TMSOTf-catalyzed stereoselective isomerization of acetates of the Baylis-Hillman adducts

Article abstract of DOI:10.1055/s-2000-6372

TMSOTf-catalyzed isomerization of acetates of the Baylis-Hillman adducts, i.e. methyl 3-acetoxy-3-aryl-2-methylenepropanoates and 3-acetoxy-3- aryl-2-methylenepropanenitriles pro-viding methyl (2E)-2-(acetoxymethyl)-3- arylprop-2-enoates and (2E)-2-(aceto

Full text of DOI:10.1055/s-2000-6372

PAPER
545
TMSOTf-Catalyzed Stereoselective Isomerization of Acetates of the Baylis-
Hillman Adducts
*
Deevi Basavaiah, Kannan Muthukumaran, Bandaru Sreenivasulu
School of Chemistry, University of Hyderabad, Hyderabad-500 046, India
Received 8 September 1999; revised 15 November 1999
3
3
-acetoxy-3-aryl-2-methylenepropanoates and 3-acetoxy-
-aryl-2-methylenepropanenitriles with trimethylsilyl tri-
Abstract: TMSOTf-catalyzed isomerization of acetates of the
Baylis–Hillman adducts, i.e. methyl 3-acetoxy-3-aryl-2-methyl-
enepropanoates and 3-acetoxy-3-aryl-2-methylenepropanenitriles
pro-viding methyl (2E)-2-(acetoxymethyl)-3-arylprop-2-enoates
and (2E)-2-(acetoxymethyl)-3-arylprop-2-enenitriles, respectively,
is described.
fluoromethanesulfonate.
-
H
R
COOMe H
Nu
Nu
OAc
+
Z= COOMe
Z
Key words: Baylis-Hillman reaction, trimethylsilyl trifluoro-
Nu
R
COOMe
major
minor
minor
R
methanesulfonate, isomerization, stereoselectivity, 1,2-interaction
-
H
R
Nu
H
CN
Nu
Nu
+
Z= CN
CN
R
Synthetic applications of trimethylsilyl trifluoromethane-
sulfonate (TMSOTf) in a variety of stereoselective reac-
tions and transformations have been well documented in
the literature and in fact, TMSOTf has become a reagent
-
-
major
-
-
Nu = H, R, Br (MgBr2), P(OEt)3
Scheme
of choice to the organic chemists in recent years for con-
ducting various interesting organic reactions.1 The Bay- Accordingly, we first examined the isomerization of
lis-Hillman reaction is an important carbon-carbon bond methyl 3-acetoxy-2-methylene-3-phenylpropanoate (1a)
forming and atom economy reaction, providing a useful under the catalytic influence of TMSOTf. The best results
class of molecules possessing chemospecific functional were obtained when the isomerization of 1a (1 mmol) was
groups (Equation 1) which have been successfully used in carried out in the presence of TMSOTf (11 mol%) in
-6
7
-20
dichloromethane at room temperature for 2 hours, thus
providing the required methyl (2E)-2-(acetoxymethyl)-3-
phenylprop-2-enoate (2a) in 100% (E)-selectivity as evi-
denced by the H NMR spectral analysis. Encouraged by
this result, we then transformed a representative class of
methyl 3-acetoxy-3-aryl-2-methylenepropanoates under
a variety of stereoselective processes. As a part of our
research program aimed at the development of the Bayl-
is-Hillman reaction
1
4-20
as a source of stereo-selective
1
21
processes, we herein report trimethylsilyl trifluo-
romethanesulfonate catalyzed stereoselective isomeriza-
tion of the acetates of the Baylis-Hillman adducts, i.e.
methyl 3-acetoxy-3-aryl-2-methylenepropanoates and 3- the catalytic influence of TMSOTf into methyl (2E)-2-
acetoxy-3-aryl-2-methylenepropanenitriles into methyl (acetoxymethyl)-3-arylprop-2-enoates (Equation 2, Ta-
(
2
2E)-2-(acetoxymethyl)-3-arylprop-2-enoates and (2E)- ble). It is worth mentioning that the isomerization of me-
-(acetoxymethyl)-3-arylprop-2-enenitriles, respectively. thyl 3-acetoxy-3-aryl-2-methylenepropanoates to methyl
-(acetoxymethyl)-3-arylprop-2-enoates was reported
2
earlier in high (E)-selectivity, under the catalytic influ-
ence of DABCO.
