Enamides via long-distance migration of double bonds

Article abstract of DOI:10.1002/hlca.200390074

A new method for preparation of enamides (N-(alken-1-yl) amides) by means of the 'long-distance' migration of the double bond in unsaturated amides in the presence of [Fe(CO)₅] is described. The method is shown to be particularly useful for the

Full text of DOI:10.1002/hlca.200390074

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Helvetica Chimica Acta Vol. 86 (2003)
Enamides via Long-Distance Migration of Double Bonds
by Sergey A. Sergeyev and Manfred Hesse*
Organisch-chemisches Institut der Universit‰t Z¸rich, Winterthurerstrasse 190, CH-8057 Z¸rich
(phone: 41-1-6354281; fax: 41-1-6356812; e-mail: mtbohley@oci.unizh.ch)
A new method for preparation of enamides (N-(alken-1-yl) amides) by means of the −long-distance×
migration of the double bond in unsaturated amides in the presence of [Fe(CO)5] is described. The method is
shown to be particularly useful for the isomerization of N-(but-3-enyl)amides, while, in the case of N-(pent-4-
enyl) and N-(hex-5-enyl) amides the mixture of products was formed and the yield of the enamide was relatively
low.
Introduction. Enamides (N-(alken-1-yl) amides) are interesting substrates for
various synthetic transformations [1]. Several methods have been employed for the
preparation of simple enamides, but they are often structurally limited or suffer from
low yields [2]. Discovery of natural enamides, which possess a wide spectrum of
biological activity [3], stimulated research in the enamide synthesis in recent years [4].
Among other methods, isomerization of N-allyl amides to enamides is particularly
attractive since N-allyl amides are readily available [5]. Stille and Becker [6] reported
isomerization of several simple N-allyl amides to (Z)/(E)-enamide mixtures in
moderate-to-high yields in the presence of hydridorhodium or -ruthenium complexes.
Recently, we have found that various enamides can be smoothly prepared from the N-
allyl amides in the presence of [Fe(CO)5] [7]. The main advantage of the method is the
availability of both starting materials and the catalyst. The procedure is compatible
with various functional groups, and the yields are generally high. Later, we have
successfully applied this procedure to the synthesis of macrocyclic enamide alkaloid
neoperiphylline [8]. We are interested in the extension of this method to other
unsaturated amides. In the present paper, we report successful preparation of enamides
by the −long-distance× migration of a CˆC bond and discuss the limitations of this
method.
Results and Discussion. The unsaturated amides 4a 4c, containing two to four
CH2 units between the amido group and the CˆC bond, were prepared similarly to the
method published recently [7] starting from commercially available bromides 1a 1c
(Scheme 1). Alkylation of (Boc)2NH [9] with 1a 1c in the presence of Cs2CO3 as
phase-transfer catalyst afforded the N,N-bis(Boc) derivatives 2a 2c, which were
smoothly and quantitatively hydrolyzed with CF3COOH (TFA) to the corresponding
amines 3a 3c. Acylation of the latter with 3-phenylpropanoyl chloride in the presence
of Et3N led to the unsaturated amides 4a 4c. (Z)-N-(Hex-4-enyl)-3-phenylpropana-
mide (7) was prepared similarly from commercially available (Z)-hex-3-en-1-ol (5),
which was first converted to the methanesulfonate 6 according to a published

Helvetica Chimica Acta Vol. 86 (2003)
751
procedure [10]. The unsaturated amine 8 with an additional side chain was prepared by
alkylation of propanenitrile with allyl bromide, followed by reduction with LiAlH4 as
described by Tamaru et al. [11]. Subsequent acylation with 3-phenylpropanoyl chloride
gave amide 9 (Scheme 1).
