One-step synthesis of benzo[g]phthalazines and naphtho[2,3-g]phthalazines from benzo- or naphtho-oxabicyclic alkene

Article abstract of DOI:10.1016/j.tet.2017.10.028

An efficient protocol for one-step synthesis of oxadisilole-fused benzo[g]phthalazines and naphtho[2,3-g]phthalazines by the Diels-Alder reactions and denitrogenation/deoxygenation aromatization reactions of benzo- or naphtho-oxabicyclic alkene with 3,6-d

Full text of DOI:10.1016/j.tet.2017.10.028

Accepted Manuscript
One-step synthesis of benzo[g]phthalazines and naphtho[2,3-g]phthalazines from
benzo- or naphtho-oxabicyclic alkene
Kundi Kong, Jie Zhang, Peng Zhao, Huali Lu, Zhijun Chen, Weiguo Cao, Jie Chen,
Yali Chen
PII:
S0040-4020(17)31043-8
10.1016/j.tet.2017.10.028
TET 29031
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 20 July 2017
Revised Date: 30 September 2017
Accepted Date: 9 October 2017
Please cite this article as: Kong K, Zhang J, Zhao P, Lu H, Chen Z, Cao W, Chen J, Chen Y, One-step
synthesis of benzo[g]phthalazines and naphtho[2,3-g]phthalazines from benzo- or naphtho-oxabicyclic
alkene, Tetrahedron (2017), doi: 10.1016/j.tet.2017.10.028.
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One-step synthesis of benzo[g]phthalazines
and naphtho[2,3-g]phthalazines from benzo-
or naphtho-oxabicyclic alkene
Leave this area blank for abstract info.
Kundi Konga, Jie Zhanga, Peng Zhaoa, Huali Lua, Zhijun Chena, Weiguo Caoa, Jie Chena, and Yali Chena,b,*
aDepartment of Chemistry, Innovative Drug Research Center, Shanghai University, Shanghai 200444, China
bKey Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032,
P. R. China

1
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Tetrahedron
journal homepage: www.elsevier.com
One-step synthesis of benzo[g]phthalazines and naphtho[2,3-g]phthalazines from
benzo- or naphtho-oxabicyclic alkene
Kundi Konga, Jie Zhanga, Peng Zhaoa, Huali Lua, Zhijun Chena, Weiguo Caoa, Jie Chena, and Yali Chena,b,
aDepartment of Chemistry, Innovative Drug Research Center, Shanghai University, Shanghai 200444, China
bKey Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R.
China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
An efficient protocol for one-step synthesis of oxadisilole-fused benzo[g]phthalazines and
naphtho[2,3-g]phthalazines by the Diels-Alder reactions and denitrogenation/deoxygenation
aromatization reactions of benzo- or naphtho-oxabicyclic alkene with 3,6-diaryl-1,2,4,5-
tetrazines in THF at room temperature for 3h. The photophysical, redox, and thermal properties
of these compounds have been determined. The proposed mechanism was also studied.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
benzo-oxabicyclic alkene
naphtho-oxabicyclic alkene
benzo[g]phthalazines
naphtho[2,3-g]phthalazines
1. Introduction
unknown compounds 3a-e and 5a-e have been determined. The
possible mechanism for the formation of product was also
suggested.
Phthalazine derivatives is an example of nitrogen
heterocycles which showed a series of biological activities and
medical applications, such as antimicrobial,1 antibacterial,2 anti-
inflammatory,3 anticancer,4 and anticonvulsant,5 activities.
