Thermal ene reactions of methyl 3,3,3-trifluoro-2-R-sulfonyliminopropionates. Synthesis of γ,δ-unsaturated derivatives of α-amino α-trifluoromethylcarboxylic acids

Article abstract of DOI:10.1023/A:1011373403583

Thermal ene reactions of methyl 3,3,3-trifluoro-2-methanesulfonyliminopropionate and methyl 2-benzenesulfonylimino-3,3,3-trifluoropropionate with terminal alkenes afford derivatives of γ,δ-unsaturated α-amino α-trifluoromethylcarboxylic acids in one step.

Full text of DOI:10.1023/A:1011373403583

Russian Chemical Bulletin, International Edition, Vol. 50, No. 6, pp. 1041—1043, June, 2001
1041
Thermal ene reactions of
methyl 3,3,3-trifluoro-2-R-sulfonyliminopropionates.
Synthesis of γ,δ-unsaturated derivatives of
α-amino α-trifluoromethylcarboxylic acids
«
N. M. Kobel´kova, S. N. Osipov, and A. F. Kolomiets
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
2
8 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5085. E-mail: osipov@ineos.ac.ru
Thermal ene reactions of methyl 3,3,3-trifluoro-2-methanesulfonyliminopropionate and
methyl 2-benzenesulfonylimino-3,3,3-trifluoropropionate with terminal alkenes afford deriva-
tives of γ,δ-unsaturated α-amino α-trifluoromethylcarboxylic acids in one step.
Key words: unsaturated α-amino acids, imino-ene reaction, methyl 3,3,3-trifluoro-2-R-
sulfonyliminopropionates, terminal alkenes.
Unsaturated α-CF -α-amino acids, like their satu-
namely, methyl 3,3,3-trifluoro-2-R-sulfonylimino-
propionates 2 (R = Me and Ph),9 as an alternative
method for the synthesis of γ,δ-unsaturated α-amino-
α-trifluoromethylcarboxylic acids.
3
rated analogs, are used in searching for new irreversible
1
inhibitors of pyridoxal-phosphate—dependent enzymes
2
3
and in the syntheses of peptidomimetics. Recently, we
have shown that these compounds can be used to pre-
pare new promising biologically active substances. In
the presence of ruthenium carbene complexes, unsatur-
ated N-alkenyl-α-amino α-trifluoromethylcarboxylic ac-
ids are easily involved in the ring-closure metathesis of
olefins to give dehydroderivatives of five-, six-, and
seven-membered cyclic α-imino α-trifluoromethyl-
carboxylic acids in high yields.
H
F C
3
N
Ts
N
SO R
2
RO C
MeO C
2
2
1
2a,b
R = Me (a), Ph (b)
Unlike glyoxylate imines, imines 2 react with isobu-
tylene even at –30 °C; the reactions are completed upon
warming the reaction mixtures to ∼ 20 °C, giving deriva-
tives of dehydroleucine 3 in good yields (Scheme 1).
At present, unsaturated α-amino α-trifluoromethyl-
carboxylic acids are mainly obtained by the reactions of
methyl 2-acyliminotrifluoropropionates with alkenyl-
magnesium halides.4,5 This method has three limita-
tions, which include, first, accessibility of alkenyl ha-
lides for the synthesis of organometallic derivatives;
second, the free-radical mechanism of the formation of
Grignard reagents, which sometimes induces undesir-
able side processes; and third, the high reactivities of
the Grignard reagents with respect to many functional
groups, which precludes involvement of different
functionalized alkenyl halides in the Grignard reactions.
In the last two decades, ene reactions of imines have
become rather important in synthetic organic chemistry
as an efficient way to the formation of C—C bonds.
Intra- and intermolecular ene syntheses have successfully
been used in the synthesis of various natural compounds,6
Scheme 1
F C
3
N
SO R
2
–30 → 20 °C
MeO C
2
2
a,b
F C
3
CO Me
2
NHSO R
2
3
3
a (61%)
b (65%)
2-Phenylpropene and methylidenecycloalkanes also
react easily with imines 2 at 20 °C to give products
(4—8) in preparative yields (Scheme 2).