Scheme 1
O
c)
X
Ph
N
H
n
n
4a–c
1a–c X = Br
a n = 1
b n = 2
c n = 3
a)
b)
2a–c X = NBoc2
3a–c X = NH2
O
a), b), c)
X
Ph
N
H
5 X = OH
7
d)
6 X = OMs
O
H2N
e), f)
c)
N
Ph
N
H
Me
Me
8
9
a) (Boc)2NH, Cs2CO3, DMF, 708. b) TFA, CH2Cl2, r.t. c) PhCH2CH2COCl, Et3N, CH2Cl2, 08. d) MsCl, Et3N,
CH2Cl2, À108. e) 1. LDA, THF, À808; 2. CH2ˆCHCH2Br, À808. f) LiAlH4, Et2O, reflux.
The isomerization of the unsaturated amides 4a 4c, 7, and 9 was performed in the
presence of 1 equiv. of [Fe(CO)5] at 1208 without solvent (cf. [7]). In all cases, both
(E)- and (Z)-isomers of enamides (Scheme 2), which were very difficult to separate by
column chromatography, were obtained. Therefore, the (E)/(Z) ratio was determined
1
from the intensities of the signals of CHˆCHN in H-NMR spectra of the mixture of
isomers. The configuration of the CˆC bond in 10a 10c was assigned on the basis of
the coupling constants (typically ca. 14 Hz for (E)- and ca. 9 Hz for (Z)-enamides; cf.
[7]). For the enamide 11, the (E)/(Z) ratio was determined from the integral intensities
of the signals of MeCˆCH (see Exper. Part).
For the N-but-3-enyl amide 4a, we observed complete conversion of the starting
material to the enamide 10a, which was obtained in almost the same yield as by the
isomerization of N-(but-2-enyl)-3-phenylpropanamide [7][12]. Unfortunately, in the
case of N-pent-4-enyl- or N-hex-5-enyl amides (4b and 4c, resp.) the yields of the
enamides were relatively low, and a considerable amount of side-product resulting from
the −incomplete× CˆC bond shift, was isolated (Table). All attempts to increase the
yield of the enamides with higher temperatures or prolonged reaction times remained
unsuccessful and resulted even in lower yields of the enamides because of
decomposition. However, the enamides can be easily separated from the other
products by column chromatography. Moreover, when N-(pent-2-enyl)-3-phenylpro-
panamide (12), the side product from the isomerization of 4b, was treated with

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Helvetica Chimica Acta Vol. 86 (2003)
Scheme 2
O
O
a)
Ph
N
H
Ph
N
H
n
n
a n = 1
b n = 2
c n = 3
4a–c
10a–c
O
a)
10c
Ph
N
H
7
O
O
a)
Ph
N
H
Ph
N
H
Me
Me
9
11
a) Fe(CO)5, 1208, without solvent.
Table. Isomerization of the Amides 4a 4c, 7, 9 in the Presence of [Fe(CO)5]
Starting amide
Enamide (yield [%])
(E)/(Z) Ratio
Side products (yield [%])
4a
4b
4c
7
10a (56)
10b (32)
10c (23)
10c (23)
11 (31)
75 : 25
70 : 30
71 : 29
66 : 34
62 : 38
Not detected
12 (55)
13, 14 (49)a)
a
13, 14 (60)
)
9
15, 16 (55) a)
a) Total yield of all isolated side products.
[Fe(CO)5] under the same conditions, an additional amount of the enamide 10b (33%
with respect to 12) was isolated, and the total yield of 10b from this two-run experiment
was increased to 48% based on starting 4b.
From (Z)-N-(hex-4-enyl)-3-phenylpropanamide (7), the enamide 10c was obtained
in the same yield as its isomer 4c with the terminal CˆC bond. Amide 9 with a
O
O
Ph
N
H
Ph
N
H
12
13
Me
15
O
Ph
Ph
N
H
O
Ph
N
H
O
Me
16
N
H
14

Helvetica Chimica Acta Vol. 86 (2003)
753
branched N-substituent also afforded enamide 11 in 31% yield, together with the side
products 15 and 16. Interestingly, only in this case were we able to detect remarkable
amounts of amide 15 with allylic position of the CˆC bond. It is consistent with the
observation that additional substituents in the allylic moiety dramatically decreased the
rate of isomerization of N-allyl amides to enamides [7][12].
