Cycloaddition of nitrones with arynes generated from benzobisoxadisilole or 2,3-naphthoxadisilole

Article abstract of DOI:10.1016/j.tet.2009.11.097

1,3-Dipolar cycloaddition of nitrones with arynes generated in situ from benzobisoxadisilole or 2,3-naphthoxadisilole afforded the oxadisilole fused benzo[d]isoxazoline or the naphtho[2,3-d]isoxazoline derivatives at room temperature in good yields.

Full text of DOI:10.1016/j.tet.2009.11.097

Tetrahedron 66 (2010) 578–582
Contents lists available at ScienceDirect
Tetrahedron
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Cycloaddition of nitrones with arynes generated from benzobisoxadisilole
or 2,3-naphthoxadisilole
,
a
a
,
,
*
Kaicheng Wu a, Yali Chen a , Yibei Lin , Weiguo Cao b, Min Zhang a, Jie Chen a, Albert W.M. Lee c
*
a Department of Chemistry, Shanghai University, No.99 Shangda Road, Shanghai 200444, PR China
b State Key Laboratory of Organometallic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China
c Department of Chemistry and Centre for Advanced Luminescence Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 October 2009
Received in revised form 15 November 2009
Accepted 24 November 2009
Available online 26 November 2009
1,3-Dipolar cycloaddition of nitrones with arynes generated in situ from benzobisoxadisilole or
2,3-naphthoxadisilole afforded the oxadisilole fused benzo[d]isoxazoline or the naphtho[2,3-d]isoxazo-
line derivatives at room temperature in good yields.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
1,3-Dipolar cycloaddition
Nitrone
Aryne
Oxadisilole fused benzo[d]isoxazoline
Naphtho[2,3-d]isoxazoline
1. Introduction
2. Results and discussion
Benzoisoxazolidine derivatives are important heterocycle com-
pounds. They have been widely used as the building blocks of
bioactive substances, intermediate of chiral pharmaceuticals and
natural products.1 1,3-Dipolar cycloaddition is one of the most
useful methods for synthesizing heterocycles.2 However, only few
examples are reported in the literatures on the 1,3-dipolar cyclo-
addition of nitrones with arynes.1a,3 Aryne is an important in-
termediate and synthon in organic synthesis.4 Recently, we
explored the aryne generation chemistry from benzobisox-
adisiloles, benzotrisoxadisilole, and 2,3-naphthoxadisilole. We
found that benzobisoxadisiloles can serve as the synthetic equiva-
lents of benzdiyne.5 The chemistry was further extended to the
synthesis and isolation of oxadisilole fused isobenzofurans and
isoindoles, and their applications in the preparation of functional
acenes and benzoquinones.6 With this motif in mind, herein, we
describe the 1,3-dipolar cycloaddition reaction of nitrones with
arynes generated in situ from benzobisoxadisilole or 2,3-naph-
thoxadisilole. Oxadisilole fused benzo[d]isoxazoline or naph-
tho[2,3-d]isoxazoline derivatives were obtained in good yields
under very mild reaction conditions.
The preparation of the oxadisilole fused benzo[d]isoxazoline de-
rivatives 5a–g or the naphtho[2,3-d]isoxazoline 9a–e are outlined in
Schemes 1 and 3. Arynes 3 and 8 were generated from benzobis-
oxadisilole 1 and 2,3-naphthoxadisilole 6, respectively through our
previously reported phenyliodination fluoride induced desilylation
protocol.5 Trapping benzyne 3 and naphthyne 8 at roomtemperature
with nitrons 4a–g via 1,3-dipolar cycloaddition reactions afforded
the oxadisilole fused benzo[d]isoxazoline derivatives 5a–g and
naphtho[2,3-d]isoxazoline 9a–e in good yields. Nitrones 4a–g were
prepared according to the literature procedures.7,8
In situ phenyliodination of 1 with a 1.5:3 mixture of phenyl-
iodium diacetate (PhI(OAc)2) and trifluoromethanesulfonic acid
(TfOH) took place readily at room temperature in CH2Cl2 (Scheme
1). Without isolation of the ring-opened iodination intermediate 2,
benzyne 3 could be generated in situ upon treatment with a 1.0 M
THF solution of tetrabutylammonium fluoride (n-Bu4NF). Trapping
experiments were carried out with 5 equiv of nitrone 4c (X¼H) at
room temperature to afford 68% isolated yields of the oxadisilole
fused benzo[d]isoxazoline derivative 5c in this three steps reaction
(Scheme 1 and Table 1, entry 4). We also observed that using less
than 5 equivalents of nitrone 4c, the yields were decreased (Table 1,
entries 1–3). However, increased the amount to 10 equivalents, the
yield of 5c was not improved (Table 1, entry 5). If CH3CN was used
as solvent (commonly used in preparing precursor, [o-(trimethyl)
phenyl]-iodonium triflate),9 the 1,3-dipolar cycloaddition reaction
* Corresponding authors. Tel.: þ86 21 66132190; fax: þ86 21 6613 4856.