Benzo[g]phthalazine derivatives have inhibitory effect to the
parasites6 or trypanosome,7 and cytotoxic activity of a potential
DNA bisintercalator.8 In addition, phthalazine derivatives as
ligands for a variety of transition metals have been used in
chemosensor or OLED materials.9 The methods to synthesize
phthalazine derivatives usually conclude with ring closing
reactions9c,10 or Diels-Alder/retro-Diels-Alder reactions of
1,2,4,5-tetrazines with alkenes or arynes.11 The Warrener Diels-
Alder/retro-Diels-Alder is an efficient approach to form
isobenzofuran from oxabicyclic alkenes with 3,6-di-2-pyridyl-
1,2,4,5-tetrazine.12 We recently interested in the chemistry of
arynes generated from benzobis(oxadisilole) and 2,3-
naphthoxadisilole under very mild conditions13, the reaction of
oxadisilole-fused oxabicyclic alkenes with 3,6-di-2-pyridyl-
1,2,4,5-tetrazine to construct oxadisilole-fused isobenzofuran
have been reported in Scheme 1.13c,f In this paper we report on a
surprising behavior of the benzo- or naphtho-oxabicyclic alkenes
(1 or 4) reacting with 3,6-diaryl-1,2,4,5-tetrazines 2a–e at room
temperature, to afford oxadisilole-fused benzo[g]phthalazines
3a–e and naphtho[2,3-g]phthalazines 5a–e (Scheme 2). The
Scheme 1. Previous work, the synthesis of oxadisilole-fused isobenzofuran
2. Results and Discussion
One-step
synthesis
of
the
oxadisilole-fused
benzo[g]phthalazines 3a–e and naphtho[2,3-g]phthalazines 5a–e
are summarized in Scheme 2. The benzo-oxabicyclic alkenes 1 or
naphtho-oxabicyclic alkenes 4 were prepared according to our
previously
reported
phenyliodination/fluoride-induced
desilylation protocol by trapping the benzyne and 2,3-naphthyne
generated from benzobis(oxadisilole) and 2,3-naphthoxadisilole
with furan, respectively.13a,b,j 3,6-diaryl-1,2,4,5-tetrazines 2a–e
were prepared according to literature procedures.14
photophysical, redox and thermal properties of these previously
———
Corresponding author. Tel.: +8621-66132797; fax: +8621-66132797; e-mail: ylchen@staff.shu.edu.cn

2
Tetrahedron
Our initial optimization studies focused on the reaction of
ACCEPTED MANUSCRIPT
oxadisilole-fused benzo-oxabicyclic alkene 1 with 3,6-diphenyl-
1,2,4,5-tetrazine 2c under different reaction conditions (Table 1).
The oxadisilole-fused benzo-oxabicyclic alkene 1 (1.0 equiv.)
reacted with 3,6-diphenyl-1,2,4,5-tetrazine 2c (1.0 equiv.) in
THF at room temperature under N2 for 3.0h, which resulted in the
formation of oxadisilole-fused benzo[g]phthalazine 3c in 36%
yield (Table 1, entry 1), while isobenzofuran was not detected.
When the amount of 2c was changed from 1.0 to 1.3, 1.5, 1.7, or
2.0 equiv., the yield of desired product 3c improved from 36% to
49, 75, 59 or 53%, respectively, the best results were obtained
when the amount of 2c was 1.5 equiv. (Table 1, entries 2-5).
When reaction time was changed to 1.5h, 4.5h or 6.0h, the
desired product 3c was formed in 52, 72, or 69% yield,
respectively (Table 1, entries 6-8), the yield of 3c has not
increased when reaction time longer than 3h. The effect of
various solvents, such as MeCN, CH2Cl2, CHCl3, Toluene, EtOH
or 1,4-dioxane at room temperature under N2 for 3.0h on this
reaction was also studied, using 1 equiv. of 1 and 1.5 equiv. of 2c,
without the improvement in the yield of 3c (Table 1, entries 9-14).
When the reaction temperature was changed from room
temperature to 0ꢀ, 45ꢀ or reflux, the yield of 3c was rather
poor (Table 1, entries 15-17). Thus the best results were obtained
when the reaction between 1 (1.0 equiv.) and 2c (1.5 equiv.) was
carried out in THF at room temperature under N2 for 3h (Table 1,
entry 3).
Scheme 2. One-step synthesis of oxadisilole-fused benzo[g]phthalazines
3a-e and naphtho[2,3-g]phthalazines 5a-e
Table 1. Optimization of reaction conditions.a
Entry 2c (equiv).
Solvent
THF
Temp. (
r.t
)
Time (h)
3.0
Yieldb (%)
36
With this result in hand, we went on to study the Diels-Alder
reactions and denitrogenation/deoxygenation aromatization
reactions of benzo-oxabicyclic alkene 1 with 3,6-diaryl-1,2,4,5-
tetrazines 2a–e in THF at room temperature under N2 for 3h. The
oxadisilole-fused benzo[g]phthalazines 3a–e were formed in
yields of 21 to 75% (Scheme 2 and Table 2).