We thank the Swiss National Science Foundation for financial support.
Experimental Part
General. All chemicals and solvents were obtained from commercial sources (Fluka, Aldrich, and Merck)
and used without further purification unless stated otherwise. Technical-grade solvents were distilled before use.
[(Z)-Hex-4-enyl]methanesulfonate (6) [10] and 2-methylpent-4-ene-1-amine (8) [11] were prepared according to
published procedures. Column chromatography (CC): SiO2, Merck 60 (40 63 mm). TLC: precoated SiO2
plates, Merck 60 F254; detection by UVat 254 nm or by spraying with KMnO4 soln. M.p.: Mettler FP-5. 1H-NMR:
Bruker ARX-300 (300 MHz); chemical shifts d in ppm relative to Me4Si as internal standard; J values in Hz.
13C-NMR: Bruker ARX-300 (75MHz); chemical shifts d in ppm relative to Me4Si as internal standard; signals
multiplicity determined from DEPT experiments. CI-MS (NH3 as reactant gas): Finnigan MAT 90, m/z and
relative intensities (% of base peak) are given.
General Procedure 1 (GP 1) for the Preparation of Unsaturated Amides. A mixture of bromide 1 (15mmol),
(Boc)2NH (2.17 g, 10 mmol), Cs2CO3 (3.26 g, 10 mmol), and DMF (10 ml) was stirred for 12 h at 708, then the
volatile materials were removed in vacuo. The residue was partitioned between CH2Cl2 (50 ml) and H2O
(50 ml), the org. phase was separated and washed with H2O (2 Â 50 ml), dried (MgSO4), and concentrated to
afford crude bis(Boc) derivative 2, which was dissolved in CH2Cl2 (20 ml) and treated with CF3COOH (TFA;
3 ml, ca. 40 mmol) in one portion. After 4 h stirring at r.t., the mixture was concentrated, and the residue was
dried in vacuo to give crude amine 3 as TFA salt. It was dissolved in a mixture of CH2Cl2 (30 ml) and Et3N
(4.15ml, 30 mmol), and treated dropwise at 0 8 with 3-phenylpropanoyl chloride (1.33 ml, 9 mmol). The mixture
was stirred for 1 h at 08, then allowed to reach r.t., washed with H2O (25ml), 10% aq. citric acid (25ml), again
H2O (2 Â 25ml), and dried (MgSO 4). Evaporation of the solvent in vacuo and CC of the residue afforded 4.
General Procedure 2 (GP 2) for the Isomerization of Unsaturated Amides. A mixture of unsaturated amide
(2 mmol) and [Fe(CO)5] (0.2 ml, 1 mmol) was stirred under Ar for 16 h at 1208. The mixture was allowed to
reach r.t., then the catalyst was removed in vacuo and collected in a trap cooled by liquid N2. Content of the trap
was treated with 5% soln. of FeCl3 in EtOH to destroy toxic [Fe(CO)5]. The residue in the reaction flask was
dissolved in CH2Cl2/hexane 1:1 and filtered through Celite. The solvent was evaporated in vacuo, and the
residue was purified by CC.