E-mail address: ylchen@staff.shu.edu.cn (Y. Chen).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.11.097

K. Wu et al. / Tetrahedron 66 (2010) 578–582
579
Si
Si
Si(OH)Me2
I(Ph)OTf
Si
Si
Si
Si
Si
Si
PhI(OAc)2, TfOH
n-Bu4NF/THF
i-Pr2NH, rt
O
O
O
O
0
oC to rt
CH Cl ,
2
2
1
3
2
Z
O
N
X
X
4a-e
Si
Si
O
N
O
or
Z
Y
N
N
O
or
Y
Si
5a-e
a: X = OCH3
b: X = CH3
c: X = H
O
N
Si
O
N
5f-g
d: X = Cl
e: X = NO2
f: Y = CH3, Z = OCH3
g: Y = OCH3, Z = CH3
4f-g
Scheme 1.
Z
Z
Z
Si
Si
Y
N
N O
O
N
O
N
Y
N
+
Y
N
O
Si
Si
O
Si
Si
O
4f-g
3
5f-g
Scheme 2.
Si(OH)Me2
I(Ph)OTf
Si
Si
n-Bu4NF/THF
i-Pr2NH, rt
PhI(OAc)2, TfOH
O
0 oC to rt
CH2Cl2,
6
8
7
O
N
X
O
N
a: X = OCH3
b: X = CH3
c: X = H
X
4a-e
d: X = Cl
e: X = NO2
9a-e
Scheme 3.
of benzyne 3 with nitron 4c was unsuccessful. It is worth noting
that the remaining material 4c could be recycled.
We further studied the 1,3-dipolar cycloaddition reaction of
benzyne 3 generated in situ from the benzobisoxadisilole 1 with
various nitrones 4a–e at room temperature. The oxadisilole fused
benzo[d]isoxazoline derivatives 5a–e were formed in 50–78%
yields (Scheme 1 and Table 2, entries 1–5). As shown from the
chemical yields, this 1,3-dipolar cycloaddition of nitrone to ben-
zyne 3 is rather insensitive in the electronic nature (X¼OCH3, CH3,
H, Cl, NO2) of the substituents on the nitrones. For cyclic nitrones
4f–g, the cis cycloadducts 5f–g could be obtained in 30–35% yields,
the phenyl and aryl group were on the same side of the benzobi-
cyclic ring system (Scheme 1 and Table 3, entries 1 and 2). The
possible reaction mechanism shown in Scheme 2 would account for
the high stereoselectivity. The fact that only cis isomer was
obtained demonstrated that the reaction was a concerted process
guided with the Woodward–Hoffman rule. When the molecule of
benzyne 3 approaches planar dipole N-oxide 4f–g, the concerted
reaction prefers to approach the dipole from the less sterically
hindered side of the plane and thus afforded cis iomers 5f–g.8b,10 As
compared with the acyclic nitrones 4a–e, the cycloadducts 5f–g
Table 1
Cycloaddition of nitrone 4c with benzyne 3 generated from benzobisoxadisilole 1 at
room temperature
Entry
Molar ratio of 1 to 4c
Yielda of 5c (%)
1
2
3
4
5
1:1
1:2
1:3
1:5
1:10
30
54
55
68
65
a
Isolated yields.

580
K. Wu et al. / Tetrahedron 66 (2010) 578–582
spectrometer (500 MHz for 1H and 125 MHz for 13C) with CDCl3 as
the solvent and TMS as internal reference and expressed in ppm.
Coupling constants (J) are reported in Hertz. Low-resolution mass
spectra were obtained on a Agilent LC/MSD SL spectrometer in EI
mode and reported as m/z. High-resolution mass spectra (HRMS)
were recorded on a Waters Micromass GCT instrument. Elemental
analyses were measured on the Elemental Vario EL III. Column
chromatography was performed using silica gel (G or GF254). PE
indicates petroleum ether (bp 60–80 ꢁC).
Table 2
Cycloaddition of nitrones 4a–e with benzyne 3 generated from benzobisoxadisilole
1 at room temperature
Entry
Nitrone
X
Product
Yielda (%)
1
2
3
4
5
4a
4b
4c
4d
4e
OCH3
CH3
H
Cl
NO2
5a
5b
5c
5d
5e
50
78
68
61
61
a
Isolated yields.
