A novel intramolecular photocyclization of N-(2-bromoalkanoyl) derivatives of 2-acylanilines via 1,8-hydrogen abstraction

Article abstract of DOI:10.1002/hlca.200590095

The photochemical reactions of different N-(2-acylphenyl)-2-bromo-2- methylpropanamides have been investigated. Irradiation of the N-unsubstituted anilides 1a-1c gave the corresponding dehydrobromination, cyclization, and bromo-migration products 2, 3, and 4, respectively (Table 1). Irradiation of the N-alkyl anilides 1e-1g afforded the corresponding deacylation and cyclization products 5 and 6, respectively, whereas irradiation of the N-alkyl anilides 1i-1k, carrying 2-benzoyl groups on the aromatic rings, afforded the unexpected tricyclic lactams 7 (besides 2, 5, and 6). The formation of the cyclization products 6 could be rationalized in terms of an electrocyclic ring closure of the 6π-electron-conjugated enamides 2 produced by dehydrobromination of 1, followed by thermal 1,5-acyl migration (Path B in the Scheme). The formation of the bridged lactams 7 probably follows a mechanism involving the 1,7-diradical 8 generated by ζ-H-abstraction (1.8-H transfer) by an excited acyl O-atom (Path A).

Full text of DOI:10.1002/hlca.200590095

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Helvetica Chimica Acta ± Vol. 88 (2005)
A Novel Intramolecular Photocyclization of N-(2-Bromoalkanoyl)
Derivatives of 2-Acylanilines via 1,8-Hydrogen Abstraction
by Takehiko Nishio*a), Hiroyuki Koyamaa), Daigo Sasakia), and Masami Sakamotob)
a) Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba,
Tsukuba-shi, Ibaraki, 305-8571 Japan
b) Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University, Yayoi-cho,
Inage-ku, Chiba, 263-8522, Japan
The photochemical reactions of different N-(2-acylphenyl)-2-bromo-2-methylpropanamides have been
investigated. Irradiation of the N-unsubstituted anilides 1a ± 1c gave the corresponding dehydrobromination,
cyclization, and bromo-migration products 2, 3, and 4, respectively (Table 1). Irradiation of the N-alkyl anilides
1e ± 1g afforded the corresponding deacylation and cyclization products 5 and 6, respectively, whereas
irradiation of the N-alkyl anilides 1i ± 1k, carrying 2-benzoyl groups on the aromatic rings, afforded the
unexpected tricyclic lactams 7 (besides 2, 5, and 6). The formation of the cyclization products 6 could be
rationalized in terms of an electrocyclic ring closure of the 6p-electron-conjugated enamides 2 produced by
dehydrobromination of 1, followed by thermal 1,5-acyl migration (Path B in the Scheme). The formation of the
bridged lactams 7 probably follows a mechanism involving the 1,7-diradical 8 generated by z-H-abstraction (1,8-
H transfer) by an excited acyl O-atom (Path A).
1. Introduction. ± Intramolecular H-abstraction reactions by an excited CˆO group
have been extensively investigated from synthetic and mechanistic points of view [1 ±
3]. Generally, H-atoms in g-position are abstracted most rapidly through a six-
membered cyclic transition state (1,5-H transfer), as, e.g., in Norrish type II reactions.
This type of H-abstraction is greatly facilitated by favorable stereoelectronic and
geometric conditions. However, carbonyl compounds that lack suitably aligned g-H-
atoms by reason of conformation or substitution can still undergo intramolecular
reactions, e.g., by abstraction of d- or e-H-atoms [2][3]. Abstraction from remote
positions is a very attractive issue in the photochemistry of carbonyl groups [3 ± 9], but
these reactions are generally disfavored for medium- and large-sized cyclic transition
states, both statistically and energetically. Elegant examples of remote H-abstractions
induced by photoexcitation of aromatic carbonyl compounds have been reported by
Breslow [10]. Long-distance Norrish type II abstractions via electron transfer have
been observed in the photochemistry of imides [11], amino ketones [12], and sulfide-
containing glyoxylates [13].
In this paper, we report a novel example of a photochemical z-H-abstraction (1,8-H
transfer) effected by photocemical irradiation of different N-(2-acylphenyl)-2-bromo-
2-methylpropanamides (anilides), and related compounds.
2. Results and Discussion. ± Irradiation of N-(2-acetylphenyl)-2-bromo-2-methyl-
propanamide (1a) in MeCN with a high-pressure Hg lamp (with Pyrex filter) under Ar
atmosphere at ambient temperature afforded the dehydrobromination product 2a, the
quinoline based cyclization product 3a, and the bromo-migration product 4a (Table 1).