O
OH
22-24
Z
+
H
DABCO
Z
R
R
OAc
Z= COOMe, CN, COMe etc. R= aryl or alkyl
H
COOMe
OAc
COOMe TMSOTf (cat.)
CH Cl , r.t. 2h
Ar
Equation 1
2
2
Ar
1a-1f
2a-2f
Ar = phenyl, 4-methylphenyl, 4-ethylphenyl,
We have observed a remarkable reversal of stereochemi-
cal directive effects from ester group to nitrile group in a
number of stereoselective transformations (Scheme) in-
4-isopropylphenyl, 4-chlorophenyl, 2-methylphenyl
Equation 2
1
6-19
volving acetates of the Baylis-Hillman adducts.
With
a view to study the stereochemical directive effects of es-
ter and nitrile groups in the TMSOTf-catalyzed reactions
and with a view to examine the application of TMSOTf as
a catalyst for stereoselective isomerization of acetates of
the Baylis-Hillman adducts, we have undertaken the in-
vestigation of the reactions of representative methyl
With a view to understanding the stereochemical directive
effect of the nitrile group in the TMSOTf catalyzed reac-
tions, we next examined the isomerization of 3-acetoxy-2-
methylene-3-phenylpropanenitrile with
a
catalytic
amount of TMSOTf at room temperature for 2 hours. This
reaction provided a simple and convenient synthesis of the
Synthesis 2000, No. 4, 545–548 ISSN 0039-7881 © Thieme Stuttgart · New York

5
46
D. Basavaiah et al.
PAPER
desired
2-(acetoxymethyl)-3-phenylprop-2-enenitrile Claisen type rearrangement (transition state models I, II,
with exclusive (E)-stereoselectivity (Equation 3) in high III, and IV). In the case of molecules 1, the unusual 1,2-
yields. The (E)-stereochemistry was assigned on the basis interaction may be more predominant than the classical
of a 2D NOESY NMR experiment. This reaction clearly 1,3-interaction (transition state models I, II) leading to
demonstrates that there is a reversal in the stereochemical (E)-selectivity. In the case of molecules 3, however, the
directive effect of the nitrile group with respect to the ester classical 1,3- interaction may be more predominant than
group. We then synthesized a representative class of (2E)- the unusual 1,2-interaction (transition state models III,
2
-(acetoxymethyl)-3-arylprop-2-enenitriles via TMSOTf IV) resulting in (E)- selectivity.26
induced isomerization of various 3-acetoxy-3-aryl-2-me-
thylenepropanenitriles (Equation 3, Table). Our attempts
to isomerize methyl 3-acetoxy-2-methyleneoctanoate and
Another possible explanation for the reversal of stereo-
chemical directive effects of the nitrile group with respect
to the ester group is that the products are those of thermo-
dynamic control in all these cases. That is, the more steri-
cally demanding ester group requires a particular
conformation for optimal conjugation compared to the
slim cyano group with local cylindrical symmetry. Thus,
the molecules 1a-f provide trisubstituted alkenes 2a-f
having the aryl group trans to the ester group, whereas
compounds 3a-f produce trisubstituted alkenes 4a-f hav-
ing the aryl group cis to the nitrile group.
3
-acetoxy-2-methyleneoctanenitrile under the catalytic
influence of TMSOTf were unsuccessful.
OAc
H
OAc
CN TMSOTf (cat.)