3.2. General procedure for the preparation of nitrones
3.2.1. General procedure for the preparation of nitrones 4a–e7. A
mixture of p-substituted benzaldehyde (0.02 mol) and hydroxyl-
amine hydrochloride (2.07 g, 0.03 mol) in 15 mL of MeOH was
stirred for 1 h, then the solvent was evaporated and the residue was
extracted with ethyl acetate (25 mLꢂ3). The combined organic
phase was dried over anhydrous MgSO4, filtered and evaporated.
The crude p-substituted benzaldehyde oxime was used without
further purification.
Table 3
Cycloaddition of nitrones 4f–g with benzyne 3 generated from benzobisoxadisilole 1
at room temperature
Entry
Nitrone
Y
Z
Product
Yielda (%)
1
2
4f
4g
CH3
OCH3
OCH3
CH3
5f
5g
35
30
a
Isolated yields.
To a solution of p-substituted benzaldehyde oxime (10.0 mmol)
and NaBH3CN (1.07 g, 17.0 mmol) in 10 mL of MeOH was added
a trace of bromocresol green as an indicator. Concentrated HCl was
then added dropwise with stirring to maintain a yellow color
(pHw4). The reaction mixture was stirred at room temperature for
24 h. The mixture was then made basic with 10% NaOH and it was
extracted with CH2Cl2. The organic layer was dried over anhydrous
MgSO4, the solvent was evaporated, and the solid residue N-(p-
substituted benzyl)hydroxylamine was obtained.
To a stirred solution of N-(p-substituted benzyl)hydroxylamine
(5 mmol) in 3 mL of CH2Cl2 was treated with benzaldehyde (0.8 mL,
7.5 mmol) and anhydrous MgSO4 (1.2 g, 10.0 mmol). The mixture
was vigorously stirred at room temperature for overnight, the re-
action mixture was filtered and the filtrate evaporated under re-
duced pressure, the residue was purified by column
chromatography on silica gel using a gradient of 10–20% EtOAc in
petroleum ether (60–80 ꢁC) as eluent to afford the nitrones 4a–e.
were formed in lower yields. It may be due to the steric effects. The
structures of compounds 5f–g are interesting for synthesizing
heterocycles.
Furthermore, 1,3-dipolar cycloaddition reactions of naphthyne 8
generated in situ from the 2,3-naphthoxadisilole 6 with various
nitrones 4a–e at room temperature were also investigated. The
naphtho[2,3-d]isoxazoline derivatives 9a–e were formed in good
yields (Scheme 3 and Table 4, entries 1–5). The structures of all the
cycloadducts 5a–g and 9a–e, were established by 1H and 13C NMR,
MS, IR, elemental analysis and HRMS.
Table 4
Cycloaddition of nitrones 4a–e with 2,3-naphthyne 8 generated from 2,3-naph-
thoxadisilole 6 at room temperature
Entry
Nitrone
X
Product
Yielda (%)
1
2
3
4
5
4a
4b
4c
4d
4e
OCH3
CH3
H
Cl
NO2
9a
9b
9c
9d
9e
81
66
84
73
76
3.2.2. General procedure for the preparation of nitrones 4f–g8. A
mixture of a-bromoacetophenone (3.96 g, 0.02 mol) and hydroxyl
amine hydrochloride (2.07 g, 0.03 mol) in 15 mL of MeOH was
stirred for 1 h, then the solvent was evaporated and the residue was
extracted with ethyl acetate (25 mLꢂ3). The combined organic
phase was dried over anhydrous MgSO4, filtered and evaporated.
a
Isolated yields.
In conclusion, we have investigated 1,3-dipolar cycloaddition of
nitrones 4a–g with arynes 3 and 8 generated in situ from the
benzobisoxadisilole 1 or 2,3-naphthoxadisilole 6, respectively.
Oxadisilole fused benzo[d]isoxazoline 5a–g and naphtho[2,3-
d]isoxazoline derivatives 9a–e were synthesized in good yields
under very mild reaction conditions. The simplicity of these pro-
cedures and good yields should offer great opportunities for the
synthesis of important heterocyclic compounds.
The crude a-bromoacetophenone oxime was used without further
purification.
The solid
a-bromoacetophenone oxime (2.5 mmol) was added
to a solution of aromatic amine (5.0 mmol) in 10 mL of absolute
ethanol and the mixture was stirred for 20 min followed by adding
aromatic aldehyde (5.0 mmol) and then stirred for 3 h at room
temperature. The formed precipitate was collected by filtration and
recrystallized from acetone to get cycloadducts 4f–g.