1
1.0
1.3
1.5
1.7
2.0
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
2
THF
r.t
3.0
49
3
THF
r.t
3.0
75
As shown in Table 2, the reaction of 1 with 2a–e is quite
sensitive to the electronic nature of substituent on the 3,6-diaryl-
1,2,4,5-tetrazine moiety. The 3,6-diphenyl-1,2,4,5-tetrazine 2c
(Ar = C6H5) gave higher yield than electron-rich or deficient
compounds 2a–b or 2d–e. Isobenzofuran was not detected.
4
THF
r.t
3.0
59
5
THF
r.t
3.0
53
6
THF
r.t
1.5
52
Table 2.
O
ne-step synthesis of oxadisilole-fused
benzo[
g
]phthalazines 3a–ea.
7
THF
r.t
4.5
72
Entry
Tetrazine
Ar
Product
Yieldb (%)
21
8
THF
r.t
6.0
69
1
2
3
4
5
2a
4-OCH3C6H4
3a
9
MeCN
CH2Cl2
CHCl3
Toluene
EtOH
1,4-dioxane
THF
r.t
3.0
16
2b
2c
2d
2e
4-CH3C6H4
C6H5
3b
3c
3d
3e
48
75
20
40
10
11
12
13
14
15
16
17
r.t
3.0
38
r.t
3.0
34
4-ClC6H4
4-CF3C6H4
r.t
3.0
23
aReaction conditions:1 (1.0 equiv.), 2a-e (1.5 equiv.), THF (5.0 mL), at room
temperature under N2 for 3h
r.t
3.0
31
bIsolated yield.
r.t
3.0
47
One possible mechanistic pathway for the formation of
products 3a-e is shown in Scheme 3. The Diels-Alder reaction of
1 with 2a-e forms the corresponding adducts 6a-e. Subsequent
denitrogenation15 of adducts 6a-e and deoxygenation
aromatization reactions13j of 7a-e could lead to benzenoid
frameworks.
0
3.0
trace
19
THF
45
reflux
3.0
THF
3.0
21
aReaction conditions: 1 (1.0 equiv.) under N2
bIsolated yield.

3
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6x104
3a
3b
3c
3d
3e
5x104
4x104
3x104
2x104
14000
10500
7000
3500
0
360
380
400
420
440
460
1x104
0
250
300
350
400
450
500
Scheme 3. Possible mechanism for the formation of oxadisilole-fused
benzo[g]phthalazines 3a–e
Wavelength / nm
Furthermore,
the
Diels-Alder
reactions
and
Figure 1. Absorption spectra of 3a-e in CH2Cl2.
denitrogenation/deoxygenation aromatization reactions of
naphtho-oxabicyclic alkene 4 with 3,6-diaryl-1,2,4,5-tetrazines
2a–e in THF at room temperature under N2 for 3h were also
investigated. To our delight, naphtho[2,3-g]phthalazines 5a–e
were synthesized in yields of 16 to 89% (Scheme 2 and Table 3).
The yield of 5a (Ar = 4-OCH3C6H4) was rather poor (Table 3,
entry 1).
7x104
5a
5b
5c
5d
5e
6x104
8000
5x104
6000
4000
4x104
2000
3x104
0
Table 3. One-step synthesis of naphtho[2,3-
5a–e[a].
g
]phthalazines
420
430
440
450
460
470
480
490
500
2x104
1x104
0
Entry
Tetrazine
Ar
Product
Yield[b] (%)
300
350
400
450
500
1
2
3
4
5
2a
2b
2c
2d
2e
4-OCH3C6H4
4-CH3C6H4
C6H5
5a
16
52
89
30
87
Wavelength / nm
5b
Figure 2. Absorption spectra of 5a–e in CH2Cl2.
