Photochemistry of N-(2-acylphenyl)-2-methylprop-2-enamides: Competition between photocyclization and long-range hydrogen abstraction

Article abstract of DOI:10.1002/hlca.200490298

The photochemical reactions of various 'N-methacryloyl acylanilides' (= N-(acylphenyl)-2-methylprop-2-enamides) have been investigated. Under irradiation, the acyl-substituted anilides 1a-1c and 1o afforded exclusively the corresponding quinoline-based cy

Full text of DOI:10.1002/hlca.200490298

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Helvetica Chimica Acta ± Vol. 88 (2005)
Photochemistry of N-(2-Acylphenyl)-2-methylprop-2-enamides:
Competition between Photocyclization and Long-Range Hydrogen
Abstraction
a
b
a
c
by Takehiko Nishio* ), Megumi Tabata ), Hiroyuki Koyama ), and Masami Sakamoto )
a) Department of Chemistry, University of Tsukuba, Tsukuba-shi, Ibaraki, 305-8571, Japan
b
)
Graduate School of Environmental Sciences, University of Tsukuba, Tsukuba-shi, Ibaraki, 305-8571, Japan
c) Department of Materials Technology, Faculty of Engineering, Chiba University, Yayoi-cho, Inage-ku, Chiba,
2
63-8522, Japan
The photochemical reactions of various ꢀN-methacryloyl acylanilidesꢁ (ˆ N-(acylphenyl)-2-methylprop-2-
enamides) have been investigated. Under irradiation, the acyl-substituted anilides 1a ± 1c and 1o afforded
exclusively the corresponding quinoline-based cyclization products of type 2 (Table 1). In contrast, irradiation
of the benzoyl (Bz)-substituted anilides 1e ± 1h afforded a mixture of the open-chain amides 4e ± 4h and the
cyclization products 2e ± 2h. Irradiation of the para-acyl-substituted anilides 6a ± 6e and 6h afforded the
corresponding quinoline-based cyclization products of type 5 as the sole products (Table 2). The formation of
the cyclization products 2a ± 2c and 2o can be rationalized in terms of 6p-electron cyclization, followed by
thermal [1,5] acyl migration, and that of compounds 3p, 5a ± 5e, and 5h can be explained by a 6p-electron
cyclization only. The formation of the open-chain amides 4e ± 4h probably follows a mechanism involving a 1,7-
diradical, C and a spirolactam of type D (Scheme). Long-range z-H abstraction by the excited carbonyl O-atom
of the benzoyl group on the aniline ring is expected to proceed via a nine-membered cyclic transition state, as
proposed on the basis of X-ray crystallographic analyses (Fig. 2).
1. Introduction. ± Owing to mesomerism, which confers to amides groups a partial
double-bond character, aromatic enamides exhibit a photochemical behavior similar to
that of conjugated hexatrienes. Indeed, the photo-induced electrocyclic ring closure of
6
p-electron-conjugated enamides has been extensively exploited, and used in the
preparation of a great variety of six-membered lactams [1]. Ninomiya and co-workers
reported that irradiation of a,b-unsaturated acylanilides with ortho-substituents on the
aniline ring leads to smooth photocyclization, followed by thermal [1,5] migration of a
substituent to afford six-membered lactams [2]. For example, irradiation of N-(2-
acetylphenyl)-N-benzyl-2-methylprop-2-enamide (A) afforded 3-acetyl-1-benzyl-3,4-
dihydro-3-methylquinolin-2(1H)-one (B). However, benzophenones-ortho-amides
undergo primarily photolytic deacetylation and dealkylation [3].
ꢂ 2005 Verlag Helvetica Chimica Acta AG, Zürich

Helvetica Chimica Acta ± Vol. 88 (2005)
79
In the course of our studies on the photochemistry of amides and thioamides [4], we
have reported that irradiation of N-(2-halogenoalkanoyl)-substituted anilines (ani-
lides) results in dehydrohalogenation products, which further undergo an electrocyclic
ring closure to afford the corresponding 3,4-dihydroquinolin-2(1H)-ones [5]. We now
report an investigation of the photochemical reactions of various substituted anilides of
type 1 to illustrate the dramatic difference in the photochemical behavior of ortho-
acetyl (Ac)- vs. ortho-benzoyl (Bz)-substituted anilides and related compounds.
2
. Results and Discussion. ± Irradiation of the N-substituted prop-2-enoyl anilides
1a ± 1c in MeCN and under Ar gas with a high-pressure Hg lamp (Pyrex filter, ambient
temperature) led exclusively to the 3,4-dihydroquinolin-2(1H)-ones 2a ± 2c in good
yields (Table 1). The latter are products of the electrocylic ring closure of the parent
6
p-electron-conjugated starting materials 1a ± 1c, the intermediary products of which
undergo a thermal [1,5] acyl migration (see below). Similar results were obtained when
a was irradiated in benzene (Entry 2 in Table 1) instead of MeCN. The photo-
1
cyclization of 1a ± 1c proceeded in the same way as that of N-(a,b-unsaturated)
acylanilides with an electron-withdrawing group in ortho-position of the aniline ring
[
2].
