Full text of DOI:10.1016/S0040-4020(01)01177-2

TETRAHEDRON
Pergamon
Tetrahedron 58 92002) 983±988
Zinc tetra¯uoroborate catalyzed Mannich-type reaction of
aldimines and silyl enol ethers in aqueous medium
Brindaban C. Ranu,p Sampak Samanta and Sankar K. Guchhait
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India
Received 31 August 2001; revised 26October 2001; accepted 22 November 2001
AbstractÐThe use of zinc tetra¯uoroborate as a catalyst in Mannich-type addition of silyl enol ethers to aldimines in aqueous THF provides
b-amino ketones or b-amino esters in high yields. A one-pot reaction of an aldehyde, amine and silyl enolate also works well. q 2002
Elsevier Science Ltd. All rights reserved.
1. Introduction
2. Results and discussion
The Mannich reaction is one of the most important methods
for the preparation of b-amino carbonyl compounds and has
received wide applications in organic synthesis.1 However,
the classical procedure is associated with serious dis-
advantages involving drastic reaction conditions and long
reaction periods. Thus, the Lewis acid promoted condensa-
tion of silyl enol ethers to imines, ®rst reported by Ojima
et al.2 constitutes an excellent modi®cation. Since then
several methods using a variety of Lewis acids in anhydrous
conditions have been reported.3 However, many of these
methods involve toxic and hazardous Lewis acids including
TiCl4 in chlorinated solvents which is not desirable from an
environmental point of view. Thus, in recent times a number
of procedures using less hazardous Lewis and Bronsted
acids in aqueous media have been developed.4 Being eco-
friendly these methods are of much signi®cance in the ®eld
of synthetic organic chemistry. As part of our program to
study organic reactions in aqueous medium we have intro-
duced a very cheap commercially available reagent, zinc
tetra¯uoroborate in water for the deprotection of TBDMS
ethers5 and we have discovered that this reagent is also very
effective in catalyzing Mannich-type reactions of silyl enol
ethers with aldimines 9Scheme 1).
In a typical experimental procedure, an imine in aqueous
THF was stirred with a silyl enol ether in presence of a
catalytic amount 930 mol%) of an aqueous solution 940%)
of zinc tetra¯uoroborate at room temperature for a few
minutes 9TLC). Extraction with ether and puri®cation by
column chromatography over silica gel furnished the pure
product.
Several aldimines derived from aromatic aldehydes and
aniline underwent clean additions to silyl enol ethers of a
variety of acyclic ketones by this procedure to produce the
corresponding b-amino ketones in high yields. The results
are summarized in Table 1. However, the reaction with silyl
enol ether from an aldehyde 9entry 10) ended up with
relatively lower yield. Aldimines from aliphatic aldehydes
also did not give satisfactory results 9poor yield).
Silyl enol ethers of cyclic ketones 95±8 membered) add
readily to aldimines providing the corresponding b-amino
ketones in very good yields. The diastereoselectivities are
reasonably good, the syn isomers6 being the major in cyclo-
pentanone and cycloheptanone units while the anti isomers6
dominate in six- and eight-membered ketones. The results
Scheme 1.
Keywords: Mannich reaction; b-amino carbonyl compounds; zinc tetra¯uoroborate.
Corresponding author. Tel.: 191-33-473-4971; fax: 191-33-473-2805; e-mail: ocbcr@mahendra.iacs.res.in
p
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020901)01177-2

984
B. C. Ranu et al. / Tetrahedron 58 )2002) 983±988
Table 1. Mannich-type addition of aldimines and silyl enol ethers of acyclic ketones
Entry
R1
R2
R3
R4
Time 9min)
Yield 9%)a
syn/anti6
90:10
1
2
3
4
5
6Ph
7
Ph
Ph
Ph
Ph
Ph
H
H
Me
H
Me
H
H
H
H
Me
Me
Et
Et
Ph
10
20
20
6
10
10
12
80
71
82
98
p-9Me)±C6H4
p-9Cl)±C6H4
Ph
72
95
81
H
Ph±CHvCH9t)
H
H
H
H
8
H
Ph
12
82
9
H
H
Ph
H
12
20
84
48
10
Ph
Me
Me
a
Yields refer to those of pure isolated products fully characterized by spectral data.
Table 2. Mannich-type addition of aldimines and silyl enol ethers of cyclic
ketones
The addition of ketene silyl acetals is also carried out
successfully by this procedure to give the corresponding
b-amino esters 9Scheme 2). The syn addition products are
found to be major isomers in these reactions too.