When a mixture of 2-phenylpropene and tosylimine 1
is kept at 20 °C for five days, no corresponding product of
the ene reaction is formed.10 Low-reactive linear terminal
olefins react with imines 2 at 80—100 °C. Thus, the
reactions of benzenesulfonylimine 2b with 4-bromo-
7
including amino acids. The latter are most often synthe-
sized from glyoxylate tosylimines, whose thermal reac-
tions with terminal olefins (even with such reactive ones
as isobutylene) require temperatures above 110 °C.8
In the present communication, we report for the first
time the results of the study of thermal ene reactions of
α-CF -containing analogs of glyoxylate tosylimines 1,
3
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 997—999, June, 2001.
066-5285/01/5006-1041 $25.00 © 2001 Plenum Publishing Corporation
1

1
042
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 6, June, 2001
Kobel´kova et al.
Scheme 2
chemical shifts (ppm) were referenced to HMDS as the internal
standard and CF COOH as the external standard, respectively.
3
CF3
The Rf values were determined using Merck TLC plates
(60 F-254, 0.25 mm). The substances were purified by column
chromatography on silica gel (Kieselgel 60, 0.063—0.200 mm)
in mixtures of ethyl acetate with light petroleum.
Ph
CF3
CO Me
2
CO Me
2
NHSO R
NHSO R
2
2
4
4
a (78%)
b (80%)
7a (79%)
7b (84%)
Synthesis of compounds 3 (general procedure). Isobutylene
(0.06 mol) was passed in a solution of imine 2 (0.02 mol) in
10 mL of CH Cl at –30 °C. The reaction mixture was kept at
Ph
2
2
–
30 °C for 2 h and then warmed to ∼ 20 °C. The solvent was
removed in vacuo, and the residue was crystallized by tritura-
tion with hexane.
Methyl 4-methyl-2-methylsulfonylamino-2-trifluoromethyl-
2
CH Cl2
2
CH Cl2
2
pent-4-enoate (3a). Yield 61%, m.p. 70—73 °C, R 0.26 (ethyl
f
1
acetate : hexane, 1 : 3). H NMR (acetone-d ), δ: 7.01 (br.s,
6
1
H, NH); 4.97 (m, 1 H, =CH ); 4.90 (m, 1 H, =CH ); 3.81
2 2
n
CH Cl2
CH Cl2
(s, 3 H, OMe); 3.10 (s, 3 H, Me); 3.03, 2.79 (both d,
2
2
2
AB system, 1 H each, CH , JH,H = 13.8 Hz); 1.80 (s, 3 H,
2
Me). 19F NMR (acetone-d ), δ: 9.08 (s, CF ). Found (%):
CF3
CO Me
6
3
CF3
CO Me
C, 37.39; H, 4.62; N, 4.73. C H F NO S. Calculated (%):
9 14 3 4
C, 37.37; H, 4.84; N, 4.84.
Methyl 4-methyl-2-phenylsulfonylamino-2-trifluoromethyl-
2
n
2
NHSO R
2
NHSO R
2
pent-4-enoate (3b). Yield 65%, m.p. 75—78 °C, R 0.42 (ethyl
f
5
5
6
6
a (n = 1; 74%)
b (n = 1; 85%)
a (n = 2; 65%)
b (n = 2; 76%)
1
8
8
a (68%)
b (71%)
acetate : hexane, 1 : 3). H NMR (acetone-d ), δ: 7.91 (m,
6
2 H, Ph); 7.61 (m, 3 H, Ph); 7.34 (s, 1 H, NH); 4.86 (m, 2 H,
=CH ); 3.75 (s, 3 H, OMe); 3.10 (s, 3 H, Me); 3.01, 2.70
2
2
(
both d, AB system, 1 H each, CH , JH,H = 14.3 Hz); 1.70 (s,
3 H, Me). F NMR (acetone-d ), δ: 4.51 (s, CF ). Found (%):
2
1
9
but-1-ene, -hex-1-ene, and -oct-1-ene give the corre-
sponding unsaturated derivatives 9—11 in preparative yields
over 24 h, only the E isomers being formed (Scheme 3).
6 3
C, 47.98; H, 4.72; N, 4.08. C14H16F3NO4S. Calculated (%):
C, 47.86; H, 4.56; N, 3.98.
Synthesis of compounds 4—8 (general procedure). 2-Phe-
nylpropene (or the corresponding methylidenecycloalkane)
(14.4 mmol) was added to a solution of imine 2 (14.2 mmol) in
Scheme 3
5
2
mL of CH Cl . The reaction mixture was kept at ∼ 20 °C for
4 h, the solvent was removed in vacuo, and the product was
2 2
F3C
MeO C
R
purified by column chromatography in ethyl acetate : light
petroleum (1 : 3).