ꢀ 2005 Verlag Helvetica Chimica Acta AG, Zürich

Helvetica Chimica Acta ± Vol. 88 (2005)
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Table 1. Photoproducts of Compounds 1a ± 1l. Unless noted otherwise, irradiations were carried out for 1 h with
a Hg lamp.
Isolated yield [%]
Entry
X
H
R1
R2
H
Solvent
2
3
4
5
6
7
1
2a)
3b)
4
1a
1a
1a
1b
1b
1c
1d
1e
1e
1e
1f
1g
1h
1i
1i
1i
1i
1j
1k
1l
Me
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
Benzene
MeOH
MeCN
MeCN
MeCN
MeCN
MeCN
Benzene
MeOH
MeCN
MeCN
MeCN
42
33
19
34
71
48
11
trace
8
trace
trace
trace
6
7
34
18
39
51
trace
7
24
56
±
±
±
±
±
±
±
±
±
±
±
±
±
8
15
19
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
H
Ph
H
5b)
6b)
7b)
8
6
Cl
H
H
Ph
EtO
Me
H
H
Me
trace
±
±
±
±
±
±
±
±
±
±
±
±
±
±
trace
17
17
6
13
3
13
9
trace
14
5
65
38
24
42
9
41
30
10
28
17
30
23
±
±
±
±
±
±
±
32
19
28
30
35
18
±
9
10
11
12
13
14
15c)
16
17
18
19
20
H
H
H
H
Me
Me
EtO
Ph
Et
Bn
Me
Me
16
8
Cl
H
H
Ph
Ph
Ph
Me
Et
Bn
15
14
13
19
18
10
a) Irradiation time: 3 h. b) Irradiation time: 5 h. c) Irradiation time: 0.5 h.
We noticed that, with increasing irradiation time, the yields of both the 3,4-
dihydroquinolin-2(1H)-one 3a and the migration product 4a increased on the expense
of the dehydrobromination product 2a (Entries 1 ± 3 in Table 1). Similar results were
obtained when compounds 1b and 1c were irradiated under the same conditions.
Irradiation of the EtOCO-substituted anilide 1d basically gave only the elimination
product 2d and the cyclization product 3d.
The N-alkylated anilides 1e ± 1g, when irradiated under similar conditions, yielded
the deacylation products 5e ± 5g1) and the 3-acetyl-3,4-dihydroquinolin-2(1H)-ones
6e ± 6g (Entries 8 ± 12). When benzene instead of MeCN was used as solvent, the
dehydrobromination product 2e was obtained in low yield, together with 5e and 6e.
Irradiation of 1h, which carries an ester function on the benzene ring, yielded the
products 2h, 5h, and 6h. In contrast, irradiation of the N-substituted anilides 1i ± 1k
carrying benzoyl substituents on the aniline ring afforded the unexpected tricyclic
lactams 7i ± 7k (besides 2i ± 2k, 5i ± 5k, and 6i ± 6k; Entries 14 ± 19). Irradiation of the N-
1
)
A similar photodeacylation was observed in the photolysis of 2-(N-acylamino)benzophenones [14].

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Helvetica Chimica Acta ± Vol. 88 (2005)
benzyl (Bn) analog 1l led to a complex product mixture, from which 2l and 5l were
isolated by flash chromatography. The structures of the above photoproducts were
assigned on the basis of spectral and analytical evidence. In the case of 7i, the
assignment was further confirmed by X-ray crystal-structure analysis (Figure).
Figure. X-Ray crystal structure of compound 7i (ORTEP view)
The formation of the cyclization products 3 can be rationalized in terms of an
electrocyclic ring closure of 2 produced by CÀBr bond homolysis, followed by
dehydrobromination (Path B in the Scheme) [15e]. Thereby, for R2 ˆ H (compounds
a ± d), cyclization occurred in meta-position to the acyl group due to strong H-bonding
between the aniline NH and the acyl C ˆ O groups. The formation of 6e ± 6k can also be
rationalized by ring closure of 2 (after change in enamide conformation), followed by a
1,5-acyl migration. Analogous electrocyclic reactions have been observed in the
photochemistry of enamides [15][16]. The migration products 4 are probably formed
by an elimination/addition sequence of HBr, compounds 2 acting as ꢁintermediatesꢂ.
The formation of the tricyclic lactams 7 can be rationalized by Path A in the Scheme.
After amide bond isomerization, z-H-abstraction from the 2-methylpropanoyl group
by the excited carbonyl O-atom of the acyl group on the aniline ring may take place via

Helvetica Chimica Acta ± Vol. 88 (2005)
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Helvetica Chimica Acta ± Vol. 88 (2005)
a nine-membered-ring transition state. This would result in formation of the hypo-
thetical 1,7-biradical 8. Subsequent ring closure would then yield the spirocyclic lactam
9, which may undergo two kinds of ring opening, either to the amide 10 or to the
aziridinone 11. Finally, intramolecular ring closure affords 7.
