Studies on the synthesis of novel chiral naphthylene bisoxazoline ligands

Article abstract of DOI:10.1081/SCC-120018687

The synthesis of chiral C₂-symmetric substituted bisoxazoline ligands containing naphthalene group were investigated. Ethyl 2,3-naphthylene-dicarboxylate reacted with amino alcohols and the resulting amides were treated with SOCl₂ and then reacted with Et₃N in toluene to afford the desired bisoxazolines. 2,3-Naphthylenedicarbonitrile reacted with amino alcohol give N-(1′-phenyl-2′-hydroxyethyl)-2,3naphthylenedicarboximide 1. The 2,3-naphthylenedicarboxylic acid reacted with thionyl chloride give the 2,3-Naphthalenedicarboxylic acid cyclic anhydride rather than corresponding 2,3-naphthalenedicarboxylic acid dichloride, the former reacted with amino alcohol also give compound 1. The later two strategies cannot give the target bisoxazoline.

Full text of DOI:10.1081/SCC-120018687

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Studies on the Synthesis of Novel Chiral Naphthylene
Bisoxazoline Ligands
a
a
a
a
Zhan-Yue Wang , Da-Ming Du , Di Wu & Wen-Ting Hua
a
Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education,
College of Chemistry and Molecular Engineering, Peking University, Beijing, P.R. China
Published online: 15 Aug 2006.
To cite this article: Zhan-Yue Wang , Da-Ming Du , Di Wu & Wen-Ting Hua (2003) Studies on the Synthesis of Novel Chiral
Naphthylene Bisoxazoline Ligands, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 33:8, 1275-1283, DOI: 10.1081/SCC-120018687
To link to this article: http://dx.doi.org/10.1081/SCC-120018687
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Õ
SYNTHETIC COMMUNICATIONS
Vol. 33, No. 8, pp. 1275–1283, 2003
Studies on the Synthesis of Novel Chiral
Naphthylene Bisoxazoline Ligands
Zhan-Yue Wang, Da-Ming Du,* Di Wu, and Wen-Ting Hua
Key Laboratory of Bioorganic Chemistry and
Molecular Engineering of Ministry of Education,
College of Chemistry and Molecular Engineering,
Peking University, Beijing, P.R. China
ABSTRACT
2
The synthesis of chiral C -symmetric substituted bisoxazoline ligands
containing naphthalene group were investigated. Ethyl 2,3-naphthy-
lene-dicarboxylate reacted with amino alcohols and the resulting
amides were treated with SOCl and then reacted with Et N in toluene
2
3
to afford the desired bisoxazolines. 2,3-Naphthylenedicarbonitrile
0
0
reacted with amino alcohol give N- (1 -phenyl-2 -hydroxyethyl)-2,3-
naphthylenedicarboximide 1. The 2,3-naphthylenedicarboxylic acid
*
Correspondence: Da-Ming Du, Key Laboratory of Bioorganic Chemistry and
Molecular Engineering of Ministry of Education, College of Chemistry and
Molecular Engineering, Peking University, Beijing 100871, P.R. China; Fax:
8
6-10-62751708; E-mail: dudm@pku.edu.cn.
1
275
DOI: 10.1081/SCC-120018687
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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1
276
Wang et al.
reacted with thionyl chloride give the 2,3-Naphthalenedicarboxylic
acid cyclic anhydride rather than corresponding 2,3-naphthalene-
dicarboxylic acid dichloride, the former reacted with amino alcohol
also give compound 1. The later two strategies cannot give the target
bisoxazoline.
Key Words: Bisoxazoline; Naphthylene; Synthesis; Amino alcohol.
In recent years, the C -symmetric chiral bis(oxazolines) are very useful
2
ligands in the catalysis of many reactions. The design and synthesis of new
chiral oxazoline ligands and their metal complexes in asymmetric catalytic
[
1–8]
reaction has inspired many scientists to work with great efforts.
Our
interest has focused on the studies of enantioselective transition-metal
catalysis of heterocyclic ligands. In the design of our new ligands it was
crucial to have a rigid cyclic backbone. We have chosen system of
bisoxazoline containing naphthylene, it has rigid aromatic unit and
N coordination sites, the facial selectivity of naphthylene and chiral
selectivity of oxazoline may result special enantioselectivity. The size of
the chelate in the reaction metal complex of bisoxazolines is an important
factor of the catalyst since it will controll the orientation of the substituents
on the two oxazolines around the metal ion. The design and synthesis of
[
9]
closely related 1,2-bis(2-oxazolinyl)benzene ligands are reported. In this
article, we reported the synthesis of new chiral naphthylene bisoxazolines.
Chiral C -symmetric substituted bisoxazoline ligands containing
2
naphthylene group were designed in present work considering it has
a rigid aromatic unit. The synthesis of naphthylene bisoxazoline was
attempted following several of the procedures described above.
0
0
2
,3-Naphthylenedicarbonitrile 3 can be easily prepared from a,a,a ,a -
[10]
tetrabromo-o-xylene 2 and fumaronitrile. So, 2,3-naphthylenedicarbo-
nitrile reacted with amino alcohol in chlorobenzene with ZnCl may be the
2
convenient way to synthesize the target bisoxazoline. In fact, 2,3-naphthyl-
enedicarbonitrile reacted with R-phenylglycinol in chlorobenzene with
ꢀ
ZnCl as catalyst at 130 C do not give the corresponding bisoxazoline,
2
0
0
but give the cyclized five-member ring product, N- (1 -phenyl-2 -hydroxy-
ethyl)-2,3-naphthylenedicarboximide 1a in 53% yield. This cyclized
product does not like the reaction product of phthalodinitrile and
2-aminoethanol, which give the 1,3-bis-(2-hydroxyethylimino)isoindole
as the main product. The 2,3-naphthylenedicarboxylic acid 4, prepared
[11]
0
0
[12]
from a,a,a ,a -tetrabromo-o-xylene and maleic anhydride, reacted with
thionyl chloride unexpectedly give the 2,3-Naphthalenedicarboxylic acid

