The first regio- and diastereoselective synthesis of homochiral perhydroimidazoisoxazoles via the 1,3-dipolar cycloaddition of imidazoline 3-oxides with (1S)-(-)-β-pinene

Article abstract of DOI:10.1016/S0957-4166(01)00270-1

The 1,3-dipolar cycloaddition of imidazoline 3-oxides 1 with (1S)-(-)-β-pinene proceeds regio- and diastereoselectively to give homochiral perhydroimidazoisoxazole derivatives 3 in high yields in the cases of imidazoline 3-oxides 1a-e but in low yields in

Full text of DOI:10.1016/S0957-4166(01)00270-1

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 12 (2001) 1463–1467
The first regio- and diastereoselective synthesis of homochiral
perhydroimidazoisoxazoles via the 1,3-dipolar cycloaddition of
imidazoline 3-oxides with (1S)-(−)-b-pinene
a,
a
b
8
8
Necdet Cos¸kun, * Fatma Tirli Tat and Ozden Ozel Gu¨ven
aUludag˘ University, Department of Chemistry, 16059 Bursa, Turkey
bZonguldak Karaelmas University, Department of Chemistry, 67100 Zonguldak, Turkey
Received 1 May 2001; accepted 11 June 2001
Abstract—The 1,3-dipolar cycloaddition of imidazoline 3-oxides 1 with (1S)-(−)-b-pinene proceeds regio- and diastereoselectively
to give homochiral perhydroimidazoisoxazole derivatives 3 in high yields in the cases of imidazoline 3-oxides 1a–e but in low
yields in the reactions of 1f–g. The preferred attack of (1S)-(−)-b-pinene to the cyclic nitrone was shown to be anti–endo. The
reaction of racemic nitrones ( )-1f–g with the homochiral b-pinene gave the adduct from the (S)-nitrone and the corresponding
imidazole. The adducts 3 undergo retro-1,3-dipolar cycloaddition when heated in the condensed phase or in diphenyl ether to give
the corresponding imidazole and b-pinene. © 2001 Elsevier Science Ltd. All rights reserved.
the cases of isocyanate4 and styrene5 adducts where
1. Introduction
regeneration of the nitrone is a highly efficient process.
1,3-Dipolar cycloadditions have become increasingly
important in recent years, particularly those involving
isoxazolidine cycloadducts, which can be elaborated to
2. Results and discussion
cyclic or acyclic compounds with complete control of
the relative stereochemistry.1 The use of enantiomeri-
Cyclic nitrones 1 were heated for 72 h in xylene in the
presence of a nine-fold excess of (S)-(−)-b-pinene.
cally pure cyclic nitrones in the synthesis of alkaloids,2
and g-aminoalcohols3 is described in the literature.
Homochiral adducts 3a–e were isolated in high yields
Recently we have reported the regio- and diastereose-
by recrystallization from ethanol or by column chro-
lective 1,3-dipolar cycloaddition of chiral nitrones 1
matography in some cases. The reaction of imidazoline
3-oxides 1f–g with pinene in refluxing xylene led mainly
to the formation of corresponding imidazole, therefore
with achiral dipolarophiles such as aryl isocyanates,4
styrene,5 and DMAD.6 Although the synthesis and use
of chiral auxiliaries prepared from (−)-b-pinene are
the reaction was performed in refluxing toluene for 18
known,7,8 no examples of acyclic and cyclic nitrone
days. The yields of 3f and 3g are drastically lower than
adducts with (S)-b-pinene have been reported.
in the cases of 1a–e (see Table 1). Chromatographic
assays during the reaction showed the presence of a
Herein, we report on the regio- and diastereoselective
single adduct with the unreacted nitrone and the corre-
1,3-dipolar cycloaddition of achiral 1a–e and racemic 1f
sponding imidazole. In one case we terminated the
reaction after heating for 68 h and isolated the corre-
sponding adduct and imidazoline 3-oxide expecting that
the latter would be enriched by the enantiomer reacting
slower with (S)-(−)-b-pinene. Unfortunately, the mea-
surements showed the product to be optically inactive.