The photochemical behavior of the N-substituted anilides 1e ± 1g and 1i ± 1k reveals
that the product distribution strongly depends on the acyl group on the aromatic ring,
probably due to conformational and steric effects between the neighboring acyl and 2-
1
bromo-2-methylpropanoyl groups. In the room-temperature H-NMR (CDCl3) spec-
trum of 1i, the signals for the two a-Me groups and that of the NMe group at d(H) 1.75
(6 H) and 3.51 (3 H), respectively, were broadened. In CD3CN, these signals were still
broad, but became sharp on raising the temperature to ca. 608. This strongly indicates
that the conformation of 1i is highly restricted at room temperature.
Irradiation of 1i in Me3CN at 08 or at 608 led, in both cases, to the same products 2i,
5i, 6i, and 7i. However, their distribution depended on the temperature (Table 2). The
yield of the H-abstraction product 7i increased at lower temperature, the ratio (2i ‡ 6i)/
7i changing from 1:2 to 1:0.37 upon raising the temperature from 08 to 608.
Table 2. Temperature-Dependent Distribution of Photoproducts in the Reaction of 1i in MeCN Solution
Time
T
Isolated yield [%]
Ratio (2 ‡ 6)/7
2
5
6
7
1 h
1 h
5 h
1 h
258
08
08
7
10
trace
31
9
30
22
28
18
32
49
56
18
1 : 0.86
1 : 1.53
1 : 2.00
1 : 0.37
13
12
22
608
Finally, we investigated analogous anilides with 4-acyl substituents on the benzene
ring. However, irradiation of compounds 12a ± 12f in MeCN gave only the correspond-
ing dehydrobromination and cyclization products 13 and 14, respectively (Table 3).
Indolones were not detected [15e].
Table 3. Yield of Photoproducts upon Irradiation of Substrates 12a ± 12f. Conditions: irradiation for 5 h in
MeCN at 258.
R1
R2
Isolated yield [%]
13
14
12a
12b
12c
12d
12e
12f
Me
Ph
EtO
Me
Ph
H
H
H
Me
Me
Me
19
9
40
21
7
33
43
5
65
65
56
EtO
25

Helvetica Chimica Acta ± Vol. 88 (2005)
1001
Conclusions. ± Hydrogen-abstraction reactions by excited CˆO O-atoms typically
require favorable stereoelectronic and geometric conditions [2], long-range H-
abstractions being rare [3]. Many of the known cases involve amino ketones, amino
imides, or sulfide-containing imides, and proceed via electron-transfer reactions [11 ±
13]. Our results concerning the photochemical reactions of 2-acyl-substituted anilides
with an a-Br substituent on the alkanoyl part demonstrate that long-range H-
abstractions are feasible, given the molecules are present in favorable conformations.
Experimental Part
General. Flash chromatography (FC): Wakogel C-300 silica gel. M.p.: Yanaco MP-J3 micro-melting-point
apparatus; uncorrected. B.p.: Shibata GTO-350-RD glass-tube-oven distillation apparatus. IR Spectra: Jasco
FT/IR-300 spectrophotometer; in cmÀ1. 1H- and 13C-NMR Spectra: Jeol JNM-EX 270 (270/67.5 MHz) or Varian
Gemini-200 (200/50 MHz) spectrometers; in CDCl3, with Me4Si as internal standard; d in ppm, J in Hz.
General Procedure for the Photochemical Reactions of Anilides 1 or 12. A soln. of the anilide (1 mmol) in
MeCN (70 ml), unless noted otherwise, was irradiated in a Pyrex tube with a high-pressure 500-W Hg lamp
(Halos EHP; Eikosha) under Ar atmosphere for 0.5 ± 5 h at r.t. After removal of the solvent, the residue was
subjected to FC (SiO2; toluene/AcOEt 19 :1 ! 4 :1) to afford the photoproducts 2 ± 7, or 13 and 14 (Tables 1 and
3). The structures of the photoproducts 3a, 3b, 3d, 5e ± 5l, 6e ± 6k, and 14a ± 14f were confirmed by comparison of
their spectral data with those given in the literature [16].
1
N-(2-Acetylphenyl)-2-methylprop-2-enamide (2a). B.p. 1558/3 Torr. IR (film): 3225, 1685, 1630. H-NMR:
2.12 (s, 3 H); 2.68 (s, 3 H); 5.54 (br. s, 1 H); 6.03 (s, 1 H); 7.09 ± 7.16 (m, 1 H); 7.54 ± 7.60 (m, 1 H); 7.89 ± 7.94 (m,
1 H); 8.83 ± 8.87 (m, 1 H); 12.21 (br. s, 1 H). 13C-NMR: 19.0; 29.0; 121.1; 122.3; 122.9; 133.2; 135.7; 141.0; 141.6;
167.6; 203.4. Anal. calc. for C12H13NO2: C 70.91, H 6.45, N 6.89; found: C 70.95, H 6.24, N 6.60.