2
The N-unsubstituted anilide 1d (R ˆ H; Table 1) was unreactive upon irradiation
in MeCN, in contrast to the N-methyl-substituted 1o with an ester function on the
benzene ring. The latter compound underwent smooth photocyclization followed by
thermal [1,5] migration of the the COOEt group to afford the lactam 2o in 83% yield.
Irradiation of the corresponding N-unsubstituted analog of 1o, i.e., 1p, gave ethyl
1,2,3,4-tetrahydro-3-methyl-2-oxoquinoline-8-carboxylate (3p) in almost quantitative
yield. In contrast, irradiation of the N-substituted anilides 1e ± 1h, with ortho-Bz
substituents on the aromatic rings, afforded under the same conditions (in MeCN or
MeOH) the quinolinones 2e ± 2h (22 ± 39%), together with the unexpected 2-
hydroxypropanamides 4e ± 4h (26 ± 43%). Neither deacetylation nor dealkylation
products were detected in the reaction mixtures of 1 [3], and no indole or indoline
derivatives arising from d-H abstraction at N-alkyl groups by the excited carbonyl O-
atom were found [6].
Irradiation of the N-methylated anilides 1i and 1j with ortho-Bz groups on their
aromatic rings yielded the cyclized compounds 2i and 2j, respectively, as the sole
products, but in low yields. On the other hand, irradiation of the ortho-Bz anilides 1k
and 1l, lacking a-substituents on the prop-3-enoyl moiety, afforded no products at all.
Thus, a-alkyl substitution is necessary for 6p-electron cyclizations to occur. Moreover,
the N-unsubstituted ortho-Bz anilides 1m and 1n were fully recovered after irradiation.
This is probably due to NH ´´´ CˆO H-bonding, which suppresses enolization (6p-
electron-conjugated enamide).
Next, we investigated anilides with para- rather than ortho-acyl substituents on the
aromatic ring (Table 2). The quinolinone cyclization products 5a ± 5e and 5h were
produced in the photolysis of the anilides 6a ± 6e and 6h, respectively. In these reactions,
the yields of 5a and 5c were especially low. Moreover, no reaction took place with 6f
3
and 6g, lacking a-substituents (R ) on their prop-2-enoyl moieties. These results are,
thus, in accordance with those obtained in the photoreaction of the ortho-acyl anilides
1k ± 1n.

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Helvetica Chimica Acta ± Vol. 88 (2005)
Table 1. Photochemical Reactions ofthe Anilides 1. Unless noted otherwise, all reactions were performed at
ambient temperature. For details, see the Exper. Part.
Entry
Compound
Substituentsa)
Solvent
Isolated Yield [%]
R1
R2
R3
R4
R5
2
4
3p
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
1a
1a
1b
1c
1d
1e
1e
1e
1e
1e
Me
Me
Me
Me
Me
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Me
Me
Et
Bn
H
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
H
H
Me
H
MeCN
Benzene
MeCN
MeCN
MeCN
MeCN
MeCN/H
MeOH
67±
72
72
98
±
35
35
22
41
40
38
39
38
29
11
±
±
±
±
±
±
43
33
32
18
18
30
26
30
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
±
Me
Me
Me
Me
Me
Me
Et
Bn
Me
Me
Me
Me
H
2
O
b
MeCN )
1
1
1
1
1
1
1
1
1
1
2
2
Toluene
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
a
1f )
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
H
H
Me
H
Me
Me
Me
Me
H
Me
H
±
±
±
83
±
Ph
EtO
EtO
H
Me
H
Me
H
H
±
±
99
H
a) X ˆ H, except for 1f (X ˆ Cl; see formulae) and its products 2f and 4f, resp. b) Reaction performed at 608.
The structures of the photoproducts described above were assigned on the basis of
spectral and analytical evidence. In the case of the amide derivative 4e, the assignment
was further confirmed by an X-ray crystal-structure analysis (Fig. 1).
The formation of the 3,4-dihydroquinolin-2(1H)-ones 2 can be rationalized by
means of a mechanism involving a conrotatory electrocyclization, followed by thermal
[
1,5] acyl migration, as proposed previously (Path A in the Scheme) [2]. A reasonable
mechanism for the formation of the unexpected amides 4 is depicted in the
Scheme below (Path B). Allylic-H abstraction by the excited carbonyl O-atom would
result in the 1,7-diradical C. Subsequent ring closure yields the spirolactam D, which
may undergo two kinds of ring opening, either to the aziridinone E or to the enamide F.
Addition of H O (present in trace amounts in the solvent or during workup) would
2
then yield the observed products 4. To remove potential traces of H O in the solvent,
2
the photoreaction of 1e was performed in the presence of molecular sieves. However,
this had little effect, and similar results were obtained as before. Irradiation of 1e in

Helvetica Chimica Acta ± Vol. 88 (2005)
81
Table 2. Photocyclization ofthe para-Acyl-Substituted Anilides 6. All reactions were performed at ambient
temperature (see Exper. Part).
a
Entry
Compound
Substituents
R1
Yield ) [%] of 5
R2
R3
1
2
3
4
5
6
7
8
6a
6b
6c
6d
6e
6f
Me
Me
Ph
Ph
EtO
EtO
EtO
EtO
H
Me
H
Me
H
H
Me
Me
Me
Me
Me
H
19
99
6
90
68
0
6g
6h
Me
Me
H
Me
0
90
a) Yield after chromatographic purification.