N-(But-3-enyl)-3-phenylpropanamide (4a). According to GP 1, 4-bromobut-1-ene (1a) afforded, after CC
(CH2Cl2/AcOEt 4 :1), 4a (1.58 g, 86%). Colorless oil. Rf (CH2Cl2/AcOEt 10 :1) 0.38. 1H-NMR (CDCl3): 2.18 (q-
like m, CH2CH); 2.45( t, J ˆ 7.7, CH2CO); 2.95( t, J ˆ 7.7, PhCH2); 3.24 3.32 (m, CH2N); 4.97 5.05 (m,
CHˆCH2); 5.44 (br. s, NH); 5.68 (ddt, J ˆ 16.7, 10.7, 6.8, CHˆCH2); 7.17 7.30 (m, Ph). 13C-NMR (CDCl3): 31.6
(t, PhCH2); 33.5(t, CH2CHˆ); 38.3, 38.4 (2t, CH2N, CH2CO); 117.0 (t, CHˆCH2); 126.1 (d, arom. CH); 128.2,
128.4 (2d, 2  2 arom. CH); 135.1 (d, CHˆCH2); 140.7 (s, arom. C); 172.0 (s, CˆO). CI-MS: 221 (18, [M ‡
‡
‡
NH4] ), 126 (100, [M ‡ 1] ).
N-(Pent-4-enyl)-3-phenylpropanamide (4b). According to GP 1, 5-bromopent-1-ene (1b) afforded, after
CC (CH2Cl2/AcOEt 5:1), 4b (1.64 g, 84%). Colorless oil. Rf (CH2Cl2/AcOEt 10 :1) 0.39. 1H-NMR (CDCl3): 1.52
(quint.-like m, CH2CH2N); 1.95 2.04 ( m, CH2CHˆCH2); 2.45( t, J ˆ 7.6, CH2CO); 2.95( t, J ˆ 7.6, PhCH2);
3.17 3.25( m, CH2N); 5.08 5.18 (m, CHˆCH2); 5.40 (br. s, NH); 5.75 (ddt, J ˆ 17.0, 10.3, 6.6, CHˆCH2); 7.16
7.31 (m, Ph). 13C-NMR (CDCl3): 28.6 (t, CH2CH2N); 30.9, 31.7 (2t, PhCH2, CH2CHˆCH2); 38.5, 38.9 (2t, CH2N,
CH2CO); 115.0 (t, CHˆCH2); 126.1 (d, arom. CH); 128.2, 128.4 (2d, 2  2 arom. CH); 137.6 (d, CHˆCH2);
‡
‡
140.8 (s, arom. C); 171.9 (s, CˆO). CI-MS: 235(6, [ M ‡ NH4] ), 218 (100, [M ‡ 1] ).
N-(Hex-5-enyl)-3-phenylpropanamide (4c). According to GP 1, 6-bromohex-1-ene (1c) afforded, after CC
(CH2Cl2/AcOEt 5:1), 4c (1.72 g, 83%). Colorless oil. Rf (CH2Cl2/AcOEt 10 :1) 0.43. 1H-NMR (CDCl3): 1.25
1.49 (m, CH2CH2CH2N); 1.99 2.07 (m, CH2CHˆCH2); 2.45( t, J ˆ 7.7, CH2CO); 2.96 (t, J ˆ 7.7, PhCH2); 3.17
3.24 (m, CH2N); 4.92 5.03 (m, CHˆCH2); 5.29 (br. s, NH); 5.76 (ddt, J ˆ 17.0, 10.3, 6.7, CHˆCH2); 7.16 7.31
(m, Ph). 13C-NMR (CDCl3): 25.9, 28.8 (2t, CH2CH2CH2N); 31.7 (t, PhCH2); 33.2 (t, CH2CHˆCH2); 38.5, 39.2

754
Helvetica Chimica Acta Vol. 86 (2003)
(2t, CH2CO, CH2N); 114.6 (t, CHˆCH2); 126.1 (d, arom. CH); 128.2, 128.4 (2d, 2  2 arom. CH); 138.3 (d,
‡
‡
CHˆCH2); 140.8 (s, arom. C); 171.8 (s, CˆO). CI-MS: 249 (7, [M ‡ NH4] ), 232 (100, [M ‡ 1] ).