and 1g imidazoline 3-oxides with (S)-(−)-b-pinene to
give optically active spiro-compounds 3. The adducts
from these reactions were heated in the condensed
phase under vacuum or in diphenyl ether at 200°C to
give b-pinene and the corresponding imidazoles (not,
unfortunately the 3-oxides).9 It was hoped that the
retro-dipolar cycloaddition of 3f and 3g would serve as
a method for the preparation of homochiral 3-imidazo-
line 3-oxides but the reaction was not analogous with
The structure of compounds 3 was determined on the
basis of H and 13C and 2D NMR studies. Elemental
1
analysis for all adducts and MS data for 3g are in
agreement with the proposed structure. Adducts 3a–g
have the same 1H and 13C NMR spectra related to their
* Corresponding author. E-mail: coskun@uludag.edu.tr
0957-4166/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(01)00270-1

1464
N. Cos¸kun et al. / Tetrahedron: Asymmetry 12 (2001) 1463–1467
Table 1. Perhydroimidazo[1,5-b]isoxazoles 3
R
R1
R2
Yield (%)
Mp (°C)
Yield of recovered 1
[h]2D0
a
b
c
d
e
f
4-MeC6H4
4-MeOC6H4
4-MeC6H4
4-MeOC6H4
4-MeOC6H4
4-MeC6H4
4-MeOC6H4
H
H
H
H
H
Ph
Ph
Ph
Ph
85
80
60
47
121.9–122.2
138–139
168–170
115.5–117
140–140.7
194–195
12
+212 (CHCl3, 0.50)
+92 (CHCl3, 0.50)
+137.5 (CHCl3, 0.40)
+93.75 (CHCl3, 0.40)
+100 (CHCl3, 0.40)
+80 (CHCl3, 0.50)
+97.7 (CHCl3, 0.44)
15
3-MeOC6H4
3-MeOC6H4
4-MeOC6H4
Ph
24b
41b
55
20+20b
70b
25a
24a
g
Ph
155.5–158
18+50b
a The reaction was performed under reflux in toluene for 18 days.
b The yield of corresponding imidazole.
1
isoxazolidine and pinene components. In the H NMR
more stable than the anti–exo and syn–exo adducts by
about 4 and 1 kJ/mol, respectively.
spectra of the adducts, the AB system near 2.45 ppm
indicates the 2-spiro regioisomer shown in Scheme 1.
The NOESY spectrum of 3g shows correlations10 (see
Fig. 1) for C(6)H/C(b-3)H, C(a-4)H/C(3a)Ph, C(a-4)H/
C(5)Ph, C(6)H/C(5)Ph which indicates that C(3a) and
C(6) phenyls are cis-oriented.6 The one proton triplet
(J=4.97 Hz) at l 2.11 ppm, was assigned to C(1%)H. Its
NOESY correlations with C(6), C(b-3)H, C(b-4)H,
C(7%) and C(8%) revealed that the preferred orientation
of (S)-b-pinene in the 1,3-dipolar cycloaddition with
cyclic nitrones 1 is anti–endo. The alternative anti–exo
and syn–exo attacks (see Fig. 2) should give the adducts
3% and 3%%% having the bridgehead C(1%)H correlating
with the aromatic ortho protons of the C(3a) phenyl
group. The product of syn–endo attack 3%% would have
the C(1%) proton correlating with C(6)H but the methyl
groups are too far from C(3)H to give cross peaks.
To prove that imidazoles in the reaction mixture are
not products from the fragmentation of adducts 3 we
refluxed adduct 3f in xylene for a week but no conver-
sion to imidazole was observed. Adducts 3f and 3g were
heated in condensed phase at 200°C under vacuum for
1 h to give (S)-(−)-b-pinene and the corresponding
imidazole. The same results were obtained when the
adducts were heated in diphenyl ether. The products
were determined by gas chromatography to be again
b-pinene and the corresponding imidazole.
3. Experimental
Melting points were taken on an Electrothermal Digital
melting point apparatus. Infrared spectra were recorded
on a Mattson 1000 FTIR. Proton and 13C magnetic
resonance spectra were recorded on a Bruker Dpx 400
MHz spectrometer. All spectra were taken in deuteri-
ochloroform. Mass spectrum of 3g was recorded at 70
eV by electron impact on a Fisons VG Platform II
instrument. The optical rotation of the adducts were
measured on a WXG-4 disk polarimeter. Freshly pre-
pared imidazoline 3-oxides were used after recrystalliza-
Figure 1. The stereochemistry of adduct 3g based on selected
NOESY correlations.
tion
from
either
ethanol
or
acetone.