N-(2-Acetylphenyl)-3-bromo-2-methylpropanamide (4a). M.p. 56.5 ± 58.08. IR (KBr): 3204, 1696, 1651.
1H-NMR: 1.42 (d, J ˆ 6.9, 3 H); 2.68 (s, 3 H); 2.87 ± 2.96 (m, 1 H); 2.91 (dd, J ˆ 7.3, 13.2, 1 H); 3.71 (dd, J ˆ 7.3,
9.9, 1 H); 7.51 (dt, J ˆ 1.0, 8.6, 1 H); 7.57 (dt, J ˆ 1.3, 7.3, 1 H); 7.92 (dd, J ˆ 1.7, 7.9, 1 H); 8.78 (dd, J ˆ 1.0, 8.6,
1 H); 11.92 (br. s, 1 H). Anal. calc. for C12H14BrNO2: C 50.72, H 4.97, N 4.93; found: C 50.96, H 4.99, N 4.87.
N-(2-Benzoylphenyl)-2-methylprop-2-enamide (2b). Compounds 2b and 4b could not be completely
separated by FC. Thus, for spectral analysis, 2b was prepared independently by reaction of 2-amino-
benzophenone and methacryloyl chloride in the presence of Et3N. B.p. 2258/3 Torr. IR (film): 3301, 1681, 1632.
1H-NMR: 2.13 (s, 3 H); 5.54 (d, J ˆ 0.7, 1 H); 6.04 (s, 1 H); 7.06 ± 7.13 (m, 1 H); 7.45 ± 7.71 (m, 7 H); 8.74 ± 8.79
(m, 1 H); 11.47 (br. s, 1 H). 13C-NMR: 18.5; 121.3; 121.3; 122.0; 123.0; 128.2; 129.8; 132.3; 133.8; 134.3; 138.7;
140.3; 140.8; 166.8; 199.9. Anal. calc. for C17H15NO2: C 76.96, H 5.70, N 5.28; found: C 76.61, H 5.85, N 5.12.
N-(2-Benzoylphenyl)-3-bromo-2-methylpropanamide (4b). 1H-NMR: 1.42 (d, J ˆ 6.9, 3 H); 2.84 ± 2.95 (m,
1 H); 3.51 (dd, J ˆ 5.6, 9.9, 1 H); 3.71 (dd, J ˆ 7.6, 9.9, 1 H); 7.06 ± 7.14 (m, 1 H); 7.45 ± 7.72 (m, 7 H); 8.75 (d, J ˆ
1.3, 1 H); 11.09 (br. s, 1 H). 13C-NMR (non-aromatic signals only): 17.0; 34.4; 45.4; 176.2; 199.2.
N-(2-Benzoyl-4-chlorophenyl)-2-methylprop-2-enamide (2c). The products 2c and 3c could not be
completely separated by FC. Thus, 2c was prepared independently by reaction of 2-amino-4-chlorobenzophe-
1
none and methacryloyl chloride in the presence of Et3N. M.p. 92 ± 938. IR (KBr): 3277, 1693, 1629. H-NMR:
2.11 (s, 3 H); 5.55 (s, 1 H); 6.02 (s, 1 H); 7.15 ± 7.28 (m, 2 H); 7.39 ± 7.72 (m, 5 H); 8.74 (d, J ˆ 8.9, 1 H); 11.29 (br.
s, 1 H). 13C-NMR (non-aromatic and non-olefinic signals only): 18.8; 167.0; 199.0. Anal. calc. for C17H14ClNO2:
C 68.11, H 4.67, N 4.67; found: 68.00, H 4.43, N 4.35.
8-Benzoyl-6-chloro-3,4-dihydro-3-methylquinolin-2(1H)-one (3c). 1H-NMR: 1.40 (d, J ˆ 6.9, 3 H); 2.89
(dd, J ˆ 7.3, 12.9, 1 H); 3.46 ± 3.53 (m, 1 H); 3.65 ± 3.72 (m, 1 H); 7.15 ± 7.28 (m, 2 H); 7.49 ± 7.72 (m, 4 H); 8.65 (d,
J ˆ 9.5, 1 H); 10.88 (br. s, 1 H). 13C-NMR (non-aromatic signals only): 17.4; 34.6; 45.7; 172.6; 198.8. Anal. calc.
for C17H14ClNO2 (mixture of 2c and 3c): C 68.11, H 4.67, N 4.67; found: 68.32, H 4.62, N 4.92.