3. Experimental
3.1. General
3.3. General procedure for the preparation of oxadisilole
fused benzo[d]isoxazoline derivatives 5a–g and naphtho
[2,3-d]isoxazoline 9a–e
All non-aqueous reactions were carried out in oven-dried
glassware under a slight positive pressure of nitrogen unless oth-
erwise noted. All reagents and solvents were obtained from com-
mercial sources and used without purification, unless indicated
otherwise. Solvents were reagent grade and purified by standard
techniques: THF was distilled from Na-benzophenone; CH2Cl2 was
distilled from CaH2. Melting points were determined on a WRS-1
digital melting point apparatus and are uncorrected. IR spectra
were determined on a Bruker spectrometer and expressed in cmꢀ1
(KBr disc). NMR spectra were recorded on a Bruker DRX-500 NMR
Trifluoromethanesulfonic acid (0.27 mL, 3.0 mmol) was added
with a syringe to a stirred solution of phenyliodium diacetate
(493 mg, 1.5 mmol in 10 mL of CH2Cl2) at 0 ꢁC. The mixture was
stirred under N2 for 1 h at 0 ꢁC and for 2 h at room temperature. The
clear yellow solution was cooled again to 0 ꢁC followed by dropwise
addition of a cold (0 ꢁC) solution of the benzobisoxadisilole 1 (or
2,3-naphthoxadisilole 6) (1.0 mmol in 5 mL of CH2Cl2). The mixture
was stirred for 0.5 h at 0 ꢁC and warmed up to room temperature.
After benzobisoxadisilole
1
(or 2,3-naphthoxadisilole 6)

K. Wu et al. / Tetrahedron 66 (2010) 578–582
581
disappeared (monitored by TLC), diisopropylamine (0.35 mL,
2.5 mmol) and nitrones 4 (5.0 mmol) were added followed by
a solution of tetrabutylammonium fluoride (2.5 mL, 2.5 mmol,
1.0 M solution in THF). The mixture was stirred under N2 for 5 h at
room temperature. The organic solvent was removed under re-
duced pressure. The crude product was purified by column chro-
matography on silica gel using a gradient of 2–5% EtOAc in
petroleum ether (60–80 ꢁC) as eluent to afford cycloadducts 5a–g
and 9a–e.
144.6, 147.7, 150.6, 157.3; IR (KBr) 2955,1604, 1556, 1521, 1450, 1346,
1252, 1100, 927, 841 cmꢀ1; MS m/z (%) (EI): 462.2 (Mþ, 81), 385.2
(82), 326.2 (100), 311.1 (60); Anal. Calcd for C24H26N2O4Si2: C, 62.31;
H, 5.66; N, 6.06; Found: C, 62.07; H, 5.69; N, 6.02.
3.3.6. Cycloadduct 5f from cycloaddition of nitrone 4f with benzyne 3
generated from benzobisoxadisilole 1. As a white solid; mp 138–
140 ꢁC; 1H NMR (500 MHz, CDCl3)
d 0.32 (s, 3H), 0.33 (s, 3H), 0.360
(s, 3H), 0.364 (s, 3H), 2.2 (s, 3H), 3.77 (s, 3H), 4.37 (d, J¼9.5 Hz, 1H),
4.42 (d, J¼9.5 Hz, 1H), 5.75 (s, 1H), 6.49 (d, J¼8.5 Hz, 2H), 6.82–6.84
(m, 2H), 6.94 (d, J¼8.5 Hz, 2H), 7.02 (s, 1H), 7.23–7.24 (m, 1H),
7.29–7.32 (m, 2H), 7.36–7.38 (m, 2H), 7.43 (s, 1H), 7.56–7.58 (m, 2H);
3.3.1. 2-(4-Methoxybenzyl)-3-phenyl-5,6-oxadisilole fused benzo [d]
isoxazolidine (5a). As a white solid; mp 94–95 ꢁC; 1H NMR
(500 MHz, CDCl3)
d
0.27 (s, 3H), 0.31 (s, 3H), 0.33 (s, 3H), 0.35
13C NMR (125 MHz, CDCl3)
d 1.08, 1.16, 1.51, 1.53, 21.2, 55.3, 61.0,
(s, 3H), 3.81 (s, 3H), 4.10 (d, J¼13.5 Hz, 1H), 4.32 (d, J¼13.0 Hz, 1H),
77.7, 86.3, 110.6, 114.0, 114.4, 125.98, 126.03, 127.4, 127.6, 128.6,
128.9, 129.6, 130.9, 133.8, 141.1, 142.4, 143.6, 150.5, 157.3, 159.6; IR
(KBr) 2952, 1614, 1516, 1253, 1103, 1036, 930, 845 cmꢀ1; HRMS: m/z
[M]þ calcd for C33H36N2O3Si2: 564.2265; found 564.2263.