1,4-Di-p-methoxyphenyl-D3-imidazoline N-oxide is a
new compound and was obtained according to the proce-
dure reported by us.11 Yield 48%; mp 216.5–218°C; IR
Molecular modelling studies revealed that the syn–endo
adduct of the (S)-b-pinene should be more stable (the
energy calculated for syn–endo adduct is 163.464 kJ/
mol) than anti–exo adduct 3%, Etotal 168.748 kJ/mol. The
syn–endo adduct is seen to be more stable by 1 kJ/mol
than adduct 3 but, in spite of this the (R)-3-oxide
leading to 3%% seems to dehydrate more easily than the
corresponding (S)-3-oxide. The anti-endo adduct is
wCꢀN 1591 cm−1; H NMR (CDCl3): l ppm 3.71 (3H, s),
1
3.80 (3H, s), 4.65 (2H, t, J=3.63), 5.27 (2H, t, J=3.63),
6.50 (2H, d, J=8.60), 6.85 (2H, d, J=8.60), 6.94 (2H,
d, J=8.60), 8.25 (2H, d, J=8.60). Anal. calcd for
C17H20N2O3: C, 67.98; H, 6.71; N, 9.33. Found: C,
67.65; H, 6.19; N, 8.83%.
Scheme 1.

N. Cos¸kun et al. / Tetrahedron: Asymmetry 12 (2001) 1463–1467
1465
Figure 2. The possible four diastereomers of C(2) spiroisoxazolidines 3a–e and four of the eight possible for 3f and 3g and the
transition states leading to their formation.
3.1. Cycloaddition of imidazoline 3-oxides with (1S)-(−)-
b-pinene. General procedure for the preparation of
3a–g
3.3. Perhydroimidazoisoxazole 3b
Yield 80%; mp 138–139°C; [h]2D0=+92 (c=0.5, CHCl3);
1H NMR (CDCl3): l ppm 0.78 (3H, s), 1.17 (3H, s),
1.46 (1H, d, J=10.22), 1.72 (1H, m), 1.79 (3H, m), 1.98
(1H, t, J=5.42), 2.11 (1H, m), 2.28 (1H, m), 2.51 (2H,
To a solution of imidazoline 3-oxide 1 (1 mmol) in
xylene (S)-(−)-b-pinene (9 mmol) was added and the
mixture was stirred under reflux for 72 h. The solvent
and excess pinene were removed under vacuum and the
residue triturated with ethanol. The solid formed was
purified by recrystallization from ethanol.
JAB=12.36), 3.54 (2H, JAB=8.52), 3.65 (3H, s), 4.37
(2H, JAB=9.80), 6.38 (2H, d, J=8.90), 7.12 (2H, d,
J=8.90), 7.14 (1H, m), 7.24 (2H, t, J=7.44), 7.43 (2H,
d, J=7.45). 13C NMR (CDCl3): l ppm 23.48; 24.84;
27.46; 33.31; 39.02; 40.56; 53.35; 56.08; 58.46; 59.06;
73.31; 78.71; 87.45; 96.57; 114.03; 115.33; 126.08;
127.50; 128.96; 141.57; 143.92; 152.31. Anal. calcd for
C26H32N2O2: C, 77.19; H, 7.97; N, 6.92. Found: C,
77.15; H, 8.10; N, 6.80%.
3.2. Perhydroimidazoisoxazole 3a
Yield 82%; mp 121.9–122.2°C; [h]2D0=+212 (c=0.50,
1
CHCl3); H NMR (CDCl3): l ppm 0.71 (3H, s), 1.10
(3H, s), 1.37 (1H, d, J=10.25), 1.61 (1H, m), 1.72 (1H,
t, J=2.84), 1.76 (2H, m), 1.92 (1H, t, J=3.52), 2.05
(1H, m), 2.09 (3H, s), 2.27 (1H, m), 2.45 (2H, s), 3.52
(2H, s), 4.21 (1H, d, J=9.90), 4.44 (1H, d, J=9.90),
6.25 (2H, d, J=8.44), 6.84 (2H, d, J=8.44), 7.08 (1H,
t, J=8.00), 7.18 (2H, t, J=8.00), 7.37 (2H, d, J=8.00).
13C NMR (CDCl3): l ppm 20.77; 23.48; 24.86; 27.46;
27.50; 33.58; 39.04; 40.55; 53.44; 58.22; 58.46; 72.54;
78.58; 87.40; 112.93; 126.11; 126.26; 127.54; 128.96;
130.06; 143.66; 144.71. Anal. calcd for C26H32N2O: C,
80.37; H, 8.30; N, 7.21. Found: C, 80.25; H, 8.25; N,
7.21%.