Alternatively, a one-pot three-component condensation of
aldehydes, amines and silyl enol ethers from acyclic as well
as cyclic ketones was also found to proceed ef®ciently in the
presence of zinc tetra¯uoroborate. Some examples are
presented in Schemes 3 and 4. The yields of products are
reasonably good for a three-component condensation
although lower than two-component one. The diastereo-
selectivities are found to remain more or less same as in
the corresponding two-component reaction.
Entry
R1
n
Time 9min)
Yield 9%)a
syn/anti6
1
2
3
4
5
6Ph
7
Ph
Ph
1
2
2
3
3
8
10
12
5
87
88
8630:70
93
94
30:70
97
87
70:30
20:80
p-9Cl)±C6H4
Ph
p-9Cl)±C6H4
4
p-9Cl)±C6H4
p-9OMe)±C6H4
85:15
80:20
5
10
98
4
4
8
15
15:85
10:90
8
a
Yields refer to pure isolated products fully characterized by spectral data.
3. Conclusion
are presented in Table 2 Surprisingly, additions to silyl enol
ethers of cyclic ketones are not adequately addressed in
earlier methods,4 except a recent one using indium9III)
chloride which reports a few reactions with silyl enol
ether of cyclopentanone in low yields 911±68%).4d
The present procedure using zinc tetra¯uoroborate provides
an ef®cient Mannich-type addition of aldehydes, amine and
silyl enol ethers for the synthesis of b-amino carbonyl
compounds which are useful intermediates for the synthesis
of various biologically active units. The signi®cant features
Scheme 2.

B. C. Ranu et al. / Tetrahedron 58 )2002) 983±988
985
Scheme 3.
Scheme 4.
of this procedure are: 9a) operational simplicity and fast
reaction 910±40 min); 9b) use of a very cheap commercially
available reagent as catalyst; 9c) general applicability to
silyl enol ethers of both acyclic and cyclic ketones,
aldehydes and esters; 9d) high yields of products; 9e) reason-
ably good diastereoselectivities; and 9f) reaction in aqueous
medium avoiding chlorinated solvents.
4.2. General procedure for the synthesis of b-amino
carbonyl compounds
4.2.1. General procedure for the addition of imine and
silyl enol ethers 'entry 4, Table 1). A mixture of benzyl-
ideneaniline 9181 mg, 1 mmol) and 1-phenyl-1-trimethyl-
silyloxy ethene 9192 mg, 1 mmol) in aqueous 91:1) THF
92 mL) was stirred with an aqueous 940%) solution of zinc
tetra¯uoroborate 90.13 mL, 30 mol%, Aldrich) at room
temperature 928±308C) for 6min 9TLC). A solid separated
out in the reaction media. The reaction mixture was then
extracted with ether 93£15 mL) and the ether extract was
washed with brine and dried over Na2SO4. Evaporation of
solvent left the crude product which was puri®ed by column
chromatography over silica gel 9eluted with petroleum
ether/ether 99:1)) to provide a pure product, 3-amino-
4. Experimental
4.1. General
Melting points were determined on a glass disk with an
1
electrical bath and are uncorrected. H NMR 9300 MHz)
and 13C NMR 975 MHz) spectra were run in CDCl3 solu-
tions. IR spectra were taken as KBr plates. Elemental
analyses were done by a Perkin Elmer autoanalyzer.
Column chromatography was performed on silica gel
960±120 mesh, SRL, India) and alumina 9neutral, SRL).
The imines were prepared by keeping a mixture of aldehyde
and amine at 08C for half-an-hour followed by recrystalliza-
tion from ethanol. Silyl enol ethers were prepared by
standard procedures.7 Chlorotrimethylsilane and the alde-
hydes, ketones and amines used are all commercially
available and were distilled before use.
phenyl-1,3-diphenylpropan-1-one
compound 9295 mg, 98%), mp 168±1708C. The spectral
as
a
crystalline
9IR, H and 13C NMR) data of our compound is found to
1
be identical with those reported.4d
This procedure is followed for the addition of all other
imines and silyl enol ethers listed in Tables 1 and 2 and
Scheme 2).