The photoluminescence spectra of 3a–e and 5a–e in CH2Cl2
show blue emission with maxima in the range of 497 to 509 nm
for 3a–e, and yellow-orange emission with maxima in the range
of 580 to 615 nm for 5a–e (Figures 3 and 4, and Table 4). A
substituent effect was also found for the emission maxima in 3a–
e and 5a–e. The electron-donating or -withdrawing substituent in
3a,b,d,e or 5a,b,d,e (Ar = OCH3C6H4, CH3C6H4, ClC6H4,
CF3C6H4) resulted in a red shift of about 9 nm (3a or 3e) or 3 nm
(3d) and blue shift of about 3 nm (3b) compared to 3c (Ar =
C6H5) in 3a–e; blue shift of about 14 nm (5a) or 6 nm (5b) and
red shift of about 8 nm (5d) or 11 nm (5e) compared to 5c (Ar =
C6H5) in 5a–e. The fluorescence quantum yields (Φ) measured in
CH2Cl2 by using quinine as the reference for 3a–e and
fluorescein as the reference for 5a–e are in the range of 7 to 35%
for 3a–e and 2 to 10% for 5a–e, respectively. Thus, 3b–d could
potentially be used as blue emitters for organic light-emitting
diode (OLED) applications. In addition, the thermal properties of
3a–e and 5a–e were determined by thermal gravimetric analysis
(TGA). They showed good thermal stabilities, ranging from 218
to 400ꢀ for 3a–e and 317 to 380ꢀ for 5a–e.
5c
4-ClC6H4
4-CF3C6H4
5d
5e
aReaction conditions:4 (1.0 equiv.), 2a-e (1.5 equiv.), THF (5.0 mL), at
room temperature under N2 for 3h
bIsolated yield.
The structures of compounds 3a–e and 5a–e were established
by 1H and 13C NMR spectroscopy, IR spectroscopy, and low- and
high-resolution mass spectrometry. The data are in good
agreement with the expected structures.
The absorption spectra for 3a–e and 5a–e were recorded in
CH2Cl2, and the results are shown in Figures 1 and 2, and Table 4.
The long-wavelength absorption bands were in the range 378 to
435 nm for 3a–e, and 482 to 488 nm for 5a–e. A substituent
effect was observed in both 3a–e and 5a–e series. The electron-
withdrawing or donating groups in 3a,b,d and 5a,d,e cause
bathochromic shifts in absorption maximum compared to the
respective parent compound (i.e., 3c or 5c; Ar = C6H5) except 3e.
Table 4. Summary of optical measurements and thermal
properties of 3a–e and 5a–e.
Compd. λabs a,b/nm
λem a,c /nm
ΦFLa,b [eV]
Tm/Tdec(℃)
max
max
(εmax/104M-1cm-1)
3a
3b
3c
3d
435 (0.89)
509
497
500
503
0.10
0.35
0.35
0.27
149/218
118/400
246/353
126/388
429 (0.55)
410 (0.52)
414 (0.60)

4
3e
Tetrahedron
Table 5. Summary of oxidation potential and HOMO and
ACC2E66P/3T98ED MANUSCRIPT
378 (0.52)
484 (0.25)
482 (0.36)
482 (0.52)
486 (0.19)
488 (0.29)
509
580
588
594
602
615
0.07
0.10
0.08
0.06
0.03
0.02
LUMO energy levels of 3a–e and 5a–e.
5a
5b
5c
5d
5e
222/318
198/326
259/366
179/317
273/380
Compd. Eox[a] [V]
3a 0.95
3b 1.08
HOMOb [eV] Band gapc [eV]
-5.35 2.58
-5.48 2.64
LUMOd[eV]
-2.77
-2.84
3c
3d
3b
5a
5b
5c
5d
5e
0.91
0.85
0.93
1.45
1.46
1.39
1.51
1.53
-5.31
-5.25
-5.33
-5.85
-5.86
-5.79
-5.91
-5.93
2.53
2.53
2.70
2.18
2.30
2.34
2.21
2.20
-2.78
-2.72
aMeasured in CH2Cl2.
-2.63
bExcited at the absorption maximum.
cExcited at the emission maximum.