CH Cl , r.t. 2h
Ar
2
2
Ar
CN
4a-4f
3a-3f
Ar = phenyl, 4-methylphenyl, 4-ethylphenyl,
4-isopropylphenyl, 4-chlorophenyl, 2-methylphenyl
Equation 3
OTf
SiMe3
Ar
CH3
MeOOC
Ar
O
O
H
H
OTf
O
CH
3
O
O
SiMe3
COOMe
The reversal of stereochemical directive effects from the
ester group to the nitrile group is consistent with our ear-
lier results and can be possibly explained through the
H
H
I
II
OTf
SiMe3
Ar
CH3
NC
Ar
OTf
O
CH3
O
O
SiMe3
CN
III
IV
Table TMSOTf-Catalyzed Isomerization Acetates of the Baylis−
a,b,c
Hillman Adducts
d
In conclusion, we have stereoselectively transformed ace-
tates of the Baylis-Hillman adducts, i.e., methyl 3-ace-
toxy-3-aryl-2-methylenepropanoates and 3-acetoxy-3-
aryl-2-methylenepropanenitriles under the catalytic influ-
ence of trimethylsilyl trifluoromethanesulfonate into
methyl (2E)-2-(acetoxymethyl)-3-arylprop-2-enoates and
(2E)-2-(acetoxymethyl)-3-arylprop-2-enenitriles, respec-
tively. Thus, we have demonstrated the synthetic applica-
tions of trimethylsilyl trifluoromethanesulfonate, and the
importance of the Baylis-Hillman adducts in stereoselec-
tive organic synthesis.
Substrate Ar
Z
Product Yield (%)
COOMe 2a2
1
73
65
88
83
80
77
85
68
78
74
65
84
1
1
1
1
1
1
3
3
3
3
3
3
a
b
c
d
e
f
a
b
c
d
e
f
phenyl
e
4-methylphenyl
4-ethylphenyl
4-isopropylphenyl
4-chlorophenyl
2-methylphenyl
phenyl
4-methylphenyl
4-ethylphenyl
4-isopropylphenyl
4-chlorophenyl
2-methylphenyl
COOMe 2b
COOMe 2ce
e
COOMe 2d
COOMe 2ee
e,f
h
g
COOMe 2f
CN
CN
CN
CN
CN
CN
4a
i
4b
4ci
i
4d
4ei
4f i
a
IR spectra were recorded on JASCO-FT-IR model 5300 spectro-
All reactions were carried out on 1 mmol scale of acetates of the Bay-
1
13
meter using samples as neat liquids. H NMR (200 MHz) and
C
lis−Hillman adducts with TMSOTf (11 mol %) at r.t. for 2 h.
b
NMR (50 MHz) spectra were recorded in CDCl on a Bruker-AC-
All compounds were obtained as colorless liquids and characterized
3
1
13
200 spectrometer using TMS as internal standard. Elemental analy-
ses were recorded on Perkin-Elmer 240C-CHN analyzer. The re-
quired acetates of the Baylis-Hillman adducts (1 and 3) were
prepared by the reaction of the corresponding Baylis-Hillman ad-
ducts (obtained from corresponding aldehydes via the reaction with
methyl acrylate and acrylonitrile, respectively, in presence of a cat-
by IR, H NMR, C NMR spectral data and microanalysis.
c 1
d
13
H and C NMR indicate the absence of any (Z)-isomer.
Isolated yield of the products after column chromatography (3%
EtOAc in hexanes).
e
(
E)-Stereochemistry was assigned on the basis of the chemical shift
1
value of the olefinic proton in H NMR and allylic methylene carbon
1
3
25
7,8
in C NMR spectra in analogy with 2a.
alytic amount of DABCO according to the literature procedure)
f
This compound contains ≈10% impurity and was further purified by
preparative HPLC (Shim-Pack PREP-ODS column, (20 mm x 25 cm),
MeOH, flow rate 3mL/min, Rt: 20 min
with acetyl chloride in presence of pyridine.
Isomerization of Acetates of the Baylis-Hillman Adducts; Gen-
eral Procedure
g
Isolated yield after purification by preparative HPLC.
h
(
E)-Stereochemistry was assigned by a 2D NOESY experiment.
To a stirred solution of acetates of the Baylis-Hillman adduct (1a-
i
13
(
E)-Stereochemistry was assigned on the basis of the C NMR
f and 3a-f, 1 mmol) in CH Cl (2 mL), was added TMSOTf (0.02
2
2
chemical shift value of the allylic methylene carbon in comparison
mL, 11 mol %, 0.0245 g)) at r.t. After 2 h, the reaction mixture was
with that of 4a.25
Synthesis 2000, No. 4, 545–548 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
TMSOTf-Catalyzed Stereoselective Isomerization of Acetates of the Baylis-Hillman Adducts
547
diluted with H O (3 mL) and extracted with Et O (3 x 10 mL). The
Anal. Calcd for C H O Cl: C, 58.11, H, 4.88. Found: C, 58.38, H,
2
2
13 13
4
combined organic layer was dried (Na SO ), the solvent was evap-
4.86.