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Naphthylene Bisoxazoline Ligands
1277
cyclic anhydride 5 rather than corresponding 2,3-Naphthalenedicar-
boxylic acid dichloride. 2,3-Naphthalenedicarboxylic acid cyclic anhy-
dride 5 reacted with S-Leucinol give compound 1c in 89% yield, this
route also can not give the target bisoxazoline. Fortunately, ethyl
2,3-naphthylenedicarboxylate 6 reacted with amino alcohol in the absence
of solvent give the corresponding hydroxy amide intermediates 7b and 7c
in 91 and 85% yield. Treatment of hydroxy amides 7b and 7c with MsCl
and Et N also can not give the target bisoxazoline. Hydroxy amide
3
intermediates 7b and 7c were treated with SOCl to afford the correspond-
2
ing chloride intermediate 8b and 8c in 61.4 and 15.3% yield. Besides 8c
was formed from the reaction of 7c, mono cyclized oxazoline 10 was also
formed in 46.2% yeild. Compounds 8b and 8c was cyclized by treated
with Et N and toluene to give the desired bisoxazoline 9b and 9c in 83.3
3
and 70.3% yield, respectively (Sch. 1). The difficulty in synthesis of
this series of bisoxazoline may be ascribed to the intramolecular and
intermolear hydrogen bonding of hydroxy amide intermediate. The
hydrogen bonding forbidden the enolization and imino formation is
difficult, and thus result in the slowly cyclization process.
Bisoxazolines have been used as catalysts for the enantioselective
synthesis. The application of 2,3-naphthylene bisoxazoline metal
complexes as asymmetric catalysts for stereoselective transformations
are currently under investigation in our group.
EXPERIMENTAL
Melting points were measured on an XT-4 melting point apparatus
1
and are uncorrected. H NMR spectrawere recorded on aBrucker
400 MHz spectrometer, tetramethylsilane (TMS) serving as internal
standard. Infrared spectra were obtained on a Bruker Vector 22
spectrometer. Mass spectra were obtained on a VG-ZAB-HS mass
spectrometer. Optical rotations were measured on a Perkin-Elmer 241
MC spectrometer. Elemental analyses were carried out on an Elementar
Vario EL instrument. Solvents used were purified and dried by standard
procedures.
0
0
2
,3-Naphthylenedicarbonitrile was prepared from a,a,a ,a -tetra-
[10]
bromo-o-xylene and fumaronitrile according to Lit. 2,3-Naphthylene-
dicarboxylic acid was prepared from a,a,a ,a -tetrabromo-o-xylene and
malic anhydride according to literature procedure.
N-[(R)-1 -Phenyl-2 -hydroxyethyl]-2,3-naphthylenedicarboximide 1a:
,3-naphthylenedicarbonitrile (0.5 g, 2.8 mmol), D-phenylglycinol (0.9 g,
.6 mmol) and ZnCl2 (0.1 g) in chlorobenzene (30 mL) with heated
0
0
[
12]
0
0
2
6