-3.67
dUsing quinine in 0.1N H2SO4 (Φ365=0.54) as
benzo[g]phthalazines 3a-e and fluorescein in 0.1N NaOH (Φ470=0.91) as
standard for naphtho[2,3-g]phthalazines 5a-e
a
standard for
-3.56
-3.45
1.0
3a
3b
3c
3d
3e
-3.70
0.8
-3.73
0.6
aEox was estimated by cyclic voltammetry in CH2Cl2 with a platinum disc
as the working electrode, a platinum wire as the counter electrode, and a
standard calomel electrode (SCE) as the reference electrode. An agar salt
bridge connected the compound solution, ferrocene was used as an
external standard, and Bu4NPF6 (0.1M) was used as electrolyte. Scan rate
= 100 mV/s; E1/2(Fc/Fc+) = 0.40 V versus SCE, calculated with ferrocene
(4.8 eV vs vacuum).
0.4
0.2
0.0
450
500
550
600
Wavelength / nm
bHOMO = -[Eox-[E1/2(Fc/Fc+)]+4.8].
Figure 3. Emission spectra of 3a-e in CH2Cl2
.
cEstimated from the absorption edge in CH2Cl2.
dLUMO = HOMO + Optical band gap.
5a
5b
5c
5d
5e
1.0
0.8
0.6
0.4
0.2
0.0
3. Conclusions
One step synthesis of two new series of oxadisilole-fused
benzo[g]phthalazines 3a–e and naphtho[2,3-g]phthalazines 5a–e
by the Diels-Alder reactions and denitrogenation /deoxygenation
aromatization reactions of benzo- or naphtho-oxabicyclic alkene
(1 or 4) with 3,6-diaryl-1,2,4,5-tetrazines 2a–e under mild
condition. They were used as the building blocks for the simple
preparation of fused heterocyclic compounds. The photophysical,
redox, and thermal properties of 3a–e and 5a–e have been
determined. Compounds 3b–d show potential applications used
as blue emitters for OLED due to their high fluorescence
quantum yields and thermal stabilities.
540
560
580
600
620
640
660
Wavelength / nm
Figure 4. Emission spectra of 5a-e in CH2Cl2.
The redox properties as well as the HOMO (highest-occupied
molecular orbital) and LUMO (lowest-unoccupied molecular
orbital) energy levels of 3a–e and 5a–e are tabulated in Table 5.
The redox properties of 3a–e and 5a–e were studied by cyclic
voltammetry in a three-electrode cell in CH2Cl2 with Bu4NPF6
(0.1M) as the supporting electrolyte. All of the potentials
reported are referenced to Fc/Fc+ as standard. In contrast to the
optical properties, the substituent on the aryl ring has no
significant effect on the oxidation potential (Eox), which occurs
between 0.85 and 1.08 V for 3a–e and between 1.39 and 1.53 V
for 5a–e. The HOMO energy values were calculated according to
the equation reported by Janietz and Schmidt,16 and the LUMO
energy levels were obtained by subtraction of the optical band
gap from the HOMO.
4. Experimental section
4.1. General Methods
Purification was effected by silica gel column chromatography
(300-400 mesh silica gel) using mixtures of reagent-grade
EtOAc/petroleum ether (PE, 60-80 ) as the eluents. NMR
spectra were recorded at 500 MHz for H and 125 MHz for 13C
1
with CDCl3 as the solvent by using a Bruker DRX-500 NMR
spectrometer. Chemical shifts are reported in parts per million
(ppm on) the δ scale relative to the residual resonance of CHCl3
1
(δ = 7.26 ppm for H and 77.00 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 cm-1 (KBr disc). Low-resolution mass spectra were recorded
with an Agilent spectrometer in EI or API-ES mode and are

5
reported as m/z values. High-resolution mass spectra were
4.2.5. 7,8-Oxadisilole-1,4-bis(4-trifluoromethanephenyl)
benzo[g]phthalazine (3e).
ACCEPTED MANUSCRIPT
recorded with a Waters Micromass GCT instrument. The
fluorescence quantum yields in solution were determined by
dilution method using quinine in 1.0N H2SO4 (Φ365 = 0.54) and
fluorescein in 0.1N NaOH (Φ470 = 0.91) as standard with an LS-
55 spectrometer. Thermal stabilities were determined using a
thermal gravimetric analyzer with a heating rate of 10ꢀ min-1
under N2.