Ethyl 2-[(2-Methyl-1-oxoprop-2-enyl)amino]benzoate (2d). M.p. 43.0 ± 44.58. IR (KBr): 3254, 1684.
1H-NMR: 1.42 (t, J ˆ 7.1, 3 H); 2.17 (s, 3 H); 4,39 (q, J ˆ 7.1, 2 H); 5.53 (s, 1 H); 6.00 (s, 1 H); 7.05 ± 7.12 (m,
1 H); 7.52 ± 7.59 (m, 1 H); 8.04 ± 8.09 (m, 1 H); 8.79 ± 8.87 (m, 1 H); 11.62 (br. s, 1 H). 13C-NMR: 14.1; 18.5; 61.3;
115.3; 120.3; 121.0; 122.4; 130.8; 134.5; 130.7; 141.6; 144.7; 166.7; 168.4. Anal. calc. for C13H15NO3: C 66.93, H
6.48, N 5.84; found: C 66.62, H 6.53, N 5.84.
N-(2-Acetylphenyl)-N-methyl-2-methylprop-2-enamide (2e). B.p. 1658/3 Torr. IR (film): 1691, 1649.
1H-NMR: 1.69 (br. s, 3 H); 2.53 (s, 3 H); 3.31 (br. s, 3 H); 4.90 (br. s, 1 H); 4.99 (br. s, 1 H); 7.22 ± 7.30 (m,

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Helvetica Chimica Acta ± Vol. 88 (2005)
1 H); 7.35 ± 7.41 (m, 1 H); 7.49 ± 7.52 (m, 1 H); 7.55 ± 7.69 (m, 1 H). 13C-NMR: 19.3; 28.4; 37.2; 115.3; 119.3; 127,1;
128.8; 129.5; 132.2; 135.1; 139.7; 170.7; 198.3. Anal. calc. for C13H15NO2: C 71.86, H 6.96, N 6.45; found: C 71.61,
H 6.81, N 6.15.
Ethyl 2-[Methyl(2-methyl-1-oxoprop-2-enyl)amino]benzoate (2h). M.p. 86 ± 878. IR (KBr): 1715, 1620.
1H-NMR: 1.38 (t, J ˆ 6.9, 3 H); 1.70 (br. s, 3 H); 3.30 (br. s, 3 H); 4.30 ± 4.39 (m, 2 H); 4.90 (br. s, 1 H); 4.96 (br. s,
1 H); 7.21 ± 7.27 (m, 1 H); 7.34 ± 7.41 (m, 1 H); 7.50 ± 7.57 (m, 1 H); 7.93 ± 7.97 (m, 1 H). 13C-NMR: 14.1; 20.0;
37.6; 61.5; 119.3; 127.6; 128.6; 129.5; 131.8; 133.0; 140.3; 144.5; 165.5; 171.5. Anal. calc. for C14H17NO3: C 67.99, H
6.93, N 5.66; found: C 67.92, H 7.01, N 5.60.
N-(2-Benzoylphenyl)-N-methyl-2-methylprop-2-enamide (2i). M.p. 74 ± 758. IR (KBr): 1664, 1621.
1H-NMR: 1.61 (br. s, 3 H); 3.23 (br. s, 3 H); 4.96 (br. s, 1 H); 5.03 (br. s, 1 H); 7.27 ± 7.62 (m, 7 H); 7.77 ± 7.80
(m, 2 H). Anal. calc. for C18H17NO2: C 77.32, H 6.39, N 5.01; found: C 77.59, H 6.31, N 4.91.
1,2,4,5-Tetrahydro-2,4-dimethyl-1-phenyl-1,4-epoxy-2-benzazepin-3(3H)-one (7i). M.p. 122.5 ± 124.08. I R
(KBr): 1713. 1H-NMR: 1.63 (s, 3 H); 2.65 (s, 3 H); 2.92 (d, J ˆ 17.2, 1 H); 3.12 (d, J ˆ 17.2, 1 H); 7.01 (dd, J ˆ 1.0,
7.6, 1 H); 7.12 ± 7.19 (m, 2 H); 7.25 ± 7.33 (m, 1 H); 7.46 ± 7.57 (m, 5 H). 13C-NMR. 21.1; 28.0; 35.8; 80.2; 95.8;
125.1; 126.1; 128.6; 128.7; 129.6; 130.3; 133.6; 134.5; 176.8. Anal. calc. for C18H17NO2: C 77.39, H 6.13, N 5.01;
found: C 77.40, H 6.27, N 4.95.