4.2.2. General procedure for the one-pot addition of
aldehyde, amine and silyl enol ethers. To a stirred

986
B. C. Ranu et al. / Tetrahedron 58 )2002) 983±988
910 min) mixture of aniline 9116mg, 1.2 mmol) and benzal-
dehyde 9106mg, 1 mmol) in aqueous 91:1) THF 91 mL) was
added 1-trimethylsilyloxycyclohexene 9170 mg, 1 mmol)
and aqueous solution 940%) of zinc tetra¯uoroborate
90.13 mL, 30 mol%) and the reaction mixture was stirred
for 25 min 9TLC) at room temperature. Extraction with
ether followed by work-up and puri®cation as described in
Section 4.2.1 provided the pure product, 2-[aminophenyl-
9phenyl)methyl]cyclohexan-1-one, as a crystalline 9cubes)
compound 9232 mg, 80%), mp 123±258C; IR 3328, 1701,
11.9, 10.0. Anal. calcd for C18H21NO: C, 80.89; H, 7.86;
N, 5.24. Found: C, 80.56; H, 7.76; N, 5.19.
4.2.6. 3-Aminophenyl-2,2-dimethyl-1-'40-methylphenyl)-
3-phenylpropan-1-one 'entry 5, Table 1). Colorless
1
needles, mp 136±1388C; IR 3419, 1681, 1600 cm21; H
NMR d 7.19±7.28 9m, 7H), 7.09 9d, Jˆ7.8 Hz, 2H), 7.00
9d, Jˆ7.5 Hz, 1H), 6.97 9d, Jˆ7.5 Hz, 1H), 6.54±6.58 9m,
1H), 6.40 9d, Jˆ7.5 Hz, 2H), 4.769s, 1H), 4.65 9s, 1H), 2.33
9s, 3H), 1.33 9s, 3H), 1.20 9s, 3H); 13C NMR d 209.9, 146.7,
141.0, 139.2, 137.2, 129.4 92C), 129.1 92C), 129.0 92C),
128.5 92C), 127.9, 127.5 92C), 117.9, 113.9 92C), 63.8,
52.4, 25.9, 21.8. Anal. calcd for C24H25NO: C, 83.96; H,
7.28; N, 4.08. Found: C, 83.57; H, 6.98; N, 3.97.
1
1600 cm21; H NMR 9syn/antiˆ20:80) d 7.18±7.37 9m,
5H), 7.02±7.07 9m, 2H), 6.51±6.63 9m, 3H), 4.79 9d,
Jˆ4.5 Hz, 0.2H), 4.61 9d, Jˆ6.3 Hz, 0.8H), 2.69±2.74 9m,
1H), 2.27±2.41 9m, 2H), 1.77±1.89 9m, 4H), 1.59±1.71 9m,
2H); 13C NMR 9major isomer) d 213.3, 147.7, 142.1, 129.5
92C), 128.8 92C), 127.7, 127.4 92C), 117.9, 114.0 92C), 58.3,
57.9, 42.2, 31.7, 28.3, 24.0; 9minor isomer) d 212.3, 147.9,
142.0, 129.4 92C), 128.9 92C), 127.9, 127.692C), 118.1,
114.5 92C), 57.6, 57.0, 42.8, 29.1, 27.4, 25.3. Anal. calcd
for C19H21NO: C, 81.72; H, 7.52; N, 5.02. Found: C, 81.46;
H, 7.49; N, 4.98.
4.2.7. 3-Aminophenyl-1-'40-chlorophenyl)-3-phenylpro-
pan-1-one 'entry 6, Table 1). Colorless round crystal, mp
116±1188C; IR 3377, 1672, 1602 cm21; 1H NMR d 7.78 9d,
Jˆ8.4 Hz, 2H), 7.18±7.49 9m, 7H), 7.04±7.09 9m, 2H),
6.62±6.67 9m, 1H), 6.54 9d, Jˆ8.1 Hz, 2H), 4.98 9t,
Jˆ6.3 Hz, 1H), 4.49 9br s, 1H), 3.32±3.46 9m, 2H); 13C
NMR d 197.5, 147.3, 143.2, 140.3, 135.4, 130.0 92C),
129.692C), 129.4 92C), 129.3 92C), 127.9, 12.68 92C),
118.3, 114.3 92C), 55.1, 46.6. Anal. calcd for
C21H18NOCl: C, 75.12; H, 5.36; N, 4.17. Found: C, 74.77;
H, 5.12; N, 4.01.
This procedure is followed for all one-pot condensation of
aldehydes, amines and silyl enol ethers listed in Schemes 3
and 4.