Fig. 1. X-Ray crystal structure ofcompound 4e (ORTEP view)

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Helvetica Chimica Acta ± Vol. 88 (2005)
MeCN saturated with H O also gave similar results (see Entry 7 in Table 1). To shed
2
more light on this transformation, the crude reaction mixture was examined by
1
H-NMR analysis immediately after evaporation of the solvent. However, no evidence
for the formation of the anticipated intermediates E or F was found. Attempts to isolate
the MeOH addition products of E or F were unsuccessful as well: irradiation of 1e in
MeOH gave 2e and 4e in 22 and 32% yield, respectively (Entry 8 in Table 1).
Scheme. Proposed Mechanisms for the Photochemical Formation of the Quinolinones 2 (Path A) vs. the Open-
1
2
Chain Amides 4 (Path B) from the ortho-Acyl-Substituted Anilides 1. For R and R , see Table 1.
The observed photochemical behavior of the N-substituted anilides 1 reveals that
the distribution of photoproducts strongly depends on the acyl group on the aromatic
ring ± probably due to conformational and steric effects between the neighboring acyl

Helvetica Chimica Acta ± Vol. 88 (2005)
83
1
and prop-2-enoyl groups. In the room-temperature H-NMR spectrum of 1e, the a-Me
and NMe groups, and the olefinic resonances appeared, in CDCl , at d(H) 1.68 (Me),
3
3
.24 (Me), and at 4.96 and 5.03 (2 Â 1 arom. H), respectively; in CD CN, the same
3
resonances appeared as broad peaks at 1.57, 3.12, 4.84 and 5.00 ppm at room
temperature, while, on increasing the temperature to ca. 608, the peaks became more
and more sharp. This strongly indicates that the conformation of 1e is highly restricted
at room temperature. However, there was no indication of such a conformational
1
restriction in aromatic solvents such as (D )toluene, as observed by means of H-NMR
8
at ambient temperature.
To address these questions more precisely and to determine the contact geometry
between the carbonyl chromophore and nearest H-atoms suitable for abstraction, an X-
ray crystal-structure analysis of 1e was performed (Fig. 2). In the solid state, 1e adopts
a conformation in which z-H abstraction is, indeed, likely to occur. The distance
between the benzoyl (Bz) O-atom (CˆO group) and one of the allylic z-H-atoms of
the methacryloyl moiety, i.e., O(1) ´´´ H(21), was found to be 2.82 Š, which falls within
the typical range of 2.30 ± 3.10 Š required for hydrogen abstraction [7]. In contrast, the
distance O(2) ´´´ H(20), i.e., that between the benzoyl CˆO group and one of the d-H-
atoms of the NMe amido group, is 4.92 Š.
Fig. 2. X-Ray crystal structure ofcompound 1e (ORTEP view)
Irradiation of 1e in MeCN at 608, or in toluene at r.t., resulted in a significant
reduction in the yield of 4e (Entries 9 and 10 in Table 1), 2e becoming the main
product. Intramolecular hydrogen abstraction by excited CˆO groups is very well-
known, attack taking place preferentially at the g-position, under formation of a six-
membered cyclic transition state (Norrish Type II reaction) [7]. g-H Abstraction is

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Helvetica Chimica Acta ± Vol. 88 (2005)
facilitated by favorable stereoelectronic and geometric dispositions, long-range H-atom
transfers, thus, being rare [8]. Many of the reactions involve amino ketone and amino
imides or sulfide imides, and proceed via an electron-transfer process [9]. Our results,
thus, underline that even long-range intramolecular hydrogen abstractions can proceed
efficiently when a favorable conformation is adopted.
Experimental Part
General. Flash chromatography (FC): Wakogel C-300 or Merck 60 silica gel. M.p.: Yanaco MP-J3 micro-
melting-point apparatus; uncorrected. B.p.: Shibata GTO-350-RD glass-tube-oven distillation apparatus. IR
À1
1
13
Spectra: Jasco FT/IR-300 spectrophotometer; in cm . H- and C-NMR Spectra: Jeol JNM-EX-270 (270 MHz)
or Varian Gemini-200 (200 MHz); in CDCl , with MeSi as internal standard; d in ppm, J in Hz.
3
4
General Procedure fo r Photochemical Reactions ofAnilides ofType 1 and 6. A soln. of the anilides 1 or 6
1 mmol) in MeCN (70 ml), unless otherwise noted, was irradiated in a Pyrex tube with a high-pressure Hg lamp
Halos EHP, 500 W; Eikosha) under Ar gas for 3 ± 10 h at r.t. After evaporation, the residue was subjected to FC
(
(
(
SiO
2
; toluene/AcOEt 50 :1 : 4 :1) to afford a mixture of 2 ± 4 (see Table 1).