2
4
orated and the crude product thus obtained was purified by column
chromatography (silica gel, 3% EtOAc in hexanes) to provide the
desired products (2a-f and 4a-f).
Methyl (2E)-2-(Acetoxymethyl)-3-(2-methylphenyl)prop-2-
enoate (2f)
Colorless liquid; yield: 77%; R = 0.57 (hexanes/EtOAc, 9:1).
f
Methyl (2E)-2-(Acetoxymethyl)-3-phenylprop-2-enoate (2a)
IR (neat): nmax = 1740, 1722, 1637 cm-1.
Colorless liquid; yield: 73%; R = 0.58 (hexanes/EtOAc, 9:1).
f
1
H NMR (CDCl ): d = 2.07 (s, 3H), 2.31 (s, 3H), 3.86 (s, 3H), 4.83
-
1
3
IR (neat): nmax = 1741, 1720, 1635 cm .
(
s, 2H), 7.16-7.37 (m, 4H), 8.06 (s, 1H).
1
H NMR (CDCl ): d = 2.10 (s, 3H), 3.84 (s, 3H), 4.95 (s, 2H), 7.39
13
3
C NMR (CDCl ): d = 19.81, 20.75, 52.12, 59.36, 125.84, 127.43,
3
(
s, 5H), 7.98 (s, 1H).
1
28.54, 129.24, 130.11, 133.46, 136.91, 144.53, 166.95, 170.44.
1
3
C NMR (CDCl ): d = 20.78, 52.14, 59.26, 126.77, 128.64, 129.37,
3
Anal. Calcd for C H O : C, 67.73, H, 6.50. Found: C, 67.83, H,
1
4
16
4
1
29.47, 134.19, 145.25, 167.19, 170.49.
6
.55.
Anal. Calcd for C H O : C, 66.65, H, 6.02. Found: C, 66.89, H,
13
14
4
6
.05.
(
2E)-2-(Acetoxymethyl)-3-phenylprop-2-enenitrile (4a)
Colorless liquid; yield: 85%; R = 0.55 (hexanes/EtOAc, 9:1).
f
Methyl (2E)-2-(Acetoxymethyl)-3-(4-methylphenyl)prop-2-
enoate (2b)
IR (neat): nmax = 2216, 1747, 1626 cm-1.
1
H NMR (CDCl ): d = 2.16 (s, 3H), 4.82 (s, 2H), 7.23 (s, 1H), 7.45
Colorless liquid; yield: 65%; R = 0.56 (hexanes/EtOAc, 9:1).
3
f
(
m, 3H), 7.79 (m, 2H).
-
1
IR (neat): nmax = 1740, 1718, 1633 cm .
1
3
C NMR (CDCl ): d = 20.51, 65.02, 105.88, 117.04, 128.81,
1
3
H NMR (CDCl ): d = 2.11 (s, 3H), 2.39 (s, 3H), 3.85 (s, 3H), 4.98
3
1
29.02, 130.94, 132.52, 147.05, 169.99.
(
s, 2H), 7.22 (d, 2H, J = 8.0 Hz), 7.30 (d, 2H, J = 8.0 Hz), 7.96 (s,
Anal. Calcd for C H NO : C, 71.63, H, 5.51, N, 6.96. Found: C,
1
H).
12 11
2
7
1.31, H, 5.53, N, 6.93.
1
3
C NMR (CDCl ): d = 20.75, 21.22, 52.03, 59.34, 125.74, 129.37,
3
1
29.50, 131.33, 139.87, 145.37, 167.31, 170.49.
(
2E)-2-(Acetoxymethyl)-3-(4-methylphenyl)prop-2-enenitrile
Anal. Calcd for C H O : C, 67.73, H, 6.50. Found: C, 67.86, H,
(4b)
14
16
4
6
.49.