Methyl 2-methylsulfonylamino-4-phenyl-2-trifluoromethyl-
N
SO R
2
80 → 100 °C
2
pent-4-enoate (4a). Yield 78%, pale yellow oil, R 0.35 (ethyl
f
2
acetate : light petroleum, 1 : 3). 1H NMR (acetone-d ), δ: 7.39
F C
3
6
CO Me
2
(m, 5 H, Ph); 7.60 (s, 1 H, NH); 5.43 (m, 2 H, =CH ); 3.45,
R
2
2
3
3
.35 (both d, AB system, 1 H each, CH , JH,H = 14.3 Hz);
.29 (s, 3 H, OMe); 2.97 (s, 3 H, Me). 19F NMR (acetone-d ),
2
NHSO Ph
2
6
δ: 4.42 (s, CF ). Found (%): C, 47.66; H, 4.41; N, 4.11.
9
(68%)
3
1
1
0 (87%)
1 (81%)
C14H16F NO S. Calculated (%): C, 47.86; H, 4.56; N, 3.98.
3 4
Methyl 4-phenyl-2-phenylsulfonylamino-2-trifluoromethylpent-
4
-enoate (4b). Yield 80%, m.p. 74—77 °C (from hexane), R 0.30
f
R = CH Br (9), Pr (10), C H (11)
2
5
9
1
(
ethyl acetate : light petroleum, 1 : 3). H NMR (CDCl ), δ: 7.61
3
(
m, 10 H, 2 Ph); 5.82 (s, 1 H, NH); 5.51 (d, 2 H, =CH2,
Thus, our studies of the ene reactions of sulfonyl-
imines 2 with terminal alkenes allow regarding these
imines as the most reactive enophiles, the so-called
2
JH,H = 25.62 Hz); 3.68, 3.37 (both d, AB system, 1 H each,
2
= 13.3 Hz); 3.27 (s, 3 H, OMe). 19F NMR (CDCl ),
CH , J
2
H,H
3
δ: 5.16 (s, CF ). Found (%): C, 55.34; H, 4.50; N, 3.51.
C19H18F NO S. Calculated (%): C, 55.20; H, 4.36; N, 3.39.
3
"
superenophiles". They are as reactive in the imino-ene
3
Methyl 3-(cyclopent-1-enyl)-2-methylsulfonylamino-2-tri-
4
reaction as, and sometimes more reactive than, such
enophiles as hexafluoroacetone and methyl trifluoro-
pyruvate in the keto-ene reaction.11 Hence, we devel-
oped a preparative one-step method for the synthesis of
previously unavailable derivatives of γ,δ-unsaturated
α-amino α-trifluoromethylcarboxylic acids, which are
promising for modification of biologically active peptides.
fluoromethylpropionate (5a). Yield 74%, m.p. 42—45 °C (from
hexane), Rf 0.46 (ethyl acetate : light petroleum, 1 : 3). H NMR
(
3
3
4
1
CDCl ), δ: 5.77 (s, 1 H, NH); 5.63 (s, 1 H, =CH); 3.88 (s,
3
2
H, OMe); 3.31 (d, AB system, 1 H, CH2, JH,H = 14.2 Hz);
.11 (s, 3 H, Me); 2.90 (d, AB system, 1 H, CH ); 2.30 (m,
2
1
9
H, 2 CH ); 1.86 (m, 2 H, CH ). F NMR (CDCl ), δ: 3.95
2
2
3
(s, CF ). Found (%): C, 41.98; H, 4.92; N, 4.28. C11H16F NO S.
3
3
4
Calculated (%): C, 41.90; H, 5.08; N, 4.44.