3
-Acetyl-3,4-dihydro-1,3-dimethylquinolin-2(1H)-one (2a). B.p. 1358/3 Torr. IR (film): 1713, 1666, 1603.
1
H-NMR: 1.42 (s, 3 H); 2.13 (s, 3 H); 2.77 (d, J ˆ 15.4, 1 H); 3.36 (d, J ˆ 15.4, 1 H); 3.42 (s, 3 H); 6.95 ± 7.07 (m ,
1
3
2
2
H); 7.16 ± 7.30 (m , 2 H). C-NMR: 19.8; 25.5; 29.6; 34.7; 54.6; 114,1; 122.8; 123.7; 127.2; 127.6; 138.8; 170.2;
05.5. Anal. calc. for C13 (217.26): C 71.86, H 6.96, N 6.45; found: C 71.55, H 7.01, N 6.69.
-Acetyl-1-ethyl-3,4-dihydro-3-methylquinolin-2(1H)-one (2b). B.p. 1658/3 Torr. IR (film): 1713, 1666, 1603.
H-NMR: 1.20 (t, J ˆ 7.1, 3 H); 1.32 (s, 3 H); 2.02 (s, 3 H); 2.67( d, J ˆ 15.5, 1 H); 3.25 (d, J ˆ 15.5, 1 H); 3.74 ±
.96 (m, 1 H); 3.99 ± 4.11 (m, 1 H); 6.87± 6.94 ( m, 2 H); 7.06 ± 7.22 (m , 2 H). 13C-NMR: 11.8; 19.8; 25.4; 34.8;
7.7; 54.5; 114.0; 122.7; 124.1; 127.3; 128.1; 137.9; 169.7; 205.8. Anal. calc. for C14 (231.28): C 72.70, H 7.41,
N 6.06; found: C 72.49, H 7.56, N 6.04.
H
15NO
2
3
1
3
3
H17NO
2
3
-Acetyl-1-benzyl-3,4-dihydro-3-methylquinolin-2(1H)-one (2c). M.p. 101 ± 1028 (lit. 102 ± 1038 [2b]). IR
1
(
5
3
KBr): 1713, 1680, 1650, 1603. H-NMR: 1.48 (s, 3 H); 2.16 (s, 3 H); 2.85 (d, J ˆ 5.8, 1 H); 3.38 (d, J ˆ 5.8, 1 H);
1
3
.02 (d, J ˆ 16.5, 1 H); 5.31 (d, J ˆ 16.5, 1 H); 6.84 ± 7.30 (m, 9 H). C-NMR (non-aromatic signals): 20.2; 25.6;
5.3; 46.9; 55.2; 170.4; 205.8.
3
-Benzoyl-3,4-dihydro-1,3-dimethylquinolin-2(1H)-one (2e). B.p. 1758/3 Torr. IR (film): 1681, 1601.
1
H-NMR: 1.59 (s, 3 H); 2.7 8 (d , J ˆ 15.4, 1 H); 3.35 (s, 3 H); 3.63 (d, J ˆ 15.4, 1 H); 6.87± 7. 30 ( m, 7 H); 7.74
1
3
(
(
d, J ˆ 8.7, 1 H). C-NMR (non-aromatic signals): 20.7; 29.7; 36.6; 53.5; 170.9; 198.9. Anal. calc. for C18
H17NO
2
279.32): C 77.39, H 6.13, N 5.01; found: C 77.64, H 6.34, N 4.85.
3
-(2-Benzoylphenyl)-2-hydroxy-N,2-dimethylpropanamide (4e). M.p. 120.58. IR (KBr): 3345, 1645.
H-NMR: 1.53 (s, 3 H); 2.75 (d, J ˆ 5.0, 3 H); 2.98 (d, J ˆ 13.5, 1 H); 3.36 (d, J ˆ 13.5, 1 H); 6.35 (br. s, 1 H);
.99 (br. s, 1 H); 7.26 ± 7.52 (m , 6 H); 7.61 ± 7.68 (m , 1 H); 7 .7 8 ± 7 .7 8m (, 2 H). 13C-NMR: 25.7; 27.7; 42.4; 76.4;
1
6
1
6
25.7; 128.5; 130.5; 131.3; 132.3; 133.9; 137.3; 137.6; 176.2; 200.5. Anal. calc. for C18
.44, N 4.71; found: C 72.44, H 6.34, N 4.96.
3
H19NO (297.34): C 72.70, H
3
-Benzoyl-6-chloro-3,4-dihydro-1,3-dimethylquinolin-2(1H)-one (2f). M.p. 148 ± 1508. IR (KBr): 1660,
1
1
7
1
596. H-NMR: 1.61 (s, 3 H); 2.86 (d, J ˆ 15.5, 1 H); 3.33 (s, 1 H); 3.59 (d, J ˆ 15.5, 1 H); 6.81 (d, J ˆ 8.6, 1 H);
.15 ± 7.21 (m , 2 H); 7.32 ± 7.50 (m , 3 H); 7.73 ± 7.78 m( , 2 H). 13C-NMR: 21.4; 30.4; 36.9; 53.7; 115.8; 126.3; 127.4;
2
28.2; 128.5; 132.4; 135.7; 138.0; 170.9; 198.7. Anal. calc. for C18H16ClNO (344.18): C 68.90, H 5.10, N 4.47;
found: C 68.66, H 5.09, N 4.38.