The known compounds 9entries 4 and 7 in Table 1 and entry
1 in Table 2) have been identi®ed by comparison of spectral
data and mp with those reported.4b,d The unknown
compounds have been characterized by their spectral 9IR,
1H and 13C NMR) data and elemental analysis. These data
are presented below in order of their entries.
4.2.8. 3-Aminophenyl-3-'20-furyl)-1-phenylpropan-1-one
'entry 8, Table 1). Brownish needles, mp 101±1038C; IR
3369, 1674 cm21; 1H NMR d 7.90±7.92 9m, 2H), 7.40±7.57
9m, 3H), 7.12±7.30 9m, 3H), 6.66±6.74 9m, 3H), 6.19±6.25
9m, 2H), 5.22 9t, Jˆ6.0 Hz, 1H), 4.38 9br s, 1H), 3.55 9d,
Jˆ6.1 Hz, 2H); 13C NMR d 198.3, 155.3, 147.0, 142.0, 137.1,
133.8, 129.7 92C), 129.0 92C), 128.5 92C), 118.7, 114.4 92C),
110.8, 106.9, 49.0, 42.8. Anal. calcd for C19H17NO2: C, 78.35;
H, 5.84; N, 4.81. Found: C, 77.98; H, 5.89; N, 4.68.
4.2.3. 4-Aminophenyl-4-phenylbutan-2-one 'entry 1,
Table 1). Yield: 80%, colorless needles, mp 79±818C; IR
1
3369, 1707, 1604 cm21; H NMR d 7.22±7.37 9m, 5H),
7.06±7.11 9m, 2H), 6.52±6.68 9m, 3H), 4.84 9t, Jˆ6.5 Hz,
1H), 4.34 9br s, 1H), 2.91 9d, Jˆ6.5 Hz, 2H), 2.09 9s, 3H);
13C NMR d 206.9, 146.7, 142.5, 129.0 92C), 128.7 92C),
127.2, 126.2 92C), 117.7, 113.7 92C), 54.3, 51.1, 30.6. Anal.
calcd for C16H17NO: C, 80.33; H, 7.11; N, 5.85. Found: C,
79.98; H, 7.21; N, 5.61.
4.2.9.
3-Aminophenyl-1-phenyl-3-'20-thiophenyl)pro-
pan-1-one 'entry 9, Table 1). Brownish needles, mp
115±1178C; IR 3375, 1672, 1600 cm21; H NMR d 7.94±
1
7.97 9m, 2H), 7.45±7.59 9m, 3H), 7.16±7.19 9m, 3H), 7.04±
7.05 9m, 1H), 6.93±6.96 9m, 1H), 6.71±6.77 9m, 3H); 5.43
9t, Jˆ6.1 Hz, 1H), 3.61 9d, Jˆ6.1 Hz, 2H) 13C NMR d
198.3, 148.1, 147.1, 137.2, 133.9, 129.7 92C), 129.1 92C),
128.692C), 127.4, 124.6, 124.4, 118.8, 114.5 92C), 51.1,
46.4. Anal. calcd for C19H17NOS: C, 74.26; H, 5.54; N,
4.56. Found: C, 73.97; H, 5.50; N, 4.32.
4.2.4. 5-Aminophenyl-5-phenylpentan-3-one 'entry 2,
Table 1). Waxy solid; IR 3398, 1706, 1602 cm21 1H
;
NMR d 7.20±7.34 9m, 5H), 7.04±7.09 9m, 2H), 6.50±
6.66 9m, 3H), 4.81 9t, Jˆ6.4 Hz, 1H), 2.87 9d, Jˆ6.4 Hz,
2H), 2.27±2.34 9m, 2H), 0.95 9t, Jˆ7.2 Hz, 3H); 13C NMR d
210.2, 147.2, 143.0, 129.5 92C), 129.0 92C), 127.7, 126.7
92C), 118.2, 114.1 92C), 59.3, 50.3, 37.3, 7.9. Anal. calcd for
C17H19NO: C, 80.63; H, 7.50; N, 5.53. Found: C, 80.41; H,
7.44; N, 5.29.