5.33 (s, 1H), 6.87 (d, J¼8.5 Hz, 2H), 7.00 (s,1H), 7.16 (s,1H), 7.29–7.35
(m, 7H); 13C NMR (125 MHz, CDCl3)
d 1.05, 1.12, 1.4, 1.5, 55.4, 62.1,
72.3, 110.0, 113.9, 126.9, 127.97, 128.04, 128.3, 128.7, 130.7, 131.2,
140.2, 140.5, 150.0, 157.6, 159.2; IR (KBr) 2957, 1612, 1556, 1514,
1450, 1251, 1097, 930, 844 cmꢀ1; MS m/z (%) (EI): 447 (Mþ, 18), 326
(16), 311 (13), 121 (100); Anal. Calcd for C25H29NO3Si2: C, 67.07;
H, 6.53; N, 3.13. Found: C, 67.28; H, 6.63; N, 3.10.
3.3.7. Cycloadduct 5g from cycloaddition of nitrone 4g with benzyne
3 generated from benzobisoxadisilole 1. As a white solid; mp 138–
139 ꢁC; 1H NMR (500 MHz, CDCl3)
d 0.30 (s, 3H), 0.31 (s, 3H), 0.346
(s, 3H), 0.353 (s, 3H), 2.30 (s, 3H), 3.65 (s, 3H), 4.30 (d, J¼9.5 Hz, 1H),
4.41 (d, J¼9.5 Hz, 1H), 5.64 (s, 1H), 6.52–6.54 (m, 2H), 6.68 (d,
J¼9.5 Hz, 2H), 7.02 (d, J¼0.5 Hz, 1H), 7.09 (d, J¼8.0 Hz, 2H), 7.21–
7.23 (m, 1H), 7.28–7.31 (m, 2H), 7.34 (d, J¼8.0 Hz, 2H), 7.45 (d,
3.3.2. 2-(4-Methylbenzyl)-3-phenyl-5,6-oxadisilole fused benzo [d]
isoxazolidine (5b). As a white solid; mp 102–103 ꢁC; 1H NMR
(500 MHz, CDCl3)
d 0.27 (s, 3H), 0.31 (s, 3H), 0.33 (s, 3H), 0.35
(s, 3H), 2.34 (s, 3H), 4.13 (d, J¼13.5 Hz, 1H), 4.33 (d, J¼13.5 Hz, 1H),
J¼0.5 Hz, 1H), 7.57–7.59 (m, 2H); 13C NMR (125 MHz, CDCl3)
d 0.98,
5.33 (s, 1H), 6.99 (d, J¼0.5 Hz, 1H), 7.14–7.17 (m, 3H), 7.29–7.34
1.05, 1.46, 1.49, 21.1, 55.6, 62.0, 77.5, 87.0, 110.6, 114.5, 116.1, 125.98,
126.05, 127.5, 127.7, 128.6, 129.3, 133.8, 135.9, 138.1, 140.1, 141.1,
142.7, 150.4, 152.7, 157.4; IR (KBr) 2955, 1617, 1512, 1249, 1102, 1040,
(m, 7H); 13C NMR (125 MHz, CDCl3)
d 1.05, 1.12, 1.4, 1.5, 21.3, 62.5,
72.4, 110.1, 126.9, 128.0, 128.1, 128.8, 129.2, 129.4, 131.2, 133.3, 137.4,
140.2, 140.5, 150.0, 157.7; IR (KBr) 2958, 1600, 1556, 1515, 1450,
1252, 1097, 930, 844 cmꢀ1; MS m/z (%) (EI): 431 (Mþ, 51), 354 (9),
326 (100), 311 (31); Anal. Calcd for C25H29NO2Si2: C, 69.56; H, 6.77;
N, 3.24. Found: C, 69.54; H, 6.74; N, 3.12.
930, 791 cmꢀ1
;
HRMS: m/z [M]þ calcd for C33H36N2O3Si2:
564.2265; found 564.2261.
3.3.8. 2-(4-Methoxybenzyl)-3-phenyl naphtho [2,3-d] isoxazolidine
(9a). As a white solid; mp 120–121 ꢁC; 1H NMR (500 MHz, CDCl3)
3.3.3. 2-Benzyl-3-phenyl-5,6-oxadisilole fused benzo [d] isoxa-
d
3.81 (s, 3H), 4.14 (d, J¼13.0 Hz, 1H), 4.35 (d, J¼13.0 Hz, 1H), 5.42 (s,
1H), 6.88–6.90 (m, 2H), 7.16 (s, 1H), 7.28–7.45 (m, 10H), 7.67–7.73
(m, 2H); 13C NMR (125 MHz, CDCl3)
55.4, 62.0, 72.0, 102.8, 114.0,
zolidine (5c). As a white solid; mp 101–102 ꢁC; 1H NMR (500 MHz,
CDCl3)
d
0.27 (s, 3H), 0.31 (s, 3H), 0.33 (s, 3H), 0.35 (s, 3H), 4.17
d
(d, J¼13.5 Hz, 1H), 4.38 (d, J¼13.5 Hz, 1H), 5.34 (s, 1H), 7.00 (d,
123.5, 123.8, 126.5, 127.2, 128.1, 128.2, 128.3, 128.8, 130.0, 130.8,
132.7, 134.8, 140.1, 155.1, 159.3; IR (KBr) 3059, 2831, 1639, 1512,
1448, 1247, 1091, 1037 cmꢀ1; HRMS: m/z [M]þ calcd for C25H21NO2:
367.1572; found 367.1570.