Colorless liquid; yield: 68%; R = 0.53 (hexanes/EtOAc, 9:1).
f
-
1
IR (neat): nmax = 2214, 1745, 1625 cm .
Methyl (2E)-2-(Acetoxymethyl)-3-(4-ethylphenyl)prop-2-
enoate (2c)
1
H NMR (CDCl ): d = 2.14 (s, 3H), 2.39 (s, 3H), 4.80 (s, 2H), 7.18
3
(
s, 1H), 7.24 (d, 2H, J = 8.2 Hz), 7.69 (d, 2H, J = 8.2 Hz).
Colorless liquid; yield: 88%; R = 0.52 (hexanes/EtOAc, 9:1).
f
1
3
-
1
C NMR (CDCl ): d = 20.68, 21.48, 65.36, 104.56, 117.43, 129.22,
IR (neat): nmax = 1741, 1718, 1633 cm .
3
1
29.64, 129.92, 141.76, 147.35, 170.20.
1
H NMR (CDCl ): d = 1.25 (t, 3H, J = 7.6 Hz), 2.11 (s, 3H), 2.68 (q,
3
Anal. Calcd for C H NO : C, 72.54, H, 6.09, N, 6.51. Found: C,
2
7
H, J = 7.6 Hz), 3.85 (s, 3H), 4.97 (s, 2H), 7.24 (d, 2H, J = 8.0 Hz),
.32 (d, 2H, J = 8.0 Hz), 7.97 (s, 1H).
13 13
2
7
2.74, H, 6.07, N, 6.55.
1
3
C NMR (CDCl ): d = 15.12, 20.76, 28.60, 52.03, 59.36, 125.66,
3
(
2E)-2-(Acetoxymethyl)-3-(4-ethylphenyl)prop-2-enenitrile (4c)
1
28.16, 129.60, 131.52, 145.43, 146.13, 167.31, 170.53.
Anal. Calcd for C H O : C, 68.69, H, 6.92. Found: C, 68.54, H,
Colorless liquid; yield: 78%; R = 0.49 (hexanes/EtOAc, 9:1).
15
18
4
f
6
.96.
-
1
IR (neat): nmax = 2214, 1747, 1625 cm .
1
H NMR (CDCl ): d = 1.25 (t, 3H, J = 8.0 Hz), 2.15 (s, 3H), 2.69 (q,
Methyl (2E)-2-(Acetoxymethyl)-3-(4-isopropylphenyl)prop-2-
enoate (2d)
3
2
7
H, J = 8.0 Hz), 4.81 (s, 2H), 7.20 (s, 1H), 7.28 (d, 2H, J = 8.0 Hz),
.73 (d, 2H, J = 8.0 Hz).
Colorless liquid; yield: 83%; R = 0.50 (hexanes/EtOAc, 9:1).
f
1
3
-
1
C NMR (CDCl ): d = 14.97, 20.52, 28.66, 65.21, 104.44, 117.34,
IR (neat): nmax = 1741, 1718, 1631 cm .
3
1
28.30, 129.19, 130.02, 147.22, 147.82, 170.03.
1
H NMR (CDCl ): d = 1.26 (d, 6H, J = 6.8 Hz), 2.10 (s, 3H), 2.94
3
Anal. Calcd for C H NO : C, 73.34, H, 6.59, N, 6.11. Found: C,
7
(
m, 1H), 3.84 (s, 3H), 4.97 (s, 2H), 7.20-7.45 (m, 4H), 7.96 (s, 1H).
14 15
2
3.52, H, 6.54, N, 6. 09.
1
3
C NMR (CDCl ): d = 20.82, 23.66, 33.95, 52.07, 59.44, 125.74,
3
1
26.80, 129.68, 131.71, 145.44, 150.77, 167.36, 170.58.
(
2E)-2-(Acetoxymethyl)-3-(4-isopropylphenyl)prop-2-ene-
Anal. Calcd for C H O : C, 69.55, H, 7.30. Found: C, 69.30, H,
16
20
4
nitrile (4d)
7
.28.
Colorless liquid; yield: 74%; R = 0.47 (hexanes/EtOAc, 9:1).
f
-
1
IR (neat): nmax = 2214, 1747, 1626 cm .