4.2.10. 3-Aminophenyl-2,2-dimethyl-3-phenylpropan-1-
al 'entry 10, Table 1). Gummy mass; IR 3382, 1705,
1602 cm21; H NMR d 9.95 9s, 1H), 7.18±7.369m, 7H),
1
6.45±6.68 9m, 3H), 4.63 9s, 1H), 1.23 9s, 3H), 1.18 9s, 3H);
13C NMR d 192.9, 147.5, 141.2, 129.7 92C), 129.3 92C),
127.3, 127.1 92C), 117.7, 113.8 92C), 61.6, 42.3, 23.3, 21.9.
Anal. calcd for C17H19NO: C, 80.63; H, 7.50; N, 5.53.
Found: C, 80.42; H, 7.19; N, 5.21.
4.2.5. 5-Aminophenyl-4-methyl-5-phenylpentan-3-one
'entry 3, Table 1). Colorless needles 9syn/antiˆ90:10),
mp 114±1168C; IR 3381, 1701, 1602 cm21 1H NMR
;
9syn1anti) d 7.19±7.30 9m, 5H), 7.01±7.06 9m, 2H), 6.62
9t, Jˆ7.3 Hz, 1H), 6.44±6.49 9m, 2H), 4.64 9d, Jˆ5.6,
0.9 H), 4.52 9d, Jˆ6.8 Hz, 0.1H), 2.96±3.03 9m, 1H),
2.25±2.38 9m, 2H), 1.18 9d, Jˆ7.1 Hz, 0.3H), 1.09 9d,
Jˆ7.0 Hz, 2.7H), 0.85±0.97 9m, 3H); 13C NMR 9major
isomer) d 213.1, 147.3, 141.5, 129.4 92C), 128.9 92C),
127.7, 127.2 92C), 118.1, 114.0 92C), 59.6, 52.62, 35.9,
4.2.11. 2-[Aminophenyl'40-chlorophenyl)methyl]cyclo-
hexan-1-one 'entry 3, Table 2). Gummy solid 9syn/
antiˆ30:70); IR 3388, 1705, 1600 cm21
;
1H NMR
9syn1anti) d 7.19±7.33 9m, 4H), 7.01±7.07 9m, 2H),
6.48±6.49 9m, 3H), 4.72 9d, Jˆ4.5 Hz, 0.3 H), 4.59 9d,
Jˆ6.3 Hz, 0.7H), 2.47±2.74 9m, 1H), 2.25±2.38 9m, 2H),

B. C. Ranu et al. / Tetrahedron 58 )2002) 983±988
987
1.57±1.84 9m, 6H); 13C NMR 9major isomer) d 212.8,
147.7, 140.9, 133.1, 129.692C), 129.3 92C), 129.0 92C),
118.1, 114.0 92C), 57.8, 57.7, 42.5, 31.9, 28.3, 24.4; 13C
NMR 9minor isomer) d 211.6, 147.7, 140.7, 133.0, 129.5
92C), 129.3 92C), 129.2 92C), 118.3, 114.5 92C), 57.2, 56.8,
42.8, 29.4, 27.5, 24.2. Anal. calcd for C19H20NOCl: C,
72.74; H, 6.38; N, 4.46. Found: C, 72.63; H, 6.21; N, 4.19.
133.2, 129.5 92C), 129.1 92C), 128.5 92C), 117.7, 113.6
92C), 60.3, 55.5, 44.9, 33.0, 28.3, 25.4, 25.3, 24.2. Anal.
calcd for C21H24NOCl: C, 73.80; H, 7.02; N, 4.10. Found:
C, 73.63; H, 6.73; N, 3.87.
4.2.16. 2-[Aminophenyl'40-methoxyphenyl)methyl]cyclo-
octan-1-one 'entry 8, Table 2). Gummy solid 9syn/
antiˆ10:90); IR 3391, 1687, 1602 cm21
;
1H NMR
9syn1anti) d 6.89±7.39 9m, 5H), 6.50±6.81 9m, 4H), 4.49
9d, Jˆ7.2 Hz, 0.9H), 4.45 9d, Jˆ6.7 Hz, 0.1H), 3.81 9s,
0.3H), 3.74 9s, 2.7H), 2.96±3.15 9m, 1H), 1.25±2.07 9m,
12H); 13C NMR 9major isomer) d 219.6, 159.1, 147.5,
133.5, 129.5 92C), 128.5 92C), 117.7, 113.9 92C), 60.3,
57.5, 55.6, 44.5, 30.6, 28.0, 26.9, 26.0, 25.4. Anal. calcd
for C22H27O2N: C, 78.34; H, 8.01; N, 4.15. Found: C,
78.12; H, 7.97; N, 3.77.