J¼0.5 Hz, 1H), 7.18 (d, J¼1.0 Hz, 1H), 7.25–7.33 (m, 8H), 7.33–7.40
(m, 2H); 13C NMR (125 MHz, CDCl3)
d 1.06, 1.13, 1.4, 1.5, 62.8, 72.7,
110.1, 126.9, 127.8, 128.0, 128.1, 128.6, 128.8, 129.4, 131.2, 136.4,
140.3,140.4, 150.1,157.6; IR (KBr) 2957,1600,1556,1494,1450,1252,
1097, 930, 842 cmꢀ1; MS m/z (%) (EI): 417 (Mþ, 59), 340 (31), 326
(100), 313 (35); Anal. Calcd for C24H27NO2Si2: C, 69.02; H, 6.52;
N, 3.35. Found: C, 68.77; H, 6.68; N, 3.19.
3.3.9. 2-(4-Methylbenzyl)-3-phenyl naphtho [2,3-d] isoxazolidine
(9b). As a white solid; mp 131–132 ꢁC; 1H NMR (500 MHz, CDCl3)
d
2.40 (s, 3H), 4.21 (d, J¼13.5 Hz, 1H), 4.40 (d, J¼13.5 Hz, 1H), 5.46 (s,
1H), 7.21 (d, J¼8.0 Hz, 2H), 7.32–7.49 (m, 11H), 7.71–7.77 (m, 2H);
13C NMR (125 MHz, CDCl3)
21.3, 62.3, 72.1, 102.8, 123.4, 123.7,
3.3.4. 2-(4-Chlorobenzyl)-3-phenyl-5,6-oxadisilole fused benzo [d]
d
isoxazolidine (5d). As a white solid; mp 96–97 ꢁC; 1H NMR
126.4 127.2, 128.0, 128.1, 128.2, 128.8, 129.3, 129.4, 130.0, 132.7,
133.3, 134.7, 137.5, 140.0, 155.1; IR (KBr) 3037, 2856, 2830, 1634,
1506, 1452, 1253, 1232, 1213, 1162, 1080 cmꢀ1; MS m/z (%) (EI): 351
(Mþ, 49), 246 (24), 231 (100), 202 (18); Anal. Calcd for C25H21NO: C,
85.44; H, 6.02; N, 3.99; Found: C, 85.38; H, 6.04; N, 3.97.
(500 MHz, CDCl3)
d 0.27 (s, 3H), 0.30 (s, 3H), 0.33 (s, 3H), 0.34
(s, 3H), 4.27 (d, J¼14.5 Hz, 1H), 4.42 (d, J¼14.5 Hz, 1H), 5.35 (s, 1H),
6.97 (d, J¼0.5 Hz, 1H), 7.15 (s, 1H), 7.35–7.43 (m, 5H), 7.60 (d,
J¼8.5 Hz, 2H), 8.20 (d, J¼8.5 Hz, 2H); 13C NMR (125 MHz, CDCl3)
d
1.05, 1.11, 1.4, 1.5, 62.0, 73.0, 110.1, 126.8, 128.0, 128.3, 128.7, 128.9,
130.6, 131.1, 133.6, 135.1, 140.1, 140.5, 150.2, 157.4; IR (KBr) 2957,
1599, 1557, 1492, 1448, 1252, 1097, 934, 841 cmꢀ1; MS m/z (%) (EI):
451 (Mþ, 43), 374 (20), 326 (100), 311 (29); Anal. Calcd for
C24H26ClNO2Si2: C, 63.76; H, 5.80; N, 3.10. Found: C, 63.44; H, 5.88;
N, 2.93.
3.3.10. 2-Benzyl-3-phenyl naphtho [2,3-d] isoxazolidine (9c). As
a white solid; mp 126–127 ꢁC; 1H NMR (500 MHz, CDCl3)
d 4.22
(d, J¼13.5 Hz, 1H), 4.42 (d, J¼13.5 Hz, 1H), 5.44 (s, 1H), 7.17 (s, 1H),
7.29–7.46 (m, 13H), 7.68–7.74 (m, 2H); 13C NMR (125 MHz, CDCl3)
d
62.6, 72.4,102.8,123.4,123.8,126.5,127.2,127.9,128.1,128.2,128.3,
128.6, 128.8, 129.4, 130.0, 132.7, 134.7, 136.4, 139.9, 155.0; IR (KBr)
3036, 2919,1635,1495,1455,1252,1164,1093 cmꢀ1; MS m/z (%) (EI):
337 (Mþ, 62), 246 (44), 231 (100), 202 (25); Anal. Calcd for C24H19NO:
C, 85.43; H, 5.68; N, 4.15; Found: C, 85.54; H, 5.69; N, 3.86.