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1
278
Wang et al.
0
0
Scheme 1. Synthesis of 2,3-bis[(4 s)R-oxazolin-2 -yl]napthylene.
ꢀ
at 130 C for 72 h. The solvent was removed under reduced pressure, the
residue was treated with water (10 mL) and than extracted with dichlor-
omethane (3 Â 20 mL). The layer was separated, and the organic layer
was washed with brine and dried with anhydrous Na SO . The solvent
2
4
was removed under reduced pressure and the residue was purified by
column chromatography on silica gel (ethyl acetate–petroleum ether

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Naphthylene Bisoxazoline Ligands
1279
1
:2 v/v) to afford 0.47 g (53%) pure N-((R)-2-phenylethanol-2-yl)-2,3-
ꢀ
20
D
o
naphthylenedicarboximide 1a. M.p. 154–155 C. [a] ¼ þ50:0 (c ¼ 0.4,
1
CHCl ); H NMR (CDCl ): ꢀ 3.18 (1H, s, OH), 4.26 (1H, dd, J ¼ 4.4,
3
3
1
6.4 Hz, OCH), 4.77 (1H, dd, J ¼ 9.8, 19.4 Hz, CHN), 5.57 (1H, dd,
J ¼ 5.0, 11.2 Hz, OCH), 7.26–7.37 (3H, m, ArH), 7.50 (2H, d, J ¼
.2 Hz, ArH), 7.60–7.64 (2H, m, ArH), 7.89–7.94 (2H, m, ArH), 8.15
2H, s, ArH). IR (KBr): ꢁ 3453, 3063, 3032, 1762, 1708, 1638, 1515,
7
(
ꢁ1
1
494, 1474, 1455, 1425 cm . FABMS: m/z 318 (M þ 1, 20), 257 (18),
232 (18), 217 (100). Anal. C H NO , Calcd.: C, 75.70; H, 4.76; N, 4.41;
Found: C, 75.53; H, 4.80; N, 4.28.
2
0
15
3
0
0
N-[(S)-1 -Isobutyl-2 -hydroxyethyl)-2,3-naphthylenedicarboximide 1c:
A solution of 2,3-naphthylenedicarboxylic acid (2.16 g, 10 mmol) and
SOCl (40 mL) was refluxed for 13 h. The excess SOCl was removed
2
2
under reduced pressure, benzene (10 mL) was added and the solvent was
removed again to dryness to afford the 2,3-Naphthalenedicarboxylic acid
ꢀ
1
cyclic anhydride 5 1.85 g (93.4%). M.p. 248–249 C. H NMR (CDCl ):
3
ꢀ
8
7.82 (2H, dd, J ¼ 3.2, 6.2 Hz, ArH), 8.15 (2H, dd, J ¼ 3.2, 6.2 Hz, ArH),
.56 (2H, s, ArH).
To the solution of S-leucinol (1.15 g, 9.8 mmol) and Et N (3.5 mL) in
3
CH Cl (30 mL) was added dropwise a solution of 2,3-naphthalene-
2
2
dicarboxylic acid cyclic anhydride 5 (1.25 g, 6.3 mmol) and stirring at
room temperature for 24 h. Then water (50 mL) was added to the reaction
vessel and organic phase was separated from reaction mixture. The
aqueous layer was extracted with CH Cl (3 Â 30 mL). The organic phase
2
2
were combined and washed with brine, dried over anhydrous Na SO and
2
4
filtered. The filtrate was concentrated in vacuo, the crude product was
purified by column chromatogrsphy on silica gel (ethyl acetate–methanol
5
:2 containing 1% Et N) to afford colorless crystals 1c 1.67g (89%).
3
ꢀ
D
o
1
M.p. 103 C. [a] ¼ þ41.8 (c ¼ 0.5, CHCl ); H NMR (CDCl ): ꢀ 0.93
20
3
3
(
NCH), 3.38–3.78 (2H, m, CH ), 4.23 (1H, s, OH), 6.99–7.99 (6H, m,
6H, d, J ¼ 5.6 Hz, CH ), 1.10–1.80 (3H, m, CHþCH ), 3.05–3.20 (1H, m,
3
2
2
ArH). IR (KBr): ꢁ 3250, 3103, 2957, 2867, 1651, 1627, 1563, 1446, 1313,
ꢁ
1
þ
1
1
2
043 cm . EIMS: m/z 297 (M , 8), 266 (70), 224 (35), 210 (100), 180 (25),
26 (35), 86 (82). HRMS: C H NO , Calcd. 297.13649; Found:
1
8
19
3
97.13555.
0
0
0
2,3-Bis[N-(1 S)-(1 -isopropyl-2 -hydroxyethyl)-amido]naphthylene 7b:
S)-Valinol (1.3 g, 13 mmol) and ethyl 2,3-naphthylenedicarboxylate 6
1.1 g, 4.4 mmol) were heated at 120 C for 4 h under nitrogen, while
(
(
ꢀ
generated methanol was removed through a distillation equipment. The
crude product was recrystallized from methanol–ethyl acetate to afford
ꢀ
D
o
colorless solid 7b 1.6 g (91%). M.p. 215–217 C. [a] ¼ þ37.5 (c ¼ 0.2,
2
0
1
MeOH). H NMR (DMSO): ꢀ 0.94 (12H, d, J ¼ 6.4 Hz, CH ), 1.80–1.98
3