4.2.12. 2-[Aminophenyl'phenyl)methyl]cycloheptan-1-
one 'entry 4, Table 2). Colorless cubes 9syn/antiˆ85:15),
mp 124±1268C; IR 3390, 1689, 1602 cm21 1H NMR
;
9syn1anti) d 7.16±7.33 9m, 5H), 7.01±7.06 9m, 2H), 6.59
9t, Jˆ7.2 Hz, 1H), 6.50 9d, Jˆ7.8 Hz, 2H), 4.91 9br s, 1H),
4.61 9d, Jˆ4.8 Hz, 0.85H), 4.48 9d, Jˆ7.5 Hz, 0.15H),
2.80±2.87 9m, 1H), 2.18±2.24 9m, 2H), 1.15±2.03 9m,
8H); 13C NMR 9major isomer) d 216.8, 147.2, 140.9,
129.5 92C), 128.9 92C), 127.7 92C), 127.6, 117.7, 113.9
92C), 60.6, 58.8, 44.6, 30.2, 28.9, 27.9, 25.6; 13C NMR
9minor isomer) d 215.5, 147.5, 142.1, 128.8 92C), 128.5
92C), 127.8 92C), 127.7, 117.8, 113.8 92C), 60.7, 58.9,
43.1, 29.7, 29.5, 28.3, 25.4. Anal. calcd for C20H23NO: C,
81.91; H, 7.85; N, 4.78. Found: C, 81.63; H, 7.76; N, 4.56.
4.2.17. Ethyl 3-aminophenyl-2-benzyl-3-phenylpropano-
ate 'entry a, Scheme 2). Colorless powder 9syn/
antiˆ90:10), mp 106±1088C; IR 3400, 1697, 1604 cm21
;
1H NMR 9syn1anti) d 7.05±7.37 9m, 12H), 6.50±6.67
9m, 3H), 4.59±4.71 9m, 1H), 3.86±4.15 9m, 2H), 2.84±
3.15 9m, 3H), 1.14 9t, Jˆ7.1 Hz, 0.3H), 0.969t, Jˆ7.2 Hz,
0.7H); 13C NMR 9major isomer) d 173.4, 147.4, 140.9,
139.6, 129.5 92C), 129.4 92C), 128.8 92C), 128.7 92C),
127.9, 127.7 92C), 127.0, 118.2, 114.1 92C), 61.1, 60.1,
55.0, 34.2, 14.3. Anal. calcd for C24H25O2N: C, 80.22; H,
6.96; N, 3.90. Found: C, 80.56; H, 6.49; N, 3.68.
4.2.13. 2-[Aminophenyl'40-chlorophenyl)methyl]cyclo-
heptan-1-one 'entry 5, Table 2). Colorless cylindrical
crystal 9syn/antiˆ80:20), mp 143±1458C; IR 3388, 1689,
1
1602 cm21; H NMR 9syn1anti) d 7.17±7.25 9m, 4H),
7.069d, Jˆ8.4 Hz, 1H), 7.04 9d, Jˆ8.4 Hz, 1H), 6.62 9t,
Jˆ7.3 Hz, 1H), 6.47 9d, Jˆ7.5 Hz, 2H), 4.58 9d,
Jˆ4.8 Hz, 0.8H), 4.47 9d, Jˆ7.2 Hz, 0.2H), 2.79±2.91 9m,
1H), 1.18±2.28 9m, 10H); 13C NMR 9major isomer) d 216.3,
146.9, 139.7, 133.4, 129.5 92C), 129.1 92C), 128.9 92C),
118.0, 113.9 92C), 59.9, 58.6, 44.6, 30.1, 28.9, 27.9, 25.4;
13C NMR 9minor isomer) d 215.1, 147.2, 141.3, 129.5 92C),
129.2 92C), 129.1 92C), 118.0, 113.8 92C), 60.1, 58.5, 43.3,
29.6, 29.5, 28.4, 25.1. Anal. calcd for C20H22NOCl: C,
73.29; H, 6.72; N, 4.27. Found: C, 73.01; H, 6.47; N, 4.13.