3.3.5. 2-(4-Nitrobenzyl)-3-phenyl-5,6-oxadisilole fused benzo [d]
isoxazolidine (5e). As a white solid; mp 144–145 ꢁC; 1H NMR
(500 MHz, CDCl3)
d 0.28 (s, 3H), 0.32 (s, 3H), 0.34 (s, 3H), 0.36 (s,
3H), 4.28 (d, J¼14.5 Hz,1H), 4.43 (d, J¼14.5 Hz,1H), 5.37 (s,1H), 6.98
(s, 1H), 7.17 (s, 1H), 7.34–7.45 (m, 5H), 7.61 (d, J¼9.0 Hz, 2H),
3.3.11. 2-(4-Chlorobenzyl)-3-phenyl naphtho [2,3-d] isoxazolidine
8.19–8.21 (m, 2H); 13C NMR (125 MHz, CDCl3)
d
1.2, 1.3, 1.6, 1.7, 62.0,
(9d). As a white solid; mp 138–139 ꢁC; 1H NMR (500 MHz, CDCl3)
74.0, 110.1, 123.9, 126.9, 128.3, 128.8, 129.2, 129.9, 131.3, 139.8, 141.0,
d
4.18 (d, J¼13.5 Hz, 1H), 4.34 (d, J¼13.5 Hz, 1H), 5.41 (s, 1H), 7.16

582
K. Wu et al. / Tetrahedron 66 (2010) 578–582
(s, 1H), 7.29–7.44 (m, 12H), 7.69–7.74 (m, 2H); 13C NMR (125 MHz,
CDCl3) 61.8, 72.8, 102.8, 123.4, 123.9, 126.6, 127.2, 128.1, 128.2,
128.4, 128.8, 128.9, 130.1, 130.7, 132.6, 133.7, 134.7, 135.0, 139.6,
154.8; IR (KBr) 3062, 2881, 1640, 1507, 1492, 1447, 1246, 1089,
1015 cmꢀ1; MS m/z (%) (EI): 371 (Mþ, 43), 231 (100), 246 (41), 202
(21); Anal. Calcd for C24H18ClNO: C, 77.52; H, 4.88; N, 3.77; Found:
C, 77.70; H, 4.78; N, 3.52.
2. (a) Houk, K. N.; Yamaguchi, K. In 1,3-Cycloaddition Chemistry, [M]; Padwa, A.,
Ed.; Wiley: New York, NY, 1984; Vol. 2, p 83; (b) Houk, K. N.; Sims, J.; Watts, C.
R.; Luskus, L. J. J. Am. Chem. Soc. 1973, 95, 7301–7315; (c) Stang, P. J.; Murch, P.
Tetrahedron Lett. 1997, 51, 8793–8974; (d) Zhu, S. Z.; Jin, G. F.; Peng, W. M.;
Huang, Q. C. Tetrahedron 2003, 59, 2899–2905.
d
3. (a) Hart, H.; Ok, D. J. Org. Chem. 1986, 51, 979–986; (b) Bigdeli, M. A.; Tipping, A.
E. J. Fluorine Chem. 1992, 58, 101–110; (c) Matsumoto, T.; Sohma, T.; Hatazaki, S.;
Suzuki, K. Synlett 1993, 843–846; (d) Hamura, T.; Arisawa, T.; Matsumoto, T.;
Suzuki, K. Angew. Chem., Int. Ed. 2006, 45, 6842–6844; (e) Ashraf, A. A.; Hen-
ning, H.; Ludger, E.; Ina, D.; Peter, G. J. Eur. J. Org. Chem. 2006, 3001–3006.
4. (a) Hoffmann, R. W. Dehydrobenzene and Cycloalkynes; Academic: New York,
NY, 1967; (b) Hart, H. Supplement C2 In The Chemistry of Triple-Bonded
Functional Groups; Patai, S., Ed.; Wiley: New York, NY, UK, 1994; pp 1017–1134;
(c) Gilchrist, T. L. Supplement C2 In The Chemistry of Functional Groups; Patai, S.,
Rappoport, Z., Eds.; Wiley: Chichester, UK,1983; pp 383–419; (d) Cobas, A.; Diaz,
M. T.; Escudero, S.; Prez, D.; Guitian, E.; Castedo, L. In Current Trends in Organic
Synthesis; Scolastico, C., Nicotra, F., Eds.; Plenum: 1999; pp 307–314; (e) Wank,
H. H.; Sand, W.; Winkler, M. Angew. Chem., Int. Ed. 2003, 42, 502–528; (f) Pellisier,
H.; Santelli, M. Tetrahedron 2003, 59, 701–730.