3.4. Perhydroimidazoisoxazole 3c
Yield 60%; mp 168–170°C; [h]2D0=+137.5 (c=0.4,
1
CHCl3); H NMR (CDCl3): l ppm 0.84 (3H, s), 1.23
(3H, s), 1.48 (1H, d, J=10.25), 1.68–1.75 (1H, m),
1.81–1.90 (3H, m), 2.03 (1H, t, J=5.43), 2.14–2.19 (1H,
m), 2.21 (3H, s), 2.31–2.43 (1H, m), 2.56 (2H, s), 3.61
(2H, JAB=8.61), 3.79 (3H, s), 4.33 (1H, d, J=9.86),
4.56 (1H, d, J=9.87), 6.36 (2H, d, J=8.41), 6.72 (1H,
dd, J=10.26, 2.14), 6.94 (2H, d, J=8.26), 6.99 (1H, d,
J=8.44), 7.07 (1H, m), 7.18–7.24 (1H, m). 13C NMR
(CDCl3): l ppm 20.25; 22.95; 24.31; 26.93; 32.86; 38.46;

1466
N. Cos¸kun et al. / Tetrahedron: Asymmetry 12 (2001) 1463–1467
40.00; 52.82; 54.83; 57.98; 72.13; 77.96; 86.77; 111.51;
112.08; 112.48; 117.78; 125.71; 129.47; 129.36; 144.16;
145.02; 159.68. Anal. calcd for C27H34N2O2: C, 77.48;
H, 8.19; N, 6.69. Found: C, 77.44; H, 8.23; N, 6.66%.
115.30; 127.22; 135.5; 159.07. Anal. calcd for
C27H34N2O3: C, 74.62; H, 7.89; N, 6.45. Found: C,
74.50; H, 7.63; N, 6.45%.
3.9. 1,4-Di-p-methoxyphenylimidazole 4e
3.5. 4-m-Methoxyphenyl-1-p-tolyl-imidazole 4c
Obtained as the second product from the reaction
mixture of 3e. Yield 20%. Recrystallized from ethanol;
mp 158°C; IR (KBr) wCꢀN 1625 cm−1; 1H NMR
(CDCl3): l ppm 3.80 (3H, s), 3.84 (3H, s), 6.88 (2H, d,
J=8.69), 6.95 (2H, d, J=8.83), 7.30 (1H, s), 7.33 (2H,
s), 7.68 (1H, s), 7.70 (2H, s). 13C NMR (CDCl3): l ppm
55.41, 55.75; 113.34; 114.37; 115.24; 123.35; 126.52;
127.17; 131.24; 135.87; 143.43; 159.20; 159.25.
The compound was isolated from the mother liquor of
compound 3c as an oil. Yield 24%. IR (neat) wCꢀN 1625
1
cm−1. H NMR (CDCl3): l ppm 2.40 (3H, s), 3.86 (3H,
s), 6.46 (1H, d, J=8.35), 7.29 (6H, m), 7.39 (1H, s),
7.49 (1H, s), 7.81 (1H, s). 13C NMR (CDCl3): l ppm
21.43; 55.43; 110.25; 113.79; 117.69; 121.68; 129.85;
130.75; 137.64; 160.38.
3.6. Perhydroimidazoisoxazole 3d
3.10. Perhydroimidazoisoxazole 3f
The compound was purified by column chromatogra-
phy using silica gel as adsorbent and ethyl acetate–
petroleum ether (1:10) as eluent mixture. Yield 47%; mp
The reaction mixture was stirred under reflux in toluene
for 18 days. The product was purified by column
chromatography using silica gel as adsorbent and ethyl
acetate–petroleum ether as eluent. Yield 25%; mp 194–
195°C; [h]2D0=+80 (c=0.5, CHCl3);); 1H NMR
(CDCl3): l ppm 0.75 (3H, s), 1.17 (3H, s), 1.74 (1H, d,
J=10.14), 1.64 (1H, m), 1.82 (3H, m), 2.00 (1H, t,
J=4.70), 2.14 (3H, s), 2.45 (2H, JAB=12.51), 3.95 (2H,
1
115.5–117°C; [h]2D0=+93.75 (c=0.4, CHCl3); H NMR
(CDCl3): l ppm 0.84 (3H, s), 1.23 (3H, s), 1.50 (1H, d,
J=10.22), 1.71–1.90 (4H, m), 2.04 (1H, t, J=5.45), 2.14
(1H, s), 2.19–2.17 (1H, m), 2.34–2.42 (1H, m), 2.52–2.66
(1H, m), 3.5 (1H d, J=8.52), 3.63 (1H d, J=8.55), 3.69
(3H, s), 3.80 (3H, s), 4.3 (1H d, J=9.8), 4.55 (1H, d,
J=9.77), 6.43 (2H d, J=8.88), 6.71–6.77 (3H, m,),
6.94–7.03 (1H, m), 7.08–7.09 (1H, m), 7.17–7.25 (1H,
m). 13C NMR (CDCl3): l ppm 23.5; 24.84; 27.49; 31.12;
33.14; 38.99; 40.51; 53.26; 55.38; 55.97; 58.47; 59.46;
73.49; 78.67; 87.36; 111.94; 112.61; 114.21; 115.31;
118.31; 129.91; 141.48; 145.79; 152.44; 160.23. Anal.