Methyl 3-(cyclopent-1-enyl)-2-phenylsulfonylamino-2-tri-
Experimental
fluoromethylpropionate (5b). Yield 85%, m.p. 88—90 °C (from
1H and 19F NMR spectra were recorded on a Bruker
WR-SY instrument (200 and 188 MHz, respectively). The
1
hexane), R 0.54 (ethyl acetate : light petroleum, 1 : 3). H NMR
f
(CDCl ), δ: 7.87 (m, 2 H, Ph); 7.51 (m, 3 H, Ph); 5.90 (s, 1 H,
3

Thermal ene reactions
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 6, June, 2001
1043
NH); 5.57 (s, 1 H, =CH); 3.84 (s, 3 H, OMe); 3.42, 2.89
Synthesis of compounds 9—11 (general procedure). A mix-
ture of benzenesulfonylimine 2b (5.8 mmol) and an alkene
(15.5 mmol) was heated in a sealed tube at 80 °C for 24 h (at
100 °C for 9b and 9c). The volatile components were removed in
vacuo, and the product was purified by column chromatography.
Methyl (E)-6-bromo-2-phenylsulfonylamino-2-trifluoro-
2
(
4
both d, AB system, 1 H each, CH , J
= 14.3 Hz); 2.28 (m,
H,H
2
1
9
H, 2 CH ); 1.81 (m, 2 H, CH ). F NMR (CDCl ), δ: 4.04
2 2 3
(
s, CF ). Found (%): C, 51.07; H, 4.70; N, 3.68. C16H18F NO S.
3
3
4
Calculated (%): C, 50.93; H, 4.77; N, 3.71.
Methyl 3-(cyclohex-1-enyl)-2-methylsulfonylamino-2-tri-
fluoromethylpropionate (6a). Yield 65%, m.p. 42—45 °C (from
methylhex-4-enoate (9). Yield 68%, oil, R 0.39 (ethyl acetate :
f
1
light petroleum, 1 : 5). 1H NMR (acetone-d ): 7.93 (m, 2 H,
hexane), R 0.46 (ethyl acetate : light petroleum, 1 : 3). H NMR
f
6
(
3
1
CDCl ), δ: 5.59 (s, 1 H, =CH); 5.37 (s, 1 H, NH); 3.80 (s,
Ph); 7.60 (m, 3 H, Ph); 7.51 (s, 1 H, NH); 5.81 (dt, 2 H,
3
H, OMe); 3.09 (s, 3 H, Me); 3.00, 2.62 (both d, AB system,
CH=CH, J
= 15.1 Hz, 3J = 6.4 Hz); 3.99 (d, 2 H, BrCH2,
trans
H each, CH2, 2JH,H = 14.4 Hz); 1.96 (m, 3 H, CH ); 1.87
3
JH,H = 5.4 Hz); 3.74 (s, 3 H, OMe); 2.93 (m, 2 H, CH ).
19
2
2
1
9
(
m, 1 H, CH ); 1.50 (m, 4 H, CH ). F NMR (CDCl ),
F NMR (acetone-d ), δ: 5.61 (s, CF ). Found (%): C, 39.15;
2
2
3
6 3
δ: 5.66 (s, CF ). Found (%): C, 43.57; H, 5.38; N, 4.38.
H, 3.58; N, 3.42. C14H15BrF NO S. Calculated (%): C, 39.07;
3 4
3
C12H18F NO S. Calculated (%): C, 43.77; H, 5.47; N, 4.25.
H, 3.49; N, 3.25.
Methyl 2-phenylsulfonylamino-(E)-2-trifluoromethyloct-4-
3
4
Methyl 3-(cyclohex-1-enyl)-2-phenylsulfonylamino-2-tri-
fluoromethylpropionate (6b). Yield 76%, m.p. 83—86 °C (from
enoate (10). Yield 87%, m.p. 44—45 °C (from hexane), R 0.29
f
1
1
hexane), R 0.46 (ethyl acetate : light petroleum, 1 : 3). H NMR
(ethyl acetate : light petroleum, 1 : 5). H NMR (acetone-d ):
f
6
(
=
(
4
CDCl ), δ: 7.77 (m, 2 H, Ph); 7.46 (m, 3 H, Ph); 5.69 (s, 1 H,
CH); 5.51 (s, 1 H, NH); 3.75 (s, 3 H, OMe); 3.10, 2.60
7.91 (m, 2 H, Ph); 7.61 (m, 3 H, Ph); 7.41 (s, 1 H, NH); 5.61
3
(dt, 1 H, =CH, Jtrans = 16.1 Hz, 3J = 5.8 Hz); 5.35 (dt, 1 H,
2
=CH, 3J = 5.8 Hz); 3.70 (s, 3 H, OMe); 2.86 (m, 2 H, CH );
both d, AB system, 1 H each, CH , J
= 14.2 Hz); 1.90 (m,
H,H
2
2
1
9
H, 2 CH ); 1.49 (m, 4 H, 2 CH ). F NMR (CDCl ), δ: 5.54
1.90 (m, 2 H, CH ); 1.31 (m, 2 H, CH ); 0.84 (m, 3 H, Me).