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1
280
Wang et al.
(
(
2H, m, CH), 3.50 (4H, t, J ¼ 5.4 Hz, OCH ), 3.70–3.80 (2H, m, CH), 4.52
2
2H, t, J ¼ 5.4 Hz, OH), 7.61 (2H, dd, J ¼ 3.0, 6.2 Hz, ArH), 8.01 (2H, dd,
J ¼ 3.2, 6.2 Hz, ArH), 8.05 (2H, s, ArH), 8.16 (2H, d, J ¼ 9.0 Hz, NH).
IR (KBr): ꢁ 3308, 2969, 2876, 1650, 1622, 1593, 1537, 1435, 1316,
1
ꢁ1
032 cm . FABMS: m/z 387 (M þ 1, 5), 217 (30), 181 (15), 91 (100).
Anal. C H N O , Calcd.: C, 68.37; H, 7.82; N, 7.25; Found: C, 68.17;
2
2
30
2
4
H, 7.79; N, 7.21.
0
0
0
2
,3-Bis[N-(1 S)-(1 -isobutyl-2 -hydroxyethyl)-amido]naphthylene 7c:
Following the same procedure as decribed for 7b, (S)-Leucinol (1.42 g,
2.1 mmol) and ethyl 2,3-naphthylenedicarboxylate 6 (1.4 g, 5.7 mmol) to
1
ꢀ
D
o
afford colorless solid 7c 2.0 g (85%). M.p. 209–210 C. [a] ¼ þ11.2
2
0
1
(
CH ), 1.31–1.47 (4H, m, CH ), 1.74–1.84 (2H, m, CH), 3.35–3.53
c ¼ 0.6, MeOH); H NMR (DMSO): ꢀ 0.91 (12H, dd, J ¼ 6.6 Hz,
3
2
(
4H, m, CH ), 3.95–4.03 (2H, m, CH), 4.59 (2H, t, J ¼ 5.8 Hz, OH),
2
7
.61 (2H, dd, J ¼ 3.4, 6.2 Hz, ArH), 7.99 (2H, s, ArH), 8.01 (2H, dd,
J ¼ 3.4, 6.2 Hz, ArH), 8.12 (2H, d, J ¼ 8.6 Hz, NH). IR (KBr): ꢁ 3253,
ꢁ1
3
103, 2956, 2868, 1650, 1627, 1598, 1567, 1448, 1313, 1044 cm
.
FABMS: m/z 415 (M þ 1, 15), 298 (92). Anal. C H N O , Calcd.: C,
2
4
34
2
4
6
9.54; H, 8.27; N, 6.76; Found: C, 69.57; H, 8.20; N, 6.78.
0 0 0
2
To the suspension of dihydroxy diamide 7b (0.67 g 1.73 mmol) in the
,3-Bis[N-(1 S)-(1 -isopropyl-2 -chloroethyl)-amido]naphthylene 8b:
CH Cl (20 mL) was added thionyl chloride (1.5 mL, 20 mmol) via
2
2
syringe. The mixture was kept refluxing for 4 h. The reaction mixture
was cooled and poured into the ice-water, the organic phase (CH Cl )
was separated from the mixture. The aqueous layer was extracted with
2
2
CH Cl (3 Â 20 mL). The combined organic phase was washed with 5%
2
2
NaHCO (20 mL), water (20 mL) and brine (20 mL), respectively, dried
3
over Na SO and filtered. The filtrate was concentrated in vacuo to afford
2
4
the crude product. The crude product was purified by column chromato-
graphy on silica gel (ethyl acetate/petroleum ether/methanol 5:1:0.2) and
recrystallized from ethyl acetate–petroleum ether to afford colorless
ꢀ
D
o
needles 8b 0.45 g (61.4%). M.p. 174–176 C. [a] ¼ ꢁ89.2 (c ¼0.5,
2
0
1
CHCl ); H NMR (CDCl ): ꢀ 1.05 (6H, d, J ¼ 4.8 Hz, 2CH ), 1.08 (6H,
3
3
3
d, J ¼ 4.8 Hz, 2CH ), 2.00–2.17 (2H, m, CH), 3.76–3.91 (4H, m, CH Cl),
3
2
4
.12–4.25 (2H, m, CHN), 7.03 (2H, d, J ¼ 8.8 Hz, NH), 7.60 (2H, dd,
J ¼ 3.2, 6.4 Hz, ArH), 7.90 (2H, dd, J ¼ 3.4, 6.2 Hz, ArH), 8.15 (2H, s,
ArH). IR (KBr): ꢁ 3263, 3056, 2963, 2874, 1639, 1552, 1464, 1316,
ꢁ1
1
205 cm . FABMS: m/z 423 (M þ 1, 10), 387 (5), 302 (90), 198 (100).
Anal. C H N O Cl , Calcd.: C, 62.41; H, 6.67; N, 6.62; Found: C,
2
2
2
28
2
2
6
2.68; H, 6.69; N, 6.61.
0
0
0
2
,3-Bis[N-(1 S )-(1 -isobutyl-2 -chloroethyl)-amido]naphthylene 8c:
Dihydroxy diamide 7c (1.1 g 2.6 mmol) and thionyl chloride (2.3 mL,