N-(2-Benzoyl-4-chlorophenyl)-N-methyl-2-methylprop-2-enamide (2j). B.p. 2108/3 Torr. IR (film): 1667,
1650, 1630. 1H-NMR: 1.70 (br. s, 3 H); 3.23 (br. s, 3 H); 4.92 (br. s, 1 H); 5.07 (s, 1 H); 7.25 ± 7.59 (m, 6 H); 7.77 ±
7.81 (m, 2 H). Anal. calc. for C18H16ClNO2: C 68.90, H 5.10, N 4.47; found: C 69.00, H 5.34, N 4.35.
8-Chloro-1,2,4,5-tetrahydro-2,4-dimethyl-1-phenyl-1,4-epoxy-2-benzazepin-3(3H)-one (7j). M.p. 153 ± 1548.
1
IR: 1720. H-NMR: 1.62 (s, 3 H); 2.68 (s, 3 H); 2.88 (d, J ˆ 17.2, 1 H); 3.06 (d, J ˆ 17.2, 1 H); 7.01 (d, J ˆ 2.0,
1 H); 7.18 ± 7.23 (m, 1 H); 7.25 ± 7.31 (m, 1 H); 7.51 (s, 5 H). 13C-NMR: 21.3; 29.4; 35.6; 80.3; 126.4; 128.8; 129.1;
129.3; 130.2; 132.0; 132.4; 134.2; 174.0. Anal. calc. for C18H16ClNO2: C 68.90, H 5.10, N 4.47; found: C 68.76, H
5.20, N 4.39.
N-(2-Benzoylphenyl)-N-ethyl-2-methylprop-2-enamide (2k). M.p. 106 ± 1078. IR: 1660, 1622. 1H-NMR: 1.42
(t, J ˆ 7.3, 3 H); 1.72 (br. s, 3 H); 3.24 (br. s, 1 H); 4 20 (br. s, 1 H); 7.14 ± 7.57 (m, 7 H); 7.78 (br. d, J ˆ 7.3, 2 H).
Anal. calc. for C19H19NO2: C 77.79, H 6.53, N 4.77; found: C 77.65, H 6.60, N 4.60.
1,2,4,5-Tetrahydro-2-ethyl-4-methyl-1-phenyl-1,4-epoxy-2-benzazepin-3(3H)-one (7k). M.p. 126.5 ± 127.08.
IR (KBr): 1712. 1H-NMR: 0.98 (t, J ˆ 7.3, 3 H); 1.61 (s, 3 H); 2.92 (d, J ˆ17.1, 1 H); 3.10 (d, J ˆ 17.2, 1 H); 3.18
(q, J ˆ 7.3, 2 H); 7.01 ± 7.35 (m, 4 H); 7.46 ± 7.61 (m, 5 H). 13C-NMR: 12.0; 21.0; 35.7; 38.3; 79.8; 95.9; 125.3;
125.6; 128.6; 129.6; 130.1; 133.6; 134.9; 136.4; 177.0. Anal. calc. for C19H19NO2: C 77.79, H 6.53, N 4.77; found: C,
77.61, H 6.52 N 4.97.
N-(2-Benzoylphenyl)-2-methyl-N-phenylprop-2-enamide (2l). M.p. 135 ± 1368. IR (KBr): 1667. 1H-NMR:
1.73 (s, 3 H); 4.13 (br. s, 1 H); 5.03 (br. s, 2 H); 5.56 (br. s, 1 H); 6.95 (d, J ˆ 7.6, 1 H); 7.21 ± 7.60 (m, 12 H); 7.77
(d, J ˆ 7.6, 1 H). Anal. calc. for C24H21NO2: C 81.10. H 5.96, N 3.13; found: C 80.87, H 5.87, N 4.10.
N-(4-Acetylphenyl)-2-methylprop-2-enamide (13a). M.p. 124 ± 1268. IR (KBr): 3326, 1672, 1627. 1H-NMR:
2.07 (s, 3 H); 2.58 (s, 3 H); 5.51 (s, 1 H); 5.85 (s, 1 H); 6.73 (d, J ˆ 8.6, 2 H); 7.94 (d, J ˆ 8.6, 1 H); 8.08 (br. s, 1 H).
13C-NMR: 18.1; 36.1; 118.7; 120.1; 129.1; 132.3; 149.0; 141.6; 166.3; 196.3. Anal. calc. for C12H13NO2: C 70.91, H
6.45, N 6.89; found: C 70.71, H 6.55, N 7.12.
N-(4-Benzoylphenyl)-2-methylprop-2-enamide (13b). M.p. 111.5 ± 1138. IR (KBr): 3323, 1684, 1643.
