,
147.5, 149.5; IR (KBr, cmꢁ1) 2939, 2884,1631, 1592,1575, 1264,1068,
842; MS (EI): m/z (%)¼345 (11, Mþ), 206 (100); HRMS (EI): Mþ,
found: 345.0920. C22H16ClNO requires 345.0922.
(500 MHz, CDCl3): d 0.50 (6H, s, SiMe), 0.51 (6H, s, SiMe), 1.00 (3H, t,
J¼7.0 Hz, CH2eCH3), 1.67e1.71 (2H, m, CH2eCH3), 2.83 (2H, t,
J¼7.0 Hz, NeCH2eCH2), 4.16 (2H, s, AreCH2eN), 5.13 (2H, s,
OeCH2eN), 7.12 (1H, d, J¼8.0 Hz, AreH), 7.43 (1H, d, J¼8.0 Hz,
AreH), 8.05 (1H, s, AreH), 8.47 (1H, s, AreH); 13C NMR (125 MHz,
4.1.3.5. 3-(
oxazine (11e). Yield: 227 mg, 42%; Yellow solid; mp 178e180 ꢀC; 1H
NMR (500 MHz, CDCl3): 4.78 (2H, s, AreCH2eN), 5.66 (2H, s,
a-Naphthdyl)-3,4-dihydro-2H-anthra[2,1-e]-1,3-
CDCl3): d 1.3, 1.4, 11.8, 21.5, 50.5, 53.8, 83.1, 114.7, 120.2, 124.4, 125.1,
126.1, 131.0, 133.6, 143.2; IR (KBr, cmꢁ1) 2962, 2903, 1626, 1562,
1470, 1250, 1098, 841; MS(EI): m/z (%) 357 (22, Mþ), 271 (100);
HRMS (EI): Mþ, found: 357.1580. C19H27NSi2O2 requires 357.1579.
d
OeCH2eN), 7.04 (1H, d, J¼9.0 Hz, AreH), 7.28e7.31 (1H, m, AreH),
7.47e7.62 (7H, m, AreH), 7.87 (1H, d, J¼8.5 Hz, AreH), 7.98e8.07
(2H, m, AreH), 8.32 (1H, J¼8.5 Hz, AreH), 8.35 (1H, s, AreH), 8.80
4.1.3. General procedure for the synthesis of the 3,4-dihydro-2H-
anthra[2,1-e]-1,3-oxazines 11aef. The primary amines 5aef
(3.0 mmol) and formalin (37%, w/v,1.5 mmol) was added by means of
a syringe to a stirred mixture of the 1-anthracenol 10 (291 mg,
1.5 mmol) in o-xylene (15 mL) at room temperature under N2 for 3 h.
The resulting mixture was extracted with CH2Cl2, The organic extract
was dried over anhydrous MgSO4, filtered, and concentrated under
reduced pressure to give the crude product, which was purified by
flash chromatography on silica gel using a gradient of 5e10% EtOAc
in PE (60e80 ꢀC) as the eluent to afford the compounds 11aef.
(1H, s, AreH); 13C NMR (125 MHz, CDCl3):
d 52.4, 82.2, 112.9, 117.7,
120.3, 120.8, 123.7, 124.5, 124.8, 125.5, 125.7, 126.02, 126.04, 126.1,
128.1, 128.7, 128.8, 129.1, 131.6, 131.7, 131.9, 134.9, 146.3, 149.1; IR
(KBr, cmꢁ1) 2939, 2884, 1631, 1592, 1575, 1264, 1068, 842; MS (EI):
m/z (%)¼361 (2, Mþ), 154 (100); HRMS (EI): Mþ, found: 361.1467.
C26H19NO requires 361.1470.
4.1.3.6. 3-(Octyl)-3,4-dihydro-2H-anthra[2,1-e]-1,3-oxazine
(11f). Yield: 323 mg, 62%; Yellow oil; 1H NMR (500 MHz, CDCl3):
d
0.92 (3H, t, J¼7.0 Hz, CH2eCH3), 1.30e1.35 (12H, m, CH2), 2.86 (2H,
t, J¼7.0 Hz, NeCH2eCH2), 4.13 (2H, s, AreCH2eN), 5.14 (2H, s,
OeCH2eN), 7.06 (1H, d, J¼9.0, AreH), 7.46e7.48 (2H, m, AreH), 7.55
(1H, d, J¼8.5, AreH), 7.98e8.07 (2H, m, AreH), 8.34 (1H, s, AreH),
4.1.3.1. 3-(4-Methoxyphenyl)-3,4-dihydro-2H-anthra[2,1-e]-1,3-
oxazine (11a). Yield: 333 mg, 65%; Yellow solid; mp 118e120 ꢀC; 1H
NMR (500 MHz, CDCl3):
d
3.73 (3H, s, OMe), 4.67 (2H, s, AreCH2eN),
8.74 (1H, s, AreH); 13C NMR (125 MHz, CDCl3):
d 14.2, 22.8, 27.4,
5.53 (2H, s, OeCH2eN), 6.81 (2H, d, J¼9.0 Hz, AreH), 7.08 (1H, d,
J¼8.5 Hz, AreH), 7.16e7.17 (2H, m, AreH), 7.44e7.48 (2H, m, AreH),
7.56 (2H, d, J¼8.5 Hz, AreH), 7.96e8.03 (2H, m, AreH), 8.33 (1H, s,
28.5, 29.4, 29.7, 32.0, 50.6, 52.1, 83.1,112.1,120.1,120.2,124.3,125.31,
125.33, 125.5, 126.0, 128.1, 128.8, 131.5, 131.7, 131.8, 149.1; IR (KBr,
cmꢁ1) 2926, 2853, 1632, 1571, 1556, 1262, 1079, 910, 720; MS (EI):
m/z (%)¼347 (2, Mþ), 84 (100); HRMS (EI): Mþ, found: 347.2249.
C24H29NO requires 347.2254.
AreH), 8.72 (1H, s, AreH); 13C NMR (125 MHz, CDCl3):
d 51.6, 55.6,
81.4, 112.8, 114.6, 120.3, 120.7, 121.2, 124.5, 125.4, 125.6, 126.0, 128.1,
128.8, 131.5, 131.7, 131.9, 142.8, 149.5, 155.2; IR (KBr, cmꢁ1) 2948, 2833,
1640, 1513, 1465, 1252, 1071, 845; MS (EI): m/z (%)¼341 (1, Mþ), 120
(100); HRMS (EI): Mþ, found: 341.1416. C23H19NO2 requires 341.1415.
Acknowledgements
Financial support from the National Natural Science Foundation
of China (nos. 21272146 and 20872086) acknowledged.
4.1.3.2. 3-(4-Methylphenyl)-3,4-dihydro-2H-anthra[2,1-e]-1,3-
oxazine (11b). Yield: 210 mg, 43%; Yellow solid; mp 141e142 ꢀC; 1H
NMR (500 MHz, CDCl3): d 2.29 (3H, s, Me), 4.72 (2H, s, AreCH2eN),
References and notes
5.60 (2H, s, OeCH2eN), 7.09e7.16 (5H, m, AreH), 7.47e7.49 (2H, m,
AreH), 7.57 (1H, d, J¼8.5 Hz, AreH), 7.98e8.00 (1H, m, AreH),
8.05e8.07 (1H, m, AreH), 8.34 (1H, s, AreH), 8.76 (1H, s, AreH); 13C
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