Yellow solid, 72 mg, 40%, m.p. 265-267°C. 1H NMR (500 MHz,
CDCl3): δ 0.45 (s, 12H, SiMe2), 7.93 (d, J = 8.0 Hz, 4H, Ar-H),
8.04 (d, J = 8.0 Hz, 4H, Ar-H), 8.33 (s, 2H, Ar-H), 8.66 (s, 2H,
Ar-H) ppm. 13C NMR (125 MHz, CDCl3): δ 1.0, 122.7, 124.0 (q,
J = 270.6 Hz, CF3), 125.7 (q, J = 3.6 Hz), 127.2, 130.5, 131.7 (q,
J = 32.3 Hz), 132.3, 134.7, 140.0, 147.6, 159.0 ppm. 19F-NMR
(470 MHz, CDCl3): δ -62.63 (s, CF3). IR (KBr): 3051, 2959,
1617, 729, 692 cm-1. MS (EI) m/z (%): 599 (100, [M+H]+).
HRMS (EI) calcd for C30H24F6N2OSi2 [M+H]+: 599.1404, found
599.1397.
4.2. General procedure of oxadisilole-fused benzo[g]
phthalazines 3a-e and naphtho[2,3-g]phthalazines 5a-e.
Oxadisilole-fused benzo-oxabicyclic alkene 1 or naphtho-
oxabicyclic alkene 4 (0.3 mmol) and 3,6-diary-1,2,4,5-tetrazines
2a-e (0.45 mmol) were dissolved in THF (8 mL). The reaction
mixture was stirred at room temperature for 3h under N2. The
solvent was removed under the reduced pressure. The crude
product was purified by column chromatography on silica gel
using a gradient 5 to 25% EtOAc in PE (60-80℃) as the eluent to
afford oxadisilole-fused benzo[g]phthalazines 3a-e and
naphtho[2,3-g]phthalazines 5a-e.
4.2.6. 1,4-Bis(4-methoxyphenyl) naphtho[2,3-g]phthalazine (5a).
1
Brown solid, 21 mg, 16%, m.p. 222-223℃. H NMR (500 MHz,
CDCl3)ꢁδ 3.97 (s, 6H, OCH3), 7.18 (d, J = 9.0 Hz, 4H, OCH3),
7.52-7.54 (m, 2H, Ar-H), 7.90 (d, J = 8.5 Hz, 4H, Ar-H), 8.03-
8.05 (m, 2H, Ar-H), 8.75 (s, 2H, Ar-H), 8.96 (s, 2H, Ar-H) ppm.
13C NMR (125 MHz, CDCl3)ꢁ δ 55.5, 114.1, 122.3, 126.8,
128.1, 128.29, 128.34, 129.1, 131.6, 131.8, 132.9, 158.9, 160.8
ppm. IR (KBr): 3049, 2958, 1608, 735, 683 cm-1. MS (EI) m/z
(%): 443 (100, [M+H]+); HRMS (EI) calcd for C30H22N2O2 [M]+:
442.1681, found 442.1678.
4.2.1. 7,8-Oxadisilole-1,4-bis(4-methoxyphenyl)
benzo[g]phthalazine (3a).
1
Yellow solid, 33 mg, 21%, m.p. 148-150℃. H NMR (500 MHz,
4.2.7. 1,4-Bis(4-methylphenyl) naphtho[2,3-g]phthalazine (5b).
CDCl3)ꢁδ 0.44 (s, 12H, SiMe2), 3.96 (s, 6H, OCH3), 7.17 (d, J =
9.0 Hz, 4H, Ar-H), 7.87 (d, J = 8.5 Hz, 4H, Ar-H), 8.30 (s, 2H,
Ar-H), 8.75 (s, 2H, Ar-H) ppm. 13C NMR (125 MHz, CDCl3)ꢁδ
1.1, 55.5, 114.1, 123.4, 127.5, 129.2, 131.6, 132.4, 134.4, 146.5,
158.8, 160.7 ppm. IR (KBr): 3051, 2955, 2837, 1606, 793 cm-1.
MS (EI) m/z (%): 523 (100, [M+H]+). HRMS (EI) calcd for
C30H30N2O3Si2 [M]+: 522.1795, found 522.1798.