calcd for C27H34N2O3: C, 74.62; H, 7.89; N, 6.45.
Found: C, 75.02; H, 7.78; N, 6.36%.
JAB=8.68), 5.50 (1H, s), 6.29 (2H, d, J=8.20), 6.91
(2H, d, J=8.20), 6.98 (6H, m), 7.08 (2H, m), 7.21 (2H,
d, J=5.76). 13C NMR (CDCl3): l ppm 22.73; 25.42;
26.86; 29.47; 36.11; 41.07; 42.51; 56.10; 60.56; 61.16;
87.86; 89.85; 98.58; 115.57; 128.45; 129.08; 129.62;
129.96; 130.07; 130.21; 131.92; 141.60; 144.95; 146.96.
Anal. calcd for C32H36N2O: C, 82.72; H, 7.81; N, 6.03.
Found: C, 82.34; H, 7.56; N, 5.86%.
3.11. Perhydroimidazoisoxazole 3g
3.7. 1-p-Methoxyphenyl-4-m-methoxyphenylimidazole
4d
Purification as for 3f 24%; mp 155.5–158°C; [h]2D0=
1
+97.7 (c=0.44, CHCl3); H NMR (CDCl3): l ppm 0.81
The product was isolated from the mother liquor of 3d
by flash column chromatography. Yields 41%. Recrys-
tallized from ethanol; mp 82-82.5°C; IR (KBr) wCꢀN
(3H, s), 1.23 (3H, s), 1.56 (1H, d, J=10.25), 1.71 (1H,
m), 1.85 (3H, m), 2.11 (1H, t, J=4.97), 2.20 (1H, m),
2.37 (1H, m) 2.44 (2H, JAB=12.55), 3.69 (3H, s), 4.03
(2H, JAB=8.57), 5.54 (1H, s), 6.39 (2H, d, J=8.97),
6.73 (2H, d, J=8.97), 6.72–7.00 (6H, m), 7.20 (2H, m),
7.33 (2H, m). Anal. calcd for C32H36N2O2: C, 79.96; H,
1
1625 cm−1; H NMR (CDCl3): l ppm 3.82 (3H, s), 3.85
(3H, s), 6.78 (1H, d, J=9.33), 6.95 (2H, d, J=8.75),
7.24–7.35 (4H, m), 7.41 (1H, s), 7.44 (1H, s), 7.74 (1H,
s). 13C NMR (CDCl3): l ppm 55.54; 55.81; 110.27;
113.63; 114.83; 115.30; 117.72; 123.40; 129.93; 130.98;
135.68; 136.14; 143.24; 159.38; 160.40. Anal. calcd for
C17H16N2O2: C, 72.84; H, 5.75; N, 9.99. Found: C,
71.93; H, 6.00; N, 9.85%.
7.55; N, 5.83. Found: C, 79.84; H, 7.51; N, 5.85 m/z:
+
’
480.3 (M , 10.83), 327.2 (4.66), 262.1 (4.1), 225.1 (100),
211.1 (12.33), 193.1 (7.94), 165.1 (2.36), 134.1 (23.76),
121.1 (10.95), 104.1 (8.56), 77.0 (5.49), 69.1 (1.99), 41.0
(2.63).