5. (a) Chen, Y. L.; Zhang, H. K.; Wong, W. Y.; Lee, A. W. M. Tetrahedron Lett. 2002,
43, 2259–2262; (b) Chen, Y. L.; Sun, J. Q.; Wei, X.; Wong, W. Y.; Lee, A. W. M.
J. Org. Chem. 2004, 69, 7190–7197.
6. (a) Chen, Y. L.; Hau, C. K.; Wang, H.; He, H.; Wong, M. S.; Lee, A. W. M. J. Org. Chem.
2006, 71, 3512–3517; (b) Chen, Y. L.; Lee, M. H.; Wong, W. Y.; Lee, A. W. M. Synlett
2006, 2510–2512; (c) Chen, Y. L.; Wong, M. S.; Wong, W. Y.; Lee, A. W. M.
Tetrahedron Lett. 2007, 48, 2421–2425; (d) Chen, Y. L.; Wong, W. Y.; Lee, A. W. M.
Tetrahedron Lett. 2008, 49, 1257–1260.
3.3.12. 2-(4-Nitrobenzyl)-3-phenyl naphtho [2,3-d] isoxazolidine
(9e). As a white solid; mp 140–141 ꢁC; 1H NMR (500 MHz, CDCl3)
d
4.31 (d, J¼14.0 Hz, 1H), 4.44 (d, J¼14.0 Hz, 1H), 5.45 (s, 1H), 7.13 (s,
1H), 7.30–7.46 (m, 8H), 7.63 (d, J¼8.5 Hz, 2H), 7.69 (d, J¼8.5 Hz, 1H),
7.72 (d, J¼8.5,1H), 8.22 (d, J¼8.5 Hz, 2H); 13C NMR (125 MHz, CDCl3)
d
61.7, 73.6, 102.8, 123.4, 123.8, 124.1, 126.7, 127.3, 128.1, 128.3, 128.7,
129.1, 129.8, 130.1, 132.4, 134.7, 139.1, 144.3, 147.6, 154.5; IR (KBr)
3060, 2878,1640,1604,1513,1448,1344,1247,1090 cmꢀ1; HRMS: m/
z [M]þ calcd for C24H18N2O3: calcd 382.1317; found 382.1316.
Acknowledgements
Financial support from the National Natural Science Foundation
of China (No. 20872086), the Project of Shanghai Municipal Edu-
cation Commission (Nos. 09YZ19 and J50102), the Hong Kong Re-
search Grants Council (HKBU 201307) are gratefully acknowledged.
7. (a) Maskill, H.; Jencks, W. P. J. Am. Chem. Soc. 1987, 109, 2062–2070; (b) Mur-
ahashi, S. I.; Mitsui, H.; Shiota, T. J. Org. Chem. 1990, 55, 1736–1744; (c) Gothelf,
K. V.; Jørgensen, K. A. Chem. Rev. 1998, 98, 863–909; (d) Schwartz, M. A.; Hu, X.
F. Tetrahedron Lett. 1992, 33, 1689–1692; (e) Merino, P.; Franco, S.; Lafuente, D.;
Merchan, F.; Revuelta, J.; Tejero, T. Eur. J. Org. Chem. 2003, 2877–2881.
8. (a) Coskun, N.; Asutay, O. Chim. Acta Turc. 1999, 27, 17–23; (b) Lu, L.; Cao, W. G.;
Chen, J.; Zhang, H.; Chen, H. Y.; Wei, J. M.; Deng, H. M.; Shao, M. J. Fluorine Chem.
2009, 130, 295–300.
References and notes
9. (a) Liu, Z.; Larock, R. C. Org. Lett. 2004, 6, 99–102; (b) Zhao, J.; Larock, R. C. Org.
Lett. 2005, 7, 4273–4275; (c) Shi, F.; Waldo, J. P.; Chen, Y.; Larock, R. C. Org. Lett.
2008, 10, 2409–2412.
1. (a) Dai, M.; Danishefsky, S. J. Tetrahedron Lett. 2008, 49, 6613–6616; (b) Wu, Q.
C.; Li, B. S.; Lin, W. Q.; Shi, C. Q.; Chen, Y. W.; Chen, Y. X. Chin. J. Synth. Chem.
2007, 15, 292–295.
¨
¨
10. Cos¸kun, N.; Tat, F. T.; Gu¨ven, O. O Tetrahedron 2001, 57, 3413–3417.