3
-(2-Benzoyl-4-chlorophenyl)-2-hydroxy-N,2-dimethylpropanamide (4f). M.p. 152 ± 1548. IR (KBr): 3412,
1
3
(
343, 1643, 1542. H-NMR: 1.52 (s, 3 H); 2.76 (d, J ˆ 4.8, 3 H); 2.88 (d, J ˆ 14.0, 1 H); 3.33 (d, J ˆ 14.0, 1 H); 7.01
1
3
br. s, 1 H); 7.26 ± 7.83 (m, 8 H). C-NMR: 25.2; 27.3; 41.3; 128.3; 129.4; 130.7; 131.4; 133.1; 134.0; 135.6; 136.2;
1
38.9; 175.6; 198.8. Anal. calc. for C18
3
H18ClNO (331.78): C 65.16, H 5.47, N 4.22; found: C 64.96, H 5.49, N 4.04.
3
-Benzoyl-1-ethyl-3,4-dihydro-3-methylquinolin-2(1H)-one (2g). B.p. 1708/3 Torr. IR (film): 1659, 1601.
1
H-NMR: 1.05 (t, J ˆ 7.2, 3 H); 1.63 (s, 3 H); 2.79 (d, J ˆ 15.6, 1 H); 3.60 (d, J ˆ 15.6, 1 H); 3.68 ± 3.87( m, 1 H);
1
3
4
3
.03 ± 4.15 (m, 1 H); 6.99 ± 7.61 (m, 7 H); 7.70 (d, J ˆ 6.8, 2 H). C-NMR (non-aromatic signals): 11.6; 21.0; 36.9;
‡
‡
‡
7.9; 53.5; 170.4; 199.6. MS: 293 (M ), 188, 105. HR-MS: 293.14090 (M , C19
H
19NO
2
; calc. 293.3597).
3
-(2-Benzoylphenyl)-N-ethyl-2-hydroxy-2-methylpropanamide (4g). B.p. 2008/3 Torr. IR (film): 3345, 1650.
1
H-NMR: 1.04 (t, J ˆ 7.2, 3 H); 1.53 (s, 3 H); 2.98 (d, J ˆ 13.9, 1 H); 3.17± 3.30 ( m, 2 H); 3.37( d, J ˆ 13.9, 2 H);
1
3
6
.38 (br. s, 1 H); 7.20 ± 7.67 (m , 7 H); 7.79 (d, J ˆ 6.9, 2 H). C-NMR: 14.9; 28.0; 34.1; 42.6; 77.7; 128.7; 130.7;

Helvetica Chimica Acta ± Vol. 88 (2005)
85
1
31.3; 131.5; 132.6; 134.1; 137.7; 137.9; 175.7; 200.7. Anal. calc. for
1
C
9
H
21NO
3
(311.37): C 73.29, H 6.80, N 4.50;
found: C 73.67, H 6.60, N 4.65.
3
-Benzoyl-1-benzyl-3,4-dihydro-3-methylquinolin-2(1H)-one (2h). B.p. 2358/3 Torr. IR (film): 1681, 1602.
1
H-NMR: 1.26 (s, 3 H); 2.99 (d, J ˆ 13.5, 1 H); 3.41 (d, J ˆ 13.5, 1 H); 6.39 (br. s, 1 H); 7.11 ± 7.65 (m , 12 H); 7.78
1
3
(
(
d, J ˆ 7.6, 2 H). C-NMR (non-aromatic signals): 21.9; 37.2; 47.4; 54.3; 171.2; 198.8. Anal. calc. for C24
H21NO
2
355.42): C 81.10, H 5.96, N 3.93; found: C 80.96, H 6.10, N 3.87.
3
-(2-Benzoylphenyl)-N-benzyl-2-hydroxy-2-methylpropanamide (4h). M.p. 73.5 ± 75.08. IR (KBr): 3390,
1
1
1
2
681, 1650. H-NMR: 1.57( s, 3 H); 2.99 (d, J ˆ 13.5, 1 H); 3.42 (d, J ˆ 13.5, 1 H); 4.29 ± 4.40 (m, 2 H); 6.39 (br. s,
13
H); 7.11 ± 7.65 (m , 12 H); 7 .7 8d (, J ˆ 7.6, 2 H). C-NMR (non-aromatic signals): 28.0; 42.3; 43.0; 76.3; 175.5;
00.4. Anal. calc. for C24 (355.42): C 77.19, H 6.21, N 3.75; found: C 76.97, H 6.14, N 3.61.
-Benzoyl-3,4-dihydro-1,3,4-trimethylquinolin-2(1H)-one (2i). M.p. 86 ± 878. IR (KBr): 1667, 1601.