1
Orange solid, 64 mg, 52%, m.p. 197-198℃. H NMR (500 MHz,
CDCl3): δ 2.54 (s, 6H, CH3), 7.46 (d, J = 8.0 Hz, 4H, Ar-H),
7.49-7.51 (m, 2H, Ar-H), 7.83 (d, J = 8.0 Hz, 4H, Ar-H), 7.99-
8.01 (m, 2H, Ar-H), 8.69 (s, 2H, Ar-H), 8.91 (s, 2H, Ar-H) ppm.
13C NMR (125 MHz, CDCl3): δ 21.5, 122.2, 126.7, 128.1, 128.2,
128.3, 129.3, 130.1, 131.7, 132.9, 139.4, 159.4 ppm. IR (KBr):
3049, 3021, 1611, 722, 677 m-1; MS (EI) m/z (%): 411 (100,
[M+H]+); HRMS (EI) calcd for C30H22N2 [M]+: 410.1783, found:
410.1781.
4.2.2. 7,8-Oxadisilole-1,4-bis(4-methylphenyl)
benzo[g]phthalazine (3b).
1
Yellow solid, 71 mg, 48%, m.p. 117-119℃. H NMR (500 MHz,
CDCl3)ꢁ1H NMR (500 MHz, CDCl3): δ 0.44 (s, 12H, SiMe2),
2.53 (s, 6H, CH3), 7.44 (d, J = 7.5 Hz, 4H, Ar-H), 7.80 (d, J = 7.5
Hz, 4H, Ar-H), 8.29 (s, 2H, Ar-H), 8.73 (s, 2H, Ar-H) ppm. 13C
NMR (125 MHz, CDCl3): δ 1.1, 21.5, 123.3, 127.5, 129.3, 130.1,
132.4, 133.8, 134.4, 139.4, 146.5, 159.4 ppm. IR (KBr): 3028,
2851, 1447, 725, 664 cm-1; MS (EI) m/z (%): 491 (100, [M+H]+).
HRMS (EI) calcd for C30H30N2OSi2 [M]+: 490.1897, found
490.1896.
4.2.8. 1,4-Diphenyl naphtho[2,3-g]phthalazine (5c).
Orange solid, 102 mg, 89%, m.p. 258-260℃. 1H NMR (500 MHz,
CDCl3): δ 7.50-7.52 (m, 2H, Ar-H), 7.64-7.68 (m, 6H, Ar-H),
7.93-7.95 (m, 4H, Ar-H), 8.00-8.02 (m, 2H, Ar-H), 8.70 (s, 2H,
Ar-H), 8.90 (s, 2H, Ar-H) ppm; 13C NMR (125 MHz, CDCl3): δ
122.0, 126.8, 128.1, 128.3, 128.6, 129.5, 130.1, 131.7, 132.9,
136.7, 159.7 ppm. IR (KBr): 3051, 2923, 1547, 701, 673 m-1; MS
(EI) m/z (%): 383 (100, [M+H]+); HRMS (EI) calcd for C28H18N2
[M]+: 382.1470, found 382.1467.
4.2.3. 7,8-Oxadisilole-1,4-diphenyl benzo[g]phthalazine (3c).
Yellow solid, 104 mg, 75%, m.p. 245-246℃. 1H NMR (500 MHz,
CDCl3): δ 0.44 (s, 12H, SiMe2), 7.62-7.66 (m, 6H, Ar-H), 7.90-
7.92 (m, 6H, Ar-H), 8.30 (s, 2H, Ar-H), 8.72 (s, 2H, Ar-H) ppm.
13C NMR (125 MHz, CDCl3): δ 1.1, 123.2, 127.5, 128.6, 129.4,
130.2, 132.4, 134.4, 136.7, 146.7, 159.6 ppm. IR (KBr): 3056,
2954, 1656, 765, 699 cm-1. MS (EI) m/z (%): 463 (100, [M+H]+);
HRMS (EI) calcd for C28H26N2OSi2 [M]+: 462.1584, found
462.1580.
4.2.9. 1,4-Bis(4-chlorophenyl) naphtho[2,3-g]phthalazine (5d).