2
2
3
2
2
1
9
(s, CF ). Found (%): C, 52.34; H, 5.32; N, 3.68. C17H20F NO S.
F NMR (acetone-d ), δ: 4.63 (s, CF ). Found (%): C, 50.91;
3
3
4
6 3
Calculated (%): C, 52.17; H, 5.12; N, 3.58.
Methyl 3-(6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl)-2-
H, 4.98; N, 3.75. C16H20F NO S. Calculated (%): C, 50.65;
3 4
H, 5.27; N, 3.69.
Methyl 2-phenylsulfonylamino-(E)-2-trifluoromethyldec-4-
methylsulfonylamino-2-trifluoromethylpropionate (7a). Yield
7
9%, m.p. 98—100 °C (from hexane), Rf 0.42 (ethyl ac-
enoate (11). Yield 81%, oil, R 0.43 (ethyl acetate : light petro-
f
1
1
etate : light petroleum, 1 : 3). H NMR (CDCl ), δ: 5.47 (s,
leum, 1 : 6). H NMR (acetone-d ): 7.91 (m, 2 H, Ph); 7.61 (m,
3
6
1
3
H, =CH); 5.30 (s, 1 H, NH); 3.23 (s, 3 H, OMe); 3.06 (s,
H, Me); 2.95, 2.68 (both d, AB system, 1 H each, CH2,
3 H, Ph); 7.40 (s, 1 H, NH); 5.61 (dt, 1 H, =CH, Jtrans = 17.3 Hz,
3J = 6.4 Hz); 5.35 (dt, 1 H, =CH, 3J = 6.4 Hz); 3.72 (s, 3 H,
2
JH,H = 14.4 Hz); 2.31 (m, 1 H, CH ); 2.20 (m, 2 H, CH );
OMe); 2.86 (m, 2 H, CH ); 1.95 (m, 2 H, CH ); 1.31 (m, 6 H,
2 2
2
2
1
9
1
0
.88 (m, 2 H, CH ); 1.20 (s, 3 H, Me); 1.05 (m, 1 H, CH );
3 ½ CH ); 0.87 (m, 3 H, Me). F NMR (acetone-d ), δ: 4.64 (s,
2
2
2
6
1
9
.76 (s, 3 H, Me).
F NMR (CDCl ), δ: 5.66 (s, CF ).
CF ). Found (%): C, 53.18; H, 5.95; N, 3.34. C18H24F NO S.
3
3
3
3
4
Found (%): C, 48.91; H, 5.83; N, 3.77. C15H22F NO S. Cal-
Calculated (%): C, 53.07; H, 5.89; N, 3.44.
3
4
culated (%): C, 48.78; H, 5.96; N, 3.79.
Methyl 3-(6,6-dimethylbicyclo[3.1.1]hept-2-en-2-yl)-2-
phenylsulfonylamino-2-trifluoromethylpropionate (7b). Yield
References
8
4%, m.p. 94—96 °C (from hexane), R 0.36 (ethyl acetate : light
f
1
2
. J. T. Welch, Tetrahedron, 1987, 43, 3123.
. K. Burger, K. Muetze, W. Hollweck, and B. Koksch,
Tetrahedron, 1998, 54, 5915.
. (a) S. N. Osipov, C. Bruneau, M. Picquet, A. F. Kolomiets,
and P. H. Dixneuf, J. Chem. Soc., Chem. Commun., 1998,
1
petroleum, 1 : 5). H NMR (CDCl ), δ: 7.78 (m, 2 H, Ph);
3
7
(
.42 (m, 3 H, Ph); 5.63 (s, 1 H, =CH); 5.41 (s, 1 H, NH); 3.75
s, 3 H, OMe); 3.06, 2.67 (both d, AB system, 1 H each, CH2,
3
2
JH,H = 12.5 Hz); 2.33 (m, 1 H, CH ); 2.17 (m, 2 H, CH );
2
2
2
0
.00 (m, 2 H, CH ); 1.19 (s, 3 H, Me); 1.03 (m, 1 H, CH );
2
2
2
053; (b) D. Semeril, J. Le Notre, C. Bruneau, P. H.