N-[(Z)-Hex-4-enyl]-3-phenylpropanamide (7). A mixture of 6 (1.78 g, 10 mmol), (Boc)2NH (2.60 g,
12 mmol), Cs2CO3 (3.26 g, 10 mmol), and DMF (10 ml) was stirred for 12 h at 708, then DMF was removed in
vacuo. The residue was partitioned between CH2Cl2 (50 ml) and H2O (50 ml), the org. phase was separated,
washed with H2O (2 Â 50 ml), dried (MgSO4), and concentrated. The intermediate N,N-bis-Boc derivative was
isolated by CC (hexane/AcOEt 2 :1). Subsequent transformation as described in GP 1 gave, after CC (CH2Cl2/
AcOEt 5:1), 7 (1.85g, 89%). Colorless oil. Rf (CH2Cl2/AcOEt 10 :1) 0.40. 1H-NMR (CDCl3): 1.49 (quint-like m,
CH2CH2N); 1.58 (d-like m, Me); 1.96 2.04 (m, CH2CHˆCH2); 2.45( t, J ˆ 7.7, CH2CO); 2.95( t, J ˆ 7.7, PhCH2);
3.18 3.25( m, CH2N); 5.28 5.52 (m, CHˆCH, NH); 7.16 7.31 (m, Ph). 13C-NMR (CDCl3): 12.62 (q, Me); 24.1
(t, CH2CHˆCH2); 29.2 (t, CH2CH2N); 31.7 (t, PhCH2); 38.5, 39.1 (2t, CH2CO, CH2N); 124.6 (d, MeCHˆ); 126.1
(d, arom. CH); 128.2, 128.4 (2d, 2  2 arom. CH); 129.3 (d, CH2CHˆ); 140.8 (s, arom. C); 171.8 (s, CˆO). CI-
‡
MS: 232 ([M ‡ 1] ).
N-(2-Methylpent-4-enyl)-3-phenylpropanamide (9). A soln. of 8 (4 mmol) and Et3N (0.70 ml, 5mmol) in
Et2O (20 ml) was treated dropwise at 08 with 3-phenylpropanoyl chloride (0.76 ml, 4 mmol). The mixture was
stirred for 30 min at 08, then allowed to reach r.t., washed with H2O (25ml), 10% aq. citric acid (25ml), again
H2O (2 Â 25ml), and dried (MgSO 4). Evaporation of the solvent in vacuo and CC (CH2Cl2/AcOEt 10 :1) gave 9
(0.88 g, 95%). Colorless oil. Rf (CH2Cl2/AcOEt 10 :1) 0.44. 1H-NMR (CDCl3): 0.82 (d, J ˆ 6.7, Me); 1.65( oct.-
like m, MeCH); 1.78 1.89, 1.96 2.06 (2m, CH2CHˆ); 2.48 (t, J ˆ 7.6, CH2CO); 2.96 (t, J ˆ 7.6, PhCH2); 3.00
3.19 (m, CH2N); 4.95 5.03 ( m, CHˆCH2); 5.52 (br. s, NH); 5.65 5.79 (m, CHˆCH2); 7.16 7.31 (m, Ph).
13C-NMR (CDCl3): 17.3 (q, Me); 31.7 (t, CH2Ph); 33.0 (d, MeCH); 38.4, 38.7 (2t, CH2CO, CH2CHˆ); 45.0 (t,
CH2N); 116.2 (t, CHˆCH2); 126.1 (d, arom. CH); 128.2, 128.4 (2d, 2  2 arom. CH); 136.4 (d, CHˆCH2); 140.7
‡
(s, arom. C); 172.0 (s, CˆO). CI-MS: 232 ([M ‡ 1] ).