H
23NO
3
3
1
H-NMR: 1.55 (d, J ˆ 7.2, 3 H); 1.73 (s , 3 H); 3.08 (q, J ˆ 7.2, 1 H); 3.25 (s, 3 H); 7.05 ± 7.59 (m , 9 H).
1
3
C-NMR (non-aromatic signals): 12.4; 19.9; 30.1; 39.7; 56.7; 171.2; 200.9. Anal. calc. for C19
H
19NO
2
(293.35): C
7
7.79, H 6.53, N 4.77; found: C 77.97, H 6.42, N 4.99.
1
3-Benzoyl-3,4-dihydro-1-methylquinolin-2(1H)-one (2j). B.p. 1808/3 Torr. IR (film): 1681, 1603. H-NMR:
3
7
.06 (dd, J ˆ 6.0, 10.0, 1 H); 3.39 (s, 3 H); 3.38 ± 3.48 (m, 1 H); 4.59 (dd, J ˆ 6.0, 16.0, 1 H); 7.00 ± 7.60 (m, 7 H);
13
.94 ± 7.99 (m , 2 H). C-NMR (non-aromatic signals): 28.1; 29.4; 48.2; 167.4; 185.9. Anal. calc. for C17H15NO
2
(265.30): C 76.96, H 5.70, N 5.23; found: C 76.62, H 5.73, N 5.18.
Ethyl 1,2,3,4-Tetrahydro-1,3-dimethyl-2-oxoquinolin-3-carboxylate (2o). B.p. 1258/3 Torr. IR (film): 1730,
1
1
3
1
680, 1603. H-NMR: 1.03 (t, J ˆ 7.2, 3 H); 1.51 (s, 3 H); 2.85 (d, J ˆ 15.4, 1 H); 3.35 (d, J ˆ 15.4, 1 H); 3.40 (s,
1
3
H); 4.03 ± 4.13 (m, 2 H); 6.95 ± 7.05 (m, 2 H); 7.14 ± 7.31 (m , 2 H). C-NMR: 13.7; 20.4; 30.1; 30.7; 49.6; 61.2;
14.4; 122.9; 123.9; 127.7; 127.9; 139.8; 169.7; 172.1. Anal. calc. for C14H17NO (247.28): C 67.99, H 6.93, N 5.66;
3
found: C 67.68, H 6.90, N 5.89.
Ethyl 1,2,3,4-Tetrahydro-3-methyl-2-oxoquinoline-8-carboxylate (3p). M.p. 102.0 ± 103.58. IR (KBr): 3316,
1
1
3
3
672, 1602. H-NMR: 1.28 (d, J ˆ 6.6, 3 H); 1.40 (t, J ˆ 7.3, 1 H); 2.58 ± 2.81 (m, 2 H); 3.02 (dd, J ˆ 5.6, 15.2, 1 H);
1
3
.67( q, J ˆ 7.3, 2 H); 6.94 ± 7.00 (m, 1 H); 7.28 ± 7.35 (m , 1 H); 7.88 (dd, J ˆ 1.3, 8.3, 1 H). C-NMR: 14.1; 15.1;
3.5; 34.2; 61.2; 113.1; 121.3; 124.5; 129.2; 132.7; 140.0; 167.0; 173.4. Anal. calc. for C13
H
15NO
3
(233.26): C 66.93,
H 6.48, N 6.01; found: C 66.66, H 6.49, N 6.21.
6
-Acetyl-3,4-dihydro-3-methylquinolin-2(1H)-one (5a). M.p. 169 ± 1708. IR (KBr): 3200, 1666, 1605, 1590.
1
H-NMR: 1.32 (d, J ˆ 6.6, 3 H); 2.58 (s, 3 H); 2.63 ± 2.87( m, 2 H); 3.04 ± 3.14 (m, 1 H); 6.95 (d, J ˆ 8.7, 1 H); 7.81
1
3
(
br. s, 2 H); 9.51 (br. s, 1 H). C-NMR: 14.7; 25.8; 32.5; 34.2; 114.4; 122.7; 127.9; 128.0; 131.5; 140.9; 174.5; 196.3.
(203.23): C 70.91, H 6.45, N 6.89; found: C 71.08, H 6.38, N 6.87.
-Acetyl-3,4-dihydro-1,3-dimethylquinolin-2(1H)-one (5b). M.p. 88 ± 898. IR (KBr): 1685, 1667, 1600.
H-NMR: 1.27( d, J ˆ 6.9, 3 H); 2.58 (s, 3 H); 2.63 ± 2.81 (m, 2 H); 2.97± 3.14 ( m, 1 H); 3.39 (s, 3 H); 7 .02 (d , J ˆ
Anal. calc. for C12H13NO
2
6
1
1
3
8
1
7
.3, 1 H); 7.79 (br.s, 1 H); 7.88 (dd, J ˆ 2.0, 8.3, 1 H). C-NMR: 15.6; 26.3; 29.9; 33.1; 35.3; 114.1; 125.9; 127.9;
28.3; 128.4; 131.6; 144.4; 173.2; 196.8. Anal. calc. for C13
2
H15NO (217.26): C 71.86, H 6.96, N 6.45; found: C
1.94, H 7.11, N 6.45.