Methyl (2E)-2-(Acetoxymethyl)-3-(4-chlorophenyl)prop-2-
enoate (2e)
1
H NMR (CDCl ): d = 1.27 (d, 6H, J = 8.0 Hz), 2.15 (s, 3H), 2.95
3
(
m, 1H), 4.81 (s, 2H), 7.20 (s, 1H), 7.30 (d, 2H, J = 8.2 Hz), 7.74 (d,
Colorless liquid; yield: 80%; R = 0.61 (hexanes/EtOAc, 9:1).
f
2
H, J = 8.2 Hz).
-
1
IR (neat): nmax = 1740, 1720, 1637 cm .
1
3
C NMR (CDCl ): d = 20.66, 23.61, 34.11, 65.35, 104.67, 117.44,
1
3
H NMR (CDCl ): d = 2.10 (s, 3H), 3.85 (s, 3H), 4.92 (s, 2H), 7.25-
3
1
27.04, 129.37, 130.29, 147.33, 152.58, 170.17.
7
.46 (m, 4H), 7.91 (s, 1H).
Anal. Calcd for C H NO : C, 74.05, H, 7.04, N, 5.76. Found: C,
1
3
15 17
2
C NMR (CDCl ): d = 20.82, 52.31, 59.05, 127.32, 129.00, 130.73,
3
7
3.74, H, 7.07, N, 5.73.
1
32.62, 135.71, 143.89, 167.02, 170.51.
Synthesis 2000, No. 4, 545–548 ISSN 0039-7881 © Thieme Stuttgart · New York

5
48
D. Basavaiah et al.
PAPER
(
(
2E)-2-(Acetoxymethyl)-3-(4-chlorophenyl)prop-2-enenitrile
4e)
(7) Ciganek, E. In Organic Reactions, Vol. 51; Paquette, L. A.,
Ed.; Wiley: New York, 1997; pp 201-350.
Colorless liquid; yield: 65%; R = 0.55 (hexanes/EtOAc, 9:1).
(8) Basavaiah, D.; Dharma Rao, P.; Suguna Hyma, R.
Tetrahedron 1996, 52, 8001.
f
-
1
IR (neat): nmax = 2212, 1743, 1624 cm .
(
9) Drewes, S. E.; Roos, G. H. P. Tetrahedron 1988, 44, 4653.
1
H NMR (CDCl ): d = 2.15 (s, 3H), 4.80 (s, 2H), 7.17 (s, 1H), 7.42
d, 2H, J = 8.8 Hz), 7.72 (d, 2H, J = 8.8 Hz).
3
(10) Chamakh, A.; Amri, H. Tetrahedron Lett. 1998, 39, 375.
11) Matsumoto, S.; Okubo, Y.; Mikami, K. J. Am. Chem. Soc.
1998, 120, 4015.
12) Aggarwal, V. K.; Mereu, A.; Tarver, G. J.; McCague, R. J.
Org. Chem. 1998, 63, 7183.
13) Barrett, A. G. M.; Cook, A. S.; Kamimura, A. Chem.
Commun. 1998, 2533.
14) Basavaiah, D.; Bakthadoss, M.; Pandiaraju, S. Chem.
Commun. 1998, 1639.
15) Basavaiah, D.; Krishnamacharyulu, M.; Suguna Hyma, R.;
Sarma, P. K. S.; Kumaragurubaran, N. J. Org. Chem. 1999,
64, 1197.
16) Basavaiah, D.; Sarma, P. K. S.; Bhavani, A. K. D. J. Chem.
Soc., Chem. Commun. 1994, 1091.
17) Basavaiah, D.; Bhavani, A. K. D.; Sarma, P. K. S.; Pandiaraju,
S. Synlett 1995, 243.
(
(
(
(
(
(
1
3
C NMR (CDCl ): d = 20.71, 65.04, 106.75, 116.93, 129.34,
3
1
30.45, 131.10, 137.23, 145.72, 170.20.
Anal. Calcd for C H NO Cl: C, 61.16, H, 4.28, N, 5.94. Found: C,
6
12
10
2
1.02, H, 4.27, N, 5.99.