N-(But-1-enyl)-3-phenylpropanamide (10a). According to GP 2, 4a (2 mmol, 406 mg) afforded, after CC,
10a (227 mg, 56%) as a mixture of (E)- and (Z)-isomers. Colorless solid. Rf (CH2Cl2/AcOEt 10 :1) 0.45. Spectral
1
data of the mixture. H-NMR (CDCl3): (E)-10a: 0.99 (t, J ˆ 7.4, Me); 1.96 2.05( m, MeCH2); 2.49 (t, J ˆ 7.8,
CH2CO); 2.90 2.98 (m, PhCH2); 5.12 (dt, J ˆ 14.2, 6.7, CHˆCHN); 6.73 6.79 (m, CHˆCHN); 7.15 7.31 ( m,
Ph, NH); (Z)-10a: 0.94 (t, J ˆ 7.5, Me); 1.82 1.90 (m, MeCH2); 2.57 (t, J ˆ 7.6, CH2CO); 4.66 (dt, J ˆ 8.8, 7.3,
CHˆCHN); 6.59 6.66 (m, CHˆCHN). Other signals overlapped with those of (E)-10a. 13C-NMR (CDCl3):
(E)-10a: 14.1 (q, Me); 22.8 (t, MeCH2); 31.4 (t, PhCH2); 38.2 (t, CH2CO); 114.9 (d, CHˆCHN); 121.7 (d,
CHˆCHN); 126.2 (d, arom. CH); 128.2, 128.5(2 d, 2  2 arom. CH); 140.6 (s, arom. C); 169.3 (s, CˆO); (Z)-
10a: 13.8 (q, Me); 18.8 (t, MeCH2); 113.1 (d, CHˆCHN); 120.0 (d, CHˆCHN); 126.3 (d, arom. CH); 169.4 (s,
‡
‡
CˆO). Other signals overlapped with those of (E)-10a. CI-MS: 407 (7, [2M ‡ 1] ), 221 (37, [M ‡ NH4] ), 204
‡
(100, [M ‡ 1] ).
N-(Pent-1-enyl)-3-phenylpropanamide (10b). According to GP 2, 4b (2 mmol, 434 mg) afforded, after CC,
10b (140 mg, 32%) as a mixture of (E)- and (Z)-isomers. Colorless solid. Rf (CH2Cl2/AcOEt 10 :1) 0.48. Spectral
data of the mixture: H-NMR (CDCl3): (E)-10b: 0.86 (t, J ˆ 7.4, Me); 1.28 1.41 (m, MeCH2); 1.91 2.01 (m,
1
CH2CHˆ); 2.50 (t, J ˆ 7.8, CH2CO); 2.91 2.98 (m, PhCH2); 5.13 (dt, J ˆ 14.2, 7.2, CHˆCHN); 6.68 6.76 (m,
CHˆCHN); 7.13 7.28 (m, Ph); 7.91 (br. d, NH). (Z)-10b: 0.87 (partially overlapped t, J ˆ 7.3, Me); 1.82 1.91
(m, CH2CHCˆ); 2.58 (t, J ˆ 7.6, CH2CO); 4.67 (dt, J ˆ 8.9, 7.4, CHˆCHN); 6.62 6.68 (m, CHˆCHN); 7.36 (br.
d, NH). Other signals overlapped with those of (E)-10b. 13C-NMR (CDCl3): (E)-10b: 13.4 (q, Me); 22.9 (t,
MeCH2); 31.4 (t, PhCH2); 31.7 (t, CH2CHˆ); 38.1 (t, CH2CO); 113.2 (d, CHˆCHN); 122.5( d, CHˆCHN);
126.1 (d, arom. CH); 128.2, 128.5(2 d, 2  2 arom. CH); 140.7 (s, arom. C); 169.5( s, CˆO); (Z)-10b: 13.8 (q,
Me); 22.4 (t, MeCH2); 27.6 (t, CH2CHˆ); 111.6 (d, CHˆCHN); 120.7 (d, CHˆCHN); 126.3 (d, arom. CH);
‡
‡
169.8 (s, CˆO). Other signals overlapped with those of (E)-10b. CI-MS: 435(6, [2 M ‡ 1] ); 218 (100, [M ‡ 1] ).