1H-NMR: 2.06 (s, 3 H); 5,49 (s, 1 H); 5.83 (s, 1 H); 7.11 ± 7.29 (m, 2 H); 7.39 ± 7.62 (m, 3 H); 7.66 ± 7.84 (m,
4 H); 8.09 (br. s, 1 H). 13C-NMR: 18.1; 113.0; 118.5; 120.0; 127.7; 129.3; 131.7; 132.4; 137.2; 140.2; 141.3; 166.3;
195.2 Anal. calc. for C17H15NO2: C 76.96, H 5.70, N 5.28; found: C 76.74, H 5.85, N 5.21.
Ethyl 4-[(2-Methyl-1-oxoprop-2-enyl)amino]benzoate (13c). M.p. 116 ± 1188. IR (KBr): 1719, 1671.
1H-NMR: 1.38 (t, J ˆ 7.3, 3 H); 2.05 (s, 3 H); 4.29 ± 4.39 (m, 2 H); 5.48 (s, 1 H); 5.81 (s, 1 H); 7.67 (d, J ˆ 7.9,
2 H); 8.01 (d, J ˆ 7.79, 2 H). 13C-NMR: 13.9; 18.2; 60.4; 113.3; 118.7; 120.0; 127.9; 130.3; 131.1; 140.2; 141.6;
165.7; 166.3. Anal. calc. for C13H15NO3: C 66.93, H 6.48, N 6.01; found: C 67.01, H 6.62, N 5.93.
N-(4-Acetylphenyl)-N-methyl-2-methylprop-2-enamide (13d). B.p. 1658/3 Torr. IR (film): 1681, 1657, 1630.
1H-NMR: 1.82 (s, 3 H); 2.61 (s, 3 H); 3.39 (s, 3 H); 5.01 (s, 1 H); 5.10 (s, 1 H); 7.24 (d, J ˆ 6.8, 3 H); 7.51 (d, J ˆ
6.8, 2 H). 13C-NMR: 19.5; 26.0; 36.8; 119.6; 125.4; 128.8; 134.4; 139.7; 148.3; 171.2; 196.3. Anal. calc. for
C13H15NO2: C 71.86, H 6.96, N 6.45; found: C 72.00, H 7.17, N 6.41.
N-(4-Benzoylphenyl)-N-methyl-2-methylprop-2-enamide (13e). M.p. 85 ± 868. IR (KBr): 1653. 1H-NMR:
1.84 (s, 3 H); 3.42 (s, 3 H); 5.04 (s, 1 H); 5.13 (s, 1 H); 7.26 (d, J ˆ 8.4, 2 H); 7.45 ± 7.66 (m, 3 H); 7.77 ± 7.85 (m,
4 H). 13C-NMR: 19.6; 36.9; 119.7; 125.2; 127.8; 129.3; 130.6; 132.9; 134.9; 136.7; 139.7; 147.8; 171.3; 195.0. Anal.
calc. for C18H17NO2: C 77.39, H 6.13, N 5.01; found: C 77.50, H 6.24, N 4.90.

Helvetica Chimica Acta ± Vol. 88 (2005)
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Ethyl 4-[Methyl(2-methyl-1-oxoprop-2-enyl)amino]benzoate (13f). B.p 1758/3 Torr. IR (film): 1714, 1658,
1631. 1H-NMR: 1.40 (t, J ˆ 7.3, 3 H); 1.81 (d, J ˆ 1.0, 3 H); 3.38 (s, 3 H); 4.28 (q, J ˆ 7.3, 2 H); 4.99 (br. s, 1 H);
5.00 (br. s, 1 H); 7.21 (d, J ˆ 8.6, 2 H); 8.03 (d, J ˆ 8.6, 2 H). 13C-NMR: 14.2; 20.0; 37.3; 61.0; 120.0; 125.7; 128.5;
130.5; 140.2; 148.6; 165.6; 171.7. Anal. calc. for C14H17NO3: C 67.99, H 6.93, N 5.66; found: C 68.22, H 6.93, N
5.63.
X-Ray Crystal-Structure Analysis. A crystal of 7i was grown from CH2Cl2/hexane. The intensity data were
collected on a Mac Science MXC-18 diffractometer, with graphite-monochromated CuKa radiation (l ˆ
1.54178 Š), in the w À 2q scan mode (2q < 69.998). Out of 3041 total reflections, 2005 reflections with
intensities greater than 3s(I) were used. No absorption corrections were made. The structure was solved by
direct methods with the maXus program. Least-squares refinements were performed, including anisotropic
thermal parameters for non-H-atoms, and isotropic refinement of H-atoms located in difference Fourier
synthesis. Crystal data for 7i: formula, C18H17O2N; Mr 279.339; Vˆ 2960(2) Š; Z ˆ 8; Dx ˆ 1.254 g cmÀ3
;
orthorhombic system, space group Pbca; a ˆ 15.962(4), b ˆ 21.813(8), c ˆ 8.501(2) Š, a ˆ 90.00, b ˆ 90.00, g ˆ
90.008; Vˆ 2960(2) Š3; R ˆ 0.092, Rw2 ˆ 0.089.