Dixneuf, A. F. Kolomiets, and S. N. Osipov, New J. Chem.,
001, 16.
1
9
.77 (s, 3 H, Me).
F NMR (CDCl ), δ: 5.79 (s, CF ).
3
3
Found (%): C, 55.72; H, 5.63; N, 3.18. C20H24F NO S. Cal-
culated (%): C, 55.68; H, 5.57; N, 3.25.
Methyl 3-(bicyclo[2.2.1]hepta-2,5-dien-2-yl)-2-methyl-
sulfonylamino-2-trifluoromethylpropionate (8a). Yield 68%, oil,
Rf 0.50 (ethyl acetate : light petroleum, 1 : 4). 1H NMR
3
4
2
4
5
. (a) K. Burger, E. Hoess, K. Gaa, N. Sewald, and
C. Schierlinger, Z. Naturforsch., 1991, 46, 361; (b) K. Burger
and N. Sewald, Synthesis, 1990, 115.
. N. Sewald and K. Burger, in Fluorine-Containing Amino
Acids: Synthesis and Properties; Eds. V. P. Kukhar´ and
V. A. Soloshonok, J. Wiley and Sons, Chichester, 1995, 139.
. R. M. Borzilleri and M. Weinreb, Synthesis, 1995, 347.
. D. M. Tschaen, E. Turos, and S. M. Weinreb, J. Org.
Chem., 1984, 49, 5058.
. O. Achmatowicz and M. Pietraszkiewicz, J. Chem. Soc.,
Chem. Commun., 1976, 484.
. S. N. Osipov, N. D. Chkanikov, A. F. Kolomiets, and A. V.
Fokin, Izv. Akad. Nauk SSSR, Ser. Khim., 1986, 1384 [Bull.
Acad. Sci. USSR, Div. Chem. Sci., 1986, 35 1256 (Engl.
Transl.)].
(
(
(
CDCl ), δ: 6.72 (m, 2 H, 2 =CH); 6.52 (s, 1 H, =CH); 5.37
s, 1 H, NH); 3.84 (s, 3 H, OMe); 3.53 (br.s, 1 H, CH); 3.43
d, AB system, 1 H, CH , 2JH,H = 14.5 Hz); 3.39 (br.s, 1 H,
3
2
6
7
CH); 3.09 (s, 3 H, Me); 2.95 (d, AB system, 1 H, CH ); 1.96
2
m, 2 H, CH ). 1 F NMR (CDCl ), δ: 5.10 (s, CF ). Found (%):
9
(
2 3 3
C, 45.89; H, 4.59; N, 4.25. C13H16F NO S. Calculated (%):
C, 46.02; H, 4.72; N, 4.13.
Methyl 3-(bicyclo[2.2.1]hepta-2,5-dien-2-yl)-2-phenylsul-
fonylamino-2-trifluoromethylpropionate (8b). Yield 71%, oil,
Rf 0.38 (ethyl acetate : light petroleum, 1 : 5). 1H NMR
3
4
8
9
(
CDCl ), δ: 7.80 (m, 2 H, Ph); 7.41 (m, 3 H, Ph); 6.68 (m,
3
2
3
3
1
H, 2 =CH); 6.42 (s, 1 H, =CH); 5.67 (s, 1 H, NH); 3.73 (s,
1
1
0. W. J. Drury, III, D. Ferraris, C. Cox, B. Young, and
T. Lectka, J. Am. Chem. Soc., 1998, 120, 11006.
1. A. S. Golubev, A. F. Kolomiets, and A. V. Fokin, Usp.
Khim., 1992, 61, 1422 [Russ. Chem. Rev., 1992, 61, 779
H, OMe); 3.45 (d, AB system, 1 H, CH , 2JH,H = 15.6 Hz);
2
.44 (br.s, 1 H, CH); 3.37 (br.s, 1 H, CH); 2.89 (d, AB system,
H, CH ); 1.93 (m, 1 H, CH ); 1.88 (m, 1 H, CH ).
2
2
2
1
9
F NMR (CDCl ), δ: 5.37 (s, CF ). Found (%): C, 53.90;
3
3
(
Engl. Transl.)].
H, 4.61; N, 3.58. C18H18F NO S. Calculated (%): C, 53.86;
3
4
H, 4.49; N, 3.49.
Received February 13, 2001