N-(Hex-1-enyl)-3-phenylpropanamide (10c). a). According to GP 2, 4c (2 mmol, 462 mg) afforded, after
CC, 10c (106 mg, 23%) as a mixture of (E)- and (Z)-isomers. b). According to GP 2, 7 (2 mmol, 462 mg)
afforded, after CC 10c (108 mg, 23%). Colorless solid. Rf (CH2Cl2/AcOEt 10 :1) 0.50. Spectral data of the
mixture. 1H-NMR (CDCl3): (E)-10c: 0.84 0.90 (m, Me); 1.22 1.36 (m, CH2CH2Me); 1.94 2.01 (m,
CH2CHˆ); 2.47 (t, J ˆ 7.7, CH2CO); 2.90 2.99 (m, PhCH2); 5.10 (dt, J ˆ 14.2, 7.1, CHˆCHN); 6.68 6.76
(m, CHˆCHN); 7.15 7.32 ( m, Ph); 7.53 (br. d, NH). (Z)-10c: 1.82 1.89 (m, CH2CHˆ); 2.57 (m, CH2CO);
4.67 (dt, J ˆ 8.8, 7.4, CHˆCHN); 6.61 6.68 (m, CHˆCHN) 7.36 (br. d, NH). Other signals overlapped with
those of (E)-10c. 13C-NMR (CDCl3): (E)-10c: 13.8 (q, Me); 22.0 (t, MeCH2); 29.2, 31.4, 31.9 (3t, CH2CH2CHˆ,
CH2Ph); 38.1 (t, CH2CO); 113.3 (d, CHˆCHN); 122.3 (d, CHˆCHN); 126.1 (d, arom. CH); 128.2, 128.5(2 d,
2  2 arom. CH); 140.6 (s, arom. C); 169.3 (s, CˆO). (Z)-10c: 22.2 (t, MeCH2); 25.2 (t, CH2CHˆ); 111.6 (d,

Helvetica Chimica Acta Vol. 86 (2003)
755
CHˆCHN); 120.5( d, CHˆCHN); 126.3 (d, arom. CH); 140.4 (s, arom. C); 169.5( s, CˆO). Other signals
‡
overlapped with those of (E)-10c. CI-MS: 232 ([M ‡ 1] ).
N-(2-Methylpent-1-enyl)-3-phenylpropanamide (11). According to GP 2, 9 (2 mmol, 462 mg) afforded,
after CC, 11 (143 mg, 31%) as a mixture of (E)- and (Z)-isomers. Colorless solid. Rf (CH2Cl2/AcOEt 10 :1) 0.51.
1H-NMR (CDCl3): (E)-11 0.85( t, J ˆ 7.2, MeCH2); 1.29 1.42 (m, MeCH2); 1.49 (s, MeCˆ); 1.94 (t, J ˆ 7.4,
CH2Cˆ); 2.56 (m, CH2CO); 2.96 (m, PhCH2); 6.52 (d-like m, CHˆ); 7.16 7.31 (m, Ph, NH). (Z)-11: 1.63 (s,
MeCˆ); 1.84 (t, J ˆ 7.5, CH 2Cˆ). Other signals overlapped with those of (E)-11. 13C-NMR (CDCl3): (E)-11:
13.5, 14.4 (2q, 2 Me); 20.8 (t, MeCH2); 31.5( t, PhCH2); 38.1 (t, CH2CO), 38.6 (t, CH2Cˆ); 116.9 (d, CHˆ);
118.9 (s, Cˆ); 126.2 (d, arom. CH); 128.2, 128.5(2 d, 2  2 arom. CH); 140.6 (s, arom. C); 169.3 (s, CˆO). (Z)-
11: 13.8, 20.0 (2q, 2 Me); 20.2 (t, MeCH2); 32.5( t, CH2Cˆ); 119.4 (s, Cˆ). Other signals overlapped with those
‡
of (E)-11. CI-MS: 232 ([M ‡ 1] ).
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Received October 29, 2002