6
-Benzoyl-3,4-dihydro-3-methylquinolin-2(1H)-one (5c). M.p. 159.5 ± 1618. IR (KBr): 3323, 1684, 1643,
1
1
(
587. H-NMR: 1.33 (d, J ˆ 8.6, 3 H); 2,66 ± 3.12 (m, 2 H); 3.01 ± 3.12 (m, 1 H); 6.93 (d, J ˆ 6.6, 1 H); 7.45 ± 7.91
13
m, 7H); 9.22 (br. s, 1 H). C-NMR: 14.7; 30.3; 32.5; 34.2; 114.2; 122.8; 127.7; 129.2; 129.7; 130.0; 131.6; 137.3;
1
40.6; 174.5; 195.0. Anal. calc. for C17
2
H15NO (265.30): C 76.96, H 5.70, N 5.28; found: C 77.18, H 5.70, N 5.45.
6
-Benzoyl-3,4-dihydro-1,3-dimethylquinolin-2(1H)-one (5d). M.p. 117± 118 8. IR (KBr): 1665, 1645, 1600.
1
H-NMR: 1.28 (d, J ˆ 6.6, 3 H); 2.63 ± 2.81 (m, 2 H); 3.01 (dd, J ˆ 4.3, 14.2, 1 H); 3.41 (s, 3 H); 7 .03 d( , J ˆ 8.3,
1
3
1
1
H); 7.45 ± 7.62 (m, 4 H); 7.7 0 ± 7.7 9m (, 3 H). C-NMR: 15.5; 29.9; 32.9; 35.2; 113.8; 125.4; 128.2; 128.7; 130.3;
31.6; 132.1; 137.8; 144.0; 173.1; 195.4. Anal. calc. for C18 (279.32): C 77.39, H 6.13, N 5.01; found: C 77.56,
H
17NO
2
H 6.09, N 5.27.
Ethyl 1,2,3,4-Tetrahydro-3-methyl-2-oxoquinoline-6-carboxylate (5e). M.p. 211 ± 2138. IR (KBr): 3205,
1
1
4
1
6
713, 1672, 1614. H-NMR: 1.31 (d, J ˆ 6.6, 3 H); 1.39 (t, J ˆ 7.3, 3 H); 2.69 ± 2.83 (m, 2 H); 3.03 ± 3.11 (m, 1 H);
1
3
.36 (q, J ˆ 7.3, 2 H); 6.90 (d, J ˆ 7.9, 1 H); 7.87 (s , 1 H); 7 .88 d( , J ˆ 7.9, 1 H); 9.56 (br. s, 1 H). C-NMR: 15.4;
6.3; 34.1; 35.8; 61.9; 115.9; 124.1; 126.0; 130.5; 130.6; 142.2; 167.2; 176.0. Anal. calc. for C13
3
H15NO (233.26): C
6.93, H 6.48, N 6.01; found: C 66.86, H 6.53, N 6.24.
Ethyl 1,2,3,4-Tetrahydro-1,3-dimethyl-2-oxoquinoline-6-carboxylate (5h). M.p. 78 ± 798. IR (KBr): 1710,
1
1
3
1
639, 1607. H-NMR: 1.27( d, J ˆ 6.6, 3 H); 1.40 (t, J ˆ 7.3, 3 H); 2.60 ± 2.79 (m , 2 H); 2.96 ± 3.04 (m, 1 H); 3.39 (s,
1
3
H); 4.37( q, J ˆ 7.3, 2 H); 6.99 (d, J ˆ 8.6, 1 H); 7.85 (br. s, 1 H); 7 .95 d( d, J ˆ 8.6, 2.0, 1 H). C-NMR: 14.3;
5.6; 29.9; 33.0; 35.3; 60.8; 114.0; 124.6; 125.3; 129.1; 129.3; 133.2; 166.1; 173.2. Anal. calc. for C14H17NO
3
(247.28): C 67.99, H 6.93, N 5.65; found: C 67.89, H 6.90, N 5.66.

8
6
Helvetica Chimica Acta ± Vol. 88 (2005)
1
X-Ray Crystal-Structure Determinations ). Crystals of 4e and 1e were grown from CHCl
3
/hexane. The
intensity data were collected on a Mac Science MXC-18 diffractometer, with graphite-monochromated CuK
a
radiation (l ˆ 1.54178 Š), in the w-2q scan-mode (2q < 69.998). Out of 3176 total reflections, 2630 reflections
with intensities greater than 3s(I) were used in the case of 4e, and 2494 out of 2987reflections were used in the
case of 1e. No absorption corrections were made. The structures were 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.