3.8. Perhydroimidazoisoxazole 3e
3.12. Retro-cycloaddition of perhydroimidazoisoxazoles
in condensed phase: general procedure for preparation
of 3f and 3g
Yield 55%; mp 140–140.7°C; [h]2D0=+100 (c=0.4,
1
CHCl3); H NMR (CDCl3): l ppm 0.85 (3H, s), 1.23
(3H, s), 1.50 (1H, d, J=10.24), 1.69–1.76 (1H, m),
1.83–1.91 (2H, m), 2.03 (1H, t, J=5.44), 2.14 (3H, s),
2.36–2.43 (1H, m), 2.54 (2H, JAB=12.54, 12.52), 3.57
(2H, JAB=8.57, 8.52), 3.71 (3H, s), 3.77 (3H, s), 4.26
(1H, d, J=9.85), 4.51 (1H, d, J=9.85), 6.42 (2H, d,
J=8.81), 6.74 (2H, d, J=8.93), 6.81 (2H, d, J=8.77),
7.34 (2H, d, 8.76). 13C NMR (CDCl3): l ppm 23.50;
24.88; 27.50; 31.12; 33.48; 39.01; 40.55; 53.36; 55.40;
55.97; 58.47; 58.78; 73.10; 78.32; 87.24; 113.96; 114.29;
Compound 3 (0.1 mmol) was placed in a glass sample
vial and heated in a vacuum oven at 200°C for 1 h at
1.3×10−3 mmHg and left to cool at room temperature.
The obtained 4 was extracted with warm hexane (3×2
mL). The extract was concentrated and cooled. The
formed crystals were collected by filtration. The identity
of the obtained imidazoles was determined comparing
their melting points as well as their IR spectra with
those of the authentic samples.

N. Cos¸kun et al. / Tetrahedron: Asymmetry 12 (2001) 1463–1467
1467
3.13. Retro-cycloaddition of perhydroimidazoisoxazoles
3f and 3g in solution
4. (a) Cos¸kun, N. Tetrahedron Lett. 1997, 38, 2299–2302;
(b) Cos¸kun, N. Tetrahedron 1997, 53, 13873–13882.
5. Cos¸kun, N.; Ay, M. Heterocycles 1998, 48, 537–544.
6. The adducts of imidazoline 3-oxides 1 with DMAD were
proved to have cis structure by X-ray analysis: Cos¸kun,
Compound 3 (0.12 mmol.) was dissolved in diphenyl
ether (3 mL) and heated for 1 h at 200°C. The yield of
b-pinene was 65 and 60%, respectively, for 3f and 3g as
determined by GC-FID.
8
8
8
N.; Tat, F. T.; Gu¨ven, O. O.; Ulku¨, D.; Arici, C. Tetra-
hedron Lett. 2000, 41, 5407–5409; Cos¸kun, N.; Tat, F. T.;
8
8
Gu¨ven, O. O. Tetrahedron 2001, 57, 3413–3417.
7. Alencar, K. G.; Filho, U. F. L.; Vasconcellos, M. L. A.
A.; Costa, P. R. R. Synth. Commun. 2000, 30, 455–468.
8. Dumas, F.; Alencar, K.; Mahuteau, J.; Barbero, M. J. L.;
Miet, C.; Gerard, F.; Vasconcellos, M. L. A. A; Costa, P.
R. R. Tetrahedron: Asymmetry 1997, 8, 579–583.
Acknowledgements
Uludag˘ University Research Fund is gratefully
acknowledged for the financial support (Project No
2001-1)
9. The imidazole forms from the thermal dehydration of the
corresponding imidazoline 3-oxide.
10. The assignment for some of the protons of 3g is as
follows; 0.81 (3H, s, C-7%), 1.23 (3H, s, C-8%), 1.56 (1H, d,
J=10.25), 1.71 (1H, m), 1.85 (3H, m), 2.11 (1H, t,
J=4.97, C-1%), 2.20 (1H, m), 2.37 (1H, m) 2.44 (2H,
References
J
AB=12.55, C-3), 3.69 (3H, s, OMe), 4.03 (2H, JAB=
1. March, P.; Figueredo, M.; Font, J.; Gallagher, T.; Milan,
S. J. Chem. Soc., Chem. Commun. 1995, 2097–2098.
2. Goti, A.; Fedi, V.; Nannelli, L.; DeSarlo, F.; Brandi, A.
Synlett 1997, 5, 577.
8.57, C-4), 5.54 (1H, s, C-6), 6.39 (2H, d, J=8.97, N-Ph
ortho), 6.73 (2H, d, J=8.97, N-phenyl meta H), 7.00 (6H,
m, C-3a and C-6 phenyl meta and para H), 7.20 (2H, m,
C-6 phenyl ortho H), 7.33 (2H, m C-3a phenyl ortho H)
11. Cos¸kun, N.; Asutay, A. Chim. Acta Turc. 1997, 25,
69–72.
3. Cicchi, S.; Crea, S.; Goti, A.; Brandi, A. Tetrahedron:
Asymmetry 1997, 8, 293–301.
.