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Naphthylene Bisoxazoline Ligands
1281
30.7 mmol) was was treated with procedure as decribed for 8b. The crude
product was purified by column chromatography on silica gel, first elut-
ing with ethyl acetate/petroleum ether (v/v 1:15) to give the product 10
0.52 g (46.2%). Followed by eluting with ethyl acetate/petroleum ether
ꢀ
(
[
6
1
v/v 1:6) to afford the colorless plates 8c 0.18 g (15.3%). M.p. 169–171 C.
D
o
1
a] ¼ ꢁ98.3 (c ¼ 0.12, CHCl ); H NMR (CDCl ): ꢀ 1.00 (6H, d, J ¼
20
3
3
.4 Hz, 2CH ), 1.01 (6H, d, J ¼ 6.2 Hz, 2CH ), 1.55–1.64 (4H, m, CH ),
2 2
3
3
2
.70–1.76 (2H, m, Me CH), 3.71 (2H, dd, J ¼ 3.2, 11.0 Hz, CH Cl), 3.92
(
2H, dd, J ¼ 4.0, 11.0 Hz, CH Cl), 4.48–4.60 (2H, m, CHN), 6.89 (2H, d,
2
J ¼ 8.2 Hz, NH), 7.61 (2H, dd, J ¼ 3.2, 6.2 Hz, ArH), 7.91 (2H, dd,
J ¼ 3.2, 6.2 Hz, ArH), 8.13 (2H, s, ArH). IR (KBr): ꢁ 3273, 3065, 2955,
ꢁ1
2
4
7
857, 1642, 1551, 1464, 1312, 1207 cm . FABMS: m/z 451 (M þ 1, 16),
15 (9), 316 (100), 198 (100). Anal. C H N O Cl , Calcd.: C, 63.85; H,
2
2
4
32
2
2
.14; N, 6.21; Found: C, 63.58; H, 7.08; N, 6.20.
ꢀ
D
o
Compound 10: M.p. 120–122 C. [a] ¼ ꢁ41.6 (c ¼0.5, CHCl );
2
0
3
1
H NMR (CDCl ): ꢀ 0.97 (12H, t, J ¼ 6.4 Hz, 4CH ), 1.47–1.71 (6H, m,
3
3
Me CHþCH ), 3.57–3.73 (4H, m, OCH þ CH Cl), 4.37–4.49 (2H, m,
2
2
2
2
CHN), 7.62 (2H, dd, J ¼ 3.2, 6.2 Hz, ArH), 8.00 (2H, dd, J ¼ 3.2,
1
.4 Hz, ArH), 8.46 (2H, s, ArH). C NMR (CDCl ): ꢀ 21.81, 23.47,
3
6
3
25.11, 43.12, 48.93, 57.52, 115.99, 123.39, 128.22, 129.35, 135.15. IR
(
9
KBr): ꢁ 3065, 2956, 2871, 1735, 1681, 1613, 1509, 1467, 1366, 1271,
ꢁ
1
37 cm . FABMS: m/z 433 (Mþ1, 34), 332 (21), 315 (100), 197 (100).
Anal. C H N OCl , Calcd.: C, 66.51; H, 6.98; N, 6.46; Found: C, 66.52;
24 30 2 2
H, 6.88; N, 6.48.
0
0
2
,3-Bis[(4 S )-isopropyloxazolin-2 -yl]naphthylene 9b: A 100 mL round-
bottom flask with a magnetic stir bar was charged with compound 8b
277 mg, 0.65 mmol) and Et N (0.92 mL, 6.6 mmol) and toluene (25 mL).
(
3
The solution was stirred under reflux for 12 h. After cooling to room
temperature, ethyl acetate (50 mL) was added and the resulting mixture
was washed with water (50 mL) and brine (50 mL), dried over anhydrous
Na SO and filtered. The solvent was removed under reduced pressure.
2
4
Purification of the residue by column chromatography on silica gel (ethyl
acetate–petroleum ether 1:3) to afford the pure oily product 9b 0.19 g
D
o
1
(
(
(
83.3%). [a] ¼ ꢁ38.7 (c ¼ 0.68, CHCl ); H NMR (CDCl ): ꢀ 0.99
20
3
3
6H, d, J ¼ 6.8 Hz, 2CH ), 1.08 (6H, d, J ¼ 6.2 Hz, 2CH ), 1.80–2.02
3 3
2H, m, CH), 4.06–4.20 (4H, m, CH O), 4.42 (2H, t, J ¼ 12.8 Hz,
2
CHN), 7.52 (2H, m, ArH), 7.86–7.90 (2H, m, ArH), 8.29 (2H, s, ArH).
IR (KBr): ꢁ 3057, 2959, 2874, 1734, 1656, 1597, 1469, 1347, 1087,
ꢁ
73 cm . HRFABMS: C H N O , Calcd.: 351.2067; Found: 351.2064.
22 27 2 2
1
9
0
0
2,3-Bis[(4 S )-isobutyloxazolin-2 -yl]naphthylene 9c: Compound 8c
85 mg, 0.19 mmol) and Et N (0.26 mL, 1.9 mmol) was treated with
(
procedure as decribed for 9b. The crude product was purified by column
3