(
(
2E)-2-(Acetoxymethyl)-3-(2-methylphenyl)prop-2-enenitrile
4f)
Colorless liquid; yield: 84%; R = 0.53 (hexanes/EtOAc, 9:1).
f
-
1
IR (neat): nmax = 2218, 1747, 1624 cm .
(
1
H NMR (CDCl ): d = 2.16 (s, 3H), 2.35 (s, 3H), 4.83 (s, 2H), 7.09-
3
7
.50 (m, 4H), 7.83 (m, 1H).
(
1
3
C NMR (CDCl ): d = 19.58, 20.65, 64.89, 107.95, 116.87, 126.32,
3
1
27.79, 130.46, 130.59, 131.83, 137.26, 146.13, 170.15.
(18) Basavaiah, D.; Pandiaraju, S. Tetrahedron 1996, 52, 2261.
(
19) Basavaiah, D.; Sarma, P. K. S. J. Chem. Soc., Chem.
Commun. 1992, 955.
20) Basavaiah, D.; Krishnamacharyulu, M.; Suguna Hyma, R.;
Pandiaraju, S. Tetrahedron Lett. 1997, 38, 2141.
Anal. Calcd for C H NO : C, 72.54, H, 6.09, N, 6.51. Found: C,
1
3
13
2
7
2.87, H, 6.12, N, 6.49.
(
Acknowledgement
(21) The (E)-stereochemistry of this molecule was assigned on the
1
13
basis of H and C NMR spectral data in comparison with
We thank CSIR (New Delhi) for funding this project. KMK thanks
UGC (New Delhi) and BS thanks CSIR (New Delhi) for their rese-
arch fellowships. We also thank UGC (New Delhi) for the Special
Assistance Program in Organic Chemistry in the School of Chemi-
stry, University of Hyderabad.
22,23
literature values.
(
(
(
22) Manson, P. H.; Emslie, N. D. Tetrahedron 1994, 41, 12001.
23) Foucaud, A.; El Guemmout, F. Bull. Soc. Chim. Fr. 1989, 403.
24) Foucaud reported similar isomerization using metal salts (1
equiv) under the catalytic influence of benzyltriethyl-
2
3
ammonium chloride (4 mol %).
1
3
(
25) In the C NMR spectra of trisubstituted olefins the allylic
References and Notes
carbon cis to aryl group appears upfield while the same carbon
1
7,27
13
(
(
(
(
(
(
1) Ihara, M.; Suzuki, S.; Taniguchi, N.; Fukumoto, K. J. Chem.
Soc., Chem. Commun. 1993, 755.
2) Oishi, M.; Aratake, S.; Yamamoto, H. J. Am. Chem. Soc.
trans to aryl group appears downfield.
The C NMR
spectral data indicate the absence of any (Z)-isomer in the case
of molecules 2a and 4a.
1998, 120, 8271.
(26) We have recently invoked the possibility of unusual 1,2-
interactions in the Johnson-Claisen rearrangement to explain
the stereoselectivity. See: Basavaiah, D.; Pandiaraju, S.;
Krishnamacharyulu, M. Synlett 1996, 747.
(27) Funabiki, T.; Hosomi, H.; Yoshida, S.; Tarama, K. J. Am.
Chem. Soc. 1982, 104, 1560.
3) Procopiou, P. A.; Baugh, S. P. D.; Flack, S. S.; Inglis, G. G. A.
Chem. Commun. 1996, 2625.
4) Kobayashi, M.; Masumoto, K.; Nakai, E.; Nakai, T.
Tetrahedron Lett. 1996, 37, 3005.
5) Hunter, R.; Michael, J. P.; Tomlinson, G. D. Tetrahedron
1994, 50, 871.
6) Fujii, N.; Otaka, A.; Ikemura, O.; Akaji, K.; Funakoshi, S.;
Hayashi, Y.; Kuroda, Y.; Yajima, H. J. Chem. Soc., Chem.
Commun. 1987, 274.
Article Identifier:
1437-210X,E;2000,0,04,0545,0548,ftx,en;Z06599SS.pdf
Synthesis 2000, No. 4, 545–548 ISSN 0039-7881 © Thieme Stuttgart · New York