4.2.18. Ethyl 3-aminophenyl-2,2-dimethyl-3-phenylpro-
panoate 'entry b, Scheme 2). Waxy solid; IR 3398,
1
1712, 1602 cm21; H NMR d 7.20±7.30 9m, 5H), 7.00±
7.05 9m, 2H), 6.47±6.60 9m, 3H), 4.80 9d, Jˆ7.0 Hz, 1H),
4.49 9d, Jˆ7.4 Hz, 1H), 4.07±4.169m, 2H), 1.269s, 3H),
1.169t, Jˆ7.1 Hz, 3H), 1.14 9s, 3H); 13C NMR d 176.9,
147.4, 139.7, 129.4 92C), 128.9 92C), 128.4 92C), 127.8,
117.6, 113.7 92C), 64.7, 61.3, 47.3, 25.0, 20.1, 14.5. Anal.
calcd for C19H23NO2: C, 76.76; H, 7.74; N, 4.71. Found: C,
76.62; H, 7.82; N, 4.43.
4.2.14. 2-[Aminophenyl'phenyl)methyl]cyclooctan-1-one
'entry 6, Table 2). Colorless needles 9syn/antiˆ30:70), mp
138±1408C; IR 3388, 1693, 1602 cm21
;
1H NMR
4.2.19. Ethyl 3-aminophenyl-2-ethyl-3-phenylpropano-
ate 'entry c, Scheme 2). Colorless powder 9syn/
9syn1anti) d 7.13±7.25 9m, 5H), 7.00±7.069m, 2H),
6.57±6.62 9m, 1H), 6.49±6.53 9m, 2H), 4.78 9br s, 1H),
4.54 9d, Jˆ7.2 Hz, 0.7H), 4.50 9d, Jˆ6.6 Hz, 0.3H), 2.98±
3.12 9m, 1H), 1.19±2.03 9m, 12H); 13C NMR 9major isomer)
d 219.5, 147.6, 141.7, 129.5 92C), 129.0 92C), 127.6 92C),
127.2, 117.8, 113.9 92C), 60.8, 57.3, 44.0, 30.7, 28.1, 26.8,
25.4, 25.3; 13C NMR 9minor isomer) d 220.6, 147.5, 142.3,
129.5 92C), 128.9 92C), 127.7 92C), 127.5, 117.5, 113.7
92C), 60.9, 55.8, 44.7, 32.8, 28.3, 25.8, 25.6, 24.4. Anal.
calcd for C21H25NO: C, 82.08; H, 8.14; N, 4.56. Found: C,
81.91; H, 7.87; N, 4.43.
antiˆ84:16), mp 113±1158C; IR 3390, 1708, 1602 cm21
;
1H NMR 9syn1anti) d 7.02±7.33 9m, 7H), 6.48±6.65 9m,
3H), 4.61 9d, Jˆ6.0 Hz, 0.84H), 4.54 9d, Jˆ6.8 Hz, 0.16H),
4.49 9br s, 1H), 3.92±4.12 9m, 2H), 2.66±2.74 9m, 1H),
1.56±1.85 9m, 2H), 1.07±1.12 9m, 3H), 0.86±0.92 9m,
3H); 13C NMR 9major isomer) d 174.0, 147.3, 129.5 92C),
128.8 92C), 127.7, 127.4 92C), 117.9, 113.9 92C), 60.9, 59.9,
54.9, 21.2, 14.5, 12.7. Anal. calcd for C19H23NO2: C, 76.76;
H, 7.74; N, 4.71. Found: C, 76.41; H, 7.52; N, 4.46.
Acknowledgements
4.2.15. 2-[Aminophenyl'40-chlorophenyl)methyl]cyclo-
octan-1-one 'entry 7, Table 2). Colorless needles 9syn/
We are pleased to acknowledge ®nancial support from
CSIR, New Delhi. S. S. is also thankful to CSIR for his
fellowship.
antiˆ15:85), mp 176±1788C; IR 3400, 1687, 1602 cm21
;
1H NMR 9syn1anti) d 7.19±7.269m, 4H), 7.04±7.09 9m,
2H), 6.61±6.66 9m, 1H), 6.46±6.50 9m, 2H), 4.51 9d,
Jˆ7.2 Hz, 0.85H), 4.47 9d, Jˆ6.3 Hz, 0.15H), 2.95±3.18
9m, 1H), 1.22±2.04 9m, 12H); 13C NMR 9major isomer) d
219.1, 147.1, 140.2, 133.4, 129.2 92C), 129.1 92C), 128.9
92C), 118.1, 113.9 92C), 60.3, 57.0, 44.1, 30.6, 28.0, 26.6,
25.6, 25.5; 13C NMR 9minor isomer) d 220.5, 147.2, 140.8,
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