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2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
1
282
Wang et al.
chromatography on silica gel (ethyl acetate/petroleum ether 1:6) to give
D
o
1
the oily 9c 50 mg (70.3%). [a] ¼ ꢁ16.5 (c ¼ 0.2, CHCl ); H NMR
2
0
3
(
CDCl ): ꢀ 1.00 (12H, t, J ¼ 6.2 Hz, 4CH ), 1.20–1.70 (4H, m, CH ),
3
3
2
1
.70–1.94 (2H, m, Me CH), 3.90–4.42 (4H, m, CH O), 4.45–4.57 (2H,
2 2
m, CHN), 7.56 (2H, dd, J ¼ 3.4, 6.4 Hz, ArH), 7.88 (2H, dd, J ¼ 3.4,
6
1
3
.4 Hz, ArH), 8.27 (2H, s, ArH). IR (KBr): ꢁ 3055, 2961, 2873,
ꢁ
1
733, 1638, 1558, 1460, 1375, 1282 cm . HREIMS: C H N O , Calcd.:
2
4
30
2
2
78.2307; Found: 378.2292.
ACKNOWLEDGMENT
This work was supported by the National Natural Science
Foundation of China (Grant No. 20172001). Visiting Scholar from
Wenzhou Medical College, Wenzhou, Zhejiang, P.R. China.
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2
3
4
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1

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2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.
Naphthylene Bisoxazoline Ligands
1283
11. Witte, H.; Seeliger, W. Liebigs Ann. Chem. 1974, 996.
12. Carlson, R.G.; Srinivasachar, K.; Givens, R.S.; Matuszewski, B.K.
J. Org. Chem. 1986, 51, 3978.
Received in Japan April 2, 2002

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©
2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.