1
Brown solid, 41 mg, 30%, m.p. 178-180℃. H NMR (500 MHz,
CDCl3): δ 7.55-7.57 (m, 2H, Ar-H), 7.64 (d, J = 8.5 Hz, 4H, Ar-
H), 7.88 (d, J = 8.5 Hz, 4H, Ar-H), 8.05-8.07 (m, 2H, Ar-H), 8.77
(s, 2H, Ar-H), 8.89 (s, 2H, Ar-H) ppm. 13C NMR (125 MHz,
CDCl3): δ 121.8, 127.1, 128.16, 128.23, 128.3, 129.0, 131.4,
131.8, 133.2, 134.9, 135.9, 158.9 ppm. IR (KBr): 3062, 2924,
1596, 725, 675 m-1; MS (EI) m/z (%): 451 (100, [M+H]+);
HRMS (EI) calcd for C28H16Cl2N2 [M]+: 450.0691, found:
450.0691.
4.2.4. 7,8-Oxadisilole-1,4-bis(4-chlorophenyl)
benzo[g]phthalazine (3d).
1
4.2.10. 1,4-Bis(4-trifluoromethanephenyl)
naphtho[2,3-
Yellow solid, 32 mg, 20%, m.p. 125-127℃. H NMR (500 MHz,
g]phthalazine (5e).
CDCl3): δ 0.45 (s, 12H, SiMe2), 7.63 (d, J = 8.5 Hz, 4H, Ar-H),
7.85 (d, J = 8.0 Hz, 4H, Ar-H), 8.31 (s, 2H, Ar-H), 8.67 (s, 2H,
Ar-H) ppm. 13C NMR (125 MHz, CDCl3): δ 1.1, 122.9, 127.3,
129.0, 131.5, 132.3, 134.5, 135.0, 135.8, 147.2, 158.8 ppm. IR
(KBr): 3059, 2957, 1594, 722, 657 cm-1. MS (EI) m/z (%): 531
(100, [M+H]+); HRMS (EI) calcd for C28H24Cl2N2OSi2 [M]+:
530.0804, found 530.0803.
Orange solid, 135 mg, 87%, m.p. 272-273℃. 1H NMR (500 MHz,
CDCl3): δ 7.56-7.58 (m, 2H, Ar-H), 7.94 (d, J = 8.0 Hz, 4H, Ar-
H), 8.07 (d, J = 8.5 Hz, 6H, Ar-H), 8.79 (s, 2H, Ar-H), 8.87 (s,
2H, Ar-H) ppm. 13C NMR (125 MHz, CDCl3): δ 121.6, 124.1 (q,
J = 270.6 Hz), 125.7 (q, J = 3.6 Hz), 127.3, 128.1, 128.3, 128.4,
130.5, 131.7 (q, J = 32.6 Hz), 131.8, 133.3, 140.0, 159.1 ppm.
19F-NMR (470 MHz, CDCl3): δ -62.59 (s, CF3). IR (KBr): 3071,

6
Tetrahedron
ACCEPTED MANUSCRIPT
2924, 1547, 708, 680 cm-1. MS (EI) m/z (%): 519 (100,
Tetrahedron, 2005, 61, 1545–1550. (c) Girardot, M.; Nomak, R.;
[M+H]+). HRMS (EI) calcd for C30H16F6N2 [M]+: 518.1218,
found 518.1216.
Snyder, J. K. J. Org. Chem. 1998, 63, 10063–10068. (d) Li, J. B.;
Gao, J. K.; Xiong, W. W.; Zhang, Q. C. Tetrahedron Lett. 2014,
55, 4346–4349. (e) Suh, S. E.; Barros, S. A.; Chenoweth, D. M.
Chem. Sci. 2015, 6, 5128–5132.
Acknowledgments
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Warrener, R. N.; Hammer, B. C,; Russell, R. A. J. Chem. Soc.,
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We are grateful to the National Natural Science Foundation of
China (NSFC) (No. 21272146) for financial support.
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file. That file can then be transformed into PDF format and
submitted along with the manuscript and graphic files to the
appropriate editorial office.
10. (a) Dong, C.; Liao, Z. Q.; Xu, X. Y.; Zhou, H. B. J. Heterocyclic.
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Lett. 2013, 54, 7056–7058.
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