À3
Crystal Data of 4e: C18
H
19NO
3
; M
r
297.354;Z ˆ 4, D
x
ˆ 1.224 Mg cm ; monoclinic, space group P 2
1
/c; a ˆ
3
1
6.222(3), b ˆ 5.2468(13), c ˆ 22.887(6) Š; a ˆ 90.008, b ˆ 124.05(3)8, g ˆ 90.008; Vˆ 1614.0(7) Š ; R ˆ 0.052,
Rw ˆ 0.046.
À3
Crystal data of 1e: C18
H
17NO
2
, M
r
ˆ 279.339; Z ˆ 2; D
x
ˆ 1.209 Mg cm ; triclinic, space group P 1; a ˆ
3
8
0
.1796(14), b ˆ 8.431(3), c ˆ 12.386(4) Š; a ˆ 93.94(3)8, b ˆ 94.87(2)8, g ˆ 114.84(2)8; Vˆ 767.1(4) Š ; R ˆ
.075, Rw2 ˆ 0.069.
REFERENCES
[
1] G. R. Lenz, Synthesis 1978, 389; I. Ninomiya, T. Naito, Heterocycles 1981, 15, 1433; I. Ninomiya, T. Naito,
Yuki Gousei Kagaku Kyokaishi 1984, 42, 225; A. Campbell, G. R. Lenz, Synthesis 1987, 421; I. Ninomiya, T.
Naito, T. Kiguchi, O. Miyata, Yuki Gousei Kagaku Kyokaishi 1990, 48, 206; P. G. Cleveland, O. L.
Chapman, J. Chem. Soc., Chem. Commun. 1967, 1064; Y. Ogata, K. Takagi, I. Ishino, J. Org. Chem. 1971, 36,
3975; A. Couture, E. Deniau, P. Grandclaudon, S. Lebrin, Tetrahedron Lett. 1996, 37, 7749; T. Bach, B.
Grosch, T. Strassner, E. Herdweck, J. Org. Chem. 2003, 68, 1107.
[2] a) I. Ninomiya T. Kiguchi, T. Naito, J. Chem. Soc., Chem. Commun. 1974, 81; b) I. Ninomiya, T. Kiguchi, S.
Yamauchi, T. Naito, J. Chem. Soc., Perkin Trans. 1 1980, 197.
[
[
3] T. Hasegawa, S. Kosaku, J. Ueno, S. Oguchi, Bull. Chem. Soc. Jpn. 1982, 55, 3569.
4] M. Sakamoto, T. Nishio, in ꢀCRC Handbook of Organic Photochemistry and Photobiologyꢁ, Eds. W.
Horspool, F. Lenci, CRC Press, Boca Raton, 2003, Chapt. 106; M. Sakamoto, T. Nishio, Heterocycles 2003,
59, 399.
[5] T. Nishio, H. Asai, T. Miyazaki, Helv. Chim. Acta 2000, 83, 1475; T. Nishio, K. Iseki, N. Araki, T. Miyazaki,
Helv. Chim. Acta 2005, 88, 35.
[6] H. Aoyama, T. Nishio, Y. Hirabayashi, T. Hasegawa, H. Noda, N. Sugiyama , J. Chem. Soc., Perkin Trans. 1
1975, 298; P. T. Wagner, Q. Cao, Tetrahedron Lett. 1991, 32, 3918; M. Seiler, A. Schumacher, U. Lindemann,
E. Barbosa, B. Giese, Synlett 1999, 1588.
[7] P. J. Wagner, B.-S. Park, in ꢀOrganic Photochemistryꢁ, Ed. A. Padwa, Marcel Dekker, New York, 1991, Vol.
1
1, p. 227; P. J. Wagner, P. Kl a n, in ꢀCRC Handbook of Organic Photochemistry and Photobiologyꢁ, 2nd ed.,
Eds. W. Horspool, F. Lenci, CRC Press, Boca Raton, 2004, Chapt. 52.
[
8] G. L. Descotes, in ꢀCRC Handbook of Organic Photochemistry and Photobiologyꢁ, Eds. W. Horspool, P.-S.
Song, CRC Press, Boca Raton, 1995, p. 501; T. Nishio, Koukagaku [Photochemistry] 2003, 34, 2.
9] T. Hasegawa, Y. Yamazaki, M. Yoshioka, Trends Photochem. Photobiol. 1997, 4, 27; A. Griesbeck H.
Heckroth, H. Schmickler, Tetrahedron Lett. 1999, 40, 3137; P. Wessig, Tetrahedron Lett. 1999, 40, 5987; M.
Oelgemoller, A. G. Griesbeck, in ꢀCRC Handbook of Organic Photochemistry and Photobiologyꢁ, 2nd ed.,
Eds. W. Horspool, F. Lenci, CRC Press, Boca Raton, 2004, Chapt. 84.
[
Received September 6, 2004
1)
The crystallographic data (excluding structure factors) for 4e and 1e have been deposited with the
Cambridge Crystallographic Data Centre (CCDC) as supplementary publication numbers CCDC-239873
and CCDC-239874, resp. Copies of the data can be obtained, free of charge, by application to CCDC, 12
Union Road, Cambridge, CB21EZ, UK (fax: ‡44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk), or via
the internet (http://www.ccdc.cam.ac.uk/products/csd/request).