The crystallographic data (excluding structure factors) for 7i have been deposited with the Cambridge
Crystallographic Data Centre (CCDC) as supplementary publication number CCDC-264914. Copies of the data
can be obtained, free charge, by application to CCDC, 12 Union Road, Cambridge, CB21EZ, UK (fax: ‡ 44-
1223-336033; e-mail: data_request@ccdc.cam.ac.uk), or via the internet (http://www.ccdc.cam.ac.uk/products/
csd/request).
REFERENCES
[1] P. J. Wagner, Acc. Chem. Res. 1971, 4, 168; P. J. Wagner, Acc. Chem. Res. 1983, 16, 461; P. J. Wagner, Acc.
Chem. Res. 1989, 22, 83; P. Wagner, in ꢁCRC Handbook of Organic Photochemistry and Photobiologyꢂ, Eds.
W. M. Horspool, P.-S. Song, CRC Press, New York, 1995, p. 449.
[2] P. J. Wagner, B.-S. Park, in ꢁOrganic Photochemistryꢂ, Ed. A. Padwa, Marcel Dekker, New York, 1991,
Vol. 11, p. 227; P. Wagner, P. Klan, in ꢁCRC Handbook of Organic Photochemistry and Photobiologyꢂ, 2nd
edn., Eds. W. M. Horspool, F. Lenci, CRC Press, Boca Raton, 2004, p. 52-1.
[3] G. L. Descotes, in ꢁCRC Handbook of Organic Photochemistry and Photobiologyꢂ, Eds. W. M. Horspool,
P.-S. Song, CRC Press, New York, 1995, p. 501; T. Nishio, Koukagaku [Photochemistry] 2003, 34, 2.
[4] H. A. J. Carless, S. Mwesigye-Kibense, J. Chem. Soc., Chem. Commun. 1987, 1673.
[5] G. Adam, A. Preiss, P. D. Hung, Tetrahedron 1987, 43, 5815.
[6] F. Cottet, L. Cottier, G. Descotes, Can. J. Chem. 1990, 68, 1251.
[7] G. A. Kraus, Y. Wu, J. Am. Chem. Soc. 1992, 114, 8705.
[8] G. A. Kraus, W. Zhang, Y. Wu, Chem. Commun. 1996, 1439.
[9] K. Mizuno, S. Konishi, Y. Yoshimi, A. Sugimoto, Chem. Commun. 1998, 1659.
[10] R. Breslow, Acc. Chem. Res. 1980, 13, 170.
[11] Y. Kanaoka, Acc. Chem. Res. 1978, 11, 407; P. H. Mazzocchi, in ꢁOrganic Photochemistryꢂ, Ed. A. Padwa,
Marcel Dekker, New York, 1981, p. 421; J. D. Coyle, in ꢁSynthetic Organic Photochemistryꢂ; Ed. W. M.
Horspool, Plenum Press, New York, 1984, p. 259; H. Mauder, A. G. Griesbeck, in ꢁCRC Handbook of
Organic Photochemistry and Photobiologyꢂ, Eds. W. M. Horspool, P.-S. Song, CRC Press, New York, 1995,
p. 513.
[12] T. Hasegawa, T. Ogawa, K. Miyata, A. Karakizawa, M. Komiyama, K. Nishizawa, M. Yoshioka, J. Chem.
Soc., Perkin Trans. 1 1990, 901; T. Hasegawa, Y. Yamazaki, M. Yoshioka, Trends Photochem. Photobiol.
1997, 4, 27.
[13] S. Hu, D. C. Neckers, Tetrahedron 1997, 53, 7165; S. Hu, D. C. Neckers, J. Org. Chem. 1997, 62, 7827.
[14] T. Hasegawa, S. Kosaku, J. Ueno, S. Oguchi, Bull. Chem. Soc. Jpn. 1982, 55, 3659.
[15] a) Y. Ogata, K. Takagi, I. Isibe, J. Org. Chem. 1971, 36, 3945; b) G. R. Lenz, Synthesis 1978, 489; c) I.
Ninomiya, T. Naito, Heterocycles 1981, 15, 1433; d) I. Ninomiya, T. Naito, Yuki Gosei Kagaku Kyokaishi
1989, 47, 916, and refs. cit. therein; e) T. Nishio, H. Asai, T. Miyazaki, Helv. Chim. Acta 2000, 83, 1475.
[16] T. Nishio, M. Tabata, H. Koyama, M. Sakamoto, Helv. Chim. Acta 2005, 88, 78.
Received March 8, 2005